A SUSTAINED-RELEASE SOLID MEDICAMENT FORM AND A METHOD FOR THE PREPARATION THEREFOF

Abstract: Different from conventional sustained-release granular solid medicament form of which each granule has a structure formed of a core granule containing a pharmaceutically effective ingredient and a coating layer thereon for controlling the releasing rate of the effective ingredient, each granule of the inventive medicament form has a structure formed of a core granule mainly composed of an excipient and a coating layer thereon of a cellulose ether insoluble in hot water and the pharmaceutically effective ingredient is contained in the coating layer of the cellulose ether. The granules are prepared by coating core granules of an excipient with a coating liquid which is a hot aqueous dispersion of a powdery cellulose ether insoluble in hot water and contains the pharmaceutically effective ingredient dissolved or dispersed therein. If necessary, the granules are provided with an overcoating layer of a wax-like material to further improve the controllability of the releasing rate of the effective ingredient.

Description: _ !____ A SUSTAINED-RELEASE SOLID MEDICAMENT FORM AND A METHOD FOR THE PREPARATION THEREOF Field of Technology The present invention relates to a sustained-release granular solid medicament form of which the concentration of the effective pharmaceutical ingredient in blood can be maintained at an effec¬ tive level to exhibit the desired medical effect over a long time by a single administration as well as to a method for the preparation of such a solid medicament form. Background Technology Solid medicament forms for sustained release in the prior art include granules, capsules illed with granules, tablets and the like, of which the largest number of the hitherto commercialized medicament products are in the granular form by virtue of the ad¬ vantage of granules that a patient can be administrated with any desired dose of the medicament without dividing as is sometimes necessary in the administration of tablets. As a method for the pre¬ paration of a typical sustained-release granular solid medicament form, the surface of granules shaped from a mixture composed of an effective ingredient, excipient and binder is coated with a solu¬ tion of a wax-like coating material in an organic solvent followed by drying. The factors which provide proper selection of the posi¬ tion in the digestive tract where the effective ingredient is re- leased and control of the sustainability of the concentration of the ingredient in blood for a desired length of time include the propor¬ tion of the components in the mixture forming the granules, solu¬ bility behavior of the binder in the digestive fluids, coating amount of the wax-like coating material and so on. Besides, an¬ other type of a sustained-release granular medicament form is known which is mainly composed of an effective ingredient and a wax or polymeric substance insoluble in water but soluble in orga¬ nic solvents. It is of course indispensable in the process of granula¬ tion thereof to use an organic solvent for dissolving the wax or polymeric substance. The sustained-release solid medicament forms in the prior art have various problems in respect of the performance as a medi¬ cine and method for the preparation thereof. For example, the use of an organic solvent involves problems including danger of fire and explosion, toxicity against the workers in the production of the medicament, eventual residual amount of the solvent in the finish¬ ed medicament form and so on. The residual amount of the solvent in the finished medicament form can be decreased only by a sub¬ stantial extension of the drying time in the coating process leading to a disadvantageous decrease in the productivity due to the in¬ crease of the overall time taken for the production if not to mention the disadvantage of possible decomposition of the effective ingredi¬ ent by prolonged heating. Alternatively, a method of water-based film coating has been developed in which the coating solution is prepared from a water- soluble polymeric material without using any organic solvent and the method is widely utilized in the coating of ordinary solid medi¬ cament forms of tablets and granules. No practical procedure has yet been proposed, however, of the water-based film coating meth¬ od in the preparation of sustained-release solid medicament forms. The reason therefor is that the method of the film coating has been developed mainly with objects of prevention of decrease in the acti¬ vity of the effective ingredient, decrease of bitterness and increase of the beautiful appearance while the object of a sustained-release solid medicament form to ensure a sufficiently high concentration of the effective ingredient in blood over a length of time has been achieved solely by means of a wax-like material insoluble or hard¬ ly soluble in water. On the other hand, Japanese Patent Kokai No. 58-110513 teaches a composition for sustained-release solid medicament forms of which the carrier base is a hydroxypropyl