SLOW-RELEASE PHARMACEUTICAL COMPOSITION

Abstract: A slow-release pharmaceutical composition which com­ prises fumaric acid and/or DL-tryptophan in addition to one or more pharmaceutically active substances, and a process for preparing the same are disclosed. Among many organic acids and amino acids, fumaric acid and DL-tryptophan are remark­ ably useful for extending the duration of release of a pharmaco­ logically active substance when fumaric acid, DL-tryptophan or both are used for the formulation of a pharmaceutical compo­ sition. The pharmaceutical composition may be in any solid form of formulations such as powder, granule, tablet, troche, capsule, suppository, etc., and may be used with practically all types of drugs.

Description: While many compounds are known to be useful as pharmacologically active substances, some of them have a relatively short biological half life and must be administered several times a day in order to exhibit their full action. However, a decrease in the number of administrations will not only reduce the burden on the patient but will also increase his compliance and thus provide greater therapeutic effects. In order to meet this requirement, medicines must release their active ingredients slowly so that they maintain effective levels in the blood for a prolonged period of time. Various techniques have been proposed for preparing slow-release pharmaceutical compositions that are capable of retaining the concentrations of their active substances in the blood for a prolonged period of time. Most of the slow-release pharmaceuticals so far proposed employ a variety of high-molecular weight materials which include: hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl methyl cellulose phthalate, pullulan, gelatin, collagen, casein, agar, gum arabic, dextrin, ethyl cellulose, methyl cellulose, chitin, chitosan, mannan, carboxymethylethyl cellulose, sodium carboxymethyl cellulose, polyethylene glycol, sodium alginate, poly(vinyl alcohol), cellulose acetate, poly(vinylpyrrolidone) silicone, poly(vinyl acetal) diethylamino acetate and albumin [see Sustained and Controlled Release Drug Delivery Systems, Marcel Dekker, Inc., 1978; Yakkyoku (Pharmacy), vol. 35, No. 2, pp 575 - 583, 1984; and Japanese Patent Public Disclosure No. 62521/1984]. The use of the above-listed high-molecular weight materials in manufacturing slow-release pharmaceuticals has several problems: (1) many high-molecular weight materials, particularly those which are soluble in water, have such a high moisture content that the pharmacologically active substances incorporated therein are liable to suffer decomposition, such as by hydrolysis, and often fail to withstand prolonged storage; (2) high-molecular weight materials have distributions in molecular weight and their molecular weight distribution and average molecular weight generally differ from one to another notwithstanding the existence of certain limits to be complied with and, therefore, the slow-release pharmaceuticals employing such high-molecular weight materials will experience considerable variations in the drug dissolution rate no matter how strict the quality control is during the manufacturing process; (3) some of the slow-release pharmaceuticals employing high-molecular weight materials are used while they are implanted in the human body, but many high-molecular weight materials are not decomposed in the human body at all or are decomposed only slightly, and therefore have to be removed from the human body after they have liberated the pharmaceutically active substance; even the high-molecular weight materials that are decomposable in the human body are in most cases dependent on the presence of decomposition enzymes if the rate of their decomposition is to be satisfactory, and this applies to the rate of release of the active substance too; furthermore, even the decomposable high-molecular weight materials are not completely decomposed to monomers and there is a high possibility that only a part of them are decomposed, most of them remaining as polymers and being absorbed by tissues to become a potential antigen capable of causing an anaphylactic shock [see Seiyaku Kojo (Pharmaceutical Factory), vol. 13, No. 10, pp. 552 - 557 (1983); and Kagaku no Ryoiki (Region of Chemistry), Special Issue, No. 134, pp. 151 - 157, Nankodo]; and (4) in slow-release pharmaceuticals of the matrix type and those wherein the active substances (i.e., drugs) are released through a semipermeable membrane, the drug release rate is so highly dependent on the solubility of the drug that such types of slow-release pharmaceuticals are not suitable for use with sparingly soluble drugs. US-A-3 577 491 discloses an improvement in the process of compressing powdered tabletable compositions by mixing fumaric acid with said composition prior to compression. The fumaric acid acts as a surfaced lubricant and an internal compression lubricant. Preferred is an amount from 5 - 14 wt% fumaric acid. In EP-A- O 121 901 the provision of novel pH-independent, controlled release oral tablets comprising an effective amount of an intimate mixture of dipyridamole or an acid addition salt thereof is described. At least 18 acid equivalents of at least one non-toxic, pharmaceutically acceptable acid such as fumaric acid or acid substance per mole of