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Am J Obstet Gynecol. 2002 Jan;186(1):100-2.

Acyclovir concentrations in human breast milk after valaciclovir administration.

Author information

1
Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas, 75390-9032, USA. Jeanne.Sheffield@UTSouthwestern.edu

Abstract

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 microg/mL at 1 hour vs 4.2 microg/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 microg/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.

PMID:
11810093
[Indexed for MEDLINE]

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