BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
[0001] The present disclosure relates to the field of drug delivery, and more particularly
to the use of an enhancer to enhance the permeation of a pharmacologically active
agent through human or animal skin.
2. DESCRIPTION OF RELATED ART
[0002] Phosphodiesterase (PDE) is an enzyme found in various tissues. The interest in PDEs
as molecular targets of drug action has grown with the development of isozyme-selective
PDE inhibitors that offer potent inhibition of selected isozymes without the side-effects
attributed to nonselective inhibitors. Sildenafil, vardenafil and tadalafil are inhibitors
of cGMP-specific phosphodiesterase type 5 (PDE-5).
[0003] PDE-5 inhibitors are used to treat primary pulmonary hypertension (PPH), which is
a disease in which blood vessels in the lungs become abnormally narrow; and erectile
dysfunction. There are now three oral formulation containing PDE-5 inhibitors for
treating erectile dysfunction (ED), they are Viagra (containing sildenafil) by Pfizer,
Levitra (containing vardenafil) by Bayer Pharmaceutical and Glaxo-Smith-Kline-Beecham/Schering
Plough, and Cialis (containing tadalafil) by Lilly-ICOS.
[0004] Although oral delivery is a convenient and non-invasive way of delivering a pharmacologically
active compound, yet it has its own disadvantages. For example, it is slow acting,
for the drug would have to go through the gastrointestinal system of the recipient
before it can reach the intended target site such as penis for ED treatment. Further,
it is more likely to cause a number of side-effects, for the drug will be circulated
systematically instead of exerting its function locally.
[0005] Transdermal delivery is a feasible solution to the above-identified disadvantages
of oral formulation of PDE-5 inhibitors. Various substances are known to enhance the
ability of drugs and agents to diffuse through the skin and other tissues. The more
popular approach has been the employment of surface active agents. However, many surface
active agents enhance the permeability by actually damaging the barrier tissue. Only
slight to moderate enhancement of penetration is effected with the prior art surface
active agents. Another approach is to use certain organic solvents, such as dimethylsulfoxide
(DMSO), dimethyl formamide (DMF) or N,N-dimethylacetamide, to enhance the penetration
of active substances through stratum corneum. A disadvantage of using these solvents
is that they are systemically distributed in a short period of time and cause undesirable
side effects.
[0006] Thus, it would be desirable to provide an improved transdermal formulation that overcomes
the above-identified deficiency. Accordingly, this invention identifies several compounds
that may enhance transdermal delivery of PDE-5 inhibitors, hence are useful for the
development of an improved medicament for treating conditions or diseases mediated
by PDE-5.
[0007] WO 2007/023396 A2 describes a therapeutic kit to provide a safe and effective dosage of a vascoactive
agent including a foamable emulsion composition for transdermal or mucosal administration
comprising a vasoactive agent, such as a PDE-5 inhibitor, at least one organic carrier,
a surface-active agent, at least one polymeric additive, water and a gas propellant.
The vasoactive agent may be sildenafil or vardenafil and betaines may be used as surface-active
agents in this composition.
SUMMARY
[0008] The present disclosure is based on the finding that certain agent(s) is effective
as an enhancer to promote transdermal delivery of a PDE-5 inhibitor, hence is useful
as an agent or an adjuvant for developing a topical medicament for treating conditions
or diseases mediated by PDE-5 such as erectile dysfunction or primary pulmonary hypertension.
[0009] Accordingly, it is therefore an object of the present disclosure to provide an improved
transdermal pharmaceutical composition with an enhanced transdermal absorption rate
of a PDE-5 inhibitor. According to embodiments of the present disclosure, an improved
transdermal pharmaceutical composition according to claim 1 is defined, comprising
vardenafil as PDE-5 inhibitor or a pharmaceutically acceptable salt thereof, an enhancer
as claimed, and a pharmaceutical excipient.
[0010] The enhancer is selected from the group consisting of cocamidopropyl betaine, sodium
lauroamphoacetate, quaternium-60, isostearamidopropyl morpholine lactate, dipropylene
glycol and a combination thereof. In one example, the enhancer is cocamidopropyl betaine.
