Nalmefene, sold under the brand name Revex among others, is a medication that is used in the treatment of opioid overdose and alcohol dependence.

[2][3] Nalmefene belongs to the class of opioid antagonists and can be taken by mouth, administered by injection, or delivered through nasal administration.

[8] In terms of its chemical structure and biological activity, nalmefene is similar to another opioid antagonist called naltrexone, as they are both derivatives of opiates.

[10] Intravenous doses of nalmefene have been shown effective at counteracting the respiratory depression produced by opioid overdose.

[17][18] In vivo evidence indicative of KOR activation, such as elevation of serum prolactin levels due to dopamine suppression and increased hypothalamic–pituitary–adrenal axis activation via enhanced adrenocorticotropic hormone and cortisol secretion, has been observed in humans and animals.

[15][19] Side effects typical of KOR activation such as hallucinations and dissociation have also been observed with nalmefene in human studies.

[21] In addition to MOR and KOR binding, nalmefene also possesses some, albeit far lower affinity for the δ-opioid receptor (DOR) (Ki = 16 nM), where it behaves as an antagonist.

[23] With oral administration, peak brain MOR occupancy of 87 to 100% was found after 3 hours with single or repeated dosing of nalmefene.

[5][35] The FDA granted the application for the nalmefene hydrochloride auto-injector fast track and priority review designations.

[35] The FDA granted approval of Zurnai to Purdue Pharma L.P.[35] As of 2012, nalmefene in pill form, used for the treatment of alcohol dependence and other addictive behaviors, is not available in the United States.