Acyclovir Safety During Breastfeeding
Acyclovir is safe to use during breastfeeding as it passes into breast milk in clinically insignificant amounts and poses minimal risk to nursing infants. 1, 2
Evidence on Acyclovir in Breast Milk
- Acyclovir concentrations in breast milk range from 4.16 to 5.81 micrograms/mL, which represents approximately 1% of the maternal dose in mg/kg/day 1
- The FDA drug label notes that acyclovir concentrations in breast milk range from 0.6 to 4.1 times corresponding plasma levels, potentially exposing nursing infants to a dose of up to 0.3 mg/kg/day 2
- Despite measurable levels in breast milk, these amounts are subtherapeutic for infants and have not been associated with adverse effects 1, 3
Clinical Recommendations for Breastfeeding Mothers
- Acyclovir should be administered to a nursing mother with caution and only when indicated, according to FDA labeling 2
- For mothers requiring treatment for herpes infections, continuing breastfeeding while taking acyclovir is considered safe 1
- Mothers with active herpes lesions on or near the breast should avoid direct contact between lesions and the infant but can continue breastfeeding from the unaffected breast 4
Special Considerations
- Acyclovir is the antiviral drug with the most reported experience in pregnancy and appears to be safe, making it the first choice for therapy of HSV infections in pregnancy and, by extension, during breastfeeding 4
- The CDC guidelines for prevention and treatment of opportunistic infections in HIV-infected adults specifically mention acyclovir as the preferred agent during pregnancy, which supports its safety profile for lactating women as well 4
- When treating immunocompromised patients, including breastfeeding mothers with compromised immunity, higher dosages of acyclovir may be needed, but this does not contraindicate breastfeeding 4
Monitoring Recommendations
- No specific monitoring of the breastfed infant is required when the mother is taking acyclovir 1
- Mothers should be advised to watch for potential side effects in the infant such as diarrhea or changes in feeding patterns, although these are rarely reported 3
- If the mother has severe herpes infection requiring high-dose intravenous therapy, temporary interruption of breastfeeding might be considered, but this is rarely necessary 4
Common Pitfalls to Avoid
- Do not confuse the safety profile of acyclovir during breastfeeding with its use during pregnancy (both are generally considered safe, but the considerations are different) 4, 2
- Do not unnecessarily discontinue breastfeeding when acyclovir treatment is indicated for the mother 1
- Do not assume that higher maternal doses will necessarily lead to clinically significant infant exposure, as studies show that even with high maternal doses (800 mg five times daily), infant exposure remains minimal 1