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Etorphine (M99) is a semi-synthetic opioid possessing an
analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...
potency approximately 1,000–3,000 times that of morphine. It was first prepared in 1960 from
oripavine Oripavine is an opioid and the major metabolite of thebaine. It is the parent compound from which a series of semi-synthetic opioids are derived, which includes the compounds etorphine and buprenorphine. Although its analgesic potency is comp ...
, which does not generally occur in
opium poppy ''Papaver somniferum'', commonly known as the opium poppy or breadseed poppy, is a species of flowering plant in the family Papaveraceae. It is the species of plant from which both opium and poppy seeds are derived and is also a valuable ornamen ...
extract but rather the related plants '' Papaver orientale'' and '' Papaver bracteatum''. It was later reproduced in 1963 by a research group at MacFarlan Smith in Gorgie, Edinburgh, led by Kenneth Bentley. It can also be produced from thebaine.


Veterinary use

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 in humans is 30 Î¼g 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.


Pharmacology

Etorphine is an extremely potent, non-selective full agonist of the μ-, δ-, and κ-opioid receptors. It also has relatively weak affinity for the nociceptin receptor. Etorphine has an LD50 of 30 Î¼g in humans.


Legal status

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. 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. In the US, etorphine is listed as a Schedule I drug with an ACSCN of 9056, although its hydrochloride salt is classified as Schedule II with an ACSCN of 9059. For both, the 2013 annual aggregate manufacturing quota for both was zero so presumably veterinary supplies of the hydrochloride are imported from Germany and/or the UK. In the UK, under the
Misuse of Drugs Act 1971 The Misuse of Drugs Act 1971 is an Act of the Parliament of the United Kingdom. It represents action in line with treaty commitments under the Single Convention on Narcotic Drugs, the Convention on Psychotropic Substances, and the United Nation ...
, etorphine is controlled as a Class A substance. In Italy Etorphine is illegal, as are the parent compounds
Dihydroetorphine Dihydroetorphine was developed by K. W. Bentley at McFarlan-Smith in the 1960s and is a potent opioid analgesic used mainly in China. It is a derivative of the better-known opioid etorphine, a very potent veterinary painkiller and anesthetic m ...
and Acetorphine. (Datas from 2022)


See also

*
6,14-Endoethenotetrahydrooripavine 6,14-Endoethenotetrahydrooripavine is the central nucleus, or backbone, of a class of morphinan opioids known as the Bentley compounds and may be considered their "privileged scaffold". These include but are not limited to etorphine and buprenor ...
- the central nucleus of all Bentley compound opioids under which class etorphine falls *
Dihydroetorphine Dihydroetorphine was developed by K. W. Bentley at McFarlan-Smith in the 1960s and is a potent opioid analgesic used mainly in China. It is a derivative of the better-known opioid etorphine, a very potent veterinary painkiller and anesthetic m ...
– a close analog of etorphine that has been used as an opioid painkiller for human usage in China *
Thienorphine Thienorphine is a very potent, extremely long-acting, orally-active opioid analgesic with mixed agonist–antagonist properties which was developed by the Beijing Institute of Pharmacology and Toxicology as a potential treatment for opioid depend ...
* Opioid potency comparison


References


External links


Opioids.com
page on etorphine

{{Opioidergics Analgesics Delta-opioid receptor agonists 4,5-Epoxymorphinans Ethers Semisynthetic opioids Kappa-opioid receptor agonists Mu-opioid receptor agonists Nociceptin receptor agonists Phenols Tertiary alcohols