Pharmaceutical composition for treating periodontal diseases.

0001This invention relates to a pharmaceutical composition which is applied to a periodontal pocket or paradentium for the purpose of treating periodontal diseases. The pharmaceutical composition may be provided in the form of gel, sheet, film or bar-like formulation to release a controlled and effective amount of an active ingredient at the periodontal pocket or paradentium.

0002The "periodontal diseases" is a general term of various inflammatory diseases of paradentium. The diseases include a series of diseases exhibiting various syndromes which vary from each other according to the stage or situation of the diseases or the age of the patient, and have not been definitely subclassified. Since, however, the term "periodontal diseases" is given to any inflammatory disease which initially occurs at a marginal gingiva area and finally reaches an alveolar bone, the diseases can be roughly divided, on the basis of the degree of the inflamma­tion, into "gingivitis" in which the inflammation is limited to the gingiva tissue, and "paradentitis" in which the inflammation is chronic and found even in an alveolar bone. However, peculiar diseases such as "juvenilie paradentitis" and "acute necrotizing ulcerative gingivitis" are also included in the periodontal diseases.

0003The paradentitis, which was once called "alveolar pyorrhea", is characterized by remarkable symptoms such as inflammation of gingiva, formation periodontal pockets, bleeding and pus discharge from said periodontal pockets, and it brings about resorption of alveolar bone, loose tooth, and shedding of tooth.

0004The consensus of most investigators is that the periodontal diseases is caused by bacteria present in dental plaques formed in periodontal pockets. Efforts have been concentrated on the discovery of pathogenic bacteria responsible for said diseases. At the present time, an attributable major pathogen is recognized to be a certain nigral pigment-producing bacteria, such as genus <u style="single">Bacteroides</u>. However, other genus of bacteria including <u style="single">Actinobacillus</u>, <u style="single">Capnocytophaga</u>, <u style="single">Fusobacterium</u> and <u style="single">Spiro­chetes</u> may be included in the causative pathogens. In any case, it is an established theory that the periodontal diseases should not be attributed to all bacteria present in the dental plaque.

0005The periodontal diseases has previously been treated by several ways, such as exhaustive scaling of plaques in periodontal pockets, root plainning, gingivectomy to eliminate the periodontal pocket, or surgical curettage to excise inflammatory tissues. These treatments have been effective to some extent but not satisfactory.

0006On the other hand, pharmacotherapy has also been conducted using a drug selected from germicides, anti-­inflammatory agents, plaque solubilizing agents, hemo­styptics, and the like. These drugs are used in the form of the formulation suited for internal use or massotherapy (e.g., dentifrices, ointments, and the like). However, they are not satisfactory for the purpose of treatment of perio­dontal diseases because the internal use hardly permits the selective migration of the drug to the lesional region, and the massotherapy is not successful in solubilizing the plaques which are present beneath the gingival margin.

0007Recently, strips which comprise polymers and active ingredients for treatment of periodontal diseases have been developed. These strips are said useful for the treatment of plaques and inflammation beneath the gingival margin. The strips can be applied directly to the lesional region to be treated, and therefore, the active ingredient can be concentrated to the desired site selectively. This modified therapeutic method has been proved to be more effective than any conventional pharmacotherapy. For instance, J. M. Goodson et al. disclose the implantation of "hollow fiber", which contains germicides, into gingival resion (J. Clinical Periodontology, 1979: 6: 83-92). M. Addy et al. have reported the insertion of strips, which were prepared from a mixture of an insoluble polymer such as polyethylmethacrylate and germicides, into periodontal pockets (J. Periodontal, 693, Nov. 1982). In addition, insertion of the strips, prepared from a mixture of a soluble polymer and a drug, into the lesional region, such as periodontal pockets, is also reported (Japan Patent Publication No. 59-222406).

0008The formulations mentioned above comprise a mixture of an active ingredient and a homogeneous polymer base. Accordingly, where such formulation is designed to contain two or more active ingredients which differ each other in terms of pharmacological activity and therapeuti­cally effective dose, it has been impossible to prepare the formulation in which each of the plural ingredients may release independently and provide its suitable concentration as desired.

0009The use of the hollow fiber or insoluble polymer, as a base, causes irritation or pain to patients, and moreover, it necessitates the removal of the base after release of an active ingredient, which is often annoying. On the other hand, the strip which comprises a soluble polymer as a base or carrier permits a rapid release of an active ingredient. Accordingly, it does not afford a constant therapeutical effect and, therefore, has a poor practical use.

