Cetirizine (CTZ)

Cetirizine is a second-generation antihistamine used in the treatment of hay fever, allergies, angioedema, and urticaria. It is a major metabolite of hydroxyzine, and a racemic selective H1 receptor inverse agonist. Cetirizine crosses the blood–brain barrier only slightly, reducing the sedative side-effect common with older antihistamines. It has also been shown to inhibit eosinophil chemotaxis and LTB4 release. Interleukin 6 and interleukin 8 have been shown to be elevated in acute respiratory distress syndrome. Cetirizine contains L- and D-stereoisomers. Chemically, levocetirizine is the active L-enantiomer of cetirizine. One recent study of airway epithelial cells showed that Levocetirizine may have beneficial effects on the pathophysiologic changes related to human rhinovirus (HRV) infection. Airway inflammation caused from a cytokine storm secondary to acute respiratory distress syndrome could also theoretically benefit.