PRODUCTION OF ENDERMIC ADMINISTRATION PREPARATION

PURPOSE:To obtain the titled preparation capable of controlling release of drug, by dissolving a water-soluble drug having a specific molecular weight and polyvinyl alcohol in water, freezing and thawing. CONSTITUTION:0.05-1.0wt% based on the total amounts of a water-soluble drug having 200-1,000mol.wt., preferably clonidine hydrochloride, dibucaine hydrochloride, etc., having 200-500mol.wt. and 10-20wt% based on the total amounts of polyvinyl alcohol are dissolved in water and operation of freezing and thawing the aqueous solution is carried out once or more to give drug- containing polyvinyl alcohol hydrogel. An endermic absorption preparation containing the hydrogel. The preparation controls release of the drug by changing hardening of the hydrogel. The polyvinyl alcohol has high saponification degree and has preferably >=97 saponification degree. The hydrogel has different physical properties such as modulus of elasticity of storage, etc., depending upon grade of polyvinyl alcohol and difference in freezing and thawing operation.