Abstract:
The present invention relates to sustained release tablet formulations of venlafaxine. Kollidon SR proved to be an excellent sustained release agent for venlafaxine, that is an extremely soluble drug.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to sustained release tablet formulations of venlafaxine.  
       TECHNICAL BACKGROUND AND PRIOR ART  
       [0002]     Venlafaxine, (+/−)-[α-[(dimethylamino)methyl]-p-methoxybenzyl]cyclohexanol, is a phenylethylamine derivative which facilitates neurotransmission in the brain by blocking presynaptic reuptake of serotonin and noradrenaline for use in treating depression. See for example Holliday and Benfield, Venlafaxine, a review of its pharmacology and therapeutic potential in depression, Drugs, Vol. 49, No. 2, 1995, pp 280-294.  
         [0003]     U.S. Pat. No. 4,535,186 describes venlafaxine and its acid additional salts.  
         [0004]     The preparation of useful sustained release formulations of venlafaxine hydrochloride is complicated because venlafaxine HCl is very water soluble. The advantage of sustained release tablets compared to conventional tablets is that the frequency of dosage administration is reduced. Sustained release formulations can further have the advantage of inducing less side effects than conventional tablets, because the blood plasma levels of the active compound increase more slowly.  
         [0005]     WO 9427589 concerns controlled-release dosage forms comprising venlafaxine and polymers selected from poly(alkylene oxide) polymer, cellulose polymer and maltodextrin polymer.  
         [0006]     WO 99/22724 (EP 1028718) relates to extended release spheriod cores of venlafaxine hydrochloride. The cores are prepared by means of microcrystalline cellulose without the addition of hydroxypropylmethylcellulose. Furthermore, ethylcellulose is used as sustained release coating agent on the core in this formulation.  
         [0007]     Sustained release tablets of venlafaxine hydrochloride are discussed in Makhija and Vavia, Once daily sustained release tablets of venlafaxine, a novel antidepressant, European Journal of Pharmaceutics and Biopharmaceutics, Vol. 54, No. 1, July 2002, pp 9-15. The article relates to matrix system based on swellable as well as non-swellable polymers. The polymers studied are hydroxypropylmethylcellulose, cellulose acetate, Eudragit RSPO and ethylcellulose.  
       SUMMARY OF THE INVENTION  
       [0008]     In an attempt to prepare a suitable sustained release tablet of venlafaxine numerous sustained release agents were tried, povidone (e.g. Kollidone), hydrogenated vegatable oil (e.g. Lubritab), polyethylene glycol (e.g. Macrogol), glyceril behenate (e.g. Compritol), polymethacrylates (e.g. Eudragit), hydroxypropylmethylcellulose (e.g. Methocel) and glyceryl palmitostearate (e.g. Precirol).  
         [0009]     It was discovered that useful formulations of venlafaxine can be produced by use of a mixture of povidone and polyvinylacetate known as Kollidone SR.  
         [0010]     Kollidon SR is used in various applications including preparing sustained release pharmaceutical compositions, as described in the technical and patent literature. For example, EP 0 231 826 B1 describes sustained release tablet containing theophylline as the active ingredient.  
         [0011]     The properties of Kollidone SR are described in V. Buhler, Kollidon®, Polyvinylpyrrolidone for the pharmaceutical industry, 233-249, BASF, Ludwigshafen 2001.  
         [0012]     Kollidone SR consists mainly of two polymers, povidone and polyvinyl acetate. The povidone part is water soluble but the polyvinyl acetate is water-insoluble. When a tablet comprising Kollidone SR is immersed in a water solution the water soluble polymer dissolves and passages are formed in the tablet. The active ingredinet will then diffuse through the passages.  
         [0013]     Althought Kollidone SR is a known sustained release agent, the inventors were surprised to find that it was so suitable agent for venlafaxine because of the high solubility of the active material.  
         [0014]     However, the dissolution profile of uncoated tablets that contained Kollidone SR as the only sustained-release agent showed a faster release in the beginning than was intended. In a single dose pharmacokinetic study of these tablets the C max  was slightly higher in the beginning than was anticipated.  
         [0015]     In an attempt to further control the initial rate of release of venlafaxine from the tablets, several types of film materials were tested and polymethacrylates proved to be suitable and several types of this film material were extensively tested. Coating the tablets with a film that contained polymethacrylates proved to be surprisingly effective for the sustained release tablet of venlafaxine.  
         [0016]     The polymethacrylates that were tested are mixtures of polyethyl acrylate and polymethyl methacrylate and they optionally also include trimethylammonioethyl methacrylate chloride. The trade names for the tested polymethacrylates are Eudragit RS, Eudragit RL and Eudragit NL.  
         [0017]     By coating the tablets with a film containing Eudragit SR 30 D, the C max  fitted intended criteria.  
         [0018]     Conventional hydroxypropylmethylcellulose (HPMC) based coatings do not affect the dissolution rate of sustained release tablets, since they dissolve too quikly in vivo.  
         [0019]     Properties of polymethacrylates are described in A. H. Kibbe, Handbook of pharmaceutical excipients, 401-406, American Pharmaceutical Association, Washington, and Pharmaceutical Press, London, 2000.  
         [0020]     Eudragit RS is a water insoluble, swellable film-former based on neutral methacrylic acid esters with a small proportion of trimethylaminoetyl methacrylate chloride. The ratio is 1:40 trimethylaminoetyl methacrylate chloride:methacrylic acid esters.  
         [0021]     The quaternary ammonium groups determine the swellability of the films and their permeability to water, dissolved salts and medicinal substances. The small amount in the Eudragit RS result in the properties that it swells less than comparable Eudragit film formers, and is only slightly permeable to active ingredients. 
     
