RELEASE OF CLONIDINE HYDROCHLORIDE FROM PRESSURE-SENSITIVE ADHESIVE MATRICES PREPARED BY EMULSION-TYPE ACRYLATE POLYMERS

The in vitro release characteristics of a model hydrophilic drug, clon idine hydrochloride, from pressure sensitive adhesive (PSA) matrices p repared by two coating methods, direct coating on a backing layer and transfer coating (coating on a liner layer and transfer of the resulti ng PSA onto a backing layer), with different drying temperatures were measured and evaluated, Hydrophilic polymer, polyethylene glycol (PEG) , hydroxypropyl cellulose (HPC) or polyvinyl pyrrolidone (PVP) was add ed to the matrices to increase the drug release rate. A lower drying t emperature showed a higher release rate, Each polymer increased the re lease rate compared to control (without polymer), A PSA matrix with HP C showed a low initial burst followed by a prolonged release, whereas those with PEG and PVP exhibited a high initial burst and a subsequent low release rate. The difference in the initial burst was related, to a considerable degree, to the affinity of the matrices against water. It was also related to the amount of drug on the matrix surface. The transfer coating and addition of HPC were useful in suppressing the hi gh initial burst and in maintaining a high sustained release rate of t he drug from the PSA matrices.