From the Guidelines
The best antihistamine to use is a second-generation antihistamine, such as fexofenadine, loratadine, or desloratadine, due to their lower likelihood of adverse effects compared to first-generation antihistamines. When choosing an antihistamine, it's essential to consider the patient's specific symptoms and needs. For everyday allergy relief, second-generation antihistamines like cetirizine (Zyrtec), loratadine (Claritin), or fexofenadine (Allegra) are generally recommended as they cause less drowsiness than first-generation options 1.
Key Considerations
- Cetirizine (10mg daily) may work faster but can cause mild drowsiness in some people.
- Loratadine (10mg daily) is less sedating but may take longer to work.
- Fexofenadine (180mg daily) typically causes the least drowsiness.
Additional Options
For severe allergies or sleep issues, diphenhydramine (Benadryl, 25-50mg) might be preferred at night due to its sedating effects. However, it's crucial to weigh the benefits against the potential risks of sedation, performance impairment, and anticholinergic effects associated with first-generation antihistamines 1.
Treatment Approach
These medications work by blocking histamine receptors that trigger allergy symptoms like sneezing, itching, and runny nose. Take antihistamines regularly during allergy season rather than as needed for better symptom control. If one antihistamine doesn't work well after 2-3 weeks, try switching to another type. Consult a healthcare provider if you have chronic conditions, take other medications, or if symptoms persist despite treatment 1.
From the FDA Drug Label
Fexofenadine hydrochloride, the major active metabolite of terfenadine, is an antihistamine with selective peripheral H1-receptor antagonist activity. Radiolabeled tissue distribution studies in rats indicated that fexofenadine does not cross the blood-brain barrier.
The best antihistamine to use cannot be determined from the provided information, as the FDA drug labels do not directly compare the effectiveness of different antihistamines.
- Fexofenadine has selective peripheral H1-receptor antagonist activity and does not cross the blood-brain barrier, which may indicate a lower risk of central nervous system effects 2.
- Cetirizine is also an antihistamine, but its mechanism of action and potential benefits are not directly described in the provided label 3.
From the Research
Antihistamine Options
- Levocetirizine is a selective, potent, oral histamine H(1) receptor antagonist that is effective and generally well tolerated in the treatment of allergic rhinitis and chronic idiopathic urticaria 4.
- Fexofenadine may offer the best overall balance of effectiveness and safety, and is an appropriate selection for initial or switch therapy for most patients with mild or moderate allergic symptoms 5.
- Cetirizine is the most potent antihistamine available and is appropriate for patients proven unresponsive to other antihistamines and for those with the most severe symptoms 5.
Administration Routes
- Both oral and intranasal antihistamines are approved for the first-line treatment of allergic rhinitis and both formulations result in a reduction in symptoms and an improvement in quality of life 6.
- Intranasal agents may be preferred in patients in whom nasal congestion is particularly bothersome or in cases where a more rapid onset of action is desired 6.
- Oral agents would be a better choice in young children, in cases of poor medication compliance, and in patients who are bothered most by histamine-associated symptoms, such as itching or red and watery eyes 6.
Safety and Efficacy
- Newer generation H1-antihistamines, such as levocetirizine and fexofenadine, are safer than first-generation H1-antihistamines and should be the first-line antihistamines for the treatment of allergic rhinitis and urticaria 7.
- Levocetirizine has a fast onset and long duration of action, with a well-tolerated adverse effect profile 8.
- Several large well-controlled clinical trials have shown levocetirizine to be consistently efficacious and well tolerated in relieving the symptoms of seasonal, perennial, and persistent allergic rhinitis, and chronic idiopathic urticaria 4, 8.