5-FU is a cytotoxic drug. This means that it kills cancer cells. 5-FU kills cells by interfering with the activities of DNA and RNA, which are molecules in the cells important in expressing genetic material.
Most frequently, 5-FU is given as an injection into the vein (intravaneous injection or IV). Many different doses and regimens are used depending on the cancer diagnosis, and patients should discuss with their physician the dose based on the individual protocol used. A sample dose is 500 to 1, 000 mg per square meter of body surface area given as a 24-hour infusion for four to five days every three weeks. A dose of 425 mg per square meter of body surface area per day for five days given along with the drug leucovorin is also common.
Patients with allergic reaction to 5-FU should not be administered this drug. It is also inadvisable for pregnant women. 5-FU should be administered with caution to patients with impaired liver or kidney function, or in patients with a history of heart problems.
The amount of drug given and the duration of which it is given during a single session greatly influences the side effects seen. For example, when given as a 24-hour continuous infusion, the most common side effects are diarrhea and mouth ulcers. If 5-FU is given as a bolus infusion (a high quantity of the drug all at once), the most common side effect is bone marrow suppression; this results in a decrease of the white blood cells responsible
The severity of the side effects is increased when 5-FU is given with the drug leucovorin. Vomiting, diarrhea, nausea, and loss of appetite (anorexia) may occur regardless of how 5-FU is administered. The diarrhea side effect may be severe in some patients, and it is important for them to alert their doctor immediately so that appropriate medications for the diarrhea can be prescribed.
5-FU may cause rashes, increased sensitivity to sunlight, changes in skin color, changes to the fingernails, and redness and swelling in the palms of the hands and soles of the feet. Patients who have had heart disease before starting therapy with 5-FU may have problems with blood flow to the heart. Rarely, 5-FU may cause an allergic reaction, dry eyes, sleepiness, confusion, headache, changes in walking gait, involuntary rapid movement of the eyes, and difficulty speaking. When 5-FU is applied directly on the skin, there are usually no side effects except for those to the skin itself. These may include burning sensations, pain, and darkening of the skin color.
Some authorities recommend discontinuation of 5-FU therapy as soon as mild side effects are observed as a way of reducing the extent of injury to the digestive tract. Administration may then be restarted at a lower dose after the side effects have stopped.
People taking fluorouracil should consult their doctor before taking any other prescription drug, over-the-counter drug, or herbal remedy.
—A medicine that kills (cancer) cells.
—A molecule found in all living cells that contains tiny bits of genetic information.
—Administration of a medication as a liquid through an intravenous (IV) device.
—A molecule found in all living cells that plays a role in transmitting information from the DNA to the protein-forming system of the cell.