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Biotransformation of fluticasone: in vitro characterization.
Robin E Pearce, J Steven Leeder, Gregory L Kearns
Drug metabolism and disposition: the biological fate of chemicals 2006 Jun
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Fluticasone propionate (FTP) is a synthetic trifluorinated glucocorticoid with potent anti-inflammatory action that is commonly used in patients with asthma. After oral or intranasal administration, FTP undergoes rapid hepatic biotransformation; the principal metabolite formed is a 17beta-carboxylic acid derivative (M1). M1 formation has been attributed largely to cytochrome P450 3A4 (CYP3A4); however, there are no published data that confirm this assertion. Hence, in vitro studies were conducted to determine the role that human P450s play in the metabolism of FTP. Consistent with in vivo data, human liver microsomes catalyzed the formation of a single metabolite (M1) at substrate concentrations plasma Cmax = 1 nM). Under these conditions, the kinetics of M1 formation in human liver microsomes were consistent with those of a single enzyme (Km congruent with 5 microM). Formation of M1 correlated significantly (r > 0.95) with CYP3A4/5 activities in a panel of human liver microsomes (n = 14) and was markedly impaired by the CYP3A inhibitor ketoconazole (>94%) but not by inhibitors of other P450 enzymes (enzymes revealed that M1 formation was catalyzed primarily by CYP3A enzymes at FTP concentrations P450s 3A4, 3A5, and 3A7; in vitro intrinsic clearance values (Vmax/Km) were comparable for all three CYP3A enzymes. These results suggest that at pharmacologically relevant concentrations, biotransformation of FTP to M1 is mediated predominantly by CYP3A enzymes in the liver.
Citation
Robin E Pearce, J Steven Leeder, Gregory L Kearns.
Biotransformation of fluticasone: in vitro characterization.
Drug metabolism and disposition: the biological fate of chemicals.
2006 Jun;34(6):1035-40
Mesh Tags
Androstadienes
Anti-Inflammatory Agents
Biotransformation
Cytochrome P-450 CYP3A
Cytochrome P-450 Enzyme Inhibitors
Cytochrome P-450 Enzyme System
Dose-Response Relationship, Drug
Enzyme Inhibitors
Fluticasone
Humans
In Vitro Techniques
Ketoconazole
Kinetics
Lung
Microsomes, Liver
Mifepristone
Recombinant Proteins
Substances
Androstadienes
Anti-Inflammatory Agents
Cytochrome P-450 Enzyme Inhibitors
Enzyme Inhibitors
Recombinant Proteins
Mifepristone
Cytochrome P-450 Enzyme System
Fluticasone
CYP3A5 protein, human
Cytochrome P-450 CYP3A
CYP3A4 protein, human
Ketoconazole
PMID: 16565171
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