EFFECT OF METHOTREXATE ON VITAMIN B6 DEFICIENCY IN RHEUMATOID ARTHRITIS

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The purpose of this study is to determie the status of B vitamins in rheumatoid arthritis (RA) patients with or without methotrexate (MTX) treatment by methionine and tryptophan load tests, and by measuring vitamin B levels in the blood. Recently, we have found that patients with RA and low plasma PLP levels also have elevated homocysteine levels, both fasting and in response to an oral methionine challange, than do healthy subjects. Hyper-homocysteinemia is a newly recognized risk factor for stroke and coronary heart disease, and may be important in explaining the increased mortality rate of patients with RA. We hypothesize that PLP deficiency in RA causes disorders of PLP-dependent metabolic pathways. We hypothesize that MTX blocks the response to the methionine challenge test, but that PLP deficiency nonetheless exists in patients treated with MTX, and that this deficiency can be identified using a tryptophan challenge test. This study will: a. determine the response to methionine and tryptophan challenge in 20 patients with RA taking MTX, 20 patients not taking MTX, and 20 age-matched healthy controls; b. determine the effect of nonsteroidal anti-inflammatory medication on the tryptophan challenge test by re-testing the healthy control subjects after two weeks of treatment with naproxen; c. determine whether there is a level of plasma PLP which can reliably predict vitamin B6 deficiency in patients with RA; d. test the ability of 1 month of oral vitamin B6 therapy to normalize methionine and tryptophan challenge results in those patients with abnormal tests.