In another example, the enhancer is a mixture of cocamidopropyl betaine and sodium
lauroamphoacetate. In still another example, the enhancer is a mixture of cocamidopropyl
betaine, sodium lauroamphoacetate, and quaternium-60. In one preferred example, the
enhancer is a mixture of cocamidopropyl betaine, sodium lauroamphoacetate, quaternium-60,
isostearamidopropyl morpholine lactate, and dipropylene glycol. In one preferred example,
the PDE-5 inhibitor is vardenafil, which is not in crystalline state.
[0011] According to embodiments of the present disclosure, the improved pharmaceutical composition
may be formulated into the form of a solution, a paste, a lotion, a cream, a gel,
or a patch. In one embodiment, improved pharmaceutical composition is a gel. In another
embodiment, the improved pharmaceutical composition is a skin patch. In another aspect,
the composition is for use in treating erectile dysfunction or primary pulmonary hypertension.
[0012] The improved pharmaceutical composition of the present disclosure can attain the
same therapeutic benefits to the recipient thereof at a reduced level of PDE-5 inhibitor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] These and other features, aspects and advantages of the present invention will become
better understood with reference to the following description, appended claims and
the accompanying drawings, where:
FIG 1 illustrates the effects of formulations of Example 2.1 on in vitro transdermal delivery of vardenafil in accordance with one embodiment of the present
disclosure; and
FIG 2 illustrates the effects of the formulations of Example 2.1 and the skin patch
of Example 2.2 on in vivo transdermal delivery of vardenafil in accordance with one embodiment of the present
disclosure.
DESCRIPTION
[0014] These and other features, aspects and advantages of the present invention will become
better understood with reference to the following description and the appended claims
[0015] The detailed description provided below in connection with the appended drawings
is intended as a description of the present examples and is not intended to represent
the only forms in which the present example may be constructed or utilized. The description
sets forth the functions of the example and the sequence of steps for constructing
and operating the example. However, the same or equivalent functions and sequences
may be accomplished by different examples.
Definitions
[0016] For convenience, certain terms employed in the specification, examples and appended
claims are collected here. Unless defined otherwise, all technical and scientific
terms used herein have the same meaning as commonly understood by one of the ordinary
skill in the art to which this invention belongs.
[0017] Unless otherwise defined herein, scientific and technical terminologies employed
in the present disclosure shall have the meanings that are commonly understood and
used by one of ordinary skill in the art. Unless otherwise required by context, it
will be understood that singular terms shall include plural forms of the same and
plural terms shall include the singular. Specifically, as used herein and in the claims,
the singular forms "a" and "an" include the plural reference unless the context clearly
indicates otherwise. Also, as used herein and in the claims, the terms "at least one"
and "one or more" have the same meaning and include one, two, three, or more.
[0018] Notwithstanding that the numerical ranges and parameters setting forth the broad
scope of the invention are approximations, the numerical values set forth in the specific
examples are reported as precisely as possible. Any numerical value, however, inherently
contains certain errors necessarily resulting from the standard deviation found in
the respective testing measurements. Also, as used herein, the term "about" generally
means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term
"about" means within an acceptable standard error of the mean when considered by one
of ordinary skill in the art. At the very least, each numerical parameter should at
least be construed in light of the number of reported significant digits and by applying
ordinary rounding techniques.
[0019] As used herein, the term "enhancer" is defined as a substance that, when added to
the pharmaceutical composition, enhances the absorption kinetics, hence the bioavailability
of a pharmacologically active agent,
i.e., the PDE-5 inhibitor, while having few or none of direct therapeutically effects when
given by itself.
[0020] The term "transdermal delivery" as used herein refers to delivery by passage of a
compound or drug through the skin and into the bloodstream.
[0021] "Enhanced delivery", "enhanced permeability", "enhanced permeation", or "enhanced
absorption" are used interchangeably herein to represent an increase in the permeability
of skin to a pharmacologically active agent,
i.e., so as to increase the rate at which the drug (e.g., the PDE-5 inhibitor) permeates
through the skin and enters the bloodstream. The enhanced permeation effected through
the use of the improved composition of the present invention can be observed by measuring
the rate of diffusion of a drug through animal or human skin using a diffusion cell
apparatus as described in the Examples herein.
