[Efficacy of leflunomide].

Leflunomide(Arava) is a novel immunomodulatory drug, the primary action of which is inhibition of de-novo pyrimidine synthesis by selective inhibition of dihydro-orotate dehydrogenase. It has been shown that leflunomide is effective in treating active rheumatoid arthritis(RA) in a placebo-controlled phase II study. Subsequent multinational, randomized, controlled phase III clinical trials demonstrated that leflunomide is as effective and safe as methotrexate and sulfasalazine in treatment of RA. Frequently reported adverse effects included diarrhea, nausea and vomiting, skin rash, reversible alopecia, and transient lever enzyme elevations. However, accumulating concerns about its toxic effects, especially hepatotoxicity, have been raised recently. In addition, rheumatologists should be aware that leflunomide has a much longer half life than any other disease modifying antirheumatic drug.