Neopred Mechanism of Action

Pharmacology: Pharmacokinetics: Prednisolone and prednisone are both readily absorbed from the gastrointestinal tract. Whereas prednisolone already exists in metabolically active form, prednisone must be converted in the liver to its active metabolite, prednisolone. In general, this conversion is rapid so that prednisone has a preconversion biological half-life (t_½) of only about 60 min. Hence, although prednisone has been estimated to have only 80% the bioavailability of prednisolone, this difference is of little consequence when seen in the light of intersubject variation in the pharmacokinetics of prednisolone itlself; bioavailability also depends on the dissolution rates of the tablet formulations. Nevertheless, prednisolone is the more reliably absorbed of the two corticosteroids, particularly in some liver diseases where the conversion of prednisone may be diminished.
Peak plasma concentrations of prednisolone are obtained 1-2 hrs after administration by mouth and it has a usual plasma t_½ of 2-4 hrs. Its initial absorption, but not its overall bioavailability, is affected by food.
Prednisolone is extensively bound to plasma proteins, although less so than hydrocortisone (cortisol).
Prednisone is excreted in the urine as free and conjugated metabolites, together with an appreciable proportion of unchanged prednisolone. Prednisolone is largely inactivated as it crosses the placenta; small amounts are excreted in breast milk.
Prednisolone has a biological t_½ lasting several hours, intermediate between those of hydrocortisone (cortisol) and the longer-acting glucocorticoids eg, dexamethasone. It is this intermediate duration of action that makes it suitable for the alternate-day dosage regimens which have been found to reduce the risk of adrenocortical insufficiency, yet provide adequate corticosteroid coverage in some disorders.