Displaying 3 results of Leflunomide Stable Isotopes Leflunomide is a medication used for the treatment of rheumatoid arthritis. Leflunomide stable isotopes refer to the isotopes of the elements found in the molecule of leflunomide that do not decay over time. These isotopes are useful for research and development of new drugs as they allow for more accurate analysis of the effects of the drug on the body.