Abstract:
A stable, oral pharmaceutical composition comprising a proton pump inhibitor and a gelling agent designed for the treatment of gastric acid related diseases in animals, the process for preparation of the composition and the use thereof.

Description:
TECHNICAL FIELD 
     The invention relates to an oral pharmaceutical composition comprising a proton pump inhibitor (PPI) and is designed for the treatment of gastric acid related diseases in animals. 
     BACKGROUND OF THE INVENTION 
     Proton pump inhibitors are potent inhibitors of gastric acid secretion and are used for the treatment of gastric acid related diseases in humans, such as for instance gastric and duodenal ulcers. These substances are susceptible to degradation/transformation in acid reacting and neutral media. Pharmaceutical formulations for oral administration to humans are preferably enteric-coated. These formulations are sensitive to moisture and must be stored in well-closed, tight containers during long-term storage. 
     Peptic ulcer diseases are common also in some animals, especially in horses and camels. Other animals of interest for treatment of peptic ulcer diseases are for example dolphins, sea-lions, llamas, dogs, cats and pigs. By gastro-endoscopic evaluation of horses, ulcers have been found in the squamous mucosa, the non glandular fundus, the glandular stomach and the duodenum. The aetiology of gastro-duodenal ulcers in the equine species is mainly unknown but stress appears to play an important role in some cases. 
     Anti-ulcer compounds such as for instance histamine-2-receptor antagonists have reportedly been administered several times a day to horses by oral or naso-gastric tubes. This procedure can be traumatic and may require light sedation of the horse. Trained persons are required for the administration. 
     Omeprazole and other proton pump inhibitors are potent inhibitors of gastric acid secretion in animals. They block the production of gastric acid by inhibition of H +  K +  -ATPase, the enzyme responsible for the production of hydrogen ions in the parietal cells. The proton pump inhibitors cause profound acid suppression and unlike most other anti-ulcer compounds such as for instance the H 2  -blockers, omeprazole can be given once daily. According to the present invention enteric-coated beads containing omeprazole in a gel formulation can easily be applied onto the dorsal part of the tongue of the horse during field conditions and is well accepted by the horses. 
     Such a moist gel comprising enteric-coated beads of proton pump inhibitors is not stable during long-term storage at room temperature and must be prepared ex tempore. Today there exists no such formulation on the market. 
     Omeprazole, 5-methoxy-2(((4-methoxy-3,5-dimethyl-2-pyridinyl)methyl)sulfinyl)-1H-benzimidazole, is disclosed in European patent no 5129 as a potent inhibitor of gastric acid secretion. 
     Lansoprazole, 2-   3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridyl!methyl!sulfinyl!-1H-benzimidazole, is disclosed in European patent no 174 726 as a potent inhibitor of gastric acid secretion. 
     Pantoprazole is disclosed in European patent no 166 287 as a potent inhibitor of gastric acid secretion. 
     Leminoprazole is disclosed in UK patent no 2 163 747. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide oral pharmaceutical compositions for easy administration to horses and other animals. The proton pump inhibitor is in the form of dry particles, such as beads or tablets, which are coated with one or more coatings one of which is an enteric-coating. The beads or tablets can be prepared by compaction, crystallisation, applying a solution or suspension of the proton pump inhibitor onto inert cores, extrusion and spheronisation or similar processes. The enteric-coated beads or tablets are mixed with dry gelling agent(s), such as for instance xanthan gum, guar gum, locust bean gum, tragacanth, modified cellulose derivatives or similar gel forming compounds. When water is added to this mixture a paste-like gel is formed (having the consistency of a paste). The gel is for example applied dorsally at the tongue of the animal such as a horse with a suitable applicator. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Proton pump inhibitors used in the compositions of the invention are compounds of the general formula I ##STR1## wherein R a  is ##STR2## R 1  and R 3  are independently selected from hydrogen, lower alkyl, lower alkoxy and halogen, R 2  is selected from hydrogen, lower alkyl, lower alkoxy, lower alkoxy--lower alkoxy, lower fluoralkoxy and ##STR3## R 4  and R 5  are independently selected from lower alkyl, A is ##STR4## R 6  and R 7  are independently selected from hydrogen, lower alkyl, lower alkoxy, lower fluoroalkoxy, lower fluoroalkyl, halogen, ##STR5## wherein R 8  is lower alkyl or lower alkoxy. 
     Lower alkyl in the present invention means an alkyl group having 1-5 carbon atoms. 
     Lower alkoxy in the present invention means an alkoxy group having 1-5 carbon atoms. 
     Examples of proton pump inhibitors according to formula I are ##STR6## 
     The proton pump inhibitors used in the compositions of the invention may be used in neutral form or in the form of a basic salt, such as for instance the Mg 2+ , Ca 2+ , Na + , or K +   salts, preferably the Mg 2+   of Na +   salts. Further where applicable, a compound listed above may be used in racemic form or in the form of a substantially pure enantiomer. 
