Valacyclovir-associated acute kidney injury

A 90-year-old woman presented with grouped vesicular lesions with crusts on the left half of the face, and she was diagnosed with herpes zoster. She was received 3000 mg/d valacyclovir at a dermatology clinic near her home. Her medical history included hypertension, ischemic heart disease, pulmonary tuberculosis, and dementia. She was not prescribed nonsteroidal anti-inflammatory drugs. She developed anuria and coma after 2 days of valacyclovir administration. Valacyclovir was discontinued and replaced with amenamevir, but her clinical findings did not improve. She was admitted to our hospital 3 days after the initial dose. At the time of admission, her blood pressure was 175/107 mm Hg, she was anuric and comatose, and she had ongoing seizure-like activity. Her serum creatinine level increased from 1.0 to 4.7 mg/dl. The results of cerebrospinal fluid analysis and head computed tomography were unremarkable. Polymerase chain reaction was not performed. Microscopic analysis of the urine revealed birefringent needle-shaped crystals (Figure 1a and b ). The concentrations of acyclovir on admission were high (urine, >53.6 μg/ml; serum, 13.3 μg/ml), and she was diagnosed with acute kidney injury attributable to crystalluria and acyclovir-related encephalopathy associated with valacyclovir administration. We discontinued valacyclovir and continued conservative treatment. Her serum creatinine level recovered to 0.8 mg/dl, and her neurologic status improved to its previous level. Valacyclovir is a prodrug and is rapidly converted to acyclovir in the body, and it has higher bioavailability when taken orally compared with acyclovir. Acyclovir-induced acute kidney injury is believed to occur when precipitated acyclovir crystals obstruct the renal tubules. Care regarding dosing is required when administering valacyclovir to elderly patients. When overdose of valacyclovir is suspected, examination of the urinary sediment findings is important in making a diagnosis and determining the course of treatment. All the authors declared no competing interests. All authors provided clinical care for the patient and drafted, edited, and approved the final version of the manuscript. The authors thank Joe Barber, Jr., PhD, from Edanz (https://jp.edanz.com/ac), for editing a draft of this manuscript and Dr. Hidenobu Matsumoto for revising the figure. Written consent for publication was obtained from the patient's surety.