Fluorouracil cream. Nurse holding a box containing a tube of fluorouracil cream, marketed under the name Efudix. This thymidylate synthase inhibitor is a cytotoxic (toxic to cells) drug. When used as an injection it is used to treat various cancers, including colon cancer, breast cancer and pancreatic cancer. As a cream, it is used to treat actinic keratosis, basal cell carcinoma (skin cancer), and skin warts.