Some of the most common side effects of leflunomide include:
muscle pain or weakness
pain, burning, numbness, or tingling in the hands or feet
This is not a complete list of adverse effects – though these are among the most common. Seek medical attention right away if you experience symptoms such as rash, fever, blisters or peeling of the skin, difficulty breathing, a new or worsening cough, chest pain, or pale skin while taking leflunomide.
As with all prescription medication, be sure to inform the prescribing doctor about any medical conditions you have been previously diagnosed with, as well as any medication/ supplements you are currently taking before starting treatment with leflunomide. Leflunomide can interact with other forms of medication and substances, causing potentially serious side effects.
Leflunamide carries a black box warning for severe liver damage, which means that the Food and Drug Administration (FDA) has qualified it as a high-risk drug. This means that patients with preexisting liver disease, patients who have elevated liver enzyme levels, or patients who have a history of heavy drinking shouldn't take the drug.
In addition, do not take leflunomide if you are pregnant or plan on becoming pregnant before starting treatment with this medication, as it may harm the fetus. You must use an effective method of birth control before, during, and for 2 years after leflunomide treatment.