Allegra (fexofenadine)

# Allegra (fexofenadine) ## Overview Fexofenadine is a second-generation, non-sedating histamine H1-receptor antagonist. It is a metabolite of terfenadine, lacking the cardiac toxicity profile of its parent compound due to its inability to block potassium channels (hERG). ## Primary Indications * Seasonal Allergic Rhinitis (SAR) * Chronic Idiopathic Urticaria (CIU) ## Adult Dosing * **SAR:** 60 mg PO twice daily OR 180 mg PO once daily. * **CIU:** 60 mg PO twice daily OR 180 mg PO once daily. * **Maximum Dose:** 180 mg per day. ## Pediatric Dosing * **Children 6 to 11 years:** 30 mg PO twice daily. * **Children 12 years and older:** Same as adult dosing (60 mg BID or 180 mg daily). * *Note:* Use age-appropriate formulations (tablets vs. oral suspension). Safety and efficacy in children <6 years are not established. ## Dose Adjustments * **Renal Impairment:** Reduce dose in patients with impaired renal function (e.g., CrCl <80 mL/min). A common starting dose is 60 mg once daily. * **Hepatic Impairment:** No specific adjustment required; primarily excreted unchanged in feces/urine. ## Contraindications * Hypersensitivity to fexofenadine or any component of the formulation. ## Adverse Effects * **Common:** Headache, nausea, dizziness, dysmenorrhea. * **Serious:** Rare reports of hypersensitivity reactions (urticaria, angioedema, chest tightness, anaphylaxis). * *Note:* Fexofenadine does not cross the blood-brain barrier significantly; sedation is comparable to placebo. ## Key Drug Interactions * **Aluminum/Magnesium-containing antacids:** May decrease fexofenadine absorption. Separate administration by at least 2 hours. * **Fruit Juices:** Grapefruit, orange, and apple juice may decrease the bioavailability of fexofenadine via inhibition of OATP (Organic Anion Transporting Polypeptides). Avoid consumption near the time of dosing. * **P-glycoprotein (P-gp) Inhibitors:** Medications such as erythromycin or ketoconazole may increase fexofenadine plasma concentrations. ## Monitoring * Monitor for symptomatic relief of allergic symptoms. * Monitor for signs of adverse effects if used in combination with P-gp inhibitors. ## Clinical Pearls * Unlike first-generation antihistamines, fexofenadine is preferred for patients requiring high levels of alertness (e.g., drivers, students). * For CIU, if standard doses are insufficient, some clinical guidelines suggest "off-label" uptitration (up to 4x standard dose), though this must be managed by an allergy/immunology specialist. * Absorption is not significantly influenced by food; however, the impact of fruit juices is clinically significant. *** *Disclaimer: This information is for educational purposes and does not constitute medical advice. Always verify current prescribing information, institutional protocols, and patient-specific factors with the latest resources (e.g., Lexicomp, Micromedex, or the official FDA label) before prescribing or administering medication.*