Alpha adrenergic blockers – Dihydroergotamine MCQs With Answer
This concise guide helps B. Pharm students master alpha adrenergic blockers and dihydroergotamine through focused, exam-oriented content. Learn key concepts: receptor selectivity (alpha-1 vs alpha-2), mechanisms of action, pharmacokinetics, therapeutic uses in hypertension, BPH and migraine, adverse effects such as orthostatic hypotension and ergotism, important drug interactions (CYP3A4 inhibitors, vasoconstrictors), and clinical precautions. The questions emphasize mechanism-based reasoning, clinical pharmacology, and formulation differences to boost retention and application. Ideal for revision, viva prep and competitive exams, the set links theory to practice for pharmacy students. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which receptor subtype primarily mediates vasoconstriction targeted by alpha-1 adrenergic blockers?
- Alpha-1 receptor (Gq coupled)
- Alpha-2 receptor (Gi coupled)
- Beta-1 receptor (Gs coupled)
- Beta-2 receptor (Gs coupled)
Correct Answer: Alpha-1 receptor (Gq coupled)
Q2. Which of the following drugs is a selective alpha-1 adrenergic antagonist used for benign prostatic hyperplasia?
- Prazosin
- Phentolamine
- Phenoxybenzamine
- Clonidine
Correct Answer: Prazosin
Q3. Phenoxybenzamine differs from phentolamine because it is:
- An irreversible alpha antagonist
- A selective alpha-1 antagonist
- A beta antagonist
- A reversible alpha-2 agonist
Correct Answer: An irreversible alpha antagonist
Q4. A common adverse effect of alpha-1 blockers related to vasodilation is:
- Orthostatic hypotension
- Bradycardia
- Constipation
- Hyperglycemia
Correct Answer: Orthostatic hypotension
Q5. Dihydroergotamine (DHE) is primarily used clinically for:
- Acute migraine treatment
- Chronic hypertension management
- Type II diabetes
- Asthma exacerbations
Correct Answer: Acute migraine treatment
Q6. Which route is commonly used for dihydroergotamine administration due to low oral bioavailability?
- Intravenous or intranasal
- Oral tablet
- Subcutaneous injection for chronic use
- Transdermal patch
Correct Answer: Intravenous or intranasal
Q7. Alpha-2 adrenergic receptor activation in the CNS primarily causes:
- Decreased sympathetic outflow
- Increased peripheral vasoconstriction
- Bronchodilation
- Enhanced insulin secretion
Correct Answer: Decreased sympathetic outflow
Q8. Which alpha blocker is commonly associated with a “first-dose” syncope phenomenon?
- Prazosin
- Phenoxybenzamine
- Terazosin
- Phentolamine
Correct Answer: Prazosin
Q9. The mechanism of action of dihydroergotamine in migraine involves agonism at which receptor family?
- Serotonin (5-HT) receptors, especially 5-HT1B/1D
- Beta-adrenergic receptors
- Muscarinic acetylcholine receptors
- NMDA glutamate receptors
Correct Answer: Serotonin (5-HT) receptors, especially 5-HT1B/1D
Q10. Which alpha blocker is irreversible and used in pheochromocytoma to control hypertension preoperatively?
- Phenoxybenzamine
- Prazosin
- Doxazosin
- Phentolamine
Correct Answer: Phenoxybenzamine
Q11. Nonselective alpha antagonists (alpha-1 and alpha-2) can cause which compensatory effect?
- Reflex tachycardia due to increased norepinephrine release
- Severe bradycardia due to vagal stimulation
- Hypoglycemia due to increased insulin
- Bronchoconstriction due to histamine release
Correct Answer: Reflex tachycardia due to increased norepinephrine release
Q12. Which property makes prazosin suitable for treating both hypertension and BPH?
- Selective alpha-1 blockade reducing vascular tone and relaxing prostatic smooth muscle
- Alpha-2 agonism leading to decreased sympathetic tone
- Beta-1 selectivity improving cardiac output
- Inhibition of ACE reducing angiotensin II
Correct Answer: Selective alpha-1 blockade reducing vascular tone and relaxing prostatic smooth muscle
Q13. A major contraindication for dihydroergotamine therapy is concomitant use of:
- Strong CYP3A4 inhibitors (e.g., macrolide antibiotics)
- Beta blockers at low dose
- Antacids containing magnesium
- Topical corticosteroids
Correct Answer: Strong CYP3A4 inhibitors (e.g., macrolide antibiotics)
Q14. Which adverse effect is characteristically associated with ergot alkaloids like dihydroergotamine?
