antihistamines - exam 3

What is the mechanism of action of antihistamines?

block histamine (H1 or H2 receptors) to reduce allergic reactions, inflammation, and gastric acid secretion.

What are first-generation antihistamines primarily used for?

Allergies, motion sickness, nausea, insomnia, and cold symptoms.

Why do first-generation antihistamines cause drowsiness?

They cross the blood-brain barrier and block H1 receptors in the CNS, leading to sedation.

Which first-generation antihistamine is commonly used for allergic reactions?

Diphenhydramine (Benadryl).

What are common side effects of first-generation antihistamines?

Drowsiness, dry mouth, dizziness, blurred vision, urinary retention.

Why should elderly patients use first-generation antihistamines with caution?

Increased risk of falls, confusion, and anticholinergic effects.

What are second-generation antihistamines primarily used for?

Seasonal allergies, urticaria (hives), and chronic allergic conditions.

Why do second-generation antihistamines cause less drowsiness?

They do not cross the blood-brain barrier as easily as first-generation antihistamines.

Which antihistamines are second-generation and non-drowsy?

Loratadine (Claritin), Fexofenadine (Allegra), Cetirizine (Zyrtec).

What is the key patient education for antihistamines?

Avoid alcohol, be cautious with driving (first-gen), and do not take with other CNS depressants.

Which antihistamine is used for anaphylaxis?

Diphenhydramine (Benadryl) is often used alongside epinephrine.

Which antihistamines are available as nasal sprays?

Azelastine (Astelin)