Etorphine is available legally only for veterinary use and is strictly governed by law. It is often used to immobilize elephants and other large mammals. Diprenorphine (Revivon) is an opioid receptor antagonist that can be administered in proportion to the amount of etorphine used (1.3 times) to reverse its effects. Veterinary-strength etorphine is fatal to humans. For this reason the package as supplied to vets always includes the human antidote along with the etorphine.
The human antidote is generally naloxone, not diprenorphine, and is always prepared before the preparation of etorphine to be immediately administered following accidental human exposure to etorphine. The LD50 in humans is 3 μg which led to the requirement that the medicine include an equal dose of an antidote, diprenorphine or naloxone.
One of its main advantages is its speed of operation, and more importantly, the speed that diprenorphine reverses its effects. The high incidence of side effects, including severe cardiopulmonary depression, has caused etorphine to fall into disfavor in general veterinary practice. However, its high potency, combined with the rapid action of both etorphine and its antagonist, diprenorphine, means that it has found a place for use in the capture of large mammals, such as rhinoceroses and elephants, where rapid onset and rapid recovery are both very important. The high potency of etorphine means that sufficient etorphine can be administered to large wild mammals by projectile syringe (dart).
Large Animal Immobilon is a combination of etorphine plus acepromazine maleate. An etorphine antidote Large Animal Revivon contains mainly diprenorphine for animals and a human-specific naloxone-based antidote, which should be prepared prior to the etorphine. A 5–15 mg dose is enough to immobilize an African elephant and a 2–4 mg dose is enough to immobilize a black rhinoceros.[5]
In Hong Kong, etorphine is regulated under Schedule 1 of Hong Kong's Chapter 134 Dangerous Drugs Ordinance. It can be used legally only by health professionals and for university research purposes. The substance can be given by pharmacists under a prescription. Anyone who supplies the substance without prescription can be fined $10,000 (HKD). The penalty for trafficking or manufacturing the substance is a $5,000,000 (HKD) fine and life imprisonment. Possession of the substance for consumption without license from the Department of Health is illegal with a $1,000,000 (HKD) fine and/or 7 years of jail time.[10]
In the Netherlands, etorphine is a Schedule I drug of the Opium Law. It is used only for veterinary purposes in zoos to immobilize large animals.[11]
^Bentley KW, Hardy DG (June 1967). "Novel analgesics and molecular rearrangements in the morphine-thebaine group. 3. Alcohols of the 6,14-endo-ethenotetrahydrooripavine series and derived analogs of N-allylnormorphine and -norcodeine". Journal of the American Chemical Society. 89 (13): 3281–3292. doi:10.1021/ja00989a032. PMID6042764.
^Bentley KW, Hardy DG (1963). "New potent analgesics in the morphine series". Proceedings of the Chemical Society. 220: 189–228. doi:10.1039/PS9630000189.
^"Etorphine HCl". Veterinary medicine for wildlife: immobilisation medicine for animals zoo animals. Zoo Pharm. Archived from the original on 2016-09-08. Retrieved 2013-10-11.
^Hawkinson JE, Acosta-Burruel M, Espitia SA (February 2000). "Opioid activity profiles indicate similarities between the nociceptin/orphanin FQ and opioid receptors". European Journal of Pharmacology. 389 (2–3): 107–114. doi:10.1016/S0014-2999(99)00904-8. PMID10688973.
^Riviere JE, Papich MG (2009-03-17). Riviere JE, Papich MG (eds.). Veterinary Pharmacology and Therapeutics. John Wiley & Sons. p. 32. ISBN978-0-8138-2061-3.
