PT  - JOURNAL ARTICLE
AU  - Tunek, Anders
AU  - Sjödin, Karin
AU  - Hallström, Gösta
TI  - Reversible Formation of Fatty Acid Esters of Budesonide, an Antiasthma Glucocorticoid, in Human Lung and Liver Microsomes
DP  - 1997 Nov 01
TA  - Drug Metabolism and Disposition
PG  - 1311--1317
VI  - 25
IP  - 11
4099  - http://dmd.aspetjournals.org/content/25/11/1311.short
4100  - http://dmd.aspetjournals.org/content/25/11/1311.full
SO  - Drug Metab Dispos1997 Nov 01; 25
AB  - Microsomes from human lung and liver catalyze the formation of fatty acid esters of budesonide, a glucocorticoid used for inhalation treatment of asthma. The conjugation was dependent on coenzyme A and ATP. Addition of free fatty acids to the incubations affected the pattern of metabolites, but ester formation was observed also without such addition. Budesonide oleate, palmitate, linoleate, palmitoleate, and arachidonate were identified as metabolites. The fatty acid conjugates of budesonide were shown to be substrates for lipasein vitro, thus budesonide is regainable from the conjugates. The data suggest that an equilibrium between budesonide and these pharmacologically inactive lipoidal conjugates will be established in tissues at repeated exposure to budesonide. Since the fatty acid conjugates most likely will be retained intracellularly for a longer time than unchanged budesonide, the duration of tissue exposure to budesonide will depend partly on the rate of lipase-catalyzed hydrolysis of the conjugates. The findings in this study provide a possible explanation for the efficacy of budesonide in mild asthmatics also when inhaled once daily. The American Society for Pharmacology and Experimental Therapeutics