An Investigation of the Steady‐State Pharmacokinetics of Oral Valacyclovir in Immunocompromised Children

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Abstract
Valacyclovir was administered to 28 immunocompromised children (ages 5–12 years) to obtain preliminary pharmacokinetic and safety information. Patients were randomized to valacyclovir regimens of 250 mg (9.4–13.3 mg/kg) or 500 mg (13.9–27.0 mg/kg) twice daily or 500 mg (13.2–21.7 mg/kg) 3 times a day. Acyclovir pharmacokinetics were evaluated at steady state. Valacyclovir was rapidly absorbed and converted to acyclovir. Mean (±SD) acyclovir peak concentrations from 250 mg and 500 mg valacyclovir were 4.11±1.41 and 5.19±1.96 μg/mL, respectively. Corresponding single dose area-under-curve values were 12.14±6.60 and 14.49±4.69h×μg/mL. By using historical data for intravenous acyclovir as reference, the overall estimate of acyclovir bioavailability from valacyclovir was 48%, 2- to 4-fold greater than for oral acyclovir. In general, adverse events were not attributable to valacyclovir and were consistent with disease-related expectations and concomitant therapies. Dosage options for using valacyclovir in children are discussed