(19)
(11)EP 2 593 463 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
06.05.2020 Bulletin 2020/19

(21)Application number: 11807418.6

(22)Date of filing:  12.07.2011
(51)Int. Cl.: 
A61K 9/14  (2006.01)
A61K 9/48  (2006.01)
A61K 31/437  (2006.01)
A61K 9/16  (2006.01)
A61K 9/10  (2006.01)
C07D 498/22  (2006.01)
(86)International application number:
PCT/US2011/043769
(87)International publication number:
WO 2012/009388 (19.01.2012 Gazette  2012/03)

(54)

FORMULATIONS OF RIFAXIMIN AND USES THEREOF

FORMULIERUNGEN VON RIFAXIMIN UND ANWENDUNGEN DAVON

FORMULATIONS DE RIFAXIMINE ET UTILISATIONS CORRESPONDANTES


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME

(30)Priority: 02.12.2010 US 419056 P
12.07.2010 US 363609 P

(43)Date of publication of application:
22.05.2013 Bulletin 2013/21

(73)Proprietor: Salix Pharmaceuticals, Inc.
Bridgewater, NJ 08807 (US)

(72)Inventors:
  • SELBO, Jon
    West Lafayette IN 47906 (US)
  • TENG, Jing
    West Lafayette, IN 47906 (US)
  • KABIR, Mohammed, A.
    Cary NC 27519 (US)
  • GOLDEN, Pam
    Durham NC 27713 (US)

(74)Representative: Adam, Holger 
Kraus & Weisert Patentanwälte PartGmbB Thomas-Wimmer-Ring 15
80539 München
80539 München (DE)


(56)References cited: : 
EP-A1- 2 011 486
WO-A1-2011/061748
WO-A2-2011/051971
US-A1- 2009 011 020
WO-A1-2010/067072
WO-A2-2009/108730
US-A1- 2008 095 754
US-A1- 2010 174 064
  
  • VASCONCELOS ET AL: "Solid dispersions as strategy to improve oral bioavailability of poor water soluble drugs", DRUG DISCOVERY TODAY, ELSEVIER, RAHWAY, NJ, US, vol. 12, no. 23-24, 30 October 2007 (2007-10-30), pages 1068-1075, XP022370275, ISSN: 1359-6446
  • LEUNER C ET AL: "Improving drug solubility for oral delivery using solid dispersions", EUROPEAN JOURNAL OF PHARMACEUTICS AND BIOPHARMACEUTICS, ELSEVIER SCIENCE PUBLISHERS B.V., AMSTERDAM, NL, vol. 50, no. 1, 3 July 2000 (2000-07-03), pages 47-60, XP004257179, ISSN: 0939-6411, DOI: 10.1016/S0939-6411(00)00076-X
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

BACKGROUND



[0001] Rifaximin (INN; see The Merck Index, XIII Ed., 8304) is an antibiotic belonging to the rifamycin class of antibiotics, e.g., a pyrido-imidazo rifamycin. Rifaximin exerts its broad antibacterial activity, for example, in the gastrointestinal tract against localized gastrointestinal bacteria that cause infectious diarrhea, irritable bowel syndrome, small intestinal bacterial overgrowth, Crohn's disease, and pancreatic insufficiency among other diseases. It has been reported that rifaximin is characterized by a negligible systemic absorption, due to its chemical and physical characteristics (Descombe J.J. et al. Pharmacokinetic study of rifaximin after oral administration in healthy volunteers. Int J Clin Pharmacol Res, 14 (2), 51-56, (1994)).

[0002] Rifaximin is described in Italian Patent IT 1154655 and EP 0161534. EP 0161534 discloses a process for rifaximin production using rifamycin O as the starting material (The Merck Index, XIII Ed., 8301). U.S. Patent No. 7,045,620 B1 and PCT Publication WO 2006/094662 A1 disclose polymorphic forms of rifaximin. There is a need in the art for formulations of rifaximin to better treat gastrointestinal and other diseases.

SUMMARY



[0003] Provided herein are solid dispersion forms of rifaximin with a variety of polymers and polymer concentrations.

[0004] In one aspect, provided herein are forms solid dispersion of rifaximin.
In particular, provided is a solid dispersion form of rifaximin comprising rifaximin and a polymer selected from: hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grade HG and grade MG, wherein the rifaximin:polymer weight ratio ranges from 10:90 to 90:10.

[0005] In one embodiment, the form solid dispersion of rifaximin is characterized by an XRPD substantially similar to one or more of the XRPDs of Figures 12, 17, and 31.

[0006] In one embodiment, the form solid dispersion of rifaximin is characterized by a Thermogram substantially similar to Figures 13-16, 18-21, 28, 29 and 32.

[0007] In one embodiment, the form has the appearance of a single glass transition temperature (Tg).

[0008] In one embodiment, a Tg of a form increases with an increased rifaximin concentration

[0009] In one embodiment, a form stressed at 70°C/ 75%RH for 1 week, solids are still x-ray amorphous according to XRPD.

[0010] In one embodiment, a form stressed at 70°C/ 75%RH for 3 weeks, solids are still x-ray amorphous according to XRPD.

[0011] In one embodiment, a form stressed at 70°C/ 75%RH for 6 weeks, solids are still x-ray amorphous according to XRPD.

[0012] In one embodiment, a form stressed at 70°C/ 75%RH for 12 weeks, solids are still x-ray amorphous according to XRPD.

[0013] In one aspect, provided herein are microgranules comprising one or more of the solid dispersion forms of rifaximin described herein.

[0014] In one embodiment, the microgranules further comprise a polymer.

[0015] In one embodiment, the polymer comprises one or more of polyvinylpyrrolidone (PVP) grade K-90, hydroxypropyl methylcellulose phthalate (HPMC-P) grade 55, hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grades HG and MG, or a polymethacrylate (Eudragit® L100-55).

[0016] In specific embodiments, the microgranules comprises 25-75% polymer, 40-60% polymer, or 40-50% polymer. In an exemplary embodiment, the microgranules comprises 42-44% polymer.

[0017] In one embodiment, the microgranules comprise equal amounts of rifaximin and polymer.

[0018] In another embodiment, the microgranules further comprising an intragranular release controlling agent. In exemplary embodiments, the intragranular release controlling agent comprises a pharmaceutically acceptable excepient, disintegrant, crosprovidone, sodium starch glycolate, corn starch, microcrystalline cellulose, cellulosic derivatives, sodium bicarbonate, and sodium alginate.

[0019] In one embodiment, the intragranular release controlling agent comprises between about 2 wt% to about 40 wt% of the microgranule, about 5 wt% to about 20 wt% of the microgranule, or about 10 wt% of the microgranule.

[0020] In another embodiment, the intragranular release controlling agent comprises a pharmaceutically acceptable disintegrant, e.g., one selected from the group consisting of crosprovidone, sodium starch glycolate, corn starch, microcrystalline cellulose, cellulosic derivatives, sodium bicarbonate, and sodium alginate.

[0021] In another embodiment, the microgranules further comprise a wetting agent or surfactant, e.g., a non-ionic surfactant.

[0022] In one embodiment, the non-ionic surfactant comprises between about 2 wt% to about 10 wt% of the microgranule, between about 4 wt% to about 8 wt% of the microgranule, or about 5.0 wt% of the microgranule .

[0023] In one embodiment, the non-ionic surfactant comprises a poloxamer, e.g., poloxamer 407 also known as Pluronic F-127.

[0024] In another embodiment, the microgranules further comprise an antioxidant.

[0025] In exemplary embodiments, the antioxidant is butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) or propyl gallate (PG).

[0026] In another embodiment, the antioxidant comprises between about 0.1 wt% to about 3 wt% of the microgranule or between about 0.5 wt% to about 1 wt% of the microgranule.

[0027] Further, the present invention provides a pharmaceutical composition comprising the solid dispersion form of rifaximin as described herein and at least one pharmaceutically acceptable excipient.

[0028] In another aspect, provided herein are pharmaceutical compositions comprising the microgranules described herein.

[0029] In one embodiment, the pharmaceutical compositions further comprise one or more pharmaceutically acceptable excepients.

[0030] In one embodiment, the pharmaceutical compositions are tablets or capsules.

[0031] In one embodiment, the pharmaceutical compositions comprises a disintegrant.

[0032] In one embodiment, the polymer comprises one or more of polyvinylpyrrolidone (PVP) grade K-90, hydroxypropyl methylcellulose phthalate (HPMC-P) grade 55, hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grades HG and MG, or a polymethacrylate (Eudragit® L100-55)), with the provision that solid dispersion forms of rifaximin comprise rifaximin and a polymer selected from hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grade HG and grade MG..

[0033] In one aspect, provided herein are pharmaceutical solid dispersion formulations comprising: rifaximin, HPMC-AS, at a rifaximin to polymer ratio of 50:50, a non-ionic, surfactant polyol and a intragranular release controlling agent.

[0034] In one embodiment, the intragranular release controlling agent comprises about 10 wt% of the formulation.

[0035] In one aspect, provided herein are processes for producing a solid dispersion of rifaximin comprising: making a slurry of methanol, rifaximin, a polymer and a surfactant; spray drying the slurry; and blending the spray dried slurry with a intragranular release controlling agent.

[0036] In one aspect, provided herein are processes for producing a solid dispersion of rifaximin comprising: making a slurry of methanol, rifaximin, HPMC-AS MG and Pluronic F-127; spray drying the slurry; and blending the spray dried slurry with a intragranular release controlling agent.

[0037] In one embodiment, the intragranular release controlling agent comprises croscarmellose sodium.

[0038] A process for producing form solid dispersion of rifaximin comprising one or more of the methods listed in Tables 1-5.

[0039] In one embodiment, pharmaceutical compositions comprising SD rifaximin, a polymer, a surfactant, and a release controlling agent are provided. In one embodiment, provided are pharmaceutical compositions comprising SD rifaximin, HPMC-AS, pluronic F127, and croscarmellose Na (CS). In one embodiment, the pharmaceutical compositions are tablets or pills.

[0040] In additional embodiments, the pharmaceutical compositions further comprise fillers, glidants or lubricants.

[0041] In specific embodiments, the pharmaceutical compositions comprise the ratios of components set forth in Table 37.

[0042] Other embodiment and aspects are disclosed infra.

BRIEF DESCRIPTION OF THE DRAWINGS



[0043] 

Figure 1. Chemical structure of Rifaximin.

Figure 2. (for reference) Overlay of XRPD patterns for Rifaximin/PVP K-90 dispersions obtained from methanol by spray drying.

Figure 3. (for reference) mDSC thermogram for 25:75 (w/w) Rifaximin/PVP K-90 dispersion obtained from methanol by spray drying.

Figure 4. (for reference) mDSC thermogram for 50:50 (w/w) Rifaximin/PVP K-90 dispersion obtained from methanol by spray drying .

Figure 5. (for reference) mDSC thermogram for 75:25 (w/w) Rifaximin/PVP K-90 dispersion obtained from methanol by spray drying .

Figure 6. (for reference) Overlay of mDSC thermogram for Rifaximin/PVP K-90 dispersions obtained from methanol by spray drying.

Figure 7. (for reference) Overlay of XRPD patterns for Rifaximin/HPMC-P dispersions obtained from methanol by spray drying.

Figure 8. (for reference) mDSC thermogram for 25:75 (w/w) Rifaximin/HPMC-P dispersion obtained from methanol by spray drying.

Figure 9. (for reference) mDSC thermogram for 50:50 (w/w) Rifaximin/HPMC-P dispersion obtained from methanol by spray drying.

Figure 10. (for reference) mDSC thermogram for 75:25 (w/w) Rifaximin/HPMC-P dispersion obtained from methanol by spray drying .

Figure 11. (for reference) Overlay of mDSC thermogram for Rifaximin/HPMC-P dispersions obtained from methanol by spray drying.

Figure 12. Overlay of XRPD patterns for Rifaximin/HPMC-AS HG dispersions obtained from methanol by spray drying.

Figure 13. mDSC thermogram for 25:75 (w/w) Rifaximin/HPMC-AS HG dispersion obtained from methanol by spray drying .

Figure 14. mDSC thermogram for 50:50 (w/w) Rifaximin/HPMC-AS HG dispersion obtained from methanol by spray drying.

Figure 15. mDSC thermogram for 75:25 (w/w) Rifaximin/HPMC-AS HG dispersion obtained from methanol by spray drying.

Figure 16. Overlay of mDSC thermogram for Rifaximin/HPMC-AS HG dispersions obtained from methanol by spray drying.

Figure 17. Overlay of XRPD patterns for Rifaximin/HPMC-AS MG dispersions obtained from methanol by spray drying.

Figure 18. mDSC thermogram for 25:75 (w/w) Rifaximin/HPMC-AS MG dispersion obtained from methanol by spray drying.

Figure 19. mDSC thermogram for 50:50 (w/w) Rifaximin/HPMC-AS MG dispersion obtained from methanol by spray drying.

Figure 20. mDSC thermogram for 75:25 (w/w) Rifaximin/HPMC-AS MG dispersion obtained from methanol by spray drying.

Figure 21. Overlay of mDSC thermogram for Rifaximin/HPMC-AS MG dispersions obtained from methanol by spray drying.

Figure 22. (for reference) Overlay of XRPD patterns for Rifaximin/Eudragit L100-55 dispersions obtained from methanol by spray drying.

Figure 23. (for reference) mDSC thermogram for 25:75 (w/w) Rifaximin/Eudragit LI00-55 dispersion obtained from methanol by spray drying.

Figure 24. (for reference) mDSC thermogram for 50:50 (w/w) Rifaximin/Eudragit LI00-55 dispersion obtained from methanol by spray drying.

Figure 25. (for reference) mDSC thermogram for 75:25 (w/w) Rifaximin/Eudragit L100-55 dispersion obtained from methanol by spray drying.

Figure 26. (for reference) Overlay of mDSC thermogram for Rifaximin/Eudragit L100-55 dispersions obtained from methanol by spray drying.

Figure 27. (for reference) mDSC thergram for 25:75 (w/w) Rifaximin/HPMC-P dispersion stressed at 40 °C/75% RH for 7 d.

Figure 28. mDSC thergram for 75:25 (w/w) Rifaximin/HPMC-AS HG dispersion stressed at 40 °C/75% RH for 7 d.

Figure 29. mDSC thergram for 75:25 (w/w) Rifaximin/HPMC-AS MG dispersion stressed at 40 °C/75% RH for 7 d.

Figure 30. (for reference) mDSC thergram for 25:75 (w/w) Rifaximin/Eudragit L100-55 dispersion stressed at 40 °C/75% RH for 7 d.

Figure 31. XRPD pattern for 50:50 (w/w) Rifaximin/HPMC-AS MG dispersion.

Figure 32. Modulate DSC thermograms for 50:50 (w/w) Rifaximin/HPMC-AS MG dispersion.

Figure 33. TG-IR analysis for 50:50 (w/w) Rifaximin/HPMC-AS MG dispersion- TGA data.

Figure 34. TG-IR analysis for 50:50 (w/w) Rifaximin/HPMC-AS MG dispersion- Gram-Schmidt plot and waterfall plot.

Figure 35. TG-IR analysis for 50:50 (w/w) Rifaximin/HPMC-AS MG dispersion.

Figure 36. (for reference) XRPD pattern for 25:75 (w/w) Rifaximin/HPMC-P dispersion.

Figure 37. (for reference) Modulate DSC thermograms for 25:75 (w/w) Rifaximin/HPMC-P dispersion.

Figure 38. (for reference) TG-IR analysis for 25:75 (w/w) Rifaximin/HPMC-P dispersion - TGA data.

Figure 39. (for reference) TG-IR analysis for 25:75 (w/w) Rifaximin/HPMC-P dispersion - Gram-Schmidt plot and waterfall plot.

Figure 40. (for reference) TG-IR analysis for 25:75 (w/w) Rifaximin/HPMC-P dispersion.

Figure 41. Overlay of pre-processed XRPD patterns in multivariate mixture analysis.

Figure 42. Estimated Concentrations of Rifaximin (blue) and HPMC-AS MG (red) using Unscrambler MCR analysis.

Figure 43. Estimated XRPD patterns of Rifaximin (blue) and HPMC-AS MG (red) using Unscrambler MCR analysis.

Figure 44. Overlay of estimated XRPD pattern of pure rifaximin using MCR and measured XRPD pattern of 100% rifaximin.

Figure 45. Overlay of estimated XRPD pattern of pure HPMC-AS MG using MCR and measured XRPD pattern of 100% HPMC-AS MG.

