The present invention relates to pharmaceutical formulations for oral administration, and particularly to those containing gliclazide.

Pharmaceutical formulations for oral administration containing gliclazide as the active ingredient are well known.

The patent WO 0018373 describes the production of core tablets by mixing several types of hydroxypropyl methylcellulose (HPMC) and adding maltodextrin and other diluents.

The production method involves the following steps:

• mixing all the components except for the HPMC
• wet granulation with water
• drying and grading of the granules
• mixing first with the various types of HPMC to form the delayed-release matrix and then with lubricants
• compression.

A hydrophilic core tablet is thus obtained with a mechanism of release by means of gelification.

This type of formulation has considerable drawbacks, i.e.

• lengthy and costly process times;
• the need for ample production areas;
• the risk of segregating the active ingredient from the granules;
• contamination and toxicity of the production environments and for the operators involved, due to the dust forming in the various production stages and the considerable handling needed during the production process.

On the other hand, patents EP 1064935 and US 6319520 describe the formation of granules by means of thermoforming process using methacrylate derivatives, such as Eudragit RS, RL, E.

After granulation, which takes place at a temperature coming between 60 and 150°C, the resulting granules are compressed to produce core tablets.

The mechanism of release from these tablets is diffusive and it is pH-independent, in particular, in the case of Eudragit RS + Eudragit RL being used.

This type of formulation has the drawback of demanding a high-temperature extrusion process with a consequent risk of damaging the active ingredient and making the working conditions particularly hazardous.

Zhang et al. (STN Database Accession no. 2006:1098308; ZHONGGUO YAOYE, 15(10), 27-29) describes a granule composition comprising gliclazide, microcrystalline cellulose, ethylcellulose, stearic acid. The pellets are manufactured by extruding and spheronizing.

WO2006/061697A1 discloses once a da sustained release graaanules obtained by wet granulation comprising: a) gliclazide, b) the hydrophilic polymer HPMC K4M and c) HPMC K100VL. The granules are further blended with talc, colloidal silico dioxide and magnesium stearate before compression into tablets.

It has now surprisingly been established that gliclazide can be mixed with hydrophilic ingredients in combination with a hydroxypropyl methylcellulose and lipophilic ingredients with a low melting point to obtain dust-free granules suitable, without further handling, for compression to form tablets.

Said tablets are characterised in that they release the active ingredients they contain over a period of 24 hours.

Object of the present invention are tablets according to claim 1 and a process for preparing tablets according to claim 8. Oral formulations comprising gliclazide can be mixed with hydrophilic ingredients in combination with a hydroxypropyl methylcellulose and lipophilic ingredients with a low melting point.

The term hydrophilic ingredients is used to mean hydrophilic polymers (e.g. hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxypropyl cellulose, ethylene polyoxide, carbomer or mixtures thereof), mannitol, dibasic sodium phosphate, sorbitol, isomalt, or mixtures thereof.

According to the invention, HPMC is the preferred hydroxypropyl methylcellulose, in a solution at 2% w/w, with a viscosity corresponding to approximately 4000 cps. The term lipophilic elements with a low melting point is used herein to mean, for instance, stearic acid, carnauba wax, cetyl alcohol or cetyl stearyl alcohol. According to the invention, the above-mentioned components are contained in the following proportions (calculated weight to weight with respect to the total weight of the mixture):

Gliclazide: 10-30% Stearic acid 5-20% Carnauba wax 5-20% HPMC (viscosity 2% w/w approx 4000 cps) 5-25% Mannitol 10-50% Dibasic sodium phosphate 10-30% Magnesium stearate 0.1-5% Anhydrous colloidal silica 0.1-5% HPMC 5 cps 1 - 5% PEG 4000 0.1 - 5% Talc 0.1-5% Titanium dioxide 0.1 - 5%

More preferably: Gliclazide: 15-20% Stearic acid 10-20% Carnauba wax 5-15% HPMC (viscosity 2% w/w approx 4000 cps) 10-20% Mannitol 15-40% Dibasic sodium phosphate 10-20% Magnesium stearate 1-3% Anhydrous colloidal silica 1-3% HPMC 5 cps 1-4% PEG 4000 0.1-3% Talc 0.5-3% Titanium dioxide 0.5-4%

The above-described granules can be prepared in a single production step by granulation-extrusion at a temperature lower than 50°C, using standard granule production methods.

The granules are then mixed with the typical additives used in the preparation of tablets for oral administration, such as: lubricants 0.5-2% separating agents 0.1-3% anticaking agents 0.1-10% and ultimately compressed.

If necessary, the tablets are subsequently coated with a soluble film (generally containing a low-viscosity hydroxypropyl methylcellulose or acrylic polymers, or colouring agents, etc) to facilitate their swallowing, make the tablets readily identifiable and facilitate subsequent procedures.

For the sake of completeness and a better understanding of the present invention, several examples of formulations according to the invention and their preparation are given below.

The components listed below are mixed together in an automatic drum mixer for 20 minutes at a turning speed of 4 rpm. Gliclazide 3000 g (19.5%) Mannitol 4481 g (29.1%) Stearic acid 1539 g (10.0%) Carnauba wax 1539 g (10.0%) Dibasic sodium phosphate 2923 g (19.0%) HPMC (viscosity 2% w/w approx 4000 cps) 1904 g (12.4%)

The resulting mixture is extruded using the Leistritz HP18 extruder in the following working conditions: temperature of the refrigerant: 15°C temperature of the extruder: 50°C temperature of the extruded products: 53°C

The granules thus obtained are mixed with the lubricants (magnesium stearate and anhydrous colloidal silica) and compressed into tablets containing doses of 30 and 60 mg of active ingredient. Magnesium stearate: 2 mg/tab (30 mg) 4mg/cpr (60 mg) Anhydrous colloidal silica: 1 mg/tab (30 mg) 2 mg/tab (60 mg)

Characteristics of the tablets: mean weight of tablet: 157 mg shape of tablet: oval size of tablet: 11x5.6 mm

The tablets thus obtained are coated with a film in a GS 25 drum mixer using a titanium-dioxide-based white colouring agent in order to obtain a 10 mg increase in the weight of the tablet, under the following working conditions: air temperature at inlet: 55°C drum turning speed: 12 rpm nebulising pressure: 1 bar

The resulting tablets have a 24-hour release profile.

The components listed below are mixed in a suitable mixer: Gliclazide 733 g (19,5%) Mannitol 1095 g (29,1%) Stearic acid 376 g (10.0%) Carnauba wax 376 g (10.0%) Dibasic sodium phosphate 714 g (19.0%) HPMC (viscosity 2% w/w approx 4000 cps) 465 g (12.4%)

The resulting mixture is extruded using the Leistritz HP18 extruder; the granules obtained are mixed with the lubricants and then compressed into tablets containing 30 and 60 mg of active ingredient, as previously described in example 1.

The tablets have a 24-hour release profile.

The components listed below are mixed in a suitable mixer. Gliclazide 733 g (19.5%) Isomalt 950 g (25.3%) Stearic acid 448 g (11.9%) Carnauba wax 449 g (11.9%) Dibasic sodium phosphate 700 g (18.6%) HPMC (viscosity 2% w/w approx 4000 cps) 479 g (12.8%)

The mixture thus obtained is extruded using the Leistritz HP18 extruder; the resulting granules are mixed with the lubricants and subsequently compressed into tablets containing doses of 30 and 60 mg of active ingredient, as described previously in example 1.

The tablets have a 24-hour release profile.

As an example, the analytical results obtained on a batch of gliclazide 30 mg are given below. Time Release 1 h 16% 4h 55% 8h 86% 12h 100%