Nalmefene (NMF)

Nalmefene is an opioid receptor antagonist used primarily in the management of alcohol dependence. Nalmefene is an opiate derivative similar in both structure and activity to the opioid antagonist naltrexone. Advantages of nalmefene relative to naltrexone include longer half-life, greater oral bioavailability and no observed dose-dependent liver toxicity. As with other drugs of this type, nalmefene can precipitate acute withdrawal symptoms in patients who are dependent on opioid drugs, or more rarely when used post-operatively to counteract the effects of strong opioids used in surgery. Nalmefene acts as a silent antagonist of the μ-opioid receptor and as a partial agonist of the κ-opioid receptor. It also possesses affinity for the δ-opioid receptor. Nalmefene differs from naltrexone by substitution of the ketone group at the 6-position of naltrexone with a methylene group (CH2), which considerably increases binding affinity to the μ-opioid receptor.