Effects of slow release misoprostol on uterine contractility in early pregnancy.

BACKGROUND The effect of a novel slow release form of misoprostol (SR misoprostol) on uterine activity during early pregnancy was investigated in a pilot study. METHODS Thirty women with a pregnancy between 8 and 12 weeks requesting surgical abortion were allocated to treatment according to computerized randomization. SR misoprostol (400 and 800 microg) was compared to 400 microg of conventional misoprostol, all given orally. Intrauterine pressure was recorded using a pressure transducer inserted extra-amniotically and connected to a computer 30 min before treatment until 4 h thereafter when suction curettage was performed. Uterine tonus (mmHg) and contractility in Montevideo Units (MU) were calculated. RESULTS An increase in uterine tonus occurred after a significantly shorter time interval and was significantly more pronounced following conventional misoprostol compared to SR misoprostol. Regular uterine contractions developed in only a few patients treated with 400 microg conventional misoprostol or 400 microg SR misoprostol. In contrast the increase in uterine contractility (MU) was significantly more pronounced following 800 microg SR misoprostol treatment and was still continuing at 4 h of recording. CONCLUSIONS SR misoprostol acts less on uterine tonus than orally administered conventional misoprostol but leads to development of regular uterine contractions.