Acyclovir concentrations in human breast milk after valaciclovir administration

Jeanne S. Sheffield, Douglas N. Fish, Lisa M. Hollier, Sabrina Cadematori, Brenda J. Nobles, George D. Wendel

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


OBJECTIVE: The purpose of this study was to determine the valaciclovir and acyclovir pharmacokinetic profiles in serum and breast milk after valaciclovir administration to women after delivery. STUDY DESIGN: Valaciclovir (500 mg twice daily for 7 days) was given to 5 women after delivery who were breast-feeding healthy term infants. Matched serum and breast milk samples were obtained after the initial dose, on day 5 and 24 hours after the drug was discontinued. Infant urine was obtained on day 5. RESULTS: Valaciclovir was rapidly converted to acyclovir. The peak serum acyclovir concentration occurred 3 hours before the peak breast milk concentration (2.7 μg/mL at 1 hour vs 4.2 μg/mL at 4 hours). The serum acyclovir elimination half-life was 2.3 hours. The ratio of breast milk to serum acyclovir concentration was highest 4 hours after the initial dose at 3.4 and reached steady state ratio at 1.85. The median infant urine acyclovir concentration at steady state was 0.74 μg/mL. CONCLUSION: Valaciclovir is rapidly converted to acyclovir and concentrates in breast milk. However, the amount of acyclovir in breast milk after valaciclovir administration is considerably less (2%) than that used in therapeutic dosing of neonates.

Original languageEnglish (US)
Pages (from-to)100-102
Number of pages3
JournalAmerican journal of obstetrics and gynecology
Issue number1
StatePublished - 2002
Externally publishedYes


  • Acyclovir
  • Breast milk
  • Herpes simplex virus
  • Valaciclovir

ASJC Scopus subject areas

  • Obstetrics and Gynecology


Dive into the research topics of 'Acyclovir concentrations in human breast milk after valaciclovir administration'. Together they form a unique fingerprint.

Cite this