Can pregnant patients have Flagyl (metronidazole)?

From the Guidelines

Flagyl (metronidazole) can be used in pregnant patients when necessary, but it should be prescribed cautiously and only when the potential benefits outweigh the risks. For pregnant patients requiring Flagyl:

• Oral dosing: 250 mg orally three times a day for 7 days is a recommended regimen, as stated in the 1998 guidelines for treatment of sexually transmitted diseases 1
• Avoid use in the first trimester if possible
• Use the lowest effective dose for the shortest duration While Flagyl crosses the placenta, most studies have not shown an increased risk of birth defects, as noted in the guidelines for the treatment of sexually transmitted diseases 1. However, it's classified as FDA Pregnancy Category B, meaning animal studies haven't shown risk, but there aren't adequate well-controlled studies in pregnant women. Flagyl is primarily used to treat bacterial vaginosis, trichomoniasis, and other anaerobic infections during pregnancy. These conditions, if left untreated, can lead to complications such as preterm labor or low birth weight, which may outweigh the potential risks of the medication, as suggested by the studies on bacterial vaginosis and trichomoniasis 1. Always inform patients to avoid alcohol consumption while taking Flagyl and for at least 24 hours after completing treatment, as it can cause a disulfiram-like reaction. Key considerations for the use of Flagyl in pregnant patients include:
• The potential benefits of treatment should outweigh the risks
• The lowest effective dose should be used for the shortest duration
• Patients should be informed of the potential risks and benefits of treatment
• Alternative treatments, such as clindamycin, may be considered in some cases, as noted in the guidelines for the treatment of sexually transmitted diseases 1.

From the FDA Drug Label

Pregnancy Teratogenic Effects Pregnancy category B Metronidazole crosses the placental barrier and enters the fetal circulation rapidly. Reproduction studies have been performed in rats at doses up to five times the human dose and have revealed no evidence of impaired fertility or harm to the fetus due to metronidazole No fetotoxicity was observed when metronidazole was administered orally to pregnant mice at 20 mg/kg/day approximately one and a half times the most frequently recommended human dose (750 mg/day) based on mg/kg body weight; however in a single small study where the drug was administered intraperitoneally, some intrauterine deaths were observed The relationship of these findings to the drug is unknown. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, and because metronidazole is a carcinogen in rodents, this drug should be used during pregnancy only if clearly needed Use of metronidazole for trichomoniasis during pregnancy should be restricted to those in whom alternative treatment has been inadequate. Use of metronidazole for trichomoniasis in the first trimester of pregnancy should be carefully evaluated because metronidazole crosses the placental barrier and its effects on the human fetal organogenesis are not known

• Pregnancy category: Metronidazole is classified as Pregnancy category B.
• Use during pregnancy: Metronidazole should be used during pregnancy only if clearly needed.
• First trimester use: Use of metronidazole for trichomoniasis in the first trimester of pregnancy should be carefully evaluated.
• Alternative treatment: Use of metronidazole for trichomoniasis during pregnancy should be restricted to those in whom alternative treatment has been inadequate 2.
• Contraindication: Metronidazole tablets are contraindicated in patients with trichomoniasis during the first trimester of pregnancy 2.

From the Research

Use of Flagyl (Metronidazole) in Pregnant Patients

• Metronidazole is recommended for the treatment of trichomoniasis and bacterial vaginosis in pregnant women, as the benefits of treatment may outweigh the potential risks to the fetus 3, 4.
• The use of metronidazole in pregnancy has been associated with a reduced risk of preterm birth, particularly when used in combination with other antibiotics 5, 6.
• However, metronidazole has also been linked to a 70% increased risk of spontaneous abortion, although this risk should be interpreted cautiously due to potential confounding factors 5.
• The current guidelines advocate for the use of metronidazole for the treatment of bacterial vaginosis in pregnant women, and it is considered safe for use in pregnancy when used as directed 3, 7.

Safety and Efficacy of Metronidazole in Pregnancy

• Metronidazole has been found to be effective in preventing preterm births and does not predict birth defects or congenital abnormalities 5, 6.
• The use of metronidazole in pregnancy requires consideration of the potential effects on the fetus or newborn, as well as the nature of follow-up care 7.
• Additional information is needed when metronidazole is used in association with other agents, and the benefits and risks of treatment should be carefully weighed in each individual case 6.