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Efudix

What is Efudix?

The active ingredient of Efudix is 5 – Fluorouracil (5FU- a chemotherapy drug used successfully to treat many forms of cancer since the 1960’s. Efudix (5FU in cream form) is therefore best thought of as a chemotherapy “anticancer” cream.

How does Efudix work?

Abnormal (pre-cancer or cancer) cells in the skin selectively absorb 5FU which then blocks DNA synthesis in the cells, leading to the death of these abnormal cells. Normal cells are unaffected by this process.

What conditions are treated with Efudix?

Efudix is mainly used in the treatment of Actinic Keratoses, a  precancerous skin condition It is also used for

  • Bowen’s Disease – an extremely superficial form of SCC
  • Severely sun damaged skin


Why is Efudix NOT able to treat most skin cancers?

Unfortunately Efudix does not penetrate deeply enough to be effective against the majority of skin cancers. It will certainly treat the surface of basal cell and squamous cell carcinomas, but not the entire thickness of the cancer. Local injectable forms of 5FU have also proved unreliable and intravenous 5FU has too may systemic side effects to be useful.

Is there any systemic absorption of 5FU?

5FU is selectively absorbed by the abnormal cells with very little absorption by normal skin. However, there may be very small amounts absorbed when larger areas of abnormal skin are treated which is why it is not used in pregnancy. Very rarely nausea vomiting and loss of appetite may occur, but are generally mild.

How effective is Efudix?

It is highly effective in the treatment of Actinic Keratoses, especially if widespread over large areas of skin. It is most effective when used on the face, scalp and neck, but is also effectively used on the chest, arm, back of hands an occasionally on the leges. Treatment will very often have to be repeated at intervals and this is perfectly safe to so.

What about the Efudix treatment reaction?

For Efudix to be an effective treatment it must kill the abnormal cells. When this occurs, typically there is a “reaction” in the skin. This reaction develops slowly over the first week, with the affected skin appearing red and slightly scaly. In the second week the reaction intensifies with increasing redness, crusting and scabbing of individual lesions. The treated area may become swollen, itchy and somewhat uncomfortable. Many more lesions than were initially apparent become obvious. Typically the reaction looks worse than it feels!

Treatment usually lasts for 2 to 4 weeks depending on the anatomical area. This reaction is entirely normal and should be expected by all patients. The greater the number of abnormal cells in the skin, the stronger the reaction, and the better the long term results.

It is important not to stop the treatment because of concern regarding the reaction. Once the 5FU is ceased, other creams may be used to settle the reaction, which usually subsides quite quickly. The treated area will remain red for some time after the acute healing has occurred and again this is a sign of a good clinical response.

Apart from the expected reaction, are there any other side effects?

Some patients will develop a severe “normal” reaction and this may appear quite quickly and will generally be associated with significant swelling.
Other possible but not common, side effects include:

  • Formation of fine blood vessels
  • Loss of pigmentation
  • Sun sensitivity


True allergy to 5FU or to other cream components occurs rarely and usually only after multiple usage.

As described earlier, mild nausea, anorexia, tiredness and lethargy are very occasionally seen.


Further reading:



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