Linear pharmacokinetics of penciclovir following administration of single oral doses of famciclovir 125, 250, 500 and 750 mg to healthy volunteers

Twenty healthy male volunteers received single oral doses of famciclovir (125–750 mg), in a randomized, single-blind, crossover study. Plasma and urine concentrations of penciclovir and its 6-deoxy precursor, BRL 42359, were determined and penciclovir plasma concentration-time data submitted to model-independent pharmacokinetic analysis. Peak plasma concentrations of penciclovir were obtained at median times of 0.5–0.75 h after dosing. The areas under the concentration versus time curves (AUC) and the peak penciclovir concentration (Cmax) increased linearly with dose of famciclovir. Time to Cmax, elimination half-life, urinary recovery and renal clearance of penciclovir did not change with increasing dose. Famciclovir was excreted via the kidneys as penciclovir (60%) and BRL 42359 (5%), respectively. Famciclovir was well tolerated by all subjects with a low incidence of adverse effects. In conclusion, penciclovir thus displays linear pharmacokinetics in the anticipated therapeutic dose range of famciclovir.