methyl cellulose or a mixture thereof with 30% by weight or less of an ethyl cellu¬ lose and/or sodium salt of carboxymethyl cellulose. The medica¬ ment form disclosed there is prepared by compression molding so that the object thereof is basically a solid medicament form in the form of tablets. Although such a solid medicament form is suitable for the purpose of sustainedly releasing the effective ingredient, a disadvantage thereof is that, when the tablets are divided into fragments with an object to adjust the dose to a patient, the per¬ formance of the medicament relative to the sustained releasability of the ingredient is totally altered depending on the divided condi¬ tion of the tablets. In addition, the composition disclosed there is not suitable as a material of granules because sufficiently dense granules can hardly be prepared therefrom so that the effective ingredient is released prematurely not to meet the object of a sus¬ tained-release solid medicament form. In connection with the method of water-based film coating of granules and tablets to impart sustained releasability thereto by use of a cellulose ether as the base material of the coating film, no satisfactory sustained releasability has ever been obtained due to the proble.ms in the properties of the base material and the condi¬ tions of the working procedure suitable for film coating. When car¬ rier granules are coated in a conventional manner, " in particular, adherence of the granules proceeds in the course of coating to cause so-called agglomeration unless the concentration of the cel¬ lulose ether in the coating solution is extremely low so that film coating of granules with a cellulose ether cannot be practiced in¬ dustrially by solving the above mentioned problem. In this regard, the inventors have previously proposed a method of film coating by using a hot-water dispersion of a high-molecular cellulose ether which, in the prior art, can hardly be used for film coating. Disclosure of the Invention In the course of the investigations leading to the above men¬ tioned method of film coating by using a hot water dispersion of a high-molecular cellulose ether, it has been unexpectedly discover¬ ed that a quite satisfactory sustained-release granular solid medi¬ cament form can be obtained when carrier granules are coated with the above mentioned coating dispersion which also contains the effective pharmaceutical ingredient dissolved or dispersed therein so as to provide the carrier granules with a dense coating layer composed of the hot water-insoluble cellulose ether and the effective ingredient from which the effective ingredient is released at an efficiently controlled rate. Namely, the present invention provides a sustained-release granular solid medicament form of which each granule is compos¬ ed of a core shaped of a carrier mainly composed of an excipient and a coating layer formed of a cellulose ether insoluble in hot wa¬ ter and containing a pharmaceutically effective ingredient on the surface of the core granule. The above defined sustained-release granular solid medica¬ ment form can be prepared by coating core granules shaped mainly of an excipient with a coating liquid which is an aqueous disper¬ sion of a cellulose ether insoluble in hot water containing a phar¬ maceutically effective ingredient dissolved or dispersed therein. Best Mode Embodiments to Practice the Invention The mechanism by which the above described granular solid medicament form exhibits sustained releasability of the effective ingredients is not quite clear. It is presumable that, when the coat¬ ing layer formed mainly of a cellulose ether and containing the ef¬ fective ingredients is brought into contact with the digestive fluid, the cellulose ether absorbs the fluid and is converted into a layer of a hydrogel which is gradually dissolved in the digestive fluid to release the effective ingredient or through which the effective in¬ gredient is gradually leached out into the digestive fluid. Accord¬ ingly, the sustained releasability of the effective ingredient from the granules can be controlled by appropriately selecting the hot water-insoluble cellulose ether forming the layer of hydrogel de¬ pending on the nature of the effective ingredient and, optionally, by providing an overcoating layer with a wax-like coating materi¬ al according to need. The core granules made mainly of an excipi- ent serves to control the final disintegration time of the medica¬ ment form in the digestive tract. Several kinds of cellulose ethers are suitable as the hot wa¬ ter-insoluble cellulose ether used in the invention including hy- droxypropyl methyl cellulose, methyl cellulose, hydroxypropyl cel¬ lulose, hydroxyethyl methyl cellulose and the like. One of the im¬ portant characteristics of these cellulose ethers is that they are in¬ soluble in hot water but soluble in cold water so that, when an aqueous dispersion of the powdery cellulose ether at a sufficiently high temperature is gradually cooled, dissolution of the cellulose ether particles takes place at