Pharmaceutical composition for treating periodontal diseases

This invention relates to a pharmaceutical composition which is applied to a periodontal pocket or the paradentium for the purpose of treating periodontal diseases.

The pharmaceutical composition, which is provided in the form of a gel, a sheet, a film or a bar-like formulation, releases a controlled and effective amount of an active ingredient to the periodontal pocket or paradentium.

The term periodontal diseases is a general term used to describe various inflammatory diseases of the 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 the marginal gingiva area and eventually reaches the alveolar bone, the diseases can be roughly divided, on the basis of the degree of inflammation, into gingivitis in which the inflammation is limited to the gingiva tissue, and paradentitis in which the inflammation is chronic and found in the alveolar bone. However, particular diseases like juvenile paradentitis and acute necrotizing ulcerative gingivitis are also included in the definition of periodontal diseases.

<img file="CA1300515C_D0001.tif" />

- 2 Paradenfcitis, which was once called alveolar pyorrhea, is characterized by remarkable symptoms which include inflammation of gingiva, formation of periodontal pockets, bleeding and pus discharge from said periodontal pockets, and it results in the resorption of the alveolar bone, loosening of the tooth, and loss of the tooth.

The consensus of most investigators is that periodontal diseases are caused by the bacteria present in dental plaque which forms in periodontal pockets. Efforts have concentrated on the discovery of the pathogenic bacteria responsible for said diseases. At the present time, an attributable major pathogen is recognized to be a certain nigral pigment-producing bacteria, i.e., genus Bacteroides. However, other genus of bacteria including Actinobacillus, Capnocytophaga, Fusobacterium and Spirochetes may be included in the causative pathogens. In any case, it has been established that periodontal diseases cannot be attributed to all bacteria present in the dental plaque.

Periodontal diseases have previously been treated in several ways, for example, exhaustive scaling of plaque in the periodontal pockets, root plaining, gingivectomy to eliminate the periodontal pocket, or surgical curettage to excise inflammatory tissues. These treatments have been effective to some extent but are not entirely satisfactory.

On the other hand, pharmacotherapy has also been conducted using drugs selected from germicides, antiinflammatory agents, plaque solubilizing agents, hemostyptics, and the like. These drugs are used in formulations suitable for internal use or massotherapy (e.g., dentifrices, ointments, and the like). However, they are not satisfactory for the treatment of periodontal diseases because their internal use barely permits the selective migration of the drug to the lesional region, and massotherapy is not successful in solubilizing the plaque which is present beneath the gingival margin.

Recently, strips made from polymers and active ingredients for the treatment of periodontal diseases have been developed. These strips are said to be useful for the treatment of plaque and inflammation beneath the gingival margin. The strips can be applied directly to the lesional region to be treated, and the active ingredient can therefore be selectively concentrated on the desired site. This modified therapeutic method has proved to be more effective than any conventional pharmacotherapy. For instance, J.M. Goodson et al. disclose the implantation of a hollow fiber, which contains germicides, into the gingival region (J. Clinical Periodontology, 1979: 6: 83-92). M. Addy et al. have reported the insertion of strips, which had been prepared from a mixture of an insoluble polymer i.e., polyethylmethacrylate and ger15 micides, into periodontal pockets (J. Periodontal, 693, Nov. 1982). In addition, insertion of strips, prepared from a mixture of a soluble polymer and a drug, into the lesional region, i.e., periodontal pockets, has also been reported (Japan Patent Publication No. 59-222406).

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

The 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, a strip which comprises a soluble polymer as a base or carrier permits rapid release of the active ingredient. Accordingly, it does not afford a constant therapeutical effect and, therefore, has poor practical use .

As a result of an extensive study 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 discomfort to patients, it has been found that the use of a two-phase carrier base, which consists of particles comprising a polymer having limited solubility in water and a water soluble polymer used for dispersing such particles, meets the requirements mentioned above.

