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Acyclovir concentrations in human breast milk after valaciclovir administration
Jeanne S Sheffield1, Douglas N Fish, Lisa M Hollier
1Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas, 75390-9032, USA. Jeanne.Sheffield@UTSouthwestern.edu
American Journal of Obstetrics and Gynecology
|January 26, 2002
Summary
Valaciclovir rapidly converts to acyclovir, which concentrates in breast milk. However, the acyclovir levels in breast milk are significantly lower than neonatal therapeutic doses.
Area of Science:
- Pharmacology
- Neonatal Medicine
- Lactation Studies
Background:
- Valaciclovir is an antiviral medication.
- Breastfeeding mothers may require antiviral treatment.
- Understanding drug transfer into breast milk is crucial for infant safety.
Purpose of the Study:
- To characterize the pharmacokinetics of valaciclovir and its active metabolite, acyclovir.
- To quantify acyclovir levels in breast milk and maternal serum.
- To assess potential infant exposure to acyclovir via breast milk.
Main Methods:
- Five breastfeeding mothers received 500 mg of valaciclovir twice daily for 7 days postpartum.
- Serum and breast milk samples were collected at specified intervals.
- Infant urine samples were collected to assess acyclovir excretion.
Main Results:
- Valaciclovir was rapidly converted to acyclovir.
- Peak breast milk acyclovir concentrations were observed 4 hours after dosing.
- The ratio of breast milk to serum acyclovir concentration reached a steady state of 1.85.
Conclusions:
- Valaciclovir is efficiently converted to acyclovir, which is present in breast milk.
- Acyclovir concentrations in breast milk are substantially lower than therapeutic neonatal doses.
- This suggests a low risk of systemic exposure for breastfeeding infants.