THURSDAY, Oct. 20 (HealthDay News) -- Rheumatoid arthritis patients who take folic acid may reduce the efficacy of their methotrexate treatment by 10% to 20%, according to a report in the October issue of Arthritis & Rheumatism.
Folic acid is frequently used to prevent the side effects of methotrexate, however, the effect on methotrexate efficacy is unknown. Dinesh Khanna, M.D., M.Sc., of the University of Cincinnati, and colleagues performed a post hoc analysis of two randomized controlled studies -- one in Europe and one in the United States -- where methotrexate was used as a comparator to leflunomide. Folic acid is prescribed prophylactically in the United States, while Europeans tend to use it only as needed.
Folic acid use was 98% in the U.S. study while only 10% in the multinational European study. After combining the data from two studies, the authors found a 9% to 21% reduction in American College of Rheumatology 20%, 50% or 70% improvement criteria at 52 weeks for folic acid users compared with non-users. Folic acid users also had less frequent abnormal liver function tests.
"The results of this data analysis should be considered 'hypothesis generating' and an impetus for future studies regarding the effects of folic acid on the efficacy of [methotrexate in rheumatoid arthritis]," the authors conclude.
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