Generic name
Leflunomide: adverse event reports filed with FDA
36,993 reports list it as a suspect or interacting product, 2004–2026. Class: Antirheumatic agent. Also reported as Leflunomide Tablet, Leflunomide Tab 10mg, Leflunomide Tab 20mg.
- 36,993
- reports as suspect product
- 0.2% of all reports · about 1,645 a year
- 2,568
- reports, 12 months to June 2026
- 3,085 in the 12 months before
- 94.2%
- marked serious by the reporter
- 92.1% across the class
- 16.1%
- record death among outcomes, as reported
- 5,954 reports · not verified by FDA
Between January 2004 and June 2026, 36,993 adverse event reports received by FDA list leflunomide, a generic name as a suspect or interacting product. Reports that mention it only as a concomitant medication (27,520) are left out of every figure here.
In the 12 months to June 2026, 2,568 reports listed it, down 17% from 3,085 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 1,645 reports a year and 0.2% of the 20,646,523 reports in the database, and 52% of the reports for the antirheumatic agent class. How many people take it is not in the data, so a count is not a rate of occurrence.
The reactions recorded most often are drug ineffective (49.8%), rheumatoid arthritis (34.4%) and pain (27.3%). A report can list several reactions, so shares add to more than 100%; 2,654 different terms appear across these reports. Drug ineffective is recorded in 49.8% of these reports, about the same share as in the median antirheumatic agent drug (51.6%).
94.2% of the reports are marked serious by the reporter (92.1% across the class); 16.1% record death among the outcomes and 33.7% record hospitalisation, as reported. 54.1% of the reports came from other health professionals, and the largest patient age group is 45 to 64 (25.4%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
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 Leflunomide reports recording the termmedian drug in antirheumatic agent
- Drug ineffectivethe medicine did not work as expected49.8%18,437
- Rheumatoid arthritisrheumatoid arthritis, an inflammatory joint disease34.4%12,714
- Painpain, site not specified27.3%10,095
- Drug intolerancethe medicine was not tolerated26.5%9,821
- Joint swellinga swollen joint26.3%9,731
- Arthralgiajoint pain23.6%8,720
- Rashskin rash23.5%8,680
- Fatiguetiredness22.9%8,481
- Contraindicated product administered20.5%7,566
- Synovitis20.2%7,463
- Off label useused for a purpose or in a way not on the label20.1%7,429
- Arthropathy17.5%6,479
- Alopeciahair loss17.3%6,383
- Hypersensitivityan allergic-type reaction17.3%6,382
- Hepatic enzyme increasedraised liver enzymes17%6,299
- Swellingswelling17%6,283
- Abdominal discomfortstomach discomfort16.8%6,199
- Condition aggravatedthe condition being treated got worse16.7%6,161
- Treatment failurethe treatment did not work15.9%5,870
- Peripheral swellingswelling of the arms or legs15.7%5,811
- Systemic lupus erythematosuslupus, an autoimmune disease15.2%5,611
- Infusion related reactiona reaction during or soon after an infusion14.9%5,516
- Hand deformity14.9%5,511
- Therapeutic product effect decreased14.8%5,474
- Pemphigus14.5%5,354
- Drug hypersensitivityan allergic-type reaction to a medicine14.4%5,320
- Glossodynia14.4%5,311
- Nauseafeeling sick14.2%5,239
- Diarrhoealoose or frequent stools13.6%5,037
- Wound13.2%4,873
Top 30 of 2,654 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 2 drugs in the antirheumatic agent 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 71,196 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
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 10.3% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Rheumatoid arthritis | 16,400 | 44.3% |
| Psoriatic arthropathy | 703 | 1.9% |
| Systemic lupus erythematosus | 224 | 0.6% |
| Juvenile idiopathic arthritis | 186 | 0.5% |
| Immunosuppressant drug therapy | 168 | 0.5% |
| Arthritis | 161 | 0.4% |
The indication field is filled in by the reporter and is often blank; shares are of all 36,993 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Leflunomide reports |
|---|---|---|
| Methotrexate | 26,764 | 72.3% |
| Enbrel | 18,568 | 50.2% |
| Sulfasalazine | 17,118 | 46.3% |
| Humira | 16,850 | 45.5% |
| Orencia | 16,245 | 43.9% |
| Prednisone | 16,027 | 43.3% |
| Actemra | 15,100 | 40.8% |
| Rituximab | 13,078 | 35.4% |
| Xeljanz | 12,893 | 34.9% |
| Hydroxychloroquine | 12,727 | 34.4% |
Other products listed in reports where Leflunomide 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
| Measure | Leflunomide | Antirheumatic agent | All reports |
|---|---|---|---|
| Reports as suspect product | 36,993 | 71,196 | 20,646,523 |
| Share of that pool | — | 52% | 0.2% |
| Reports, latest 12 months | 2,568 | — | 1,332,454 |
| Marked serious | 94.2% | 92.1% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 161 | 143 | 91 |
| Hospitalisation recorded, per 1,000 reports | 337 | 308 | 213 |
| Consumer-filed share | 18.5% | 19.4% | 45.8% |
| Top term, share of reports | Drug ineffective 49.8% | median 51.6% | 6.3% |
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 antirheumatic agent class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Arava | brand | 34,203 | 1,424 | 89.8% |
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.
Questions about Leflunomide reports
How many adverse event reports has FDA received for Leflunomide?
36,993 reports list Leflunomide as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 2,568 of them arrived in the latest 12 months. Another 27,520 list it only as a concomitant medication.
What reactions are recorded in Leflunomide reports?
drug ineffective (49.8%), rheumatoid arthritis (34.4%), pain (27.3%), drug intolerance (26.5%) and joint swelling (26.3%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Leflunomide was responsible.
How serious are the reports?
94.2% are marked serious by the reporter. Among the outcomes recorded, 16.1% of reports include death and 33.7% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
other health professional (54.1%), physician (25.3%) and consumer or non-health professional (18.5%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Leflunomide rising?
2,568 reports in the 12 months to June 2026, down 17% from 3,085 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Leflunomide was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Leflunomide?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.
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 Leflunomide as a suspect or interacting product; reports listing it only as a concomitant medication (27,520) 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.
Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.