Neurologic Acyclovir Toxicity in the Absence of Kidney Injury

Herpes zoster (zoster) also commonly known as "shingles," occurs following re-activation of the varicella zoster virus. It contributes a large cost burden to the U.S. health care system, with an estimated 1 million cases costing $1 billion annually. The current gold standard treatment is acyclovir, which limits viral replication. However, acyclovir has been reported to cause neurotoxicity in patients with acute or chronic kidney disease.

This case presents an occurrence of acyclovir-induced toxic encephalopathy in a patient with normal renal function. A 63-year-old male presented to the emergency department with ataxia, tremors, fluctuating aphasia, confusion, agitation, and fatigue. Results of imaging, lumbar puncture, and laboratory studies directed clinicians toward acyclovir toxicity, despite a normal creatinine level. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians will likely be the first point of contact in the health care system following the onset of acyclovir toxicity. With an increasing incidence of zoster disease, such atypical toxic manifestations may increase. Early recognition is important to avoid permanent neurologic compromise.