Terbinafine and Breastfeeding
Terbinafine is not recommended during breastfeeding, as the FDA drug label explicitly states that "treatment with terbinafine is not recommended in nursing mothers" due to significant drug transfer into breast milk with a milk-to-plasma ratio of 7:1. 1
FDA Drug Label Guidance
The official FDA labeling provides clear direction on this issue:
- Terbinafine is present in breast milk after oral administration 1
- The milk-to-plasma ratio is 7:1, meaning terbinafine concentrates in breast milk at seven times the level found in maternal plasma 1
- The FDA explicitly states: "Treatment with terbinafine is not recommended in nursing mothers" 1
This is not listed as an absolute contraindication, but rather a strong recommendation against use.
Clinical Context and Risk-Benefit Assessment
The recommendation against terbinafine during breastfeeding must be understood in the context of the conditions it treats:
- Onychomycosis and most superficial dermatophyte infections are not life-threatening and pose no risk to maternal health if treatment is delayed 2
- Treatment can be safely postponed until after breastfeeding is completed without adverse consequences to the mother 2, 1
- The infant would receive substantial drug exposure given the 7:1 concentration ratio in breast milk 1
Alternative Management Strategies
For nursing mothers requiring antifungal therapy:
- Topical antifungal agents are preferred for localized superficial infections, as systemic absorption and transfer to breast milk is minimal 2, 3
- Delay systemic treatment until after breastfeeding is completed for non-urgent conditions like onychomycosis 2, 1
- If systemic therapy is absolutely necessary for extensive or severe infection, consider alternative agents with better lactation safety profiles, though specific alternatives are not well-defined in the available evidence 4
Important Clinical Caveats
While the general principle is that most medications appear in breast milk in small amounts and are compatible with breastfeeding 5, 6, 7, terbinafine is an exception due to its high milk-to-plasma concentration ratio 1. The 7:1 ratio means the nursing infant would receive a disproportionately high exposure relative to maternal plasma levels 1.
The AAP guidelines note that breastfeeding decisions should consider advantages to the newborn and benefits to the patient 4, but in this case, the FDA's explicit recommendation against use, combined with the non-urgent nature of most indications for terbinafine, strongly favors avoiding the medication during lactation 1, 2.