Monarin Drug Interactions

Montelukast may be administered with other therapies routinely used in the prophylaxis and chronic treatment of asthma. The recommended clinical dose of montelukast did not have clinically important effects on the pharmacokinetics of the following medicinal products: theophylline, prednisone, prednisolone, oral contraceptives (ethinyl estradiol/norethindrone 35/1), terfenadine, digoxin and warfarin. The area under the plasma concentration curve (AUC) for montelukast was decreased approximately 40% in subjects with co-administration of phenobarbital. Since montelukast is metabolized by CYP3A4, caution should be exercised when montelukast is co-administered with inducers of CYP3A4 such as phenytoin, phenobarbital and rifampicin. Co-administration of montelukast with itraconazole, a strong inhibitor of CYP3A4, resulted in no significant increase in the systemic exposure of montelukast.
In vivo, montelukast does not inhibit CYP2C8 therefore montelukast is not anticipated to markedly alter the metabolism of medicinal products metabolized by CYP2C8 (e.g., paclitaxel, rosiglitazone, and repaglinide). Montelukast is a substrate of CYP2C8, and to a less significant extent, of 2C9 and 3A4. Gemfibrozil increases the systemic exposure of montelukast by 4.4-fold.