Metronidazole Pregnancy and Breastfeeding Warnings
Metronidazole Pregnancy Warnings
Animal studies have failed to reveal evidence of fetal harm, except when the drug was administered intraperitoneally. There are no controlled data in human pregnancy. Metronidazole crosses the placental barrier; effects on human fetal organogenesis are not known. Published data from case-control studies, cohort studies, and 2 meta-analyses included more than 5000 pregnant women who used metronidazole during pregnancy. Many studies included first trimester exposures. In 1 study, an increased risk of cleft lip (with or without cleft palate) was seen in infants exposed to metronidazole in utero; however, findings were not confirmed. More than 10 randomized placebo-controlled clinical studies enrolled more than 5000 pregnant women to assess use of antibiotics (including metronidazole) for bacterial vaginosis on rate of preterm delivery. Most studies did not show increased risk for congenital anomalies or other adverse fetal outcomes after metronidazole exposure during pregnancy. Increased risk of infant cancer after metronidazole exposure during pregnancy was not found in 3 studies conducted to assess this risk; however, limited ability to detect such a signal. The CDC recommends use of metronidazole for vaginal trichomoniasis during any stage of pregnancy. Multiple studies and meta-analyses have not established an association between metronidazole use during pregnancy and teratogenic or mutagenic effects in infants. FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.
FDA pregnancy category: B Use of metronidazole for trichomoniasis is contraindicated during the first trimester; the manufacturer makes no further recommendations regarding use during pregnancy.
Metronidazole Breastfeeding Warnings
Metronidazole is present in human milk at levels similar to maternal serum levels, and infant serum levels can be similar to infant therapeutic levels. Due to the potential for tumorigenicity shown for metronidazole in mouse and rat studies, discontinuation of the drug or nursing is recommended. Alternatively, nursing mothers may pump and discard their milk during and for 24 hours after metronidazole therapy and feed their infants stored human milk or formula.
A decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother. Excreted into human milk: Yes Excreted into animal milk: Data not available
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