[0022] As used herein, a "pharmaceutically acceptable" component is one that is suitable
for use with humans and/or animals without undue adverse side effects (such as toxicity,
irritation, and allergic response) commensurate with a reasonable benefit/risk ratio.
[0023] The term "an effective amount" as used herein refers to an amount effective, at dosages,
and for periods of time necessary, to achieve the desired therapeutically desired
results with respect to the treatment of diseases or conditions mediated by PDE-5,
such as erectile dysfunction or primary pulmonary hypertension. It will be appreciated
that the therapeutically effective amount of the PDE-5 inhibitor will vary from subject
to subject not only for the particular PDE-5 inhibitor selected, the route of administration,
and the ability of the PDE-5 inhibitor (alone or in combination with one or more PDE-5
inhibitor or other drugs) to elicit a desired response in the subject, but also factors
such as state or severity of the condition to be alleviated, age, weight of the subject,
the state of being of the subject, and the severity of the condition being treated,
concurrent medication or special diets then being followed by the subject, and other
factors which those skilled in the art will recognize, with the appropriate dosage
ultimately being at the discretion of the attendant physician. Dosage regimens may
be adjusted to provide the improved therapeutic response. An effective amount is also
one in which any toxic or detrimental effects of the compound or composition are outweighed
by the therapeutically beneficial effects. Preferably, the PDE-5 inhibitor is administered
at a dosage and for a time such that the severity of the symptoms is decreased.
[0024] The term "subject" refers to any animal (e.g., a mammal), including, but are not
limited to humans, non-human primates, which is to be subjected under the treatment
of this invention. Typically, "patient" and "subject" are used interchangeably herein
in reference to a human subject.
[0025] The term "excipient" as used herein means any inert substance (such as a powder or
liquid) that forms a vehicle/carrier for the PDE-5 inhibitor and/or enhancer. The
excipient is generally safe, non-toxic, and in a broad sense, may also include any
known substance in the pharmaceutical industry useful for preparing pharmaceutical
compositions such as, fillers, diluents, agglutinants, binders, lubricating agents,
glidants, stabilizer, colorants, wetting agents, disintegrants, and etc.
[0026] The practices of this invention are hereinafter described in detail with respect
to a method and a pharmaceutical composition that improves the transdermal delivery
effects, and, thus, enhances the bioavailability of a PDE-5 inhibitor in a subject.
[0027] According to embodiments of the present disclosure, the improved transdermal pharmaceutical
composition as claimed comprises vardenafil as a PDE-5 inhibitor or a pharmaceutically
acceptable salt thereof, and a pharmaceutically acceptable excipient, wherein the
improvement comprises, an enhancer selected from the group consisting of cocamidopropyl
betaine, sodium lauroamphoacetate, quaternium-60, isostearamidopropyl morpholine lactate,
dipropylene glycol and a combination thereof; wherein the PDE-5 inhibitor and the
enhancer are present in a ratio as claimed in the improved transdermal pharmaceutical
composition.
[0028] The enhancer suitable for use in this invention is selected from the group consisting
of cocamidopropyl betaine, sodium lauroamphoacetate, quaternium-60, isostearamidopropyl
morpholine lactate, dipropylene glycol and a combination thereof. Cocamidopropyl betaine
or {[3-(Dodecanoylamino)propyl](dimethyl)ammonio} acetate is a synthetic surfactant
derived from coconut oil and dimethylaminopropylamine. Sodium lauroamphoacetate or
Sodium 2-[1-(2-hydroxyethyl)-2-undecyl-4,5-dihydroimidazol-1-ium-1-yl]acetate is an
amphoacetate commonly used in moisturizers. Quaternium-60 is an active quaternary
commonly dissolved in propylene glycol. By including the enhancer in the present improved
composition, it is ensured that the PDE-5 inhibitor is completely dissolved in, or
without being crystallized out of, the improved composition, and thereby increases
the availability of PDE-5 inhibitor for transporting across stratum corneum. In case
the enhancer is cocamidopropyl betaine, then vardenafil and the enhancer are present
in a weight ratio of 5:1 in the improved composition. In case the enhancer is a one-to-one
mixture of cocamidopropyl betaine and sodium lauroamphoacetate; the vardenafil and
the enhancer are present in a weight ratio of 6:1 in the improved composition. In
case the enhancer is a mixture of cocamidopropyl betaine, sodium lauroamphoacetate
and quaternium-60; the vardenafil and the enhancer are present in a weight ratio of
4:1 in the improved composition. In case the enhancer is a mixture of cocamidopropyl
betaine, sodium lauroamphoacetate, quaternium-60, isostearamidopropyl morpholine lactate,
and dipropylene glycol; the vardenafil and the enhancer are present in a weight ratio
of 3:1 in the improved composition.
