title: Kinetics of the epimeric glucocorticoid budesonide.
abstract: Budesonide is a potent nonhalogenated glucocorticoid consisting of a 1/1 mixture of the two epimers 22R and 22S. The kinetics of these epimers were studied in six healthy male subjects after intravenous administration of 500 micrograms 3H-budesonide. Estimation of the epimer concentrations in plasma was made possible by development of an HPLC method for simultaneous separation and quantification. The plasma t 1/2, distribution volume (V beta), and plasma clearance for epimer 22R were (mean +/- SD) 2.66 +/- 0.57 hr, 425 +/- 100 l, and 117 +/- 40 l/hr. The corresponding values for epimer 22S were 2.71 +/- 0.69 hr, 245 +/- 38 l, and 67 +/- 19 l/hr. Differences in V beta and plasma clearance between the two were significant. The larger V beta noted for epimer 22R may be a result of higher tissue affinity. The high plasma clearance for both epimers should largely reflect their high rate of liver biotransformation.
mesh_terms: D000328:Adult; D001711:Biotransformation; D001772:Blood Cell Count; D019819:Budesonide; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007263:Infusions, Parenteral; D007536:Isomerism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D011282:Pregnenediones / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014316:Tritium
chemical_list: D011282:Pregnenediones; D014316:Tritium; D019819:Budesonide; D006854:Hydrocortisone