Cyclazocine-induced sleep disruptions in nondependent addicts

After one adaptation night, the sleep of seven male nondependent opiate addicts was studied following intramuscular cyclazocine (0.125; 0.25; 0.50 mg/70 kg) or placebo at weekly intervals in a randomized double-blind crossover design. Drug effects were measured on sleep stages and several episodic phenomena. Cyclazocine caused dose-related increases in sleep latency, REMS latency, percent spindle sleep, and a marked increase over placebo in wakefulness, drowsiness, and shifts in sleep-waking states. Cyclazocine produced a dose-related decrease in all measures of delta sleep, and some measures of REMS, and a marked decrease below placebo of sleep efficiency and total REMS. All doses of cyclazocine caused sustained periods of waking with little muscle tension. Cyclazocine (0.5mg) consistently caused urination during periods of extended arousal; urination has not been seen after morphine or other opioids of the mu type. These studies indicate that cyclazocine has effects on human sleep which are in some ways similar and other ways dissimilar to morphine type analgesics. The results are consistent with the concept that cyclazocine is a mixed agonist-antagonist of the opioid type with agonist actions at the kappa receptor.