- Peripheral ischemia (ergotism)
- Hyperkalemia
- Severe thrombocytopenia
- Photosensitivity rash
Correct Answer: Peripheral ischemia (ergotism)
Q15. The primary pharmacodynamic effect of alpha-1 blockade on vascular smooth muscle is mediated by inhibition of which intracellular pathway?
- Gq → phospholipase C → increased IP3 and Ca2+
- Gs → adenylate cyclase → increased cAMP
- Gi → decreased adenylate cyclase → decreased cAMP
- Tyrosine kinase receptor activation
Correct Answer: Gq → phospholipase C → increased IP3 and Ca2+
Q16. Which of the following is a common central nervous system side effect of dihydroergotamine?
- Nausea and vomiting
- Excessive salivation
- Memory loss
- Insomnia
Correct Answer: Nausea and vomiting
Q17. Terazosin and doxazosin differ from prazosin mainly in:
- Longer half-life allowing once-daily dosing
- Being irreversible antagonists
- Selective alpha-2 blockade
- Higher incidence of reflex tachycardia
Correct Answer: Longer half-life allowing once-daily dosing
Q18. In pharmacology, competitive reversible alpha-1 antagonists produce which type of dose-response shift?
- Rightward shift with increase in EC50 but no change in maximal effect (surmountable)
- Downward shift with decreased maximal effect (insurmountable)
- Leftward shift with increased potency
- No change in dose-response curve
Correct Answer: Rightward shift with increase in EC50 but no change in maximal effect (surmountable)
Q19. Which drug is commonly used intravenously for catecholamine-induced hypertensive crisis due to its nonselective alpha blockade?
- Phentolamine
- Prazosin
- Doxazosin
- Tamsulosin
Correct Answer: Phentolamine
Q20. Blockade of presynaptic alpha-2 receptors would be expected to cause:
- Increased norepinephrine release
- Decreased norepinephrine release
- Increased insulin secretion
- Activation of vagal tone
Correct Answer: Increased norepinephrine release
Q21. Which adverse cardiovascular effect is more likely with nonselective alpha blockers compared to alpha-1 selective agents?
- Reflex tachycardia due to alpha-2 blockade
- Prolonged QT interval
- Bradyarrhythmia due to SA node blockade
- Myocardial infarction due to direct myocardial toxicity
Correct Answer: Reflex tachycardia due to alpha-2 blockade
Q22. A pharmacokinetic property of dihydroergotamine relevant to dosing is:
- Significant first-pass metabolism leading to low oral bioavailability
- Renal excretion as unchanged drug predominantly
- Long half-life suitable for once-weekly dosing
- Activation by prodrug conversion in the liver
Correct Answer: Significant first-pass metabolism leading to low oral bioavailability
Q23. Which of the following is a selective alpha-1A antagonist used to treat BPH with less effect on blood pressure?
- Tamsulosin
- Prazosin
- Phenoxybenzamine
- Phentolamine
Correct Answer: Tamsulosin
Q24. Combining alpha blockers with which drug class increases the risk of severe hypotension?
- PDE5 inhibitors (e.g., sildenafil)
- Loop diuretics
- Statins
- Proton pump inhibitors
Correct Answer: PDE5 inhibitors (e.g., sildenafil)
Q25. Dihydroergotamine’s vasoconstrictive effect is clinically useful in migraine because it:
- Reverses cranial vasodilation and inhibits trigeminal peptide release
- Blocks beta receptors in cerebral vessels
- Promotes CSF turnover
- Enhances central dopamine release to suppress pain
Correct Answer: Reverses cranial vasodilation and inhibits trigeminal peptide release
Q26. Which laboratory or monitoring concern is most relevant when initiating high-dose alpha blockers?
