Meptazinol in the treatment of severe post-operative pain: a comparison with morphine.

The efficacy of meptazinol (100 mg) was compared to morphine (15 mg) in the relief of post-operative orthopaedic pain. In a randomised double blind study, 35 patients received meptazinol and 28 morphine. The onset of maximum analgesia was quicker with meptazinol. The mean intervals between first and second intramuscular doses were 2.4 hours and 2.7 hours for meptazinol and morphine respectively. Four patients were withdrawn from the study after receiving meptazinol because analgesia was inadequate and morphine scored better than meptazinol in an assessment of overall quality of treatment. The effects on the cardiovascular system were similar for both drugs but meptazinol caused significantly less elevation of arterial PCO2 than morphine.