Pharmacology General 764a493d Most common side effect of 5-Fluorouracil is- A GI. toxicity B Bone marrow depression C Cardiotoxicity D Neurotoxicity High-Yield Explanation Ans. is 'a' i.e., GI toxicity o The earliest untoward symptoms during a course of 5-FU are anorexia and nausea; these are followed by stomatitis and diarrhea.