Postpartum intrauterine pressure studies of the uterotonic effect of oral misoprostol and intramuscular syntometrine

Objectives To investigate the effect of oral misoprostol in dosages varying from 200 mug to 800 mug on post partum uterine contractility and to establ ish their side effects. Design A prospective descriptive study. Participants Fifty-seven women who delivered vaginally after spontaneous la bours not requiring augmentation. Methods Within 5 minutes of delivery of the placenta, a calibrated Gaeltec catheter with an intrauterine pressure transducer at its tip was inserted t ranscervically into the uterine cavity. Cumulative uterine activity was rec orded for 30 minutes in each woman before administering the oral misoprosto l tablets and continued for a further 90 minutes after its administration. Thus each woman acted as her own control regarding changes in uterine contr actility. Uterine activity was recorded on a Sonicaid Meridian fetal monito r, which measures active contraction area automatically. The incidence of s ide effects was also recorded. Results There was no statistical difference (P = 9.837) in the adjusted mea n difference in cumulative uterine activity following all the doses of oral misoprostol, compared with intramuscular syntometrine, the largest differe nce being seen in oral misoprostol 200 mug (adjusted mean difference -2282 kPas s, 95% CI -7954 to 3390 kPas s). The mean onset of action of oral miso prostol (6.1, SD 2.1 min) was significantly slower than that of intramuscul ar syntometrine (3.2, SD 1.5 min; P = 0.002), but their durations of action were similar (P = 0.637). In the misoprostol group the commonest side effe cts were shivering (36%) and a rise in body temperature above 38 degreesC ( 40%). In the syntometrine group, the most commonly observed side effect was moderate uterine pain (nine out of ten women) and a rise in diastolic bloo d pressure of 20 mmHg (two out of ten women). Conclusion The results of this study show that oral misoprostol has a defin ite uterotonic effect on the postpartum uterus. At doses of 200 mug to 100 mug, oral misoprostol has a similar uterotonic effect to intramuscular synt ometrine. Higher doses of oral misoprostol are associated with significantl y more side effects.