Butorphanol-precipitated withdrawal in opioid-dependent human volunteers.

The subjective, physiological and behavioral effects of hydromorphone, naloxone and butorphanol, an opioid agonist/antagonist analgesic, were studied in adult, male, methadone-dependent volunteers living on a clinical research ward. Drug conditions included saline placebo, 4 and 8 mg of hydromorphone HCl, 0.375, 0.75, 1.5, 3 and 6 mg of butorphanol tartrate and 0.1 and 0.2 mg of naloxone HCl. Drug conditions, given by i.m. injection, were tested in five subjects under double-blind conditions in 2.5-hr experimental sessions. Physiologic measures and subject- and observer-rated behavioral responses were measured before dosing and for 2 hr after drug administration. Hydromorphone decreased pupil diameter, and significantly increased ratings of "Good Effects" on the subjective measures. Naloxone precipitated opioid abstinence which was measurable on several subject- and observer-rated behavioral measures and physiological measures. Butorphanol produced effects which were generally similar to the effects of naloxone, indicating that butorphanol doses precipitate withdrawal signs and symptoms when administered to methadone-dependent humans. There were some differences in the withdrawal syndromes precipitated by naloxone vs. butorphanol, suggesting that multiple mechanisms may be involved in opioid withdrawal precipitation.