Methotrexate--the relationship between dose and clinical effect.

Methotrexate (MTX) is an effective anti-rheumatic drug. Despite its frequent use, the relationship between different MTX doses and clinical effects remain unclear. In a randomized double-blind study in patients with RA, the effects of four MTX doses (5 to 20 mg) was studied. MTX (5 mg) induced a significant effect on the Ritchie joint index, morning stiffness, pain, ESR and C-reactive protein. The effect of MTX on those variables was related to the dose in the range from 5 to 20 mg MTX weekly. Interindividual differences in dose-response curves were observed. The study shows that MTX doses should be adjusted individually for each patient in order to improve efficacy and decrease dose-dependent side effects.