Abstract:
Almokalant (p-INN), 4-[3-]ethyl[3-(propylsulfinyl)propyl]amino[-2-hydroxypropoxy]-benzonitrile, having the formula ##STR1## is a member of a group of compounds useful in the treatment of cardiac arrhythmias. Enhanced stability, palatability, and technical properties of almokalant can be achieved when it is complexed as a salt with polystyrenesulfonic acid. Accordingly, the invention encompasses the almokalant salt and processes for the preparation of said salt. The invention further encompasses solid oral pharmaceutical dosage forms containing the almokalant-polystyrenesulfonate complex as well as methods for their manufacture as medicaments with action against cadiac arrhythmias.

Description:
This application is a Continuation-in-Part of copending patent application Ser. No. 07/539,863 filed Jun. 18, 1990, now U.S. Pat. No. 5,068,272. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a novel polystyrenesulfonate and to processes for its preparation. The invention also relates to solid dosage forms of the antiarrhythmic drug almokalant (p-INN) formulated as immediate release (IR) tablets and extended release (ER) tablets as well as processes for manufacture thereof. 
     More particularly, the present invention relates to the salt of almokalant (p-INN), 4-[3-[ethyl[3-(propylsulfinyl) propyl]amino]-2-hydroxypropoxy]benzonitrile, with polystyrenesulfonic acid, to its preparation, and to its manufacture in solid dosage forms as an agent for treatment of cardiac arrhythmias. 
     BACKGROUND OF THE INVENTION 
     Our prior patent application PCT/SE88/00691, filed on Dec. 20, 1988, relates to a group of novel compounds which are useful in the treatment, acute as well as long term, of cardiac arrhythmias of diverse etiology. Among the compounds included in the group of compounds disclosed in said application is almokalant (p-INN), 4-[3-[ ethyl[3-(propylsulfinyl)propyl]amino]-2-hydroxypropoxy]benzonitrile having the formula ##STR2## which can be obtained as a stereoisomeric mixture as well as in the form of the different stereoisomers, for instance: 
     4-[3-[ethyl[3-(propylsulfinyl)propyl]amino]-2(R)-hydroxypropoxy]benzonitrile, 
     4-[3-[ethyl[3-(propylsulfinyl)propyl]amino]-2(S)-hydroxypropoxy]benzonitrile. 
     The stereoisomeric mixture as well as the above mentioned pure stereoisomers can be obtained by oxidizing the appropriate 4-[3[ethyl[3-(propylthio)-propyl]amino]-2-hydroxy]benzonitrile with m-chloroperbenzoic acid or analogous to methods disclosed in the above mentioned prior patent application. 
     Almokalant in its free base form is an oil. It is a viscous, sticky substance, problematic to handle in the manufacture of solid dosage forms. It has a pronounced tendency to give a repellent odorous degradation product with a smell resembling old onions. No solid dosage forms containing the polystyrene sulphonate complex of almokalant have been reported. The polystyrenesulphonate complex of almokalant is described in the European patent application EP 90850242.0. 
     Several different ways were tested in order to prepare a solid dosage form of almokalant. Commonly used methods had the following disadvantages. 
     Due to the instability of the base and its tendency to worsen tablet binding properties, solid dosage forms of the free base are difficult to produce. See further reference example III. 
     Tablets prepared by conventional technique, with almokalant dissolved in an acidic granulating solution, have inferior stability properties and develop a repelling onion-like odor. See further reference examples I and III. 
     The use of complexes of drug substances with ion exchange resins in pharmaceutical formulation is described previously. A way to obtain a controlled release suspension containing codeine is described by Amsel L.P. et al. &#34;Unique Oral Controlled Release Systems&#34;: In-Vivo Drug Release Pattern pp. 83-93 where a complex between codeine and an ion exchange resin is coated with a diffusion membrane and then formulated into a suspension. In addition, Pennwalt Corporation has published a series of patents describing the use of ion exchange resins having pharmacologically active substances absorbed thereon for use in controlled release preparations either as such or further coated with diffusion membranes (U.S. Pat. No. 4,221,778, EP 0171 528, EP 0 254 811). Other uses of ion exchange resin complexes with drugs in pharmaceutical formulation is for example summarized by Raghunathan et al. J Pharm Sci 1981, 70, (No. 4), 379-384. 
    
