The metabolism of celecoxib is mediated mainly by the cytochrome P450 isoenzyme CYP2C9. Concomitant administration of other drugs that inhibit or are metabolized by this isoenzyme may result in changes in plasma concentrations of celecoxib. Co-administration of fluconazole has resulted in increased plasma concentration of celecoxib. Celecoxib is an inhibitor of the isoenzyme CYP2D6 therefore, individuals with reduced CYP2D6 activity may exhibit potential CYP2D6-associated drug-drug interactions.