Controlled delivery of pilocarpine. 1. In vitro characterization of Gelfoam matrices.

The potential of Gelfoam absorbable gelatin sponge as a carrier for ophthalmic delivery of pilocarpine was examined. Prolonged in vitro release of pilocarpine was achieved through pharmaceutical modification of the device by embedding a retardant in the pores. The device embedded with cetyl ester wax released pilocarpine in a zero-order pattern (release exponent = 0.93 +/- 0.04) for up to 5 hr. This result corresponded well with a linear penetrant uptake by this device. The device impregnated with polyethylene glycol 400 monostearate exhibited anomalous drug transport with a release exponent of 0.63 +/- 0.02. The absorption of water by this retardant and the formation of a gel layer on the surface slowed the penetration of the release medium into the deeper sections of the matrix, as well as the rapid outward diffusion of drug, resulting in a prolonged release of pilocarpine.