Research conducted by the Pediatric Trials Network (PTN) has led the U.S. Food and Drug Administration (FDA) to update the prescribing information, or drug label, of acyclovir to include dosing for infants with Neonatal Herpes Simplex Virus (HSV) based upon the infants post-menstrual age. Acyclovir (brand name Zovirax) is an antiviral drug used in the pediatric population to treat HSV, a highly contagious virus that can be very serious for babies.

Because an infant’s immune system is not fully developed to fight off the virus, the disease can result in death or mental disabilities. While appropriate dosing of acyclovir was known for adults and children, acyclovir had not been adequately studied in full-term or preterm infants.

In the two associated PTN studies, 32 infants were enrolled. The first study was conducted at a single medical center in preterm and term infants with suspected HSV infection. The second study involved multiple medical centers and enrolled only preterm infants with suspected HSV infection.

Based upon the pharmacokinetic (how a drug travels through the body) results, the FDA updated the label to include dosing in infants based on their post-menstrual age (PMA), or the time that had elapsed since the mother’s last menstrual cycle. PMA is especially useful in preterm infants because it characterizes the baby’s expected developmental age.