Comparing Second-Generation Antihistamines for Allergic Rhinitis
Cetirizine appears to be more effective than loratadine for treating allergic rhinitis symptoms, though it may cause slightly more sedation at recommended doses. 1
Efficacy Comparison
- Among second-generation antihistamines, several studies have found cetirizine to be superior to loratadine for decreasing mean rhinitis symptom scores in seasonal allergic rhinitis, although in one study the differences were not statistically significant 1
- In controlled environmental exposure studies, cetirizine produced significantly greater mean reductions than loratadine in both major symptom complex (37.4% vs 14.7%) and total symptom complex severity scores (36.7% vs 15.4%) 2, 3
- Cetirizine demonstrated a more rapid onset of action (within 1 hour) compared to loratadine (3 hours) in controlled pollen challenge studies 3
- In field studies conducted in outdoor parks during allergy season, cetirizine relieved rhinitis symptoms more effectively and quickly than loratadine 2
Sedation and Safety Profiles
There are important differences among second-generation antihistamines regarding sedative properties 1:
Cetirizine 10 mg may be associated with mild drowsiness (13.7% for patients age 12+ years) compared with placebo (6.3%), but typically without performance impairment 1
In some studies, higher doses of cetirizine (10 mg or above) have been associated with performance impairment 1
In comparative studies, the incidence of somnolence with cetirizine was greater than that of fexofenadine in some clinical trials and greater than loratadine or fexofenadine in a postmarketing surveillance study 4
Clinical Application
- For patients where efficacy is the primary concern, cetirizine may be preferred due to its superior symptom control and faster onset of action 2, 3
- For patients where minimal sedation is critical (e.g., those who drive, operate machinery, or need optimal cognitive function), loratadine may be preferred 1
- Dose titration of cetirizine (starting at 5 mg and increasing as needed up to 20 mg) may allow for greater efficacy in patients with refractory symptoms of allergic rhinitis 5
- Both cetirizine and loratadine demonstrate anti-inflammatory effects beyond histamine blockade, including reduction in eosinophil infiltration, inflammatory mediators, and ICAM-1 expression on nasal epithelial cells 6
Important Considerations
- Intranasal corticosteroids are more effective than oral antihistamines for overall control of allergic rhinitis symptoms, particularly nasal congestion 1
- For patients with both allergic rhinitis and asthma, leukotriene receptor antagonists (e.g., montelukast) may be considered 1
- In patients with severe symptoms, combination therapy may be necessary, such as an antihistamine with a decongestant or an intranasal corticosteroid 1
- Second-generation antihistamines are generally preferred over first-generation antihistamines due to less sedation, performance impairment, and anticholinergic effects 1