What type of antihistamine is Zyrtec, and more specifically, is it considered a first-generation or second-generation antihistamine? Beyond just that classification, can you tell me about the specific receptor that Zyrtec primarily targets (H1, H2, etc.), and how its mechanism of action at that receptor leads to the relief of allergy symptoms? Finally, does Zyrtec cross the blood-brain barrier to a significant extent, and how does this relate to its potential for causing drowsiness compared to other antihistamines?

Answer

Zyrtec (cetirizine) is a second-generation antihistamine.