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Valacyclovir Pregnancy and Breastfeeding Warnings

Valacyclovir is also known as: Valtrex

Valacyclovir Pregnancy Warnings

Valacyclovir has been assigned to pregnancy category B by the FDA. High-dose animal studies have failed to reveal evidence of teratogenicity. No significant neonatal toxicity or fetal drug accumulation was noted in a small pharmacokinetic study (n=20) of valacyclovir (500 mg twice daily) administered beginning at 36 weeks' gestation. Records from the Acyclovir in Pregnancy Registry regarding the outcomes of live births in 380 women exposed to systemic acyclovir during the first trimester of pregnancy demonstrated no significant increase in the frequency of birth defects over that of the general population. However, the small size of the registry precludes any definitive conclusions to be made regarding the safety of acyclovir or valacyclovir use during pregnancy. Valacyclovir should only be given during pregnancy when the need has been clearly established.

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Valacyclovir Breastfeeding Warnings

The U.S. Public Health Service Centers for Disease Control and Prevention advise HIV-infected women not to breast-feed to avoid postnatal transmission of HIV to a child who may not yet be infected.

Acyclovir is excreted into breast milk after valacyclovir administration. A pharmacokinetic study (n=5) revealed that after a 500 mg dose of valacyclovir, the peak acyclovir breast milk concentrations (Cmax) were 0.5 to 2.3 times the maternal serum Cmax. The breast milk area under the concentration-time curve (AUC) for acyclovir was 1.4 to 2.2 times the maternal serum AUC. Therefore, a 500 mg maternal dose of valacyclovir would result in a 0.6 mg/kg/day dosage of acyclovir to the nursing infant (approximately 2% of a standard neonatal IV dose). No unchanged valacyclovir was detected in infant urine or maternal breast milk or serum. The manufacturer recommends that valacyclovir be administered to breast-feeding women with caution and only when clearly needed. However, HIV-infected mothers should not breast-feed their infants due to the risk of transmission of HIV via breast milk.

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References for pregnancy information

  1. Kimberlin DF, Weller S, Whitley R, Andrews WW, Hauth JC, Lakeman F, Miller G "Pharmacokinetics of oral valacyclovir and acyclovir in late pregnancy." Am J Obstet Gynecol 179 (1998): 846-51
  2. "Product Information. Valtrex (valacyclovir)." Glaxo Wellcome, Research Triangle Park, NC.

References for breastfeeding information

  1. "Infant feeding and transmission of human immunodeficiency virus in the United States." Pediatrics 131 (2013): 391-6
  2. Panel on Treatment of HIV-Infected Pregnant Women and Prevention of Perinatal Transmission. National Institute of Health "Recommendations for use of antiretroviral drugs in pregnant HIV-1-infected women for maternal health and interventions to reduce perinatal HIV transmission in the United States. Available from: URL:" ([2011 Sep 14]):
  3. "Product Information. Valtrex (valacyclovir)." Glaxo Wellcome, Research Triangle Park, NC.

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