Comparison of meptazinol and pethidine given i.v. on demand in the management of postoperative pain.

Meptazinol and pethidine were compared under double-blind conditions in 20 patients, using an on-demand analgesic system to provide pain relief after upper abdominal surgery. The degree of analgesia, subjectively assessed, was good with both meptazinol and pethidine; although meptazinol produced significantly more nausea than did pethidine (P less than 0.01), there was no statistically significant difference in the frequency of other side-effects. Over 24 h average consumption of meptazinol was 2.4 times that of pethidine, suggesting that, when given by i.v. injection, meptazinol is less potent that pethidine.