    
     DESCRIPTION OF THE INVENTION 
     It has now been found that the salt of almokalant with polystyrenesulfonic acid is a valuable new product having the same basic antiarrhythmic effect as almokalant but being a solid. 
     Accordingly the present invention relates to the salt of almokalant with polystyrenesulfonic acid. 
     According to one embodiment of the salt according to the invention, almokalant is present in the form of a stereoisomeric mixture. 
     According to another embodiment of the present invention almokalant is present in the form of one of the pure stereoisomers. 
     Examples of stereoisomers are, in addition to the two stereoisomers mentioned earlier, the following: 
     4-[3-[ethyl[3-((R*)-propylsulfinyl) propyl]amino]-2(R)-hydroxypropoxy]benzonitrile 
     4-[3-[ethyl[3-((S*)-propylsulfinyl) propyl]amino]-2(R)-hydroxypropoxy]benzonitrile 4-[3-[ethyl[3-((R*)-propylsulfinyl) propyl]amino]-2(S)-hydroxypropoxy]benzonitrile 4-[3-[ethyl[3-((S*)-propylsulfinyl)propyl]amino]-2(S)-hydroxypropoxy]benzonitrile 
     The present invention also relates to a process for the preparation of the salt according to the present invention, which process comprises reacting almokalant with polystyrenesulfonic acid. 
     Polystyrenesulfonic acid is preferably used in the form of small particles. 
     Usually the polystyrenesulfonic acid is crosslinked with divinylbenzene, the degree of crosslinking preferably being 2-10%. 
     According to one embodiment of the process according to the invention small particles of polystyrenesulfonic acid, either in the acid (H + ) form or in the form of a salt with a metal ion suited for ion exchange reactions, e.g. Na + , K +   or Ca 2+ , are added to a solution of almokalant and of a suitable salt of said compound, respectively, in a suitable reaction medium. 
     According to another embodiment of the process according to the invention small particles of polystyrene-sulfonic acid in the form of a salt with a metal ion suited for ion exchange reactions are packed into a column for ion exchange operations and a solution of almokalant in the form of a suitable salt is applied to the column. 
     The invention further relates to a method of preventing or reducing cardiac arrhythmias in mammals, including man, which comprises administering to a host in need of such treatment an effective amount of the salt of almokalant with polystyrenesulfonic acid. 
     The invention yet further relates to the salt of almokalant with polystyrenesulfonic acid for use as a medicament, particularly as an antiarrhythmic agent. 
     The invention also relates to the use of the salt of almokalant with polystyrenesulfonic acid for the manufacture of medicaments with action against cardiac arrhythmias. 
     The following non-limiting examples further illustrate the invention. 
     EXAMPLE 1 
     The polystyrenesulfonate of 4-[3-[ethyl[3-(propylsulfinyl)-propyl]amino]-2-hydroxypropoxy]benzonitrile 
     To a stirred solution of 4-[3-[ethyl[3-(propylsulfinyl)-propyl]amino]-2-hydroxypropoxy]benzonitrile (92.28 g) in methanol (900 ml) was added polystyrenesulfonic acid (63.15 g) at 0° C. under nitrogen atmosphere. Stirring was continued for 18 h. The resin Was filtered, washed With methanol (500 ml), extracted in a Soxhlet extractor at room temperature overnight with ethanol and finally dried under high vacuum to constant weight. Analysis showed 59.3% binding of active substance. 
