Metoprolol Pregnancy and Breastfeeding Warnings
Metoprolol Pregnancy Warnings
FDA pregnancy category: C Use of metoprolol is not recommended unless clearly needed. Women of childbearing potential should be encouraged to use adequate forms of contraception.
Animal studies have revealed decreased embryo and neonatal survival in rats at doses up to 22 times (on a mg/m2 basis) the daily dose of 200 mg in a 60 kg patient, although there was no evidence of impaired fertility or teratogenicity. There are no controlled data in human pregnancy. Metoprolol should only be given during pregnancy when benefit outweighs risk. Metoprolol readily crosses the placenta. The maternal to fetal serum metoprolol concentration ratio is approximately 1:1. No teratogenic effects have been reported in human pregnancy. In a large study, the incidence of perinatal mortality was 2% of 57 hypertensive women who were treated with metoprolol alone, compared to 8% of 97 patients who were treated with hydralazine alone. No signs or symptoms of beta-blockade were noted in the fetuses or neonates. A case of a pregnant woman successfully treated with metoprolol for pheochromocytoma has been reported. Again, no signs or symptoms of beta-blockade were noted in the newborn. It is recommended that newborns who are exposed in utero to metoprolol should be carefully monitored for signs and symptoms of beta-blockade (bradycardia or hypotension) for at least 48 hours after birth. Incidentally, the plasma clearance (CL/F) of metoprolol is increased during pregnancy, averaging 362 mL/min/kg, compared to 82 mL/min/kg in the same patients postpartum.
Metoprolol Breastfeeding Warnings
Data from three lactating women who each were taking metoprolol up to 100 mg orally twice a day show that the mean area under the concentration versus time curve (AUC) in milk to AUC maternal serum ratio was 3.6, indicating concentration of metoprolol in human milk. Assuming ingestion of 75 mL of milk per meal, the infant dose at the time of maximum maternal drug concentration would not exceed 0.05 mg, and would be considerably less at other times. The authors of this study recommended that, unless the nursing infant has impaired renal or hepatic function, breast-feeding need not be interrupted with ordinary doses of metoprolol. Nursing infants should be carefully observed for signs of beta-blockade, however.
Caution is recommended. Excreted into human milk: Yes Excreted into animal milk: Unknown The effects in the nursing infant are unknown.
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