Fluorouracil is an antitumor agent from the group of antimetabolites. As a pyrimidine antagonist, it disrupts DNA synthesis and thus inhibits cell division. Fluorouracil itself does not have antineoplastic activity. The antitumor effect is manifested in the body after enzymatic transformation of fluorouracil into phosphorylated forms - 5-fluorouridine and 5-fluorodeoxyuridine.