Chapter 30 - Decreasing Histamine Effects and Allergic Response

Question 1

diphenhydramine (Benadryl)

Answer 1

Class: Antihistamine First-generation H1 receptor antagonists

• MOA: occupies the same receptor site as histamine and prevents histamine from acting on target tissues. Inhibit vascular permeability, edema formation, bronchoconstriction, and pruritus associated with histamine release. They DO NOT block or decrease the amount of histamine released
• Use: allergic rhinitis, motion sickness, insomnia, allergic reactions
• Admin: for motion sickness 30-60 minutes before travel; give IV dose slowly over several minutes –> (Dramamine = 1st generation antihistamine)
• AE: young children may have paradoxical excitement, CNS depression, CNS stimulation, anticholinergic effects

Question 2

fexofenadine (Allegra)

Answer 2

Class: Antihistamine Second-generation H2 receptor antagonists

• MOA: competes with histamine for binding to histamine receptor sites
• Use: allergic rhinitis, pruritus in urticaria, minor allergies
• Admin: most available OTC, also have some nasal spray preparations (Astelin)
• AE: minor – headache, N/V, dysmenorrhea, fatigue
• Safer, especially for older adults, than 1st generation antihistamines