Clinical pharmacokinetics of oral acyclovir in patients on continuous ambulatory peritoneal dialysis

It is increasingly recognised that dose adjustment of oral acyclovir in continuous ambulatory peritoneal dialysis (CAPD) patients is necessary to avoid neurotoxicity. A single 800-mg oral dose of acyclovir was administered to 10 uninfected anuric patients who were treated by CAPD. Serial blood and CAPD bag samples were analysed for acyclovir during the 31 h after dosing. Serum acyclovir levels were measured using radioimmunoassay and the pharmacokinetic parameters were estimated by linear regression using the STRIPE computer programme. Peak plasma levels of 8.95 +/- 3.95 microM were achieved at 4.1 +/- 1.85 h with the T1/2 calculated to be 14.52 +/- 3 h. The mean predicted serum acyclovir levels at steady state after 1,600-, 800- and 600-mg daily doses were 13.76, 6.88 and 5.16 microM, respectively. The present recommended daily doses of acyclovir (1,600 mg) for end-stage renal disease patients leads to supratherapeutic levels therefore increasing the risk and incidence of neurotoxicity. Computer modelling of various dosage simulations suggests that daily doses of 800 and 600 mg will achieve therapeutic levels (4-8 microM).