Acyclovir is used to treat herpes simplex virus infections. The standard dose is 20 mg/kg every 8 hours intravenously for 14-21 days depending on the type of infection. It can also be used to prevent chickenpox in newborns after delivery at a dose of 10 mg/kg every 8 hours intravenously until tests confirm absence of the virus. Common side effects include neutropenia, phlebitis, and renal dysfunction. The infusion rate may need to be slowed and hydration improved to manage side effects.