[Methotrexate and folates in rheumatoid arthritis]

The efficacy of weekly low-dose methotrexate treatment of rheumatoid arthritis is well documented. Efficacy and adverse events are both dose dependent, and side effects rather than lack of response are the main reason for discontinuing therapy. Several adverse effects appear to be related to folate deficiencies, and are largely due to the antifolate properties of methotrexate. In order to diminish side effects without compromising drug efficacy, clinical trials have been performed using folic acid or folinic acid concomitantly with methotrexate. Important to this achievement are both the timing of folate supplementation and the weekly folate-to-methotrexate ratio. Considering these and other factors, an individually adjusted supply of folic acid is proposed. For several patients a properly balanced diet is sufficient; they do not need additional folate supplements when using methotrexate.