Fluorouracil

Blocks thymidylate synthase, halting DNA synthesis in rapidly dividing cells. Applied across a field, it destroys the atypical keratinocytes of actinic damage — including the subclinical ones — which is why the therapeutic endpoint is visible erosion rather than the absence of a reaction.

HOUSE NOTES

• ▸Dosed to a tissue endpoint rather than a calendar: continue until the inflammatory response reaches the erosion stage, then stop. Usual duration two to four weeks.
• ▸The reaction is unsightly during therapy and usually for several weeks after stopping, and complete healing may take one to two months.
• ▸There is no clinical studies section on the label — no success rate, no comparator, no sample size. The evidence exists in the literature; none of it is on the box.
• ▸Contraindicated in DPD enzyme deficiency, with one reported case of life-threatening systemic toxicity from the 5% topical cream.
• ▸The label warns it may be fatal if ingested by pets, and to avoid residues on hands, clothing, carpeting and furniture. Nothing else in this register carries that warning.
• ▸Irritation is scored at 10 because erosion is the intended endpoint, not a side effect to be minimised.

MEASURED ENDPOINTS

SUPPORTING RECORDS