Acetorphine

Acetorphine is a potent analgesic drug (painkiller), several thousand times stronger than morphine by weight. It is a derivative of the more well-known opioid etorphine, which is used as a very potent veterinary painkiller and anesthetic medication, primarily for the sedation of large animals such as elephants, giraffes and rhinos.

Acetorphine was developed in 1966 by the Reckitt research group that developed etorphine. Acetorphine was developed for the same purpose as etorphine itself, namely as a strong tranquillizer for use in immobilizing large animals in veterinary medicine. However despite showing some advantages over etorphine (for instance producing less toxic side effects in giraffes), acetorphine was never widely adopted for veterinary use, and etorphine (along with other tranquillizers such as carfentanil and azaperone) remains the drug of choice in this application.