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Cancer Glossary Cancer Diet Guide Support Groups

5-FU (5-fluorouracil)  

Indications: 5-FU is an abbreviation of the word fluorouracil, which is a medicine that fights cancer by inhibiting or slowing down the growth of cancerous cells on the skin that are usually caused by long-term exposure of the skin to sunlight. It is usually applied directly to the skin where it causes the non-melanoma cancerous cells to die. It is used to treat superficial skin cancers that are only in the upper skin layer. It may also be used to help treat some issues with cancers in the eye when other more common treatments cannot be used.

This medication focuses on fast-growing cells such as those in actinic keratoses. This medication has been shown to be approximately 90% effective with topical skin cancers. Some of the side effects can include skin redness and some swelling of the area. There may also be a burning sensation and the skin will usually change color and may ooze. Pain and itching are common as the cancerous cells begin to be affected by the medicine. Often, it mimics the symptoms of an allergic reaction as it works on the cancerous cells. A person's skin may also be extra sensitive to sunlight, so should be covered when going outdoors while using this medication. Usually, 5-FU does not lead to scars on the affected skin.   

Dosage: 5-FU can be used once or twice each day for up to several weeks and should be rubbed gently into the affected skin areas.  This medicine is usually found in the form of a cream or a solution that you put on your skin.  It is best to use some sort of applicator that is not made of metal.  If you use your hands, you should be sure to wash your hands thoroughly after the application.  You should not bandage the treated areas or apply a dressing unless your physician has recommended it.  It is important to use the dose prescribed by your doctor, and to use it only as he has directed, whether you apply it once or twice each day. It is important to follow up with your medical specialist to be sure that the entire skin cancer has been eliminated.


Overdose:  since it is a tropical treatment, the risk of overdose is almost inexistent. However, 5-FU may cause irritation and/or inflammation even at normal. If irritation is such that you cannot continue the treatment, contact your health care provider before taking any decision.  


Missing dose: It is important that you use 5-FU exactly as indicated by your physician or pharmacist; in case you forgot to apply the medication, apply the missed dose as soon as you remember it; if it is almost time for the next dose, skip the missed dose and continue your regular dosing. Double dose is not recommended.  

Storage: Store 5-FU at room temperature and out of reach of children. The drug should not be kept in the light or moisture. After use, do not throw the container in the garbage. For more information on proper disposal of 5-FU, talk to your physician or pharmacist.    

Contraindication: There are no major contraindications with 5-FU, but as with all medications, it is important to discuss your current health with your physician before beginning to use a new medication. In addition, while you are treated with 5-FU , you need to take the following precautions: 

·         avoid the treated area to prolonged sun exposure  

·         tell your doctor if you have a history of other skin problems or acne rosacea  

·         Tell your physician if you are taking prescription or nonprescription medications including aspiring, vitamins and nutritional supplements.   

Mechanism of action (MOA): 5-FU acts by inhibiting DNA synthesis and thus slows or stops the division of cancer cells.  


Interactions : It is important to tell your doctor about any prescription or over the counter medications you are taking, especially other topical medications in case of the possibility of negative drug interactions.


Side effects: in some patients, 5-FU can cause skin reactions. Common 5-FU side effects include:  

  • rash 
  • soreness 
  • burning 
  • crusting 
  • redness 
  • discoloration 
  • irritation 
  • Itching.  

If the side effects above persist for days or weeks, contact your oncologist. In addition, contact your doctor immediately if you experience any of these symptoms:  include:  

  • fever 
  • chills 
  • vomiting 
  • bloody diarrhea 
  • severe red skin rash 
  • Severe stomach pain.  


For more chemotherapy side effects and steps to take manage them, please visit www.cancereffects.com