Mechanisms of solute release from porous hydrophilic polymers

Porous hydrophilic discs were prepared from two grades of poly(vinyl alcohol) of varying degree of hydrolysis. The influence of the molecular size of the tracer used (potassium chloride, phenylpropanolamine hydrochloride and bovine serum albumin), that of the addition of a second water-soluble polymer poly(N-vinyl-2-pyrrolidone) and poly(ethylene glycol)) and the effect of the tracer/excipient ratio on the release profile were examined. Finally the role of the dynamic swelling and the dissolution of the polymer matrix on the release mechanism are discussed.