Intraruminal devices.

Intraruminal boluses are drug delivery devices designed to provide long term delivery of drug to the reticulo-rumen compartments of ruminant animals. This cavity is the site of the bacterial fermentation and breakdown of foodstuffs and represents an ideal site for the long term delivery of drugs and nutrients to these grazing animals. Often such animals are 'turned out' in the spring to spend much of the spring, summer and autumn seasons grazing open range. As such, the administration of drugs during the grazing season is complicated by the need to first retrieve the animals prior to drug administration. Long term delivery of drug circumvents this problem providing for decreased costs and improved efficiencies for the farmer. Numerous types of delivery devices have been developed to meet this need. This review summarizes the various approaches that have been developed, provides information on the critical design features and reviews the relevant anatomy and physiology of these animals. Some comments are provided regarding needed future developments for this class of drug delivery system.