0010As the result of an extensive study for seeking a novel therapeutical composition for periodontal diseases, which suitably controls the release of one or more of active ingredients and which does not give any uncomfortable feelings to patients, it has been found that the use of a two-phase carrier base, which consists of particles compri­sing a polymer having a limited solubility in water and a water soluble polymer used for dispersing such particles, meets the requirements just mentioned above.

0011Thus, the present invention provides a pharmaceu­tical composition for treating periodontal diseases, which comprises one or more of therapeutically active ingredients dispersed in a carrier, characterized in that said carrier consists of <ul id="ul0001" list-style="none"><li>(A) water soluble polymer, and</li><li>(B) polymeric particles having a limited solubility,</li></ul>     said particles being dispersed in said water soluble polymer.

Brief Description of the Drawing

0012Fig. 1 shows the dissolution profile of two active ingredients contained in the pharmaceutical composition of the invention which is in the form of a film. Fig. 2 shows the dissolution profile of two active ingredients contained in a conventional composition.

0013The term "a polymer having a limited solubility in water" herein used includes an insoluble polymer, a spar­ingly soluble polymer, and a polymer which dissolves in an aqueous medium within a limited pH range.

0014For the purpose of the present invention, the term "insoluble polymer" means a polymer which dissolves in an aqueous medium, particularly in water, in a concentration of less than 0.1% by weight, irrespective of pH.

0015"Water soluble polymer" or "soluble polymer" denotes any polymer which dissolves in an aqueous medium, particularly in water, in a concentration of more than 1% by weight, irrespective of pH. "Sparlingly soluble polymer" means a polymer which has a solubility between the soluble polymer and the insoluble polymer or decomposes to dissolve in vivo slowly. The term "polymer which dissolves in an aqueous medium within a limited pH range" means a polymer which dissolves in an aqueous medium, particularly in water, having a pH higher than 4 or lower than 6, in a concentra­tion of more than 1% by weight.

0016For the purpose of simplicity, the insoluble polymer, sparlingly soluble polymer and the polymer which dissolves in an aqueous medium within a limited pH range are hereinafter referred to as "non-soluble polymer" as a whole.

0017The soluble polymer used in the present invention must be fabricated into a semi-solid or a solid material. The non-soluble polymer should have a property suitable for being fabricated into particles. Both soluble and non-­soluble polymers employed in the present application should be, of course, physiologically acceptable.

0018Specific examples of the insoluble polymer are ethyl cellulose, cellulose acetate, ethyl methacrylate / trimethylammonioethyl methacrylate chloride copolymer, and the like. The sparlingly soluble polymer includes, for instance, biodegradable polymer such as polyglycolic aicd, polylactic acid, polytetramethylglycolide, polydiethyl­glycolide, poly- -caprolactone, poly(DL-decalactone), poly(alkyleneadipate), copolymers thereof, and ion exchange resins.

0019The polymer which dissolves in an aqueous medium having a pH above 4 includes copolymers consisting of acry­lic acid, methacrylic acid and/or esters thereof, such as methyl acrylate / methacrylic acid copolymer, methyl acry­late / methacrylic acid / octyl acrylate copolymer, ethyl acrylate / methacrylic acid copolymer, methyl acrylate / methacrylic acid / methyl methacrylate copolymer, and methyl methacrylate / methacrylic acid copolymer, hemiesters of organic bivalent acid with polysaccharide acetates such as cellulose acetate phthalate, cellulose acetate succinate, cellulose acetate maleate, starch acetate phthalate, and amylose acetate phthalate, hemiesters of organic bivalent acid with alkylated polysaccharides such as methyl cellulose phthalate, hemiesters of organic bivalent acid with hydroxy­propylmethyl cellulose phthalate, and hydroxyethyl ethyl cellulose phthalate, hydroxypropylmethyl cellulose acetate succinate, alkyl ethers of carboxyalkylated polysaccharide such as carboxymethylethyl cellulose, hemiesters of organic bivalent acid with polyvinyl alcohol and its derivatives such as polyvinyl alcohol phthalate, polyvinyl acetate phthalate, polyvinyl acetal phthalate, and polyvinyl butyl­ate phthalate.

0020The polymer which dissolves in an aqueous medium having a pH below 6 includes dimethylaminoethyl methacrylate / methyl methacrylate copolymer, polyvinylacetal / dimethyl­amino acetate, cellulose acetate dibutylhydroxypropyl ether, and the like.

