allergy:drug_classes:second_generation_h1
Second-Generation H1 Antihistamines
These agents are selective peripheral H1 receptor inverse agonists with minimal central nervous system penetration.
Primary use:
- Chronic urticaria
- Pruritus
Side-by-Side Comparison
| Drug | Usual Adult Dose | Sedation Risk | Elimination | Unique Feature |
|---|---|---|---|---|
| Loratadine | 10 mg daily | Very low | Hepatic (CYP3A4) | Prodrug |
| Desloratadine | 5 mg daily | Very low | Hepatic | Active metabolite |
| Cetirizine | 10 mg daily | Low | Renal | Active metabolite of hydroxyzine |
| Levocetirizine | 5 mg daily | Low | Renal | R-enantiomer refinement |
| Fexofenadine | 180 mg daily | Minimal | Renal/Fecal | Least sedating |
Sedation Spectrum (Low → Higher)
(Note: All far less sedating than first-generation agents.)
Clinical Selection Guide
If daytime alertness is critical: Fexofenadine
If patient has hepatic impairment: Cetirizine or Levocetirizine
If patient has renal impairment: Loratadine or Desloratadine
If chronic urticaria: Cetirizine commonly effective
Key Board Pearls
- Second-generation agents have minimal anticholinergic effects.
- Intranasal corticosteroids are superior for nasal congestion.
- Sedation varies within the class.
- Fexofenadine has the cleanest CNS profile.
- Cetirizine and levocetirizine require renal dose adjustment.
allergy/drug_classes/second_generation_h1.txt · Last modified: by andrew2393cns