Therapeutic category: Second generation antihistaminic having selective H-1 receptor antagonist action.
Mechanism of action
Cetirizine, a human metabolite of hydroxyzine, is an antihistamine; its principle effects are mediated via selective inhibition of peripheral H, receptors.
Indications and usage
Seasonal allergic rhinitis: Oncet is indicated for the relief of symptoms associated with seasonal allergic rhinitis due to allergens such as ragweed, grass and tree pollens. Symptoms treated effectively include sneezing, rhinorrhea, nasal pruritus, ocular pruritus, tearing and redness of the eyes.
Perennial allergic rhinitis: Oncet is indicated for the relief of symptoms associated with perennial allergic rhinitis due to allergens such as dust mites, animal dander and molds. Symptoms treated effectively include sneezing, rhinorrhea, post-nasal discharge, nasal pruritus, ocular pruritus and tearing
Chronic urticarial: Oncet is indicated for the treatment of the uncomplicated skin manifestations of chronic idiopathic urticarial.
Pruritus: It significantly reduces the occurrence, severity and duration of hives and significantly reduces pruritus
Allergic conjunctivitis: the drug has been found to decrease the symptoms of allergic conjunctivitis
Cetirizine is contraindicated in those patients with a known hypersensitivity to it or hydroxyzine
Most adverse reactions reported during therapy with Oncet are mild or moderate. The common side effects are somnolence, fatigue, dry mouth, pharyngitis, dizziness.
To date there are no known interactions with other drugs. Studies with diazepam and cimetidine have revealed no evidence of drug interaction. As with other antihistamines, excessive alcohol consumption should be avoided.
No clinically significant drug interactions have been found with Theophylline at low dose, Azithromycin, Pseudoephedrine, Ketoconazole or Erythromycin. There was a small decrease in the clearance of cetirizine caused by a 400 mg dose of Theophylline, it is possible that larger Theophylline doses could have a greater effect.
Activities requiring metal alertness
In clinical trials, the occurrence of somnolence has been reported in some patients taking cetirizine; due caution should therefore be exercised when driving a car or operating potentially dangerous machinery. Concurrent use of Oncet with alcohol or other CNS depressants should be avoided because additional reductions in alertness and additional impairment of CNS performance may occur.
Cetirizine has been reported to be excreted in human breast milk; use of Oncet in nursing mothers is not recommended.
Dosage and administration
The recommended initial dose of Oncet is 5 or 10 mg per day in adults and children above 12 years, depending on symptoms severity. Most patients in clinical trials started at 10 mg. Oncet is given as a single daily dose, with or without food.