Liposome-encapsulated oxymorphone hydrochloride provides prolonged relief of postsurgical visceral pain in rats.

Adequate pain control is necessary for optimal postsurgical recovery and humane treatment of laboratory and companion animals. Opioid drugs are currently the most potent analgesic agents available in human and veterinary medicine. Long-acting formulations of opioid drugs confer several important advantages over standard pharmaceutical preparations, especially for use in animals.