Usefulness of daily folic acid supplementation during methotrexate treatment of Japanese patients with rheumatoid arthritis

Objectives: We investigated the effect of daily folic acid supplementation on methotrexate (MTX) toxicity and efficacy in Japanese patients with rheumatoid arthritis (RA). Methods: We followed 19 patients treated with MTX who switched from taking weekly 5 mg folic acid supplementation (weekly regimen) to 1.25 mg daily (daily regimen). White blood cell (WBC) and platelet (PLT) counts, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels were collected for 24 weeks following the change. Results: We observed no significant changes in WBC or PLT counts. AST and ALT levels, which had exceeded the upper limits of their normal ranges at the beginning of the study, were improved significantly at weeks 4 and 8, no subsequent deterioration in liver function was found. Further, no significant changes in ESR and CRP levels were observed. Conclusion: Our data indicate that supplementing 1.25 mg of folic acid daily rather than 5 mg weekly reduces toxicity caused by MTX without affecting its efficacy.