Figure 46. An exemplary XRPD pattern for combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 47. A modulate DSC thermogram for combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 48. A TG-IR analysis for combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion - TGA thermogram.

Figure 49. An exemplary TG-IR analysis for combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 50. An exemplary overlay of IR spectra for X-ray amorphous Rifaximin and combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 51. An exemplary overlay of Ramam spectra for X-ray amorphous Rifaximin and combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 52. A particle size analysis report for combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 53. An exemplary dynamic vapor sorption (DVS) analysis for combined solids of Rifaximin/HPMC-AS MG/Pluronic ternary dispersion.

Figure 54. An exemplary overlay of XRPD patterns for Rifaximin/HPMC-AS MG/Pluronic ternary dispersion post-DVS solids and solids as-prepared.

Figure 55. An exemplary overlay of XRPD patterns for Rifaximin ternary dispersion post-stressed samples and as-prepared sample.

Figure 56. An exemplary mDSC thermgram for Rifaximin ternary dispersion after 70 °C/75% RH 1week.

Figure 57. An exemplary mDSC thermgram for Rifaximin ternary dispersion after 70 °C/75% RH 3weeks.

Figure 58. An exemplary mDSC thermgram for Rifaximin ternary dispersion after 40 °C/75% RH 6 weeks.

Figure 59. An exemplary mDSC thermgram for Rifaximin ternary dispersion after 40 °C/75% RH 12 weeks.

Figure 60. Pharmacokinetic data of solid dispersion in dogs.

Figure 61. Rifaximin SD capsules dissolution; acid phase: 0.1 N HCl with variable exposure time. Buffer phase: pH 6.8 with 0.45% SDS.

Figure 62. Rifaximin SD capsules dissolution; acid phase: 2 hours; buffer phase: pH 6.8.

Figure 63. Rifaximin capsule dissolution; phosphate buffer pH 6.8 with 0.45% SDS.

Figure 64. Rifaximin spray dried dispersion (SDD) capsule dissolution. (a) acid phase 2 hours, buffer phase: P. Buffer, pH. 7.4. (b) acid phase: 0.1N HCl with various exposure times, buffer phase: P. buffer, pH 7.4 with 0.45% SDS.

Figure 65. Rifamixin SDD with 10%CS formulation. (a) kinetic solubility Rifamixin SD granules. 10% wt% CS sodium FaSSIF, 10% wt% CS sodium FeSSIF. (b) dissolution profiles SDD tablet 10% CS. 0.2% SLS, pH4.5; 0.2% SLS, pH5.5; 0.2% SLS, pH 7.4; FaSSIF.

Figure 66. Rifaximin SDD with 10% CS formulation. Rifaxamin SDD capsules dissolution: (a) acid phase 2 hours, buffer phase: P. Buffer, pH. 7.4. With 0.45% SDS; without SDS. (b) acid phase: 0.1N HCl with variable exposure times, buffer phase: P. buffer, pH 7.4 with 0.45% SDS.

Figure 67. Effects of media pH on dissolution. (a) Rifaxamin SDD tablet dissolution. Acid phase: 2 hours, pH 2.0, (b) Dissolution profiles 0.2% SDS at pH 4.5, SDD tablet dissolution at various levels of CS: 0%, 2.5%,5%, and 10% CS.

Figure 68. Effects of media pH on dissolution. (a) Rifaxamin SDD tablet dissolution at various levels of CS: 0%, 2.5%,5%, and 10% CS, 0.2% SDS at pH 5.5. (b) Dissolution profiles SDD tablet dissolution at various levels of CS: 0%, 2.5%,5%, and 10% CS, 0.2% SDS at pH 7.4.

Figure 69. Effects of media pH on dissolution. (a) Rifaxamin SDD tablet dissolution 2.5% CS, 0.2% SLS, pH4.5, 0.2% SLS, pH 5.5, 0.2% SLS, pH 7.4. (b) Rifaxamin SDD tablet dissolution 0% CS, 0.2% SLS, pH4.5, 0.2% SLS, pH 5.5, 0.2% SLS, pH 7.4.

Figure 70. Effects of media pH on dissolution. (a) Rifaxamin SDD tablet dissolution 10% CS, 0.2% SLS, pH4.5, 0.2% SLS, pH 5.5, 0.2% SLS, pH 7.4. (b) Rifaxamin SDD tablet dissolution 5% CS, 0.2% SLS, pH4.5, 0.2% SLS, pH 5.5, 0.2% SLS, pH 7.4.

Figure 71. CS release mechanism. (a) Kinetic solubility in FaSSIF media, pH 6.5, (b) slope vs. time point.

Figure 72 depicts an overlay of XRPD patterns of rifaximin quaternary samples spray dried from methanol. The top is a rifaximin quaternary sample containing 0.063 wt% BHA. The second is rifaximin quaternary sample containing 0.063 wt% BHT. The third: is rifaximin quaternary sample containing 0.094 wt% PG, and the bottom is a spray dried rifaximin ternary dispersion.

Figure 73 depicts an mDSC thermogram of rifaximin quaternary sample containing 0.063 wt% BHA

Figure 74 depicts an mDSC thermogram of rifaximin quaternary sample containing 0.063 wt% BHT.

Figure 75 depicts a mDSC thermogram of rifaximin quaternary sample containing 0.094 wt% PG.

Figure 76 depicts an XRPD pattern comparison of rifaximin solid dispersion powder 42.48% w/w with roller compacted material of rifaximin blend.Top: Rifaximin Solid Dispersion Powder 42.48% w/w; Bottom: roller compacted rifaximin blend.

Figure 77 depicts the pharmacokinetics of rifaximin following administration of varying forms and formulations following a single oral dose of 2200 mg in dogs.

Figure 78 depicts Rifaximin SDD in dogs.

Figure 79 depicts the quotient study design.

Figure 80 summarizes the dose escalation/regional absorption study, part A dose escalation/dose selection.

Figure 81 depicts representative subject data from a dose escalation study.

Figure 82 depicts representative subject data from a dose escalation study.

Figure 83 depicts mean dose escalation data, on a linear scale.

Figure 84 depicts mean dose escalation data, on a log scale.

Figure 85 depicts a summary of Rifaximin SDD dose escalation studies.

Figure 86 is a Table of dose/ dosage form comparison.

Figure 87 is a Table of dose/ dosage form comparison. This table compares SDD at increasing doses to the current crystalline formulation in terms of systemic PK.


DETAILED DESCRIPTION



[0044] Embodiments described herein relate to the discovery of new solid dispersion forms of rifaximin with a variety of polymers and polymer concentrations. In one embodiment the use of one or more of new solid dispersion forms of the antibiotic known as Rifaximin (INN), in the manufacture of medicinal preparations for the oral or topical route is contemplated. For example, the solid dispersion forms of rifaximin are used to create pharmaceutical compositions, e.g.,. tablets or capsules, or microgranules comprising solid dispersion forms of rifaximin. Exemplary methods for producing rifaximin microgranules are set forth in the examples. Rifaximin microgranules can be formulated into pharmaceutical compositions as described herein.

[0045] Aspects described herein also relate to administration of such medicinal preparations to a subject in need of treatment with antibiotics. Provided herein are solid dispersion forms of rifaximin with a variety of polymers and polymer concentrations.

[0046] In particular, provided is a solid dispersion form of rifaximin comprising rifaximin and a polymer selected from: hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grade HG and grade MG, wherein the rifaximin:polymer weight ratio ranges from 10:90 to 90:10.

[0047] As used herein, the term "intragranular release controlling agent" include agents that cause a pharmaceutical composition, e.g., a microgranule, to breakdown thereby releasing the active ingredient, e.g., rifaximin. Exemplary intragranular release controlling agent, include disintegrants such as crosprovidone, sodium starch glycolate, corn starch, microcrystalline cellulose, cellulosic derivatives, sodium bicarbonate, and sodium alginate.

[0048] In one embodiment, the intragranular release controlling agent comprises between about 2 wt% to about 40 wt% of the microgranule, about 5 wt% to about 20 wt% of the microgranule, about 8-15 wt% or about 10 wt% of the microgranule.

[0049] In another embodiment, the microgranule comprises a surfactant, e.g., a non-ionic surfactant. In one embodiment, the non-ionic surfactant comprises between about 2 wt% to about 10 wt% of the microgranule, between about 4 wt% to about 8 wt% of the microgranule, about 6 to about 7 wt % of the microgranule, or about 5.0 wt% of the microgranule .

[0050] In another embodiment, the microgranule comprises an antioxidant. In one embodiment, the antioxidant comprises between about 0.1 wt% to about 3 wt% of the microgranule, between 0.3 wt% to about 2 wt% or between about 0.5 wt% to about 1 wt% of the microgranule.

[0051] As used herein, the term "intragranular" refers to the components that reside within the microgranule. As used herein, the term "extragranular" refers to the components of the pharmaceutical composition that are not contained within the microgranule.

[0052] As used herein, the term polymorph is occasionally used as a general term in reference to the forms of rifaximin and includes within the context, salt, hydrate, polymorph co-crystal and amorphous forms of rifaximin. This use depends on context and will be clear to one of skill in the art.

[0053] As used herein, the term "about" when used in reference to x-ray powder diffraction pattern peak positions refers to the inherent variability of the peaks depending on, for example, the calibration of the equipment used, the process used to produce the polymorph, the age of the crystallized material and the like, depending on the instrumentation used. In this case the measure variability of the instrument was about ±0.2 degrees 2-θ. A person skilled in the art, having the benefit of this disclosure, would understand the use of "about" in this context. The term "about" in reference to other defined parameters, e.g., water content, Cmax, tmax, AUC, intrinsic dissolution rates, temperature, and time, indicates the inherent variability in, for example, measuring the parameter or achieving the parameter. A person skilled in the art, having the benefit of this disclosure, would understand the variability of a parameter as connoted by the use of the word about.

[0054] As used herein, "similar" in reference to a form exhibiting characteristics similar to, for example, an XRPD, an IR, a Raman spectrum, a DSC, TGA, NMR, SSNMR, etc, indicates that the polymorph or cocrystal is identifiable by that method and could range from similar to substantially similar, so long as the material is identified by the method with variations expected by one of skill in the art according to the experimental variations, including, for example, instruments used, time of day, humidity, season, pressure, room temperature, etc.

[0055] As used herein, "rifaximin solid dispersion," "rifaximin ternary dispersion," "solid dispersion of rifaximin," "solid dispersion", "solid dispersion forms of rifaximin", "SD", "SDD", and "form solid dispersion of rifaximin" are intended to have equivalent meanings and include rifaximin polymer dispersion composition. These compositions are XRPD amorphous, but distinguishable from XRPD of amorphous rifaximin. As shown in the Examples and Figures, the rifaximin polymer dispersion compositions are physically chemically distinguishable from amorphous rifaximin, including different Tg, different XRPD profiles and different dissolution profiles.

[0056] Polymorphism, as used herein, refers to the occurrence of different crystalline forms of a single compound in distinct hydrate status, e.g., a property of some compounds and complexes. Thus, polymorphs are distinct solids sharing the same molecular formula, yet each polymorph may have distinct physical properties. Therefore, a single compound may give rise to a variety of polymorphic forms where each form has different and distinct physical properties, such as solubility profiles, melting point temperatures, hygroscopicity, particle shape, density, flowability, compactibility and/or x-ray diffraction peaks. The solubility of each polymorph may vary, thus, identifying the existence of pharmaceutical polymorphs is essential for providing pharmaceuticals with predictable solubility profiles. It is desirable to investigate all solid state forms of a drug, including all polymorphic forms, and to determine the stability, dissolution and flow properties of each polymorphic form. Polymorphic forms of a compound can be distinguished in a laboratory by X-ray diffraction spectroscopy and by other methods such as, infrared spectrometry. For a general review of polymorphs and the pharmaceutical applications of polymorphs see G. M. Wall, Pharm Manuf. 3, 33 (1986); J. K. Haleblian and W. McCrone, J Pharm. Sci., 58, 911 (1969); and J. K. Haleblian, J. Pharm. Sci., 64, 1269 (1975).

[0057] As used herein, "subject" includes organisms which are capable of suffering from a bowel disorder or other disorder treatable by rifaximin or who could otherwise benefit from the administration of rifaximin solid dispersion compositions as described herein, such as human and non-human animals. The term "non-human animals" includes all vertebrates, e.g., mammals, e.g., rodents, e.g., mice, and non-mammals, such as non-human primates, e.g., sheep, dog, cow, chickens, amphibians, reptiles, etc. Susceptible to a bowel disorder is meant to include subjects at risk of developing a bowel disorder infection, e.g., subjects suffering from one or more of an immune suppression, subjects that have been exposed to other subjects with a bacterial infection, physicians, nurses, subjects traveling to remote areas known to harbor bacteria that causes travelers' diarrhea, subjects who drink amounts of alcohol that damage the liver, subjects with a history of hepatic dysfunction, etc.

[0058] The language "a prophylactically effective amount" of a composition refers to an amount of a rifaximin solid dispersion formulation or otherwise described herein which is effective, upon single or multiple dose administration to the subject, in preventing or treating a bacterial infection.

[0059] The language "therapeutically effective amount" of a composition refers to an amount of a rifaximin solid dispersion effective, upon single or multiple dose administration to the subject to provide a therapeutic benefit to the subject. In one embodiment, the therapeutic benefit is wounding or killing a bacterium, or in prolonging the survivability of a subject with such a bowel or skin disorder. In another embodiment, the therapeutic benefit is inhibiting a bacterial infection or prolonging the survival of a subject with such a bacterial infection beyond that expected in the absence of such treatment.

[0060] Rifaximin exerts a broad antibacterial activity in the gastrointestinal tract against localized gastrointestinal bacteria that cause infectious diarrhea, including anaerobic strains. It has been reported that rifaximin is characterized by a negligible systemic absorption, due to its chemical and physical characteristics (Descombe J.J. et al. Pharmacokinetic study of rifaximin after oral administration in healthy volunteers. Int J Clin Pharmacol Res, 14 (2), 51-56, (1994)).

[0061] In respect to possible adverse events coupled to the therapeutic use of rifaximin, the induction of bacterial resistance to the antibiotics is of particular relevance.

[0062] From this point of view, any differences found in the systemic absorption of the forms of rifaximin disclosed herein may be significant, because at sub-inhibitory concentration of rifaximin, such as in the range from 0.1 to 1 µg/ml, selection of resistant mutants has been demonstrated to be possible (Marchese A. et al. In vitro activity of rifaximin, metronidazole and vancomycin against clostridium difficile and the rate of selection of spontaneously resistant mutants against representative anaerobic and aerobic bacteria, including ammonia-producing species. Chemotherapy, 46(4), 253-266,(2000)).

[0063] Forms, formulations and compositions of rifaximin have been found to have differing in vivo bioavailability properties. Thus, the polymorphs disclosed herein would be useful in the preparation of pharmaceuticals with different characteristics for the treatment of infections. This would allow generation of rifaximin preparations that have significantly different levels of adsorption with Cmax values from about 0.0 ng/ml to 5.0 µg/ml. This leads to preparation of rifaximin compositions that are from negligibly to significantly adsorbed by subjects undergoing treatment. One embodiment described herein is modulating the therapeutic action of rifaximin by selecting the proper form, formulation and/or composition, or mixture thereof, for treatment of a subject. For example, in the case of invasive bacteria, the most bioavailable form, formulation and/or composition can be selected from those disclosed herein, whereas in case of non-invasive pathogens less adsorbed forms, formulations and/or compositions of rifaximin can be selected, since they may be safer for the subject undergoing treatment. A form, formulation and/or composition of rifaximin may determine solubility, which may also determine bioavailability.

[0064] For XRPD analysis, accuracy and precision associated with third party measurements on independently prepared samples on different instruments may lead to variability which is greater than ±0.1° 2θ. For d-space listings, the wavelength used to calculate d-spacings was 1.541874 Å, a weighted average of the Cu-Kα1 and Cu-Kα2 wavelengths. Variability associated with d-spacing estimates was calculated from the USP recommendation, at each d-spacing, and provided in the respective data tables and peak lists.

Methods of Treatment



[0065] Described herein are methods of treating, preventing, or alleviating bowel related disorders comprising administering to a subject in need thereof an effective amount of one or more of the solid dispersion compositions of rifaximin. In particular, the present invention relates to the solid dispersion form of rifaximin as described herein for use in treating, preventing, or alleviating bowel related disorders.

