Symptomatic 5-fluorouracil-induced sinus bradycardia

5‐Fluorouracil (5‐FU) is a commonly used anti‐neoplastic agent. 5‐FU has been not uncommonly associated with cardiotoxicity, although the many potentially causative mechanisms are yet to be established. Here, we present the case of a 61‐year‐old gemstone miner who developed symptomatic sinus bradycardia while receiving a continuous 5‐FU infusion combined with radiotherapy for locally advanced rectal cancer. This dysrhythmia is an unusual type of 5‐FU toxicity, our case being the second described. We review the actions of 5‐FU and the various proposed mechanisms of its cardiotoxic effects.