Exacerbation of rheumatoid arthritis in patients treated with methotrexate after administration of folinic acid.

A double blind, placebo controlled trial examined the effects of folinic acid on the efficacy and toxicity of methotrexate in 27 patients with rheumatoid arthritis. Clinical and laboratory indices of disease activity worsened significantly in the 13 patients treated with folinic acid after four weeks of treatment, but not in the 14 patients treated with placebo. Exacerbation of rheumatoid arthritis led to withdrawal of the test drug in seven of the patients treated with folinic acid but in none of those treated with placebo. It is concluded that excerbation of rheumatoid arthritis is likely when folinic acid is given shortly after the weekly dose of methotrexate.