leflunomide
Brand names: Arava
Leflunomide is a drug that can help reduce the symptoms of rheumatoid arthritis. It works by slowing down the body's immune system.
Drug Pricing (NADAC)
Generic Price
$0.31/unit
Generic Available
Yes (8 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Leflunomide treats active rheumatoid arthritis in adults.
Common side effects
Diarrhea, Respiratory infection, Nausea
Key warnings
This drug can cause serious harm to an unborn baby.
How It Works
Leflunomide is a pyrimidine synthesis inhibitor. This means it blocks a certain process in your body. By blocking this process, it can reduce inflammation and slow down the damage to your joints.
How to Take It
You can take leflunomide with or without food. The usual dose is 20 mg once a day. Sometimes, your doctor may start you on a higher dose of 100 mg for the first 3 days. If you have side effects, your doctor may lower your dose to 10 mg daily.
Pregnancy & Breastfeeding
Do not take leflunomide if you are pregnant. It can cause birth defects. If you are breastfeeding, you should stop while taking this medicine.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and take your next dose at the regular time.
Storage
Store at room temperature, away from light.
Side Effects (from patient reports)
Based on 182,288 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 102,095 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
102,095
Death-Related Reports
8,456
Hospitalization Reports
27,652
Top Indication
Rheumatoid Arthritis
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DRUG INEFFECTIVE | 36,983 |
| 2 | RHEUMATOID ARTHRITIS | 24,923 |
| 3 | PAIN | 20,055 |
| 4 | ARTHRALGIA | 16,941 |
| 5 | DRUG INTOLERANCE | 15,586 |
| 6 | JOINT SWELLING | 15,567 |
| 7 | FATIGUE | 15,384 |
| 8 | RASH | 13,321 |
| 9 | OFF LABEL USE | 11,798 |
| 10 | ABDOMINAL DISCOMFORT | 11,731 |
| 11 | ALOPECIA | 11,692 |
| 12 | CONTRAINDICATED PRODUCT ADMINISTERED | 11,637 |
| 13 | ARTHROPATHY | 10,791 |
| 14 | CONDITION AGGRAVATED | 10,367 |
| 15 | SWELLING | 10,250 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
This drug can cause serious harm to an unborn baby. If you are pregnant or could become pregnant, you should not take this medicine. This drug can also cause serious liver problems. If you have liver problems, you should not take this medicine. Your doctor will monitor your liver with blood tests.
Known Drug Interactions
For other substrates of BCRP (e.g., mitoxantrone) and drugs in the OATP family (e.g., methotrexate, rifampin), especially HMG-Co reductase inhibitors (e.g., atorvastatin, nateglinide, pravastatin, repaglinide, and simvastatin), consider reducing the dose of these drugs and monitor patients closely for signs and symptoms of increased exposures to the drugs while patients are taking leflunomide [see Clinical Pharmacology (12.3) ].
Mechanism: Leflunomide can interfere with how your body moves and clears atorvastatin, potentially leading to higher levels of the drug in your blood.
What to do: Your doctor may need to lower your dose of atorvastatin and monitor you for signs of drug toxicity.
For a patient taking leflunomide, the dose of rosuvastatin should not exceed 10 mg once daily. ( 7 ) Rosuvastatin: The dose of rosuvastatin should not exceed 10 mg once daily in patients taking leflunomide.
Mechanism: Leflunomide changes how your body processes rosuvastatin, which can cause the amount of the cholesterol medicine in your blood to increase.
What to do: If you are taking leflunomide, your daily dose of rosuvastatin should not be more than 10 mg.
For other substrates of BCRP (e.g., mitoxantrone) and drugs in the OATP family (e.g., methotrexate, rifampin), especially HMG-Co reductase inhibitors (e.g., atorvastatin, nateglinide, pravastatin, repaglinide, and simvastatin), consider reducing the dose of these drugs and monitor patients closely for signs and symptoms of increased exposures to the drugs while patients are taking leflunomide [see Clinical Pharmacology (12.3) ].
Mechanism: Leflunomide can block the proteins that help your body get rid of simvastatin, which may cause the drug to reach higher levels than normal.
What to do: Your doctor may consider lowering your simvastatin dose and should monitor you closely for any side effects.
In patients taking leflunomide, exposure of drugs which are OAT3 substrates (e.g., cefaclor, cimetidine, ciprofloxacin, penicillin G, ketoprofen, furosemide, methotrexate, zidovudine) may be increased.
Mechanism: Leflunomide interferes with a protein that helps the body remove furosemide, which can cause the levels of furosemide in your blood to rise.
What to do: Your doctor may need to monitor you more closely for side effects or adjust your dose of furosemide.
In patients taking leflunomide, exposure of drugs metabolized by CYP1A2 (e.g., alosetron, duloxetine, theophylline, tizanidine) may be reduced.
Mechanism: Leflunomide speeds up how fast your body breaks down duloxetine, which can lower the amount of medicine in your system and make it less effective.
What to do: Your doctor may need to check if your duloxetine is still working well and might adjust your dose.
Common Questions
What should I do before starting leflunomide?
How long does it take for leflunomide to work?
Can I take other medicines with leflunomide?
What if I want to get pregnant while taking leflunomide?
How often will my liver be checked?
What are the signs of liver problems?
What if I get an infection?
Can leflunomide affect my blood pressure?
What happens if I need surgery?
What do the tablets look like?
What are the common side effects of leflunomide?
Does leflunomide interact with other medications?
What drug class is leflunomide?
Is leflunomide safe during pregnancy?
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Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for leflunomide
The FDA label for leflunomide (sold under brand names such as Arava) classifies it as a prescription-only medication in the Disease-Modifying Antirheumatic Drug (DMARD) class. Leflunomide treats active rheumatoid arthritis in adults. Official labeling lists 7 commonly reported side effects, including Diarrhea, Respiratory infection, Nausea.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 182,288 voluntary reports. The database also lists 20 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $0.31.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: December 17, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages