Acute renal insufficiency due to oral acyclovir in a man with sickle cell trait

Several published reports have suggested that oral acyclovir can cause renal insufficiency, but baseline renal function was either abnormal or unclear in those reports. We describe a patient with oral acyclovir-induced acute renal failure and a normal serum creatinine level documented just before exposure to the drug. Conceivably, competition with a cephalosporin for renal tubular elimination predisposed our patient to nephrotoxic serum levels of acyclovir. In addition, the patient had sickle cell trait, which might have contributed to a disproportionate degree of hyperkalemia and acidosis seen early in the patient's clinical course.