[0066] Bowel related disorders include one or more of irritable bowel syndrome, diarrhea, microbe associated diarrhea, Clostridium difficile associated diarrhea, travelers' diarrhea, small intestinal bacterial overgrowth, Crohn's disease, diverticular disease, chronic pancreatitis, pancreatic insufficiency, enteritis, colitis, hepatic encephalopathy, minimal hepatic encephalopathy or pouchitis.

[0067] The length of treatment for a particular bowel disorder will depend in part on the disorder. For example, travelers' diarrhea may only require treatment duration of 12 to about 72 hours, while Crohn's disease may require treatment durations from about 2 days to 3 months. Dosages of rifaximin will also vary depending on the diseases state. Proper dosage ranges are provided herein infra. The polymorphs and cocrystals described herein may also be used to treat or prevent apathology in a subject suspected of being exposed to a biological warfare agent.

[0068] The identification of those subjects who are in need of prophylactic treatment for bowel disorder is well within the ability and knowledge of one skilled in the art. Certain of the methods for identification of subjects which are at risk of developing a bowel disorder which can be treated by the subject method are appreciated in the medical arts, such as family history, travel history and expected travel plans, the presence of risk factors associated with the development of that disease state in the subject. A clinician skilled in the art can readily identify such candidate subjects, by the use of, for example, clinical tests, physical examination and medical/family/travel history.

[0069] Topical skin infections and vaginal infections may also be treated with the rifaximin compositions described herein. Thus, described herein are methods of using a solid dispersion composition of rifaximin (SD rifaximin compositions) to treat vaginal infections, ear infections, lung infections, periodontal conditions, rosacea, and other infections of the skin and/or other related conditions. Provided herein are vaginal pharmaceutical compositions to treat vaginal infection, particularly bacterial vaginosis, to be administered topically, including vaginal foams and creams, containing a therapeutically effective amount of SD rifaximin compositions, preferably between about 50 mg and 2500 mg. Pharmaceutical compositions known to those of skill in the art for the treatment of vaginal pathological conditions by the topical route may be advantageously used with SD rifaximin compositions. For example, vaginal foams, ointments, creams, gels, ovules, capsules, tablets and effervescent tablets may be effectively used as pharmaceutical compositions containing SD rifaximin compositions, which may be administered topically for the treatment of vaginal infections, including bacterial vaginosis. Also provided herein are method of using SD rifaximin compositions to treat gastric dyspepsia, including gastritis, gastroduodenitis, antral gastritis, antral erosions, erosive duodenitis and peptic ulcers. These conditions may be caused by the Helicobacter pylori. Pharmaceutical formulations known by those of skill in the art with the benefit of this disclosure to be used for oral administration of a drug may be used. Provided herein are methods of treating ear infections with SD rifaximin compositions. Ear infections include external ear infection, or a middle and inner ear infection. Also provided herein are methods of using SD rifaximin compositions to treat or prevent aspiration pneumonia and/or sepsis, including the prevention of aspiration pneumonia and/or sepsis in patients undergoing acid suppression or undergoing artificial enteral feedings via a Gastrostomy/Jejunostomy or naso/oro gastric tubes; prevention of aspiration pneumonia in patients with impairment of mental status, for example, for any reason, for subjects undergoing anesthesia or mechanical ventilation that are at high risk for aspiration pneumonia. Provided herein are methods to treat or to prevent periodontal conditions, including plaque, tooth decay and gingivitis. Provided herein are methods of treating rosacea, which is a chronic skin condition involving inflammation of the cheeks, nose, chin, forehead, or eyelids.

Pharmaceutical Preparations



[0070] Embodiments also provide pharmaceutical compositions, comprising an effective amount of one or more SD rifaximin compositions, or microgranules comprising SD forms of rifaximin described herein (e.g., described herein and a pharmaceutically acceptable carrier). In particular, the present invention provides a pharmaceutical composition comprising the solid dispersion form of rifaximin as described herein and at least one pharmaceutically acceptable excipient.

[0071] In a further embodiment, the effective amount is effective to treat a bacterial infection, e.g., small intestinal bacterial overgrowth, Crohn's disease, hepatic encephalopathy, antibiotic associated colitis, and/or diverticular disease. Embodiments also provide pharmaceutical compositions, comprising an effective amount of rifaximin SD compositions.

[0072] For examples of the use of rifaximin to treat Travelers' diarrhea, see Infante RM, Ericsson CD, Zhi-Dong J, Ke S, Steffen R, Riopel L, Sack DA, DuPont, HL., Enteroaggregative Escherichia coli Diarrhea in Travelers: Response to Rifaximin Therapy. Clinical Gastroenterology and Hepatology. 2004;2:135-138; and Steffen R, M.D., Sack DA, M.D., Riopel L, Ph.D., Zhi-Dong J, Ph.D., Sturchler M, M.D., Ericsson CD, M.D., Lowe B, M.Phil., Waiyaki P, Ph.D., White M, Ph.D., DuPont HL, M.D. Therapy of Travelers' Diarrhea With Rifaximin on Various Continents. The American Journal of Gastroenterology. May 2003, Volume 98, Number 5. Examples of treating hepatic encephalopathy with rifaximin see, for example, N. Engl J Med. 2010_362_1071-1081.

[0073] Embodiments also provide pharmaceutical compositions comprising rifaximin SD compositions and a pharmaceutically acceptable carrier. Embodiments of the pharmaceutical composition further comprise excipients, for example, one or more of a diluting agent, binding agent, lubricating agent, intragranular release controlling agent, e.g., a disintegrating agent, coloring agent, flavoring agent or sweetening agent. One composition may be formulated for selected coated and uncoated tablets, hard and soft gelatin capsules, sugar-coated pills, lozenges, wafer sheets, pellets and powders in sealed packet. For example, compositions may be formulated for topical use, for example, ointments, pomades, creams, gels and lotions.

[0074] In a disclosure, the rifaximin SD composition is administered to the subject using a pharmaceutically-acceptable formulation, e.g., a pharmaceutically-acceptable formulation that provides sustained or delayed delivery of the SD rifaximin composition to a subject for at least 2, 4, 6, 8, 10, 12 hours, 24 hours, 36 hours, 48 hours, one week, two weeks, three weeks, or four weeks after the pharmaceutically-acceptable formulation is administered to the subject. The pharmaceutically-acceptable formulations may contain microgranules comprising rifaximin as described herein.

[0075] In certain embodiments, these pharmaceutical compositions are suitable for topical or oral administration to a subject. In other embodiments, as described in detail below, the pharmaceutical compositions described herein may be specially formulated for administration in solid or liquid form, including those adapted for the following: (1) oral administration, for example, drenches (aqueous or non-aqueous solutions or suspensions), tablets, boluses, powders, granules, pastes; (2) parenteral administration, for example, by subcutaneous, intramuscular or intravenous injection as, for example, a sterile solution or suspension; (3) topical application, for example, as a cream, ointment or spray applied to the skin; (4) intravaginally or intrarectally, for example, as a pessary, cream or foam; or (5) aerosol, for example, as an aqueous aerosol, liposomal preparation or solid particles containing the compound.

[0076] The phrase "pharmaceutically acceptable" refers to those SD rifaximin compositions and cocrystals presented herein, compositions containing such compounds, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio.

[0077] The phrase "pharmaceutically-acceptable carrier" includes pharmaceutically-acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, excipient, solvent or encapsulating material, involved in carrying or transporting the subject chemical from one organ, or portion of the body, to another organ, or portion of the body. Each carrier is preferably "acceptable" in the sense of being compatible with the other ingredients of the formulation and not injurious to the subject. Some examples of materials which can serve as pharmaceutically-acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer's solution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxic compatible substances employed in pharmaceutical formulations.

[0078] Wetting agents, emulsifiers and lubricants, such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, release agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the compositions.

[0079] Examples of pharmaceutically-acceptable antioxidants include: (1) water soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate, alpha-tocopherol, and the like; and (3) metal chelating agents, such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol, tartaric acid, phosphoric acid, and the like.

[0080] Methods of preparing these compositions include the step of bringing into association a SD rifaximin composition(s) or microgranules containing the SD rifaximin compositions with the carrier and, optionally, one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association a SD rifaximin composition with liquid carriers, or finely divided solid carriers, or both, and then, if necessary, shaping the product.

[0081] Compositions suitable for oral administration may be in the form of capsules, cachets, pills, tablets, lozenges (using a flavored basis, usually sucrose and acacia or tragacanth), powders, granules, or as a solution or a suspension in an aqueous or non-aqueous liquid, or as an oil-in-water or water-in-oil liquid emulsion, or as an elixir or syrup, or as pastilles (using an inert base, such as gelatin and glycerin, or sucrose and acacia) and/or as mouth washes and the like, each containing a predetermined amount of a SD rifaximin composition(s) as an active ingredient. A compound may also be administered as a bolus, electuary or paste.

[0082] The SD compositions of rifaximin disclosed herein can be advantageously used in the production of medicinal preparations having antibiotic activity, containing rifaximin, for both oral and topical use. The medicinal preparations for oral use will contain an SD composition of rifaximin together with the usual excipients, for example diluting agents such as mannitol, lactose and sorbitol; binding agents such as starches, gelatines, sugars, cellulose derivatives, natural gums and polyvinylpyrrolidone; lubricating agents such as talc, stearates, hydrogenated vegetable oils, polyethylenglycol and colloidal silicon dioxide; disintegrating agents such as starches, celluloses, alginates, gums and reticulated polymers; coloring, flavoring, disintegrants, and sweetening agents.

[0083] Embodiments described herein include SD rifaximin composition administrable by the oral route, for instance coated and uncoated tablets, of soft and hard gelatin capsules, sugar-coated pills, lozenges, wafer sheets, pellets and powders in sealed packets or other containers.

[0084] Pharmaceutical compositions for rectal or vaginal administration may be presented as a suppository, which may be prepared by mixing one or more SD rifaximin composition(s) with one or more suitable nonirritating excipients or carriers comprising, for example, cocoa butter, polyethylene glycol, a suppository wax or a salicylate, and which is solid at room temperature, but liquid at body temperature and, therefore, will melt in the rectum or vaginal cavity and release the active agent. Compositions which are suitable for vaginal administration also include pessaries, tampons, creams, gels, pastes, foams or spray formulations containing such carriers as are known in the art to be appropriate.

[0085] Dosage forms for the topical or transdermal administration of a SD rifaximin composition(s) include powders, sprays, ointments, pastes, creams, lotions, gels, solutions, patches and inhalants. The active SD rifaximin composition(s) may be mixed under sterile conditions with a pharmaceutically-acceptable carrier, and with any preservatives, buffers, or propellants which may be required.

[0086] Ointments, pastes, creams and gels may contain, in addition to SD rifaximin composition(s), excipients, such as animal and vegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonites, silicic acid, talc and zinc oxide, or mixtures thereof.

[0087] Powders and sprays can contain, in addition to a SD rifaximin composition(s), excipients such as lactose, talc, silicic acid, aluminium hydroxide, calcium silicates and polyamide powder, or mixtures of these substances. Sprays can additionally contain customary propellants, such as chlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, such as butane and propane.

[0088] The SD rifaximin composition(s) can be alternatively administered by aerosol. This is accomplished by preparing an aqueous aerosol, liposomal preparation or solid particles containing the compound. A non-aqueous (e.g., fluorocarbon propellant) suspension could be used. Sonic nebulizers are preferred because they minimize exposing the agent to shear, which can result in degradation of the compound.

[0089] An aqueous aerosol is made, for example, by formulating an aqueous solution or suspension of the agent together with conventional pharmaceutically-acceptable carriers and stabilizers. The carriers and stabilizers vary with the requirements of the particular compound, but typically include non-ionic surfactants (Tweens, Pluronics, or polyethylene glycol), innocuous proteins like serum albumin, sorbitan esters, oleic acid, lecithin, amino acids such as glycine, buffers, salts, sugars or sugar alcohols. Aerosols generally are prepared from isotonic solutions.

[0090] Transdermal patches have the added advantage of providing controlled delivery of a SD rifaximin composition(s) to the body. Such dosage forms can be made by dissolving or dispersing the agent in the proper medium. Absorption enhancers can also be used to increase the flux of the active ingredient across the skin. The rate of such flux can be controlled by either providing a rate controlling membrane or dispersing the active ingredient in a polymer matrix or gel.

[0091] Ophthalmic formulations, eye ointments, powders, solutions and the like, are also contemplated as being within the scope of the invention.

[0092] Pharmaceutical compositions suitable for parenteral administration may comprise one or more SD rifaximin composition(s) in combination with one or more pharmaceutically-acceptable sterile isotonic aqueous or nonaqueous solutions, dispersions, suspensions or emulsions, or sterile powders which may be reconstituted into sterile injectable solutions or dispersions just prior to use, which may contain antioxidants, buffers, bacteriostats, solutes which render the formulation isotonic with the blood of the intended recipient or suspending or thickening agents.

[0093] Examples of suitable aqueous and non-aqueous carriers which may be employed in the pharmaceutical compositions include water, ethanol, polyols (such as glycerol, propylene glycol, polyethylene glycol, and the like), and suitable mixtures thereof, vegetable oils, such as olive oil, and injectable organic esters, such as ethyl oleate. Proper fluidity can be maintained, for example, by the use of coating materials, such as lecithin, by the maintenance of the required particle size in the case of dispersions, and by the use of surfactants.

[0094] When the SD rifaximin composition(s) are administered as pharmaceuticals, to humans and animals, they can be given per se or as a pharmaceutical composition containing, for example, 0.1 to 99.5% (more preferably, 0.5 to 90%) of active ingredient in combination with a pharmaceutically-acceptable carrier.

[0095] Regardless of the route of administration selected, the SD rifaximin composition(s) are formulated into pharmaceutically-acceptable dosage forms by methods known to those of skill in the art.

[0096] Actual dosage levels and time course of administration of the active ingredients in the pharmaceutical compositions may be varied so as to obtain an amount of the active ingredient which is effective to achieve the desired therapeutic response for a particular subject, composition, and mode of administration, without being toxic to the subject. An exemplary dose range is from 25 to 3000 mg per day. Other doses include, for example, 600mg/day, 1100mg/day and 1650mg/day. Other exemplary doses include, for example, 1000mg/day, 1500mg/day, from between 500mg to about 1800mg/day or any value in-between.

[0097] A preferred dose of the SD rifaximin composition disclosed herein is the maximum that a subject can tolerate without developing serious side effects. Preferably, the SD rifaximin composition is administered at a concentration of about 1 mg to about 200 mg per kilogram of body weight, about 10 to about 100 mg/kg or about 40 mg to about 80 mg/kg of body weight. Ranges intermediate to the above-recited values are also intended to be part. For example, doses may range from 50mg to about 2000mg/day.

[0098] In combination therapy treatment, the other drug agent(s) are administered to mammals (e.g., humans, male or female) by conventional methods. The agents may be administered in a single dosage form or in separate dosage forms. Effective amounts of the other therapeutic agents are well known to those skilled in the art. However, it is well within the skilled artisan's purview to determine the other therapeutic agent's optimal effective-amount range. In one disclosure in which another therapeutic agent is administered to an animal, the effective amount of the rifaximin SD composition is less than its effective amount in case the other therapeutic agent is not administered. In another embodiment, the effective amount of the conventional agent is less than its effective amount in case the rifaximin SD composition is not administered. In this way, undesired side effects associated with high doses of either agent may be minimized. Other potential advantages (including without limitation improved dosing regimens and/or reduced drug cost) will be apparent to those skilled in the art.

[0099] In various disclosures, the therapies (e.g., prophylactic or therapeutic agents) are administered less than 5 minutes apart, less than 30 minutes apart, 1 hour apart, at about 1 hour apart, at about 1 to about 2 hours apart, at about 2 hours to about 3 hours apart, at about 3 hours to about 4 hours apart, at about 4 hours to about 5 hours apart, at about 5 hours to about 6 hours apart, at about 6 hours to about 7 hours apart, at about 7 hours to about 8 hours apart, at about 8 hours to about 9 hours apart, at about 9 hours to about 10 hours apart, at about 10 hours to about 11 hours apart, at about 11 hours to about 12 hours apart, at about 12 hours to 18 hours apart, 18 hours to 24 hours apart, 24 hours to 36 hours apart, 36 hours to 48 hours apart, 48 hours to 52 hours apart, 52 hours to 60 hours apart, 60 hours to 72 hours apart, 72 hours to 84 hours apart, 84 hours to 96 hours apart, or 96 hours to 120 hours part. In preferred disclosures, two or more therapies are administered within the same subject's visit.

