Methotrexate: an old new drug in autoimmune disease.

Methotrexate (MTX) is currently considered, among disease-modifying anti-rheumatic drugs (DMARDs), the 'anchor-drug' in the treatment of rheumatoid arthritis. In the last 25 years, there has been a marked expansion in the use of MTX in different inflammatory diseases. Its low cost, associated to a good long-term efficacy and safety profile, justifies the use of MTX as a first-line disease-modifying drug or alternatively, a steroid-sparing medication in this field of medicine. Although new emerging options, including biological treatments, are being established in the therapeutic scenario, the good cost/benefit ratio of MTX supports the choice of this drug in combination with these newer therapies, enhancing the efficacy of these combination therapies and decreasing the risk of potential side effects.