Plasma protein binding of prednisolone in normal volunteers and arthritic patients

Abstract

The plasma binding of prednisolone was studied in twenty normal volunteers and twenty rheumatoid arthritis patients. An in vitro assessment of the binding following the addition of prednisolone, prednisone, and hydrocortisone to the plasmas obtained from the subjects showed significant differences in the percentage of prednisolone bound. However, the differences observed were regarded as clinically insignificant. The plasma protein binding was determined by an in vitro equilibrium dialysis of the individual plasma samples at 37° C. Prednisolone levels on both sides of the dialysis membrane were determined using radioactivity and HPLC analytical methodologies. The percentages of prednisolone bound calculated from the analytical results of either the radiochemical or HPLC method were not significantly different. The change in the percentage of prednisolone bound to plasma proteins was studied as a function of the total prednisolone plasma concentration in a normal volunteer and in a systemic lupus erythematosis patient. As a result of prednisolone binding to both transcortin and albumin, the binding of prednisolone changes as a function of prednisolone concentration. The binding data were fitted using nonlinear least squares regression, and the affinity constants for the binding of prednisolone to transcortin and albumin were estimated.