Cetirizine is preferred over diphenhydramine for chronic urticaria in outpatients because it has which pharmacological advantage?

• A It is a selective H1 antagonist that does not cross the blood-brain barrier significantly, causing minimal sedation ✓
• B It has a faster onset of action due to parenteral administration
• C It also blocks H2 receptors providing combined gastric acid suppression
• D It inhibits leukotriene synthesis in addition to H1 blockade

Explanation

Cetirizine is a second-generation H1 antihistamine; its zwitterionic structure and P-glycoprotein-mediated efflux at the blood-brain barrier limit CNS penetration, resulting in minimal sedation compared to first-generation agents like diphenhydramine (which freely enter the CNS and block muscarinic, alpha-adrenergic and histamine receptors centrally). This non-sedating property makes cetirizine suitable for daytime chronic urticaria management. Neither H2 blockade nor leukotriene inhibition is a property of cetirizine.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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