Another medication used for this purpose is 5-fluorouracil (5-FU). This is an antimetabolite (a drug that inhibits another chemical that is part of normal processes) that works by irreversibly inhibiting the enzyme thymidylate synthetase resulting in impaired DNA synthesis. This reduces fibroblast proliferation and inhibits collagen type 1 production which is a key protein in scar formation. This medication is commonly used in ophthalmology after glaucoma filtration surgery. In this usage, it is injected under the conjunctiva to prevent scarring around the surgical site.