OPIOID ANTAGONIST EFFECTS OF DEZOCINE IN OPIOID-DEPENDENT HUMANS

Dezocine is an opioid mu-partial agonist recently approved for use as an analgesic in the United States. This study characterized the relati ve agonist versus antagonist effects of dezocine in comparison to nalo xone (an opioid antagonist), hydromorphone (an opioid mu-agonist), and placebo (saline solution) in opioid-dependent volunteers. In a reside ntial laboratory, six volunteer male oploid abusers maintained on 30 m g/day oral methadone underwent pharmacologic challenges two to three t imes per week, 20 hours after the last dose of methadone. Challenges c onsisted of a double-blind intramuscular injection of dezocine (dose r ange, 7.5 to 60 mg), hydromorphone (5 and 10 mg), naloxone (0.1 and 0. 2 mg), or saline solution. Measures included physiologic indexes, self -reports of drug effects, and observer ratings of drug effects. Naloxo ne and hydromorphone produced characteristic antagonist-like and agoni st-like effects, respectively. Dezocine acted as an opioid antagonist, precipitating a withdrawal syndrome only slightly different from that produced by naloxone. Dezocine's antagonist effects were not directly dose related, but peaked at intermediate doses and declined at higher doses.