Maternal blood pressure response to the intravenous administration of pethidine-promethazine during labor.

A double blind study on the effect of an intravenous injection of a combination of 75 mg pethidine and 25 mg promethazine was conducted on 200 women during normal deliveries. Four groups of 50 women each received injections of pethidine and promethazine, promethazine alone, pethidine alone and normal saline. In the pethidine-promethazine group there was a significant elevation in blood pressure in the first 10 min following the injection as compared with the other groups. The mean (+/- S.D.) systolic blood pressure after the injection was 143.2 +/- 14.3 mmHg as compared with 118.9 +/- 8.4 mmHg before the injection, and the mean diastolic blood pressure as 96.9 +/- 8.4 mmHg after the injection as compared with 77.7 +/- 9.3 mmHg before the injection. 25 mg promethazine alone caused slight elevation in blood pressure which was further increased by combination with pethidine. The clinical significance of these observations is discussed.