Which of the following is a commonly used antihistamine with the brand name Benadryl?

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

Answer: (A)

Benadryl is the brand name most people associate with an old, well-known antihistamine, which is diphenhydramine. The reason this one fits the brand mapping is that diphenhydramine is a first-generation H1 blocker. It crosses into the brain easily, so it not only blocks allergic symptoms like sneezing and itching but also causes noticeable drowsiness and some drying effects due to its anticholinergic actions.

The other drugs listed—loratadine, cetirizine, and fexofenadine—are second-generation antihistamines. They work similarly to block histamine at the H1 receptor but are designed to penetrate the brain less, so they typically produce much less sedation. That’s why they’re marketed as non-sedating options (though they still relieve allergy symptoms).

So the brand Benadryl corresponds to diphenhydramine, while the others are different antihistamines with a lower likelihood of causing drowsiness.