Background: Uncommon early-onset severe toxicities from 5-fluorouracil (5-FU) and capecitabine can be fatal if early warning signs are not recognized and treated promptly.

Objectives: This article delineates the differences between expected side effects and uncommon early-onset severe toxicities from 5-FU and capecitabine. It also provides background for understanding the reasons patients may develop these toxicities and reviews the efficacy of standard supportive care against a novel therapy (uridine triacetate).

Methods: A panel of nurses convened to review the literature about toxicities associated with 5-FU and capecitabine administration and determined methods to educate nurses about toxicities and treatment.

Findings: Standard supportive care for 5-FU and capecitabine toxicities is associated with high fatality rates. Uridine triacetate treatment within 96 hours of administration is associated with survival.