Polyvinyl alcohol-methyl acrylate copolymers as a sustained-release oral delivery system

Low crystalline and crystalline polyvinyl alcohol-methyl acrylate (PVA-MA) copolymers were examined, because of their excellent flow and compressibility properties, as matrices for sustained-release tablets using phenylpropanolamine hydrochloride (PPA.HCl) as a model drug. Crystallinity of the copolymer affected the release characteristics from the tablet. Tablets made with low-crystalline PVA-MA provided sustained release of PPA, both in vitro and in vivo in dogs. PPA absorption from the low-crystalline PVA-MA tablet formulation was biphasic. An initial rapid phase was followed by a second, slower absorption phase which continued over 16 hr. Plasma PPA concentrations then declined with a half-life roughly parallel to the oral immediate-release half-lives. Oral bioavailability from the low-crystalline PVA-MA tablet formulation was 78.8 +/- 3.9%.