     EXAMPLE 2 
     The polystyrenesulfonate of 4-[3-[ethyl[3-(propylsulfinyl)-propyl]amino]-2-hydroxypropoxy]benzonitrile 
     To a stirred solution of 4-[3-[ethyl[3-(propylsulfinyl)-propyl]amino]-2-hydroxypropoxy]benzonitrile·HCl (5.5 g) in ethanol:water (1:1) (30 ml) was added sodium polystyrenesulfonate (5 g) at room temperature. After 30 minutes the resin was filtered and washed with ethanol:water (1:1) three times, and dried under high vacuum to constant weight. 
     Analysis showed 32% binding of active substance. 
     EXAMPLE 3 
     4-[3-[ethyl[3-(propylsulfinyl)propyl]amino]-2-hydroxypropoxy]benzonitrile, 2.45 g of 4-[3-[ethyl[3-(propylthio)propyl]amino]-2-hydroxypropoxy]benzonitrile, and 1.4 g p-toluenesulfonic acid were mixed in 50 ml of ethanol. The mixture was cooled to -10° C. and 1.7 g of m-chloroperbenzoic acid was added in small portions. The mixture was stirred for 0.5 hour at -10° C. and one hour at room temperature and then evaporated. The residue was dissolved in dichloromethane and washed with three portions of sodium carbonate and twice with water and thereafter dried over sodium sulfate, filtered and evaporated. The residue, 2.3 g yellow oil, was purified by column chromatography. Yield: 1.4 g of the title compound. 
     NMR:  13  C in CDCl 3  ; 11.21, 11.33, 13.11, 16.02, 20.30, 20.43, 47.41, 47.45, 49.69, 49.95, 52.18, 52.41, 54.29, 54.41, 56.06, 56.09, 66.08, 70.41, 70.49, 103.76, 115.09, 118.83, 113.62, 161.88 ppm 
     EXAMPLE 4 
     4-[3-[ethyl[3-(propylsulfinyl)propyl]amino]-2(R)-hydroxypropoxy]benzonitrile 
     Oxidation of 4-[3-[ethyl[3-(propylthio)propyl]amino]-2(R)-hydroxypropoxy]benzonitrile with m-chloroperbenzoic acid was carried out as described for the stereoisomeric mixture in example 3. 
     [α] 20   D  -18.6° (C=1.0, CH 3  OH). 
     NMR:  13  C in CDCl 3  ; 11.35, 11.47, 13.30, 16.24, 20.47, 20.62, 47.59, 47.63, 49.83, 50.12, 52.30, 52.57, 54.53, 54.66, 56.28, 56.31, 66.13, 70.52, 70.60, 104.08, 115.24, 119.02, 133.85, 162.0 ppm. 
     EXAMPLE 5 
     4-[3-[ethyl[3-(propylsulfinyl)propyl]amino]-2(S)-hydroxypropoxy]benzonitrile 
     The title compound was prepared in analogy with the method described in example 4 and example 3. [α] 20   D  +18.0° (C=1.0, CH.sub. OH). 
     NMR:  13  C in CDCl 3  ; 11.31, 11.43, 13.26, 16.18, 20.41, 20.57, 47.53, 47.58, 49.8, 50.08, 52.26, 52.53, 54.48, 54.61, 56.22, 56.24, 66.09, 70.48, 70.57, 104.0, 115.20, 118.97, 133.79, 161.96 ppm. 
     Any of the isomers prepared according to Examples 4 and 5 may replace the stereoisomeric mixture used in Examples 1 and 2. 
     EXAMPLE 6 
     4-[3-[ethyl[3-((S*)-propylsulfinyl)propyl]amino]-2(R)-hydroxypropoxy]benzonitrile 
     a) Ethyl (3-(S*)-propylsulfinyl)propylamine 
     A hot solution of 27.2 g (0.1 mol) of (-)-1,3,2-dioxaphosphorinane-5,5-dimethyl-2-hydroxy-4-(2-methoxyphenyl)-2-oxide and 17.73 g (0.1 mol) of racemic ethyl (3-propylsulfinyl)-propylamine in 750 ml of acetone and 32.5 ml of methanol was allowed to cool to room temperature, yielding 23.9 g of crystalline material. The experiment was repeated on a 0.25 mol scale, this time yielding 53.0 g of crystals. The combined crops were recrystallized five times from acetone-methanol finally yielding 8.95 g of salt. 
