A synthetic opioid similar to morphine in chemical structure, which acts as a mixed opioid antagonist and agonist and formerly was used in the diagnosis and treatment of narcotic abuse and overdosage; (−)-(5 R,6 S)-9a-allyl-4,5-epoxymorphin-7-en-3,6-diol, C ₁₉ H ₂₁ NO ₃. [A trademark for this drug in the United States is Nalline.].
1950s; earliest use found in Journal of Pharmacological and Experimental Therapeutics. Shortened from N-allylnormorphine, an alternative name for the compound.