Antihistamines
Drowsy vs non-drowsy
Allergies, hives and itching; the first-generation agents also treat motion sickness and are used for sleep.
Blocks histamine at the H1 receptor, so the allergic response is dampened.
The 6 antihistamines in the PTCB Top 200
| Generic | Brand | Common use |
|---|---|---|
| Hydroxyzine | Atarax / Vistaril | anxiety, itching |
| Cetirizine | Zyrtec | allergies |
| Loratadine | Claritin | allergies |
| Meclizine | Antivert | motion sickness, vertigo |
| Azelastine | Astelin | allergic rhinitis |
| Levocetirizine | Xyzal | allergies |
Tap any generic name for its full drug guide — brand↔generic, side effects, interactions and the exam tip.
What to know for the exam
- check_circleSecond-generation agents — cetirizine, loratadine, levocetirizine — cause far less drowsiness.
- check_circleFirst-generation agents such as hydroxyzine cross into the brain and sedate.
- check_circleAzelastine is a nasal spray version.
- check_circleMeclizine is used for motion sickness and vertigo.
First-generation antihistamines are on the list of medications to use cautiously in older adults — confusion, falls and urinary retention.
Generation is the dividing line: first sedates, second largely doesn't.
Drill antihistamines the way the PTCE asks them
RxReflex groups the Top 200 drugs into classes like this one, then quizzes you on brand↔generic, class, side effects and interactions. Plus a guided Learn path, pharmacy math and 40+ cheat sheets. Free to start.
Frequently asked
What drugs are in the antihistamines class? add
Hydroxyzine, Cetirizine, Loratadine, Meclizine, Azelastine, Levocetirizine. All are in the PTCB Top 200.
What are antihistamines used for? add
Allergies, hives and itching; the first-generation agents also treat motion sickness and are used for sleep.
How do antihistamines work? add
Blocks histamine at the H1 receptor, so the allergic response is dampened.
Last reviewed August 7, 2026. For education only — not medical advice. Not affiliated with or endorsed by the PTCB.