Abstract: FR-PO236
Valacyclovir Neurotoxicity in a Patient on Peritoneal Dialysis
Session Information
- Pharmacology
November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Pharmacology (PharmacoKinetics‚ -Dynamics‚ -Genomics)
- 1900 Pharmacology (PharmacoKinetics‚ -Dynamics‚ -Genomics)
Authors
- Moody, Taylor R., University of Maryland Medical System, Baltimore, Maryland, United States
- Leonard, James B., University of Maryland Medical System, Baltimore, Maryland, United States
- Lam, Angela H., University of Maryland Medical System, Baltimore, Maryland, United States
- Husak, Nicholas, University of Maryland Medical System, Baltimore, Maryland, United States
- King, Joshua D., University of Maryland Medical System, Baltimore, Maryland, United States
Introduction
Valacyclovir is a prodrug of acyclovir often used to treat herpes zoster and herpes simplex. While acyclovir neurotoxicity is well-described in the literature, a recent systematic review identified only 35 cases of valacyclovir neurotoxicity (VAN) through 2021. Patients with advanced age and impaired kidney function are at highest risk of both acyclovir and valacyclovir neurotoxicity. In the absence of hemodialysis (HD), the half-life of valacyclovir in patients with ESKD can be up to 20 hours. Valacyclovir is removed well by HD, but continuous ambulatory peritoneal dialysis (PD) removes only approximately 10% of the drug.
Case Description
A 64-year-old man with ESKD on PD after a failed kidney transplant was prescribed valacyclovir 1000 mg three times daily for herpes zoster, exceeding the recommended dose of 500 mg daily. The evening of his first day of therapy, he began to experience confusion. The following day, he presented to a local hospital with hypertension, hypothermia, hallucinations, and disorientation. Serum laboratory tests and complete blood count were close to baseline; cerebrospinal fluid analysis was notable for mild leukocytosis at 11 WBC/uL. He was admitted to the ICU. The patient’s mental status did not improve, and he was persistently hypertensive requiring nicardipine infusion. On hospital day 3 he began receiving PD, but his mental status deteriorated. On hospital day 5 he was started on intermittent HD in combination with his usual PD with dwells every 4 hours. Approximately 4 days after the initiation of HD, mentation substantially improved. No other medical cause of his prolonged encephalopathy was identified, and his altered sensorium was attributed to VAN.
Discussion
Valacyclovir is a commonly used drug that is typically well-tolerated, safe, and efficacious; however, in ESKD it may cause substantial encephalopathy. Because this drug is largely renally excreted, patients with impaired kidney function, especially those with ESKD, are at increased risk of toxicity and require substantial dose reduction. Valacyclovir is dialyzable and may require HD to rapidly remove this drug, even in patients on maintenance PD. Delaying initiation of HD, as in this case, may prolong encephalopathy and increase the risk of adverse outcomes.