Fexofenadine (Allegra) Dosage and Treatment Plan for Allergic Reactions
For allergic reactions, fexofenadine is recommended at a dose of 60 mg twice daily or 180 mg once daily for adults and children 12 years and older, and 30 mg twice daily for children 6-11 years. 1
Recommended Dosage by Age and Condition
Adults and Children 12 Years and Older:
- 60 mg twice daily OR 180 mg once daily with water for seasonal allergic rhinitis and chronic idiopathic urticaria 1
- For patients with decreased renal function, start with 60 mg once daily 1
Children 6 to 11 Years:
- 30 mg twice daily with water for seasonal allergic rhinitis and chronic idiopathic urticaria 1
- For pediatric patients with decreased renal function, start with 30 mg once daily 1
Treatment Considerations for Allergic Reactions
Advantages of Fexofenadine
- Non-sedating second-generation antihistamine, even at higher than FDA-approved doses 2
- Rapid onset of action (≤2 hours) with long duration, making it suitable for once-daily administration 3
- Does not cross the blood-brain barrier, avoiding sedative effects even at doses up to 240 mg/day 3
- Safety profile similar to placebo in clinical trials 4
Role in Allergic Reaction Management
- For milder allergic reactions (flushing, urticaria, mild angioedema), H1 antihistamines like fexofenadine are appropriate 5
- For anaphylaxis, fexofenadine may be used as adjunctive treatment after discharge, but is not first-line therapy 5
- Particularly effective for relieving symptoms of sneezing, rhinorrhea, itchy nose/palate/throat, and itchy/watery/red eyes 3
Treatment Duration
- For seasonal allergic rhinitis: Treatment should be continued throughout the allergy season 3
- For chronic idiopathic urticaria: Effective for up to 6 weeks of continuous treatment 3, 6
Special Considerations
Medication Discontinuation Before Testing
- When preparing for oral food challenge testing, fexofenadine should be discontinued 3 days before the test 5
Comparative Efficacy
- Fexofenadine 120 mg once daily is as effective as cetirizine 10 mg once daily and loratadine 10 mg once daily for seasonal allergic rhinitis 3, 7
- No single second-generation antihistamine has been conclusively shown to have superior overall efficacy 2
Safety Profile
- Does not inhibit cardiac K+ channels and is not associated with QT interval prolongation 3, 8
- No clinically significant drug interactions have been identified 4
- Most common adverse event is headache, occurring at similar rates to placebo 3
Important Caveats
- Fexofenadine should never be used alone in the treatment of anaphylaxis; epinephrine is the first-line treatment 5
- Has limited effect on nasal congestion; for excessive nasal congestion, combination with pseudoephedrine may be beneficial 3
- For post-anaphylaxis treatment, H1 antihistamines like fexofenadine should be continued for 2-3 days after discharge 5