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RESPIRATORY SYSTEM › ANTIHISTAMINES FOR SYSTEMIC USE › ANTIHISTAMINES FOR SYSTEMIC USE › Other antihistamines for systemic use
astemizole
R06AX11
Forms & Strengths
- Oral tablets: 10 mg (historically withdrawn globally due to toxicity)
Adult Dosing
- Allergic rhinitis and chronic urticaria: 10 mg orally once daily (historically)
Pediatric Dosing
- Children > 12 years: 10 mg orally once daily
- Children 6-12 years: 5 mg orally once daily
- Safety and efficacy not established in children < 6 years
Indications
- Symptomatic relief of seasonal allergic rhinitis
- Symptomatic relief of perennial allergic rhinitis
- Chronic idiopathic urticaria
Mechanism of Action
- Second-generation peripheral histamine H1-receptor antagonist
- Long duration of action due to slow dissociation from H1 receptors and active metabolites (desmethylastemizole)
- Lacks significant central nervous system sedative effects at standard doses
Contraindications
- Hypersensitivity to astemizole or excipients
- Concurrent administration of potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, erythromycin, clarithromycin)
- Patients with pre-existing prolonged QT syndrome or significant cardiac arrhythmias
- Severe hepatic impairment
Adverse Reactions
- Torsades de pointes and other ventricular arrhythmias (often fatal)
- QT prolongation
- Cardiac arrest
- Weight gain and increased appetite
- Somnolence, dizziness, headache
- Dry mouth
Drug Interactions
- CYP3A4 inhibitors (ketoconazole, itraconazole, macrolide antibiotics, protease inhibitors) significantly increase astemizole plasma levels, leading to fatal cardiac arrhythmias
- QT-prolonging drugs (antiarrhythmics, tricyclic antidepressants, phenothiazines) increase risk of cardiotoxicity
- Grapefruit juice inhibits CYP3A4 metabolism, elevating serum concentration
Curated Content: Needs Vetting Before Put to Clinical Use