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Leflunomide Side Effects

The most commonly reported side effects of leflunomide include rheumatoid arthritis, pain, and arthralgia, based on 104,480 FDA adverse event reports from 2004 to 2025. 36.6% of reports found the drug to be ineffective.

Leflunomide side effects

Percentages show how often each reaction appears relative to total reports for leflunomide.

1
Drug Ineffective36.6%38,216
2
Rheumatoid Arthritis24.1%25,227
3
Pain19.1%19,986
4
Arthralgia15.9%16,613
5
Drug Intolerance15.3%16,023
6
Joint Swelling15.1%15,743
7
Fatigue14.5%15,166
8
Rash12.6%13,192
9
Off Label Use11.4%11,937
10
Contraindicated Product Administered11.3%11,833
11
Abdominal Discomfort11.3%11,777
12
Alopecia11.2%11,684
13
Arthropathy10.4%10,871
14
Condition Aggravated9.9%10,353
15
Swelling9.8%10,273

These are voluntary reports and do not establish that leflunomide caused these reactions.

Report severity

82.7%Serious86,381 reports
27.0%Hospitalizations28,169 reports
8.1%Fatal8,491 reports

Seriousness is determined by the reporter, not by OpenClaim.

Leflunomide drug interactions

Other drugs that appear in adverse event reports alongside leflunomide. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Methotrexate47.6%49,749
2
Etanercept43.3%45,278
3
Adalimumab39.4%41,202
4
Hydroxychloroquine-sulfate31.1%32,519
5
Abatacept30.3%31,649
6
Tocilizumab28.8%30,055
7
Rituximab25.8%26,993
8
Infliximab23.8%24,892
9
Sulfasalazine23.0%24,053
10
Certolizumab-pegol18.1%18,915
11
Golimumab17.5%18,279
12
Prednisone16.6%17,340
13
Tofacitinib15.7%16,418
14
Folic-acid11.8%12,365
15
Alendronate-sodium11.4%11,934

Taken alongside

1
Prednisone20.6%21,494
2
Hydroxychloroquine-sulfate13.2%13,779
3
Methotrexate13.0%13,550
4
Acetaminophen12.8%13,388
5
Tofacitinib11.3%11,833
6
Sulfasalazine10.1%10,543
7
Folic-acid9.7%10,086
8
Pantoprazole-sodium8.3%8,699
9
Ergocalciferol8.3%8,693
10
Ibuprofen7.7%8,033
11
Levothyroxine-sodium6.0%6,253
12
Naproxen5.3%5,493
13
Omeprazole4.9%5,094
14
Diclofenac4.8%5,047
15
Calcium4.8%5,030

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports leflunomide side effects

73.1% of leflunomide adverse event reports involve female patients and 16.3% involve male patients. The largest age group is adult at 72%. These figures reflect who reports side effects, not underlying risk.

Sex

Female73.1%
Male16.3%
Unknown10.6%

Age group

< 20.4%
2–110.4%
12–170.7%
18–6471.7%
65+26.8%

What is leflunomide used for

Conditions and purposes for which patients were taking leflunomide when the adverse event was reported.

Abdominal DiscomfortAbdominal LymphadenopathyAccidental Drug Intake By ChildAccidental Exposure To ProductAcute Febrile Neutrophilic DermatosisAdjuvant TherapyAdrenal InsufficiencyAlanine Aminotransferase IncreasedAlopeciaAlveolitis AllergicAnalgesic TherapyAngiolymphoid Hyperplasia With EosinophiliaAnkylosing SpondylitisAnti-cyclic Citrullinated Peptide AntibodyAnti-cyclic Citrullinated Peptide Antibody Positive

Showing 15 of 574 indications

Leflunomide brand names and reporting trend

Leflunomide is sold under the brand name Arava.

Brand names

Arava106,371

Quarterly reports (20042025)

20052010201520202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking leflunomide with another medication?

Ask OpenClaim about your specific drug combination. Get a sourced report using FDA data, drug labels, and medical literature.