Abstract
The in vitro release characteristics of a model hydrophilic drug, clonidine hydrochloride, from pressure sensitive adhesive (PSA) matrices prepared by two coating methods, direct coating on a backing layer and transfer coating (coating on a liner layer and transfer of the resulting 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 added to the matrices to increase the drug release rate. A lower drying temperature showed a higher release rate. Each polymer increased the release rate compared to control (without polymer). A PSA matrix with HPC 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 HPV were useful in suppressing the high initial burst and in maintaining a high sustained release rate of the drug from the PSA matrices.