    
     BRIEF DESCRIPTION OF FIGURES  
       [0022]      FIG. 1  shows the effect of increasing amount of Kollidone RS on the dissolution rate of venlafaxine HCl.  
         [0023]      FIG. 2  shows the effect of increasing the hardness of the tablets on the dissolution profile of venlafaxine HCl.  
         [0024]      FIG. 3  shows the dissolution profiles of venlafaxine sustained release tablets in two different media, water and 0.01 M HCl. The dissolution profiles are independent of the pH.  
         [0025]      FIG. 4  shows the dissolution profiles of uncoated tablets and tablets coated with a film containing Eudragit RS 30 D. The amount of the film on the tablet surface affects the dissolution rate.  
     
    
     DETAILED DESCRIPTION  
       [0026]     The invention provides a sustained release pharmaceutical formulation comprising pharmaceutically effective amount of venlafaxine or an acid addition salt thereof,  
                         
 
 a sustained release agent selected from sustained release agent selected from povidone, a mixture of povidone and polyvinyl acetate, hydrogenated vegatable oil, polyethylene glycol, glyceril behenate and glyceril palmitostearate; and a lubricant. 
 
         [0027]     The pharmaceutical formulation of the present invention comprises:  
         [0000]     a) 15-40% w/w of venlafaxine HCl;  
         [0000]     b) 50-85% w/w of the sustained release agent; and  
         [0000]     c) 0.5-5.0% w/w of lubricant  
         [0000]     and optionally a filler material and glidant.  
         [0028]     The sustained release agent may suitably be selected from povidone (e.g. Kollidone), a mixture of povidone and polyvinyl acetate (e.g. Kollidone SR), hydrogenated vegatable oil (e.g. Lubritab), polyethylene glycol (e.g. Macrogol), glyceril behenate (e.g. Compritol), polymethacrylates (e.g. Eudragit), hydroxypropylmethylcellulese (e.g. Methocel) and glyceryl palmitostearate (e.g. Precirol).  
         [0029]     The Kollidone SR was found to be especially suitable in controlling the release of venlafaxine. It was found that the dissolution profiles for the tablets depend on the amount of the Kollidone SR. Furthermore, it was found that the hardness of the tablets could be used to adjust the rate of the release of venlafaxine to the preferred dissolution profile. The hardness factor was especially surprising since usually the properties of Kollidone SR are not affected by the hardness of the tablets.  
         [0030]     The lubricant is selected from magnesium stearate, hydrogenated vegatable oil, glyceryl dibehenate and sodium fumaric acid. Magnesium stearate is preferred.  
         [0031]     For a sustained release tablet formulation containing 37.5 mg venlafaxine, the preferable amount of venlafaxine is HCl is 19-25% w/w, the preferable amount of Kollidone SR is 55-70% w/w and the preferable amount of magnesium stearate is 2-4% w/w.  
         [0032]     For a sustained release tablet formulation containing 75 mg venlafaxine, the preferable amount of venlafaxine HCl is 19-25% w/w, the preferable amount of Kollidone SR is 55-70% w/w and the preferable amount of magnesium stearate is 2-4% w/w.  
         [0033]     For a sustained release tablet formulation containing 150 mg venlafaxine, the preferable amount of venlafaxine HCl is 24-30% w/w, the preferable amount of Kollidone SR is 50-70% w/w and the preferable amount of magnesium stearate is 2-4% w/w.  
         [0034]     In one embodiment the tablet is film-coated.  