     A solution of 15.6 g (0.0392 mol) of trioctylamine in dichloromethane was shaken with 19.6 ml of 2M hydrochloric acid. The phases were separated and the organic layer was washed with water. The organic phase, now containing trioctylammonium chloride, was stirred for 90 min. with a solution of 8.8 g (0.0196 mol) of the above mentioned resolved salt in water. The phases were separated, and the organic layer was washed with water. The combined aqueous phases were washed with dichloromethane, and then brought to pH 11.5 with 10M sodium hydroxide. Extraction four times with dichloromethane yielded 2.3 g of laevorotatory amine base, arbitrarily denoted S* [α] 20   D  -8.0° (c=1, CH 3  OH). 
       13  C NMR (as salt With (-)-1,3,2-dioxaphosphorinane-5,5-dimethyl-2-hydroxy-4-(2-methoxyphenyl)-2-oxide); in CDCl 3  : 10.80, 12.95, 15.81, 17.55, 19.49, 19.58, 20.41, 36.59, 36.61, 42.37, 45.50, 48.73, 53.67, 54.71, 76.79, 76.83, 77.34, 109.63, 119.69, 126.42, 126.50, 128.33, 128.93, 155.83. 
     b) (R)-4-(oxiranylmethoxy)benzonitrile 
     A solution of 2.71 g of (2S)-1-(4-cyanophenoxy)-3-methanesulfonyloxypropan-2-ol in 40 ml of 1,2-dimethoxyethane was stirred with 1.0 g of powdered sodium hydroxide at room temperature for 22 h, 10 ml of saturated sodium chloride solution was added, and the mixture was extracted twice with ether. Washing with 5% sodium hydrogen carbonate, drying over magnesium sulfate, filtration and evaporation gave 1.76 g of crystalline material, m.p. 67.5° C., 
     [α] 20   D  -14.7° (c=1, acetone). 
     NMR:  13  C in CDCl 3  ; 44.40, 49.71, 69.02, 104.59, 115.34, 118.95, 133.98, 161.66 ppm. 
     c) 4 [3-[ethyl[3-((S*)-propylsulfinyl)propyl]amino]-2(R)-hydroxypropoxy]benzonitrile 
     A mixture of 3 g of ethyl (3-(S*)-propylsulfinyl)propylamine and 3.18 g of (R)-4-(oxiranylmethoxy)benzonitrile was refluxed for 16 h in 25 ml of isopropyl alcohol. After evaporation of the solvent, the crude product was dissolved in 2M hydrochloric acid, washed with ether, the solution brought to pH 11.5 with 2M sodium hydroxide and extracted with dichloromethane. Evaporation of the organic phase gave 6.11 g of an oil, 
       13  C NMR in CDCl 3  : 11.23, 13.17, 16.08, 20.46, 47.41, 49.98, 52.41, 54.46, 56.11, 66.05, 70.50, 103.80, 115.13, 118.92, 133.69, 161.92 ppm. 
     EXAMPLE 7 
     4-[3-[ethyl[3-((R*)-propylsulfinyl)propyl]amino]-2(S)-hydroxypropoxy]benzonitrile 
     a) Ethyl(3-(R*)-propylsulfinyl)propylamine 
     Resolution of racemic ethyl (3-propylsulfinyl)propylamine with (+)-1,3,2-dioxaphosphorinane-5,5-dimethyl-2-hydroxy-4-(2-methoxyphenyl)-2-oxide in analogy with example 1a gave dextrorotatory amine base. This compound, arbitrarily denoted R*, has the following data: [α] 20   D  +7.6° (c=1, CH 3  OH). 
       13  C NMR (as salt With (+)-1,3,2-dioxaphosphorinane-5,5-dimethyl-2 hydroxy-4-(2-methoxyphenyl)-2-oxide); in CDCl 3  : 10.92, 13.07, 15.93, 17.66, 19.56, 19.70, 20.52, 36.72, 36.73, 42.48, 45.61, 48.85, 53.79, 54.82, 76.92, 76.96, 77.45, 77.49, 109.73, 119.81, 126.54, 126.62, 128.44, 129.06, 155.95 
     b) (S)-4-(oxiranylmethoxy)benzonitrile 
     From 2.7 g (2R)-1-(4-cyanophenoxy)-3-methanesulfonyloxypropan-2-ol in analogy with example 1b was obtained 1.75 g crystalline material; m.p. 68.0° C. [α] 20   D  +14.5° (c=1, acetone) 
       13  C NMR in CDCl 3  : 44.21, 49.58, 68.90, 104.25, 115.20, 118.86, 133.80, 161.53. 
     (c) 4-[3-[ethyl[3-((R*)-propylsulfinyl)propyl]amino]-2(s)-hydroxypropoxy]benzonitrile 
