Human pharmacology and abuse potential of nalmefene

Nalmefene hydrochloride was administered to six male volunteers with histories of opiate abuse using a double-blind, randomized, Latin square design to determine if it produced typical morphine-like effects. A comparison of physiologic and subject- and observer-reported effects was made between morphine, 15 and 30 mg given intramuscularly; nalmefene, 25, 50, and 100 mg given orally; and placebo. Drowsiness or sleepiness was the most common drug effect reported after the administration of each treatment. Only morphine produced miosis and increased subject-reported euphoria and "drug liking." Neither drug increased Addiction Research Inventory subscale scores measuring dysphoria or sedation or produced changes on the Profile of Mood States questionnaire. Adverse effects reported only after the administration of nalmefene included agitation/irritability and muscle tension; these did not appear to be dose related. The data indicated that nalmefene did not produce typical morphine-like effects and has no apparent abuse potential.