Improved Procedure for the Determination of Protein Binding by Conventional Equilibrium Dialysis

• Published in: Journal of pharmaceutical sciences 1983-08, Vol.72 (8), p.918-921
• Main Authors: Briggs, Colin J., Hubbard, John W., Savage, Catherine, Smith, Diane
• Format: Article
• Language: English
• Subjects: alpha -globulin; Blood Proteins - metabolism; correction for concentration-dependent binding; Dialysis - methods; drugs; elimination of artifactual error; equilibrium dialysis; equilibrium dialysis with multiple replicated controls; Equilibrium dialysis-measurement of low-level protein binding; Equilibrium dialysis—measurement of low-level protein binding, elimination of artifactual error, multiple replicated controls; Humans; multiple replicated controls; Pharmaceutical Preparations - blood; Protein Binding; Protein binding-low levels measured by equilibrium dialysis; Protein binding—low levels measured by equilibrium dialysis, use of multiple replicated controls to eliminate artifactual error, correction for concentration-dependent binding; sulfadimethoxine; Sulfadimethoxine - blood; Sulfadimethoxine-binding to CF-IV-1 α-globulin at therapeutic doses; Sulfadimethoxine—binding to CF-IV-1 α-globulin at therapeutic doses, equilibrium dialysis with multiple replicated controls; use of multiple replicated controls to eliminate artifactual error
• ISSN: 0022-3549; 1520-6017
• DOI: 10.1002/jps.2600720819

□ The binding of drugs to plasma proteins has been studied extensively using a variety of methods, including equilibrium dialysis. Published information on controls used in these studies is frequently inadequate; in other cases, there are deficiencies in the experimental design for the controls. A method is described that eliminates many of the problems associated with artifactual errors in dialysis studies. Multiple replicated controls are performed at the same time as the test, under identical conditions. The controls are used to correct for concentration- dependent binding of drug to the membrane or other equipment. The method was used to determine the binding of sulfadimethoxine to CF-IV-1α-globulin at therapeutic concentrations. The level of binding was low (9–13%), but the stringent control technique permitted statistical analysis which showed each mean test value to be significantly different from its corresponding control. Furthermore, there was a linear relationship between the control-corrected percentage binding values and total drug concentration, whereas there was no correlation between total drug concentration and the uncorrected percentage binding values.