         [0035]     The film coated tablet formulation of the present invention comprises:  
         [0000]     a) 15-40% w/w of venlafaxine;  
         [0000]     b) 50-85% w/w of the sustained release agent;  
         [0000]     c) 0.5-5.0% w/w of lubricant;  
         [0000]     and optionally a filler material and/or glidant,  
         [0000]     wherein the tablet is coated with a film wherein the film-forming material is selected from polymethacrylates.  
         [0036]     Several film forming types of polymethacrylates were evaluated, Eudragit NE, Eudragit RL, Eudragit SR 30 D and Eudragit RS powder. Eudragit SR 30 D gave the best result.  
         [0037]     The coating was performed by conventional pan spray coating process using solution containing the Eudragit SR 30 D (30% dispersion in water), titanium dioxide, talc, polyethylene glycol and purified water.  
         [0038]     The time used in the coating process affects the amount of the film on the tablet surface. The amount of the film corresponding to 0.5-3.0% w/w, more preferably 1.0-2.0% w/w showed the most suitable dissolution profile for intended use as a sustained release pharmaceutical.  
         [0039]     The coating solution includes 15-80% w/w Eudragit RS 30 D, 0.5-10% w/w titanium dioxide, 0.5-15% w/w talc, 0.5-10% w/w polyethylene glycol and 00-85% w/w purified water, preferably 30-70% w/w Eudragit RS 30 D, 1.5-6% w/w titanium dioxide, 2-8% w/w talc, 1.5-5% w/w polyethylene glycol and 25-60% w/w purified water, more preferably 45-60% w/w Eudragit RS 30 D, 2-3% w/w titanium dioxide, 3.5-5% w/w talc, 1-3% w/w polyethylene glycol and 30-50% w/w purified water and most preferably 52-54% w/w Eudragit RS 30 D, 2-3% w/w titanium dioxide, 4-5% w/w talc, 1-3% w/w polyethylene glycol and 35-43% w/w purified water.  
         [0040]     The polyethylene glycol is preferably Macrogol 6000.  
         [0041]     Dissolution of venlafaxine can also be adjusted by use of insoluble fillers such as calcium phosphate and microcrystalline cellulose. Calcium hydrogen phosphate dihydrate is preferred.  
         [0042]     Optionally the formulations include glidants such as silica colloid anhydrate.  
         [0043]     The dissolution profiles of the sustained release formulation are independent of the pH of the dissolution medium.  
       EXAMPLES  
       [0044]     The following examples are merely illustrative of the present invention and they should not be considered as limiting the scope of the invention.  
       Example 1  
       [0045]     The following materials were combined by wet granulation to produce 37.5 mg venlafaxine sustained release tablets  
                                                       Venlafaxine HCl   42.5 mg           Kollidone SR   127.5 mg            Magnesium stearate     5 mg                      
 
       Example 2  
       [0046]     The following materials were combined by wet granulation to produce 75 mg venlafaxine sustained release tablets:  
                                                       Venlafaxine HCl   85 mg           Kollidone SR   255 mg            Magnesium stearate   10 mg                      
 
       Example 3  
       [0047]     The following materials were combined by wet granulation to produce 150 mg venlafaxine sustained release tablets:  
                                                       Venlafaxine HCl   170 mg           Kollidone SR   400 mg           Magnesium stearate    20 mg                      
 