a certain temperature and the disper¬ sion is converted into an aqueous solution showing a rapid in¬ crease of the viscosity. The above mentioned critical temperature below which the cellulose ether is dissolved in water is called the solubilization temperature which is a value inherent in each type- of the cellulose ether products. For example, methyl cellulose and hydroxypropyl cellulose have a solubilization temperature of 35 to 45 °C while different grades of hydroxypropyl methyl cellulose have different solubilization temperatures of 45 to 55 °C for type 2910, 50 to 60 °C for type 2906 and 60 to 70 °C for type 2208 of the hydroxypropyl methyl cellulose according to the classification in Japanese Pharmacopoeia. The aqueous dispersion of a hot water-insoluble cellulose ether is prepared by adding the powdery cellulose ether to hot water at a temperature higher than the above mentioned solubili¬ zation temperature of the respective cellulose ether under agita¬ tion and the aqueous dispersion of a cellulose ether once prepared should be kept at a temperature not lower than the solubilization temperature of the cellulose ether throughout until the dispersion is used as a coating liquid of the core granules. On the contrary, cellulose ether powders should never be added to cold water to be dispersed therein because the particles of the cellulose ether dis¬ persed in cold water become at least partly dissolved in water in the course of temperature increase of the dispersion so that the dispersion acquires a gel-like consistency and can no longer be used as a coating liquid of the core granules. The aqueous disper¬ sion of a cellulose ether used as the coating liquid should contain from 5 to 30% by weight of the powdery cellulose ether. When the content thereof is too high in the aqueous dispersion, the disper¬ sion may have a slurry-like consistency eventually to cause clog¬ ging of the spray gun nozzles used in the coating work. When the content is too low, on the other hand, coating layers of a desired thickness can be formed only by continuing the coating work for an unduly long time to cause some economical disadvantages. The hot water-insoluble cellulose ether used in the inventive method should preferably have such a particle size distribution that an at least 90 % by weight portion thereof passes thorough a #100 screen having a mesh opening of 149 μ as specified in the Japanese Pharmacopoeia. When the powder contains coarser par¬ ticles in an excessively large amount, no satisfactory coating films can be formed on the core granules due to incomplete coalescence of the particles in the coating layer. The pharmaceutically effective ingredient dissolved or dis¬ persed in the aqueous dispersion of the cellulose ether is not parti¬ cularly limitative and any medicinal compound can be used when it should desirably be released sustainedly in the digestive tract for medical purposes. Examples of medicinal compound usable in the invention include theophylline, aspirin, nifedipine, chlorphen- iramine maleate, propantheline bromide, trihexyphenydyl hydro- chloride, diclofenac sodium, indomethacin, nitroglycerin, potassi¬ um chloride, iron (II) sulfate, iron (II) fumarate and the like. The amount of the phrmaceutically effective ingredient dissolved or dispersed in the coating liquid should of course be adequately selected depending on the desired rate of sustained release of the medicine, total dose and other factors but it is usually in the range from 0.1 to 50% by weight based on the amount of the cellulose ether dispersed therein. When the pharmaceutically effective in¬ gredient is insoluble in neutral water, it is of course dispersed in water to give a coating liquid, if necessary, after pulverization in order to increase the absorptivity of the medicine in the digestive organ. The pharmaceutically effective ingredient can be added to the coating liquid in any convenient procedure without particular limitation. For example, it can be added as such to a hot aqueous dispersion of the cellulose ether prepared beforehand or, alterna¬ tively, it is dissolved or dispersed in hot water and the hot solution or dispersion is then admixed with the aqueous dispersion of the cellulose ether. The coating liquid, which is an aqueous dispersion of a cellu¬ lose ether containing a pharmaceutically effective ingredient ei¬ ther dissolved or dispersed therein, may optionally contain various kinds of additives according to need including water-soluble poly¬ mers and surface active agents to improve the dispersibility of the cellulose ether particles and a water-insoluble effective ingredient, coloring agents such as edible dyes and edible lake pigments, ex¬ tender pigments such as talc and a finely divided silica powder, plasticizers such as polyethylene glycol and triethyl citrate, fla¬ vors such as vanilla extract and menthol, and others. The sustain¬ ed releasability of the pharmaceutically effective ingredient can be controlled by admixing the coating liquid with saccharides, e. g., lactose, and waxes, e.g., beeswax