Promethazine is a 1st generation H1 blocker antihistamine. Which option lists a 1st generation H1 blocker?

Promethazine is a 1st generation H1 blocker antihistamine. Which option lists a 1st generation H1 blocker?

• A. Loratadine
• B. Promethazine
• C. Fexofenadine
• D. Cetirizine

Answer: (B)

First-generation H1 blockers cross the blood-brain barrier and tend to cause sedation and anticholinergic effects, unlike second-generation agents which are designed to cause less CNS penetration and fewer sedative effects. Promethazine is a classic example of a first-generation antihistamine, so it fits as the correct choice. The other drugs listed—loratadine, fexofenadine, and cetirizine—are second-generation antihistamines, chosen for their reduced sedative properties. Therefore, promethazine is the first-generation option.

First-generation H1 blockers cross the blood-brain barrier and tend to cause sedation and anticholinergic effects, unlike second-generation agents which are designed to cause less CNS penetration and fewer sedative effects. Promethazine is a classic example of a first-generation antihistamine, so it fits as the correct choice. The other drugs listed—loratadine, fexofenadine, and cetirizine—are second-generation antihistamines, chosen for their reduced sedative properties. Therefore, promethazine is the first-generation option.