Pharmacokinetics of vidarabine in the treatment of infants and children with infections due to herpesviruses.

The pharmacokinetics of vidarabine were studied on 22 occasions in nine infants and three older children with herpesvirus infection. The drug was administered for 10 days in doses of 15-30 mg/kg per day. Vidarabine was not detected in the serum of any patient, although small quantities were detected in the urine of two of the older children. Peak serum concentrations of arabinosyl hypoxanthine, the major metabolite of vidarabine, ranged from 2.3 to 11.4 micrograms/ml. Concentrations of this metabolite were higher in two preterm infants than in full-term infants receiving comparable doses. The mean elimination half-life estimated from cumulative urinary excretion was 2.4 hr in a preterm infant, 3.1 hr in full-term infants, and 2.8 hr in older children. Neither clearance nor half-life changed when multiple doses were administered. Vidarabine and arabinosyl hypoxanthine did not accumulate during therapy. The rates of recovery of drug from the urine and of renal clearance of arabinosyl hypoxanthine were directly related to the age and maturity of the patient. Arabinosyl hypoxanthine readily diffused into cerebrospinal fluid.