[0100] In certain disclosures, one or more compounds and one or more other therapies (e.g., prophylactic or therapeutic agents) are cyclically administered. Cycling therapy involves the administration of a first therapy (e.g., a first prophylactic or therapeutic agent) for a period of time, followed by the administration of a second therapy (e.g., a second prophylactic or therapeutic agent) for a period of time, optionally, followed by the administration of a third therapy (e.g., prophylactic or therapeutic agent) for a period of time and so forth, and repeating this sequential administration, i.e., the cycle in order to reduce the development of resistance to one of the therapies, to avoid or reduce the side effects of one of the therapies, and/or to improve the efficacy of the therapies.

[0101] In certain disclosures, the administration of the same compounds may be repeated and the administrations may be separated by at least 1 day, 2 days, 3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2 months, 75 days, 3 months, or at least 6 months. In other disclosures, the administration of the same therapy (e.g., prophylactic or therapeutic agent) other than a SD rifaximin composition may be repeated and the administration may be separated by at least 1 day, 2 days, 3 days, 5 days, 10 days, 15 days, 30 days, 45 days, 2 months, 75 days, 3 months, or at least 6 months.

[0102] Certain indications may require longer treatment times. For example, travelers' diarrhea treatment may only last from between about 12 hours to about 72 hours, while a treatment for Crohn's disease may be from between about 1 day to about 3 months. A treatment for hepatic encephalopathy may be, for example, for the remainder of the subject's life span. A treatment for IBS may be intermittent for weeks or months at a time or for the remainder of the subject's life.

Compositions and Formulations



[0103] Rifaximin solid dispersions, pharmaceutical compositions comprising SD rifaximin or microgranules comprising rifaxmin solid dispersions, can be made from, for example, polymers including polyvinylpyrrolidone (PVP) grade K-90, hydroxypropyl methylcellulose phthalate (HPMC-P) grade 55, hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grades HG and MG, and a polymethacrylate (Eudragit® L100-55), with the provision that solid dispersion forms of rifaximin comprise rifaximin and a polymer selected from hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grade HG and grade MG. Rifaximin solid dispersion compositions are comprised of, for example, 10:90, 15:85, 20:80, 25:75, 30:70, 40:60, 50:50 60:40, 70:30, 75:25, 80:20, 85:15, and 90:10 (Rifaximin/polymer, by weight). In particular, the rifaximin:polymer weight ratio ranges from 10:90 to 90:10. Preferred solid dispersions are comprised of 25:75, 50:50 and 75:25 (Rifaximin/polymer, by weight). In addition to rifaximin and polymer, solid dispersions may also comprise surfactants, for example, non-ionic, surfactant polyols.

[0104] An example of a formulation comprises about 50:50 (w/w) Rifaximin:HPMC-AS MG with from between about 2 wt% to about 10 wt% of a non-ionic, surfactant polyol, for example, Pluronic F-127.

[0105] One example of a formulation comprises 50:50 (w/w) Rifaximin:HPMC-AS MG with about 5.9 wt%) of a non-ionic, surfactant polyol, for example, Pluronic F-127. Spray dried rifaximin ternary dispersion (50:50 (w/w) rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127) was blended with 10 wt% croscarmellose sodium and then filled into gelatin capsules. Each capsule contains 275 mg of rifaximin and the blend formulation is 85:5:10 of 50:50 (w/w) Rifaximin:HPMC-AS MG : Pluronic : croscarmellose sodium (calculated in total solids). Other examples of microgranules and pharmaceutical compositions comprising SD rifaximin are described in the examples.

[0106] To form the rifaximin solid dispersion, the components, e.g., rifaximin, polymer and methanol are mixed and then spray dried. Exemplary conditions are summarized in Table 9 and the procedure outlined below and in Examples 3 and 4.

[0107] Exemplary Spray Drying Process Parameters, include for example:
  • Spray Dryer - e.g., PSD 1;
  • Single or multi-fluid nozzle: e.g., a two Fluid Niro Nozzle;
  • Nozzle orifice - 0.1 - 10 mm;
  • Inlet gas temperature - 75 - 150±5 deg C;
  • Process gas flow (mmH2O) - 20 - 70, preferred 44;
  • Atomizing gas pressure - 0.7 - 1 bar;
  • Feed rate - 2 - 7 kg/Hr;
  • Outlet temperature - 30 - 70 ± 3 deg C;
  • Solution temperature - 20 - 50 deg C; and
  • Post spray drying vacuum dry at 20 - 60 deg C, for between about 2 and 72 hrs.

Article of Manufacture



[0108] Another embodiment includes articles of manufacture that comprise, for example, a container holding a rifaximin SD pharmaceutical composition suitable for oral or topical administration of rifaximin in combination with printed labeling instructions providing a discussion of when a particular dosage form should be administered with food and when it should be taken on an empty stomach. Exemplary dosage forms and administration protocols are described infra. The composition will be contained in any suitable container capable of holding and dispensing the dosage form and which will not significantly interact with the composition and will further be in physical relation with the appropriate labeling. The labeling instructions will be consistent with the methods of treatment as described hereinbefore. The labeling may be associated with the container by any means that maintain a physical proximity of the two, by way of non-limiting example, they may both be contained in a packaging material such as a box or plastic shrink wrap or may be associated with the instructions being bonded to the container such as with glue that does not obscure the labeling instructions or other bonding or holding means.

[0109] Another aspect is an article of manufacture that comprises a container containing a pharmaceutical composition comprising SD rifaximin composition or formulation wherein the container holds preferably rifaximin composition in unit dosage form and is associated with printed labeling instructions advising of the differing absorption when the pharmaceutical composition is taken with and without food.

[0110] Packaged compositions are also provided, and may comprise a therapeutically effective amount of rifaximin. Rifaximin SD composition and a pharmaceutically acceptable carrier or diluent, wherein the composition is formulated for treating a subject suffering from or susceptible to a bowel disorder, and packaged with instructions to treat a subject suffering from or susceptible to a bowel disorder.

[0111] Kits are also provided herein, for example, kits for treating a bowel disorder in a subject. The kits may contain, for example, one or more of the solid dispersion forms of rifaximin and instructions for use. The instructions for use may contain proscribing information, dosage information, storage information, and the like.

[0112] Packaged compositions are also provided, and may comprise a therapeutically effective amount of an SD rifaximin composition and a pharmaceutically acceptable carrier or diluent, wherein the composition is formulated for treating a subject suffering from or susceptible to a bowel disorder, and packaged with instructions to treat a subject suffering from or susceptible to a bowel disorder.

[0113] The present invention is further illustrated by the following examples, which should not be construed as further limiting.

EXAMPLES



[0114] The chemical structure of Rifaximin is shown below in Figure 1.

Example 1. Solid Dispersions of Rifaximin



[0115] Various polymers were formulated with rifaximin into solids prepared by methanol and spray drying at small scale (∼ 1g). Polymers, including polyvinylpyrrolidone (PVP) grade K-90 (for reference), hydroxypropyl methylcellulose phthalate (HPMC-P) grade 55 (for reference), hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grades HG and MG, and a polymethacrylate (Eudragit® L100-55) (for reference) were used. Solids have compositions of 25:75, 50:50 and 75:25 (Rifaximin/polymer, by weight).

[0116] Samples generated were observed under polarized light microscope after preparation and were characterized by XRPD. The results are included in Table 1 through Table 5. Birefringence with extinction (B/E) was not observed for any of the samples, indicating solids without crystalline order were obtained. No sharp peaks were evident by visual inspection of XRPD patterns of these samples, consistent with non-crystalline materials, as shown in Figure 2 (with PVP K-90), Figure 7 (with HPMC-P), Figure 12 (with HMPC-AS HG), Figure 12 (with HMPC-AS MG), and Figure 17 (with Eudragit LI00-55).

[0117] Materials were characterized by mDSC where the appearance of a single glass transition temperature (Tg), provides support for a non-crystalline fully miscible dispersion. All the dispersions prepared with PVP K-90 display a single apparent Tg at approximately 185 °C (Figure 3, 25:75 w/w), 193°C (Figure 4, 50:50 w/w), and 197°C (Figure 5, 75:25) respectively. The change in heat capacity (ΔCp) at Tg is approximately 0.3 J/g·°C for each dispersion. A non-reversible endotherm, which is likely due to the residual solvent in the materials, was observed in each of Rifaximin /PVP K-90 dispersions centered at approximately 78°C, 59 °C and 61°C.

[0118] From Figure 6, Tg of Rifaximin/PVP K-90 dispersions increases with the increased Rifaximin concentration, which is due to the higher Tg of Rifaximin (199 °C) than PVP K-90 (174 °C). Evidence of a single Tg may suggest that the components of the dispersion are intimately mixed, or miscible.

[0119] Dispersions prepared with other polymers also display a single apparent Tg, as a step change in the reversing heat flow signal by mDSC. Dispersions prepared with HPMC-P exhibit Tg at 153°C (Figure 8, 25:75 w/w), 161°C (Figure 9, 50:50 w/w) and 174°C (Figure 10, 75:25 w/w) respectively, with ΔCp at Tg approximately 0.4 J/g·°C.

[0120] With HPMC-AS HG, dispersions display Tg at 137°C (Figure 13, 25:75 w/w), 154 °C (Figure 14, 50:50 w/w) and 177 °C (Figure 15, 75:25 w/w) respectively; ΔCp at Tg is approximately 0.4 or 0.3 J/g·°C.

[0121] With HPMC-AS MG, dispersions display Tg at 140°C (Figure 18, 25:75 w/w), 159 °C (Figure 19, 50:50 w/w) and 177 °C (Figure 10, 75:25 w/w) respectively; ΔCp at Tg is approximately 0.4 or 0.3 J/g·°C.

[0122] Dispersions prepared with Eudragit L100-55 exhibit Tg at 141°C with ΔCp approximately 0.5 J/g·°C (Figure 23, 25:75 w/w), 159°C with ΔCp approximately 0.3 J/g·°C (Figure 24, 50:50 w/w), and 176°C with ΔCp at Tg approximately 0.2 J/g·°C (Figure 25, 75:25 w/w) respectively.

[0123] Similarly, as shown in Figure 11 (with HPMC-P), Figure 16 (with HPMC-AS HG), Figure 21 (with HPMC-AS MG, and Figure 26 (with Eudragit L100-55), Tg of material in each set of Rifaximin/polymer dispersions increases with the increased Rifaximin concentration due to the higher Tg of Rifaximin.

Physical Stability Assessment



[0124] An assessment of physical stability for rifaximin/polymer dispersions was conducted under stress conditions of aqueous solutions at different biologically relevant conditions, including 0.1N HCl solution at 37°C and pH 6.5 FASSIF buffer at 37°C, elevated temperature/relative humidity (40 °C/75% RH), and elevated temperature/dry (60°C). The x-ray amorphous rifaximin - only sample prepared from methanol by spray drying was also stressed under the same conditions for comparison.

Stress in 0.1N HCl solution at 37 °C



[0125] For the assessment of physical stability for samples in a 0.1N HCl solution maintained at 37°C, observations were made and microscopy images were acquired using polarized light at different time points including 0, 6 and 24 hrs, as summarized in Table 6. Based on the absence of birefringent particles when samples were observed by PLM, dispersions prepared with HPMC-AS HG and HPMC-AS MG display the highest physical stability under this particular stress condition. The results of this study for each of samples are discussed below.

[0126] X-ray amorphous Rifaximin stressed in 0.1N HCl solution at 37°C at 0, 6, and 24 hrs showed evidence of birefringence/extinctions was observed at 6hrs, indicating the occurrence of devitrification of the material.

[0127] Samples at compositions of 25:75 and 50:50 (w/w) crystallized at 6 hrs; sample at 75:25 (w/w) composition crystallized within 24 hrs while no evidence of crystallization was observed at 6 hrs or earlier. The decreased stability of Rifaximin/PVP K-90 dispersions in 0.1N HCl solution with increased PVP K-90 concentration may due to the high solubility of PVP K-90 in the solution.

[0128] Irregular aggregates without birefringence/extinctions were observed for dispersion prepared with HPMC-P at t = 0 hr, the initial time point when 0.1N HCl solution was just added into solids. After 24 hrs, samples at compositions of 25:75 and 50:50 (w/w) remained as non-birefringent aggregates, indicating no occurrence of devitrification under the conditions examined. Evidence of crystallization was observed for sample of 75:25 (w/w) composition at 6 hrs. No birefringence/extinctions were observed for all of dispersions prepared with HPMC-AS HG and HPMC-AS MG after 24 hrs, suggesting these samples are resistant to devitrification upon exposure to 0.1N HCl solution for 24 hrs.

[0129] For dispersions prepared with Eudragit L100-55, upon exposure to 0.1N HCl solution for 24 hrs, birefringent particles with extinctions were observed only in the sample at 50:50 (w/w) composition. Considered that no evidence of crystallization was observed for dispersions of compositions at 25:75 and 75:25 (w/w), it is unknown whether such birefringence was caused by some foreign materials or by crystalline solids indicating the occurrence of devitrification.

Stress in pH 6.5 FASSIF buffer at 37 °C



[0130] An assessment of physical stability of dispersions prepared was also performed in pH 6.5 FASSIF buffer maintained at 37°C. X-ray amorphous Rifaximin material was also stressed under same condition for comparison. PLM observations indicated that dispersions prepared from HPMC-AS HG and HPMC-AS MG display the highest physical stability under this stress condition. X-ray amorphous rifaximin-only material crystallized within 6 hrs, so did all rifaximin/PVP K-90 dispersions. For dispersions prepared with HPMC-P, birefringent particles with extinctions were observed in samples at 50:50 and 75:25 (w/w) compositions within 6 hrs, indicating the occurrence of devitrification in materials. No evidence of any birefringence/extinctions was observed in 25:75 (w/w) rifaximin/HPMC-P dispersion material after 24 hrs. No birefringence/extinctions were observed for all of dispersions prepared with HPMC-AS HG and HPMC-AS MG after 24 hrs, suggesting these samples are resistant to devitrification upon exposure to pH 6.5 FASSIF buffer for 24 hrs. Rifaximin/Eudragit L100-55 dispersions at 50:50 and 75:25 (w/w) compositions crystallized with 6 hrs while no evidence of crystallization was observed in the sample at 25:75 (w/w) composition after 24 hrs.

Stress at 40 °C/ 75% RH condition



[0131] The samples including all the dispersions and x-ray amorphous rifaximin-only material were assessed for evidence of crystallization based on observations by microscopy using polarized light. Each of the samples remained as irregular aggregates without birefringence/extinctions after stressed at 40 °C/ 75% RH condition for 7 days.

[0132] Modulated DSC analyses were carried out on selected samples including 25:75 (w/w) rifaximin/HPMC-P, 75:25 (w/w) rifaximin/HPMC-AS HG, 75:25 (w/w) rifaximin/HPMC-AS MG, and 25:75 (w/w) Rifaximin/Eudragit L100-55 to inspect for evidence of phase separation after exposure to 40 °C/ 75% RH for 7 days. All of samples display a single apparent Tg at approximately 148°C (Figure 27 , 25:75 (w/w) HPMC-P), 177 °C (Figure 28, 75:25 (w/w) HPMC-AS HG) 152°C (Figure 29, 75:25 (w/w) HPMC-AS MG) and 140°C (Figure 30, 25:75 (w/w) Eudragit L100-55) respectively, indicating the components of each dispersion remained intimately miscible after stress. Although crimped with manual pin-hole DSC pan was used, the release of moisture from sample upon heating can still be observed from non-reversible heat flow signals.

Stress at 60 °C/ dry condition



[0133] All the dispersions and x-ray amorphous rifaximin-only material were also stressed at 60 °C/ dry condition for 7 days and were assessed for evidence of crystallization based on observations by microscopy using polarized light. Each of the samples remained as irregular aggregates without birefringence/extinctions after stressed at this condition for 7 days.

Rifaximin Solid Dispersions by Spray Drying



[0134] Based on the experimental results from screen, HPMC-AS MG and HPMC-P were used to prepare additional quantities of solid dispersions at gram-scale by spray drying. The operating parameters used for processing are presented in Table 9. Based on visual inspection, both dispersions were x-ray amorphous by XRPD (Figure 31 and Figure 36).