dipyridamole and a sufficient amount of a disintegration agent are admixed to allow at least 90 % dissolution of dipyridamole in the gastrointestinal pH range of 1 to 7. DE-A-2 841 170 describes the provision of a pharmaceutical composition acting as a hypnotic agent requiring a lower dose of L-tryptophan which is used together with at least one compound blocking the linkage to serum protein, or cleaning said linkage, respectively, and at least one compound suppressing the activity of L-tryptophan pyrolase. It is the object of the present invention to provide pharmaceutical composition which will slowly release its active ingredient over a period of time and which is free from the aforementioned problems of the prior art products. This object could be achieved by the surprising finding that the duration of the sustained release of a pharmaceutically active substance can be extended significantly by employing DL-tryptophan or a mixture of fumaric acid and DL-tryptophan, both of which are low-molecular weight materials. However, it was found that no such prolonging effect could be attained by organic acids other than fumaric acid such as citric acid, maleic acid, succinic acid, tartaric acid and malic acid, or amino acids other than DL-tryptophan such as L-valine, L-tryptophan, DL-methionine, L-methionine, L-phenylalanine, L-isoleucine, L-leucine and L-glutamic acid. The subject matter of the invention therefore is a slow-release pharmaceutical composition which comprises DL-typtophan or a mixture of fumaric acid and DL-tryptophan in addition to one or more pharmacologically active substances. DL-tryptophan or a mixture of Fumaric acid and DL-tryptophan are preferably present in an amount of at least 10 wt% of the total weight of the composition. In a preferred embodiment the composition chiefly comprises DL-tryptophan and one or more pharmaceutically active substances. In another preferred embodiment the composition chiefly comprises fumaric acid, DL-tryptophan and one or more pharmacologically active substances. Nicorandil is a preferred pharmaceutically active substance in the two above-mentioned embodiments. The slow-release pharmaceutical composition according to the invention may be a layered tablet consisting of a layer containing a pharmacologically active substance and a layer which does not contain any pharmaceutically active substance. A slow-release multiple-layered tablet of the invention may be prepared by compressing a layer having the composition recited above and a fast-release layer containing the same pharmacologically active substance as present in the first layer. Another slow-release multiple-layered tablet of the invention may be prepared by compressing a layer having the composition recited above, a layer composed of DL-tryptophan or a mixture of fumaric acid and- DL-tryptophan, and a fast-release layer containing the same pharmacologically active substance as present in the first layer. A slow-release granule of the invention is composed of a granulation having the composition recited above. It may comprise in addition a fast-release granulation containing the same pharmacologically active substance as present in the first granulation. The slow-release granule composed of a granulation having the composition recited above can be coated with an enteric base or with a water-insoluble base. Also, the slow-release granule comprising the granulation having the composition recited above which is coated with an enteric base or with a water-insoluble base may comprise in addition a fast-release granulation containing the same pharmacologically active substance as present in the first granulation. A further subject matter of the invention is a slow-release granule wherein a fast-release granulation of a pharmacologically active substance is coated with DL-tryptophan or a mixture of fumaric acid and DL-tryptophan. A further subject matter of the invention is a slow-release capsule which is filled with the slow-release granules having the composition recited above. A further subject matter of the invention is a slow-release tablet prepared by compressing a powder or a granulation having the composition recited above. The slow-release tablet may also be prepared by compressing a mixture of a granulation having the composition recited above and a water-insoluble base. A further subject matter of the invention is a slow-release tablet wherein a tablet prepared by compressing a granulation having the composition recited above or a powder having the composition recited above is coated with an enteric base. Still a further subject matter of the invention is a slow-release tablet wherein a tablet prepared by compressing a granulation having the composition recited above or a powder having the composition recited above is coated with a water-insoluble base. A sugar-coated slow-release tablet according to the invention is a tablet having the composition recited above and being surrounded by a sugar coat. In another sugar-coated slow-release tablet of the invention a tablet having the composition recited above is surrounded by a sugar coating containing the same pharmacologically active substance as present in said center tablet. A core/shell slow-release tablet according to the invention has a core which is a tablet having the composition recited above with a shell