Fluorouracil 500 mg Injection (5-FU) — Antimetabolite Chemotherapy for Solid Tumors Fluorouracil 500 mg Injection is a widely used anticancer chemotherapy medicine containing 5-fluorouracil (5-FU), a pyrimidine antimetabolite that disrupts DNA and RNA synthesis in rapidly dividing cancer cells. This intravenous injection is administered under expert medical supervision as part of treatment protocols for breast cancer, colorectal cancer, stomach cancer, pancreatic cancer, and other solid tumors, often in combination with other chemotherapy agents. Due to its potent effects on cancer cells and normal tissues, Fluorouracil requires careful clinical monitoring including frequent blood counts, liver and kidney function tests, and management of side effects such as mucositis, nausea, diarrhea, and depressed immunity.