Indications: Alerfast is indicated for the relief of symptoms associated with seasonal and perennial allergic rhinitis in adults and children 12 years of age and older. Symptoms effectively treated include sneezing, rhinorrhea, lacrimation, itchy/red eyes, and itching of the nose/palate/throat. It is also indicated for chronic idiopathic urticaria to relieve itching and reduce hives.

Pharmacology: Histamine H1 receptors mediate hypersensitivity and allergic reactions. Exposure to allergens causes mast cell and basophil degranulation, releasing histamine and other inflammatory mediators. Histamine binds to H1 receptors, leading to cytokine release and allergic symptoms such as pruritus, rhinorrhea, and watery eyes. Fexofenadine acts as an “inverse agonist” of the H1 receptor, stabilizing its inactive form and preventing activation. It has potent and selective affinity for H1 receptors, without antidopaminergic, antiserotonergic, anticholinergic, sedative, or adrenergic blocking activity. Fexofenadine does not cross the blood‑brain barrier, minimizing CNS effects.

Dosage & Administration:

Allergic Rhinitis:
- Adults & children ≥12 years: 60 mg twice daily or 120 mg once daily or 180 mg once daily.
- Impaired renal function: 60 mg once daily.
- Children 6–11 years: 30 mg twice daily or 60 mg once daily.
- Children 2–5 years: Suspension 30 mg (5 ml) twice daily; impaired renal function: 30 mg once daily.
Chronic Idiopathic Urticaria:
- Adults & children ≥12 years: 60 mg twice daily or 120 mg once daily or 180 mg once daily.
- Impaired renal function: 60 mg once daily.
- Children 6–11 years: 30 mg twice daily or 60 mg once daily.
- Children 6 months–2 years: Suspension 15 mg (2.5 ml) twice daily; impaired renal function: 15 mg once daily.
- Children 2–11 years: Suspension 30 mg (5 ml) twice daily; impaired renal function: 30 mg once daily.

Interactions: Fexofenadine does not undergo hepatic biotransformation, reducing drug interaction risk. Co‑administration with erythromycin or ketoconazole increases plasma fexofenadine levels 2–3 times, without QT prolongation or increased adverse reactions. No interaction with omeprazole. Antacids containing aluminum/magnesium hydroxide reduce bioavailability if taken within 15 minutes; separate administration by 2 hours.

Contraindications: Contraindicated in patients with known hypersensitivity to fexofenadine hydrochloride or any component of the formulation.

Side Effects:

Common: Headache, dizziness, nausea, drowsiness.
Uncommon: Fatigue.
Rare/Unknown frequency: Hypersensitivity reactions (angioedema, chest tightness, dyspnea, flushing, systemic anaphylaxis), insomnia, nervousness, sleep disorders, tachycardia, palpitations, diarrhea, rash, urticaria, pruritus.