Early-Onset 5-Fluorouracil Toxicity in a Patient Negative for Dihydropyrimidine Dehydrogenase Mutations: The Clinical Course of Reversal with Uridine Triacetate.

An antimetabolite pyridine analog, 5-fluorouracil (5-FU), is used to treat solid tumors. Early toxicities may occur at standard doses of 5-FU due to dihydropyrimidine dehydrogenase (DPD) deficiency. Uridine triacetate, approved by the Food and Drug Administration in 2015, is an oral prodrug of uridine, a pharmacologic antidote for 5-FU toxicity. To our knowledge, this is the first case report that documents the clinical course of a patient treated with uridine triacetate to reverse early-onset 5-FU toxicity negative for DPD mutations. We describe the case of a 73-year-old man with anal cancer treated with standard-of-care chemotherapy and radiation. Two days after completion of his initial 5-FU infusion, the patient developed severe mucositis and extreme fatigue, followed by a rapid decline in his blood cell counts and fevers. The patient was initiated on uridine triacetate 86 hours after completion of his 5-FU infusion. Over a 10-day hospital length of stay, the patient's absolute neutrophil count recovered to within normal limits, and his mucositis significantly improved. At follow-up visits, the patient denied any residual symptoms of 5-FU toxicity. We describe the patient's clinical course from hospital presentation to 31 days after initiation of uridine triacetate.