PULSED FSH RELEASE FROM AN IMPLANTABLE CAPSULE SYSTEM

An implantable capsule capable of bursting at a predetermined time is proposed for pulsed delivery of hormones. This delivery system consist s of a core of an effervescent agent enclosed in a hollow biodegradabl e poly(lactic-co-glycolic) acid (PLGA) polymer cylinder, closed at one end, and capped at the other end with a PLGA membrane. On immersion, entry of water through the membrane results in sufficient pressure inc rease (due to gas generation) to rupture ('burst') the membrane. The s ystem, designed to deliver FSH, for specific application in cattle rep roduction management, was tested in vitro and in vivo in rabbits. Burs t times from 2 h to 168 h have been obtained in vitro compared with pe ak FSH levels observed from 6 to 64 h in vivo. Among the parameters in vestigated (membrane thickness, capsule size, and core composition), t he core ingredient composition was the most influential factor in dete rmining the burst time.