- Blood pressure monitoring for orthostatic changes
- Serum potassium monitoring
- Liver biopsy assessment
- Coagulation profile regularly
Correct Answer: Blood pressure monitoring for orthostatic changes
Q27. Which patient population should avoid dihydroergotamine due to risk of uterine contractions and fetal harm?
- Pregnant women
- Geriatric patients over 65
- Patients with migraine with aura only
- Children under 12
Correct Answer: Pregnant women
Q28. Mechanistically, how do alpha-1 blockers improve urinary flow in BPH?
- Relaxation of prostatic and bladder neck smooth muscle
- Reduction of prostate size by inhibiting cell proliferation
- Increased diuresis to flush urethra
- Stimulation of detrusor contractility
Correct Answer: Relaxation of prostatic and bladder neck smooth muscle
Q29. Which drug interaction with dihydroergotamine can produce severe peripheral ischemia and gangrene?
- CYP3A4 inhibitors (e.g., grapefruit juice, macrolides)
- ACE inhibitors
- Thiazide diuretics
- Low-dose aspirin
Correct Answer: CYP3A4 inhibitors (e.g., grapefruit juice, macrolides)
Q30. Which alpha blocker is competitive and reversible, used occasionally for diagnosis and treatment of catecholamine excess?
- Phentolamine
- Phenoxybenzamine
- Tamsulosin
- Doxazosin
Correct Answer: Phentolamine
Q31. Which sign indicates an adverse vascular reaction to ergot therapy that requires immediate discontinuation?
- Severe cold, pale, painful extremities (signs of peripheral ischemia)
- Transient mild headache improvement
- Increased appetite
- Mild transient hypertension
Correct Answer: Severe cold, pale, painful extremities (signs of peripheral ischemia)
Q32. Which statement about tamsulosin is correct?
- It is more selective for alpha-1A receptors and has less orthostatic hypotension
- It irreversibly blocks alpha receptors
- It is primarily used as an intravenous antihypertensive
- It is a central alpha-2 agonist
Correct Answer: It is more selective for alpha-1A receptors and has less orthostatic hypotension
Q33. In pharmacology exams, the ‘first-dose phenomenon’ with alpha blockers is attributed to:
- Sudden profound vasodilation and pooling of blood on first administration
- Accumulation of drug metabolites on first day
- Activation of the renin-angiotensin system exclusively
- Immediate tachyphylaxis reducing effect
Correct Answer: Sudden profound vasodilation and pooling of blood on first administration
Q34. Which of the following best describes the effect of alpha-1 blockade on peripheral resistance and cardiac output?
- Decrease in peripheral resistance with possible reflex increase in heart rate and cardiac output
- Increase in peripheral resistance and decreased cardiac output
- No change in peripheral resistance but decreased stroke volume
- Direct increase in myocardial contractility without vascular effects
Correct Answer: Decrease in peripheral resistance with possible reflex increase in heart rate and cardiac output
Q35. Dihydroergotamine is contraindicated in patients with which vascular condition?
- Peripheral vascular disease
- Essential tremor
- Chronic sinusitis
- Iron deficiency anemia
Correct Answer: Peripheral vascular disease
Q36. Which metabolic enzyme system is primarily responsible for dihydroergotamine clearance?
- CYP3A4
- CYP2D6
- Monoamine oxidase
- Glucuronosyltransferase exclusively
Correct Answer: CYP3A4
Q37. Which adverse effect is commonly reported with alpha-1 blockers due to increased nasal mucosal blood flow?
- Nasal congestion
- Dry mouth
- Blurred vision
- Constipation
Correct Answer: Nasal congestion
Q38. When studying receptor pharmacology, an irreversible antagonist like phenoxybenzamine causes:
- Long-lasting blockade until new receptors are synthesized
- Immediate surmountable inhibition overcome by high agonist concentration
- Short duration of action with quick offset
- Selective blockade of beta receptors only
Correct Answer: Long-lasting blockade until new receptors are synthesized
Q39. Which dihydroergotamine characteristic explains why it should not be combined with potent vasoconstrictors?
- Its intrinsic vasoconstrictive properties via 5-HT and alpha receptors
- Its potent diuretic activity
- Its ability to increase nitric oxide synthesis
- Its anticoagulant effect
Correct Answer: Its intrinsic vasoconstrictive properties via 5-HT and alpha receptors
Q40. Which clinical scenario is an appropriate use of an alpha-1 blocker?
