Teriflunomide must not be used during pregnancy because it may cause serious harm (such as birth defects, death) in an unborn baby. Women of childbearing age must have a negative pregnancy test before starting this medication. Men and women must use reliable forms of birth control (such as condoms, birth control pills) while taking teriflunomide and for as long as directed by your doctor to prevent pregnancy. After stopping treatment with teriflunomide, your doctor may prescribe a different drug to help speed up the removal of teriflunomide from your body. If you become pregnant or think you may be pregnant or cause a pregnancy, tell your doctor right away. (See also How to Use and Precautions sections.) This drug may rarely cause serious (possibly fatal) liver disease. Careful monitoring by your doctor may help decrease your risk. Your doctor will perform liver function tests before you start treatment and once a month for at least the first 6 months of treatment. Tell your doctor right away if you notice nausea/vomiting that doesn't stop, dark urine, loss of appetite, stomach/abdominal pain, or yellowing eyes/skin.

Diarrhea, nausea, or tingling/burning/numbness/prickling feelings in your skin may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. Temporary hair loss may occur. Normal hair growth should return after treatment has ended. Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: easy bruising/bleeding, new/worsening shortness of breath, new/worsening numbness/tingling of hands/feet, pain in your side (flank pain), symptoms of high potassium blood levels (such as muscle weakness, slow/irregular heartbeat), unusual tiredness. This medication may raise your blood pressure. Check your blood pressure regularly and tell your doctor if the results are high. This medication may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Get medical help right away if you have any signs of infection (such as sore throat that doesn't go away, fever, chills, cough, swollen lymph nodes). Teriflunomide can cause a mild rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe allergic reaction. Get medical help right away if you develop any rash. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

This medication can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include ketorolac, tovorafenib, among others. This medication can speed up the removal of other medications from your body, which may affect how they work. Examples of affected drugs include vorasidenib, among others. Because leflunomide (used to treat rheumatoid arthritis) is very similar to this medication, do not take it while you are taking teriflunomide.