It derivative of morphine that acts to reverse the effects of morphine and other narcotics . It counteracts narcotic-induced nervous system and respiratory system depression but is not effective against depression induced by other sedatives such as barbiturates . Nalorphine and other narcotic antagonists are useful in reversing the effects of narcotic overdoses. Because nalorphine causes withdrawal symptoms in addicts, it is administered to apparent ex-addicts to determine if they have returned to drug use. Nalorphine is marketed under the trade name Nalline.