Intramuscular meptazinol analgesia after surgery: a study of the dose-response effect and a controlled comparison with pentazocine and pethidine.

In a single-blind study of a new hexahydroazepine analgesic, meptazinol, intramuscular (i.m.) doses of 50-100 mg produced effective, dose-related analgesia in 45 patients recovering from abdominal surgery. The analgesic effect was significant 30 minutes after injection, and was still present after 2 hours. There was a good correlation between pain relief assessed by the patient, by the physician and indirectly by pulmonary function tests. Neither the respiratory nor cardiovascular systems were depressed. There were no abnormal biochemical or haematological findings and the only side effects were nausea and vomiting in a few patients receiving multiple doses of the drug. In a subsequent double-blind investigation in which drugs were given i.m. to 75 abdominal and orthopaedic surgery patients, meptazinol 100 mg was found to be equianalgesic with pentazocine 60 mg and pethidine 100 mg. The duration of action of meptazinol was estimated to be 4 hr. Patients given meptazinol were less sedated than those given pentazocine or pethidine and tended to show a greater improvement in lung function tests. There was no evidence of patient preference for meptazinol or morphine which were administered for further pain relief in a single-blind manner.