     A mixture of 2.3 g of ethyl[(R*)-3-propylsulfinyl]propylamine and 3.18 g of (S)-4-(oxiranylmethoxy)benzonitrile in 19 ml of isopropyl alcohol was refluxed 16 h and thereafter worked up in analogy with 1c yielding 4.1 g of an oil; [α] 20   D  -26.5° (c=1, acetone) 
       13  C NMR in CDCl 3  : 11.16, 13.05, 15.96, 20.37, 47.38, 49.87, 52.37, 54.31, 56.05, 66.10, 70.47, 103.65, 115.06, 118.78, 133.55, 161.86. 
     EXAMPLE 8 
     4-[3-[ethyl[3-((R*)-propylsulfinyl)propyl]amino]-2(R)-hydroxypropoxy]benzonitrile 
     A mixture of 2.3 g of ethyl[(R*)(-3-propylsulfinyl)propylamine and 2.5 g of (R)-4-(oxiranylmethoxy)benzonitrile was refluxed for 16 h in 19 ml of isopropyl alcohol in analogy with example 1c. Traditional workup procedures gave 4.27 g of an oil; [α] 20   D  -13.4° (c=1, CH 3  OH) 
       13  C NMR in CDCl 3  : 11.58, 13.36, 16.29, 20.57, 47.70, 49.96, 52.41, 54.64, 56.36, 66.24, 70.63, 104.18, 115.33, 119.07, 133.91, 162.09. 
     EXAMPLE 9 
     4-[3-[ethyl[3-((S*)-propylsulfinyl)propyl]amino]-2(S)-hydroxypropoxy]benzonitrile 
     A mixture of 2.3 g of ethyl[3-((S*)-propylsulfinyl)propylamine and 2.5 g of (S)- 4-(oxiranylmethoxy)benzonitrile in 19 ml of isopropyl alcohol was refluxed for 24 h in analogy with example 1c. Traditional workup procedures gave 3.65 g of an oil; [α] 20   D  +11.1° (c=1, CH 3  OH). 
       13  C NMR in CDCl 3  : 11.56, 13.33, 16.25, 20.54, 47.71, 49.92, 52.42, 54.53, 56.31, 66.33, 70.64, 104.03, 115.33, 119.06, 133.86, 162.11. 
     A further aim of the present invention is to provide solid dosage forms of the antiarrhythmic drug almokalant, formulated as IR-tablets and ER-tablets with improved stability and minimal odor. ER-tablets can be formulated by a variety of formulation principles, such as hydrophilic gel-matrix tablets, matrix tablets, membrane diffusion controlled formulations, osmotic pressure controlled dosage forms, etc. 
     As the use of solid substances in tablet manufacture in general is advantageous and facilitates the production, different ways to prepare solid dosage forms were investigated. 
     As it had been noticed that almokalant in acidic solutions has a good stability, which makes it possible to autoclave it without noteworthy degradation, the addition of acid compounds was tested. 
     Although complex-binding to ion-exchange resins of viscous, unstable, pharmacologically active agents to form a stable solid complex suitable for pharmaceutical processing has not been previously described, this was tested with almokalant. 
     Thus, it was tested to use the polystyrene sulfonate complex of almokalant in the formulation of pharmaceutical dosage forms. It was then unexpectedly found that almokalant polystyrene sulfonate complex (A-PSS), had a much better stability, less repelling odor and was much easier to handle in tablet manufacture. 
     To form ER tablets it is necessary to mix the formed complex with e.g. a hydrophilic matrix. It is especially preferable to use hydroxypropyl methylcellulose as the gel-forming substance. 
     EXAMPLE 10 
     Immediate release tablets of almokalant were prepared by mixing A-PSS 90 parts, lactose 85 parts, microcrystalline cellulose 91 parts and polyvinyl pyrrolidone 27 parts and then granulating the mixture with purified water. 
     After drying, the granulate was milled and then mixed with sodium stearyl fumarate and compressed to tablets. 
     A reference preparation was produced by dissolving the free base in a 2M hydrochloric acid solution and using this solution to granulate the excipients. 
     