- Symptomatic benign prostatic hyperplasia with urinary retention
- First-line therapy for heart failure with reduced ejection fraction
- Chronic management of asthma
- Treatment of acute bacterial infection
Correct Answer: Symptomatic benign prostatic hyperplasia with urinary retention
Q41. Which monitoring advice is important for a patient starting prazosin?
- Take the first dose at bedtime and monitor for orthostatic symptoms
- Avoid drinking water for 12 hours after dosing
- Check fasting blood glucose every hour
- Increase salt intake immediately
Correct Answer: Take the first dose at bedtime and monitor for orthostatic symptoms
Q42. An MCQ question on drug interactions: combining alpha blockers with beta blockers may lead to:
- Unopposed alpha-mediated vasoconstriction if beta blockade is predominant
- Synergistic alpha agonism
- Marked hyperglycemia exacerbation
- Complete neutralization of effects with no clinical change
Correct Answer: Unopposed alpha-mediated vasoconstriction if beta blockade is predominant
Q43. The mechanism underlying ergot-induced nausea is most closely related to:
- Dopamine receptor agonism in the chemoreceptor trigger zone
- Anticholinergic blockade of muscarinic receptors
- Excess serotonin in peripheral GI receptors only
- Direct irritation of gastric mucosa only
Correct Answer: Dopamine receptor agonism in the chemoreceptor trigger zone
Q44. Which property of doxazosin makes it convenient for hypertension therapy?
- Once-daily dosing due to longer half-life
- Intravenous formulation for emergency use
- High beta receptor affinity
- Renal excretion requiring dose adjustment in liver failure
Correct Answer: Once-daily dosing due to longer half-life
Q45. Which of the following best describes the therapeutic index concern when combining dihydroergotamine with potent CYP3A4 inhibitors?
- Increased plasma levels raise risk of vasospasm and ischemia
- Decreased efficacy leading to treatment failure
- Rapid clearance and shorter duration of action
- Enhanced renal elimination with diuresis
Correct Answer: Increased plasma levels raise risk of vasospasm and ischemia
Q46. Which receptor action contributes to the antimigraine effect of dihydroergotamine beyond vasoconstriction?
- Inhibition of trigeminal nerve peptide release via 5-HT1D receptors
- Beta-2 receptor mediated bronchodilation
- Alpha-1 mediated increased renal perfusion
- Muscarinic receptor blockade in the cortex
Correct Answer: Inhibition of trigeminal nerve peptide release via 5-HT1D receptors
Q47. Which statement about dosage forms of dihydroergotamine is correct?
- Parenteral and intranasal forms are preferred due to poor oral bioavailability
- Oral tablets are standard for acute migraine
- Transdermal patches provide immediate relief
- Topical creams are effective for migraine
Correct Answer: Parenteral and intranasal forms are preferred due to poor oral bioavailability
Q48. In receptor pharmacology, selectivity of alpha-1A vs alpha-1B subtypes is clinically relevant because:
- Alpha-1A selectivity improves urinary symptoms with less systemic hypotension
- Alpha-1A selectivity causes greater hepatic toxicity
- Alpha-1B selectivity exclusively effects prostate tissue
- Subtype selectivity has no practical clinical relevance
Correct Answer: Alpha-1A selectivity improves urinary symptoms with less systemic hypotension
Q49. A pharmacist counseling a patient on dihydroergotamine should warn about which urgent symptom requiring medical attention?
- Severe limb pain and discoloration suggesting ischemia
- Mild transient thirst
- Temporary taste disturbance
- Benign mild hair loss
Correct Answer: Severe limb pain and discoloration suggesting ischemia
Q50. Which pharmacological principle is demonstrated when alpha-1 antagonists reduce blood pressure but may increase heart rate?
- Reflex sympathetic activation secondary to vasodilation
- Direct stimulation of sinoatrial node by the drug
- Inhibition of renin release leading to tachycardia
- Enhanced vagal tone producing tachycardia
Correct Answer: Reflex sympathetic activation secondary to vasodilation
