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# Allegra (fexofenadine)
## Overview
Fexofenadine is a second-generation, non-sedating, selective histamine H1-receptor antagonist. Unlike first-generation antihistamines, it does not readily cross the blood-brain barrier.
## Primary Indications
* Seasonal Allergic Rhinitis (SAR)
* Chronic Idiopathic Urticaria (CIU)
## Adult Dosing
* **SAR:** 60 mg twice daily OR 180 mg once daily.
* **CIU:** 60 mg twice daily OR 180 mg once daily.
* *Maximum:* 180 mg per 24 hours.
## Pediatric Dosing
* **Ages 6–11 years:** 30 mg twice daily.
* **Ages ≥12 years:** Same as adult dosing (60 mg BID or 180 mg daily).
* *Note:* Tablets are generally not recommended for children <6 years; oral suspension is preferred. Dosing for <6 years depends on product-specific formulation; always verify tablet vs. suspension titration against the specific product label.
## Dose Adjustments
* **Renal Impairment:**
* Adults: 60 mg once daily is the recommended starting dose for patients with decreased renal function (CrCl <80 mL/min).
* Pediatrics (6–11 years): 30 mg once daily.
* **Hepatic Impairment:** No dosage adjustment necessary.
## Contraindications
* Known hypersensitivity to fexofenadine or any components of the formulation.
## Adverse Effects
* **Common:** Headache, upper respiratory tract infection, nausea, dysmenorrhea, dizziness.
* **Rare:** Hypersensitivity reactions (urticaria, angioedema, chest tightness, dyspnea).
## Key Drug Interactions
* **Antacids (Aluminum/Magnesium):** May reduce fexofenadine absorption; space doses by at least 2 hours.
* **Fruit Juices (Grapefruit, Orange, Apple):** May significantly decrease fexofenadine bioavailability via inhibition of OATP1A2 transporters; avoid co-administration.
* **Erythromycin/Ketoconazole:** May increase fexofenadine plasma concentrations (likely due to P-glycoprotein transport interference), though clinical significance is generally minor.
## Monitoring
* Efficacy regarding allergy/urticaria symptom relief.
* Monitor for signs of hypersensitivity.
* In patients with renal impairment, monitor for symptoms of overdose (e.g., fatigue, dizziness).
## Clinical Pearls
* Fexofenadine is preferred in patients where non-sedation is critical compared to first-generation antihistamines.
* Does not demonstrate significant anticholinergic effects.
* High doses (up to 240 mg/day) are sometimes used off-label for recalcitrant urticaria; consult local clinical protocols or dermatology guidelines before exceeding 180 mg/day.
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*Disclaimer: This information is for educational purposes only. Always verify dosing, contraindications, and drug interactions against the most current FDA-approved prescribing information or institutional clinical resources before prescribing or administering medication.*