     In one embodiment of the invention the enteric-coated particles are mixed with suitable substances, such as for instance suitable inorganic or organic water soluble salts of potassium, calcium, magnesium or aluminium. When a water solution of a suitable polymeric compound or compounds, such as for instance kappa-carrageenan, pectin, anionic polymers known to give gels with positively charged metal ions, or similar compounds, is added to the mixture a paste-like gel is formed through the interaction of the ions with the polymers. 
     In another embodiment of the invention the enteric-coated particles are mixed with suitable constituents. When a low-viscous solution of a temperature-sensitive polymer, such as for instance ethylhydroxyethylcellulose (EHEC) or polyethylenepolypropylene glycols or similar substances, is added and the system is warmed to temperatures of 33°-35° C. or higher a viscous paste-like gel is formed. 
     In still another embodiment of the invention the enteric-coated particles are mixed with suitable substances in the form of gelforming agents, such as dry gelling agent. As gelforming agents can be used for example acacia, agar, alginic acid, sodium carboxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose or other similar cellulose derivatives, fucoidan, xanthan gum, furcellaran, laminaran or similar gelforming agents. 
     In a preferred embodiment of the invention the proton pump inhibitor is omeprazole. 
     The amount of the different components of the composition can vary and will depend on various factors such as for example the individual requirement of the animal treated. 
     The amount of gelforming agent can vary but is within the range 0.02-20% by weight calculated on the amount of wet gel, preferably in the range of 0.2-20% and especially 0.5-5% by weight. 
     The amount of active substance, i.e. the enteric-coated particles, depends on the individual dosages for the animal. For example the amount of enteric-coated particles is usually in the range of 0.1-20 grams, preferably 0.2-10 grams per dosage for horses. The total volume of the final gel given to horses is in the range of 5-50 ml. 
     Other suitable substances which may be incorporated in the composition are flavouring substances known in the pharmaceutical field. 
     The suitable substances may be added to the enteric-coated proton pump inhibitor particles by mixing the different substances with the enteric-coated particles to a mixture or an ordered mixture. An ordered mixture may be produced for example by particle adhesion or coating processes. 
     The mixtures of enteric-coated proton pump inhibitor particles and the suitable constituents are dried before or after mixing to a moisture level where the proton pump inhibitor has a good long-term stability. The mixture is preferably dispensed into a tight applicator preferably in the form of a syringe. 
     The mixture of the enteric-coated proton pump inhibitor beads or tablets and other constituents can also comprise a suitable pH-buffering substance which will improve the functional stability of the formulation during its transport through the oesophagus and stomach before it reaches the small intestine where the proton pump inhibitor is dissolved and absorbed. Suitable buffering substances are citric acid, tartaric acid, succinic acid, malic acid, lactic acid, benzoic acid, sorbic acid and ascorbic acid and other substances. Such substances will decrease the pH-value of the gel produced to a value below 5.5, thus protecting the enteric coating of the beads or tablets. 
     Further the mixture of the enteric coated proton pump inhibitor particles and suitable constituents may also comprise inert particles, such as inert beads to facilitate the mixing of the different constituents with the enteric-coated particles. Such inert beads are for example beads of coated sugar or any other kind of beads not harmful to the animal. 
     Enteric coated beads or tablets can be prepared by conventional methods. Enteric-coated pellets of omeprazole can for instance be prepared as described in the U.S. Pat. No. 4,786,505 (=EP 247983) hereby incorporated by reference in its entirety. Such enteric coated pellets or beads of omeprazole are preferably coated with at least two coatings one of which is an isolation coating/subcoat and the other is an enteric coating. 
     The preparation of a stable pharmaceutical composition according to the invention is performed by incorporating a proton pump inhibitor in the form of beads or tablets, which are coated with one ore more coatings one of which is an enteric-coating, into a paste-like gel. 
     More particular, the preparation of a formulation in the form of a paste-like gel is performed by either I) mixing the coated particles of the proton pump inhibitor with a dry gelling agent and optionally a pH-buffering system protecting the coated particles whereafter water is added ex tempore, just prior to administration to the animal, or II) mixing the coated particles with a potassium or calcium ion containing salt and optionally a pH-buffering system and thereafter ex tempore, just prior to administration to the animal, with a low-viscous water solution of a gelling agent such as a polymer compound or compounds or by III) mixing the coated particles ex tempore, just prior to administration to the animal, with a low-viscous solution of a gelling agent in the form of temperature-sensitive polymer and optionally with a pH-buffering system and then subjecting the mixture to gentle heating. 
    
