Oral controlled-release delivery of ivermectin in cattle via an osmotic pump.

Ivermectin, a potent antiparasitic agent with activity against internal and external parasites, was delivered to cattle at a controlled zero-order rate for 35 d via orally administered, specially weighted, ALZET 2ML4 osmotic pumps. The osmotic pumps delivered the drug consistently over the trial period. Steady-state levels in plasma were achieved in 7-14 d, and plasma concentration depletion curves were observed to start at approximately day 35, the theoretical delivery lifetime of the osmotic pumps. Bioavailability was estimated to be 40%, and dose rate-plasma steady-state interrelationships were shown to be linear.