[0029] The pharmaceutical compositions of this invention may be formulated into a variety
of dosage forms for topical application. A wide variety of dermatologically acceptable
inert excipients well known to the art may be employed. The topical compositions may
include liquids, pastes, creams, lotions, ointments, gels, sprays, aerosols, skin
patches, and the like. Typical inert excipients may be, for example, water, ethyl
alcohol, polyvinyl pyrrolidone, propylene glycol, mineral oil, stearyl alcohol and
gel-producing substances. All of the above dosages forms and excipients are well known
to the pharmaceutical art. The choice of the dosage form is not critical to the efficacy
of the composition described herein.
[0030] When formulated for presentation as a solution, the improved composition can include
volatile carriers such as ethanol and water as well as non-volatile carriers such
as medium chain length triglyceride and straight chain aliphatic alcohols. Thus a
typical solution composition of this invention includes at least, a concentration
of the PDE-5 inhibitor in a range of about 1-20% by weight, a concentration of the
enhancer in a range of about 0.2-5% by weight, and a concentration of volatile and
non-volatile carriers in the range of about 0.5-98% by weight, respectively.
[0031] When formulated for presentation as a lotion, the improved composition can include
a finely divided solid and a thickener. Thus a typical lotion composition of this
invention includes at least, a concentration of the PDE-5 inhibitor in a range of
about 1-20% by weight, a concentration of the enhancer in a range of about 0.2-5%
by weight, a concentration of the finely divided solid in the range of about 0.5-5%
by weight, and a concentration of the thickener in the range of about 2-5% by weight.
[0032] When formulated for presentation as a cream, the improved composition can include
emollient and an emulsifier, as well as an antioxidant and/or preservative. Thus a
typical cream composition of this invention includes at least, a concentration of
the PDE-5 inhibitor in a range of about 1-20% by weight, a concentration of the enhancer
in a range of about 0.2-5% by weight, a concentration of the emollient in the range
of about 0-50% by weight, and a concentration of the emulsifier in the range of about
0-20% by weight.
[0033] When formulated for presentation as a gel, the improved composition can include a
gelling agent such as a finely divided solid and/or thickener in concentrations that
produce a loose molecular network inhibiting the free movement of liquid ingredients.
Thus a typical gel composition of this invention includes at least, a concentration
of the PDE-5 inhibitor in a range of about 1-20% by weight, a concentration of the
enhancer in a range of about 0.2-5% by weight, a concentration of the thickener in
the range of about 2-5% by weigh, and a concentration of the finely divided solid
in the range of about 0-20% by weight.
[0034] The improved compositions of this invention may also be formulated into an aerosol
formulation for drug delivery through skin. Thus a typical aerosol composition of
this invention includes, at least, a concentration of the PDE-5 inhibitor in a range
of about 1-20% by weight, a concentration of the enhancer in a range of about 0.2-5%
by weight, a concentration of a propellant and/or co-solvent in a range of 10-90%
by weight. Suitable propellants and/or co-solvents for solubilizing the PDE-5 inhibitor
and the enhancer of this invention in medicinal aerosol formulations are well known
in this art. Typical propellants are hydrofluoroalkanes such as 1,1,1,2-tetrafluoroethane
(HFA-134a), 1,1,1,2,3,3,3-heptafluoropropane (HFA-227ea). pentafluoroethane (HFA-125),
1,1-difluoroethane (HFA-152a), difluoromethane (HFA-32) and the like. Typical co-solvents
include, but not limited to, alcohols, polyols, alkoxy derivatives, fatty acid alkyl
esters, polyalkylene glycols, dimethylsulphoxide and the like.
