Oripavine

Oripavine
File:Oripavin.svg
IUPAC name 6,7,8,14-Tetradehydro-4,5α-epoxy- 6-methoxy-17-methylmorphinan-3-ol
Other names 3-O-demethyl-thebaine
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	467-04-9
PubChem	5462306
EC number	207-385-6
KEGG	C06175
MeSH	Oripavine
ATC code	N02A
SMILES
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C18H19NO3
Molar mass	297.35 g mol−1
style="background: #F8EABA; text-align: center;" colspan="2" | Pharmacology
Routes of administration	SC
Legal status	Schedule II(US)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Oripavine is an opiate 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 comparable to morphine, it is not used clinically due to its severe toxicity and low therapeutic index.

Pharmacological Properties

Oripavine possesses an analgesic potency comparable to morphine; however, it is not clinically useful due to severe toxicity and low therapeutic index. In both mice and rats, toxic doses caused tonic-clonic seizures followed by death, similar to thebaine. Oripavine has a potential for dependence which is significantly greater than that of thebaine but slightly less than that of morphine.

Bridged Oripavine Derivatives

Of much greater relevance are the properties of the large family of semi-synthetic oripavine derivatives classically synthesised by Diels-Alder reaction of thebaine with an appropriate dienophile followed by 3-O-demethylation to the corresponding bridged oripavine. These compounds were developed by the group led by KW Bentley in the 1960s, and represent the first series of "super-potent" μ-opioid agonists, with some compounds in the series being over 10,000 times the potency of morphine as an analgesic. The simple bridged oripavine parent compound 6,14-Endoethenotetrahydrooripavine is already 40x the potency of morphine, but adding a branched tertiary alcohol substituent on the C7 position results in a wide range of highly potent compounds.

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Drug name	R	Analgesic Potency (Morphine = 1)
	methyl	63
	ethyl	330
Etorphine	n-propyl	3200
	n-butyl	5200
	isobutyl	10
	n-pentyl	4500
	isopentyl	9200
	n-hexyl	58
O-desmethyl-7-PET	phenethyl	2200
	phenyl	34
	cyclopentyl	70
	cyclohexyl	3400

Other notable derivatives then result from further modification of this template, with saturation of the 7,8-double bond of etorphine resulting in the even more potent dihydroetorphine (up to 12,000x potency of morphine) and acetylation of the 3-hydroxy group of etorphine resulting in acetorphine (8700x morphine) - although while the isopentyl homologue of etorphine is nearly three times more potent, its 7,8-dihydro and 3-acetyl derivatives are less potent than the corresponding derivatives of etorphine at 11000x and 1300x morphine respectively. Replacing the N-methyl group with cyclopropylmethyl results in opioid antagonists such as diprenorphine (which is used as an antidote to reverse the effects of etorphine), and partial agonists such as buprenorphine, which is widely used in the treatment of opioid addiction.

Legal Status

Due to the relative ease of synthetic modification of oripavine to produce other narcotics (by either direct or indirect routes via thebaine), the World Health Organization's Expert Committee on Drug Dependence recommended in 2003 that oripavine be controlled under Schedule I of the 1961 Single Convention on Narcotic Drugs. On March 14, 2007, the United Nations Commission on Narcotic Drugs formally decided to accept these recommendations, and placed oripavine in the Schedule I.

Until recently, oripavine was a Schedule II drug in the United States by default as a thebaine derivative, although it was not explicitly listed. However, as a member state under the 1961 Single Convention on Narcotic Drugs, the US was obligated to specifically control the substance under the Controlled Substances Act following its international control by the UN Commission on Narcotic Drugs. On September 24, 2007, the Drug Enforcement Administration formally added oripavine to Schedule II.

References

de:Oripavin