Human pharmacology and abuse potential of meptazinol

Meptazinol was assessed in nine opioid abusers according to a double-blind, randomized, crossover design to determine if it produced typical morphine effects. A comparison of physiologic and subjective effects was made between morphine, 7.5, 15, and 30 mg, meptazinol, 70, 140, and 280 mg, and placebo. Both drugs constricted pupils. Meptazinol, 140 and 280 mg, decreased body temperature. Valid relative potency estimates of morphine to meptazinol were obtained for self-reported liking, opiate symptoms, and pupillary constriction. Meptazinol did not increase euphoria or sedation scale scores but did increase dysphoria scale scores. In the therapeutic dose range, meptazinol produced miosis, morphine-like identification and symptoms, limited liking, and some dysphoria. Dysphoria predominated at the 280 mg dose of meptazinol. From these data, it is concluded that meptazinol is not a typical morphine-like drug and has limited abuse potential.