Methotrexate versus leflunomide in rheumatoid arthritis: what is new in 2011?

To review the recent efficacy and safety data comparing methotrexate (MTX) and leflunomide (LEF) monotherapy, in combination with biologic therapies and in combination with each other. MTX is the 'anchor drug' in all rheumatoid arthritis treatment strategies. Patients with contraindications to or intolerance of this drug pose a challenge to the treating physician. Recent studies have re-examined LEF as an alternative to MTX and demonstrated comparable clinical and radiographic efficacy both as monotherapy and in combination with certain biologic agents (tumor necrosis factor inhibitors and rituximab). Safety data, however, are less conclusive. Though some studies have shown greater withdrawal rates with LEF, the incidence of infection and elevated transaminases have been comparable. There are few new data examining the previously demonstrated added benefit of combination MTX+LEF over either alone. The safety profile of this combination, however, has been re-examined in several studies, with conflicting results. Although two meta-analyses and two small retrospective studies have demonstrated a safety profile similar to that of MTX monotherapy, data from a large population study suggested a greater degree of hepatotoxicity with combination. LEF offers an alternative with comparable efficacy to MTX as both monotherapy and, as preliminary data suggest, in combination with certain biologics agents. Addition of LEF to MTX in rheumatoid arthritis patients who have failed MTX monotherapy has added therapeutic benefit. Safety data on LEF compared to MTX are less conclusive. All patients on LEF, and particularly those on combined LEF+MTX, should be monitored closely for hepatotoxicity.