Nalmefene: blockade of intravenous morphine challenge effects in opioid abusing humans

No studies have assessed the dose-effect or duration of opioid blockade in opioid abusers produced by oral nalmefene: a mu-opioid antagonist. The pres ent study examined the profile and time course of oral nalmefene blockade o f subjective and physiological effects produced by intravenous morphine. To assess these effects, seven opioid abusers received oral nalmefene (0, 50 and 100 mg) followed by intravenous morphine (0, 10 and 20 mg) challenges e very 24 h for 96 h using a Latin square randomized cross-over design. The d uration of blockade varied by measure and dose. Both 50 and 100 mg nalmefen e blocked morphine's effects up to 48 h. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.