[Acyclovir-induced neurotoxicity and acute kidney injury in an elderly diabetic patient treated with valacyclovir: report of a case].

An 83-year-old Japanese man had a 29-year history of well-controlled diabetes mellitus. His HbA1c level was approximately 6.0%, with no microalbuminuria and a serum creatinine level seven days before admission of 0.8 mg/dl (eGFR: 69.67 ml/min/1.73 m(2)). Five days before admission, he visited an ophthalmologist with inflammation of the right palpebra and conjunctiva and began taking valacyclovir at a dose of 3,000 mg for the treatment of herpes zoster. Two days before admission, he was prescribed loxoprofen at a dose of 180 mg for a headache. One day prior to admission, he developed dysarthria, wandering and loss of appetite. He was subsequently admitted to our hospital with progressive deterioration of consciousness (Japan Coma Scale: II-20). On admission, he exhibited renal dysfunction, with a serum creatinine level of 5.11 mg/dl (eGFR: 9.16 ml/min/1.73 m(2)). Based on his diverse symptoms and current treatment with valacyclovir, the patient was diagnosed with acyclovir-induced neurotoxicity and his symptoms rapidly improved after hemodialysis. The serum acyclovir level on admission was found to be 9.25 μg/ml. Although acyclovir-induced neurotoxicity is commonly seen in elderly patients with renal dysfunction, there are also reports of this condition in patients with a normal renal function. Valacyclovir is frequently prescribed to the elderly to treat diseases such as herpes zoster. As valacyclovir induces renal dysfunction, which raises the serum acyclovir level to the toxic range, special attention must be paid when administering this drug in elderly subjects.