Pharmacology
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. At a dosage of 20 mg, Boone et al. found that it inhibited the expression of VCAM-1 in patients with atopic dermatitis.
The levorotary enantiomer of cetirizine, known as levocetirizine, is the more active form.
Read more about this topic: Cetirizine