Characterization of 50:50 (w/w) Rifaximin/HPMC-AS MG Dispersion



[0135] Characterization and results for the 50% API loading HPMC-AS MG are summarized in Table 10. The sample was x-ray amorphous based on high resolution XRPD. A single Tg at approximately 154 °C was observed from the apparent step change in the reversing heat flow signal in mDSC with the change of heat capacity 0.4 J/ g °C. A non-reversible endotherm was observed at approximately 39°C which is likely due to the residual solvent in the materials (Figure 32). TG-IR analysis was carried out in order to determine volatile content on heating. TGA data for this material is shown in Figure 34. There was a 0.5% weight loss up to ∼100 °C. A Gram-Schmidt plot corresponding to the overall IR intensity associated with volatiles released by solids upon heating at 20 °C/min is shown in Figure 33. There was a dramatic increase of intensity of released volatiles after ∼8 minutes, with a maximum at ∼ 11.5 minutes. The waterfall plot (Figure 34) and the linked IR spectrum (Figure 35) are indicative of the loss of water loss up to ∼8 minutes then methanol and some unknown volatiles thereafter. This is consistent with the dramatic change in the slope in the TGA and may indicate decomposition of material.

Characterization of 25:75 (w/w) Rifaximin/HPMC-P Dispersion (for reference)



[0136] Characterization and results for the 25% API loading dispersion of HPMC-P are summarized in Table 11. Solids were x-ray amorphous based on high resolution XRPD (Figure 36). By mDSC, there is a single Tg at approximately 152°C from the apparent step change in the reversing heat flow signal. The change of heat capacity is 0.4 J/ g °C (Figure 37). A non-reversible endotherm, which is likely due to the residual solvent in the materials, was observed at approximately 46 °C. Volatiles generated on heating were analyzed by TG-IR. The total weight loss of sample was approximately 1.5 wt% to 100°C and the dramatic change in the slope occurs at approximately 178 °C (Figure 38). The Gram-Schmidt plot (Figure 39) shows a small increase of intensity upon heating after ∼ 2 minutes, followed by negligible change of intensity until ∼ 9 minutes. Then dramatic change of intensity can be observed with a maximum at ∼ 11 minutes, followed by a final increase of intensity above ∼12 minutes. As seen in the waterfall plot (Figure 39), some volatiles were released during entire heating period (data is shown in Figure 40 using the linked IR spectrum at different time points as an example). The sample released water during entire heating period and methanol after ∼ 9 minutes.

Dispersions Miscibility Study by Multivariate Mixture Analysis



[0137] For Rifaximin/HPMC-AS MG dispersions prepared by spray drying, a multivariate mixture analysis was performed using the XRPD data to examine the physical state of the components and inspect for evidence of miscibility. The analysis was done with MATLAB (v7.6.0) and Unscrambler (v 9.8) and it was not performed under cGMP guidelines. XRPD patterns of all the samples were truncated with their baseline corrected, and unit area normalized before analysis. The pre-possessed XRPD patterns are shown in Figure 41.

[0138] In the analysis, Rifaximin and HPMC-AS MG were assumed to be separated phases (no miscibility) and the compositions of Rifaximin and HPMC-AS MG in each sample were estimated based on this assumption. As shown in Figure 42, the estimated ratios of Rifaximin to HPMC-AS MG based on pure separated phases did not agree with samples actual compositions, especially for the samples with high compositions of HPMC-AS MG (low Rifaximin loading). Also, the calculated XRPD patterns for Rifaximin and HMPC-AS MG based on the assumption of separated phases (Figure 43) compared to actual experimental XRPD patterns for Rifaximin (Figure 44) and HPMC-AS MG (Figure 45) were generated. Although the calculated Rifaximin pattern is similar to its experimental pattern, the calculated HMPC-AS MG pattern is quite different from its experimental pattern. Both results suggest that Rifaximin and HPMC-AS MG are not separated phases but miscible in the dispersions. The differences in the estimated and actual compositions are likely due to the interaction between Rifaximin and HPMC-AS MG.
Table 1. Solid Dispersion Attempts for Rifaximin/PVP K-90 (for reference) by Spray Drying
Description (a, b)Habit/DescriptionAnalysisResult (c)
(25:75) 90 solids orange; aggregates irregular, no B/E XRPD x-ray amorph.
mDSC 180 °C (Tg, midpoint); 0.3 J/g·°C (ΔCp)
(50:50) PVP K-90 solids orange; a ggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 193°C(Tg, midpoint); 0.3 J/g·°C (ΔCp)
(75:25) PVP K-90 solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 197°C (Tg, midpoint); 0.3 J/g·°C (ΔCp)
(a): approximate ratio of Rifaximin to polymer, by weight;
(b): samples stored in freezer over desiccant after prepared.
Table 2. Solid Dispersion Attempts for Rifaximin/HPMC-P (for reference) by Spray Drying
Description (a, b)Habit/DescriptionAnalysisResult (c)
(25:75) HPMC-P solids light orange; aggregates, irregular, no B/E XRPD x-ray amorph.
  mDSC 153°C (Tg, midpoint); 0.4 J/g·°C (ΔCp)
(50:50) HPMC-P solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
  mDSC 161 °C(Tg, midpoint); 0.4 J/g·°C (ΔCp)
(75:25) HPMC-P solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
  mDSC 174 °C(Tg, midpoint); 0.4 J/g·°C (ΔCp)
(a): approximate ratio of Rifaximin to polymer, by weight;
(b): samples stored in freezer over desiccant after prepared.
Table 3. Solid Dispersion Attempts for Rifaximin/HPMC-AS HG by Spray Drying
Description (a, b)Habit/DescriptionAnalysisResult (c)
(25:75) HPMC-AS HG solids light orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 137°C (Tg, midpoint); 0.4 J/g·°C (ACp)
(50:50) HPMC-AS HG solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 154 °C (Tg, midpoint); 0.4 J/g·°C (ΔCp)
(75:25) HPMC-AS HG solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 177 °C (Tg, midpoint); 0.3 J/g·°C (ΔCp)
(a): approximate ratio of Rifaximin to polymer, by weight;
(b): samples stored in freezer over desiccant after prepared.
Table 4. Solid Dispersion Attempts for Rifaximin/HPMC-AS MG by Spray Drying
Description (a, b)Habit/DescriptionAnalysisResult (c)
(25:75) HPMC-AS MG solids light orange; aggregates, irregular, no B/E XRPD x-ray amorph.
  mDSC 140 °C (Tg, midpoint); 0.4 J/g·°C (ΔCp)
(50:50) HPMC-AS MG solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
  mDSC 159 °C Tg, midpoint); 0.4 J/g·°C (ΔCp)
(75:25) HPMC-AS MG solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
  mDSC 177 °C(Tg, midpoint); 0.3 J/g·°C (ΔCp)
(a): approximate ratio of Rifaximin to polymer, by weight;
(b): samples stored in freezer over desiccant after prepared.
Table 5. Solid Dispersion Attempts for Rifaximin/Eudragit L100-55 (for reference) by Spray Drying
Description (a, b)Habit/DescriptionAnalysisResult (c)
(25:75) Eudragit L100-55 solids light orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 141°C (Tg, midpoint); 0.5 J/g·°C (ΔCp)
(50:50) Eudragit L100-55 solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 159°C (Tg, midpoint); 0.3 J/g·°C (ΔCp)
(75:25) Eudragit L100-55 solids orange; aggregates, irregular, no B/E XRPD x-ray amorph.
mDSC 176°C (Tg, midpoint); 0.2 J/g·°C (ΔCp)
(a): approximate ratio of Rifaximin to polymer, by weight;
(b): samples stored in freezer over desiccant after prepared.
Table 6. Physical Stability Assessment in 0.1N HCl at 37°C for Rifaximin and Rifaximin Dispersions Prepared in Methanol by Spray Drying
Description (a)Time (b)Habit/DescriptionAnalysisResults
(100:0) Rifaximin-only 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, no liquid left PLM agg., no B/E + a few B/E particles
clear view of B/E particles
24 hrs orange solids, solution cloudy PLM agg., no B/E + a few B/E particles
(25:75) PVP K-90* 0 - PLM agg., no B/E
agg., irr., no B/E
6 hrs orange solids, solution slightly yellow PLM agg., no B/E + B/E particles
clear view of B/E particles
24 hrs orange solids, solution slightly yellow PLM agg., no B/E + B/E particles
(50:50) PVP K-90* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, solution slightly yellow PLM agg., no B/E + a few B/E particles
clear view of B/E particles
24 hrs orange solids, small amount of liquid left PLM majority agg., no B/E + a few B/E particles
clear view of B/E particles
(75:25) PVP K-90* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, solution slightly yellow PLM agg., no B/E
agg., no B/E
24 hrs orange solids, small amount of liquid left PLM agg., no B/E
a few B/E particles in view field
(25:75) HPMC-P* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs light orange solids, liquid turbid PLM agg., no B/E
agg., no B/E
24 hrs orange solids, liquid turbid PLM agg., no B/E
agg., no B/E
(50:50) HPMC-P* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid turbid PLM agg., no B/E
agg., no B/E
24 hrs orange solids, solution cloudy PLM agg., no B/E
agg., no B/E
(75:25) HPMC-P* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid turbid PLM agg., no B/E + some B/E particles
clear view of B/E particles
24 hrs orange solids, small amount of liquid left PLM B/E particles observed
clear view of B/E particles
(25:75) HPMC-AS HG 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs light orange solids in cloudy liquid PLM no B/E observed
no B/E observed
24 hrs orange solids in cloudy solution PLM no B/E observed
no B/E observed
(50:50) HPMC-AS HG 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid cloudy PLM no B/E observed
no B/E observed
24 hrs orange solids in cloudy solution PLM no B/E observed
(75:25) HPMC-AS HG 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid turbid PLM no B/E observed
no B/E observed
24 hrs orange solids + cloudy solution PLM agg., no B/E
agg., no B/E
(25:75) HPMC-AS MG 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs light orange solids in cloudy liquid PLM no B/E observed
24 hrs orange solids in cloudy liquid PLM majority no B/E, a few B/E particles
B/E particles seems fiber-like, may due to foreign materials
(50:50) HPMC-AS MG 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid turbid PLM agg., no B/E + a few B/E particles seems due to foreign material
clear view of B/E particles
24 hrs orange solids in cloudy solution PLM no B/E observed
no B/E observed
(75:25) HPMC-AS MG 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid turbid PLM no B/E observed
no B/E observed
24 hrs orange solids in cloudy liquid PLM no B/E observed
agg., no B/E
(25:75) Eudragit L100-55* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs light orange solids in cloudy liquid PLM no B/E observed
24 hrs orange solids in cloudy solution PLM no B/E observed
(50:50) Eudragit L100-55* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids in cloudy liquid PLM no B/E observed except 2 particles
24 hrs orange solids in cloudy solurion PLM majority no B/E, a few B/E particles in center
clear view of B/E particles
(75:25) Eudragit L100-55* 0 - PLM agg., irr., no B/E
agg., irr., no B/E
6 hrs orange solids, liquid turbid PLM agg., no B/E
agg., no B/E
24 hrs orange solids in cloudy liquid PLM agg., no B/E
(a): approximate ratio of Rifaximin to polymer, by weight.
(b): time is cumulative and approximate; 100 µL of 0.1 N HCl solution added into samples at t = 0.
(c): 100 µL of 0.1 N HCl solution added into the sample after PLM analysis at 6 hrs.
*: for reference
Table 7. Physical Stability Assessment at 40 °C/75 % RH/ 7 d Condition for Rifaximin and Rifaximin Dispersions Prepared in Methanol by Spray Drying
Description (a)Habit/DescriptionAnalysisResults
(100:0) Rifaximin-only orange solids, dry PLM agg., irr., no B/E
(25:75) PVP K-90* dark yellow solids, dry PLM agg., irr., no B/E
(50:50) PVP K-90* orange solids, dry PLM a gg., irr., no B/E
(75:25) PVP K-90* orange solids, dry PLM agg., irr., no B/E
(25:75) HPMC-P* light orange solids, dry PLM agg., irr., no B/E
mDSC 148 °C (Tg, midpoint); 0.3 J/g·°C (ΔCp)
(50:50) HPMC-P* orange solids, dry PLM agg., irr., no B/E
(75:25) * HPMC-P* orange solids, dry PLM agg., irr., no B/E
(25:75) HPMC-AS HG light orange solids, dry PLM agg., irr., no B/E
(50:50) HPMC-AS HG orange solids, dry PLM agg., irr., no B/E
(75:25) HPMC-AS HG orange solids, dry PLM agg., irr., no B/E
mDSC 177 °C (Tg, midpoint); 0.5J/g·°C(ΔCp)
(25:75) HPMC-AS MG light orange solids, dry PLM agg., irr., no B/E
(50:50) HPMC-AS MG orange solids, dry PLM agg., irr., no B/E
(75:25) HPMC-AS MG orange solids, dry PLM agg., irr., no B/E
mDSC 152 °C (Tg, midpoint)
(25:75) Eudragit L100-55* light orange solids, dry PLM agg., irr., no B/E
mDSC 140 °C (Tg, midpoint); 0.5 J/g·°C (ΔCp)
(50:50) Eudragit L100-55* orange solids, dry PLM agg., irr., no B/E
(75:25) Eudragit L100-55* orange solids, dry PLM agg., irr., no B/E
(a): approximate ratio of Rifaximin to polymer, by weight.
(b): analysis treated as non-cGMP.
*: for reference
Table 8. Physical Stability Assessment at 60 °C/Dry/ 7 d Condition for Rifaximin and Rifaximin Dispersions Prepared in Methanol by Spray Drying
Description (a)Habit/DescriptionAnalysisResults
(100:0) Rifaximin-only orange solids PLM agg., irr., no B/E
(25:75) PVP K-90* orange solids PLM agg., irr., no B/E
(50:50)* PVP K-90* orange solids PLM agg., irr., no B/E
(75:25)* PVP K-90* orange solids PLM agg., irr., no B/E
(25:75) HPMC-P* light orange solids PLM aggirr., no B/E
(50:50) HPMC-P* orange solids PLM agg., irr., no B/E
(75:25) HPMC-P* orange solids PLM agg., irr., no B/E
(25:75) HPMC-AS HG light orange solids PLM agg., irr., no B/E
(50:50) HPMC-AS HG orange solids PLM agg., irr., no B/E
(75:25) HPMC-AS HG orange solids PLM agg., irr., no B/E
(25:75) HPMC-AS MG light orange solids PLM agg., irr., no B/E
(50:50) HPMC-AS MG orange solids PLM agg., irr., no B/E
(75:25) HPMC-AS MG orange solids PLM agg., irr., no B/E
(25:75) Eudragit L100-55* light orange solids PLM agg., irr., no B/E
(50:50) Eudragit L100-55* orange solids PLM agg., irr., no B/E
(75:25) Eudragit L100-55* orange solids PLM agg., irr., no B/E
(a): approximate ratio of Rifaximin to polymer, by weight.
*: for reference
Table 9. Parameters for Rifaximin Solid Dispersions by Spray Drying
Description (a)Inlet temp. (set, °C)Aspirator%Pump %Inlet temp. (measured, °C)Outlet temp. (measured, °C)Spray rate (b) mL/min
(50:50) HPMC-AS MG, ∼10g scale 120 95 40-30 120-119 60-45 9.6
(25:75) HPMC-P*, ∼10g scale 120 95 45-30 120-119 55-43 9.7
(a): approximate ratio of Rifaximin to polymer, by weight.
(b): flow rates are estimated at 30% pump.
*: for reference
Table 10. Characterizations of 50:50 (w/w) Rifaximin/HPMC-AS MG Dispersion by Spray Drying
AnalysisResults
XRPD x-ray amorphous
mDSC 154 °C (midpoint, Tg) 0.4 J/g·°C (ΔCp)
TG-IR 0.5 wt% (loss up to 100 °C)
199°C (onset, apparent decomp.)
water, methanol and unknown volatiles
Table 11. Characterizations of 25:75 (w/w) Rifaximin/HPMC-P Dispersion (for reference) by Spray Drying
AnalysisResults
XRPD x-ray amorphous
mDSC 152 °C (midpoint, Tg) 0.4 J/g·°C (ΔCp)
TG-IR 1.5 wt% (loss up to 100 °C)
178°C (onset, apparent decomp.)
water and methanol
Table 12. Sample Information of Rifaximin Dispersions for Dissolution Test in pH 6.52 FASSIF Buffer at 37 °C
Description (a)Sample IDDissolution Vessel NoSolids Weight (mg)Volume of Buffer (mL)
(50:50) HPMC-AS MG 4042-97-01 1 122.1 300
2 120.5
3 121.4
(25:75) HPMC-P* 4103-01-01 4 242.5 300
5 239.2
6 242.4
(a): approximate ratio of Rifaximin to polymer, by weight.
*: for reference
Table 13. Rifaximin Concentrations of 50:50 (w/w) Rifaximin/HPMC-AS MG Dispersion in pH 6.52 FASSIF Buffer at 37 °C
Dissolution Vessel NoTime (min.)Dilution (c)Absorbance (d)Concentration (µg/mL)
1 5 - 0.0159 0.34
10 - 0.0346 2.53
15 - 0.0569 5.13
30 - 0.09655 9.75
60 - 0.1626 17.46
90 - 0.2216 24.35
120 - 0.25625 28.39
1440 4 0.4093 184.99
2 5 2 0.02895 3.73
10 - 0.0304 2.04
15 - 0.04655 3.92
30 - 0.104 10.62
60 - 0.17755 19.21
90 - 0.248 27.43
120 - 0.3065 34.25
1440 4 0.3944 178.04
3 5 - 0.0107 -0.26
10 - 0.02555 1.47
15 - 0.03975 3.13
30 - 0.08735 8.68
60 - 0.1766 19.10
90 - 0.25815 28.61
120 - 0.32055 35.89
1440 4 0.4202 190.08
(c): certain samples were diluted before analyzed to avoid the possibility of falling outside the linearity range of the instrument.
(d): absorbance data less than 0.05 is below instrument detection limit and therefore concentration calculated from such absorbance is an approximate value.
Table 14. Rifaximin Concentrations of 25:75 (w/w) Rifaximin/HPMC-P Dispersion (for reference) in pH 6.52 FASSIF Buffer at 37 °C
Dissolution Vessel NoTime (min.)Dilution (d)Absorbance (e)Concentration (µg/mL)
4 5 - 0.01555 0.30
10 - 0.03395 2.45
15 - 0.0528 4.65
30 - 0.12235 12.77
60 - 0.2643 29.33
90 - 0.37355 42.08
120 - 0.455 51.58
1440 4 0.39465 178.16
5 5 - 0.0329 2.33
10 - 0.06805 6.43
15 - 0.07905 7.71
30 - 0.13745 14.53
60 - 0.242 26.73
90 - 0.32595 36.52
120 - 0.40555 45.81
1440 4 0.38525 173.77
6 5 - 0.0155 0.30
10 - 0.057 5.14
15 - 0.09415 9.47
30 - 0.17145 18.49
60 - 0.2724 30.27
90 - 0.36815 41.45
120 - 0.43155 48.84
1440 4 0.3838 173.09
(d): certain samples were diluted before analyzed to avoid the possibility of falling outside the linearity range of the instrument.
(e): absorbance data less than 0.05 is below instrument detection limit and therefore concentration calculated from such absorbance is an approximate value.
Table 15. Averaged Concentrations of 50:50 (w/w) Rifaximin/HPMC-AS MG Dispersions in pH 6.52 FASSIF Buffer at 37 °C
Description (a)Dissolution Vessel NoTime (min.)Concentration (µg/mL)Average Concentration (µg/mL)Standard Deviation
  1 5 0.34 1.27b 2.154
  2 3.73
  3 -0.26
  1 10 2.53 2.01b 0.5284
  2 2.04
  3 1.47
  1 15 5.13 4.06b 1.008
  2 3.92
  3 3.13
  1 30 9.75 9.69 0.970
  2 10.62
(50:50) HPMC-AS MG 3 8.68
1 60 17.46 18.59 0.977
  2 19.21
  3 19.10
  1 90 24.35 26.80 2.202
  2 27.43
  3 28.61
  1 120 28.39 32.85 3.945
  2 34.25
  3 35.89
  1 1440 184.99 184.37 6.0455
  2 178.04
  3 190.08
(a): approximate ratio of Rifaximin to polymer, by weight.
(b): absorbance data less than 0.05 is below instrument detection limit and therefore concentration calculated from such absorbance is an approximate value.
Table 16. Averaged Concentrations of 25:75 (w/w) Rifaximin/HPMC-P Dispersions (for reference) in pH 6.52 FASSIF Buffer at 37 °C
Description (a)Dissolution Vessel NoTime (min.)Concentration (µg/mL)Average Concentration (µg/mL)Standard Deviation
  4 5 0.30 0.98b 1.171
  5 2.33
  6 0.30
  4 10 2.45 4.67b 2.030
  5 6.43
  6 5.14
  4 15 4.65 7.28 2.442
  5 7.71
  6 9.47
  4 30 12.77 15.26 2.935
  5 14.53
(25:75) HPMC-P 6 18.49
4 60 29.33 28.78 1.840
  5 26.73
  6 30.27
  4 90 42.08 40.02 3.041
  5 36.52
  6 41.45
  4 120 51.58 48.75 2.886
  5 45.81
  6 48.84
  4 1440 178.16 175.01 2.749
  5 173.77
  6 173.09
(a): approximate ratio of Rifaximin to polymer, by weight.
(b): absorbance data less than 0.05 is below instrument detection limit and therefore concentration calculated from such absorbance is an approximate value.
Table 17. Analysis of Rifaximin Dispersions after Dissolution Test in pH 6.52 FASSIF Buffer at 37 °C
Description (a)Dissolution Vessel NoAnalysisResults
(50:50) HPMC-AS MG 1 PLM no B/E observed
change view field, no B/E
2 PLM no B/E observed
change view field, no B/E
3 PLM no B/E observed
majority no B/E, only 1 B/E particle in view field
(25:75) HPMC-P* 4 PLM B/E flakes and blades
5 PLM no B/E material + B/E flakes
6 PLM no B/E material + B/E flakes & blades
(a): approximate ratio of Rifaximin to polymer, by weight.
*: for reference

