BACKGROUND: Although cardiotoxicity associated with 5-Fluorouracil (5-FU)administration is infrequent, there are case reports of acute coronary syndromes. We report on patientsundergoing 5-FU chemotherapy who developed cardiac symptoms during its administration.MATERIAL/METHODS:In patients receiving 5-FU who experienced cardiac-related symptoms, ECG and serum cardiac enzyme determinationwere performed. If cardiotoxicity was detected, 5-FU infusion was interrupted, and the patients receivedsublingual nitrates and cardiac monitoring, while patients with more than 2-fold elevated enzyme levelswere monitored in a coronary care unit for at least 72 hours. In cases of acute myocardial infarction,5-FU was terminated.RESULTS: Of 427 patients entering the study, 17 (4%) developed clinical symptomsand ECG abnormalities indicating 5-FU cardiotoxicity. Patients with continuous infusion (c.i.) of 5-FUhad a higher incidence of cardiotoxicity (12/197, 6%) than the remaining (5/235, 2.1%) (p=0.067), butmore toxicity was encountered in patients with c.i. of 5-FU+LV for 24 hours for 5 days than in patientswith the same regimen of 5-FU without LV (p

Keywords: Antimetabolites, Antineoplastic, Dose-Response Relationship, Drug, Drug Administration Schedule, Electrocardiography, Fluorouracil, Heart, Neoplasms