Abstract
The effects of a new calcium antagonist, isradipine (PN 200–110) on postpartum uterine activity and the maternal cardiovascular system were investigated. Uterine activity was recorded by a microtip transducer catheter inserted transcer-vically within 45 min of normal vaginal delivery. 0.5 mg of isradipine was given as a bolus injection during 5 min to 7 women with spontaneous uterine activity and 1 mg was given during a 15-min period to another 8 women with oxytocin-stimulated uterine activity. Matched controls with similar pre-injection activity (±5%) but not given the drug were selected for comparison. The effects of the drug in 3 women (given 1 mg of isradipine) were compared with those in matched controls and in women given 0.25 mg of terbutalin i.v. as a bolus injection. lsradipine had a marked inhibitory effect on both spontaneous and oxytocin-stimulated uterine activity. The inhibitory effect of 1 mg of isradipine seemed comparable to that of 0.25 mg of terbutalin. The inhibition occurred within 1–2 min after the injection and was sustained throughout the study period (2 h). A transient reduction of the systolic (mean maximum decrease 10–15%) and diastolic blood pressure (mean maximum decrease 15–2096) was seen, particularly during the injection period. Hypotension (systolic blood pressure < 80 mmHg) was not recorded. A moderate increase in pulse rate (mean maximum increase 22–27%) was seen in all cases. The results show that isradipine given as a bolus injection can inhibit early postpartum uterine activity, with minimal side effects.