Fluorouracil (5-FU) Injection

• Type: Anticancer medication

• Drug Class: Antimetabolite / Pyrimidine analog

• Form: Sterile solution for intravenous (IV) injection or infusion

How It Works

• 5-FU is converted in the body to active metabolites that:

  • Inhibit thymidylate synthase, an enzyme necessary for DNA synthesis

  • Get incorporated into RNA and DNA, disrupting their function

• This causes cell cycle arrest and death of rapidly dividing cancer cells (most active in the S-phase of cell cycle).

Common Uses

Fluorouracil injection is a key drug in the treatment of many solid tumors, including:

• Colorectal cancer (often in combination regimens like FOLFOX or FOLFIRI)

• Gastric cancer

• Pancreatic cancer

• Breast cancer (in combination protocols)

• Head and neck cancers

• Basal cell carcinoma and actinic keratosis (topical 5-FU form)

Advantages

• Widely used and well-studied drug with decades of clinical experience

• Can be given as bolus injection or continuous infusion (infusion is often better tolerated and more effective)

• Often combined with leucovorin (folinic acid) to enhance its effect on thymidylate synthase

Possible Side Effects

Common:

• Bone marrow suppression (low white blood cells, anemia, low platelets)

• Diarrhea

• Mouth sores (mucositis)

• Nausea, vomiting

• Hair thinning

Serious / Dose-Limiting:

• Severe neutropenia (infection risk)

• Hand-foot syndrome (palmar-plantar erythrodysesthesia) with prolonged infusions

• Cardiotoxicity (chest pain, arrhythmia – rare but serious)

• Severe toxicity in patients with DPD (dihydropyrimidine dehydrogenase) deficiency

Precautions

• Genetic testing for DPD deficiency may be recommended before starting therapy (to avoid life-threatening toxicity)

• Close monitoring of blood counts, liver and kidney function during treatment

• Use with caution in patients with a history of cardiac disease

• Good hydration and antiemetics can help manage side effects