ISRADIPINE

Fetal Risk Summary

Isradipine is a calcium channel blocking agent used in the treatment of hypertension. The drug is not teratogenic in rats or rabbits at doses 150 and 25 times the maximum recommended human dose, respectively (1). Embryotoxicity was not observed in either species at doses that were not maternally toxic (1).

In a study to determine the effects of isradipine on maternal and fetal hemodynamics, 27 women with pregnancy-induced hypertension in the 3rd trimester were treated with the drug, 2.5 mg twice daily for 4 days then 5 mg twice daily (2). Hemodynamic measurements, conducted before and after 1 week of therapy, demonstrated a significant reduction in mean arterial pressure without a significant change in uteroplacental or fetal blood flows. The lack of change in uteroplacental blood flow suggested that there was uterine vasodilatation with decreased uterine vascular resistance (2). No fetal adverse effects were observed.

A study published in 1992 examined the effect of isradipine on three standardized physical stress tests in 14 women under treatment for hypertension (3 with essential hypertension, 11 with preeclampsia) (3). Treatment with isradipine, 5 mg once daily for 4 days then 5 mg twice daily, was begun at a mean 33 weeks' gestation with delivery occurring at a mean of 38 weeks. The pregnancy outcomes were normal except for 1 newborn whose birth weight was below the 10th percentile and transient hyperbilirubinemia in 2 neonates.

Breast Feeding Summary

No reports describing the use of isradipine during human lactation or measuring the amount, if any, excreted into milk have been located. The relatively low molecular weight (about 371), however, probably indicates that the drug is excreted in milk. The potential effects of this exposure on a nursing infant are unknown.

References

1. Product information. DynaCirc. Sandoz Pharmaceuticals, 1993.
2. Lunell N-O, Garoff L, Grunewald C, Nisell H, Nylund L, Sarby B, Thornstrom S. Isradipine, a new calcium antagonist: effects on maternal and fetal hemodynamics. J Cardiovasc Pharmacol 1991;18(Suppl 3):S37–S40.
3. Lunell N-O, Grunewald C, Nisell H. Effect of isradipine on responses to standardized physical stress tests in hypertension of pregnancy. J Cardiovasc Pharmacol 1992;19(Suppl 3):S99–S101.