Astemizole MCQs With Answer: This focused review covers astemizole pharmacology, mechanism of action, pharmacokinetics, adverse effects and drug interactions tailored for B. Pharm students. Astemizole is a second‑generation H1 receptor antagonist formerly used for allergic rhinitis and urticaria; it has potent peripheral antihistaminic activity with minimal central sedation. Clinical importance arises from serious cardiac toxicity — QT prolongation and torsades de pointes due to hERG channel blockade — and significant CYP3A4-mediated interactions (e.g., macrolides, azoles, grapefruit). These MCQs emphasize mechanism, metabolism, safety monitoring, contraindications and alternative antihistamines, reinforcing core concepts in pharmacology, therapeutics and drug safety. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which description best fits astemizole?
- First‑generation sedating H1 antagonist
- Second‑generation non‑sedating H1 receptor antagonist
- Beta‑adrenergic blocker
- Proton pump inhibitor
Correct Answer: Second‑generation non‑sedating H1 receptor antagonist
Q2. What was the primary therapeutic use of astemizole?
- Analgesic for chronic pain
- Antihistamine for allergic rhinitis and urticaria
- Antiarrhythmic agent
- Antibiotic for respiratory infections
Correct Answer: Antihistamine for allergic rhinitis and urticaria
Q3. What major adverse effect led to worldwide withdrawal or restriction of astemizole?
- Hepatotoxicity
- QT prolongation and torsades de pointes
- Severe sedation and coma
- Renal failure
Correct Answer: QT prolongation and torsades de pointes
Q4. Astemizole is mainly metabolized by which hepatic enzyme system?
- CYP2D6
- CYP3A4
- CYP1A2
- UDP‑glucuronosyltransferase (UGT)
Correct Answer: CYP3A4
Q5. The cardiotoxicity of astemizole is primarily due to blockade of which channel?
- Cardiac sodium channels (Nav1.5)
- hERG (rapid delayed rectifier) potassium channels
- L‑type calcium channels
- Na+/K+ ATPase
Correct Answer: hERG (rapid delayed rectifier) potassium channels
Q6. Co-administration of astemizole with which of the following increases risk of arrhythmia?
- Paracetamol
- Erythromycin
- Ibuprofen
- Loratadine
Correct Answer: Erythromycin
Q7. What effect does grapefruit juice have on astemizole exposure?
- Induces CYP3A4 and decreases astemizole levels
- Has no clinically relevant effect
- Inhibits CYP3A4, increasing plasma astemizole levels and risk
- Increases renal elimination of astemizole
Correct Answer: Inhibits CYP3A4, increasing plasma astemizole levels and risk
Q8. Which statement about astemizole’s sedative effect is correct?
- Causes marked sedation comparable to first‑generation antihistamines
- Minimally sedating due to low central penetration
- Produces severe CNS depression at therapeutic doses
- Causes hallucinations as a common adverse effect
Correct Answer: Minimally sedating due to low central penetration
Q9. What is the primary active metabolite of astemizole?
- Desloratadine
- Desmethylastemizole (norastemizole)
- Fexofenadine
- Terfenadine
Correct Answer: Desmethylastemizole (norastemizole)
Q10. If astemizole exposure is suspected, which monitoring is most important?
- Liver function tests
- ECG monitoring for QT interval
- Blood glucose monitoring
- Chest X‑ray
Correct Answer: ECG monitoring for QT interval
Q11. Co‑administration of astemizole with ketoconazole is likely to cause:
- Reduced astemizole efficacy due to induction
- Increased astemizole levels and higher arrhythmia risk
- No interaction
- Enhanced renal clearance of astemizole
Correct Answer: Increased astemizole levels and higher arrhythmia risk
Q12. Astemizole’s penetration across the blood‑brain barrier is best described as:
- High, causing significant central effects
- Low, contributing to minimal sedation
- Moderate and dose‑dependent
- Unknown
Correct Answer: Low, contributing to minimal sedation
Q13. The pharmacodynamic action of astemizole is primarily:
- H2 receptor antagonist
- Selective H1 receptor antagonist
- Muscarinic receptor blocker
- Beta‑adrenergic agonist
Correct Answer: Selective H1 receptor antagonist
Q14. Which best describes astemizole’s elimination half‑life?
