Neurotoxicity from inordinate valacyclovir dosage in an elderly woman with stage 5 chronic kidney disease

Unadjusted doses of valacyclovir can cause neurotoxicity in patients with chronic kidney disease. There are no well documented reports of valacyclovir or acyclovir toxicity providing pre- and postdialysis concentrations of acyclovir in the blood, dialysate and urine of acutely neurotoxic patients. We report an elderly woman with stage 5 chronic kidney disease who developed neurotoxicity after being prescribed unadjusted doses of valacyclovir and provide measurements of the amount of the drug eliminated through haemodialysis vs. native renal clearance. The patient's estimated body-burden of drug before the first session of dialysis was estimated at 580.3 mg. During the first haemodialysis session acyclovir plasma concentrations decreased from 8.8 to 3.2 mg/L (63.6%). Her body-burden of drug before the second session of haemodialysis was estimated as 131.9 mg. During the 2.5 h of the second dialysis session a total of 66.6 mg was eliminated based on measured dialysate concentrations. Urinary elimination was 17.7 mg over 30 h. Despite minimal urinary elimination her blood concentration fell from 8.8 to 0.88 mg/L with a total of 4.5 h of haemodialysis. Haemodialysis appears to be an effective method of eliminating acyclovir, especially in patients with advanced kidney disease.