THE IN-VITRO AND IN-VIVO PERFORMANCE OF AN OSMOTICALLY CONTROLLED DELIVERY SYSTEM - IVOMEC SR(R) BOLUS

The IVOMEC SR(R) (sustained release) bolus is an osmotically driven dr ug delivery system designed for the long-term delivery to cattle of th e antiparasitic drug, ivermectin. The bolus is administered orally by means of a balling gun and the weight of the bolus keeps it in the ret iculum/rumen for the lifetime of the animal. The onset of delivery is immediate upon placement in the rumen and effective doses are delivere d within the first week following administration. The steady-state del ivery rate of approximately 12 mg/day of ivermectin is maintained for a period of approximately 135 days, after which, delivery ceases quick ly. This duration is sufficient to provide season-long delivery of dru g to grazing cattle.