The metabolism of celecoxib is mediated mainly by the cytochrome P450 is isoenzyme CYP2C9. Concomitant administration of other drugs that inhibit or are metabolised by this isoenzyme may result in changes in the plasma concentration of celecoxib; co-administration of fluconazole has resulted in increased in plasma concentration of celecoxib. Celecoxib is an inhibitor of the isoenzyme CYP2D6 and the potential therefore exist for an effect on drugs metabolised by this enzyme.