This updated Q&A notes that there remains no definitive answer regarding the optimal dose of folic acid for patients with rheumatoid arthritis who are being treated with methotrexate. It is generally agreed that folic acid supplementation reduces the toxicity of methotrexate without significantly affecting efficacy; and there seems to be a consensus of opinion that folic acid supplementation should be avoided on the day of methotrexate in case it adversely affects absorption. Folic acid supplementation should be continued for the duration of methotrexate therapy because adverse effects can occur at any time. The most commonly recommended dose regimens are 5mg folic acid taken the day after the methotrexate dose or 1mg folic acid daily except on the day of methotrexate. The British Society for Rheumatology recommends that patients on methotrexate are co-prescribed a minimum dose of 5mg folic acid once weekly.
Author: Diane Bramley, Senior Pharmacist Medicines Information, Guy’s and St Thomas’ NHS Foundation Trust