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 (CKD). There are no well documented reports of valacyclovir or acyclovir toxicity providing pre- and post-dialysis concentrations of acyclovir in the blood, dialysate, and urine of acutely neurotoxic patients. We report an elderly woman with stage 5 CKD who developed neurotoxicity after being prescribed standard doses of valacyclovir and provide measurements of the amount of the drug eliminated through hemodialysis versus 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 hemodialysis session acyclovir plasma concentrations decreased from 8.8 mg/L to 3.2 mg/L (63.6%). Her body-burden of drug before the second session of hemodialysis was estimated as 131.9 mg. During the 2.5 hours 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 hours. Despite minimal urinary elimination her blood concentration fell from 8.8 mg/L to 0.88 mg/L with 4.5 hours of hemodialysis. Hemodialysis appears to be an effective method of eliminating acyclovir, especially in patients with advanced kidney disease.