    
     EXAMPLES 
     The omeprazole enteric-coated pellets in the examples below are prepared 
     
         ______________________________________Uncoated pellets______________________________________I         Mannitol powder  16 150 g     Lactose anhydrous                      800 g     Hydroxypropyl cellulose                      600 g     Microcrystalline cellulose                      400 gII        Omeprazole       2 000 g     Sodium lauryl sulphate                      50 g     Disodium hydrogen phosphate                      80 g     Distilled water  4 400 g______________________________________ 
    
     The dry ingredients (I) were premixed in a mixer. Addition of a granulation liquid (II) containing suspended omeprazole was made and the mass was wet-mixed to a proper consistency. The wet mass was pressed through an extruder and spheronized to pellets. The pellets were dried and classified into suitable particle size ranges. 
     
         ______________________________________Subcoated pellets______________________________________II        Uncoated omeprazole pellets                       6 000 g     Hydroxypropyl methylcellulose                       240 g     Distilled water   4 800 g______________________________________ 
    
     The polymer solution (III) was sprayed on the uncoated pellets in a fluidized bed apparatus. The spray guns were placed above the fluidized bed. 
     
         ______________________________________Enteric-coated pellets______________________________________IV        Subcoated pellets 500 g     Hydroxypropyl methylcellulose                       57 g     phthalate     Cetyl alcohol     3 g     Acetone           540 g     Ethanol           231 g______________________________________ 
    
     The polymer solution (IV) was sprayed on the subcoated pellets in a fluidized bed apparatus with spray guns placed above the bed. After drying to a water content of 0.5% the enteric coated pellets were classified . . . 
     Example 
     
         ______________________________________Omeprazole enteric-coated pellets                7 g(corresponding to about 600 mg ofomeprazole)Xanthan gum          0.3 gare mixed in a syringe.When 10 ml of water are added a viscous gel is formed.______________________________________ 
    
     Example 
     
         ______________________________________Omeprazole enteric-coated pellets                7         gXanthan gum          0.3       gCitric acid          60        mgare mixed in a syringe.When 10 ml of water are added a viscous gel is formed.______________________________________ 
    
     Example 
     
         ______________________________________Omeprazole enteric-coated pellets                7         gPotassium chloride   30        mgare mixed in a syringe.When 10 ml of a 1% solution of kappa-carrageenan are added aviscous gel is formed.______________________________________ 
    
     Example 
     
         ______________________________________Omeprazole enteric-coated pellets                 7 gare dispensed into a syringe.When 10 ml of a solution of EHEC(ethylhydroxyethylcellulose) 1.25% and sodium laurylsulphate 0.1% are added and warmed to 35° C.a viscous gel is formed.______________________________________ 
    
     Example 
     
         ______________________________________Lansoprazole enteric-coated pellets                     10      g(prepared according to examples 1 and 2 of EP 277 741,Example 1Nonpareils (20-28 mesh), 2250 g. were broughtinto the CF grandulator (CF-360, Freund Industrial Co.,Ltd., Japan), and coated, while being sprayed with 2000 mlof hydroxypropylcellulose solution (3% (w/v)) at 25 ml/min.first with the spraying powder 1 and then the sprayingpowder 2, both of which had been prepared by mixing theingredients listed below, at the rate of 45 g/min at roomtemperature with a rotor rotating at 20 rpm. dried underreduced pressure at 40° C. for 16 hours, and sieved throughround sieves, to give spherical granules having a core of 12-32 mesh.Spraying powder 1compound A                450     gmagnesium carbonate       450     gsucrose                   450     gcorn starch               45      gL-HPC                     450     g(degree of substitution with hydroxypropyl group: 10.0--13.0%(w/w), mean particle size: not more than 30 μm. Theparticles of the same degree of substitution and particlesize were used hereinafter.spraying powder 2sucrose                   420     gcorn starch               360     gL-HPC                     360     gExample 2The granules obtained in Example 1, 3800 g. werebrought into the fluidized-bed coater (Okawara Co., Japan),subjected to enteric coating by spraying the entericcoating film solution described below at the rate of 50ml/min under the controlled conditions of inlet air at 50° C.and material temperature at 40° C., to give enteric coatedspherical granules having core.Enteric coating film solutionEudragit L30D-55          628     gtalc                      192     gpolyethyleneglycol 6000   64      gtitanium oxide            64      gTween 80                  32      gwater                     4400    mlh#r#hy ;nccrpcrat#d by #(corresponding to lansoprazole ˜900 mg)Xanthan gum               0.45    gCitric acid               80      mgWhen 15 m of water are added a viscous gel is formed.______________________________________ 
    
     Example 
     
         ______________________________________Pantoprazole enteric-coated pellets                     7       g(prepared according to example 2 of EP 519 365,PelletsI. Startera) saccharose pellets (0.7-0.85 mm)                     950.0   gb) hydroxypropylmethyl cellulose                     50.0    ga) is sprayed with the aqeous solution of b) in afluidized bed (Wurster method).II. Active pelletsc) pantoprazol-Na-sesquihydrate                     403.0   gd) hydroxypropylmethyl cellulose                     40.3    gc) and d) are dissolved in 30% isoproanol, one after theother, and sprayed onto 900 g of the starter pelletsobtained under I., in a fluidized bed (Wurster method).III. Pre-insulation (intermediate layer)Coating takes place analogous to the method of proceduredescribed for the tablets, in a vat or in a fluidized bed.IV. Coating resistant to gastric juicesCoating takes place analogous to the method of proceduredescribed for the tablets, in a vat or in a fluidized bed.hcr#by incorpcratcd by ref&amp;ence)(corresponding to pantoprazole ˜1200 mg)Xanthan gum               0.3     gCitric acid               50      mgWhen 10 ml of water are added a viscous gel is formed.______________________________________ 
    
     The best mode of carrying out the invention known at present is to use the composition described in Example 2.