[0035] In a particularly preferred embodiment, the improved composition is administered
to the recipient by means of a skin patch. The skin patch is prepared by incorporating
in a matrix such as a gauze pad the improved formulation of this invention (e.g.,
any of the gel formulations 2 to 5 of Example 2.1). Transdermal delivery is accomplished
by exposing the recipient's skin to one side of the patch for an extended period of
time, so that PDE-5 inhibitor is released on to and across the recipient's skin. Many
suitable transdermal delivery patches are known, ranging from a simple gauze pad impregnated
with the formulation of this invention and secured to the skin with an adhesive bandage
to multilayer structures. Typically, a transdermal delivery patch may also contain
other added substances that enhance the penetration of the PDE-5 inhibitor,
i.e., substances other than the enhancer identified by the inventors of this application.
Many known enhancers may be used together with the enhancers of this invention, to
improve skin penetration of PDE-5 inhibitor.
[0036] The improved composition of this invention can be prepared by conventional procedures,
such as those described in
Remington's Pharmaceutical Sciences, 17th edition, ed. Alfonoso R. Gennaro, Mack Publishing
Company, Easton, Pa (1985). Pharmaceutically acceptable excipients are those that are compatible with other
ingredients in the formulation and biologically acceptable. To minimize contamination
from the growth of microorganisms, sterilized equipment is preferably used. Once blended,
the composition can be packaged and stored in any suitable container inert to the
contents including aluminum, glass, stainless steel, and solvent resistant plastics
including polyamide, polyester, polypropylene, and ABS polymer. Storage is preferably
in a cool place away from strong sunlight. Continued sterility can be assured by conventional
techniques including aseptic packaging and post-sterilization in the final package
by electron beam exposure.
[0037] Accordingly, this invention also provides the composition of the invention for use
in the treatment of erectile dysfunction or primary pulmonary hypertension. The treatment
comprises the step of administrating the improved pharmaceutical composition of this
invention to the mammals in need thereof. Accordingly, such composition is transdermally
administered to a mammal, preferably human, with an enhanced absorption of the PDE-5
inhibitor by the human subject.
[0038] The present invention will now be described more specifically with reference to the
following embodiments, which are provided for the purpose of demonstration rather
than limitation.
EXAMPLES
Example 1 In Vitro Permeation Analysis
[0039] The permeation test was carried out using
in vitro Franz diffusion cell with a diffusion area of 0.785 cm
2. A piece of rat (Sprague-Dawley) skin tissue was mounted between the two half-cells
and fastened with a clamp. Aliquots of 1% (wt%) vardenafil with or without the addition
of the enhancer of this disclosure, such as 0.3% (wt%) cocamidopropyl betaine, 1%
(wt%) sodium lauroamphoacetate, 1% (wt%) isostearamidopropyl morpholine lactate, 1%
(wt%) quaternium-60 or dipropyl glycol, were applied to the Donor compartment to start
the experiment. The receiver compartment was filled with PBS and the temperature was
held at 37°C. Samples were taken at certain time intervals and assayed by HPLC. Amounts
of vardenafil accumulated in the receiver compartment were calculated and results
were summarized in FIG 1, wherein:
| |
1 |
2 |
3 |
4 |
5 |
6 |
| 1% Vardenafil |
+ |
+ |
+ |
+ |
+ |
+ |
| 0.3% cocamidopropyl betaine |
- |
+ |
- |
- |
- |
- |
| 1% sodium lauroamphoacetate |
- |
- |
+ |
- |
- |
- |
| 1% isostearamidopropyl morpholine lactate |
- |
- |
- |
+ |
- |
- |
| 1% quaternium 60 |
- |
- |
- |
- |
+ |
- |
| 1% dipropyl glycol |
- |
- |
- |
- |
- |
+ |
[0040] As depicted in FIG 1, an increase in skin permeation was achieved with the inclusion
of the enhancer in the formulation; penetration effect of the enhancer was seen with
the amount of vardenafil in the receiving side of Franz Diffusion chamber increased
by about 0.5-2 folds as compared with that of the control (i.e., 1% vardenafil).
