Drug release from acrylic polymers via channels and cracks: in vitro studies with hydrocortisone.

Release of hydrocortisone sodium succinate from acrylic resin was found to occur readily on elution in water at 37 degrees C. Increasing the degree of hydration of the acrylic resin by the addition of hydroxyethyl methacrylate impaired rather than enhanced the release of drug. The mechanism for the release of drug is believed to be surface release and drug dissolution into and diffusion via cracks and channels which are formed by incorporation of the drug, producing a 'drug-modified polymer'. Diffusion through the polymer matrix is believed to be insignificant. The results obtained are discussed in relation to this proposed model for drug release. A simple method for the manufacture of the core of an intra-oral insert capable of delivering drugs with MW greater than 400 for systemic and topical oral drug delivery is described.