Abbreviations



[0139] 
TypeAbbreviationFull Name / Description
INSTRUMENTAL XRPD x-ray powder diffractometry
mDSC modulated differential scanning calorimetry
TG-IR thermogravimetric infrared
PLM polarized light microscopy
UV ultraviolet spectroscopy
POLYMER HPMC-AS hydroxypropylmethyl cellulose acetate succinate
HPMC-P hydroxypropylmethyl cellulose phthalate
Eudragit L100 anionic polymers with methacrylic acid as a functional group, dissolution at pH > 6.0
PVP K-90 polyvinylpyrrolidone, grade K-90
RESULTS Tg glass transition temperature
ΔCp heat of capacity change
amorph. amorphous
agg. aggregates
irr. irregular
decomp. decomposition
B birefringence
E extinction

Example 2. Ternary Dispersion of 50:50 (w/w) Rifaximin:HPMC-AS MG



[0140] A ternary dispersion of 50:50 (w/w) Rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127 was prepared in large quantity (containing approximately 110 g of Rifaximin) by spray drying. Disclosed herein are the analytical characterizations for Rifaximin ternary dispersion as-prepared and post-stress samples at 70 °C/75% RH for 1 week and 3 week, and post-stress sample at 40 °C/75% RH for 6 weeks and 12 weeks.

Characterization of Rifaximin Ternary Dispersion



[0141] Characterizations of the spray dried Rifaximin ternary dispersion (50:50 (w/w) rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127) are described in Table 18.
Table 18. Characterizations of Combined Rifaximin Ternary Dispersion Solids - Spray Drying
Sample IDAnalysisResults (b)
  XRPD x-ray amorphous
  mDSC 136 °C (midpoint, Tg)
  0.4 J/g·°C (ΔCp)
  TG-IR 0.7 wt%
  (loss up to 100 °C)
  202°C
  (onset, volatilization and apparent decomp.)
  methanol and possible acetic acid
4103-74-01a IR-ATR consistent with structure
  Raman consistent with structure
  SEM agglomerates of collapsed spheres
  PLM irregularly-shaped equant particles
  PSA d10 (µm): 3.627, d50 (µm): 8.233,
  d90 (µm): 17.530
  DVS 0.13 wt% (loss at 5%RH)
  11.14 wt% (gain, 5-95% RH)
  10.80 wt% (loss, 95-5% RH)
4074-89-01 (c) XRPD x-ray amorphous
(b): temperatures are round to the nearest degree; ΔCp is rounded to one decimal places and wt% is rounded to one decimal place.


[0142] A high resolution XRPD pattern was acquired and material is x-ray amorphous (Figure 46). By mDSC (Figure 47), a single apparent Tg is observed from the step change in the reversing heat flow signal at approximately 136 °C with a heat capacity change at Tg of approximately 0.4 J/g-°C.

[0143] Thermogravimetric analysis coupled with infra-red spectroscopy (TG-IR) was performed to analyze volatiles generated upon heating. The total weight loss of sample was approximately 0.7 wt% to 100 °C and the dramatic change in the slope occurs at approximately 202 °C (Figure 48). The Gram-Schmidt plot corresponds to the overall IR intensity associated with volatiles released by a sample upon heating at 20 °C/min. By Gram-Schmidt, a negligible increase of intensity upon heating is observed before ~ 7 minutes followed by a dramatic increase of intensity with the maximum at ~ 11.8 min. The waterfall plot (data not shown) of this sample indicates volatile are released upon heating after ~ 7 min (data is shown in Figure 49 using the linked IR spectrum at different time points as an example) and volatiles were identified as residual methanol from the processing solvent in spray drying and possible acetic acid from HPMC-AS MG.

[0144] Vibrational spectroscopy techniques, including IR and Raman were employed to further characterize this ternary dispersion. The overlay of IR spectra for the dispersion and X-ray amorphous Rifaximin is shown in Figure 50. Based on visual inspection, two spectra are very similar. Similar observations can be drawn from the comparison of Raman analysis (Figure 51). The sample is composed of agglomerates of collapsed spheres. Particles sizes of spheres are not uniform, ranging from slightly larger to much less than 10 µm.

[0145] PLM images (data not shown) of solids dispersed in mineral oil were collected, which indicate sample primarily is composed of irregularly-shaped equant particles approximately 5-15 µm in length with some agglomerates 20-50 µm in length. Particle size analysis (Figure 52) indicates that 50% of particles have size less than 8.233 µm and 90% of particles have size less than 17.530 µm. Data was acquired in 2% (w/v) Lecithin in Isopar G.

[0146] The DVS isotherm of solids is shown in Figure 53. The material exhibits a 0.13 wt% loss upon equilibration at 5% RH. Solids then gain 11.14 wt% between 5% and 95% RH and exhibits some hysteresis with 10.80 wt% loss upon desorption from 95% to 5% RH. XRPD analysis of the solids recovered after completion of the desorption step showed no evidence of sharp peaks indicative of a crystalline solid (Figure 54).

Physical Stability Assessment on Rifaximin Ternary Dispersion



[0147] An assessment of physical stability of this rifaximin ternary dispersion is currently in progress by exposing solids to varied elevated temperature/relative humidity conditions, including 25°C/ 60%RH, 40°C/ 75%RH and 70°C/ 75%RH for extended period of time. At designated time interval, such as at 1 week, 3 week, 6 week, and 12 weeks, selected samples were removed from stress conditions for characterization.

[0148] Table 19 summarized characterization results for the samples that stressed at 70°C/ 75%RH condition 1 week and 3 weeks, and the sample that stressed at 40°C/ 75%RH condition 6 weeks.
Table 19. Physical Stability Evaluation on Rifaximin Ternary Dispersion
ConditionTimeHabit/DescriptionAnalysisResults (a)
70 °C/75% RH 1 week orange solids, aggregates, no B/E XRPD x-ray amorphous
mDSC 134 °C(midpoint, Tg)
  0.4 J/g·°C (ΔCp)
SEM agglomerates of collapsed spheres
KF 3.80%
70 °C/75% RH 3 weeks dark orange solids, aggregates, no B/E XRPD x-ray amorphous
mDSC 134 °C (midpoint, Tg)
  0.4 J/g·°C (ΔCp)
SEM agglomerates of collapsed spheres
KF 3.19%
40 °C/75% RH 6 weeks orange solids, aggregates, no B/E XRPD x-ray amorphous
mDSC 133 °C (midpoint, Tg)
  0.4 J/g.°C (ΔCp)
SEM agglomerates of collapsed spheres
KF 4.05%
40 °C/75% RH 12 weeks orange solids, aggregates, no B/E XRPD x-ray amorphous
mDSC 132 °C (midpoint, Tg)
  0.5 J/g·°C (ΔCp)
SEM agglomerates of collapsed spheres
KF 3.37%
(a): temperatures are round to the nearest degree; ΔCp is rounded to one decimal places.


[0149] For a sample that was stressed at 70°C/ 75%RH for 1 week, solids are still x-ray amorphous according to XRPD (Figure 55). A single Tg at approximately 134 °C was observed from the apparent step change in the reversing heat flow signal in mDSC with the change of heat capacity 0.4 J/ g °C, indicating the components of each dispersion remained intimately miscible after stress (Figure 56). A non-reversible endotherm was observed at approximately 54°C which is likely due to the residual solvent from spray drying and moisture that materials absorbed during stress, which is confirmed by KF analysis that sample contains 3.80 wt% of water (KF analysis for Rifaximin ternary dispersion after 70 °C/75% RH 1week; 1.2855 g - R1=3.72 and .988 g - R1= 3.87%). The sample is composed of agglomerates of collapsed spheres and particles sizes of spheres are not uniform, which is similar to the as-prepared material.

[0150] For the sample that was stressed at 70°C/ 75%RH for 3 weeks, although the color of the material appeared to be darker than the 1-week sample, characterization results for 3-week sample are similar to that for 1-week sample. Solids are also x-ray amorphous by XRPD (Figure 55) and display a single Tg at approximately 134 °C by mDSC (Figure 57). KF analysis indicates it contains 3.19 wt% of water (KF analysis for rifaximin ternary dispersion after 70 °C/75% RH 3weeks; 1.2254g - R1 = 3.45 and 1.1313g - R1 = 2.93). By SEM (data not shown), the material has morphology similar to the as-prepared dispersion and 1-week stress sample, which is composed of agglomerates of collapsed spheres and particles sizes of spheres are not uniform.

[0151] For the sample that was stressed at 40°C/ 75%RH for 6 weeks, solids are still x-ray amorphous according to XRPD (Figure 55). It has a single Tg at approximately 133 °C by mDSC with the change of heat capacity 0.4 J/ g °C (Figure 58). It contains 4.05 wt% of water by KF (KF analysis for rifaximin ternary dispersion after 40 °C/75% RH 6 weeks; 1.0947g - R1 = 3.47 and 1.2030 - R1= 4.63). By SEM (data not shown), the sample is composed of agglomerates of collapsed spheres and particles sizes of spheres are not uniform, which is similar to the as-prepared material.

[0152] For the sample that was stressed at 40°C/ 75%RH for 12 weeks, solids are x-ray amorphous (Figure 55) and display a single Tg at approximately 132°C with the change of heat capacity 0.5 J/ g °C (Figure 59). It contains 3.37 wt% of water by KF (KF analysis for Rifaximin ternary dispersion after 40 °C/75% RH 12 weeks; 1.3687 g - R1= 3.06 and 1.1630 g - R1= 3.67). SEM analysis (data not shown) indicates that the sample is composed of agglomerates of collapsed spheres and particles sizes of spheres are not uniform, which is similar to the as-prepared material.

Example 3. Rifaximin Solid Dispersion Composition and Procedures


Rifaximin Ternary Dispersion Ingredients:



[0153] Rifaximin ternary dispersions (50:50 w/w Rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127) were prepared from methanol using spray drying in closed mode suitable for processing organic solvents. Ingredients are listed as below in Table 20:
Table 20. Components of Rifaximin Solid Dispersion
Componentmg/gPurpose
Rifaximin 472 active pharmaceutical ingredient
Hydroxypropylmethyl cellulose acetate succinate (HPMC-AS), Type MG 472 stabilizing agent
Pluronic F-127 56 wetting agent
Methanol -- volatile; removed during process

Spray Drying Procedures:



[0154] Rifaximin ternary dispersions were prepared by spray drying in both small scale (∼1 g API) and large scale (≥ 34 g API in a single batch).

[0155] For the small-scale sample, rifaximin and then the methanol were added to a flask. The mixture was stirred at ambient temperature for ~ 5 min to give a clear solution. HPMC-AS MG and Pluronic F-127 were added in succession and the sample was stirred for ∼ 1hr. An orange solution was obtained.

