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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 i ...
potency approximately 1,000–3,000 times that of
morphine Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies (''Papaver somniferum''). It is mainly used as a pain medication, and is also commonly used recreationally, or to make other illicit opioids. There ...
. It was first prepared in 1960 from oripavine, which does not generally occur in opium poppy extract but rather the related plants ''
Papaver orientale ''Papaver orientale'', the Oriental poppy, is a perennial flowering plant native to the Caucasus, northeastern Turkey, and northern Iran. Oriental poppies grow a mound of leaves that are hairy and finely dissected in spring. They gather e ...
'' and '' Papaver bracteatum''. It was later reproduced in 1963 by a research group at
MacFarlan Smith MacFarlan Smith is a pharmaceutical research company based in Edinburgh, Scotland, founded in 1815. It is part of the Fine Chemical and Catalysts division of Johnson Matthey. Background J.F. Macfarlan J.F. Macfarlan Ltd was founded in 1780 as ...
in
Gorgie Gorgie ( ) is a densely populated area of Edinburgh, Scotland. It is located in the west of the city and borders Murrayfield, Ardmillan and Dalry. Name The name is thought to be Brythonic in origin. Early forms suggest it derives from ''gor ...
, Edinburgh, led by Kenneth Bentley. It can also be produced from
thebaine Thebaine (paramorphine), also known as codeine methyl enol ether, is an opiate alkaloid, its name coming from the Greek Θῆβαι, '' Thēbai'' (Thebes), an ancient city in Upper Egypt. A minor constituent of opium, thebaine is chemically similar ...
.


Veterinary use

Etorphine is available legally only for veterinary use and is strictly governed by law. It is often used to immobilize
elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae a ...
s 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 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 Acepromazine, acetopromazine, or acetylpromazine (commonly known as ACP, Ace, or by the trade names Atravet or Acezine 2, number depending on mg/ml dose) is a phenothiazine derivative antipsychotic drug. It was used in humans during the 1950s as ...
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 The black rhinoceros, black rhino or hook-lipped rhinoceros (''Diceros bicornis'') is a species of rhinoceros, native to eastern and southern Africa including Angola, Botswana, Kenya, Malawi, Mozambique, Namibia, South Africa, Eswatini, Tanzania ...
.


Pharmacology

Etorphine is an extremely potent, non-selective
full agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the a ...
of the μ-, δ-, and κ-opioid receptors. It also has relatively weak
affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Par ...
for the
nociceptin receptor The nociceptin opioid peptide receptor (NOP), also known as the nociceptin/orphanin FQ (N/OFQ) receptor or kappa-type 3 opioid receptor, is a protein that in humans is encoded by the ''OPRL1'' (opioid receptor-like 1) gene. The nociceptin recepto ...
. Etorphine has an LD50 of 30 μg 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 $10,000 (
HKD The Hong Kong dollar (, sign: HK$; code: HKD) is the official currency of the Hong Kong Special Administrative Region. It is subdivided into 100 cents or 1000 mils. The Hong Kong Monetary Authority is the monetary authority of Hong Kong and ...
). 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 The Opium Law (or ''Opiumwet'' in Dutch) is the section of the Dutch law which covers nearly all psychotropic drugs. Origin and history In 1912, the First International Opium Conference took place in The Hague, where agreements were made abo ...
. 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, 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 medi ...
and
Acetorphine Acetorphine is a potent opioid analgesic, up to 8700 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 ...
. (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 bupreno ...
- 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 medi ...
– 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