Will pharmacogenetics allow better prediction of methotrexate toxicity and efficacy in patients with rheumatoid arthritis?

Methotrexate (MTX) remains the most commonly used disease modifying antirheumatic drug in rheumatoid arthritis (RA) because of its cost and experience in its use, despite the availability of new treatments such as leflunomide and the biological agents. However, a significant number of patients with RA either do not benefit from the drug or are unable to tolerate it. Pharmacogenetic approaches may help optimise treatment with MTX, and also other agents, in RA.