being compressed around said core tablet, said shell being made of a fast-release composition containing the same pharmacologically active substance as present in said core tablet. In another core/shell slow-release tablet of the invention the core is a tablet having the composition recited above with two shells being compressed around said core tablet, the first shell around said core tablet being made of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan, and the second shell around said first shell being made of a fast-release composition containing the same pharmacologically active substance as present in said core tablet. In a slow-release suppository of the invention a granulation having the composition recited above is incorporated in a suppository base. In another slow-release suppository of the invention a tablet having the composition recited above is coated with a suppository base. Fig. 1 depicts the dissolution profiles of the granules prepared in Example 1, the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 2 depicts the dissolution profiles of the enteric granules prepared in Example 2, the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 3 depicts the dissolution profiles of the capsules prepared in Example 3, the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 4 depicts the dissolution profile of the tablets that were prepared in Example 4 and which were implanted under the dorsal skin of rats; Fig. 5 depicts the dissolution profiles of the enteric tablets prepared in Example 6, the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 6 depicts the dissolution profiles of the tablets prepared in Example 7 (--) and of the comparative tablets (-o-); Fig. 7 depicts the dissolution profiles of the tablets prepared in Exmaple 8-(a), the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 8 depicts the dissolution profiles of the tablets prepared in Example 8-(b), the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 9 depicts the dissolution profiles of the tablets prepared in Example 8-(c), the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 10 depicts the dissolution profiles of the tablets prepared in Example 10, the profile of dissolution in Fluid 1 being indicated by -- and that in Fluid 2 by -o-; Fig. 11 depicts the dissolution profiles of the suppositories prepared in Example 11 (--) and of the comparative suppositories (-o-); and Fig. 12 depicts the dissolution profiles of the tablets prepared in the Reference Example, the profile of dissolution in Fluid 1 being indicated by --, that in Fluid 2 by -o-, and that in distilled water by -▵-. The slow-release pharmaceutical composition of the present invention is prepared by the following procedures: predetermined amounts of a pharmacologically active substance and an excipient are weighed; predetermined amounts of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan are weighed; and the individual components are mixed by a routine method. The use of an excipient is optional but if one is used, preferable excipients are lactose, mannitol, inositol, calcium citrate, dibasic calcium phosphate, hardened oils, and stearic acid. The desirable effect of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan is attained if they are used in an amount of at least 10% of the total weight of the pharmaceutical composition. The slow-release pharmaceutical agent of the present invention may be used with practically all types of drugs such as hypotensives, antipyretic analgesic antiinflammatories, immunoregulators, adrenocortical hormones, antidiabetic agents, vasodilators, cardiotonics, antiarrhythmic agents, anti-arteriosclerotic agents and antidotes. To the mixed powder containing the pharmacologically active substance, DL-tryptophan or a mixture of fumaric acid and DL-tryptophan and optionally an excipient, a lubricant such as magnesium stearate, calcium stearate or talc, and any other necessary components are added and the resulting mixture is compressed into tablets. If desired, the mixture may be worked into a dosage form suitable for implanting in the human body. The mixed powder may also be blended with sucrose, a fragrance, a colorant and any other appropriate components and the resulting blend is then compressed to form troches of predetermined shapes. If desired, the blend may be formulated as a pharmaceutical for buccal administration. A layer (A) containing a pharmaceutically active substance may be placed on another layer (B) containing no such active substance and the two layers are then compressed together to form a double-layered tablet which achieves enhanced delivery of the effective substance after a given period of time has passed. Two modifications of this multiple-layered tablet are as follows: a tablet which is prepared by compressing a layer having the composition specified by the present invention and a fast-release layer containing the same pharmacologically active substance; and a tablet prepared by compressing the following three layers: the first layer having the composition specified by the present invention, the second layer consisting of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan, and and the third layer being a fast-release layer containing a pharmacologically active substance which is the same as the one present in the first layer. The