What is Fexofenadine (Allegra) used for in the treatment of allergic reactions in adults and children with a history of kidney or liver disease?

Fexofenadine: Primary Indications and Use

Fexofenadine is FDA-approved for treating seasonal allergic rhinitis and chronic idiopathic urticaria in adults and children 6 years and older, with specific advantages in patients requiring a truly non-sedating antihistamine, particularly those with kidney disease, liver disease, or at risk of falls. 1

FDA-Approved Indications

Seasonal Allergic Rhinitis

• Adults and children ≥12 years: 60 mg twice daily or 180 mg once daily 1
• Children 6-11 years: 30 mg twice daily 1
• Effectively treats sneezing, rhinorrhea, itchy nose/palate/throat, and itchy/watery/red eyes 1
• Has limited effect on nasal congestion, similar to other oral antihistamines 2, 3

Chronic Idiopathic Urticaria

• Adults and children ≥12 years: 60 mg twice daily or 180 mg once daily 1
• Children 6-11 years: 30 mg twice daily 1
• Significantly reduces pruritus and number of wheals 1, 4
• Effective for up to 6 weeks of continuous treatment 3

Critical Advantages in Special Populations

Patients with Kidney Disease

• Dose adjustment required: Start with 60 mg once daily (instead of twice daily or 180 mg) in adults with decreased renal function 1
• Pediatric adjustment: 30 mg once daily in children 6-11 years with renal impairment 1
• Unlike cetirizine, which requires 50% dose reduction in moderate renal impairment and should be avoided in severe renal impairment, fexofenadine has a simpler dosing adjustment 2, 5

Patients with Liver Disease

• No hepatic contraindications: Unlike mizolastine (contraindicated in significant hepatic impairment) and alimemazine (hepatotoxic), fexofenadine can be safely used in liver disease 2
• Does not undergo hepatic metabolism via cytochrome P450 CYP 3A4, avoiding drug interactions common with hepatically metabolized antihistamines 6

Patients at Risk of Falls or Requiring Alertness

• Truly non-sedating: Fexofenadine maintains non-sedating properties even at doses exceeding FDA recommendations (up to 240 mg/day), making it the gold standard when sedation must be absolutely avoided 5, 7
• No psychomotor impairment: Does not cross the blood-brain barrier and shows no dose-related increase in sedation 3, 7
• Preferred in elderly: Particularly advantageous for older adults who are more sensitive to psychomotor impairment and fall risk from other antihistamines 5

Comparison with Other Second-Generation Antihistamines

Non-Sedating Profile

• Fexofenadine: Completely non-sedating at all doses 5, 7
• Loratadine/Desloratadine: Non-sedating at recommended doses but may cause sedation at higher doses 2, 5
• Cetirizine/Levocetirizine: May cause mild drowsiness (13.7% vs 6.3% placebo) even at standard doses 5

Clinical Efficacy

• Fexofenadine 120 mg once daily is as effective as cetirizine 10 mg once daily and loratadine 10 mg once daily for overall symptom reduction in seasonal allergic rhinitis 3
• Produces greater improvements in quality of life than loratadine to a clinically meaningful extent 3
• All doses from 60-240 mg twice daily are superior to placebo for chronic urticaria, with 60 mg twice daily being the optimal effective dose 4

Common Pitfalls and Caveats

Drug and Food Interactions

• Avoid with fruit juices: Orange and grapefruit juices significantly reduce fexofenadine bioavailability; always take with water 1, 6
• P-glycoprotein interactions: Although fexofenadine doesn't use CYP 3A4, it interacts at P-glycoprotein and organic anion transporter polypeptides, potentially increasing toxicity risk of other drugs 6

Cardiac Safety

• No cardiotoxicity: Does not inhibit cardiac K+ channels or prolong QT interval, even when combined with erythromycin or ketoconazole 3, 7
• Safe alternative for patients who cannot use terfenadine or astemizole (removed from market for cardiotoxic effects) 2

Limitations

• Nasal congestion: Like all oral antihistamines, fexofenadine has limited effect on nasal congestion; consider adding pseudoephedrine or switching to intranasal corticosteroids for this symptom 2, 3
• Not for anaphylaxis: H1 antihistamines relieve itching and urticaria but do not relieve respiratory symptoms in anaphylaxis 5

Pregnancy Considerations

• Should be avoided in pregnancy, especially during the first trimester, though not shown to be teratogenic in humans 5