0021Specific examples of the soluble polymer are, for instance, methyl cellulose, hydroxypropyl cellulose, sodium carboxymethylcellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, sodium alginate, propylene glycol alginate, pulluran, tragacanth, xanthan gum, chitosan, polyethylene oxide, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, and a salt thereof.

0022The pharmaceutical composition of the present invention may be prepared by dispersing one or more of active ingredients into a non-soluble polymer, or both of a soluble polymer and a non-soluble polymer, and mixing these polymers, and finally forming the resultant mixture into a solid material of a film, sheet or bar-like shape, or into a semi-solid material such as gel or ointment.

0023In more detail, one or more of non-soluble polymers is dissolved, as the first step, in an appropriate organic solvent. To the resultant solution is dissolved or dispersed one or more of active ingredients, and the mixture is formed into film or sheet by casting method. The resul­tant solid material is ground into particles.

0024The particles are also obtainable by spray drying, Wuster coating, Coacervation, or Drying in liquid phase. The average particle size may range from 1µ to 500µ depend­ing on the contemplated release pattern of the active ingredient. However, the size between 1µ and 300µ is generally preferred.

0025On the other hand, one or more of water soluble polymers are dissolved in a suitable solvent. The solvent may contain, if desired, one or more of active ingredients. Subsequently, the pH of the mixture is adjusted, if nece­ssary, and the particles obtained above are uniformly suspended in the mixture. The pharmaceutical composition of the invention in the form of gel is thus obtained.

0026The composition of the invention in the form of film or sheet is obtained by deaerating the just mentioned gel, and subjecting the same to the casting process. The film or sheet may also be prepared by compression molding, extrusion or calendering. The most suitable forming process among others is selected depending on the physico-chemical properties of the polymers employed.

0027The bar-like composition of the invention is prepared in the similar manner as the film or sheet, but through extrusion.

0028The weight ratio of the particles to the soluble polymer may range from 1:99 to 99:1 on the basis of dry weight. The composition of the particles: soluble polymer in a ratio of 10:90-70:30 is preferred.

0029Therapeutically active ingredient or ingredients used for the preparation of the composition of the invention are selected from those effective for prevention or treat­ment of periodontal diseases, for example, germicides, such as chlorhexidine, Ag protein, glyceryl iodide, phenol, benzalkonium chloride, cetylpyridinium chloride, and the like; antimicrobial agents, such as ampicillin, tetra­cycline, benzylpenicillin, clindamycin, cefalexin, erythro­mycin, chloramphenicol, fragiomycin sulfate, and the like; anti-inflammatory agents, such as ibuprofen, indomethacin, ketoprofen, mefenamic acid, antipyrine, pranoprofen, ibufenac, tiaramide hydrochloride, prednisolon, dexametha­sone, triamcinolone acetonide, prostaglandine, and the like; plaque solubilizing agents, such as dextranase, protease, amylase and the like; collagenase inhibitors obtained from the extraction of crude drugs, such as gambir-catechu known in the name of "asenyaku"; local anesthetics, such as tetracaine hydrochloride, ethyl aminobenzoate, and the like; antihistaminic agents, such as chlorphenilamine maleate, diphenhydramine, and the like; hemostatic agents such as tranexamic acid, and the like.

0030The solid composition of the invention in the form of film, sheet or bar can be prepared in different sizes. However, the convenient size of the film or sheet may be 0.1-0.5 mm in thickness, 0.5-3 mm in width, and 10-50 mm in length. The size of the bar may generally range from 0.5 to 1.5 mm in diameter and from 10 to 50 mm in length. Further­more, the composition of the invention may be cut in suit­able size by the user depending on several factors, such as severity of the disease, and the width and depth of the locus to be applied. The composition of the invention can be applied to the periodontal pocket or paradentium by insertion, injection, or rubbing according to the type of formulation.