[0156] For large-scale samples, a solution was prepared at ∼40 °C. Rifaximin and then methanol were added to a flask and the mixture was stirred at ∼40°C for - 5min until clear. HPMC-AS MG, and then Pluronic F-127 were added into the rifaximin solution under stirring at ∼40 °C. The sample continued to stir for - 1.5 hr to 2 hr at this temperature. A dark red solution was obtained. The sample was removed from the hot plate and left at ambient to cool.

[0157] Experimental conditions to prepare Rifaximin ternary solutions are summarized in Table 21 below:
Table 21. Experimental Conditions to Prepare Rifaximin Ternary Solutions
Solventweight (API/HPMC AS MG/Pluronic F127, g)TemperatureConcentration (g/L)
methanol, 100 mL 1.0535/1.0529/0.1249 ambient 22.3
methanol, 1000 mL 34.07/34.07/4.02 ~ 40 °C 72.2
methanol, 1250 mL 50.34/50.32/5.94 ~ 40°C 85.3
methanol, 1250 mL 50.16/50.14/5.92 ∼ 40°C 85
methanol, 1250 mL 50.05/50.06/5.91 ∼ 40°C 85


[0158] During the spray drying process, both the small and large scale rifaximin ternary solutions were kept at ambient temperature. The pump % was decreased during the process in an attempt to control outlet temperature above 40°C. The operating parameters used for processing are presented in Table 22 below.
Table 22. Operating Parameters Used For Processing Rifaximin SD
Description (a)Inlet temp. (set, °C)Aspirator %Pump %Inlet temp. (measured, °C)Outlet temp. (measured, °C)Spray rate (b) mL/min
50:50 Rifaximin:HPM C-AS MG 5.9 wt% Pluronic F-127 120 95 35 120 60-55 10.4
120 95 65-30 120-119 61-42 23
120 95 50-30 120-119 67-43 16
120 95 50-30 120-119 65-43 16
120 95 50-30 120-119 67-43 16
(a): 50:50 is approximate ratio of Rifaximin to polymer, by weight; 5.9 wt% Pluronic is weight fraction to 50:50 rifaximin:HPMC-AS MG dispersion.
(b): Flow rates are estimated. Flow rate for 4103-41-01 was measured at pump 35%; for 4103-56-01 was measured at pump 65%, while for others were measured at pump 50%.


[0159] Solids recovered after spray drying were dried at 40 °C under vacuum for 24 hours and then stored at sub-ambient temperatures over desiccant.

[0160] Spray Drying Process Parameters:
  • Spray Dryer - PSD 1
  • Two Fluid Niro Nozzle
  • Nozzle orifice - 1mm
  • Inlet gas temperature - 125±5 deg C
  • Process gas flow (mmH2O) - 44
  • Atomizing gas pressure - 0.7 - 1 bar
  • Feed rate - 4.7 kg/Hr
  • Outlet temperature - 55± 3 deg C
  • Solution temperature - 36 deg C
  • Post spray drying vacuum dry at 40 deg C for 48 hrs

Example 4.



[0161] Exemplary formulations for micronized, API, amorphous, solid dispersion and micronized capsules are below in Table 23. These capsules were used in the dog study of Example 5.
Table 23. Capsule Formulation composition (Solid Dispersion (SD) Capsules)
IngredientsMicronized CapsulesAPI CapsulesAmorphous CapsulesSD CapsulesMicronized Tablets
 %g/dose%g/dose%g/dose%g/dose%g/dose
Rifaximin 95.5 2.2 47.2 2.2 51.7 2.2 42.47 2.2 50 2.2
Ac-di-sol 4.5 0.1 5 0.23 5 0.21 10.02 0.52 7.5 0.33
Mannitol 160C     47.8 2.23 43.3 1.84        
Pluronic 188             5.04 0.26    
HPMC AS             42.47 2.2    
Avicel 113                 26 1.14
Avicel 112                 15 0.66
Magnesium Stearate                 1 0.04
Cab-o-sil                 0.5 0.02
Avicel CL-611                    
Mannitol 160C                    
Total 100 2.3 100 4.66 100 4.26 100 5.18 100 4.4
Table 24. Manufacture of rifaximin/HPMC-AS /Pluronic 275mg Capsules
Component% Formulamg/capsTheo. Qty (g)Actual Qty (g)
Rifaximin 42.47 275 113.7 113.7
HPMC-AS (type MG) 42.47 275 113.7 113.7
Pluronic F-127 5.04 32.63 13.49 13.49
Sodium Croscarmellose 10.02 64.87 26.82 26.82
Hard Gelatin Capsule (size 000) Clear 1 N/A 300 300
Total 100 647.5 267.7 g  

Blending/Encapsulation Procedure:



[0162] To form the capsules sodium croscarmellose was added to the bag of SD rifaximin dispersion and bag blend for 1 minute, and then the material was added to the V-blender and blended for 10 minutes at 24 rpm.

[0163] The material was then discharged into a stainless steel pan and record the height of material in the pan. Empty capsules were tared using an analytical balance, then the capsules were filled by depressing into the bed of material. The weight is adjusted within + or - 5% of target fill weight of 647.5mg (acceptable fill range 615.13 - 679.88 mg).

[0164] Figures 61 - 63 show the rifaximin solid dispersion (SD) capsules in various buffers; with and without SDS; and compared to amorphous rifaximin. Figure 61 shows results of dissolution studies of rifaximin SD capsules in acid phase: 0.1 N HC1 with variable exposure times in a buffer containing 0.45% SDS at pH 6.8. Figure 62 shows results of dissolution studies of rifaximin SD capsules in acid phase for 2 hours buffered at pH 6.8 with and without SDS. Figure 63 shows results of dissolution studies of rifaximin SD capsules in acid phase in a phosphate buffer at pH 6.8 with 0.45% SDS compared to amorphous rifaximin. As shown in the Figures 61 - 63 rifaximin SD near 100% dissolution is achieved in 0.45% SDS and the SD formulation dissolves more slowly than the amorphous rifaximin.

Example 5. Pharmacokinetic (PK) studies of solid dispersion in capsules



[0165] Presented herein are dog pharmacokinetics (PK) studies comparing various forms of rifaximin. PK following administration of rifaximin API in capsule, micronized API in capsule, nanocrystal API in capsule (containing surfactant), amorphous in capsule, and solid dispersion (SD) in capsule were tested.

[0166] In the SD dosage form, the polymer used was HPMC-AS at a drug to polymer ratio of 50:50. The formulation also comprised pluronic F127 and crosscarmellose sodium (see Example 4).

[0167] A brief study design: male beagle dogs (N=6, approximately 10 kg) received rifaximin 2200 mg in the dosage forms described above as a single dose (capsules, 275 mg, 8 capsules administered in rapid succession), in a cross-over design with one week washout between phases. Blood was collected at timed intervals for 24 h after dosage administration, and plasma was harvested for LC-MS/MS analysis. The mean concentrations are shown in Figure 60.

[0168] Table 25 shows the PK parameters. From the table it can be seen that systemic exposure of the solid dispersion formulation is greater than that of amorphous or crystalline form (API) of rifaximin.
Table 25. PK Parameters of API, Amorphous and Solid Dispersion to Dogs
IDHalf-life*TmaxCmaxAUClastAUCINF_obsAUC_0-24
 hhng/mLh*ng/mLh*ng/mLh*ng/mL
             
901_API 16.76 0.5 65.5 101 118 101
902_API 9.41 1 3.83 25 29 25
903_API 10.03 1 197 344 360 344
904_API 3.56 1 1.21 5 6 6
905_API 2.94 1 1.53 5 6 6
906_API   24 0.52 7   7
mean 6.98 1 44.93 81 104 82
SD   [0.5-24] 78.75 134 150 134
             
901_amorph 5.38 1 536 1407 1421 1407
902_amorph 5.93 2 4100 12258 12762 12258
903_amorph 6.25 2 1050 3375 3523 3375
904_amorph 4.77 2 763 2291 2306 2291
905_amorph 7.72 1 1200 2041 2059 2041
906_amorph 5.63 2 704 2076 2090 2076
mean 5.88 2 1392.17 3908 4027 3908
SD   [1-2] 1348.24 4141 4334 4141
             
901_SD amorph 6.66 2 491 1354 1394 1354
902_SD amorph 2.04 2 6550 25140 25149 25140
903_SD amorph 2.8 4 2410 10490 10508 10490
904_SD amorph 2.24 1 1410 6343 6350 6343
905_SD amorph 3.97 2 2860 7885 7895 7885
906_SD amorph 4.89 2 1900 4532 4558 4532
mean 3.01 2 3026 10878 10892 10878
SD   [1-4] 2043.58 8267 8264 8267
*geometric mean **median
and range


[0169] API exposures were low, in keeping with what has been previously observed for rifaximin. In contrast, mean exposures (AUCinf) following amorphous and SD rifaximin administration were substantially higher, with ∼40-and ∼100-fold greater exposure, respectively, as compared with API. Variability was high in all three dose groups. In general, the shapes of all three profiles were similar, suggesting effects of the dosage forms on bioavailability without effects on clearance or volume of distribution.

Example 6. Human Clinical Studies



[0170] Rifaximin SDD with 10% CS formulation was used in human clinical studies. Figure 65 shows the kinetic solubility of rifaximin SD granules 10% wt CS FaSSIF or 10% wt CS FeSSIF (a) and the dissolution profiles of SDD tablet 10% CS in 0.2% SLS at pH 4.5, 5.5 and 7.4. As shown in the Figure 65, rifaximin SDD 100%, or near 100%, dissolution is achieved in 0.2% SLS, pH 4.5, 5.5 and 7.4. Figure 66 shows that release can be delayed up to two hours and extended up to three hours.

Example 7. Effects of Media pH on Dissolution



[0171] Figures 67 - 70 show the effects of media pH on Rifaximin SDD tablet SDD tablet dissolution at various levels of CS: 0%, 2.5%,5%, and 10% CS. Figures 67 and 68 show dissolution profiles of SDD tablet with 0%, 2.5%, 5% or 10% CS in 0.2%SDS at 2 hours pH 2.0, pH 4.5, 0.2% SDS pH 5.5, or 0.2% SDS, pH 7.4. Figures 69 and 70 show the dissolution profiles of SDD tablet 2.5% CS, 0% CS, 10% CS and 5% CS in 0.2% SLS, pH4.5, 0.2% SLS, pH 5.5 and 0.2% SLS, pH 7.4. Figure 71 shows CS release mechanism.

Example 8.



[0172] Described herein are the preparation and characterization of rifaximin quaternary dispersions with antioxidants. Antioxidants used were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG).

Sample preparation and Characterization



[0173] Three rifaximin quaternary samples were prepared by spray drying from methanol. Spray drying parameters are summarized in Table 26. Table 2 Parameters for Samples Prepared by Spray Drying
Table 26
Sample IDInlet temp. (set, °C)Aspirator %Pump %Inlet temp. (measured , °C)Outlet temp. (measured, °C)Spray rate (a) mL/min
0.063 wt% of BHA in the dispersion 120 95 45-35 120-124 61-49 19
0.063 wt% of BHT in the dispersion 120 95 45-35 120-121 60-50 20
0.094 wt% of propyl gallate in the dispersion 120 95 45-35 119-120 60-48 20
(a): flow rates are estimated based on initial pump% of 45%.
Table 27 Characterization of Rifaximin Quaternary Samples
Habit/DescriptionAnalysisResults (b)
orange solids, irregular aggregates, no B/E XRPD x-ray amorphous
mDSC 133 °C (midpoint, Tg)
0.3 J/g·°C (ΔCp)
orange solids, irregular aggregates, no B/E XRPD x-ray amorphous
mDSC 133 °C (midpoint, Tg)
0.4 J/g·°C (ΔCp)
orange solids, irregular aggregates, no B/E XRPD x-ray amorphous
mDSC 134 °C (midpoint, Tg)
0.4 J/g·°C (ΔCp)


[0174] A small sub-lot from each of spray dried materials was visually inspected by PLM and then characterized by XRPD and mDSC. Characterization results are summarized in Table 27.
The prepared materials are x-ray amorphous, as shown in Figure 72 the overlay of XRPD patterns, which agree with their PLM observations.

[0175] In the mDSC, each of material displays a single apparent Tg in the reversing heat flow signal at approximately 133 °C (Figure 73, with 0.063 wt% BHA), 133 °C (Figure 74, with 0.063 wt% BHT), and 134 °C (Figure 75, with 0.094 wt% PG), which is consistent with the Tg of the spray dried rifaximin ternary dispersion of 47.2:47.2:5.6 w/w/w/ rifaximin/HPMC-AS MG/Pluronic F-127 (135 or 136 °C).

Example 9: Rifaximin Solid Dispersions



[0176] This example sets forth exemplary microgranules of rifaximin and pharmaceutical compositions comprising the same.

[0177] Spray dry dispersion (SDD), solid dispersion, amorphous solid dispersion are used interchangabley herein to refer to the rifaximin formulations.

[0178] The complete statement of the components and quantitative composition of Rifaximin Solid Dispersion Formulation (Intermediate) is given in Table 28
Table 28: Composition of Rifaximin Solid Dispersion Formulation
ComponentQuantity (%)Function
Rifaximin Drug Substance 42.48 Active Ingredient
Hypromellose Acetate Succinate (HPMC-AS) 42.48 Solubility Enhancer
Poloxamer 407 5.04 Surfactant
Croscarmellose Sodium 10.00 Dissolution Enhancer

Composition of Rifaximin solid dispersion IR capsule



[0179] 
Table 29: Composition of Rifaximin solid dispersion IR capsule
ComponentQuantityFunction
Rifaximin solid dispersion (amorphous) 75mg-275mg* Active ingredient
Hard Gelatin capsules Coni-Snap, Size 000, Transparent 1 unit Capsule
*Rifaximin dose equivalent

Description of Manufacturing Process and Process Controls


Manufacturing Process for Rifaximin Solid Dispersion Formulation



[0180] Table 30 sets forth the manufacture of Rifaximin solid dispersion microgranules


Manufacturing Process for Rifaximin solid dispersion IR capsules



[0181] The manufacturing process the Rifaximin solid dispersion IR capsules is given in Table 31.



[0182] Exemplary spary drying processes are set forth in Table 32.
Table 32: Spray Drying Process:
• Spray Dryer - PSD 1
• Two Fluid Niro Nozzle
• Nozzle orifice - 1mm
• Inlet gas temperature - 125±3 deg C
• Process gas flow (mmH2O) - 44
• Atomizing gas pressure - 1 bar
• Feed rate - 4.7 kg/Hr
• Outlet temperature - 55± 3 deg C
• Solution temperature - 36 deg C
• Post spray drying vacuum dry at 40 deg C for 48 hrs
IngredientsMicronized CapsAPI CapsAmorphous CapsAmorphous SD capsMicronized Tab
 %g/dose%g/dose%g/dose%g/do se%g/dose
Rifaximin 95.5 2.2 47.2 2.2 51.7 2.2 42.47 2.2 50 2.2
Ac-di-sol 4.5 0.1 5 0.23 5 0.21 10.02 0.52 7.5 0.33
Mannitol 160C     47.8 2.23 43.3 1.84        
Pluronic 188             5.04 0.26    
HPMC AS             42.47 2.2    
Avicel 113                 26 1.14
Avicel 112                 15 0.66
Magnesium Stearate                 1 0.04
Cab-o-sil                 0.5 0.02
Avicel CL-611                    
Mannitol 160C                    
Total 100 2.3 100 4.66 100 4.26 100 5.18 100 4.4

Example 10: Characterization of Drug Product Samples Containing Rifaximin Solid Dispersion



[0183] Disclosed herein is dissolution data for roller compacted materials of Solid Dispersion Rifaximin with varying levels (0, 2.5%, 5%, and 10%) of croscarmellose sodium.

[0184] Three roller compacted material of Amorphous Solid Dispersion Rifaximin with varying levels (0, 2.5%, 5%) of croscarmellose sodium were dissolution tested. Results are compared to dissolution of the rifaximin granules with 10% croscarmellose sodium.

Dissolution Studies with USP Paddle Method



[0185] Dissolution tests were performed on as received roller compacted materials of Solid Dispersion Rifaximin with 0, 2.5 wt%, and 5 wt% croscarmellose sodium. Powders of solids were directly added into pH 6.5 FaSSIF buffer with gentle agitation of the media (50 rpm paddle stirrer) at 37 °C for 24 hrs.

