In situ formation of polymeric material

Drug – bio-affecting and body treating compositions – Solid synthetic organic polymer as designated organic active... – Ion exchange resin

Reexamination Certificate

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Details

C424S078080, C424S484000, C424S486000, C424S487000, C424S488000, C424S400000, C514S772000, C514S772100

Reexamination Certificate

active

06391294

ABSTRACT:

This invention relates to polymeric material, for example, coatings, films and gels, especially pharmaceutically acceptable bioadhesive coatings, films and gels and more specifically to improved methods for producing such coatings, films and gels.
Many polymers are known to be bioadhesive (i.e. able to adhere to biological surfaces, e.g. mucus, the skin, mucosal surfaces, epithelium etc.) and the value of this property is well recognised. For example, bioadhesives may be used to adhere active agents to specific sites in the body for local drug administration, or to coat particular parts of the body. However, when bioadhesives are applied to such surfaces in aqueous solution they may be easily washed off or mechanically removed, because the strength of adhesion of each individual bioadhesive molecule to the surface is not very high. This may lead to further problems if the bioadhesive materials contain active agents intended for use at one particular site, but which are washed away to other sites.
Thus to improve the retention of bioadhesives at a surface they may be formed into films. Such films may be formed either by chemical crosslinking or by physical interaction of the bioadhesive molecules as they come out of solution. However, all of the known methods of film formation have drawbacks with regard to their use at biological surfaces. For example, if bioadhesive films are formed before being applied to a surface (e.g. by weaving polymer strands or by slow evaporation of aqueous solutions of the polymers) they will be awkward to apply to relatively inaccessible parts of the body (e.g. the back of the throat or the underside of the tongue); furthermore, for a number of biopolymers, much of the bioadhesive character of the films may be lost if they become too dry.
Alternatively, current methods for forming bioadhesive films directly on a surface require the use of volatile solvents, which quickly evaporate to leave a film, but which are not suitable for use on sensitive areas of a body (e.g. open wounds, mucosal surfaces, etc.).
A need exists for coatings, gels and/or films, especially bioadhesive coatings, gels and films, capable of being formed directly on surfaces which avoids the use of volatile solvents.
A further need exists for a formulation which is capable of forming a bioadhesive coating, film or gel in situ and which may be provided to the consumer in stable form in a single dosage form containing both components.
According to the invention there is provided a pharmaceutically acceptable polymeric material formed in situ at a body surface, wherein the material is formed by the reaction of:
i) an anionic polymer or tripolyphosphate (component a); and
ii) a cationic polymer (component b) in the presence of water.
Further according to the invention there is provided a process for the preparation of a pharmaceutically acceptable polymeric material in situ at a body surface by applying
i) an anionic polymer or tripolyphosphate (component a) and;
ii) a cationic polymer (component b)
to the body surface wherein component a) is capable of reacting with component b) to form the polymeric material.
Preferably the polymeric material is a bioadhesive coating, film or gel.
Preferably, the polymers are applied sequentially and the first applied polymer is a bioadhesive polymer.
Preferably component a) has one or more acid (proton donor) groups, for example —COOH and/or —SO
3
H.
Preferably component b) has one or more basic (proton acceptor) groups, for example —NH
2
and/or NHCH
3
.
Component a) may be selected from any anionic polymers that are water-soluble or dispersible and that will form a coating, gel or film in the presence of component b). Preferred anionic polymers include water-soluble salts of hyaluronic acid, water-soluble salts of alginic acids (e.g. sodium alginate, potassium alginate), water-soluble or dispersible salts of polyacrylic acids (e.g. sodium carbomers), xanthan gum, acacia, pectins, sterculia, carrageenan salts, polylactic acid and water-soluble cellulose derivatives (e.g.sodium carboxymethyl cellulose). Most preferred anionic polymers for use in the present invention are water soluble or dispersible carbomer salts, water-soluble salts of alginic acids and water-soluble salts of cellulose derivatives.
Mixtures of anionic polymers may be used, as long as they do not themselves crosslink to form films until component b) is added to them.
The concentration of component a) in the the bioadhesive coating, gels or films of the invention will depend upon a number of factors (e.g. the strength of the film, gel or coating to be produced, the solubility of the polymers, the required viscosity of the solution etc.). Generally the concentration will preferably be selected from the range 0.1 to 75% weight to volume (w/v), more preferably 0.5 to 25% w/v based on the composition as a whole.
Component b) may be selected from any cationic polymers that are water-soluble or dispersible and that will form a coating, film or gel in the presence of component a). Preferred cationic polymers include water-soluble chitosan salts (e.g. chitosan chloride, chitosan acetate), polylysine, chondroitin salts, diethylaminoethyl dextran and keratin.
Mixtures of component b) may be used to form the bioadhesive films of the invention, as long as they do not interact to form a film themselves until they have been added component a).
The total amount of component b) in the bioadhesive coatings, films or gels of the invention will depend upon a number of factors including the amount of component a) used, the strength of film required, the effectiveness of component b), etc. Generally the concentration will be selected from 0.1 to 75% w/v, more preferably 0.5 to 25% w/v of the composition as a whole.
The preferred amount may be easily determined by simple experimentation, however the total weight ratio of component a) to component b) will generally be from 1:10 to 10:1, more preferably 1:2 to 2:1.
The balance of the coating, film or gel may be water, any other pharmaceutically effective carriers, fillers and/or excipients.
Where component a) is a water-soluble alginate salt, component b) is preferably selected from water-soluble chitosan salts; diethylaminoethyl dextran and chondroitin sulphate; most preferably a water-soluble chitosan salt.
Where component a) is a water-soluble or dispersible carbomer salt, component b) is preferably selected from water-soluble chitosan salts; diethylaminoethyl dextran and chondroitin sulphate; most preferably a water-soluble chitosan salt.
Where component a) is sodium carboxymethyl cellulose, component b) is preferably a water-soluble chitosan salt.
The bioadhesive coatings, films or gels of the invention may optionally further comprise one or more pharmaceutically active agents, for either local or systematic delivery depending upon the site of application of the coating, film or gel.
Suitable active agents for use in such coatings, films or gels of the invention include analgesics, anti-inflammatory agents and antipyretics (e.g. acetaminophen, ibuprofen, naproxen, diclofenac, ketoprofen, choline salicylate, benzydamine, buprenorphine, hydrocortisone, betamethasone); decongestants (e.g. pseudoephedrine, phenylephrine, oxymetazoline, xylometazoline); mineral salts (e.g. zinc gluconate, zinc acetate); cough suppressants (e.g. dextromethorphan, codeine, pholcodine); expectorants (e.g. guaiphenesin, n-acetylcysteine, bromhexine); antiseptics (e.g. triclosan, chloroxylenol, cetylpyridinium chloride, benzalkonium chloride, amylmetacresol, hexylresorcinol, dichlorobenzyl alcohol, benzyl alcohol, dequalinium chloride, silver sulphadiazine); cardiovascular agents (e.g. glyceryl trinitrate); local anaesthetics (e.g. lignocaine, benzocaine); cytoprotectants (e.g. carbenoxolone, sucralfate, bismuth subsalicylate); antiulcer agents (e.g. calcium carbonate, sodium bicarbonate, magnesium trisilicate, magaldrate, cimetidine, ranitidine, nizatidine, famotidine, omeprazole, pantoprazole); antihistamines (e.g. loratidine, terfenadine, diphenhydramine, chlorphenhydramine,

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