Plasma reactive nitrogen intermediate levels in patients with clinically active rheumatoid arthritis.

We studied reactive nitrogen intermediate levels in 31 patients with active rheumatoid arthritis (RA) taking indomethacin and 20 healthy controls using nitrite and citrulline levels, measured by spectrophotometry, as markers. Twenty patients with RA were followed up after 4 and 8 wk of treatment with additional therapy in the form of methotrexate. Mean nitrite levels in 31 patients were 0.94 +/- 0.41 mumol/ml and 20 controls it was 1.18 +/- 0.99. After treatment with methotrexate for 4 and 8 wk the levels were 0.9 +/- 0.45 and 1.25 +/- 1.15 mumol/ml, respectively. Mean citrulline levels in all patients was 1.68 +/- 0.11 and controls was 1.39 +/- 0.6 mumol/ml. Following therapy with methotrexate for 4 and 8 wk the levels were 1.40 +/- 0.49 and 1.40 +/- 0.51 mumol/ml, respectively. It is possible that serum levels of these products may not reflect alterations in the synovial fluid levels. Alternatively, whatever lowering may have been achieved by the anti-inflammatory effect of the therapy may have been countered by drug derived free radicals.