85/100 · Critical
Manufactured by sanofi-aventis U.S. LLC
Leflunomide Adverse Events: High Serious Reaction Rate
696,911 FDA adverse event reports analyzed
Last updated: 2026-05-12
LEFLUNOMIDE is a medication tracked in the FDA Adverse Event Reporting System (FAERS), manufactured by sanofi-aventis U.S. LLC. Based on analysis of 696,911 FDA adverse event reports, LEFLUNOMIDE has a safety score of 85 out of 100. This score indicates a relatively favorable safety profile, with fewer or less severe adverse events compared to many other tracked medications. The most commonly reported adverse reactions for LEFLUNOMIDE include DRUG INEFFECTIVE, RHEUMATOID ARTHRITIS, PAIN, ARTHRALGIA, DRUG INTOLERANCE. This page provides a comprehensive breakdown of reported side effects, safety signals, patient demographics, and AI-powered safety analysis for LEFLUNOMIDE.
Leflunomide has a safety concern score of 85 out of 100, placing it in the high concern category based on analysis of FDA adverse event data. The FDA has received approximately 696,911 adverse event reports for this medication, which is primarily manufactured by Sanofi-Aventis U.S. Llc.
The most commonly reported adverse events include Drug Ineffective, Rheumatoid Arthritis, Pain. Of classified reports, 82.4% were designated as serious by the FDA, meaning they involved hospitalization, disability, or other significant medical outcomes. High percentage of serious adverse events (82.4%) indicates significant safety concerns.
A wide range of reactions reported, including liver injury and infections. Fatigue, rash, and joint swelling are among the most common side effects.
Patients taking Leflunomide should monitor for the commonly reported side effects and contact their healthcare provider if they experience any unusual symptoms. Leflunomide can cause serious liver injury and infections; patients should be monitored closely, especially for signs of liver dysfunction and infections. This analysis is based on voluntary FDA adverse event reports and should not replace professional medical advice.
Leflunomide received a safety concern score of 85/100 (high concern). This is based on a 82.4% serious event ratio across 102,084 classified reports. The score accounts for 696,911 total adverse event reports and 100 distinct reaction types. This high score reflects a significant proportion of serious adverse events in the reporting data.
Adverse event reports by sex: Female: 74,654, Male: 16,527, Unknown: 141. The most frequently reported age groups are age 43 (3,062 reports), age 44 (2,860 reports), age 60 (2,216 reports). These demographics reflect reporting patterns and may not represent the full patient population.
Out of 102,084 classified reports for LEFLUNOMIDE:
The FDA classifies an adverse event as “serious” if it results in death, hospitalization, disability, congenital anomaly, or requires intervention to prevent permanent damage.
Demographics reflect voluntary FDA adverse event reporting patterns and may not represent the full patient population.
Leflunomide can cause serious liver injury and infections; patients should be monitored closely, especially for signs of liver dysfunction and infections.
If you are taking Leflunomide, here are important things to know. The most commonly reported side effects include drug ineffective, rheumatoid arthritis, pain, arthralgia, drug intolerance. While many of these may be mild and temporary, you should contact your healthcare provider if any symptoms are severe or persistent. Patients should report any signs of liver dysfunction, such as yellowing of the skin or eyes, to their healthcare provider immediately. Follow all dosing instructions and do not exceed the prescribed dose. If you experience a serious adverse reaction, seek emergency medical attention immediately or call 911. You can report side effects to the FDA's MedWatch program at 1-800-FDA-1088.
The FDA continues to monitor the safety of leflunomide and has not issued any new warnings or changes to the drug label based on this data.
The FDA has received approximately 696,911 adverse event reports associated with Leflunomide. These reports come from healthcare professionals, consumers, and manufacturers through the FDA Adverse Event Reporting System (FAERS). Note that the number of reports does not directly indicate the frequency of side effects, as adverse events are voluntarily reported and may be underrepresented.
The most frequently reported adverse events for Leflunomide include Drug Ineffective, Rheumatoid Arthritis, Pain, Arthralgia, Drug Intolerance. By volume, the top reported reactions are: Drug Ineffective (36,982 reports), Rheumatoid Arthritis (24,922 reports), Pain (20,054 reports). These figures reflect FDA adverse event reports and may not represent the true incidence rate of these side effects in all patients taking Leflunomide.
Out of 102,084 classified reports, 84,075 (82.4%) were classified as serious and 18,009 as non-serious. The FDA classifies an event as "serious" if it results in death, hospitalization, disability, or other medically significant outcomes. A higher serious-event ratio warrants closer attention but does not necessarily mean the drug is unsafe.
Adverse event reports for Leflunomide break down by patient sex as follows: Female: 74,654, Male: 16,527, Unknown: 141. This distribution reflects reporting patterns rather than actual risk differences between groups. Reporting rates can be influenced by prescribing patterns, disease demographics, and reporting behavior.
The most frequently reported age groups for Leflunomide adverse events are: age 43: 3,062 reports, age 44: 2,860 reports, age 60: 2,216 reports, age 59: 2,209 reports, age 63: 1,834 reports. Age-related reporting patterns can reflect both the demographics of the patient population and potential age-related susceptibility to certain side effects.
The primary manufacturer associated with Leflunomide adverse event reports is Sanofi-Aventis U.S. Llc. Multiple manufacturers may produce generic versions of this drug. The manufacturer listed reflects the most frequently reported brand in FDA adverse event data.
Beyond the most common reactions, other reported adverse events for Leflunomide include: Joint Swelling, Fatigue, Rash, Off Label Use, Abdominal Discomfort. Less common side effects can still be clinically significant. Patients should report any unusual symptoms to their healthcare provider.
You can report adverse events from Leflunomide to the FDA through their MedWatch program at www.fda.gov/medwatch, by calling 1-800-FDA-1088, or by completing Form FDA 3500. Healthcare professionals, consumers, and manufacturers can all submit reports. Reporting helps the FDA monitor drug safety after approval.
Leflunomide has a safety concern score of 85 out of 100 (high concern). This score is calculated from the ratio of serious to non-serious adverse events, the diversity of reported reactions, and the overall volume of reports relative to usage. High percentage of serious adverse events (82.4%) indicates significant safety concerns.
Key safety signals identified in Leflunomide's adverse event data include: Liver injury reported in a significant number of cases.. Infections, particularly respiratory and gastrointestinal, are common.. High incidence of musculoskeletal pain and joint swelling.. These signals are derived from patterns in FDA reports and should be discussed with a healthcare provider for personalized assessment.
Leflunomide can cause serious liver injury and infections; patients should be monitored closely, especially for signs of liver dysfunction and infections. Always inform your healthcare provider about all medications, supplements, and over-the-counter drugs you are taking before starting Leflunomide.
Patients should report any signs of liver dysfunction, such as yellowing of the skin or eyes, to their healthcare provider immediately. Follow all dosing instructions and do not exceed the prescribed dose.
Leflunomide has 696,911 adverse event reports on file with the FDA. A wide range of reactions reported, including liver injury and infections. The volume of reports for Leflunomide reflects both the drug's usage level and the vigilance of the reporting community.
The FDA continues to monitor the safety of leflunomide and has not issued any new warnings or changes to the drug label based on this data. For the most current regulatory information, check the FDA's drug labeling database or consult your pharmacist.
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