The effect of disopyramide on uterine contractions during pregnancy

To evaluate the effect of disopyramide on uterine contractions during pregnancy, the drug was given for 48 hours to 10 women with indications for labor induction. Placebo was given to 10 other women with the same indications for induction. During the study period, regular uterine contractions occurred in 10 women in the study group, as compared with none in the control group ( p < 0.0001). Eight women in the study group were delivered of infants within 48 hours, as compared with none in the control group ( p < 0.0001). The mean time until the appearance of regular uterine contractions in the study group (4.15 ± 1.76 hours) was significantly shorter ( p < 0.001) than that in the control group (56.13 ± 5.28 hours). Patients who were not delivered of infants within 48 hours received other medications (prostaglandin E 2, oxytocin). The mean maternal blood level of disopyramide at the time of appearance of uterine contractions was 1.52 ± 0.9 mg/ml. The mean maternal level at delivery was 0.93 ± 0.43 mg/ml and the cord blood level at the time of delivery was 0.33 mg/ml (cord blood/maternal level ratio = 0.36, r = 0.73, p < 0.05). These results indicate that disopyramide should not be used in pregnancy for antiarrhythmic purposes because it may induce uterine contractions and delivery.