May 22 2022

Classification of the active ingredient acyclovir


Risk level in pregnancy: This medicine is classified as Category B.

Registry data on consumption of acyclovir during pregnancy, ranging from 1984-1998, indicate that there is no increased risk of congenital anomalies (3.2% CI 2-5%) than in the whole population not exposed to acyclovir.

There is growing evidence about the use of systemic acyclovir is not associated with an increased prevalence of malformations at birth or preterm delivery.

Facts about the risk of low birth weight and spontaneous abortion are inconclusive, although the risk of miscarriage increases in women exposed to acyclovir during the first month of pregnancy. The use of topical acyclovir does not seem to be associated with any abortifacient or teratogenic effect.

Has been published a rare case of diastematomielia of an embryo exposed to acyclovir at the time of implantation. The case was diagnosed by ultrasonography during the pregnant controls and confirmed in the subsequent analysis to abortion.

There is a growing body of evidence about the use of systemic acyclovir is not associated with an increased prevalence of malformations at birth or preterm delivery.

Update 22.07.2009

Meaning of category B

Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women OR Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.