Levocet-Natrapharm Drug Interactions

No formal drug interaction studies with levocetirizine to date; studies have been performed with racemic cetirizine. Does not inhibit cytochrome P-450 (CYP) isoenzymes 1A2, 2C9, 2C19, 2A1, 2D6, 2E1 or 3A4. Does not induce uridine diphosphate glucuronosyltransferase (UGT) 1A or CYP isoenzymes 1A2, 2C9 or 3A4. Unlikely to produce or be subject to pharmacokinetic interactions associated with metabolic enzyme systems.
Azithromycin: No clinically important changes in electrocardiogram (ECG) parameters observed following concomitant use with cetirizine and no clinically important interactions reported following such concomitant use.
Central Nervous System Depressants (eg, Alcohol): Possible additive CNS effects. Avoid concomitant use.
Cimetidine: No pharmacokinetic interactions observed with cetirizine.
Erythromycin: No clinically important changes in ECG parameters observed following concomitant use with cetirizine and no clinically important interactions reported following such concomitant use.
Ketoconazole: Prolongation of QTc interval (with an increase of 17.4 msec) observed following concomitant administration with cetirizine. No other clinically important interactions reported following such concomitant use. Not considered clinically important.
Pseudoephedrine: No pharmacokinetic interactions observed with cetirizine.
Ritonavir: Increased AUC (42%), increased t_½ (53%) and decreased clearance (29%) of cetirizine; disposition of ritonavir did not altered following concomitant administration with cetirizine.
Theophylline: Decreased clearance (16%) of cetirizine; disposition of theophylline did not altered following concomitant administration with cetirizine.