Etorphine (M99) is a semi-synthetic

opioid Opioids are a class of Drug, drugs that derive from, or mimic, natural substances found in the Papaver somniferum, opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, ...

possessing an

analgesic An analgesic drug, also called simply an analgesic, antalgic, pain reliever, or painkiller, is any member of the group of drugs used for pain management. Analgesics are conceptually distinct from anesthetics, which temporarily reduce, and in s ...

potency approximately 1,000–3,000 times that of

morphine Morphine, formerly also called morphia, is an opiate that is found naturally in opium, a dark brown resin produced by drying the latex of opium poppies (''Papaver somniferum''). It is mainly used as an analgesic (pain medication). There are ...

. It was first prepared in 1960 from oripavine, which does not generally occur in opium poppy extract but rather the related plants '' Papaver orientale'' and '' Papaver bracteatum''. It was reproduced in 1963 by a research group at MacFarlan Smith in Edinburgh, led by Kenneth Bentley. It can 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 simi ...

Veterinary use

Etorphine is available legally only for

veterinary Veterinary medicine is the branch of medicine that deals with the prevention, management, diagnosis, and treatment of disease, disorder, and injury in non-human animals. The scope of veterinary medicine is wide, covering all animal species, both ...

use and is strictly governed by law. It is often used to immobilise

elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...

s and other large mammals.

Diprenorphine Diprenorphine (brand name Revivon; former developmental code name M5050), also known as diprenorfin, is a non-selective, high-affinity, weak partial agonist of the μ- (MOR), κ- (KOR), and δ-opioid receptor (DOR) (with equal affinity) which ...

(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 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 that

diprenorphine Diprenorphine (brand name Revivon; former developmental code name M5050), also known as diprenorfin, is a non-selective, high-affinity, weak partial agonist of the μ- (MOR), κ- (KOR), and δ-opioid receptor (DOR) (with equal affinity) which ...

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 immobilise an

African elephant African elephants are members of the genus ''Loxodonta'' comprising two living elephant species, the African bush elephant (''L. africana'') and the smaller African forest elephant (''L. cyclotis''). Both are social herbivores with grey skin. ...

and a 2–4 mg dose is enough to immobilise a

black rhinoceros The black rhinoceros (''Diceros bicornis''), also called the black rhino or the hooked-lip rhinoceros, is a species of rhinoceros native to East Africa, East and Southern Africa, including Angola, Botswana, Eswatini, Kenya, Lesotho, Malawi, Moza ...

Pharmacology

Etorphine is a potent, non-selective full agonist of the μ-, δ-, and

κ-opioid receptor The κ-opioid receptor or kappa opioid receptor, abbreviated KOR or KOP for its ligand ketazocine, is a G protein-coupled receptor that in humans is encoded by the ''OPRK1'' gene. The KOR is coupled to the G protein Gi/G0 and is one of four re ...

s. It has a 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 Pa ...

for the nociceptin receptor. Etorphine has an LD₅₀ of 3 μg in humans.

Legal status

In Hong Kong etorphine is regulated under Schedule 1 of Chapter 134 of the ''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 HKD$10,000. The penalty for trafficking or manufacturing the substance is a HKD$5,000,000 fine and life imprisonment. Possession for consumption without licence from the Department of Health is illegal, with a HKD$1,000,000 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 immobilise large animals. In the United States etorphine is listed as a Schedule I drug with an ACSCN of 9056, although its hydrochloride

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

is classified as Schedule II with an ACSCN of 9059. In the United Kingdom, 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 and Acetorphine. (Data from 2022)

In popular culture

* The fictional character

Dexter Morgan Dexter Morgan (born Dexter Moser), also known as The Bay Harbor Butcher, is a fictional serial killer and the antihero protagonist of the ''Dexter'' book series written by Jeff Lindsay (writer), Jeff Lindsay, as well as the Dexter (TV series), tel ...

uses Etorphine M-99 to capture and sedate his victims in the television series ''Dexter'' and ''Dexter: Original Sin''. * In the film ''The Meg'' etorphine is used to neutralise the first

megalodon ''Otodus megalodon'' ( ; meaning "big tooth"), Common name, commonly known as megalodon, is an extinction, extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Earl ...

References

External links