RT Journal Article SR Electronic T1 Liver metabolism of budesonide in rat, mouse, and man. Comparative aspects. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 403 OP 411 VO 15 IS 3 A1 S Edsbäcker A1 P Andersson A1 C Lindberg A1 J Paulson A1 A Ryrfeldt A1 A Thalén YR 1987 UL http://dmd.aspetjournals.org/content/15/3/403.abstract AB The metabolism of budesonide, (22RS)-16 alpha, 17 alpha-butylidenedioxy-11 beta,21-dihydroxypregna-1,4-diene- 3,20-dione, was studied in the 9000g supernatant fraction of livers from rat, mouse, and man. The two budesonide C-22 epimers produced different metabolites. This was explained by substrate-selective oxidation of the nonsymmetric 16 alpha, 17 alpha-acetal substituent. Epimer 22R gave 16 alpha-hydroxyprednisolone, while epimer 22S produced a metabolite tentatively identified as 23-hydroxybudesonide. Otherwise, budesonide followed the general metabolic pathways reported for synthetic glucocorticoids. Thus, oxidative metabolism predominated, 6 beta-hydroxybudesonide and delta 6-budesonide being identified in all investigated species. Reductive metabolism, giving 4,5 beta-dihydrobudesonide and 3,4,5 beta-tetrahydrobudesonide, was most pronounced in the rat. Rates and routes of budesonide metabolism were most similar in mouse and human livers. This implies that the mouse is a more relevant species than the rat in studies of the pharmacology and toxicology of budesonide.