Monvex-L Drug Interactions

Montelukast: In drug interactions studies, the recommended clinical dose of Montelukast did not have clinically important effects on the pharmacokinetics of the following drugs: 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 CYP 3A4, caution should be exercised, particularly in children, when Montelukast is coadministered with inducers of CYP 3A4 such as phenytoin, phenobarbital and rifampicin. In vitro studies have shown that Montelukast is a potent inhibitor of CYP 2C8. However, data from a clinical drug-drug interaction study involving Montelukast and risoglitazone (a probe substrate representative of drugs primarily metabolized by CYP 2C8) demonstrated that Montelukast does not inhibit CYP 2C8 in vivo. Therefore, Montelukast is not anticipated to markedly alter after the metabolism of drugs metabolized by this enzyme (e.g., paclitaxel, risoglitazone and repaglinide).
Levocetirizine: In vitro data indicate that Levocetirizine is unlikely to produce pharmacokinetic interactions through inhibition or induction of liver drug-metabolizing enzymes. No in-vivo drug-drug interaction studies have been performed with Levocetirizine. In pharmacokinetic interaction studies performed with racemic cetirizine, cetirizine did not interact with antipyrine, pseudoephedrine, erythromycin, azithromycin, ketoconazole or cimetidine. A small decrease in the clearance of cetirizine was caused by a 400 mg dose of theophylline. Ritonavir increased the plasma AUC, half-life and decreased the clearance 42%, 53% and 29% respectively. The disposition of ritonavir was not altered by administration of cetirizine.