Thus, the present invention provides a controlledreleased pharmaceutical composition in the form of a gel, sheet, film, or bar to be inserted or placed into a periodontal pocket for treating a periodontal disease, said composition comprising a therapeutically effective amount of at least one active ingredient effective for the treatment of the periodontal disease, said active ingredient being dispersed in a two-phase carrier consisting of (a) a continuous phase consisting of a water-soluble polymer capable dissolving in water at a concentration of more than 1% by weight irrespective of pH, and (b) a discontinuous phase consisting of solid particles composed of a polymer capable of dissolving in water at a concentration of between about 0.1% and 1.0% by weight or solid particles composed of a polymer capable of dissolving in water having a pH higher than 4 or a pH lower than 6, at a concentration of more than 1% by weight, said particles having an average size ranging from 1 μ-m to 500 Mm and being dispersed in said water-soluble polymer, with the weight ratio of said particles to said water-soluble polymer ranging from 1:99 to 99:1 on a dry weight basis, said watersoluble polymer being selected from the group consisting of methyl cellulose, hydroxypropyl cellulose, sodium carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, sodium alginate, propylene glycol alginate, pullulan, tragacanth, xanthan gum, chitosan, polyethylene oxide, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, and salts thereof, and said solid particles being selected from the group consisting

- 4a of poly(glycolic acid), poly(lactic acid), polytetramethylglycolide, polydiethylglycolide, poly-e-caprolactone, poly (DL-decalactone), poly(alkyleneadipate), methylacrylate/ methacrylic acid copolymer, methacrylate/methacrylic acid/ octylacrylate copolymer, ethyl acrylate/methacrylic acid copolymer, methylacrylate/methacrylic acid/methylmethacrylate copolymer, methyl methacrylate/methacrylic acid copolymer, cellulose acetate phthalate, cellulose acetate succinate, cellulose acetate maleate, starch acetate phthalate, amylose acetate phthalate, methyl cellulose phthalate, hydroxypropylmethyl cellulose phthalate, hydroxyethyl ethylcellulose phthalate, hydroxypropylmethyl cellulose acetate succinate, carboxymethylethyl cellulose, polyvinylalcohol phthalate, polyvinyl acetate phthalate, polyvinylacetal phthalate, polyvinylbutylate phthalate, methylmethacrylate/dimethylaminoethyl methacrylate copolymer, and polyvinylacetal/ dimethylamino acetate.

Fig. 1 shows the dissolution profile of two active ingredients contained in the pharmaceutical composition of the invention in the form of a film.

Fig. 2 shows the dissolution profile of two active ingredients contained in a conventional composition.

The term a polymer having 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.

For 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.

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. Sparingly 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.

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

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

Specific examples of the insoluble polymer are ethyl cellulose, cellulose acetate, ethyl methacrylate / tri20 methylammonioethyl methacrylate chloride copolymer, and the like. The sparingly soluble polymer includes, for instance, biodegradable polymers for example, polyglycolic acid, polylactic acid, polytetramethylglycolide, polydiethylglycolide, polycaprolactone, poly (DL-deca25 lactone), poly(alkyleneadipate), copolymers thereof, and ion exchange resins.

Polymers which dissolve in an aqueous medium having a pH above 4 include copolymers consisting of acrylic acid, methacrylic acid and/or esters thereof, for example, 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 for example, cellulose acetate

<img file="CA1300515C_D0002.tif" />

- 6 phthalate, cellulose acetate succinate, cellulose acetate maleate, starch acetate phthalate, and amylose acetate phthalate, hemiesters of organic bivalent acid with alkylated polysaccharides for example, methyl cellulose phthalate, hemiesters of organic bivalent acid with hydroxypropylmethyl cellulose phthalate, and hydroxyethyl ethyl cellulose phthalate, hydroxypropylmethyl cellulose acetate succinate, alkyl esters of carboxyalkylated polysaccharide for example, carboxymethylethyl cellulose, hemiesters of organic bivalent acid with polyvinyl alcohol and its derivatives for example, polyvinyl alcohol phthalate, polyvinyl acetate phthalate, polyvinyl acetal phthalate, and polyvinyl butylate phthalate.

Polymers which dissolve .in an aqueous medium having a pH below 6 include dimethylaminoethyl methacrylate / methyl methacrylate copolymer, polyvinylacetal / dimethylamino acetate, cellulose acetate dibutylhydroxypropyl ether, and the like.

Specific 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 salts thereof.

The pharmaceutical composition of the present invention may be prepared by dispersing one or more active ingredients into a non-soluble polymer, or 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, a sheet or a bar-like shape, or into a semi-solid material such as a gel or an ointment.

In more detail, one or more non-soluble polymers are dissolved, as the first step, in an appropriate organic

<img file="CA1300515C_D0003.tif" />

solvent. To the resultant solution is dissolved or dispersed one or more active ingredients, and the mixture is formed into a film or a sheet by a casting method. The resultant solid material is ground into particles.

