Antiherpetic Antiviral Drugs Not Linked to Birth Defects

Acyclovir, valacyclovir in early pregnancy do not up risk, but data on famciclovir limited

TUESDAY, Aug. 24 (HealthDay News) -- Exposure to the antiviral drugs acyclovir and valacyclovir during the first trimester of pregnancy is not associated with a higher risk of major birth defects, according to a study in the Aug. 25 issue of the Journal of the American Medical Association.

In a population-based historical cohort study, Björn Pasternak, M.D., and Anders Hviid, of the Statens Serum Institut in Copenhagen, Denmark, evaluated 837,795 live-born infants between Jan. 1, 1996, and Sept. 30, 2008, to assess the associations between exposure to acyclovir, valacyclovir, and famciclovir during the first trimester of pregnancy and risk of major birth defects.

There were 1,804 pregnancies exposed to acyclovir, valacyclovir, or famciclovir in the first trimester, and the investigators found that 40 infants (2.2 percent) were diagnosed with a major birth defect compared with 19,920 (2.4 percent) among those unexposed. Thirty-two of 1,561 infants (2.0 percent) with first-trimester exposure to acyclovir were diagnosed with a major birth defect, and seven of 229 infants (3.1 percent) with first-trimester exposure to valacyclovir were diagnosed with a major birth defect. The researchers found only 26 instances of famciclovir exposure, and one of these infants (3.8 percent) was diagnosed with a major birth defect.

"Acyclovir is the most extensively documented antiviral and should therefore be the drug of choice in early pregnancy, while data on valacyclovir and famciclovir are still insufficient," the authors write.

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