         ______________________________________             A-PSS tablet                       Ref.             Ex 10     Ex I______________________________________1.  A-PSS corresp. to almokalant                   50.0        --    Almokalant          --          50.02.  Lactose pwd         84.5        --    Lactose anhydrous   --          106.8    Avicel ® PH 101 91.3        114.0    Povidone ® K-25 26.8        --    Polyvinyl pyrrolidone,                   --          7.1    cross-linked    Aerosil ®       --          3.63.  Water, purified     105         --    Hydrochloric acid 2M                   --          71.2    (corresp. to HCl)   --          (5.2)4.  Sodium stearyl fumarate                    5.8        --    Magnesium stearate  --          2.9    Talcum              --          11.5    Polyvinyl pyrrolidone,                   --          5.7    cross-linked______________________________________ 
    
     The A-PSS tablet was prepared by first mixing ingredients 1 and 2. The mixture was granulated with 3. After drying and milling, 4 was admixed, whereupon compression to tablets was performed on a Korsch Pharmapress 100. 
     The reference tablet (Ref. ex. I) was prepared by making a granulating solution of the ingredients 1 and 3. The powders in 2 were mixed and then granulated with the prepared solution. After drying and milling, the lubricant, glidant and disintegrant in 4 were admixed and tablets compressed on the same machine. 
     
