Adenine Arabinoside and Allopurinol — Possible Adverse Drug Interaction

To the Editor: Two patients with chronic lymphocytic leukemia were treated with vidarabine (adenine arabinoside), one because of severe mucocutaneous herpes simplex and the other because of disseminated cutaneous varicella zoster. Both were receiving allopurinol, 300 mg daily. Severe neurotoxicity consisting of coarse, rhythmic tremors of extremities and facial muscles and impaired mentation developed on the fourth day of vidarabine treatment in both patients. Neither had impaired renal function, a condition associated with neurotoxicity in patients treated with adenine arabinoside.¹ Since allopurinol affects purine metabolism, we reviewed available information that might indicate possible mechanisms for adverse drug interactions. Mammalian cells. . .