Do not use other prescription or over-the-counter skin products without first talking to your doctor during treatment with fluorouracil topical. They may interfere with treatment or increase irritation to the skin. Drugs other than those listed here may also interact with fluorouracil topical.o not use other prescription or over-the-counter skin products without first talking to your doctor during treatment with fluorouracil topical. They may interfere with treatment or increase irritation to the skin. Drugs other than those listed here may also interact with fluorouracil topical.