5-fluorouracil (5-FU) is a fluoropyrimidine that is used in cancer treatment but also has several uses in dermatology. It was first synthesized in the late 1950s and approved by the FDA in 1962 for the treatment of colorectal cancer. 5-fluorouracil has been studied for use in a variety of skin conditions including keloid scarring, hypertrophic scars, vitiligo, cutaneous infections like viral warts and molluscum contagiosum, Hailey-Hailey disease, and skin changes related to photoaging. Two of the most common conditions for which 5-FU is prescribed are actinic keratosis and warts.
5-Fluorouracil for Actinic Keratosis
Actinic keratosis are rough and scaly patches of skin that develop from UV radiation exposure over many years. Some actinic keratoses can develop into squamous cell carcinoma (a type of skin cancer). The more actinic keratoses there are, the higher the risk of developing this type of skin cancer. The prevalence of AKs tends to increase with age – with < 10% occurrence in 20-29 year old and > 80% occurrence in 60-69 year olds.
There is significant evidence supporting the use of 5-FU for the treatment of actinic keratosis (AKs). Basically 5-fluorouracil works by selectively destroying sun damaged skin cells. There will be an inflammatory reaction when first starting treatment for AKs that may include oozing, crusting, and scabs. As the treatment course is completed this reaction will subside. After applying the cream, patients should wash their hands thoroughly and wait 20 minutes to apply any other skincare product like moisturizer.
In a trial conducted by Veterans Affairs (VA) across 12 VA medical centers, 932 veterans were enrolled who had 2 or more keratinocytes carcinomas in the previous 5 years. In the 5-FU group, there was a 73% reduction in actinic keratosis count compared to a 26% reduction in the treatment group that used only the cream vehicle.
5-Fluorouracil for Warts
The combination of 0.5% 5-fluorouracil and 10% salicylic acid has been available in Europe for over 30 years for the treatment of warts. The combination of the two ingredients has been shown to be more effective than 5-FU used on its own. Both a cream and a solution have been used for this indication sometimes with occlusion.
Before applying the 5-FU product, the warts should be debrided with a pumice stone. Most doctors will recommend occluding the wart after application. Cure rates for warts are typically high for this treatment – as high as 95% according to some research. These results can be seen within 12 weeks of consistent treatment.
Precautions with 5-Fluorouracil
5-fluorouracil is a potent treatment that produces drastic results for many patients. However you should also be aware of potential side effects and precautions to take before starting treatment. 5-FU should never be given to pregnant women as it can have severe consequences for the health of an unborn child.
Many side effects of 5-FU when used in dermatology are localized and related to inflammatory reactions in the skin. This medication makes the skin more sensitive to sunlight so proper sun protection should always be used. Skin reactions may include inflammation, redness, and pain and burning at the application site.
Studies have shown that there is not a significant difference between the use of a 5-fluorouracil 5% cream vs. a 0.5% cream. Since a lower dose may produce fewer side effects, it is often chosen over the higher dosage. Our compounding pharmacy makes a combination cream with 0.5% 5-FU and salicylic acid 10%.
Articles
Long-term Efficacy of Topical Fluorouracil Cream, 5%, for Treating Actinic Keratosis – A Randomized Clinical Trial – JAMA Dermatology
Topical 5-fluorouracil in dermatologic disease – International Journal of Dermatology
5-Fluorouracil in Dermatology: The Diverse Uses Beyond Malignant and Premalignant Skin Disease – Dermatologic Surgery
Intralesional 5-Fluorouracil in Keloid Treatment: A Systematic Review – Acta Dermato-Venereologica