1. Field of the Invention
The present invention relates to an antiinflammatory and analgesic gel preparation exhibiting excellent percutaneous absorption and good properties upon use.
2. Description of the Background Art
Diclofenac or its salts possess excellent antiinflammatory and analgesic action, and are widely used in clinics in an oral or rectal dosage form. When administered orally or rectally, they are known to cause various side effects, including gastrointestinal tract disturbance. Because of this reason, a preparation for external application has been proposed, by which the drug is percutaneously absorbed without going through gastrointestinal tract and exerts its action locally or systemically. However, since diclofenac and its salts are scarcely absorbed percutaneously, such a preparation had not been commercially sold.
Gel preparations, on the other hand, possess an advantage over other preparations for external application in terms of the good feeling upon use. When a gel preparation contains diclofenac or its salts as an active ingredient, there are problems that a high concentration of diclofenac or its salts may destroy the gel structure, and fluidize the gel or crystallize diclofenac or its salts over time.
The present inventors previously filed a patent application (WO92/07561) based on the finding that a gel preparation in which diclofenac or its salts are contained at a high concentration and in a stable manner can be obtained, if base components comprising a dibasic acid ester and a lower alcohol are gelatinized by using a nonionic polymer as a gelling agent.
The gel preparation, however, was not still satisfactory in its percutaneous absorption of diclofenac or its salts and properties upon use.
Development of an antiinflammatory and analgesic gel preparation which can exhibit excellent percutaneous absorption of diclofenac or its salts and good properties upon use has therefore been desired.
In view of this situation the present inventors have undertaken extensive studies and found that an antiinflammatory and analgesic gel preparation which can exhibit excellent percutaneous absorption of diclofenac or its salts and good properties upon use can be obtained by formulating a specific type of nonionic polymer into a composition comprising diclofenac or its salts, an ester of dibasic acid, and a lower alcohol, and by adjusting the viscosity and the yield value of the composition in specific ranges. The finding has led to the completion of the present invention.