SELECTIVE INHIBITION OF HUMAN CYTOCHROME P4502C8 BY MONTELUKAST

• Published in: Drug metabolism and disposition Vol. 33; no. 3; pp. 413 - 418
• Main Authors: WALSKY, Robert L, OBACH, R. Scott, GAMAN, Emily A, GLEESON, Jean-Paul R, PROCTOR, William R
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Pharmacology and Experimental Therapeutics 01.03.2005
• Subjects: Acetates - pharmacology; Amodiaquine - pharmacology; Anti-Asthmatic Agents - pharmacology; Aryl Hydrocarbon Hydroxylases - antagonists & inhibitors; Aryl Hydrocarbon Hydroxylases - metabolism; Biological and medical sciences; Cytochrome P-450 CYP2C8; Drug Interactions; Enzyme Inhibitors - pharmacology; Humans; In Vitro Techniques; Leukotriene Antagonists - pharmacology; Medical sciences; Microsomes, Liver - enzymology; Paclitaxel - pharmacology; Pharmacology. Drug treatments; Quinolines - pharmacology; Recombinant Proteins - metabolism; Thiazolidinediones - pharmacology; Human; Leukotriene receptor; Arachidonic acid derivatives; Eicosanoid; Montelukast; Leukotriene antagonist; Leukotriene D4; Leukotriene E4; Inhibition; Antiasthma agent
• ISSN: 0090-9556; 1521-009X
• DOI: 10.1124/dmd.104.002766

The leukotriene receptor antagonist montelukast was examined for its inhibition of the human drug-metabolizing enzyme cytochrome P4502C8 (CYP2C8). Montelukast was demonstrated to be a potent inhibitor of CYP2C8-catalyzed amodiaquine N -deethylase, rosiglitazone N -demethylase, and paclitaxel 6α-hydroxylase in human liver microsomes. Inhibition was also observed when the reaction was catalyzed by recombinant heterologously expressed CYP2C8. The mechanism of inhibition was competitive, with K i values ranging from 0.0092 to 0.15 μM. Inhibition potency was highly dependent on the microsomal protein concentration. Increasing the microsomal protein concentration by 80-fold yielded a 100-fold decrease in inhibition potency. Preincubation of montelukast with human liver microsomes and NADPH did not alter the inhibition potency, suggesting that montelukast is not a mechanism-based inactivator. Montelukast was a selective inhibitor for human CYP2C8; inhibition of other human cytochrome P450 enzymes was substantially less. These in vitro data support the use of montelukast as a selective CYP2C8 inhibitor that could be used to determine the contribution of this enzyme to drug metabolism reactions. These data also raise the possibility that montelukast could have an effect on the metabolic clearance of drugs possessing CYP2C8-catalyzed metabolism as a major clearance pathway, thereby eliciting pharmacokinetic drug-drug interactions.