Controlled release of pilocarpine hydrochloride from ethylene-vinyl alcohol copolymer matrices.

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Abstract
An ethylene-vinyl alcohol (EVAl) copolymer was evaluated as a new carrier for a long-acting delivery system of pilocarpine-hydrochloride. The release characteristics of pilocarpine-EVAl copolymer matrix (film or beads) systems were investigated in in vitro and in vivo [rabbit] test models. The results of the in vitro study suggested that the drug release rate could be easily controlled by modifying the proportions of ethylene and vinyl alcohol in the copolymer. Sustained release can be obtained by using EVAl copolymer containing more ethylene. The results of the in vivo study indicated that the use of the pilocarpine-EVAl copolymer bead system is more effective than that of the conventional liquid dosage form for prolonging the duration of a desired pupillary response. Its biocompatibility, flexibility and heat processability suggest that EVAl copolymer to be a good candidate for pilocarpine delivery into the eye.