From the Guidelines
Both Zyrtec (cetirizine) and Allegra (fexofenadine) are effective second-generation antihistamines for treating allergic symptoms, but they differ in their sedative properties, with Zyrtec causing more sedation in about 10-15% of users, as noted in studies 1. The main difference between Zyrtec and Allegra lies in their potential to cause sedation, with Allegra being virtually non-sedating and a better choice for people who need to remain alert or who experience drowsiness with Zyrtec.
- Zyrtec typically works faster, within 1 hour, and may be more effective for some people with severe allergies.
- Allegra, on the other hand, is usually taken at 180mg once daily or 60mg twice daily and its absorption may be reduced when taken with certain fruit juices. Some key points to consider when choosing between Zyrtec and Allegra include:
- Sedation risk: Zyrtec causes more sedation, while Allegra is virtually non-sedating, as stated in 1.
- Dosage: Zyrtec is typically taken once daily at 10mg for adults, while Allegra is usually taken at 180mg once daily or 60mg twice daily.
- Food interaction: Both medications can be taken with or without food, though Allegra's absorption may be reduced when taken with certain fruit juices, as mentioned in 1.
- Alcohol interaction: Neither should be used with alcohol due to increased sedation risk. It's also important to note that individual responses to these medications can vary, and if one medication doesn't work well after 1-2 weeks of consistent use, trying the other is reasonable, as both medications work by blocking histamine receptors to reduce allergy symptoms like sneezing, itching, watery eyes, and runny nose, as explained in 1.
From the Research
Comparison of Zyrtec and Allegra
- Zyrtec (cetirizine) and Allegra (fexofenadine) are both second-generation antihistamines used to treat allergic symptoms, including seasonal allergic rhinitis and chronic idiopathic urticaria 2, 3.
- Both medications are considered non-sedating, meaning they are less likely to cause drowsiness compared to first-generation antihistamines 2, 3.
- Studies have shown that both cetirizine and fexofenadine are effective in reducing symptoms of seasonal allergic rhinitis, including sneezing, rhinorrhea, itchy nose, and itchy, watery, or red eyes 4, 5.
Efficacy Comparison
- A study comparing cetirizine and loratadine found that cetirizine performed better in reducing symptom scores, although the difference was not statistically significant 4.
- Another study comparing fexofenadine and cetirizine found that both medications were effective in reducing total symptom scores, with no significant difference between the two 5.
- A study using an environmental exposure unit found that cetirizine produced a greater reduction in total symptom complex scores compared to loratadine and placebo, with an onset of action within 1 hour 6.
Safety Profile
- Both cetirizine and fexofenadine have been shown to be well-tolerated, with a similar incidence of adverse events compared to placebo 3, 5.
- However, cetirizine has been associated with a higher incidence of drowsiness or fatigue compared to fexofenadine 5.
- Fexofenadine does not cross the blood-brain barrier, making it less likely to cause sedative effects 3.