Fluorouracil 5% w/w is a topical antimetabolite and antineoplastic agent, primarily used for the treatment of multiple actinic (solar) keratoses and superficial basal cell carcinomas. It is a pyrimidine analog that interferes with DNA and RNA synthesis, leading to cell death in rapidly proliferating cells, particularly in sun-damaged and pre-cancerous skin. In the Indian context, it is a crucial, cost-effective option for managing widespread pre-malignant skin lesions, especially in patients with significant sun exposure.
Adult: Apply a thin layer to the affected area(s) once or twice daily as directed. For Actinic Keratoses: Typically applied once or twice daily for 2 to 4 weeks. For Superficial Basal Cell Carcinoma: Applied once or twice daily for 3 to 6 weeks, possibly longer under medical supervision.
Note: 1. Wash hands before and after application. 2. Clean and dry the affected area. 3. Apply a thin layer using a non-metal applicator or fingertip (wear a glove). 4. Avoid contact with eyes, eyelids, nostrils, mouth, and mucous membranes. 5. Do not cover with occlusive dressings unless specifically instructed by the physician. 6. Wash off thoroughly if accidental contact with eyes or mucous membranes occurs.
Fluorouracil is a prodrug that is converted intracellularly to active metabolites: 1) Fluorodeoxyuridine monophosphate (FdUMP) inhibits thymidylate synthase, blocking the conversion of deoxyuridylic acid to thymidylic acid, thereby inhibiting DNA synthesis. 2) Fluorouridine triphosphate (FUTP) is incorporated into RNA, disrupting RNA processing and function. This dual action leads to cytotoxic effects, particularly in rapidly dividing pre-malignant and malignant cells.
Pregnancy: Category X. Fluorouracil is teratogenic and embryotoxic. Contraindicated in pregnancy. Women of childbearing potential should use effective contraception during and for at least 3 months after treatment.
Driving: Unlikely to affect driving ability. However, if severe local reactions (e.g., pain, visual disturbance from periocular application) occur, caution is advised.
| Leucovorin (Folinic Acid) | Potentiates the cytotoxicity and toxicity of fluorouracil by stabilizing the binding of FdUMP to thymidylate synthase. Relevant if systemic absorption occurs. | Major |
| Cimetidine | May inhibit the hepatic metabolism (via CYP450) of systemically absorbed fluorouracil, potentially increasing toxicity. | Moderate |
| Warfarin | Fluorouracil may potentiate the anticoagulant effect of warfarin, increasing INR and risk of bleeding. | Major |
| Phenytoin | Fluorouracil may increase phenytoin levels, leading to toxicity. | Moderate |
| Topical Corticosteroids | May reduce the desired inflammatory therapeutic response to fluorouracil if applied concurrently to the same area. | Moderate |
| Brivudine, Sorivudine | Contraindicated. These antiviral drugs inhibit DPD and can cause fatal enhancement of fluorouracil toxicity. | Contraindicated |
Same composition (Fluorouracil (5% w/w)), different brands: