Are metronidazole (Flagyl) and fluconazole (Diflucan) safe to use while breastfeeding?

Metronidazole and Fluconazole Safety During Breastfeeding

Both metronidazole (Flagyl) and fluconazole (Diflucan) are safe to use while breastfeeding and do not require interruption of nursing. 1, 2

Fluconazole (Diflucan) - Fully Compatible

Fluconazole is the preferred azole antifungal for nursing mothers and breastfeeding can continue without any interruption at all doses. 2

Key Safety Evidence

• The American Academy of Pediatrics and the Infectious Diseases Society of America (IDSA) both classify fluconazole as compatible with breastfeeding 2
• Fluconazole is present in breast milk but at levels less than the neonatal dosage, and no problems have been observed in breastfed infants 2
• Even with high-dose maternal regimens (400-800 mg/day), the amount excreted in breast milk remains well below therapeutic infant doses 2

Important Distinction

• High-dose fluconazole during the first trimester of pregnancy is associated with congenital malformations, but this pregnancy concern does NOT apply to breastfeeding, where fluconazole is considered safe at all doses 2

Standard Dosing While Nursing

• Single 150 mg dose for vaginal candidiasis is safe during lactation 2
• For breast/nipple thrush: 100-200 mg daily for 7-14 days without interrupting breastfeeding 2
• For recurrent vaginal candidiasis: 150 mg every 72 hours for 3 doses 2

Metronidazole (Flagyl) - Possibly Safe with Precautions

Metronidazole can be used during lactation if there are no safer alternatives, with specific dosing considerations. 1

Dosing-Specific Recommendations

• Standard dosing (400 mg three times daily): Continue breastfeeding without interruption 1, 3

  • Infant plasma concentrations from this regimen (1.27-2.41 mcg/mL) caused no serious reactions in studied infants 3
  • No significant adverse effects attributable to maternal metronidazole therapy were observed 3

• Single high-dose therapy (2 g oral dose): Stop breastfeeding for 12-24 hours after the dose 1, 4

  • Peak milk concentrations occur at 2-4 hours and decline over 12-24 hours 4
  • This precaution greatly reduces infant exposure 4

Pharmacokinetic Profile

• Mean milk-to-plasma ratio is 0.9 for metronidazole 3
• Mean milk concentrations around peak are 15.5 mcg/mL with standard dosing 3

Common Pitfall to Avoid

• Do not unnecessarily withhold breastfeeding with standard multi-dose regimens (400 mg TID), as this dosing has been proven safe in clinical studies 3
• Only interrupt breastfeeding for 12-24 hours if using the single 2 g dose regimen 1, 4