Etorphine

Etorphine (also known by the brand name M99) is a very potent opioid analgesic drug which is most commonly used for tranquilizing large animals such as elephants and rhinos. It is a semi-synthetic derivative of morphine and is roughly 10,000 times stronger than morphine. It is used for its sedative, analgesic, and tranquilizing effects and is administered by injection. Etorphine is a Schedule I controlled substance in the United States and is regulated internationally under the Convention on Psychotropic Substances.