When delivery matters: Diffuse coronary vasospasm with continuous, but not bolus, 5-FU infusion

5-Fluorouracil (5-FU) is a fluorinated pyrimidine chemotherapy analogue used to treat various gastrointestinal solid malignancy. It is known to be associated with cardiotoxicity. Here, we present a case of 58-year-old male with mucinous adenocarcinoma of the sigmoid colon who experienced global coronary vasospasm in setting of continuous 5-FU infusion refractory to prophylactic antianginal treatment. However, he was asymptotic when given bolus of 5-FU. Our case highlights the difference in toxicity between continuous and bolus 5-FU therapy and emphasizes the need for further research in the pathophysiology and treatment of cardiotoxicity related to 5-FU therapy.