         ______________________________________         A-PSS tablet                    Ref.         Ex 10      Ex I______________________________________Punches:         9 mm         10 mmTablet weight:  298 mg       307 mgHardness:        7.5 kP       6.7 kPDisintegration:  1-2 min.     1-2 min.Stability data of storage in glassbottles. Degradation measured as areasum of byproducts in a HPLC-system0 month          0.81         2.111 month in 25° C.            0.88         2.831 month in 50° C.            1.82         3.413.5 months in 25° C.            0.88         2.87______________________________________ 
    
     EXAMPLE 11 
     Immediate release tablets of almokalant were prepared by mixing A-PSS 90 parts, lactose 85 parts, microcrystalline cellulose 91 parts and polyvinyl pyrrolidone 27 parts and then granulating the mixture with purified water. 
     After drying, the granulate was milled and then mixed with the lubricant sodium stearyl fumarate whereupon compression to tablets was done. 
     A reference preparation (Ref. ex. II) was produced by dissolving the free base in an aqueous tartaric acid solution and using this solution to granulate the excipients. 
     
         ______________________________________            A-PSS tablet                     Ref. tablet            Ex 11    Ex II______________________________________1.  A-PSS corresp. to almokalant                   50.0       --    Almokalant          --         50.02.  Lactose pwd         84.5       --    Lactose anhydrous   --        110.7    Avicel ® pH 101                   91.3      114.3    Polyvidone ® K-25                   26.8       --3.  Water, purified    105         57.1    Tartaric acid       --         21.54.  Sodium stearyl fumarate                   5.8        6.0    Talcum              --         12.0    Polyvinyl pyrrolidone,                   --         12.0    cross-linkedPunches:            9 mm       10 mmTablet weight:     298 mg     331 mgHardness:           7.5 kP     5.9 kPDisintegration:     1-2 min.   8 min.______________________________________ 
    
     The A-PSS tablets were prepared by first mixing ingredients 1 and 2. The mixture was granulated with 3. After drying and milling 4 was admixed, whereupon compression to tablets was performed on a Korsch Pharmapress 100. 
     The reference tablet (Ref. ex. II) was prepared by making a granulating solution of 1 and 3. The powders in 2 were mixed and granulated with the solution. After drying and milling, the lubricant, glidant and disintegrant in 4 were admixed and tablets were compressed on the same machine. 
     The odor intensities of the two formulations were compared immediately after manufacturing and after 1 month of storage in glass bottles. 
     
         ______________________________________Odor intensity     A-PSS tablet                 Ref. tablet     Ex 11       Ex II______________________________________Freshly prepared       +             ++       (some smell, but                     (pronounced smell       not of onions.)                     of onions.)1 month     +             +++       (some smell, but                     (strong smell of       not of onions.)                     onions.)______________________________________ 
    
     EXAMPLE 12 
     Immediate release tablets of almokalant can be prepared in suitable strengths. 
     In Ex. 10 and 11 a 50 mg preparation was described. Below are examples of 70 mg and 1.8 mg preparations shown. 
     
         ______________________________________                Ex 12a                      Ex 12b                70 mg 1.8 mg______________________________________1.     A-PSS               127     3.3  Avicel ® PH 101 148     29  Polyvidone ® K-90                       35     --2.     Polyvidone ® K-90                       10     --  Polyvidone ® K-25                      --      4.7  Water, purified     161     193.     Avicel ® PH 102 coarse grade                      --      107  Polyvinyl pyrrolidone,                      --      4.3  cross-linked  Sodium stearyl fumarate                         1.6  1.4______________________________________ 
    
     The A-PSS tablets were prepared by first mixing the ingredients in 1. The mixture was granulated with a solution made of the ingredients in 2. After drying and milling the ingredients in 3 were admixed, whereupon compression to tablets was performed on a Korsch Pharmapress 100. 
     
         ______________________________________Punches:       10 mm       5.5 × 10.5 mmTablet weight:         322 mg      150 mgHardness:      9-10 kP     9-10 kPDisintegration          0.6-1.0 min.                      0.2-0.4 min.(without discs):______________________________________ 
    
     EXAMPLE 13 
     Extended release tablets of almokalant were prepared by mixing A-PSS 95 parts, hydroxypropyl methylcellulose (HPMC) 50 cps 40 parts, HPMC 10000 cps 160 parts and hydroxypropyl cellulose (HPC) 50 parts and then granulating the mixture with 99.5% ethanol. After drying, the granulate was milled and then mixed with sodium stearyl fumarate whereupon compression to tablets was done. 
     A reference preparation (Ref. ex. III) was made by dissolving the free base in ethanol (99.5%) and using this solution to granulate the dry excipients, and otherwise following the same method of production. 
     
         ______________________________________                Example 13                          Ref. ex. IIIIngredient           mg/tablet mg/tablet______________________________________1.  A-PSS corresp. to almokalant                    50.0      --    Almokalant           --        50.02.  HPMC 50 cps          40.0      40.0    (Metolose ® 60SH50)3.  HPMC 10000 cps       160.00    160.00    (Methocel ® E10MCR)4.  HPC LF (Klucel ® LF)                    50.0      50.05.  Ethanol 99.5%        261       2356.  Sodium stearyl fumarate (Pruv ®)                    3.3       3.3______________________________________ 
    
     Ingredients 1 to 4 were mixed. The mixture was granulated with ethanol. After drying and milling the granulate was mixed with 6. 
     Compression to tablets was performed on a Korsch Pharmapress 100 with 11 mm circular punches. The tablet machine was equipped with compression force registration. 
     
