Zyrtec-D Drug Interactions

No interaction studies have been performed with the combination cetirizine-pseudoephedrine.
Cetirizine-component: Simultaneous use with pseudoephedrine, cimetidine, ketoconazole, erythromycin or azithromycin does not influence the pharmacokinetic parameters of cetirizine. No pharmacokinetic interactions were observed. According to in vitro tests, cetirizine does not influence the protein-bonding effect of warfarin.
Simultaneous administration with azithromycin, erythromycin, ketoconazole, theophylline and pseudoephedrine showed no relevant changes in the clinical laboratory parameters, vital functions and ECG.
In a study with the simultaneous administration of theophylline (400 mg daily) and cetirizine (20 mg daily), a slight but statistically significant elevation of the 24-hour AUC of 19% was found for cetirizine as well as 11% for theophylline. Furthermore, the maximum plasma levels increased to 7.7% and 6.4% respectively for cetirizine and theophylline. Simultaneously, the clearance of cetirizine lessened by -16% as well as -10% in the case of theophylline while cetirizine was being taken by patients who had received prior treatment with theophylline. Prior treatment with cetirizine did not, however, significantly influence the pharmacokinetic parameters of theophylline.
After a single dose of 10 mg cetirizine, the effect of alcohol (0.8%) was not significantly potentiated; a statistically significant interaction with Diazepam 5 mg was proven for one of 16 psychometric tests.
Simultaneous administration of 10 mg cetirizine daily with glipicide led to a slight drop in the glucose parameters. This effect is not clinically relevant. Nonetheless, separate administration - glipicide in the morning and cetirizine in the evening - is recommended. The extent of to which cetirizine is absorbed is not reduced by simultaneous food intake although the absorption is decreased by 1 hour.
In a multiple dose study of ritonavir (600 mg twice daily) and cetirizine (10 mg daily), the extent of exposure to cetirizine was increased by about 40% while the disposition of ritonavir was slightly altered (-11%) further to concomitant cetirizine administration.
Allergy skin tests are inhibited by antihistamines and an appropriate wash-out period is required before performing them.
A high fat meal was not found to modify the bioavailability of both active ingredients, but it resulted however in a reduced and delayed peak plasma concentration of cetirizine.
Pseudoephedrine-component: Simultaneous treatment with pseudoephedrine and MAOI (Monoamine Oxidase Inhibitors) can result in hypertensive crisis. Because of the long duration of action of MAOI (Monoamine Oxidase Inhibitors), this interaction may be observable during a period of 15 days following MAOI treatment.
Sympathomimetic amines may reduce the antihypertensive effects of beta-adrenergic blockers and of drugs that interfere with sympathetic activity such as methyldopa, guanethidine and reserpine (see Precautions).
Administration of linezolid with pseudoephedrine may result in an increase in blood pressure in normotensive patients.
Increased ectopic pacemaker activity can occur when pseudoephedrine is used concomitantly with digitalis; use of cetirizine-pseudoephedrine is therefore to be avoided in digitalized patients.
Antacids and proton pump inhibitors increase the rate of pseudoephedrine absorption; kaolin decreases it.
Concurrent use with halogenated anaesthetic agents may provoke or worsen ventricular arrhythmia.