mixed powder described above may be blended with an appropriate binder, such as hydroxypropyl cellulose, hydroxypropyl methyl cellulose or corn starch, dissolved in either water or an organic solvent, and the blend is granulated, dried and classified to obtain granules. If desired, a granulation having this composition may be mixed with a fast-release granulation containing the same pharmacologically active substance. Slow-release enteric granules may be prepared by coating the first granulation with enteric bases such as hydroxypropyl methyl cellulose phthalate and carboxymethylethyl cellulose. These enteric slow-release granules may be mixed with fast-release granules containing the same pharmacologically active substance. Said first granulation may be coated with water-insoluble bases and the so coated granules may optionally be mixed with fast-release granules containing the same pharmacologically active substance. The fast-release granules containing a pharmacologically active substance may be coated DL-tryptophan or a mixture of fumaric acid and DL-tryptophan to convert them into slow-release granules. If desired, these slow-release granules may be compressed to form slow-release tablets. Mixtures of said granules with water-insoluble bases may be compressed into tablets and the so formed tablets may be coated with enteric bases or water-insoluble bases. These tablets may be provided with a sugar coating which may optionally contain a pharmacologically active substance of the same type as incorporated in the center of the tablets. Core/shell type slow-release tablets may be prepared by compressing the aforementioned tablets after they have been coated with a fast-release composition containing the same pharmacologically active substance. In this case, a coat of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan may be provided between the core tablet and the shell of the fast-release composition. Any type of the aforementioned granules may be encapsulated to formulate capsules. If desired, the aforementioned slow-release granules may be incorporated in suppository bases to form slow-release suppositories. Alternatively, slow-release suppositories may be prepared by coating the aforementioned slow-release tablets with suppository bases. Fumaric acid and DL- tryptophan to be incorporated in the slow-release pharmaceutical agent of the present invention may be used as a mixture of appropriate proportion of DL-tryptophan only. By properly adjusting the mixing proportions of fumaric acid and DL-tryptophan, the dissolution rate of a pharmacologically active substance may be increased in an acidic environment and decreaed in a near-neutral environment or vice versa. It is also possible to maintain a substantially constant dissolution rate at all pHs of the environment. Therefore, the drug release of the pharmaceutical agent of the present invention can be controlled by properly adjusting the ratio of fumaric acid to DL-tryptophan. The slow-release pharmaceutical composition of the present invention released its active substance as DL-tryptophan or a mixture of fumaric acid and DL-tryptophan is slowly lost, so the pharmacologically active substance that can be incorporated may be water-soluble or sparingly water-soluble and is not limited to any particular type. It should of course be understood that in putting the slow-release pharmaceutical composition of the present invention to use, colorants, flavoring agents, stabilizers and any other appropriate additives may be added as required. The present invention is hereunder described in greater detail with reference to working examples and a reference example, to which the scope of the invention is by no means limited. A blender was charged with 750 g of indomethacin, 1050 g of DL-tryptophan and 1140 g of the hardened oil (hydrogenated soybean oil) and mixing was conducted for 10 minutes. Thereafter, 600 g of an ethanol solution of 10% ethyl cellulose (ETHOCEL 10CPS of Dow Chemical) was added and blending was conducted for additional 10 minutes. The blend was granulated in a rotary granulator equipped with a net (1.0 mm ⊘ ), dried at 45°C in a tray dryer for 6 hours, and classified on a 12-mesh sieve to make granules. The granules had the dissolution profiles shown in Fig. 1 that were obtained by conducting a dissolution test on 100 mg of the granules with an apparatus of the type specified in "Method I (rotary basket method)", Japanese Pharmacopoeia, 10th rev.; 500 ml each of Fluid 1 (pH 1.2) and Fluid 2 (pH 6.8) was used as testing fluids and the basket was rotated at 100 rpm. Example 2 Two thousand five hundred grams of the granules prepared in Example 1 were coated with 15% (w/w), based on the granules, of 6% hydroxypropyl methyl cellulose phthalate (HP-55 of Shinetsu Chemical Industry Co., Ltd.) dissolved in a 1:1 mixture of methylene chloride and ethanol. The coating machine used was a Flow Coater FLO-5 of Okawara Mfg. Co., Ltd. The so prepared enteric granules had the dissolution profiles depicted in Fig. 2 which were obtained by conducting a dissolution test on 115 mg of the enteric granules in accordance with the same method as employed in Example 1. Example 3 Three hundred grams of the granules prepared in Example 1 and 805 g of the enteric granules obtained in Example 2 were mixed in a polyethylene bag