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

On the other hand, one or more water soluble polymers can be dissolved in a suitable solvent. The solvent may contain, if desired, one or more 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 a gel is thus obtained.

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

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

The 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.

Therapeutically active ingredient or ingredients useful for the preparation of the composition of the invention are selected from those effective for the prevention or treatment of periodontal diseases, for example, germicides, i.e., chlorhexidine, Ag protein,

<img file="CA1300515C_D0004.tif" />

glyceryl iodide, phenol, benzalkonium chloride, cetylpyridinium chloride, and the like; antimicrobial agents, i.e., ampicillin, tetracycline, benzylpenicillin, clindamycin, cefalexin, erythromycin, chloramphenicol, fragiomycin 5 sulfate, and the like; anti-inflammatory agents, i.e., ibuprofen, indomethacin, ketoprofen, mefenamic acid, antipyrine, pranoprofen, ibufenac, tiaramide hydrochloride, prednisolon, dexamethasone, triamcinolone acetonide, prostaglandine, and the like; plaque solubilizing agents, 10 i.e., dextranase, protease, amylase and the like; collagénase inhibitors obtained from the extraction of crude drugs, i.e., gambir-catechu known by the name asenyaku; local anesthetics, i.e., tetracaine hydrochloride, ethyl aminobenzoate, and the like; antihistaminic agents, i.e., 15 chlorphenylamine maleate, diphenhydramine, and the like; hemostatic agents i.e., tranexamic acid, and the like.

The solid composition of the invention in the form v of a film, a sheet or a bar can be prepared in different sizes. However, a convenient size of the film or sheet 20 is 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 into a suitable size by the user depending on 25 several factors, including, the severity of the disease, and the width and depth of the locus to be treated. The composition of the invention can be applied to the periodontal pocket or the paradentium by insertion, injection, or rubbing depending on the formulation used.

The pharmaceutical composition of the invention exhibits a desirably controlled release pattern of the active ingredient(s). Such controlled release is attained by the careful selection of particular conditions with respect to the following variables.

(1) Distribution ratio of the active ingredient between the particles and the soluble polymer.

(2) The particle size to be dispersed in the soluble polymer .

(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.

(4) The use of one or more kind(s) of particles which differ from each other in their solubilities.

(5) The ratio of the amounts of particles and soluble polymer to be combined.

(6) Selection of soluble polymer or polymers having desired viscosity.

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

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

Example 1

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

The particles (10 parts) and hydroxypropyl cellulose (10 parts) were uniformly admixed. The mixture was blended with water, extruded with pressure, and dried.

The bar-like shaped product of 1.0 mm diameter was thus obtained .

Example 2

Methacrylic acid / methyl methacrylate copolymer

13005.15

- 10 (1:2 molar ratio) (80 parts) was dissolved in ethanol (1000 parts). In the solution were suspended or dissolved indomethacin (5 parts) and triacetin (20 parts), and the mixture was cast into a sheet, which was then pulverized into particles having an average size of 80μ.

Hydroxypropyl cellulose (10 parts) was dissolved in water (1000 parts), and tetracycline (25 parts) was added to the resultant solution, after adjusting to pH 6.0 by addition of hydrochloric acid. The resultant mixture (80 parts) was uniformly admixed with the particles obtained above (20 parts) to yield the product in a gel form. Example 3

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

Experiment 1

The controlled release of the active ingredient was evaluated for the pharmaceutical composition of the invention which contained two kinds of active ingredients. Method and materials (1) Preparation of Sample

Methacrylic 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 cast on a Teflon* tray and dried at 40°C. The resultant sheet was pulverized into particles of 105μ to 177μ in size.

On 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).

The hydroxypropyl cellulose solution and the particles were uniformly admixed at a weight ratio of 100:0.5, and * Trade Mark

-lithe mixture was deaerated, cast on a Teflon* tray with care to ensure constant thickness, and air-dried to yield a film having 300μ thickness.

In 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, cast on a Teflon* tray, air-dried to obtain a film having 300p thickness, which was employed as a reference.

(2) Evaluation of Dissolution Rate The 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

The 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 drawings. 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 identi25 cal 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 two active ingredients is employed in this experiment.

* Trade Mark

<img file="CA1300515C_D0005.tif" />