Example 2 In Vivo Permeation Analysis
2.1 Preparation of Gels Containing Vardenafil (not according to the invention)
[0041] Formulations (# 1 to 4) were prepared by stirring together separately prepared pre-mixtures
of water insoluble ingredients and the water-soluble ingredients as tabulated bellow
(all quantities are in weight %) until gels were formed, then adjusted the pH of the
respective gel formulations to a range between 2.5 and 3.5.
| Formulation # |
1 |
2 |
3 |
4 |
| Water-insoluble |
|
|
|
|
| Methyl paraben |
0.2 |
0.2 |
0.2 |
0.2 |
| Propyl paraben |
0.2 |
0.2 |
0.2 |
0.2 |
| Propylene glycol |
5 |
5 |
5 |
5 |
| Ethanol |
5 |
5 |
5 |
5 |
| cellulose |
0.5 |
0.5 |
0.5 |
0.5 |
| Water-soluble |
|
|
|
|
| L-arginine |
0.5 |
0.5 |
0.5 |
0.5 |
| EDTA |
0.5 |
0.5 |
0.5 |
0.5 |
| NaCl |
- |
0.5 |
0.5 |
0.5 |
| Vardenafil HCl |
3 |
5 |
7 |
6 |
| Tartaric acid |
- |
0.3 |
0.3 |
0.3 |
| Cocamidopropyl betaine |
- |
0.3 |
0.15 |
0.15 |
| Sodium lauroamphoacetate |
- |
- |
1 |
0.5 |
| Quaternium-60 |
- |
- |
- |
1 |
| H2O |
85.1 |
82 |
79.15 |
79.65 |
2.2 Preparation of Skin Patch Containing Vardenafil (not according to the invention)
[0042] Formulation (#5) was prepared using ingredients tabulated bellowed (all ingredients
were listed in weight %) in accordance with similar procedure as described above in
example 2.1. The thus obtained formulation (# 5) was then applied onto the surface
of a non-woven cloth, and let stand for 7 days until it gelled, thereby forming the
desired skin patch.
| Formulation # |
5 |
| Water-insoluble |
|
| Methyl paraben |
0.2 |
| Propyl paraben |
0.2 |
| Propylene glycol |
10 |
| Ethanol |
10 |
| Sodium polyacrylate |
5 |
| Polyacrlic acid |
2 |
| cellulose |
1 |
| Water-soluble |
|
| L-arginine |
1 |
| EDTA |
0.3 |
| NaCl |
1 |
| Vardenafil HCl |
8 |
| Tartaric acid |
0.2 |
| Cocamidopropyl betaine |
0.2 |
| Sodium lauroamphoacetate |
0.3 |
| Quaternium-60 |
0.5 |
| Isostearamidopropyl morpholine lactate |
1 |
| Dipropylene glycol |
0.5 |
| H2O |
58.6 |
2.3 In Vivo Permeation Analysis
[0043] In vivo skin permeation tests were carried out using the gel formulations of example 2.1
and the skin patch of example 2.2. Briefly, small aliquots (about 0.5 ml) of gel formulations
# 1 to 4 or a small piece of the skin patch (3 cm x 5 cm x 0.15 cm) was applied to
the left ear of a rabbit, after certain period of time, 1 ml of blood was drawn from
the rabbit's right ear artery and analyzed for the amount of vardenafil. Specifically,
the blood was drawn after 1 hour when gel formulation was used; and 6 hours when skin
patch was applied. Results are illustrated in FIG 2.
[0044] It is evident from the results depicted in FIG 2, the enhancer(s) identified in the
present invention, when applied simultaneously with vardenafil, either alone or in
combination, significantly enhances the permeation of vardenafil across the skin,
with the amount of vardenafil found in the blood stream increased by about 4 to 5
folds, as compared with that of the control.