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Abstract: PO1320

Acyclovir for Herpes Zoster Encephalitis: Panacea or Problem?

Session Information

Category: Trainee Case Report

  • 703 Dialysis: Peritoneal Dialysis


  • Ghaffar, Adil, University of Wisconsin System, Madison, Wisconsin, United States
  • Maursetter, Laura J., University of Wisconsin System, Madison, Wisconsin, United States
  • Garg, Neetika, University of Wisconsin System, Madison, Wisconsin, United States

Herpes zoster, which is the reactivation of varicella-zoster virus (VZV), is more common in immunocompromised patients, with a higher incidence of encephalitis. The treatment of choice is intravenous acyclovir, with one of its adverse effects being neurotoxicity. We present a case where the disease effects and the medication side effects were difficult to distinguish.

Case Description

A 59-year-old man with ESKD and a history of failed allograft on peritoneal dialysis (PD) presented with one day of acute onset headache, confusion and ataxia. Two days prior, he was diagnosed with dermatomal zoster and was treated with valacyclovir 1000 mg thrice daily. Lumbar puncture showed no pleocytosis, but protein elevation at 90 mg/dL. EEG showed no epileptiform activity and MRI and MRA brain were normal. Because his symptoms started after the initiation of overdosed valacyclovir, medication toxicity was considered more likely than VZV encephalitis. PD was continued, but he deteriorated with worsening mental and pulmonary status after aspiration, requiring intubation. Subsequently, he underwent 3 daily hemodialysis (HD) treatments without improvement. On the 3rd day post-intubation, the CSF VZV PCR returned positive prompting intravenous acyclovir at 5mg/kg/day. Over the next day, he showed marked mental status improvement and got extubated. The serum VZV PCR also resulted positive which was diagnostic of disseminated herpes zoster with encephalitis. After 6 days of intravenous acyclovir therapy, he was discharged on valacyclovir 500mg twice daily to complete 21 days of therapy.


Herpes zoster encephalitis and valacyclovir neurotoxicity can lead to similar presentations and pose a diagnostic challenge. Due to low volume of distribution and low protein binding, valacyclovir is highly dialyzable. Hemodialysis can be helpful diagnostically. Our patient’s neurologic symptoms started after an inappropriately high dose of valacyclovir was prescribed. He did not improve with hemodialysis, pointing away from valacyclovir overdose and more toward VZV encephalitis. This case underscores the need for dosing adjustments in patients with renal insufficiency and the need for clinical awareness to keep both diagnoses in mind.