Drugs › Pyrimidine synthesis inhibitor
Generic name
Teriflunomide: adverse event reports filed with FDA
4,984 reports list it as a suspect or interacting product, 2013–2026. Class: Pyrimidine synthesis inhibitor.
- 4,984
- reports as suspect product
- 0% of all reports · about 372 a year
- 334
- reports, 12 months to June 2026
- 387 in the 12 months before
- 68.4%
- marked serious by the reporter
- 43.7% across the class
- 2.6%
- record death among outcomes, as reported
- 131 reports · not verified by FDA
4,984 adverse event reports received by FDA list teriflunomide, a generic name as a suspect or interacting product, from February 2013 to June 2026. A further 297 reports list it only as a concomitant medication, and those are not counted in the figures on this page.
In the 12 months to June 2026, 334 reports listed it, down 14% from 387 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 372 reports a year and 0% of the 20,646,523 reports in the database, and 11.9% of the reports for the pyrimidine synthesis inhibitor class. How many people take it is not in the data, so a count is not a rate of occurrence.
The MedDRA terms listed most often are alopecia (16.5%), fatigue (16.5%) and diarrhoea (15.3%). A report can list several reactions, so shares add to more than 100%; 1,102 different terms appear across these reports. Alopecia is recorded in 16.5% of these reports, about the same share as in the median pyrimidine synthesis inhibitor drug (15.2%).
68.4% of the reports are marked serious by the reporter (43.7% across the class); 2.6% record death among the outcomes and 27.3% record hospitalisation, as reported. 59% of the reports came from consumers, and the largest patient age group is 45 to 64 (47.3%). 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 Teriflunomide reports recording the termmedian drug in pyrimidine synthesis inhibitor
- Alopeciahair loss16.5%824
- Fatiguetiredness16.5%820
- Diarrhoealoose or frequent stools15.3%761
- Multiple sclerosis relapsea flare of multiple sclerosis12.7%632
- Hypoaesthesianumbness11.9%593
- Falla fall11.1%553
- Headachehead pain10.8%539
- Condition aggravatedthe condition being treated got worse10.8%538
- Paraesthesiatingling or pins and needles10.1%502
- Gait disturbancedifficulty walking9.9%495
- Memory impairmentmemory problems9.5%474
- Nauseafeeling sick9.4%470
- Painpain, site not specified9%449
- Astheniaweakness or lack of energy7%349
- Coughcough7%348
- Multiple sclerosis7%348
- Balance disorderproblems with balance6.9%342
- Pain in extremitypain in an arm or leg6.9%342
- Product dose omissiona dose was missed6.5%324
- Dizzinesslight-headedness or unsteadiness6.1%306
- Depressionlow mood6%298
- Drug ineffectivethe medicine did not work as expected5.4%268
- Feeling abnormalfeeling odd or not right5%249
- Muscular weaknessmuscle weakness4.9%244
- Back painback pain4.7%234
- Malaisegeneral feeling of being unwell4.7%233
- Unevaluable eventthe event could not be assessed4.6%229
- Weight decreasedweight loss4.5%222
- Muscle spasmsmuscle cramps4.4%220
- Visual impairmentreduced vision4.2%211
Top 30 of 1,102 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 pyrimidine synthesis 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 41,974 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. 71.9% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Multiple sclerosis | 3,079 | 61.8% |
| Relapsing-remitting multiple sclerosis | 480 | 9.6% |
| Multiple sclerosis relapse | 164 | 3.3% |
| Relapsing multiple sclerosis | 59 | 1.2% |
| Secondary progressive multiple sclerosis | 12 | 0.2% |
| Foetal exposure during pregnancy | 5 | 0.1% |
The indication field is filled in by the reporter and is often blank; shares are of all 4,984 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Teriflunomide reports |
|---|---|---|
| Ergocalciferol | 330 | 6.6% |
| Gabapentin | 326 | 6.5% |
| Baclofen | 301 | 6% |
| Vitamin d | 189 | 3.8% |
| Ampyra | 181 | 3.6% |
| Lisinopril | 134 | 2.7% |
| Omeprazole | 133 | 2.7% |
| Amlodipine | 126 | 2.5% |
| Calcium | 102 | 2% |
| Atorvastatin | 100 | 2% |
Other products listed in reports where Teriflunomide 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 | Teriflunomide | Pyrimidine synthesis inhibitor | All reports |
|---|---|---|---|
| Reports as suspect product | 4,984 | 41,974 | 20,646,523 |
| Share of that pool | — | 11.9% | 0% |
| Reports, latest 12 months | 334 | — | 1,332,454 |
| Marked serious | 68.4% | 43.7% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 26 | 16 | 91 |
| Hospitalisation recorded, per 1,000 reports | 273 | 138 | 213 |
| Consumer-filed share | 59% | 57.3% | 45.8% |
| Top term, share of reports | Alopecia 16.5% | median 15.2% | 0.9% |
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 pyrimidine synthesis inhibitor class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Aubagio | brand | 36,990 | 161 | 40.4% |
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 Teriflunomide reports
How many adverse event reports has FDA received for Teriflunomide?
4,984 reports list Teriflunomide as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 334 of them arrived in the latest 12 months. Another 297 list it only as a concomitant medication.
What reactions are recorded in Teriflunomide reports?
alopecia (16.5%), fatigue (16.5%), diarrhoea (15.3%), multiple sclerosis relapse (12.7%) and hypoaesthesia (11.9%). 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 Teriflunomide was responsible.
How serious are the reports?
68.4% are marked serious by the reporter. Among the outcomes recorded, 2.6% of reports include death and 27.3% 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?
consumer or non-health professional (59%), physician (22.6%) and other health professional (13%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Teriflunomide rising?
334 reports in the 12 months to June 2026, down 14% from 387 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 Teriflunomide 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 Teriflunomide?
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 Teriflunomide as a suspect or interacting product; reports listing it only as a concomitant medication (297) 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.