Simultaneous salicylate concentrations in synovial fluid and plasma in rheumatoid arthritis

Abstract

Abstract Total, free (diffusible) and proteinbound salicylate concentrations were determined in synovial fluid samples obtained from 12 patients with rheumatoid arthritis, and compared with simultaneously obtained plasma concentrations. Free salicylate concentrations were essentially identical in the two fluids, implying complete equilibrium. Both the total and protein‐bound salicylate concentrations were consistently lower in the synovial fluids than in the corresponding plasmas; this difference may be explained by the lower albumin concentration in the joint fluid.