Controlled-release compositions for administration of therapeutic agents to ruminants

Claim 1

In a controlled release composition for administering active agents to ruminants, comprising an effective amount of an active agent, up to about 50% by weight based on the total weight of the composition, in a matrix of a biologically acceptable water insoluble wax and a biologically acceptable surfactant; the improvement in said matrix comprising at least two surfactants having an HLB value of 8.5 or less, the HLB values of said surfactants differing by not more than 2 units thereby avoiding differential dissolution and non-uniform active agent release rate arising from the component with the higher HLB value diffusing faster than the component with the lower HLB value, said composition comprising the improved matrix having a melting point in excess of 39° C. and, when inserted as a solid into the rumen of a ruminant, having the property of controlled slow disintegration at the interface between said composition and ruminal fluid in the rumen of said ruminant.