Pharmacodynamic modeling of cortisol suppression from fluocortolone.

The effect of fluocortolone on cortisol suppression was characterized using a 'direct suppression pharmacodynamic model'. The model incorporates the physiologic circadian secretion of cortisol under normal and treatment conditions, together with pharmacokinetic data from single fluocortolone doses of 20, 50, and 100 mg. A mean IC50 value (fluocortolone plasma concentration at which the circadian secretion of cortisol is inhibited by 50%) of 15.5 ng.ml-1 was found. This analysis shows how use of pharmacodynamic modeling can characterize dose-proportionality data to provide an in vivo measure of drug potency.