and carnauba wax. The core granules as the carrier of the above described coat¬ ing layer are shaped from an excipient such as lactose, starch, mi- crocrystalline cellulose and the like or a mixture mainly composed of such an excipient with optional addition of a part of the pharma¬ ceutically effective ingredient, coloring agents, taste and flavor improvers and the like. These materials are kneaded together with addition of a small volume of water and granulated by extrusion into a columnar form by use of an extrusion granulator followed by drying in a fluidized drier although the method of granulation is not particularly limitative. The core granules preferably have such a particle size distribution that at least 85% by weight of the particles can pass through a #42 screen having a mesh opening of about 355 μm specified in Japanese Pharmacopoeia. When the par¬ ticle size distribution of the core granules is coarser than above, some inconveninences are caused in handling of the medicament form and the medicament form is less acceptable to the patient administrated therewith. When the granulesd are too fine, on the other hand, the resultant solid medicament form may be unsatisfactory in respect of the sustained re-leasability of the pha- maceutically effective ingredient. The core granules are then coated with the coating liquid which is a hot aqueous dispersion of the cellulose ether containing the pharmaceutically effective ingredient dissolved or dispersed therein. The coating procedure may be conventional by use of any known coating machine in the prior art such as fluidized coating machines, pan coaters having a mechanism of aeration for drying and the like used in the process of film coating of granules in the prior art. The coating liquid must be kept at a sufficiently high temperature to prevent premature dissolution of the cellulose ether so that the coating apparatus should preferably be provided with an appropriate means for heating or heat insulation of the coating liquid. The coating amount of the coating layer containing the effective ingredient is preferably in the range from 5 to 20% by weight based on the core granules. The granular medicament obtained in the above described manner is quite satisfactory in most cases in its performance as a sustained-release solid medicament form. It is, however, optional that the granular medicament form is further provided with a thin overcoating layer of a wax-like material when an increased pos¬ sibility of controlling the sustained releasability is desired. Thus, the granules after the above described coating process are admixed with a small amount of a wax-like material and subjected to a heat treatment at a temperature higher than the melting point of the wax-like material. In this regard, the wax-like material used as the material for overcoating is preferably selected from those hav¬ ing a melting point in the range from 40 to 90 °C or, preferably, from- 55 to 70 °C including waxes, e.g., paraffins, beeswax and car- nauba wax, higher alcohols, higher fatty acids, glycerin fatty acid - esters, polyethylene glycols and the like. When the melting point of the wax-like material is too low, the overcoated granules may eventually adhere to each other when they are stored under ordi¬ nary conditions. When the melting point of the wax-like coating material is too high, on the other hand, the process of coating must be performed by heating the blend of the granules and the wax¬ like material at an unduly high temperature to cause a disadvan¬ tage of eventual denaturation of the pharmaceutically effective ingredient contained in the coating layer of the cellulose ether de¬ pending on the thermal stability of the ingredient. The heat treat¬ ment is performed by fluidizing the blend of the granules and the wax-like coating material with hot air in a fluidized coating ma¬ chine or by blowing hot air at the blend under rotation in a coating pan of a pan coater. Although the wax-like coating material may be introduced into the coating machine in any desired form such as fine powder, granules, blocks and the like, a granular form is pre¬ ferred in respect of the convenience in handling. The temperature of the hot air for the fluidization of or blown at the blend is usually at or in the vicinity of the melting point of the wax-like coating material though not limited thereto. By this wax treatment, a thinovercoating layer of the wax-like coating material is formed on the surface of the granules to exhibit a retarding effect on the releas-ing rate of the phamaceutically effective ingredient con¬ tained in the underlying layer. Accordingly, the retarding effect on the releasing rate of the pharmaceutically effective ingredient from the inventive granular medicament form is increased by the increase in the amount of overcoating with the wax-like coating material. Usually, the amount of overcoating with the wax-like coating ma-terial is preferably in the range from about 0.2% to about 30% by weight based on the granular solid medicament form of the invention. Besides, it