Nalorphine (INN; Lethidrone, Nalline), also known as N-allyl-normorphine, is a mixed opioid agonist-antagonist. It acts at two opioid receptors, at the mu receptor it has antagonistic effects and at the kappa receptors it exerts high-efficacy agonistic characteristics. It is used to reverse opioid overdose and (starting in the 1950s) in a challenge test to determine opioid dependence.