Effect of folic or folinic acid supplementation on the toxicity and efficacy of methotrexate in rheumatoid arthritis - A forty-eight-week, multicenter, randomized, double-blind, placebo-controlled study

Objective. To study the effect of folates on discontinuation of methotrexat e (MTX) as single-drug antirheumatic treatment due to toxicity, to determin e which type of adverse events are reduced, to study the effects on the eff icacy of MTX, and to compare folic with folinic acid supplementation in a 4 8-week, randomized, double-blind, placebo-controlled trial. Methods. Patients with active RA (n = 434) were randomly assigned to receiv e MTX plus either placebo, folic acid (1 mg/day), or folinic acid (2.5 mg/w eek). The initial MTX dosage was 7.5 mg/week; dosage increases,were allowed up to a maximum of 25 mg/week for insufficient responses. Folate dosages w ere doubled once the dosage of MTX reached 15 mg/week. The primary end poin t was MTX withdrawal because of adverse events. Secondary end points were t he MTX dosage and parameters of efficacy and toxicity of MTX. Results. Toxicity-related discontinuation of MTX occurred in 38% of the pla cebo group, 17% of the folic acid group, and 12% of the folinic acid group. These between-group differences were explained by a decreased incidence of elevated liver enzyme levels in the folate supplementation groups. No betw een-group differences were found in the frequency of other adverse events o r in the duration of adverse events. Parameters of disease activity improve d equally in all groups. Mean dosages of MTX at the end of the study were l ower in the placebo group (14.5 mg/week) than in the folic and folinic acid groups (18.0 and 16.4 mg/week, respectively). Conclusion. Both folate supplementation regimens reduced the incidence of e levated liver enzyme levels during MTX therapy, and as a consequence, MTX w as discontinued less frequently in these patients. Folates seem to have no effect on the incidence, severity, and duration of other adverse events, in cluding gastrointestinal and mucosal side effects. Slightly higher dosages of MTX were prescribed to obtain similar improvement in disease activity in the folate supplementation groups.