Folic acid and cyanocobalamin levels in serum and erythrocytes during low-dose methotrexate therapy of rheumatoid arthritis and psoriatic arthritis patients.

Abstract

The degree of folate depletion during MTX therapy depends primarily upon the weekly administered dose. Folate depletion may be related to B12 deficiency in RBC. Since FA levels were not related to parameters of disease activity it is conceivable that MTX does not exert its action in RA primarily by inhibiting dihydrofolatereductase. Therefore, additional folate compounds, if necessary, should not lead to a reduction in the efficacy of MTX.