From the Guidelines
Fluorouracil (5-fluorouracil) works by inhibiting thymidylate synthetase, which is necessary for DNA synthesis, and may also interfere with RNA formation and function.
Mechanism of Action
- The mechanism of action of fluorouracil is based on the inhibition of thymidylate synthetase, an enzyme essential for DNA synthesis 1.
- This inhibition prevents the proliferation of abnormal cells, such as those found in actinic keratosis.
- Additionally, fluorouracil may interfere with the formation and function of RNA, further contributing to its therapeutic effects 1.
Clinical Applications
- Fluorouracil is commonly used as a topical treatment for actinic keratosis, with a 5% concentration being the most widely studied and used 1.
- It can be used as lesional treatment or as part of field treatment, although the latter may be associated with more substantial side effects, such as soreness, redness, and crusting 1.
- To minimize side effects, the frequency of application can be reduced or short breaks can be taken during a course of therapy, and patients can be advised to wash the area and apply a thin emollient 1.
From the FDA Drug Label
When Fluorouracil Cream USP is applied to a lesion, a response occurs with the following sequence: erythema, usually followed by vesiculation, desquamation, erosion, and re-epithelialization. The mechanism of action of fluorouracil (5-fluorouracil) on the skin is not explicitly stated in the provided drug label. However, it can be inferred that fluorouracil works by inducing a sequence of skin reactions, including:
- Erythema (redness)
- Vesiculation (blistering)
- Desquamation (shedding of skin)
- Erosion (wearing away of skin)
- Re-epithelialization (regrowth of skin) 2 This sequence of reactions suggests that fluorouracil may be causing cell death and tissue damage in the affected area, leading to the elimination of abnormal cells and ultimately, the healing of the lesion.
From the Research
Mechanism of Action of Fluorouracil on the Skin
The mechanism of action of fluorouracil (5-fluorouracil) on the skin is not fully understood, but several studies have investigated its effects on various dermatological conditions.
- The drug is an analogue of the naturally occurring pyrimidine uracil and is metabolized via the same metabolic pathways as uracil 3.
- Topical 5-fluorouracil has been used for the treatment of a range of cancers and dermatological conditions, including actinic keratosis, benign tumors, nail psoriasis, mycosis fungoides, and porokeratoses 4, 5.
- The drug has been shown to have therapeutic efficacy in the treatment of many other dermatological conditions, including squamous cell carcinoma in situ, warts, psoriasis of the nail, keratoacanthoma, and vitiligo 5.
- Recent findings have also demonstrated a role for 5-fluorouracil in the treatment of photoaging 4 and other noncancerous cutaneous indications, such as scarring, pigmentary disorders, cutaneous infections, inflammatory dermatoses, and cosmetic indications 6.
Dermatological Implications
The dermatological implications of 5-fluorouracil treatment include:
- Systemic absorption, which can occur with topical application 4.
- Selectivity for abnormal skin, which allows the drug to target affected areas 4.
- Targeted delivery, which can enhance the efficacy of the treatment 4.
- Skin-specific molecular effects, which can contribute to the drug's therapeutic effects 4.
Clinical Applications
The clinical applications of topical 5-fluorouracil include:
- Treatment of actinic keratosis and superficial basal cell carcinoma, which are approved indications by the US Food and Drug Administration 5.
- Treatment of other dermatological conditions, such as squamous cell carcinoma in situ, warts, psoriasis of the nail, keratoacanthoma, and vitiligo 5.
- Off-label uses, such as treatment of scarring, pigmentary disorders, cutaneous infections, inflammatory dermatoses, and cosmetic indications 6.