Fluorouracil is an antimetabolite, as it interferes with the cell’s normal metabolic functioning, inhibiting DNA synthesis. It is a pyramidine analog which competes with thymidylate synthetase to inhibit DNA synthesis.
Fluorouracil is a pyramidine analog that causes a "thymine-less death" in cells. This is because it decreases thymidine monophosphate (dTMP), as 5-FU competes with deoxyuridine monophosphate (dUMP) for thymidylate synthase, inhibiting its action. Fluorouracil is converted to 5-FdUMP, which competes for thymidylate synthetase. This leads to blocked synthesis of the pyrimidine thymidine, which is a nucleoside required for DNA synthesis and replication. Without DNA synthesis, tumor cells undergo apoptosis.
This medication is indicated for treating slowly-growing solid tumors, with examples of stomach, colorectal, breast, ovarian, and pancreatic cancers.
Leucovorin is a drug that potentiates the activity of 5-fluorouracil (5-FU). 5-FU takes its active form as FdUMP, which then binds and inhibits the enzyme thymidylate synthase, but has a very short half-life. Leucovorin is a reduced folate, which helps with the 5-FU activity, dubbing it a "chemoprotectant." This combination is used to treat stomach and colorectal cancer.
5-FU interferes with the ability of abnormal cells to grow on the skin's top layer. It is indicated for topical administration to treat superficial basal cell carcinomas (BCCs). It is also used for actinic keratosis, superficial squamous cell cancers, and Bowen's disease.
This medication causes myelosuppression, leading to anemia (megaloblastic), neutropenia and thrombocytopenia. Unlike with methotrexate, this myelosuppression is not reversible with Leucovorin.
There is a high rate of the development of mucositis with 5-fluorouracil. These are defined as inflammatory lesions of the mucosa, and patients develop oral, nasal and alimentary tract mucositis.
Due to the severe gastrointestinal mucositis that is a side effect of 5-FU, patients can develop severe diarrhea. This is typically dose related, and is very common amongst patients.
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