       Example 4  
       [0048]     Dissoltion profiles of slow release tablets prepared by the inventors. Dissolution profiles for compositions that include relatively different amounts of kollidone SR.  
                                                                                                       Batch No                        17   18   19   20               Round   Round   Round   Round               tablets   tablets   tablets   tablets           Tablets   mg   mg   mg   mg                            Venlafaxine   42.5   42.5   42.5   42.5           HCl           Kollidone   127.5   152.5   192.5   252.5           Magnesium   5.0   5.0   5.0   5.0           stearate                           Total   175   195   240   300                      
 
         [0049]     Dissolution profiles for tablets having different amount of Kollidon SR but the same amount of venlafaxine HCl and magnesium stearate  
                                                                         Batch No. 17   Batch No. 18   Batch No. 19   Batch No. 20           % dissolved   % dissolved   % dissolved   % dissolved       Time   mean of 6   mean of 6   mean of 6   mean of 6       min   tablets   tablets   tablets   tablets                                0   0.3   0.0   0.0   0.0       30   24.1   24.6   20.5   16.2       60   32.5   32.9   27.5   22.5       120   42.1   42.0   35.2   29.4       180   48.5   47.8   40.2   33.8       240   53.5   52.6   44.0   37.3       300   58.0   56.9   47.1   40.0       360   62.1   60.7   50.0   42.5       420   65.8   64.1   52.9   44.9       480   69.0   67.2   55.4   47.1       540   72.1   70.0   57.8   49.2       600   74.6   72.6   60.2   51.1       660   76.9   74.8   62.2   53.1       720   79.0   76.8   64.2   55.1       780   80.9   78.5   66.2   57.0       840   82.4   80.2   68.0   58.7       900   84.1   81.7   69.6   60.5       960   85.2   82.9   71.3   61.9       1020   86.5   84.1   72.7   63.3       1080   87.5   85.2   74.0   64.7       1140   88.3   86.1   75.3   65.8       1200   89.0   86.9   76.6   67.0       1260   89.7   87.6   77.7   68.0       1320   90.3   88.4   78.9   69.0       1380   90.7   89.0   79.8   69.9       1440   91.1   89.5   80.8   70.9                  
 
         [0050]      FIG. 1  shows the effect of increasing amount of Kollidone SR on the olution rate of venlafaxine HCl  
       Example 5  
       [0051]     Dissolution profiles for tablets that include the same amount of Kollidone SR but the hardness of the tablets is different.  
                                                                 Batch No. 17   Batch No. 17   Batch No. 17           Hardness 40N   Hardness 90N   Hardness 9 173N       Time   % dissolved   % dissolved   % dissolved       min   mean of 6 tablets   mean of 6 tablets   mean of 6 tablets                                0   0   0   0       30   27.8   29.3   27.1       60   38   39.6   36.2       120   50.6   51.4   46.3       180   60.7   59.8   53       240   69   66.8   58.3       300   75.9   73   63       360   81.8   78.5   67.3       420   86.4   83.1   71.1       480   89.9   87.1   74.4       540   92.5   90.5   77.4       600   94.4   93.2   80.1       660   95.6   95.5   82.4       720   96.7   97.4   84.5       780   97.5   98.9   86.4       840   98   100   87.9       900   98.4   101   89.4       960   98.9   101.6   90.7       1020   99.3   102.2   91.9       1080   99.6   102.8   92.9       1140   100   103.1   93.7       1200   100.2   103.5   94.4       1260   100.6   103.9   95       1320   100.9   104.2   95.5       1380   101.1   104.5   96.1       1440   101.4   104.7   96.5                  
 
