Fluorouracil: adverse event reports filed with FDA

60,451

reports as suspect product

0.3% of all reports · about 2,687 a year

5,315

reports, 12 months to June 2026

4,983 in the 12 months before

96.1%

marked serious by the reporter

92.2% across the class

13.6%

record death among outcomes, as reported

8,230 reports · not verified by FDA

Reports by month, five years

Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

By year received

2026 covers reports received through June 2026 only.

Reactions recorded in the reports

share of Fluorouracil reports recording the termmedian drug in nucleoside metabolic inhibitor

1. Diarrhoealoose or frequent stools9.9%5,985
2. Neutropenialow neutrophils, a type of white blood cell7.9%4,761
3. Nauseafeeling sick6.8%4,130
4. Vomitingbeing sick5.6%3,362
5. Neuropathy peripheralnerve damage in hands or feet4.6%2,778
6. Febrile neutropeniafever with low white blood cells4.4%2,683
7. Disease progressionthe disease advanced4.4%2,642
8. Off label useused for a purpose or in a way not on the label4.3%2,619
9. Fatiguetiredness4.3%2,605
10. Thrombocytopenialow platelets4.2%2,547
11. Pyrexiafever4.1%2,464
12. Anaemialow red blood cells3.6%2,197
13. Astheniaweakness or lack of energy3.5%2,112
14. Drug ineffectivethe medicine did not work as expected3%1,803
15. Decreased appetitereduced appetite2.8%1,670
16. Mucosal inflammation2.8%1,667
17. Malignant neoplasm progression2.7%1,643
18. Abdominal painstomach or belly pain2.6%1,570
19. Dehydrationdehydration2.4%1,479
20. Leukopenialow white blood cells2.4%1,456
21. Dyspnoeashortness of breath2.2%1,360
22. Stomatitissore mouth2.2%1,336
23. General physical health deteriorationgeneral decline in health2.1%1,267
24. Deaththe patient died; cause not stated by this term2.1%1,244
25. Sepsisa severe body-wide response to infection2%1,224
26. Pulmonary embolisma blood clot in the lung1.9%1,170
27. Myelosuppression1.8%1,101
28. Rashskin rash1.7%1,046
29. Pneumonialung infection1.7%1,011
30. Acute kidney injurysudden loss of kidney function1.6%963

Top 30 of 3,368 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 19 drugs in the nucleoside metabolic inhibitor class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Outcomes recorded

Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 313,386 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."

Patients and reporters

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 21.2% of reports give the United States as the country of the event or reporter.

Reason for use recorded

The indication field is filled in by the reporter and is often blank; shares are of all 60,451 reports.

Drugs most often listed in the same reports

Other products listed in reports where Fluorouracil is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.

In context

Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Other drugs in the nucleoside metabolic inhibitor class

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Fluorouracil as a suspect or interacting product; reports listing it only as a concomitant medication (17,246) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.