Total and free salicylate concentrations in juvenile rheumatoid arthritis.

Salicylates are known to be highly protein bound, primarily to albumin. Patients with juvenile rheumatoid arthritis (JRA) are known to have decreased albumin concentrations. Total and free salicylate concentrations were determined for 19 patients with JRA. Although many of these patients were below the normal therapeutic range, the percent of salicylate bound was essentially constant and did not differ significantly regardless of albumin concentrations or total salicylate concentrations. Elevated liver enzymes did not correlate with total or free salicylate concentrations. We conclude that total salicylate concentrations should be used for monitoring aspirin therapy in JRA. Free salicylate concentrations do not appear to be more reliable or feasible.