The pharmacokinetic disposition of acyclovir was studied in six patients with chronic renal failure (CRF) and anuria. At the end of a one-hour intravenous infusion (2.5 mg/kg), the mean peak acyclovir plasma level (±SD), determined by radioimmunoassay, was 37.5 ± 24.2 μM (8.4 ± 5.4 μg/ml), twice the level found at this dose in patients with normal renal function (NRF). In the CRF volunteers, significant plasma levels (3.0 ± 1.4 μM) persisted at 47 hours after drug administration (before hemodialysis) whereas in the NRF patients levels dropped to less than 1 μM by 11 hours. Hemodialysis was started 47 hours after infusion and was continued for six hours. The pre-dialysis plasma drug level was reduced by 61.5 percent at 0.25 to 1.5 hours after the end of dialysis. The mean plasma t 1 2 during dialysis of 5.4 hours, the extraction ratio of 0.44, and the dialysis clearance for plasma of 113 ml/min indicate that acyclovir is efficiently removed by hemodialysis. One-half the suggested intravenous dose for a particular indication can be given every 24 hours and a similar replacement dose should be given after each dialysis.
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