Preliminary clinical and pharmacokinetic experiences in the newborn when meptazinol is compared with pethidine as an obstetric analgesic.

Preliminary results on the disposition of meptazinol in the neonate are reviewed. Meptazinol has a half-life of 3.4 hours compared with 22.7 hours for pethidine. In a randomised double blind trial of 100 patients the depressant effects in the newborn of meptazinol and pethidine were compared. There was no difference in the Apgar scores at 1 and 3 minutes. Weight loss and the incidence of neonatal jaundice were less when mothers received meptazinol although these differences did not reach statistical significance. However, the number of infants considered fit for discharge by the 6th day was significantly greater in the meptazinol groups. In 43 cases transcutaneous monitoring of arterial PO2 was carried out for 30 minutes following delivery. Although the mean PaO2 was similar for meptazinol and pethidine, significant variations in the PaO2 of 2.0 kPa or greater and significant neonatal activity as judged by episodes of crying and movement, were recorded in the meptazinol group. The results of the trial suggest that meptazinol may have less depressant effects on the newborn, and may be preferable to pethidine as an obstetric analgesic.