From the FDA Drug Label
Although there is no information on the presence of valacyclovir in human milk, its metabolite, acyclovir, is present in human milk following oral administration of valacyclovir. Based on published data, a 500-mg maternal dose of VALTREX twice daily would provide a breastfed child with an oral acyclovir dosage of approximately 0. 6 mg/kg/day. There is no data on the effects of valacyclovir or acyclovir on the breastfed child or on milk production.
The safety of Valacyclovir during breastfeeding is not established due to lack of direct information on its presence in human milk and effects on the breastfed child. However, its metabolite acyclovir is present in human milk, and the estimated oral acyclovir dosage in a breastfed child is approximately 0.6 mg/kg/day. Considering the limited data, a conservative clinical decision would be to exercise caution when using Valacyclovir in breastfeeding mothers, weighing the benefits of treatment against potential risks to the infant 1.
From the Research
Valacyclovir is considered safe to use during breastfeeding, with the benefits of treating the maternal infection typically outweighing any theoretical risks to the breastfed infant. The amount of medication that passes into breast milk is minimal, with infants receiving less than 1% of the maternal weight-adjusted dose 2. Standard dosing for valacyclovir varies by indication: for herpes simplex outbreaks, 1 gram twice daily for 7-10 days; for suppression therapy, 500-1000 mg once daily; and for herpes zoster, 1 gram three times daily for 7 days.
Key Points
- No special precautions or timing of breastfeeding relative to medication intake are necessary.
- The safety profile is supported by the fact that valacyclovir is converted to acyclovir in the body, which has been extensively studied in breastfeeding with no adverse effects reported in infants 3.
- Even premature infants have not shown any problems when their mothers took valcyclovir while breastfeeding.
- A study published in 2023 found that most drugs, including valacyclovir, are transferred from the mother's blood to the milk, but the breastfed infant usually ingests a small drug amount through human milk 2.
- Risk assessment should not only be based on the drug's potential risk for the breastfed infant but should always take into account the benefits associated with breastfeeding, the risks of untreated maternal disease, and the maternal willingness to breastfeed 2.