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  • The antimetabolites of 5-FU disrupt cell functioning through inhibiting nucleotide creation and incorporation into DNA and RNA.

  • 5-FU is indicated for treating actinic keratosis and superficial basal cell carcinoma.

  • 5-FU has been used as off-label treatment for squamous cell carcinoma in situ, actinic chelitis, keratoacanthomas, among others.

  • 1%, 2%, and 5% preparations typically follow a once- or twice-daily application, while 0.5% cream follows a once-daily application for a duration dependent on the indication, anatomic location, and patient sensitivity to treatment.


  • 5-FU treatment should be avoided in patients with a history of hypersensitivity to the agent or those with dihydropyrimidine dehydrogenase deficiency.

  • 5-FU is teratogenic and is contraindicated in women who are or are planning to become pregnant.


  • 5-FU paired with curettage, a topical retinoid, or calcipotriol has been shown to be more efficacious in treating actinic keratosis.

  • Trunk and extremity lesions have an augmented response to 5-FU after a 2-week pretreatment with a topical retinoid.

  • The inflammatory adverse effects can be curbed by concomitant use of 5-FU and a topical corticosteroid without decreasing overall therapeutic efficacy.

  • The intensity of the inflammatory reaction is controlled by altering the frequency of application, duration of treatment, and concentration of preparation.


  • 5-FU elicits an intense inflammatory response and results in erythema, irritation, pain, pruritus, erosions and crusting at the application site within 5 to 10 days of starting treatment.

  • The nasolabial folds along with the periorbital and perioral areas are most sensitive to 5-FU treatment.

  • Effective resolution of lesions by 5-FU relies on high compliance with treatment regimens to facilitate a strong inflammatory response.


The clinical use of 5-fluorouracil (5-FU) as a chemotherapy agent was discovered in 1957. In a landmark publication by Heidelberger et al, a new class of antitumor compounds known as fluorinated pyrimidines were postulated to have tumor-specific inhibitory effects via disruption of DNA synthesis.1 It was not until the early 1970s that clinical trials carried out by Cummings et al reported the remarkable response of anal cancer to intravenous 5-FU concomitant with radiation.2 Subsequent studies revealed intravenous 5-FU as an effective chemotherapeutic agent against various cancers, including colorectal, breast, and head and neck cancers.3,4

The topical use of 5-FU was first described in 1962 concerning the resolution of actinic keratosis (AK) in a patient who received systemic 5-FU.5 By 1963, patients with extensive AK were successfully treated with a hydrophilic ointment of 20% 5-FU for 4 weeks.6 Additional concentrations were evaluated in a follow-up study that indicated the comparable clearance capacity between 5% and 20% 5-FU creams.7 Since then, 5-FU has become a mainstay treatment for AK and has extended its clinical application to superficial basal cell carcinoma (sBCC), squamous cell carcinoma in situ (SCCis), actinic cheilitis, and keratoacanthomas. Studies have shown 5-FU as ...

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