IMMUNOLOGY

Detailed explanation-1: -Loratadine, cetirizine, and fexofenadine are the most commonly prescribed second-generation antihistamines. Many tests have been conducted to assess the central effects of these three drugs. Compared with placebo, at recommended doses loratadine is not associated with performance impairment.

Detailed explanation-2: -Loratadine (Claritin) Nonsedating second-generation antihistamine. Fewer adverse effects than with first-generation medications. Selectively inhibits peripheral histamine H1 receptors. Available as tab, disintegrating tab (Reditab), syr (5 mg/5 mL), or combined with pseudoephedrine in 12-or 24-h preparations.

Detailed explanation-3: -First-generation antihistamines block both histaminic and muscarinic receptors as well as passing the blood-brain barrier. Second-generation antihistamines mainly block histaminic receptors and do not pass the blood-brain barrier.