Before taking leflunomide, tell your doctor or pharmacist if you are allergic to it; or to teriflunomide; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: immune system disorder (such as HIV infection), current/recent infection (such as tuberculosis), cancer, bone marrow/blood disorder, kidney disease, liver disease (such as hepatitis B or C), alcohol abuse, heart disease (such as heart failure), high blood pressure, lung disease.

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis). Alcohol may also cause liver disease.

Do not have immunizations/vaccinations without the consent of your doctor, and avoid contact with people who have recently received oral polio vaccine or flu vaccine inhaled through the nose.

Leflunomide can make you more likely to get infections or may make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to your doctor if you have been exposed to an infection or for more details.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

This medication must not be used during pregnancy. It may harm an unborn baby. Women of childbearing age must have a negative pregnancy test before starting this medication. Women using this medication should ask about reliable forms of birth control during treatment and for some time after the last dose. Men using this medication and their female partners should ask about reliable forms of birth control during treatment. If you or your partner becomes pregnant or may be pregnant, tell your doctor right away. (See also Warning section.)

It is not known whether this medication affects the sperm. To minimize any possible risk, the manufacturer recommends that men wishing to father a child should stop the medication and use another drug (cholestyramine) as directed to help this drug leave the body before attempting to father a child. (See How to Use section.) Consult your doctor for more details.

This drug may pass into breast milk and could have undesirable effects on a nursing infant. Breastfeeding is not recommended while using this drug. Consult your doctor before breastfeeding.