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| ECHA InfoCard | 100.035.017 |
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| Formula | C25H33NO4 |
| Molar mass | 411.542 g·mol−1 |
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Etorphine (M99) is a semi-syntheticopioid possessing ananalgesic potency approximately 1,000–3,000 times that ofmorphine.[1] It was first prepared in 1960 fromoripavine, which does not generally occur inopium poppy extract but rather the related plantsPapaver orientale andPapaver bracteatum.[2] It was reproduced in 1963 by a research group atMacFarlan Smith inGorgie,Edinburgh, led by Kenneth Bentley.[3] It can be produced fromthebaine.[4]
Etorphine is available legally only forveterinary use and is strictly governed by law. It is often used to immobilizeelephants 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 generallynaloxone, not diprenorphine, and is always prepared before the preparation of etorphine to be immediately administered following accidental human exposure to etorphine. TheLD50 in humans is 3 μg which led to the requirement that the medicine include an equivalent dose of an antidote.
One of its main advantages is its speed of operation, and more importantly, the speed thatdiprenorphine 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 plusacepromazine maleate. An etorphine antidoteLarge Animal Revivon contains mainly diprenorphine for animals and a human-specificnaloxone-based antidote, which should be prepared prior to the etorphine. A 5–15 mg dose is enough to immobilize anAfrican elephant and a 2–4 mg dose is enough to immobilize ablack rhinoceros.[5]
Etorphine is a potent, non-selectivefull agonist of theμ-,δ-, andκ-opioid receptors.[6][7] It has a weakaffinity for thenociceptin receptor.[8] Etorphine has an LD50 of 3 μg in humans.[9]
InHong Kong, etorphine is regulated under Schedule 1 of Hong Kong's Chapter 134Dangerous 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 theNetherlands, etorphine is a Schedule I drug of theOpium Law. It is used only for veterinary purposes in zoos to immobilize large animals.[11]
In the US, etorphine is listed as aSchedule I drug with an ACSCN of 9056, although itshydrochloridesalt is classified asSchedule II with an ACSCN of 9059.[12]
In the UK, under theMisuse of Drugs Act 1971, etorphine is controlled as a Class A substance.[13]
In Italy,Etorphine is illegal, as are the parent compoundsDihydroetorphine andAcetorphine. (Datas from 2022)[14]