Leflunomide belongs to the class of medications called immunomodulators. It is used to treat some of the symptoms associated with rheumatoid arthritis, such as inflammation, swelling, stiffness, and joint pain. It works by blocking the body's ability to produce the immune cells that cause these problems.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended starting dose of leflunomide is 100 mg once daily for the first 3 days, followed by 20 mg once a day.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

Leflunomide may be taken with or without food, but it should be taken at the same time every day with a full glass of water or other fluid.

This medication should be taken on a regular basis for it to work effectively. It may take up to a month to see any benefit, and 4 to 6 months to get the maximum benefit of this medication.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, away from direct light and moisture. Keep it out of the reach of children.

Do not take this medication if you:

• are allergic to leflunomide, teriflunomide, or any ingredients of the medication
• are pregnant or may become pregnant, unless you use reliable contraception before, during, and for a period of 2 years after treatment with leflunomide
• are breast-feeding
• are under 18 years old
• have an immunodeficiency due to causes other than rheumatoid arthritis (e.g., AIDS, transplant recipients taking medications that suppress the immune system)
• have an impaired bone marrow function or other blood disorders due to causes other than rheumatoid arthritis
• have extremely low levels of protein in the blood
• have impaired liver function
• have moderate-to-severe kidney function impairment
• have severe infections

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• dizziness
• dry skin
• hair loss
• headache
• itching of the skin
• loss of appetite
• mild diarrhea
• nausea
• sensation of tingling skin
• stomach pain
• unexplained weight loss
• vomiting
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• fast or pounding heartbeat
• fever
• increased blood pressure
• mouth sores
• nausea or vomiting
• severe diarrhea with or without blood in the stool
• severe stomach pain
• signs of bleeding (e.g., bloody nose, blood in urine or stools, coughing blood, cuts that don't stop bleeding, unusual bleeding or bruising, black, tarry stools)
• signs of decreased red blood cells (anemia; e.g., pale skin, fatigue, shortness of breath, rapid heartbeat)
• signs of infection (e.g., cough, fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• tendon pain or swelling
• swelling of feet or lower legs
• unusual tiredness or weakness
• vision changes
• worsening arthritis symptoms (e.g., joint pain or stiffness)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of a severe skin reaction (e.g., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)
• signs of serious breathing problems (interstitial lung disease; e.g., new or worsening shortness of breath with or without fever; new or worsening cough with or without fever, difficult or painful breathing, chest congestion)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Alcohol: The liver helps to break down leflunomide into chemicals that are active in the body. Alcohol is also broken down by the liver. The combination of leflunomide and alcohol may result in more harm to the liver than if either one were used on its own. To reduce the risk of severe liver injury, you should avoid alcohol during treatment with leflunomide.

Birth defects: Leflunomide can cause birth defects in children whose fathers were using it at the time of conception. For this reason, a man planning a family must first stop taking the medication and consult with his doctor. Otherwise, he should use condoms during sexual intercourse.

If either partner is taking leflunomide, a reliable method of birth control should always be used throughout the course of treatment with leflunomide. Women should avoid pregnancy, and men should avoid fathering a child for 2 years after taking leflunomide (or for as long as a certain level of the medication and its byproducts remain in the body).

Blood clotting: This medication can reduce the number of platelet cells in the blood. Platelets help the blood to clot, and a shortage could make you bleed more easily. Tell your doctor of any signs that your blood is not clotting as quickly. Such symptoms may include black and tarry stools.

Blood pressure: Leflunomide frequently causes increased blood pressure. For this reason, it is important to monitor your blood pressure on a regular basis while taking this medication.

Infection: Leflunomide works on the immune system to help reduce the damage that parts of the immune system cause to the body. It can reduce the number of cells that fight infection in the body (white blood cells). As a result, leflunomide may reduce the body's ability to fight severe infections.

Tell your doctor immediately if you notice signs of an infection, such as fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness. Your doctor will do regular blood tests to monitor the number of specific types of blood cells in your blood.

Avoid immunizations without your doctor's approval.

Kidney function: The kidneys help to remove this medication from the body. When the kidneys are not working well, leflunomide can build up in the body and cause serious side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

This medication should not be used by anyone who has moderately to severely reduced kidney function.

Liver function: Leflunomide can cause damage to the liver, including liver failure, and should not be used by anyone who has reduced liver function or liver disease.

If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Lung inflammation: Lung inflammation (interstitial lung disease), causing difficulty breathing has occurred rarely in some people taking this medication. This complication can be serious and sometimes fatal. If you experience new or worsening shortness of breath or cough (with or without fever) at any time while you are taking leflunomide contact your doctor immediately.

Red blood cells: Leflunomide may cause low levels of red blood cells. If you experience symptoms of reduced red blood cell count (anemia) such as shortness of breath, feeling unusually tired, or pale skin, contact your doctor as soon as possible.

Pregnancy: This medication is likely to cause serious harm and birth defects to the unborn baby if it is taken by a pregnant mother. It is important that leflunomide is not used during pregnancy or by women who may become pregnant. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication may pass into breast milk. If you are a breast-feeding mother and are taking leflunomide it may affect your baby. Due to the seriousness of the effects that a breast-feeding infant would experience, women taking this medication should be advised not to breast-feed.

Children: The safety and effectiveness of leflunomide has not been established for children under the age of 18 years.

There may be an interaction between leflunomide and any of the following:

• activated charcoal
• alcohol
• amiodarone
• azathioprine
• BCG
• cancer chemotherapy (e.g., cisplatin, cytarabine, doxorubicin, nivolumab, paclitaxel, vincristine)
• cholestyraminecolesevelam
• colestipol
• corticosteroids (e.g., budesonide, hydrocortisone, prednisone)
• cyclosporine
• denosumab
• echinacea
• enzalutamide
• erlotinib
• fluoxetine
• other immunosuppressants (e.g., etanercept, fingolimod, hydroxychlorquine, infliximab, mycophenolate)
• imiquimod
• lenalidomide
• methotrexate
• natalizumab
• pimecrolimus
• pioglitazone
• repaglinide
• rifampin
• rituximab
• roflumilast
• romidepsin
• rosiglitazone
• tacrolimus
• teriflunomide
• tofacitinib
• trastuzumab
• tretinoin
• vaccines
• warfarin
• zopiclone

If you are taking any of these drugs, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.