and charged in No. 2 capsules in such a manner that each capsule contained 110.5 mg of the mixed granules. The resulting capsules had the dissolution profile shown in Fig. 3 which was obtained by conducting a dissolution test as in Example 1 except that Fluid 1 was employed for the first two hours of the test while Fluid 2 was used thereafter. To 1 g of phenobarbital, 99 g of DL-tryptophan was added in small amounts and mixed in a mortar. The mixed powder was fed into a single-punch tableting machine equipped with a die (7 mm ⊘ ) and flat-faced punches, and compressed at a total pressure of 1.5 tons so as to make tablets each weighing 100 mg. The time-dependent dissolution profile of the tablets implanted under the dorsal skin of rats is shown in Fig. 4. In obtaining the data shown in Fig. 4, the tablets were implanted at four different positions under the dorsal skin of each of the four rats tested and, at predetermined intervals, the tablets were taken out of the rats and the residual amount of phenobarbital in each tablet was measured. No formation of fibers around the tablets was observed. After 14 days of implanting, there was no indication at all of the presence of phenobarbital or DL-tryptophan under the dorsal skin of the rats upon visual observation. Aminopyrine (3 g), Polyethylene glycol 6000 (17 g) and DL-tryptophan (25 g) were well mixed in a polyethylene bag. The mixed powder was fed into a single-punch tableting machine equipped with an oval die (major axis, 8 mm; minor axis, 3 mm) and punches, and compressed at a total pressure of about 0.6 tons so as to make tablets weighing 45 mg each. Comparative tablets were prepared by the same procedures except that DL-tryptophan was replaced by Polyethylene glycol 6000. The tablets of the present invention and the comparative samples were administered to the rectum of five rats which had fasted for 24 hours. The tablets were not excreted in the following 12 hours. On the next day, the tablets of the present invention were excreted in small amounts of the rats' feces, but the rats to whom the comparative tablets had been administered did not excrete the tablets and merely excreted a small amount of feces. The comparative tablets must have been dissolved away since they were not found in the digestive tracts of the autopsyed animals either. The size of the tablets of the present invention had been reduced by about half their initial size and the residual aminopyrine content was 48.9 ± 4.2%. A blender was charged with 3,425 g of DL-tryptophan and 500 g of stearic acid and mixing was conducted for 10 minutes. Thereafter, 500 g of an aqueous solution of 10% hydroxypropyl cellulose (NISSO HPC-L of Nippon Soda Co., Ltd.) was added and blending was conducted for additional 10 minutes. The blend was granulated after passage through a 32-mesh sieve, dried at 45°C in a tray dryer for 6 hours and classified on a 32-mesh sieve to obtain fine granules. These fine granules (3,975 g ) were mixed well with 500 g of Nicorandil and 25 g of magnesium stearate in a polyethylene bag. The mixture was fed into a rotary tableting machine (Model RT-15-H1 of Kikusui Seisakusho, K.K.) equipped with a die (6 mm ⊘ ) and sugar-coated round punches (radius, 4.5 mm), and compressed at a sufficient pressure to form tablets each weighing 90 mg. Four thousand grams of the tablets were fed into a "Perfect coater" (Model PTC-10 of Okawara Mfg. Co., Ltd.) and treated with a coating solution of the following composition so that each tablet would be given a 10-mg coat. The resulting enteric tablets had the dissolution profile shown in Fig. 5 which was obtained by conducting a dissolution test as in Example 3. Acetylsalicylic acid (100 g), fumaric acid (100 g), DL-tryptophan (98 g) and magnesium stearate (2 g) were mixed in a polyethylene bag. The mixed powder was fed into a single-punch tableting machine equipped with a die (10 mm ⊘ ) and flat-faced punches, and compressed at a total pressure of about 1.8 tons so as to form tablets each weighing 300mg. Comparative tablets were formed by repeating the same procedures except that fumaric acid and DL-tryptophan were replaced by methyl cellulose (Metlose® SM-8000 of Shinetsu Chemical Industry Co., Ltd.) The two types of tablets had the dissolution profiles shown in Fig. 6 which were obtained by conducting a dissolution test with an apparatus of the type specified in the "Method of Disintegration Test", the Japanese Pharmacopoeia, 10th rev.; distilled water was used as a testing fluid. In order to examine the stability of each type of tablet, an accelerated aging test was conducted by the following two methods: in one method, the tablets were put in stoppered glass containers and left to stand at 40°C for 3 months; in the other method, the tablets were put in open glass containers and left to stand in a desiccator for 3 months at 40°C and at 61.5% r.h. The results are shown in Table 1. Isosorbitol nitrate (20 g), fumaric acid (90 g), DL-tryptophan (10 g), calcium citrate (29 g) and calcium stearate (1 g) were mixed in a polyethylene bag. The mixed powder was fed into a single-punch tableting machine equipped with a die (8 mm ⊘ ) and flat-faced punches, and compressed at a total pressure of about 1.2 tons so as to provide tablets each weighing 150 mg [Example 8-(a)]. Isosorbitol nitrate (20 g), fumaric acid (70 g), DL-tryptophan (30 g), calcium citrate (29 g) and calcium stearate (1 g) were mixed in a polyethylene bag. As in Example 8-(a), the mixed powder was compressed into tablets [Example 8-(b)]. Isosorbitol nitrate (20 g), fumaric acid (50 g), DL-tryptophan (50 g), calcium citrate (29 g) and calcium stearate (1 g) were mixed in a polyethylene bag. As in Example 8-(a), the mixed powder was compressed into tablets [Example 8-(c)]. The tablets prepared in Examples 8-(a), 8(b) and 8-(c) had the dissolution profiles shown in Figs. 7, 8, and 9, respectively. The data shown in these figures were obtained by conducting dissolution tests with an apparatus of the type shown in "Method II (puddle method) of Dissolution Test", the Japanese Pharmacopoeia, 10th rev.; 500 ml each of Fluid 1 (pH ≃ 1.2) and Fluid 2 (pH ≃ 6.8) was used as testing solution , and the puddle was rotated at 100 rpm. The graphs in Figs. 7 to 9 show that the rate of drug dissolution in the stomach or intestines can be freely controlled by adjusting the mixing proportions of fumaric acid and DL-tryptophan. Chlorhexidine hydrochloride (5 g), fumaric acid (30 g) and DL-tryptophan (122 g) were well mixed in a mortar. Thereafter, 60 g of an aqueous solution of 5% hydroxypropyl cellulose (Nisso HPC-L of Nippon Soda Co., Ltd.) was added and intimate blending was conducted. The blend was granulated by sifting through a 14-mesh sieve, dried at 50°C in a tray dryer for 4 hours, and classified for 10 mesh. The granulation was fed into a single-punch tableting machine equipped with a die (8 mm ⊘ ) and flat-faced punches, and compressed at a total pressure of about 1.5 tons so as to make troches each weighing 160 mg. The so prepared troches melted slowly in the mouth over about 3 hours. Nicorandil (15 g), fumaric acid (94 g), DL-tryptophan (40.5 g) and magnesium stearate (0.5 g) were mixed in a polyethylene bag. The mixed powder was fed into a single-punch tableting machine equipped with a die (8 mm ⊘ ) and flat-faced punches, and compressed at a total pressure of 1.2 tons so as to form tablets each weighing 150 mg. These tablets had the dissolution profile showing in Fig. 10 which was obtained by conducting a dissolution test as in Example 8. Fifty grams of aminopyrine (under 35 mesh), 400 g of DL-tryptophan and 135 g of crystalline cellulose were mixed well in a mortar. Thereafter, 300 g of an aqeuous solution of 5% hydroxypropyl methyl cellulose (TC-5-E of Shinetsu Chemical Industry Co., Ltd.) was added and blended with the previously obtained mixture. The resulting blend was granulated in a rotary granulator equipped with a net (0.7 mm ⊘ ). The granules were spheroidized with a Marumerizer machine (Model Q-236 of Fuji Powdal K.K.), dried at 50°C in a tray dryer for 4 hours and classified on a 12-mesh sieve to obtain pellets. One hundred and forty grams of Novata E (Henkel Corporation) was melted at 60°C and 60 g of the abovprepared pellets were dispersed in the melt. The resulting dispersion was cast into a mold and cooled slowly to form suppositories each weighing 2 g. Novata E (195 g) was melted at 60°C and 5 g of aminopyrine was dispersed. The dispersion was cast into a mold and cooled slowly to form suppositories each weighing 2 g. The two types of suppositories had the dissolution profiles shown in Fig. 11 which were obtained by the following procedures: into a cell in a suppository release testing apparatus (Model TMS-103 of Toyama Sangyo K.K.), 3 ml of Fluid 2 (pH ≃ 6.8) and one suppository were introduced and agitated at 25 rpm; in the release phase, 300 ml of Fluid 2 (pH ≃ 6. 8) was introduced and stirred at 100 rpm; both the cells and the release phase were held at 37 ± 0.1°C while the amount of aminopyrine that dissolved in the release phase was measured at predetermined intervals. Tablet Preparation Fumaric acid and DL-tryptophan were well mixed in the proportions shown above. Each of the resulting mixed powders was fed into a single-punch machine equipped with a die (7.0 mm ⊘ ) and flat-faced punches, and compressed at a total pressure of 1 ton so as to make tablets each weighing 100 mg. Measurement of Dissolving Time Measurement was conducted in accordance with the "Method of Disintegration Test", the Japanese Pharmacopoeia, 10th rev., and the time required for the tablets in the tester to disappear was defined as the dissolution time. No auxiliary disk was used in the measurements. Three testing fluids were used: Fluid 1 (pH ≃ 1.2), Fluid 2 (pH ≃ 6.8), and distilled water. Results In Fluid 1 (pH ≃ 1.2), the dissolution rate slowed down as the content of fumaric acid increased. In Fluid 2 (pH ≃ 6.8), the dissolution rate decreased sharply as the content of DL-tryptophan increased. This shows that by properly controlling the mixing proportions of fumaric acid and DL-tryptophan, the drug dissolution rate can be adjusted to any desirable value that fits the pH of a given environment. Another observation was that at a certain ratio of fumaric acid to DL-tryptophan, the dissolution time was constant irrespective of the pH of the testing fluids. This indicates the possibility of attaining a constant dissolution time notwithstanding the change in the pH of a given environment. The results of the disintegration test conducted as above of the individual tablets (sample Nos. 1 - 7) are graphed in Fig. 12.

