PT  - JOURNAL ARTICLE
AU  - A. Miller-Larsson
AU  - H. Mattsson
AU  - E. Hjertberg
AU  - M. Dahlbäck
AU  - A. Tunek
AU  - R. Brattsand
TI  - Reversible Fatty Acid Conjugation of Budesonide
DP  - 1998 Jul 01
TA  - Drug Metabolism and Disposition
PG  - 623--630
VI  - 26
IP  - 7
4099  - http://dmd.aspetjournals.org/content/26/7/623.short
4100  - http://dmd.aspetjournals.org/content/26/7/623.full
SO  - Drug Metab Dispos1998 Jul 01; 26
AB  - A high airway concentration might be required for the antiasthmatic efficacy of inhaled glucocorticosteroids (GCS). The topical uptake and retention of GCS in airway tissue were compared for GCS of the inhaled type [budesonide (BUD), fluticasone propionate (FP), and beclomethasone dipropionate (BDP)] and of the noninhaled type (dexamethasone and hydrocortisone). 3H-labeled GCS solutions were administered into rat airways by either perfusion of trachea in vivo, intratracheal instillation, or inhalation. Radioactivity was determined in the airway tissue, lung parenchyma, and plasma 20 min to 24 hr after exposure. Ethanol extracts of exposed tracheas were analyzed by HPLC. Exposed tracheas were also incubatedin vitro in buffer, and the released radioactivity was analyzed by HPLC. BUD, FP, and BDP were equally well taken up into the airway tissue; their uptake was 25–130 times greater than that of dexamethasone and hydrocortisone. BUD was shown to form very lipophilic intracellular fatty acid esters (at carbon 21) in the airway and lung tissue after topical application. In large airways 20 min after administration, approximately 70–80% of retained BUD was conjugated. BUD stored in esterified form in the tissue was retained in large airways for a prolonged time, compared with FP and BDP, which do not form such conjugates. The fatty acid conjugation of BUD is reversiblein vivo; BUD conjugates are gradually hydrolyzed and free BUD is regenerated. This reversible conjugation may improve airway selectivity, as well as prolong the local anti-inflammatory action of BUD in the airways and might be one explanation for why BUD is efficacious in the treatment of mild asthma when inhaled once daily. The American Society for Pharmacology and Experimental Therapeutics