Prescription medication · Disease-Modifying Antirheumatic Drug (DMARD)
leflunomide
Also sold as Arava. Leflunomide treats active rheumatoid arthritis in adults.
Data updated 2026-05-15
- 102,095
- FDA reportsOften reported
- 20
- InteractionsSeveral interactions
- $0.31
- Generic price (NADAC)
What the data shows
leflunomide (Arava) is a prescription Disease-Modifying Antirheumatic Drug (DMARD), more reported than most tracked drugs (102,095 FDA reports), with 20 documented drug interactions.
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
leflunomide (Arava) is a prescription Disease-Modifying Antirheumatic Drug (DMARD). Leflunomide treats active rheumatoid arthritis in adults.
Leflunomide is a drug that can help reduce the symptoms of rheumatoid arthritis. It works by slowing down the body's immune system.
Verify with FDA → · CMS NADAC pricing →
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.
The sections below are summarized in plain English from leflunomide's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
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.
This is a plain-language summary of leflunomide's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
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.
This is a plain-language summary of leflunomide's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
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.
This is a plain-language summary of leflunomide's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store at room temperature, away from light.
Side Effects (from patient reports)
Based on 102,095 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for leflunomide, by number of reports
- Rheumatoid arthritis
Rheumatoid arthritis
24,921 reports
- Pain
Pain
20,055 reports
- Joint pain
Joint pain
16,943 reports
- Swollen joint
Swollen joint
15,567 reports
- Tiredness
Tiredness
15,384 reports
- Rash
Rash
13,321 reports
- Stomach discomfort
Stomach discomfort
11,731 reports
- Hair loss
Hair loss
11,692 reports
- Given a medicine that should not have been given
Given a medicine that should not have been given
11,637 reports
- Joint disease
Joint disease
10,791 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for leflunomide each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where leflunomide sits
leflunomide has more FDA adverse-event reports than 85% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is leflunomide; the line is the median (50th percentile).
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
Reports Mentioning Death
8,456
8.3% of reports — not proof of cause
Hospitalization Reports
27,652
Top Indication
Rheumatoid Arthritis
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 2 | RHEUMATOID ARTHRITIS | 24,923 |
| 3 | PAIN | 20,055 |
| 4 | ARTHRALGIA | 16,941 |
| 6 | JOINT SWELLING | 15,567 |
| 7 | FATIGUE | 15,384 |
| 8 | RASH | 13,321 |
| 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 |
| 16 | NAUSEA | 10,126 |
| 17 | SYNOVITIS | 10,026 |
| 18 | SYSTEMIC LUPUS ERYTHEMATOSUS | 9,625 |
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.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
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 102,095 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.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
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