Fertility: In animal studies, VALTREX did not affect fertility. However, high parenteral doses of aciclovir caused testicular effects in rats and dogs (see Pharmacology: Toxicology: Preclinical Safety Data under Actions).
No human fertility studies were performed with VALTREX, but no changes in sperm count, motility or morphology were reported in 20 patients after 6 months of daily treatment with 400 mg to 1 g aciclovir.
Pregnancy: There are limited data on the use of VALTREX in pregnancy. VALTREX should only be used in pregnancy if the potential benefits of treatment outweigh the potential risk.
Pregnancy registries have documented the pregnancy outcomes in women exposed to VALTREX or to any formulation of ZOVIRAX (aciclovir, the active metabolite of VALTREX); 111 and 1246 outcomes (29 and 756 exposed during the first trimester of pregnancy), respectively, were obtained from women prospectively registered. The findings of the aciclovir pregnancy registry have not shown an increase in the number of birth defects amongst aciclovir-exposed subjects compared with the general population, and any birth defects showed no uniqueness or consistent pattern to suggest a common cause. Given the small number of women enrolled into the valaciclovir pregnancy registry, reliable and definitive conclusions could not be reached regarding the safety of VALTREX in pregnancy (see Pharmacology: Pharmacokinetics under Actions).
Lactation: Aciclovir, the principle metabolite of VALTREX, is excreted in breast milk. Following oral administration of a 500 mg dose of VALTREX, peak aciclovir concentrations (Cmax) in breast milk ranged from 0.5 to 2.3 (median 1.4) times the corresponding maternal aciclovir serum concentrations. The aciclovir breast milk to maternal serum AUC ratios ranged from 1.4 to 2.6 (median 2.2). The median aciclovir concentration in breast milk was 2.24 μg/ml (9.95 μM). With a maternal VALTREX dosage of 500 mg twice daily, this level would expose a nursing infant to a daily oral aciclovir dosage of about 0.61 mg/kg/day. The elimination half-life of aciclovir from breast milk was similar to that for serum.
Unchanged valaciclovir was not detected in maternal serum, breast milk, or infant urine.
Caution is advised if VALTREX is to be administered to a nursing woman. However, ZOVIRAX is used to treat neonatal herpes simplex at intravenous doses of 30 mg/kg/day.