The present invention provides a composition comprising an opioid agonist, and a polymer-antagonist conjugate. The polymer-antagonist conjugate preferably does not hydrolyze upon administration to a patient, and does not bind to the opioid receptors. The covalent bond between the polymer and the antagonist in the conjugate is broken over a defined period of time to release the antagonist into the formulation. The released antagonist attenuates the liking of the agonist, thereby eliminating the incentive to the diversion of the medicines.
