Protein binding of salicylate in uremic and normal plasma.

Protein binding of salicylate was studied by equilibrium dialysis at 37 degrees C in plasma from uremic patients and healthy subjects. The protein binding was considerably lower in the uremic plasma at all salicylate concentrations studied (14 to 1,400 mug/ml). Scatchard plots of the data were computer-analyzed assuming binding to the classes of binding sites. According to this analysis, the binding to the class of primary binding sites was considerably decreased in the uremic plasma. In addition to the effect of the uremic state, the binding was considerably decreased at high therapeutic plasma levels and at low albumin levels. The combined effect of two or three of these factors may lead to unexpectedly high unbound fractions of salicylate, which should be considered in the monitoring of plasma salicylate levels in patients.