Efudex™ is a medication used to treat pre-cancerous and cancerous lesions of the skin. Efudex™ contains the active ingredient 5-fluorouracil (5-FU), which is an anti-metabolite. That is to say, it works by inhibiting the ability of rapidly dividing cells, such as sun-damaged skin cells, to proliferate. Efudex™ is most often prescribed topically (applied directly to the skin) for the treatment of pre-cancerous spots (actinic keratoses) and skin cancers (superficial basal cell carcinomas, off-label for squamous cell carcinoma in situ), but it is also used for the treatment of warts and for other rarer skin conditions (disseminated superficial actinic porokeratosis, linear porokeratosis etc).

Efudex™ makes your skin more sensitive to the sun, so it is best applied during the winter months. Efudex™ is also not suitable for all patients:

  • It should not be used in pregnancy because it is known to cause birth defects and for similar reasons, it is not recommended if nursing.
  • People with rare genetic mutations (dihydropyrimidine dehydrogenase deficiency) accumulate the active ingredient in Efudex™ in toxic amounts and should therefore not receive treatment with this medication.
  • Efudex™ also makes healing from cold sores more difficult, so if you have a history of recurrent cold sores or currently have symptoms, let your Dermatologist know.


Frequently Asked Questions on Efudex™

How Will Treatment with Efudex™ Work?

You will receive a prescription for Efudex™ (which comes as a 25g cream). There is no associated cost as Efudex™ is covered by OHIP.

  • Apply the cream to the areas requiring treatment as directed by your Dermatologist (a fingertip sized amount is sufficient as you only need a very thin layer of Efudex™ on your skin). It is recommended to use disposable gloves when applying Efudex™, but if you use your hands make sure to wash them immediately afterwards.
  • The cream needs to be applied twice a day and remain on the areas requiring treatment for 8 hours, after which you can wash it off.
  • Also, avoid applying Efudex™ too close to the eyes, eyelids, nose and mouth as it can be irritating. Be extra careful when applying to skin folds (behind ears, sides of nose, etc) as extra cream can accumulate in these areas and result in a more severe reaction.
  • The duration of treatment depends on what is being treated:

Apply twice daily for 3 weeks if treating precancerous spots (actinic keratoses).

Apply twice daily for 4 weeks if treating superficial basal cell carcinoma.

*The exact length of treatment may differ based on your situation, so follow the instructions given by your Dermatologist.

What to Expect During and Following Treatment with Efudex™?

The most frequent symptoms resulting from treatment with Efudex™ are stinging and burning skin sensations. After a few days of treatment, the skin will become red, scaly and tender. As treatment is continued, redness may worsen along with the development of ulcers and crusting areas. You can apply petrolatum jelly over these areas to keep them moist (this will help them heal), but avoid cosmetics and other topicals until your skin heals. The extent of the reaction to Efudex™ will depend on the severity of pre-cancerous and cancerous skin lesions being treated. Generally, the more sun-damaged cells you have, the more severe the reaction to Efudex™ will be. This is normal and your skin will heal over the next 2-8 weeks after treatment has stopped. Your skin’s reaction to Efudex™ will also be intensified by exposure to ultraviolet light, so avoid the sun during peak hours and wear protective clothing while being treated.

As your skin’s normal barrier will be broken due to ulcers, you are at an increased risk of infection, so watch for the signs and symptoms and call your Dermatologist if you have any concerns. More rarely, flu-like symptoms (fever, nausea, headache, etc) have been described if you apply too much Efudex™ or if have a stronger than normal reaction to the treatment.

As a general rule, Efudex™ will effectively treat 80% of pre-cancerous and cancerous lesions in 80% of patients after one treatment. Depending on your specific situation, more than one treatment may be required.

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