         ______________________________________Tablet weight:     348 mg     303 mgTablet compression force:               8.6 kN     12.3 kNTablet hardness:    5.5 kP     3.7 kP______________________________________ 
    
     Tablets made using the free base have inferior binding properties. 
     
         ______________________________________Odor intensity       A-PSS tablets                  Reference tablet       (Ex. 13)   (Ref. ex. III)______________________________________Freshly prepared         +            +++         (some smell, but                      (strong smell         not of onions.)                      of onions.)______________________________________ 
    
     The release rate was determined from 6 individual tablets using USP dissolution apparatus 2 with the paddle rotating at 100 rpm and the tablet placed in a stationary basket above the paddle. 500 ml buffer solution pH 6.8 kept at 37° C. was used as dissolution medium. 
     
         ______________________________________     A-PSS tablet   Ref. tablet     (Ex. 13) cumulative                    (Ref. ex. III)     % released     cumulative % releasedhours     average (min-max)                    average (min-max)______________________________________2         15 (14-15)      28 (28-29)4         24 (23-25)      43 (42-43)6         34 (33-35)      55 (54-56)10        51 (48-52)      74 (72-75)24        91 (87-93)     102 (100-105)______________________________________ 
    
     EXAMPLE 14 
     Extended release tablets of almokalant can be prepared in suitable strengths and with different release rates. 
     In Ex. 13 a preparation with 50 mg strength is described. Below follow examples of 10 mg and 100 mg. 
     
         ______________________________________                 mg/tablet                   10 mg   100 mgIngredient              Ex. 14a Ex. 14b______________________________________1.  A-PSS corresp. to almokalant                       10.0    100.02.  Lactose pwd             100.0   40.0    HPMC 50 cps (Metolose ® 60SH50)                       27.6    39.2    HPMC 10000 cps (Methocel ® E10MCR)                       110.4   146.4    HPC LF (Klucel ® LF)                       25.0    --3.  Polyethylene glycol 20M 30.0    --    (Carbowax ® 20M)    Polyethylene glycol 6000                       --      42.0    (Carbowax ® 6000)4.  Water, purified         70.0    98.16.  Sodium stearyl fumarate (Pruv ®)                       1.6     2.3______________________________________ 
    
     1 and 2 were mixed. The mixture was granulated with a solution made of 3 and 4. After drying and milling the granulate was mixed with 5. 
     Compression to tablets was performed on a Korsch Pharmapress 100. The tablet machine was equipped with compression force registration. 
     
         ______________________________________Punches, diameter:    10 mm     11 mmTablet weight:       314 mg    459 mgTablet compression force (kN):                 11.0      11.4Tablet hardness (kP):                 8.2       5.4______________________________________ 
    
     The release rate was determined from 6 individual tablets using USP dissolution apparatus 2 with the paddle rotating at 100 rpm and the tablet placed in a stationary basket above the paddle. 500 ml buffer solution pH 6.8 kept at 37° C. was used as dissolution medium 
     
         ______________________________________    10 mg ER tablet 100 mg ER tablet    Ex. 14a         Ex. 14b    cumulative      cumulative    % released      % releasedhours    average (min-max)                    average (min-max)______________________________________ 2        27 (27-28)      17 (17-18) 4        44 (43-45)      28 (26-29) 6         --             37 (35-39) 8        72 (70-75)       --10         --             55 (52-56)12       105 (96-109)      --20         --             91 (84-95)24         --            100 (99-101)______________________________________ 
    
     DISCUSSION 
     From the examples it is quite obvious that the use of almokalant free base in pharmaceutical formulation-- apart for the inconvenience of handling a sticky viscous substance--results in dosage forms with inferior stability and palatability as well as in inferior technical properties. The use of almokalant-polystyrenesulfonate complex in pharmaceutical formulation eases the handling and results in more stable and more palatable dosage forms. 
     The best mode of carrying out the invention known at present is to prepare the formulation according o Example 14.