Can I take metronidazole while pregnant or breastfeeding?

Pregnancy: Teratogenic Effects: Pregnancy Category B There are no adequate and well controlled studies of metronidazole in pregnant women. There are published data from case-control studies, cohort studies, and 2 meta-analyses that include more than 5000 pregnant women who used metronidazole during pregnancy. Many studies included first trimester exposures. One study showed an increased risk of cleft lip, with or without cleft palate, in infants exposed to metronidazole in-utero; however, these findings were not confirmed. In addition, more than ten randomized placebo-controlled clinical trials enrolled more than 5000 pregnant women to assess the use of antibiotic treatment (including metronidazole) for bacterial vaginosis on the incidence of preterm delivery. Most studies did not show an increased risk for congenital anomalies or other adverse fetal outcomes following metronidazole exposure during pregnancy. Three studies conducted to assess the risk of infant cancer following metronidazole exposure during pregnancy did not show an increased risk; however, the ability of these studies to detect such a signal was limited.

Prescribing label, section “Pregnancy” (opening excerpt): Metronidazole (oral), NuCare Pharmaceuticals, Inc. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.

With maternal intravenous and oral therapy, breastfed infants receive metronidazole in doses that are less than those used to treat infections in infants, although the active metabolite adds to the total infant exposure. Plasma levels of the drug and metabolite are measurable, but less than maternal plasma levels. Case reports of Candida infections and diarrhea have been reported, and a comparative trial suggested that oral and rectal colonization with Candida might be more common in infants exposed to metronidazole.

Because of the well demonstrated genotoxicity and mutagenicity in bacteria, carcinogenicity in animals, and possible mutagenicity in humans,[1,2] concern has been raised about exposure of healthy infants to metronidazole via breastmilk. The relevance of these findings have been questioned and no definitive study has yet been performed in humans.

Opinions vary among experts on the advisability of using metronidazole during longer-term therapy while breastfeeding, but some sources recommend discontinuing breastfeeding for 12 to 24 hours after a single dose of 2 grams, but not after lower dosages.[3] Other drugs are available for some conditions that metronidazole is used to treat. Topical or use of metronidazole during breastfeeding is acceptable.[4] The manufacturer of one vaginal product recommends not breastfeeding during treatment and for 2 days after the last dose.

“Summary of Use during Lactation”, LactMed record “Metronidazole” (LM440), quoted verbatim. Everything LactMed reports about Metronidazole while breastfeeding.

Nursing Mothers Metronidazole is present in human milk at concentrations similar to maternal serum levels, and infant serum levels can be close to or comparable to infant therapeutic levels. Because of the potential for tumorigenicity shown for metronidazole in mouse and rat studies, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. Alternatively, a nursing mother may choose to pump and discard human milk for the duration of metronidazole therapy, and for 24 hours after therapy ends and feed her infant stored human milk or formula.

Prescribing label, section “Nursing Mothers”: Metronidazole (oral), NuCare Pharmaceuticals, Inc. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.