         [0052]      FIG. 2  shows the effect of increasing the hardness of the tablets on the dissolution profile of venlafaxine 37.5 mg sustained release tablets  
       Example 6  
       [0053]     Dissolution profiles of Venlafaxine sustained release tablets (same batch) are independent of the dissolution medium as shown in following table.  
                                                         % Dissolved   % Dissolved           Batch 14-0.01NHCl   Batch-14-water       Hours   Mean of 6 tablets   Mean of 6 tablets                                0   0.0   0.0       1   27.2   27.5       2   36.8   37.2       3   43.5   43.8       4   48.7   48.9       5   53.1   53.3       6   57.1   57.2       7   60.8   60.8       8   64.2   64.2       9   67.3   67.3       10   70.3   70.2       11   73.0   72.9       12   75.5   75.3       13   77.8   77.6       14   79.9   79.8       15   81.9   81.8       20   89.8   89.7       24   94.3   94.2                  
 
         [0054]      FIG. 3  showes the dissolution profiles.  
       Example 7  
       [0055]     75 mg sustained release venlafaxine tablets were prepared by combining the following materials by wet granulation:  
                                                           Venlafaxine HCl   22%   w/w           Kollidone SR   66.3%   w/w           Magnesium stearate   2.6%   w/w           Calcium hydrogen phosphate dihydrate   8.3%   w/w           Silica colloid anhydrate   0.8%   w/w                      
 
         [0056]     The tablets were coated with Eudragit RS 30 D for different periods of time, resulting in 0.7% w/w film/tablet, 1.0% w/w film/tablet, 1.4% w/w film/tablet and 3.0% w/w film/tablet or not coated at all, for comparison in a dissolution test.  
         [0057]     The coating liquid includes:  
                                                           Eudragit RS 30 D   53.00%   w/w           Titanium dioxide   2.21%   w/w           Talc   4.42%   w/w           Macrogol 6000   1.90%   w/w           Purified water   38.47%   w/w                      
 
         [0058]     Dissolution profiles of uncoated tablets and tablets with different amount of coating.  
                                                                                     Coating   Coating   Coating   Coating               0.7%   1.0%   1.4%   3.0%       Time   Uncoated %   w/w %   w/w %   w/w %   w/w %       [min]   dissolved   dissolved   dissolved   dissolved   dissolved                                0   0.0   0.0   0.0   0.0   0.0       30   21.0   18.7   13.4   10.7   3.1       60   29.9   26.9   21.1   18.5   8.9       120   40.7   37.7   31.2   28.0   20.2       180   48.5   45.3   38.7   34.9   27.7       240   54.5   51.3   44.7   40.5   33.3       300   59.8   56.4   49.7   45.3   38.0       360   64.3   60.8   54.2   49.6   42.2       420   68.4   64.8   58.2   53.4   46.2       480   72.1   68.3   61.9   57.1   49.8       540   75.5   71.6   65.3   60.4   53.1       600   78.5   74.6   68.5   63.5   56.3       660   81.2   77.2   71.4   66.4   59.2       720   83.6   79.6   74.1   69.0   61.9       780   85.7   81.8   76.7   71.5   64.4       840   87.5   83.7   78.9   73.8   66.8       900   89.2   85.4   80.9   75.9   69.0       960   90.6   87.0   82.8   78.0   71.2       1020   91.9   88.3   84.5   79.9   73.1       1080   93.0   89.6   86.0   81.8   74.9       1140   94.4   90.6   87.4   83.5   76.7       1200   95.0   91.6   88.6   84.9   78.3       1260   95.8   92.5   89.7   85.6   79.8       1320   96.5   93.2   90.7   86.8   81.2       1380   97.1   93.9   91.6   87.9   82.5       1440   97.6   94.5   92.5   88.9   83.8                  
 
         [0059]      FIG. 4  shows the dissolution profiles.  
         [0060]     Examples 1-3 show typical compositions of venlafaxine HCl, Kollidone SR and magnesium stearate.  
         [0061]     Example 4 shows different dissolution profiles for various concentrations of Kollidon SR.  
         [0062]     Example 5 shows different dissolution profiles for identical compositions with various hardness of tablets.  
         [0063]     Example 6 shows that the dissolution profiles are independent of the pH.  
         [0064]     Example 7 shows the dissolution profiles of coated and uncoated tablets.  
         [0065]     By using Kollidone SR it was possible to adjust the dissolution profile of venlafaxine to a satisfactory level by changing the amount of Kollidone SR and the hardness of the tablets. By further employing Eudragit RS 30 D as a coating agent the C max  fits the intended critera.