Controversies about Cardiotoxicity Effect of Second-Generation Antihistamines

What medicines are they?
Five examples of famous second-generation antihistamines are cetirizine, terfenadine, astemizole, ebastine, and loratadine.

What are their advantages compared to first-generation antihistamines?
First-generation antihistamines have several weaknesses; namely their tendency to cross blood-brain barrier and consequent sedative-anticholinergic side effects. Their half-life is also shorter, thus limiting their efficacy against allergic symptoms. These weaknesses have been "covered" by the second-generation antihistamines.
Overall, antihistamines are rapidly and completely absorbed after oral administration with peak plasma concentration reached within 1-4 hours. Most of second-generation antihistamines undergo an extensive first-pass metabolism via cytochrome P450 (Cyp3A4). But several of them (e.g. mizolastine) is not metabolized by this pathway, but by glucuronidation enzyme.