Is Acyclovir safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Acyclovir. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
The mother of a 4-month-old infant noticed no adverse effects in her breastfed infant while she was taking an acyclovir dosage of 800 mg orally 5 times daily.[ 7 ] A mother with necrotizing herpes simplex keratitis was treated with 3% acyclovir ointment to the affected eye as well as acyclovir 500 mg orally, both 5 times a day. She continued oral acyclovir for 1 year and breastfed during treatment. At the 3 months follow-up, the baby was clinically healthy.[ 9 ]
Effects on milk supply
Relevant published information was not found as of the revision date.
Levels in milk
Maternal Levels. A 4-month-postpartum woman was taking 200 mg of acyclovir orally 5 times daily every 4 hours while awake. After 4 days of therapy, milk samples were taken 9 hours after the previous dose and at 4 times after a 200 mg dose. The lowest milk level of 427 mcg/L occurred 30 minutes after the first dose. At 3.2 hours after the dose, the milk acyclovir level was 1.3 mg/L and apparently still increasing.[ 4 ] A woman who was 1 year postpartum was taking acyclovir 200 mg orally 5 times daily. Milk levels taken immediately before a dose during 5 days of therapy ranged from 0.78 to 1.07 mg/L. Acyclovir in milk samples taken after the last dose decreased with a half-life of 2.8 hours.[ 5 ] A woman who had taken oral acyclovir 400 mg 3 times daily for 3 days in the peripartum period had a breastmilk acyclovir level of 54 mcg/L at 5 days after her last dose of acyclovir.[ 6 ] A mother nursing her 7-month-old infant took acyclovir 800 mg orally 5 times a day. Three milk acyclovir levels on days 5 and 6 of therapy ranged from 4.2 to 5.8 mg/L, with the highest level 9.4 hours after the previous dose. The authors estimated that a fully breastfed infant would receive a daily dosage of 0.73 mg/kg of acyclovir at this maternal dosage or about 1% of the maternal weight-adjusted dosage.[ 7 ] A woman who was 6 weeks postpartum received intravenous acyclovir 300 mg (5 mg/kg) three times daily for 5 days. Milk samples were taken every 6 hours after the last dose. The peak level was 7.3 mg/L and the drug was detectable in milk for up to 88 hours after the last dose.[ 8 ] Using the level 6 hours after the last dose, a fully breastfed infant would receive a daily dosage of 1.1 mg/kg with this maternal dosage regimen. Infant Levels. A 4-month-old infant whose mother was taking 200 mg orally 5 times daily was breastfed just before a dose. The infant's urine collected over the next 2 hours contained a total of 27 mcg of acyclovir.[ 4 ]
Alternatives LactMed lists
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.