0031The pharmaceutical composition of the invention exhibits a desirably controlled release pattern of the active ingredient(s). Such controlled release is attained by careful selection of a particular condition with respect to the following variables. <ul id="ul0002" list-style="none"><li>(1) Distribution ratio of an active ingredient between the particles and the soluble polymer.</li><li>(2) The particle size to be dispersed in the soluble polymer.</li><li>(3) Selection of non-soluble polymer or polymers which permits the modification of both the solubility of particles and diffusion velocity of an active ingredient in the particles in the manner as desired.</li><li>(4) The use of one or more kind(s) of particles which differ from each other in their solubilities.</li><li>(5) The ratio of the amounts of particles and soluble polymer to be combined.</li><li>(6) Selection of soluble polymer or polymers having desired viscosity.</li></ul>

0032By selection of suitable conditions in regard to the above variables, there is obtained the pharmaceutical composition of the invention which releases one or more of active ingredients in the manner as contemplated. Since the surface of the composition of the invention is mainly composed of water soluble polymer, is does not give any uncomfortable feeling to patients.

0033The following examples are presented by way of illustration of specific embodiments of the pharmaceutical composition of the invention. In examples, part or parts are represented by weight basis.

Example 1

0034Poly(lactic acid) (10 parts) and tetracycline hydrochloride (2 parts) are dissolved in methylene chloride (100 parts). Flow casting of the resultant mixture yields a sheet, which is ground into particles having an average size of 50µ.

0035The particles (10 parts) and hydroxypropyl cellu­lose (10 parts) are uniformly admixed. The mixture is blended with water, extruded with pressure, and dried. The bar-like shaped product of 1.0 mm diameter is thus obtained.

Example 2

0036Methacrylic acid / methyl methacrylate copolymer (1:2 molar ratio) (80 parts) is dissolved in ethanol (1000 parts). In the solution are suspended or dissolved indo­methacin (5 parts) and triacetin (20 parts), and the mixture is casted into a sheet, which is then pulverized into particles having an average size of 80µ.

0037Hydroxypropyl cellulose (10 parts) is dissolved in water (1000 parts), and tetracycline (25 parts) is added to the resultant solution, after adjusting to pH 6.0 by addition of hydrochloric acid. The resultant mixture (80 parts) are uniformly admixed with the particles obtained above (20 parts) to yield the product in a gel form.

Example 3

0038The particles produced in Example 2 (20 parts), methyl cellulose (80 parts) and tetracycline hydrochloride (5 parts) are uniformly admixed, and the resulting mixture is pressed to a sheet having a 500µ thickness.

Experiment 1

0039The controlled release of an active ingredient was evaluated on the pharmaceutical composition of the invention which contains two kinds of active ingredients.

Method and materials

(1) Preparation of Sample

0040Methacrylic acid / methyl methacrylate copolymer (1:2 molar ratio) (80 parts) was dissolved in ethanol (1000 parts). Triacetin (20 parts) and tetracycline hydrochloride (6 parts) were then mixed with the resultant solution. The mixture was casted on a Teflon tray and dried at 40°C. The resultant sheet was pulverized into particles of 105µ to 177µ in size.

0041On the other hand, hydroxypropyl cellulose (viscosity of 2% aqueous solution is 1000 to 4000 cp at 20°C) (one part) was dissolved in water (99 parts). In the solution was dissolved tetracaine hydrochloride (0.03 part).

0042The hydroxypropyl cellulose solution and the particles are uniformly admixed at a weight ratio of 100:0.5, and the mixture is deaerated, casted on a Teflon tray with care to ensure the constant thickness, and air-­dried to yield a film having 300µ thickness.

0043In a solution of hydroxypropyl cellulose (1 part) dissolved in water (100 parts) were dissolved tetracycline hydrochloride (0.02 part) and tetracaine hydrochloride (0.02 parts), and the mixture was adjusted to pH 6, deaerated, casted on a Teflon tray, air-dried to obtain a film having 300  thickness, which was employed as a reference.

(2) Evaluation of Dissolution Rate

0044The dissolution rates of the active ingredients released from the films obtained above were measured using a phosphate buffer (500ml), pH 7.2, at 37°C, in accordance with the Rotating Basket Method (100 rpm) of Japanese Pharmacopoeia (X).

Results

0045The dissolution profiles of the film of the invention and that of the reference are respectively shown in Fig. 1 and Fig. 2 of the accompanying drawing. The abscissa indicates immersion time and the ordinate indicates the dissolution rate. Fig. 1 shows that two active ingre­dients were released from the film with different release patterns while Fig. 2 shows the same and identical release pattern of the two active ingredients. Thus, this experi­ment illustrates that the composition of the invention permits separate control of the release patterns of two active ingredients. It also teaches that the composition of the invention in the form of a sustained release formulation may be obtained where the same and identical active ingredi­ent rather than the two active ingredients is employed in this experiment.