Verapamil Pregnancy and Breastfeeding Warnings
Verapamil Pregnancy Warnings
Verapamil has been assigned to pregnancy category C by the FDA. Animal studies have failed to reveal evidence of teratogenicity; however, there was evidence of embryolethality and fetotoxicity at doses which produced maternal toxicity. There are no controlled data in human pregnancy. Verapamil should only be given during pregnancy when benefit outweighs risk.
Although verapamil is known to cross the human placenta, there are no reports linking verapamil with congenital defects in human pregnancy. Verapamil has been used safely to treat maternal hypertension and both maternal and fetal tachyarrhythmias. One case in which both digoxin and verapamil were successfully used to treat fetal supraventricular tachycardia at 32 weeks gestation is reported. Four weeks after the initiation of therapy, the fetus died, presumably due to complete heart block. Autopsy results are unavailable. Other than the association of fetal abnormality in this case, no adverse fetal or neonatal effects attributable to verapamil are reported. Because of the potential of reduced uterine blood flow associated with verapamil-induced hypotension, it is recommended that intravenous verapamil be used cautiously during pregnancy if it must be used. Data from the Michigan Medicaid Birth Defects Study failed to reveal an association between verapamil and congenital abnormalities (written communication, Franz Rosa, MD, Food and Drug Administration, 1994). This was a retrospective study of 229,101 completed pregnancies between 1985 and 1992, of which 76 were exposed to verapamil at some time during the first trimester and 172 were exposed to the drug at any time during pregnancy. Of these pregnancies, one cardiovascular defect was observed. This observation did not achieve statistical significance. These data do not support an association between verapamil and birth defects. A retrospective review of 78 women with first-trimester exposure to calcium channel blockers (CCBs) (41%, or 32 were taking verapamil) 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.
Verapamil Breastfeeding Warnings
Two case studies have shown that between 23% and 60% of the maternal serum verapamil concentration may be found in human milk at steady state. In case studies where verapamil concentration in human milk was calculated, the nursing infant doses ranged from less than 0.01% to 0.1% of the mother's dose. Possible infant exposure should be considered when verapamil is administered to a nursing woman.
Verapamil is excreted into human milk. Side effects in the nursing infant are unlikely. However, 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.
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