Prednisone ADME

Prednisone and prednisolone are considered to be fully therapeutically equivalent. The theoretical advantage of avoiding high GI concentrations of prednisone by administering prednisolone directly has never been shown to be clinically relevant.

Only 2–5% of a given dose of prednisone is excreted unchanged in urine. After hydrogenation to prednisolone at least 20 metabolites and their conjugates are formed and excreted. The main metabolites both after systemic and topical use are 20alpha- and 20beta-dihydro-prednisone, as well as 20alpha- and 20beta-dihydro-prednisolone (20AH-PREDN, 20BH-PREDN, 20AH-PREDL, 20BH-PREDL), in addition to the 6beta-hydroxy compounds 6B-OH-PREDN and 6B-OH-PREDL.

Hydrogenation of PREDN and dehydrogenation of PREDL are complementary reactions that are dominant in different cell types. While liver and fat cells convert PREDN to PREDL, colon and kidney cells partly convert PREDL back to PREDN. We have depicted this equilibrium by showing example reactions in hepatocytes and kidney cells in the diagram.