- Very short (<4 hours)
- Moderate (8–12 hours)
- Long (>24 hours)
- Extremely long (>7 days)
Correct Answer: Long (>24 hours)
Q15. Astemizole is contraindicated in patients with:
- Congenital long QT syndrome
- Chronic otitis media
- Uncontrolled diabetes mellitus
- Mild allergic rhinitis
Correct Answer: Congenital long QT syndrome
Q16. Which antihistamine is a safer clinical alternative with lower cardiac risk?
- Promethazine
- Chlorpheniramine
- Cetirizine
- Astemizole (continued use)
Correct Answer: Cetirizine
Q17. Astemizole belongs chemically to which class of antihistamines?
- Ethanolamine derivatives
- Alkylamine derivatives
- Piperidine derivatives
- Tricyclic antihistamines
Correct Answer: Piperidine derivatives
Q18. The usual route of administration for astemizole was:
- Topical application
- Intramuscular injection
- Oral administration
- Inhalation
Correct Answer: Oral administration
Q19. Which ECG change is classically associated with astemizole toxicity?
- Shortened PR interval
- Prolonged QT interval
- ST‑segment elevation in V1–V3
- Complete heart block
Correct Answer: Prolonged QT interval
Q20. Appropriate management of astemizole overdose includes:
- Immediate haemodialysis as first line
- Administration of cholinesterase inhibitors
- Supportive care with ECG monitoring and correction of electrolytes
- High‑dose corticosteroids
Correct Answer: Supportive care with ECG monitoring and correction of electrolytes
Q21. Astemizole’s anticholinergic effects are generally:
- Marked and clinically problematic
- Minimal compared with first‑generation antihistamines
- Equivalent to atropine
- Unknown and highly variable
Correct Answer: Minimal compared with first‑generation antihistamines
Q22. In vitro studies show astemizole blocks which cardiac target implicated in arrhythmia?
- Sodium channel Nav1.5
- hERG potassium channel
- Sarcoplasmic reticulum calcium release channel
- Vagal muscarinic receptors
Correct Answer: hERG potassium channel
Q23. What is the current regulatory status of astemizole in many countries?
- Over‑the‑counter antihistamine
- Widely used prescription drug with no warnings
- Withdrawn or severely restricted due to cardiac safety concerns
- Approved only for pediatric use
Correct Answer: Withdrawn or severely restricted due to cardiac safety concerns
Q24. Torsades de pointes is best characterized as:
- Atrial fibrillation with rapid ventricular response
- Polymorphic ventricular tachycardia often causing syncope
- Stable bradycardia without symptoms
- Isolated premature ventricular contractions with no risk
Correct Answer: Polymorphic ventricular tachycardia often causing syncope
Q25. Which of the following drugs would most likely potentiate astemizole cardiotoxicity?
- Ketoconazole
- Acetylsalicylic acid (aspirin)
- Metformin
- Vitamin C
Correct Answer: Ketoconazole
Q26. Hypokalemia in a patient taking astemizole would:
- Reduce the risk of QT prolongation
- Increase the risk of torsades de pointes
- Have no effect on cardiac risk
- Prevent astemizole absorption
Correct Answer: Increase the risk of torsades de pointes
Q27. Blockade of hERG channels by astemizole primarily produces which ECG abnormality?
- Shortened QT interval
- Prolonged QT interval
- Widened QRS complex only
- Peaked T waves
Correct Answer: Prolonged QT interval
Q28. What counseling point is important for patients with potential astemizole exposure?
- Avoid grapefruit juice and certain macrolide or azole antibiotics
- Take with milk to enhance absorption
- Double the dose if symptoms persist
- Use during pregnancy without concern
Correct Answer: Avoid grapefruit juice and certain macrolide or azole antibiotics
Q29. Blocking H1 receptors with astemizole produces which therapeutic benefit?
- Increased gastric acid secretion
- Reduced allergic symptoms such as itching, sneezing and rhinorrhea
- Direct bronchodilation via β2 stimulation
- Diuretic effect causing fluid loss
Correct Answer: Reduced allergic symptoms such as itching, sneezing and rhinorrhea
Q30. Compared with older first‑generation antihistamines, astemizole was originally favored because it:
- Was less sedating and had lower central anticholinergic effects
- Provided strong opioid‑like analgesia
- Was a potent anti‑inflammatory steroid
- Was significantly cheaper with identical safety
Correct Answer: Was less sedating and had lower central anticholinergic effects
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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