A laboratory study of hydromorphone and cyclazocine on smoking behavior in residential polydrug users

The effects of cyclazocine and hydromorphone on spontaneous and laboratory cigarette smoking were compared in a double-blind, placebo-controlled, crossover study. Participants (seven men, one woman) received oral doses of placebo, cyclazocine (0.2, 0.4, and 0.8 mg) and hydromorphone (5 and 15 mg) in a randomized order on experimental days. Spontaneous smoking was recorded during two intervals on the experimental days: a 3-h period 5-8 h after drug administration (Interval 1), and the rest of the day (Interval 2). Measures of smoking topography and subjective and physiologic effects of a single cigarette were obtained on the experimental days. Neither hydromorphone nor cyclazocine significantly changed spontaneous smoking when compared to the placebo condition; however, compared to hydromorphone (5 mg), cyclazocine (0.4 and 0.8 mg) decreased spontaneous smoking during Interval 1. Hydromorphone (5 and 15 mg) and cyclazocine (0.4 and 0.8 mg) diminished smoking-induced increases in heart rate. Compared to the placebo condition, cyclazocine (0.2 and 0.4 mg) reduced exhaled carbon monoxide (CO) boost, a measure of smoke exposure. Further studies of the effects of kappa opioid agonists on smoking behavior may lead to a better understanding of the role of opiates in smoking behavior.