Abstract
Acyclovir is a drug that is mainly eliminated via the renal route so its pharmacokinetics are affected by renal function. In cases of renal failure, the dosage must thus be adjusted to avoid neurotoxicity. We report on two cases of neurotoxicity caused by valacyclovir, a prodrug of acyclovir, in patients with end-stage renal disease who were undergoing maintenance hemodialysis (HD). In both cases, neurotoxicity occurred even though the dose of valacyclovir had been reduced and the elimination half-lives were the same as those reported in other HD patients (about 20hours). Therefore, individual variation in elimination did not appear to be the cause of the neurotoxicity, but there was still the possibility that it was due to the dosage being too high. So for the hext patient, the dose of valacyclovir given after each HD treatment was further reduced to 500mg. This dosage was well tolerated and still effective against herpes zoster. It is therefore necessary to re-examine the administration of valacyclovir for patients undergoing HD from the standpoint of safety and our recommended dosage for the prevention of herpes zoster infection following HD is 500mg.