[0186] At designated time points of 5, 10, 20, 30, 60, 90, 120, 240 and 1440 minutes, aliquots were removed from each of the samples. Analysis of the date indicates that an increase in rifaximin concentration is apparent with the rising croscarmellose sodium level in materials, particularly in the early stage of the dissolution. After 24 hrs, the rifaximin concentration from granules containing 5 wt% croscarmellose sodium is similar to granules with 10 wt% croscarmellose sodium.

Example 11: Characterization of Rifaximin Solid Dispersion Powder 42.48% w/w



[0187] Described herein is the characterization of Rifaximin Solid Dispersion Powder 42.48% w/w. Dissolution testing was also performed on the material at pH 6.5 in FaSSIF at 37 °C.

[0188] A sample of rifaximin ternary dispersion was characterized by XRPD, mDSC, TG-IR, SEM and KF.

[0189] X-ray powder diffraction (XRPD) analysis using a method for Rifaximin Solid Dispersion Powder 42.48% w/w was conducted. The XRPD pattern by visual inspection is x-ray amorphous with no sharp peaks (Figure 76). By mDSC a single apparent Tg is observed from the step change in the reversing heat flow signal at approximately 134 °C with a heat capacity change at Tg of approximately 0.36 J/g·°C.

[0190] Thermogravimetric analysis coupled with infra-red spectroscopy (TG-IR) was performed to analyze volatiles generated upon heating. The total weight loss of sample was approximately 0.4 wt% to 100 °C, and a dramatic change in the slope occurs at approximately 190 °C which is likely due to decomposition. The Gram-Schmidt plot corresponds to the overall IR intensity associated with volatiles released by a sample upon heating at 20 °C/min. Gram-Schmidt indicates that volatiles are released upon heating after ∼ 8min, and volatiles were identified as residual methanol from the processing solvent in spray drying and possible acetic acid from HPMC-AS MG.

[0191] KF analysis indicates that the material contains 1.07 wt% water [(1.00 + 1.13)/2 = 1.07%].

Example 12: Methods for Spray drying Rifaximin ternary dispersion (50:50 w/w Rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127).



[0192] Provided herein are procedures to spray dry Rifaximin ternary dispersion (50:50 w/w Rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127).

[0193] Rifaximin ternary dispersions (50:50 w/w Rifaximin:HPMC-AS MG with 5.9 wt% Pluronic F-127) were prepared from methanol using Büchi B-290 Mini Spray Dryer in closed mode suitable for processing organic solvents. Ingredients are listed in Table 33 below:
Table 33
No.Componentmg/gPurpose
1 Rifaximin 472 active pharmaceutical ingredient
2 Hydroxypropylmethyl cellulose acetate succinate (HPMC-AS), Type MG 472 stabilizing agent
3 Pluronic F-127 56 wetting agent
4 Methanol -- volatile; removed during process


[0194] Rifaximin ternary dispersions were prepared by spray drying in both small scale (∼1 g API) and large scale (≥ 34 g API in a single batch).

[0195] For a small-scale sample, rifaximin and then the methanol were added into a clean flask. The mixture was stirred at ambient for ∼ 5 min to give a clear solution. HPMC-AS MG and Pluronic F-127 were added in succession and the sample was stirred for ∼ 1hr. An orange solution was obtained.

[0196] For a large-scale sample, a solution was prepared at ∼40 °C. Rifaximin and then methanol were added to a clean flask and the mixture was stirred at ∼40 °C for - 5min until clear. HPMC-AS MG, and then Pluronic F-127 were added into the rifaximin solution under stirring at ∼40 °C. The sample continued to stir for - 1.5 hr to 2 hr at this temperature. A dark red solution was obtained. The sample was removed from the hot plate and left at ambient to cool.

[0197] Experimental conditions to prepare Rifaximin ternary solutions are summarized in Table 34 below:
Table 34
Solventweight (API/HPMC AS MG/Pluronic F127, g)TemperatureConcentration (g/L)
methanol, 100 mL 1.0535/1.0529/0.1249 ambient 22.3
methanol, 1000 mL 34.07/34.07/4.02 ∼ 40 °C 72.2
methanol, 1250 mL 50.34/50.32/5.94 ∼ 40°C 85.3
methanol, 1250 mL 50.16/50.14/5.92 ∼ 40 °C 85.0
methanol, 1250 mL 50.05/50.06/5.91 ∼ 40 °C 85.0


[0198] During spray drying process, both the small and large scale rifaximin ternary solutions were kept at ambient temperature. The Pump% was decreased during process in attempt to control outlet temperature above 40 °C. The operating parameters used for processing are presented in Table 35 below.
Table 35:
Description (a)Inlet temp. (set, °C)Aspirator%Pump %Inlet temp. (measured, °C)Outlet temp. (measured, °C)Spray rate (b) mL/min
50:50 Rifaximir:HPMC-AS MG 5.9 wt% Pluronic F-127 120 95 35 120 60-55 10.4
120 95 65-30 120-119 61-42 23
120 95 50-30 120-119 67-43 16
120 95 50-30 120-119 65-43 16
120 95 50-30 120-119 67-43 16
(a): 50:50 is approximate ratio of Rifaximin to polymer, by weight; 5.9 wt% Pluronic is weight fraction to 50:50 Rifaximin:HPMC-AS MG dispersion.
(b): flow rates are estimated. Flow rate for 4103-41-01 was measured at pump 35%; for 4103-56-01 was measured at pump 65%, while for others were measured at pump 50%.


[0199] Solids recovered after spray drying were dried at 40 °C under vacuum for 24 hours and then stored at sub-ambient (freezer) over desiccant.

Example 13. Non-clinical Data- form/ formulation comparison and dose ranging in dogs



[0200] Described herein is non-clinical data, form/formulation comparison in dogs and SDD dose ranging in dogs. Figure 77 indicates the results of two studies conducted to characterize the pharmacokinetics of rifaximin following administration of varying forms and formulations following a single oral dose. Blood samples were collected at timed intervals over the 24 h after single dose administration (2200 mg total dose in each case) and processed to plasma for analysis of rifaximin concentrations. PK parameters were estimated by noncompartmental methods. The results are shown in Figure 77. Of the forms/formulations shown, the spray-dried dispersion showed that the highest exposure, and therefore the highest bioavailability, resulted from administration of the SDD formulaton (dosed as SDD powder in gelatin capsules). In order of decreasing exposure among forms dosed in gelatin capsule formulation, SDD > amorphous > iota > micronzed > eta>current crystalline API. Lower in systemic exposure than all of those are the micronized suspension formulation (reconstituted powder for oral suspension) and the current 550 mg Xifaxan tablet. Table 36, below, shows Pk parameters for dog forms.
Table 36
HL_Lambda_zTmaxCmaxAUCallAUCINF_obs 
 hhng/mLhng/mLhng/mL
Eta 9.70 1.5 162.28 434.14 608.14
Iota 6.56 2 276.50 718.23 739.94
Amorphous 5.82 2 1392.17 3907.84 4026.86
API capsules 5.64 1 44.93 81.20 103.83
SDD 3.16 2 2603.50 9290.71 9308.83
Micronized capsules 8.10 1 473.43 894.65 905.97
Micronized suspension 5.22 3 0.68 5.11 8.41
Micronized tablets 4.77 5 0.83 6.81 10.20
Nanocrystal capsules 5.01 5 0.99 9.05 8.70


[0201] Figure 78 shows the results of the dog dose escalation, in which dogs received single doses of the SDD formulation in capsules, at doses from 150 mg to 2200 mg. The results indicate an essentially linear dose escalation (increases in exposure that are approximately proportional to increase in dose) up to 550 mg, followed by a greater-than-proportional increase at 1100 mg and 2200 mg. This is quite unusual in the linear range in that the current crystalline form of rifaxmin does not dose escalate, generally, exposure does not increase substantially on increasing dose. The greater than dose proportional increase on increasing dose is also remarkable and suggests that, at the higher doses, rifaximin is saturating intestinal P-glycoprotein transport that would otherwise limit systemic absorption, thereby allowing increased absorption.

Example 14. Human studies



[0202] Described herein are clinical studies carried in ten male human subjects. Figure 79 sets out the quotient study design for rifaximin SDD dose escalation. Figure 80 outlines the dose escalation/ regional absorption study, dose escalation/ dose selection. Figures 81 and 82 show representative subject data from an exemplary dose escalation study. Mean data (linear scale and log scale) is shown in Figures 83 and 84, respectively. Mean profiles, log scale. Terminal phases are parallel, in clearance mechanisms. A summary of rifaximin SDD dose escalation is shown indicating that it is likely that there is not saturation of any metabolic or other systemic Figure 85. To summarize, there are roughly dose proportional increases in exposure (Cmax and AUC) with increases in dose, as shown by Cmax multiple and AUC multiple columns. Tmax is not delayed by dose increases, further indicating an early absorption window (corroborated by regional absorption data). The percent of dose in urine is remarkable in that it stays low, approximately 0.2% or less of the dose excreted over 24 h. This result is surprising in that this is quite low in spite of the significant increases in systemic exposure as compared with the crystalline formulation. Taken together, the results indicate a considerably increased solubility that presumably leads to increased local/lumenal soluble rifaximin, with accompanying increases in systemic exposure, but without significant increases in urinary excretion that are reflective of percent of rifaximin dose absorbed.

[0203] Dose/ dosage form comparisons are shown in Figures 86 and 87. The tables compare SDD at increasing doses to the current crystalline formulation in terms of systemic PK. As noted in Figure 87, as compared to the PK of rifaximin from the current formulation, the SDD formulation at the same dose shows an approximate 6.4-fold increase in Cmax and an approximate 8.9-fold increase in AUC. Nonetheless, these exposures are less than those observed in any hepatic impaired subject with the current tablet formulation.

Example 15. Exemplary Tablet Formulations



[0204] According to certain exemplary embodiments, microgranules, blends and tablets are formulated as set forth in Table 37, below




Claims

1. A solid dispersion form of rifaximin comprising rifaximin and a polymer selected from: hydroxypropyl methylcellulose acetate succinate (HPMC-AS) grade HG and grade MG, wherein the rifaximin:polymer weight ratio ranges from 10:90 to 90:10.
 
2. The solid dispersion form of rifaximin of claim 1, further comprising a poloxamer.
 
3. The solid dispersion form of rifaximin of claim 2, wherein the polaxamer comprises poloxamer 407 or Pluronic F-127.
 
4. The solid dispersion form of rifaximin of claim 1, wherein the rifaximin:polymer weight ratio ranges from 15:85 to 85:15.
 
5. The solid dispersion form of rifaximin of claim 4, wherein the rifaximin:polymer weight ratio ranges from 25:75 to 75:25.
 
6. The solid dispersion form of rifaximin of claim 5, wherein the rifaximin:polymer weight ratio ranges from 40:60 to 60:40.
 
7. The solid dispersion form of rifaximin of claim 1, wherein the rifaximin:polymer weight ratio is 50:50.
 
8. The solid dispersion form of rifaximin according to claim 1, wherein the solid dispersion form of rifaximin is characterized by an XRPD according to one or more of Figures 12, 17, and 31.
 
9. The solid dispersion form of rifaximin according to claim 1, wherein the solid dispersion form of rifaximin is characterized by a Thermogram according to Figures 13-16, 18-21, 28, 29, and 32.
 
10. A microgranule comprising the solid dispersion form of rifaximin of any one of claims 1-9.
 
11. A pharmaceutical composition comprising the solid dispersion form of rifaximin of any one of claims 1-9 and at least one pharmaceutically acceptable excipient.
 
12. The solid dispersion form of rifaximin of any one of claims 1-9 for use in treating, preventing, or alleviating bowel related disorders.
 


Ansprüche

1. Feste Dispersionsform von Rifaximin, umfassend Rifaximin und ein Polymer, ausgewählt aus Hydroxypropylmethylcelluloseacetatsuccinat (HPMC-AS), Qualität HG und Qualität MG, wobei das Rifaximin:Polymer-Gewichtsverhältnis im Bereich von 10:90 bis 90:10 liegt.
 
2. Feste Dispersionsform von Rifaximin gemäß Anspruch 1, die außerdem ein Poloxamer umfasst.
 
3. Feste Dispersionsform von Rifaximin gemäß Anspruch 2, wobei das Polaxamer Polaxamer 407 oder Pluronic F-127 umfasst.
 
4. Feste Dispersionsform von Rifaximin gemäß Anspruch 1, wobei das Rifaximin:Polymer-Gewichtsverhältnis im Bereich von 15:85 bis 85:15 liegt.
 
5. Feste Dispersionsform von Rifaximin gemäß Anspruch 4, wobei das Rifaximin:Polymer-Gewichtsverhältnis im Bereich von 25:75 bis 75:25 liegt.
 
6. Feste Dispersionsform von Rifaximin gemäß Anspruch 5, wobei das Rifaximin:Polymer-Gewichtsverhältnis im Bereich von 40:60 bis 60:40 liegt.
 
7. Feste Dispersionsform von Rifaximin gemäß Anspruch 1, wobei das Rifaximin:Polymer-Gewichtsverhältnis 50:50 ist.
 
8. Feste Dispersionsform von Rifaximin gemäß Anspruch 1, wobei die feste Dispersionsform von Rifaximin durch ein XRPD gemäß einer oder mehreren der Figuren 12, 17 und 31 gekennzeichnet ist.
 
9. Feste Dispersionsform von Rifaximin gemäß Anspruch 1, wobei die feste Dispersionsform von Rifaximin durch ein Thermogramm gemäß Figuren 13-16, 18-21, 28, 29 und 32 gekennzeichnet ist.
 
10. Mikrokörnchen, das die feste Dispersionsform von Rifaximin gemäß einem der Ansprüche 1-9 umfasst.
 
11. Pharmazeutische Zusammensetzung, umfassend die feste Dispersionsform von Rifaximin gemäß einem der Ansprüche 1-9 und wenigstens ein pharmazeutisch verträgliches Exzipiens.
 
12. Feste Dispersionsform von Rifaximin gemäß einem der Ansprüche 1-9 zur Verwendung bei der Behandlung, Prävention oder Linderung von mit dem Darm in Beziehung stehenden Störungen.
 


Revendications

1. Forme de dispersion solide de rifaximine comprenant de la rifaximine et un polymère sélectionné parmi : le succinate d'acétate d'hydroxypropylméthylcellulose (HPMC-AS) de qualité HG et de qualité MG, dans lequel le rapport pondéral rifaximine/polymère se situe dans la plage entre 10/90 et 90/10.
 
2. Forme de dispersion solide de rifaximine selon la revendication 1, comprenant en outre un poloxamère.
 
3. Forme de dispersion solide de rifaximine selon la revendication 2, dans laquelle le polaxamère comprend du poloxamère 407 ou du Pluronic F-127.
 
4. Forme de dispersion solide de rifaximine selon la revendication 1, dans laquelle le rapport pondéral rifaximine/polymère se situe dans la plage entre 15/85 et 85/15.
 
5. Forme de dispersion solide de rifaximine selon la revendication 4, dans laquelle le rapport pondéral rifaximine/polymère se situe dans la plage entre 25/75 et 75/25.
 
6. Forme de dispersion solide de rifaximine selon la revendication 5, dans laquelle le rapport pondéral rifaximine/polymère se situe dans la plage entre 40/60 et 60/40.
 
7. Forme de dispersion solide de rifaximine selon la revendication 1, dans laquelle le rapport pondéral rifaximine/polymère est de 50/50.
 
8. Forme de dispersion solide de rifaximine selon la revendication 1, dans laquelle la forme de dispersion solide de rifaximine est caractérisée par un XRPD selon une ou plusieurs des figures 12, 17, et 31.
 
9. Forme de dispersion solide de rifaximine selon la revendication 1, dans laquelle la forme de dispersion solide est caractérisée par un thermogramme selon les figures 13 à 16, 18 à 21, 28, 29, et 32.
 
10. Microgranule comprenant la forme de dispersion solide de rifaximine selon l'une quelconque des revendications 1 à 9.
 
11. Composition pharmaceutique comprenant la forme de dispersion solide de rifaximine selon l'une quelconque des revendications 1 à 9 et au moins un excipient pharmaceutiquement acceptable.
 
12. Forme de dispersion solide de rifaximine selon l'une quelconque des revendications 1 à 9 pour une utilisation dans le traitement, la prévention ou le soulagement des troubles liés aux intestins.
 




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REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description




Non-patent literature cited in the description