Parenteral meptazinol: a US clinical trial.

The effectiveness and safety of i.m. meptazinol (50, 100, 200mg), a unique mu 1-selective opioid analgesic, was compared with i.m. morphine (4, 8 and 16 mg) in 128 cancer patients with moderate to severe postoperative pain; 102 patients completed the crossover study. The study design was a modification of the sequential, twin-crossover assay. Meptazinol was found to be one-fifteenth to one-twentieth as potent as morphine on a mg basis, and to provide a more rapid time to peak effect (about 40 min vs 1 h) than morphine. Morphine improved selected aspects of mood while meptazinol did not. Sleepiness was the most common side effect on morphine (n = 43), and nausea was most common on meptazinol (n = 35). The incidence of side effects appeared to be dose-related for both drugs.