Fexofenadine

# Fexofenadine ## Overview - **Classification**: Second-generation antihistamine, H1-receptor antagonist. - **Mechanism**: Selectively blocks peripheral H1 histamine receptors, preventing histamine-mediated symptoms of allergic reactions. It has minimal to no sedative or anticholinergic effects. ## Primary Indications 1. **Seasonal Allergic Rhinitis** - Relief of symptoms (sneezing, rhinorrhea, itchy/watery eyes, nasal/palatal itching). 2. **Chronic Idiopathic Urticaria (CIU)** - Relief of symptoms (itching, rash, hives). ## Adult Dosing ### Standard Dosing **Seasonal Allergic Rhinitis** - **Dose**: **60 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **OR** - **Dose**: **180 mg** - **Frequency**: Once daily (QD) - **Route**: Oral **Chronic Idiopathic Urticaria (CIU)** - **Dose**: **180 mg** - **Frequency**: Once daily (QD) - **Route**: Oral ### Dose Adjustments - **Renal Impairment**: For CrCl < 50 mL/min (including ESRD), reduce dose to **60 mg once daily**. - **Hepatic Impairment**: No dose adjustment is generally needed. - **Elderly Patients**: No specific dose adjustment needed unless renal impairment is present. Monitor for renal function. ## Pediatric Dosing ### Neonates (0-28 days) - **Special Notes**: Not recommended. Safety and efficacy have not been established. ### Infants (1-12 months) - **Chronic Idiopathic Urticaria (6 months to < 2 years)** - **Dose**: **15 mg** - **Frequency**: Twice daily (BID) - **Maximum**: **30 mg/day** - **Special Notes**: Use oral suspension formulation. ### Children (1-12 years) - **Seasonal Allergic Rhinitis (2-11 years)** - **Dose**: **30 mg** - **Frequency**: Twice daily (BID) - **Maximum**: **60 mg/day** - **Special Notes**: Use oral suspension or 30 mg tablet. - **Chronic Idiopathic Urticaria (2-11 years)** - **Dose**: **30 mg** - **Frequency**: Twice daily (BID) - **Maximum**: **60 mg/day** - **Special Notes**: Use oral suspension or 30 mg tablet. - **Renal Impairment (CrCl < 50 mL/min)**: - **6 months to < 2 years**: **15 mg once daily**. - **2 to 11 years**: **30 mg once daily**. ### Adolescents (13-18 years) - **Dose**: Treat as adults. **60 mg BID** or **180 mg once daily**. - **Maximum**: **180 mg/day**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to fexofenadine or any component of the formulation. ### Common Adverse Effects - **Common (1-10%)**: Headache, drowsiness (very mild compared to 1st gen), nausea, dizziness, fatigue. - **Serious but Rare**: Hypersensitivity reactions (e.g., angioedema, anaphylaxis). ### Key Drug Interactions - **Aluminum/Magnesium-containing Antacids**: Reduces fexofenadine absorption. - **Monitoring**: Separate administration by at least **2 hours**. - **Fruit Juices (Grapefruit, Orange, Apple)**: Significantly reduces fexofenadine bioavailability. - **Monitoring**: Avoid co-administration. Take with water. - **Erythromycin / Ketoconazole**: May slightly increase fexofenadine plasma levels, but usually not clinically significant due to fexofenadine's wide therapeutic window. ## Monitoring & Follow-up - **Before Treatment**: None typically required. - **During Treatment**: Monitor for symptom improvement (e.g., reduction in sneezing, itching, hives). - **Clinical Signs**: Watch for resolution of allergy symptoms; note any adverse effects. ## Clinical Pearls - 💡 **Tip 1**: Fexofenadine is generally **non-drowsy** compared to first-generation antihistamines. - 💡 **Tip 2**: Always take fexofenadine with **water**, not fruit juices (e.g., grapefruit, orange, apple), as juices can reduce absorption. - 💡 **Tip 3**: Avoid taking antacids containing aluminum or magnesium within **2 hours** of fexofenadine. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.