[Leflunomide: clinical effectiveness and mechanism of action].

Leflunomide is a new immunomodulatory agent by selectively inhibiting the de novo pyrimidine synthesis. Its active metabolite (A77 1726) is highly bound to plasma protein and has a long half life. Through several large trials describing its efficacy and safety including retardation of radiographic progression in comparison with both sulfasalazine and methotrexate and with placebo have been published in Europe and the United States, leflunomide was shown to improve primary and secondary outcome measures with satisfactory safety profile. The most common treatment-related adverse reactions were diarrhea, nausea, and abnormal plasma liver enzyme levels. Leflunomide may be a useful addition to the current management of rheumatoid arthritis.