Claims: A slow-release pharmaceutical composition which comprises DL-tryptophan or a mixture of fumaric acid and DL-tryptophan in addition to one or more pharmacologically active substances. The composition according to Claim 1 wherein DL-tryptophan or a mixture of fumaric acid and DL-tryptophan are present in an amount of at least 10 wt% of the total weight of the composition. The composition according to Claim 1 which is a layered tablet consisting of a layer containing a pharmacologically active substance and a layer which does not contain any pharmaceutically active substance. A slow-release multiple-layered tablet which is prepared by compressing a layer having the composition recited in Claim 1 and a fast-release layer containing the same pharmacologically active substance as present in the first layer. A slow-release multiple-layered tablet which is prepared by compressing a layer having the composition recited in Claim 1, a layer composed of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan, and a fast-release layer containing the same pharmacologically active substance as present in the first layer. A slow-release granule composed of a granulation having the composition recited in Claim 1. A slow-release granule composed of a granulation having the composition recited in Claim 1 and which is coated with an enteric base or with a water-insoluble base. A slow-release granule according to Claim 6 or 7 further comprising a fast-release granulation containing the same pharmacologically active substance as present in the first granulation. A slow-release granule wherein a fast-release granulation of the pharmacologically active substance is coated with DL-tryptophan or a mixture of fumaric acid and DL-tryptophan. A slow-release capsule which is filled with granules having the composition recited in any one of Claims 6 to 9. A slow-release tablet prepared by compressing a powder having the composition recited in Claim 1 or by compressing a granulation having the composition recited in any of Claims 6 to 9, or by compressing a mixture of a granulation having the composition recited in Claim 1 and a water-insoluble base. A slow-release tablet wherein a tablet prepared by compressing a granulation having the composition recited in Claim 6 or a powder paving the composition recited in Claim 1 is coated with an enteric base or with a water-insoluble base. A sugar-coated slow-release tablet wherein a tablet having the composition recited in any one of Claims 11 or 12 is surrounded by a sugar coating optionally containing the same pharmacologically active substance as present in said center tablet. A core/shell slow-release tablet wherein the core is a tablet having the composition recited in any one of Claims 11 or 12, with a shell being compressed around said core tablet, said shell being made of a fast-release composition containing the same pharmacologically active substance as present in said core tablet. A core/shell slow-release tablet wherein the core is a tablet having the composition recited in any one of Claims 11 or 12, with two shells being compressed around said core tablet, the first shell around said core tablet being made of DL-tryptophan or a mixture of fumaric acid and DL-tryptophan, and the second shell around said first shell being made of a fast-release composition containing the same pharmacologically active substance as present in said core tablet. A slow-release suppository wherein a granulation having the composition recited in any one of Claims 6 to 9 is incorporated in a suppository base, or a tablet having the composition recited in Claim 11 is coated with a suppository base. The use of fumaric acid and/or DL-tryptophan for preparing a slow-release pharmaceutical composition.

Inventors: IIDA, YOSHIMITSU, SUMIDA, SHUJI
Applicants: CHUGAI SEIYAKU KABUSHIKI KAISHA
Application year: 1986
Main classification: A61K9
IPC codes: A61K9, A61K47, A61K31