This page presents data from the FDA Adverse Event Reporting System (FAERS) and the FDA-approved drug label. A report submitted to FAERS does not prove a drug caused the reported event. Always consult a healthcare provider about medications.

Fluorouracil

nucleoside metabolic inhibitor

Last updated: June 20, 2026

Preview tracking

Fluorouracil is a medication, a nucleoside metabolic inhibitor. According to the FDA-approved label, Fluorouracil Cream is recommended for the topical treatment of multiple actinic or solar keratoses. In the 5% strength, it is also useful in the treatment of superficial basal cell carcinomas when conventional methods are impractical, such as with multiple lesions or difficult tr. FAERS contains 75,123 submissions naming this drug from 2004 through 2026; the top three reactions cited are diarrhoea, neutropenia, and nausea.

Most-Reported Reactions

Counts of the reactions most often cited in FAERS submissions that named Fluorouracil. Inclusion here does not establish causation - submitters describe what was observed, not what was confirmed. One submission can list several reactions, so the totals exceed the report count.

Patient Demographics

Patient sex and age across the FAERS submissions that named Fluorouracil. Percentages here are computed only from submissions where these fields were filled in - many leave them blank.

By Sex

By Age Group

Severity Outcomes

Severity flags recorded across the 75,123 FAERS submissions that named Fluorouracil. Each bar shows the count of those reports carrying that flag. A single case can carry more than one (a hospitalization that became life-threatening, for example), so these bars are independent rates - they don't sum to 100%. Inclusion of a case under any flag does not establish that the drug caused the outcome.

Submissions Per Quarter

Quarterly count of FAERS submissions that named Fluorouracil. Ups and downs on this chart can track prescribing volume, news cycles, or shifts in how reports get filed, rather than the drug becoming safer or more dangerous.

From the FDA-Approved Label

Excerpts from the official FDA-approved prescribing information for Fluorouracil. This is the authoritative source on indications, warnings, and known adverse reactions.

Indications

Fluorouracil Cream is recommended for the topical treatment of multiple actinic or solar keratoses. In the 5% strength, it is also useful in the treatment of superficial basal cell carcinomas when conventional methods are impractical, such as with multiple lesions or difficult treatment sites. Safety and efficacy in other indications have not been established. The diagnosis should be established prior to treatment, since this method has not been proven effective in other types of basal cell carcinomas. With isolated, easily accessible basal cell carcinomas, surgery is preferred since success with such lesions is almost 100%. The success rate with Fluorouracil Cream is approximately 93%, based on 113 lesions in 54 patients. Eighty-eight lesions treated with the cream produced 7 failures.

Warnings

Application to mucous membranes should be avoided due to the possibility of local inflammation and ulceration. Additionally, cases of miscarriage and a birth defect (ventricular septal defect) have been reported when Fluorouracil Cream was applied to mucous membrane areas during pregnancy. Occlusion of the skin with resultant hydration has been shown to increase percutaneous penetration of several topical preparations. If any occlusive dressing is used in treatment of basal cell carcinoma, there may be an increase in the severity of inflammatory reactions in the adjacent normal skin. A porous gauze dressing may be applied for cosmetic reasons without increase in reaction. Exposure to ultraviolet rays should be minimized during and immediately following treatment with Fluorouracil Cream because the intensity of the reaction may be increased. Patients should discontinue therapy with Fluorouracil Cream if symptoms of DPD enzyme deficiency develop (see CONTRAINDICATIONS ). Rarely, life-threatening toxicities such as stomatitis, diarrhea, neutropenia, and neurotoxicity have been reported with intravenous administration of fluorouracil in patients with DPD enzyme deficiency. (continues in label)

Adverse Reactions (from label)

The most frequent adverse reactions to Fluorouracil Cream occur locally and are often related to an extension of the pharmacological activity of the drug. These include burning, crusting, allergic contact dermatitis, pruritus, scarring, rash, soreness, and ulceration. Ulcerations, other local reactions, cases of miscarriage, and a birth defect (ventricular septal defect) have been reported when Fluorouracil Cream was applied to mucous membrane areas. Leukocytosis is the most frequent hematological side effect. Although a causal relationship is remote, other adverse reactions which have been reported infrequently are: Central Nervous System: Emotional upset, insomnia, irritability. Gastrointestinal: Medicinal taste, stomatitis. Hematological: Eosinophilia, thrombocytopenia, toxic granulation. Integumentary: Alopecia, blistering, bullous pemphigoid, discomfort, ichthyosis, scaling, suppuration, swelling, telangiectasia, tenderness, urticaria, skin rash. Special Senses: Conjunctival reaction, corneal reaction, lacrimation, nasal irritation. Miscellaneous: Herpes simplex. To report SUSPECTED ADVERSE REACTIONS contact Mayne Pharma at 1-844-825-8500 or FDA at 1-800-FDA-1088 or www.FDA. (continues in label)

FDA label effective date: 2021-11-04

Disclaimer

AdverseEvent.ai is not affiliated with the FDA. Adverse-event counts come from the FDA Adverse Event Reporting System (FAERS). Drug labels come from the FDA drug label dataset. A report submitted to FAERS does not prove a drug caused the reported event — always consult a healthcare provider about medications. This site is for informational purposes only and is not medical advice.