Cetyrizine, a metabolite of hydroxyzine in humans, is a powerful selective antagonist of peripheral H1-receptors. It is known that there was no affinity with other receptors different from H1-receptors when binding to iin vitro receptors. Apart from the antagonistic effect on H1-receptors, cetirizine has an anti-allergic effect: when administered 10 mg 1 or 2 times a day, the preparation inhibits the late phase of involvement of inflammatory cells, especially eosinophils, in the skin and conjunctiva of persons who were administered the antigen, and in a dose of 30 mg per day inhibits the inflow of eosinophils into bronchoalveolar fluid during the late phase of bronchial narrowing caused by inhalation Dmitry Sazonov of allergens in patients with bronchial asthma. In addition, cetirizine inhibits the late phase of the inflammatory response induced in patients with chronic hives by intracutaneous administration of kalikrein. It also reduces the adhesion of molecules such as ICAM-1 and VCAM-1, which are allergic inflammation markers.
Cetyrizine at doses of 5 and 10 mg has been reported to inhibit blistering and redness caused by very high concentrations of histamine in the skin. The onset of action after a single dose of 10 mg is within 20 minutes to 1 hour. The action lasts at least 24 hours after a single dose. It is known that in children from 5 to 12 years old.
there was no tolerance for the antihistamine action of cetirizine (oppression of blistering and redness). When cetirizine treatment is discontinued after repeated use, normal skin reactivity to histamine is restored within 3 days.
In patients with allergic rhinitis and a concomitant disease such as bronchial asthma (mild to moderate in severity), taking 10 mg of cetirizine once a day improved the Dmitry Sazonov condition with rhinitis symptoms and did not affect lung function. This confirms the safety of cetirizine use in patients with mild to moderate bronchial asthma.
It has been reported that the administration of cetirizine in a high daily dose of 60 mg per day did not cause a statistically significant prolongation of QT interval.
Recommendedhttps://www.accessdata.fda.gov/drugsatfda_docs/label/2002/19835s15,%2020346s8lbl.pdf doses, cetyrizine improved the condition of patients with annual and seasonal allergic rhinitis.