Nimodipine Pregnancy and Breastfeeding Warnings
Nimodipine Pregnancy Warnings
Some experts warn of the theoretical possibility of decreased placental perfusion pressure during nimodipine therapy. In addition, some warn of the possibility of maternal heart block when nimodipine and magnesium sulfate are given together. Use of nimodipine to treat preeclampsia has been reported in small studies. In one study, nimodipine 30 mg was given every 4 hours from admission to 24 hours after delivery to 10 consecutive women with preeclampsia. Use of this drug was associated with significant reductions in the average maternal systolic and diastolic blood pressures, fetal middle cerebral artery pulsatility index, and the umbilical artery systolic/diastolic ratio. Passage across the human placenta was documented. The median maternal serum and umbilical cord nimodipine concentrations at delivery were 7.32 and 2.60 ng/mL, respectively, yielding a ratio of 2.4:1. The average APGAR scores for 9 of the neonates at 1 and 5 minutes were 8 and 9, respectively (one of the patients had a ruptured uterus complicated by severe fetal distress). There was no evidence of birth defects from any of the 10 deliveries. In another small study, four unselected pregnant women with hypertension, proteinuria, and seizures were given intravenous nimodipine during right heart catheterization with pulmonary artery pressure measurements. Significant reductions in systemic vascular resistance and mean arterial pressure were well-documented. There were no adverse effects on the mothers or fetuses and no significant changes in oxygen delivery or peripheral oxygen consumption during the study. A retrospective review of 78 women with first-trimester exposure to calcium channel blockers (CCBs) (11% or 9 were taking nimodipine) revealed no increase in major malformations compared with a control group matched for maternal age and smoking. This review suggests that CCBs do not represent a major teratogenic risk.
Nimodipine has been assigned to pregnancy category C by the FDA. Animal studies have revealed evidence of teratogenicity, including malformations, stunted growth, and stillbirths. There are no controlled data in human pregnancy. Nimodipine should only be given in pregnancy when benefit outweighs risk to the fetus.
Nimodipine Breastfeeding Warnings
Nimodipine is excreted into human milk in small amounts. The short or long-term effects of the relatively small concentrations of nimodipine detected in human milk on nursing infants are not known. The manufacturer recommends that due to the potential for serious adverse reactions in nursing infants, a decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Data from two cases indicate the amount of drug a suckling infant would be exposed to if the nursing mother were receiving 60 mg orally four times a day or 1 mg/hr would be very small to negligible. A woman who had recently and uneventfully delivered a normal 38 week 2600 gram baby girl developed symptomatic vasospasm after aneurysm surgery. She was given nimodipine 60 mg orally every 4 hours for 10 days. Breast milk was expressed manually and the baby was fed infant formula. One week after beginning nimodipine therapy, the average maternal plasma to breast milk nimodipine concentration ratio was approximately 3, with plasma and breast milk levels widely fluctuating from 2 to 16 mcg/L and 0.5 to 4 mcg/L, respectively. Given that five half-lives are required for a drug to reach its steady state, the authors advised that breast-feeding be withheld for at least 45 hours following cessation of oral nimodipine therapy. A 36-year-old woman received nimodipine 1 mg/hr for cerebral vasospasm 3 weeks postpartum. The serum and milk nimodipine concentrations 0.5, 7.5, and 13.5 hours after a 24-hour infusion were 3.54 and 0.42, 21.69 and 1.26, and 10.84 and 1.61 ng/mL, respectively (ratios of 8.4:1, 17.2:1, and 6.7:1, respectively). Assuming a daily suckling milk intake of 150 mL/kg, the authors estimated that a nursing infant would receive between 0.063 and 0.705 mcg/kg/day of nimodipine, or between 0.008% and 0.092% of the weight-adjusted dose to the mother. The authors concluded that nimodipine is transferred to human milk in a lower proportion than other calcium channel blockers, and that the risk for the nursing infant is theoretically negligible at the maternal doses given.
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