is also optional that, regardless of the above described overcoating with a wax-like coating material, the inventive granular sustained-release solid medicament form is provided with another type of an overcoating layer such as gastro- soluble and enterosoluble coating films depending on the particu¬ lar requirement for the medicament. In the following, the sustained-release granular solid medi¬ cament form of the invention and the method for the preparation thereof are described in more detail by way of examples, in which the terms of "%" and "parts" all refer to "% by weight " and "parts by weight", respectively. Example 1. A coating liquid was prepared by adding and dispersing 15 parts of a hydroxypropyl methyl cellulose in 82 parts of hot water at 80 °C with agitation and then 3 parts of indomethacin with fur¬ ther continued agitation. The hydroxypropyl methyl cellulose was a commercial product (60SH4000, manufactured by Shin-Etsu Chemical Co.), of which a 2 % aqueous solution had a viscosity of 4250 centipoise at 20 °C, having such a particle size distribution that 99% of the particles could pass a #100 screen and a solubi¬ lization temperature of 48 °C according to the Japanese Pharma¬ copoeia. Separately, a mixture of 97 parts of lactose and 3 parts of a hydroxypropyl cellulose (HPC-EFP, manufactured by Shin-Etsu Chemical Co.) was kneaded with addition of a small volume of water and granulated into columnar granules passing through a screen of 0.8 mm diameter mesh openings by use of an extrusion granulator followed by drying for 2 hours in a fluidized drying machine with the fluidizing air at 80 °C and sorting of the lengths by passing the granules through a granule sorter. The granules prepared above were subjected to coating with the coating liquid. Thus, 3 kg of the granules were charged into a fluidized coater (Model Glatt WSG-5, manufactured by Ohgawara Seisakusho Co.) and coated with the coating liquid for 200 minutes under the conditions including: the temperature of the fluidizing air of 80 °C; temperature of the exhaust of 47 to 50 °C; and feed rate of the coating liquid of 50 g/minute followed by drying for 30 min¬ utes with the fluidizing air at 80 °C. In this manner, a sustained- release granular solid medicament form was obtained which con¬ tained 61 mg of indomethacin per g. For comparison, rapid-release granules of indomethacin for control test were prepared in the following manner. Thus, gra¬ nules were prepared from a blend composed of 61 parts of indo¬ methacin, 630 parts of lactose, 279 parts of corn starch and 30 parts of the same hydroxypropyl cellulose as used above in about the same procedure as in the above described granulation proce¬ dure of the core granules of lactose and the hydroxypropyl cellu¬ lose. The granules also contained 61 mg of indomethacin per g. Gelatin-made capsules were filled each with 410 mg of the above prepared inventive granules or comparative granules and subjected to a releasing test of the indomethacin according to the procedure for the releasing test in indomethacin capsules specified in Japanese Pharmacopoeia to determine the % release of the in¬ gredient as a function of time. The results are shown in Table 1 below, from which it is clear that the granules of the invention are quite satisfactory as a sustained-release solid medicament form. Table 1 Example 2. A coating liquid was prepared by first dispersing 10 parts of a hydroxypropyl methyl cellulose in 89 parts of hot water at 80 °C with agitation and then adding and dissolving 1 part of chlorphen- iramine maleate with further continued agitation. The hydroxy¬ propyl methyl cellulose was a commercial product (90SH8000, ma¬ nufactured by Shin-Etsu Chemical Co.), of which a 2% aqueous so¬ lution had a viscosity of 8860 centipoise at 20 °C, having such a particle size distribution that 98% of the particles could pass a #100 screen specified in Japanese Pharmacopoeia and a solubili¬ zation temperature of 64 °C. This coating liquid was used for coating of the same core gra¬ nules as prepared in Example 1. Thus, 3 kg of the core granules were introduced into the same fluidized coater as used in Example 1 and coated with the coating liquid for 200 minutes under the con¬ ditions including: the temperature of the fluidizing air of 80 °C; temperature of the exhaust of 46 to 48 °C; and feed rate of the coat¬ ing liquid of 50 g/minutes followed by drying for 30 minutes with the fluidizing air at 80 °C and then wax treatment with fluidiza- tion under the same conditions after introducing 400 g of a bleach¬ ed beeswax of Japanese Pharmacopoeia having a melting point of 60 to 67 °C as a wax-like coating material in several po-tions. The thus obtained sustained-release granular solid medicament form contained 22 mg of chlorpheniramine maleate per g. .For comparison, rapid-release granules of chlorpheniramine maleate for control test were prepared from a blend of 22 parts of chlorpheniraime maleate, 848 parts of lactose, 100 parts of a low- substitution hydroxypropyl cellulose (LH-21, manufactured