Binding of prednisolone to α₁-acid glycoprotein

The binding of prednisolone to α₁-acid glycoprotein (AGP) was determined in vitro by equilibrium dialysis. The effects of temperature, protein concentration, and drug concentration were evaluated. The binding ratio (bound/free) correlated well with protein concentration (r = 0.958) and percent bound ranged from 2 to 12% over high to low prednisolone concentrations at physiologic AGP concentrations (100 mg/dl). Temperature changes did not perturb binding. The non-linear regression estimate of the binding constant (nk) was 4.4 × 10³ M^-1 indicative of both low affinity and low capacity of AGP for prednisolone. Overall, contribution of AGP to the total plasma binding of prednisolone is less than 3% when considered in the competitive protein binding system with transcortin and albumin. Disease induced alterations of AGP concentrations are relatively unimportant regarding plasma protein binding of prednisolone.