Topical 5-Fluorouracil 5% cream is often abbreviated to 5-FU. The trade name in New Zealand is Efudix™, which is has a partial Drug Tariff subsidy when prescribed by a dermatologist (July 2006).
What is fluorouracil used for?
5-Fluorouracil is most often prescribed for solar keratoses and Bowen disease (in situ squamous cell carcinoma). It destroys sun-damaged skin cells so the skin appears smoother and more youthful. It works best on face and scalp, and is less effective on other areas. Fluorouracil is also occasionally used to treat the following skin conditions:
- Superficial basal cell carcinoma
- Viral warts
- Genital warts
- Disseminated superficial porokeratosis & linear porokeratosis
How should it be used?
5-Fluorouracil is a powerful, destructive medication and must be used exactly as directed. Keep it locked up so other people cannot mistakenly use it to treat a rash. It should not be used during pregnancy. It is best to use 5-fluorouracil during the winter months, generally for two to eight weeks.
Sometimes 5-fluorouracil is prescribed with tretinoin cream. This combination works best if the tretinoin has been used for at least two weeks prior to starting 5-fluorouracil. Tretinoin cream enhances the effect of 5-fluorouracil by peeling off the top layer of skin. It reduces the time required for the course of 5-fluorouracil treatment. Tretinoin cream can be continued afterwards long term to reduce the signs of photoageing and prevent deterioration of course, using very careful sun protection.
The 5-FU cream is applied once or twice a day after washing the area that is to be treated with plain water. A tiny amount of the cream should be gently rubbed into all of the treatment areas with a fingertip. It is important to apply it to all the skin and not just visible lesions. Afterwards rinse the finger thoroughly with water (or use a glove to apply the 5-FU).
What are the results of treatment?
5-FU frequently results in a mild to severe stinging or burning sensation, depending on the sensitivity of the skin, the severity of the sun damage and how long it has been used for. After five to ten days of treatment, the sun-damaged parts of treated skin become red and irritated. As treatment is continued, sores and crusts may appear. These raw areas result from the destruction of defective skin cells. They are a necessary part of 5-FU treatment. They can be covered with a dressing if you prefer.
Mild reaction after 10 days treatment to keratoses
Keratoses after 2 weeks' treatment
Bowen's disease ulcerating after 3 weeks' treatment
Avoid putting 5-fluorouracil in the eyes; it is not normally used on eyelids. Keep it off the lips, unless specifically requested to use it on this site. Use 5-FU with care in skin folds, since it may irritate more severely in these areas.
Treated skin should normally be very carefully protected from the sun; stay indoors during the middle part of the day. If the treated area is inadvertently exposed to the sun, the reaction to 5-fluorouracil is more vigorous than normal, which may be unpleasant but the result may in fact be more successful!
Many are able to use make-up over the 5-FU cream, but it can sometimes sting.
It is best to arrange for your dermatologist to review you during treatment to check on progress and to determine how long to continue using 5-FU. If any unusual or severe reaction occurs, stop applying 5-FU and contact your dermatologist.
After you have been instructed to stop using the 5-FU, you may be prescribed a specific moisturiser or mild topical steroid to help healing. If you have been given no specific instructions, apply plain white petrolatum thinly to raw and crusted areas at bedtime. Stop the petrolatum when the crusts and scabs have healed.
When treatment is stopped the skin heals rapidly. It takes two to four weeks for healthy new skin to replace the sun-damaged skin destroyed by the 5-FU. After healing, the treated areas are often redder than normal and may feel more sensitive; this redness and sensitivity will gradually fade over a few weeks. Occasionally it persists for several months but normal make-up can be used to cover it if desired.
Persistent or recurrent solar keratoses can be treated with a further course of 5-FU, imiquimod cream or by cryotherapy. However, it is important to ask your dermatologist if this is appropriate because skin cancers can look very similar and may need surgery or other procedures.
Complications of treatment
The following complications arise occasionally:
- Excessive inflammatory reaction resulting in ulceration
- Subsequent persistent white marks or scarring
- Irritant contact dermatitis or allergic contact dermatitis affecting all treated areas, including skin that is not sun damaged
- Secondary infection (impetiginisation)
- Undiagnosed skin cancers these may appear to heal with 5-FU but recur later requiring surgery.