by Shin-Etsu Chemical Co.) and 30 parts of the same hydroxypropyl cellulose as used in Example 1 in about the same procedure as in the granulation of the core granules in Example 1. The compara¬ tive granules contained 21 mg of chlorpheniramine maleate per g. Gelatin-made capsules were filled each with 364 mg of the above prepared inventive or 381 mg of the comparative granules and subjected to a releasing test of the chlorpheniramine maleate by the first method of releasing test specified in Japanese Pharma¬ copoeia using the first fluid as the test solution. The amount of the released ingredient was determined by the spectrophotometric measurement of the test solution at a wavelength of 262 nm to give the results of the released amount of the chlorpheniramine male¬ ate in % shown in Table 2 below, from which it is clear that the granules of the invention are quite satisfactory as a sustained- re¬ lease solid medicament form. Table 2 Possibility of Industrial Utilization To summarize the advantages obtained by the present inven¬ tion, the problems in the prior art sustained-release solid medica¬ ment forms accompanying the use of organic solvents can be com¬ pletely solved by the invention. In addition, the invention provides following advantages. (1) The granular sustained-release solid medicament form can be imparted with well controlled releasability of the pharmaceutical¬ ly effective ingredient exactly to meet the medical requirements. (2) The coating procedure can be performed almost without the problem of agglomeration of the granules and granules of any de¬ sired coating amount can be easily prepared within a short work¬ ing time. (3) The activity of the pharmaceutically effective ingredient can be maintained sustainedly with good controllability because a cel¬ lulose ether of any desired molecular weight can be used without particular problems in the coating works.

Claims: C L A I M S 1. A sustained-release granular solid medicament form of which each granule is composed of a core granule shaped of a carri¬ er mainly composed of an excipient and a coating layer on the sur¬ face of the core granule formed of a cellulose ether insoluble in hot water and containing a pharmaceutically effective ingredient. 2. The sustained-release solid medicament form as claimed in claim 1 wherein each granule is further coated with an overcoat¬ ing layer of a wax-like material. 3. The sustained-release granular solid medicament form as claimed in claim 1 wherein the cellulose ether insoluble in hot wa¬ ter is selected from the group consisting of methyl cellulose, hy¬ droxypropyl cellulose, hydroxypropyl methyl cellulose and hy- droxyethyl methyl cellulose. 4. The sustained-release granular solid medicament form as claimed in claim 1 wherein the excipient is selected from the group consisting of lactose, starch and microcrystalline cellulose. 5. The sustained-release granular solid medicament form as claimed in claim 2 wherein the wax-like material is selected from the group consisting of paraffins, waxes, higher alcohols, higher fatty acids and esters thereof, fatty acid esters of glycerin and polyethylene glycols having a melting point in the range from 40 °C to 90 °C. 6. A method for the preparation of a sustained-release granular solid medicament form of which each granule is composed of a core granule shaped of a carrier mainly composed of an excipient and a coating layer on the surface of the core granule formed of a cellu¬ lose ether insoluble in hot water and containing a pharmaceutical¬ ly effective ingredient which comprises the steps of: (A) granulating a carrier mainly composed of an excipient to give core granules; (B) preparing a coating liquid by dispersing a powder of a cellu¬ lose ether insoluble in hot water and dispersing or dissolving a pharmaceutically effective ingredient in hot water at a tempera¬ ture higher than the solubilization temperature of the cellulose ether; (C) coating the core granules with the coating liquid to give coa¬ ted granules; and (D) drying the thus coated granules. 7. The method for the preparation of the sustained-release gra¬ nular solid medicament form as claimed in claim 6 wherein the coating liquid contains from 5 to 30% by weight of the cellulose ether dispersed therein. 8. The method for the preparation of the sustained-release gra¬ nular solid medicament form as claimed in claim 6 wherein the powder of the cellulose ether has such a particle size distribution that at least 90 % by weight of the particles pass through a screen having mesh openings of 149 μm. 9. The method for the preparation of the sustained-release gra¬ nular solid medicament form as claimed in claim 6 wherein the coating liquid contains from 0.1% to 50% by weight of the pharma¬ ceutically effective ingredient based on the amount of the cellulose ether.

Inventors: KOKUBO HIROYASU, ONDA YOSHIRO, SEKIGAWA FUJIO, KOKUBO, HIROYASU, ONDA, YOSHIRO, SEKIGAWA, FUJIO
Applicants: SHINETSU CHEMICAL CO, SHIN-ETSU CHEMICAL CO., LTD.
Application year: 1988
Main classification: A61K9
IPC codes: A61K9