Use in pregnancy: A post-marketing aciclovir pregnancy registry has documented pregnancy outcomes in women exposed to any formulation of Zovirax. The birth defects described amongst Zovirax exposed subjects have not shown any uniqueness or consistent pattern to suggest a common cause.
The use of aciclovir should be considered only when the potential benefits outweigh the possibility of unknown risks.
Use in lactation: Following oral administration of aciclovir 200 mg 5 times a day, aciclovir has been detected in breast milk at concentrations ranging from 0.6-4.1 times the corresponding plasma levels. These levels would potentially expose nursing infants to aciclovir dosages of up to 0.3 mg/kg/day. Caution is therefore advised if Zovirax is to be administered to a nursing woman.