Etorphine (M99) is a semi-synthetic

opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...

possessing an analgesic 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. T ...

. 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 compar ...

, 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 ...

'' and ''

Papaver bracteatum ''Papaver bracteatum'', also known as the Iranian poppy or Persian poppy and the great scarlet poppy (first described by Dr. N. Saharghi and l. Lalezari nature 213, 1244, 1967 doi:10.1038/2131244a0 ) is a sturdy hardy perennial poppy with large d ...

''. 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 a ...

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 g ...

Edinburgh Edinburgh ( ; gd, Dùn Èideann ) is the capital city of Scotland and one of its 32 council areas. Historically part of the county of Midlothian (interchangeably Edinburghshire before 1921), it is located in Lothian on the southern shore of t ...

, 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 Veterinary medicine is the branch of medicine that deals with the prevention, management, diagnosis, and treatment of disease, disorder, and injury in animals. Along with this, it deals with animal rearing, husbandry, breeding, research on nutri ...

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 ...

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 Naloxone, sold under the brand names Narcan (4 mg) and Kloxxado (8 mg) among others, is a medication used to reverse or reduce the effects of opioids. It is commonly used to counter decreased breathing in opioid overdose. Effects begin withi ...

, 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 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 ...

. One of its main advantages is its speed of operation, and more importantly, the speed that

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 a ...

maleate. An etorphine antidote Large Animal Revivon contains mainly diprenorphine for animals and a human-specific

-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 receptor The κ-opioid receptor or kappa opioid receptor, abbreviated KOR or KOP, 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 related receptors that bind op ...

s. 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 receptor ...

. Etorphine has an LD₅₀ of 30 μg in humans.

Legal status

Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delta i ...

, 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 ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

, 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 about ...

. 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 In chemistry, a hydrochloride is an acid salt resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base (e.g. an amine). An alternative name is chlorhydrate, which comes from French. An archaic alternative na ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

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 med ...

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 f ...

. (Datas from 2022)

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

Veterinary use

Pharmacology

Legal status

See also

References

External links