Guanethidine monosulphate MCQs With Answer

Guanethidine monosulphate MCQs With Answer

Guanethidine monosulphate is a classical sympatholytic antihypertensive that depletes neuronal norepinephrine and inhibits its release. This MCQ set for B. Pharm students focuses on mechanism of action, pharmacokinetics, routes of administration, clinical indications, adverse effects, contraindications and drug interactions of guanethidine monosulphate. Questions emphasize uptake-1 dependence, effects on peripheral sympathetic tone, monitoring parameters, and implications for patient counseling. Detailed items test understanding of formulation, dosing considerations, metabolic handling, and common toxicities such as orthostatic hypotension, diarrhoea and sexual dysfunction. These practice questions are designed to strengthen pharmacology knowledge, exam readiness and clinical application skills. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary mechanism of action of guanethidine monosulphate?

• Direct blockade of adrenergic receptors on blood vessels
• Inhibition of catecholamine synthesis enzymes
• Uptake into sympathetic neurons and depletion of norepinephrine stores
• Central α2‑adrenergic receptor agonism reducing sympathetic outflow

Correct Answer: Uptake into sympathetic neurons and depletion of norepinephrine stores

Q2. Which transport process is essential for guanethidine to reach its site of action in sympathetic neurons?

• Passive diffusion across the blood–brain barrier
• Uptake‑1 (neuronal norepinephrine transporter)
• P-glycoprotein mediated efflux
• Organic anion transporter 1 (OAT1)

Correct Answer: Uptake‑1 (neuronal norepinephrine transporter)

Q3. For which clinical indication was guanethidine most commonly used historically?

• Angina pectoris
• Severe refractory hypertension
• Heart failure with reduced ejection fraction
• Chronic stable asthma

Correct Answer: Severe refractory hypertension

Q4. Which adverse effect is most characteristically associated with guanethidine therapy?

• Bronchospasm
• Orthostatic hypotension
• Hypoglycemia
• Tardive dyskinesia

Correct Answer: Orthostatic hypotension

Q5. Which drug class reduces the antihypertensive efficacy of guanethidine by blocking its neuronal uptake?

• ACE inhibitors
• Tricyclic antidepressants
• Calcium channel blockers
• Thiazide diuretics

Correct Answer: Tricyclic antidepressants

Q6. Which of the following best describes guanethidine’s effect on sympathetic nerve terminals?

• Enhances vesicular release of norepinephrine
• Competes with norepinephrine at postsynaptic receptors
• Accumulates in vesicles and displaces stored norepinephrine
• Blocks synthesis of dopamine from tyrosine

Correct Answer: Accumulates in vesicles and displaces stored norepinephrine

Q7. Which statement about guanethidine pharmacokinetics is most accurate?

• It is rapidly metabolized by hepatic CYP450 enzymes to active metabolites
• It readily crosses the blood–brain barrier producing central sedation
• It is poorly absorbed orally and is largely excreted unchanged in urine
• It is primarily eliminated via biliary excretion

Correct Answer: It is poorly absorbed orally and is largely excreted unchanged in urine

Q8. Why can guanethidine cause fluid retention and oedema in some patients?

• It stimulates aldosterone secretion directly from the adrenal cortex
• Reduced sympathetic renal tone leads to increased sodium and water retention
• It causes antidiuretic hormone (ADH) release from the posterior pituitary
• It acts as a mineralocorticoid agonist in the kidney

Correct Answer: Reduced sympathetic renal tone leads to increased sodium and water retention

Q9. Which side effect commonly impacts quality of life and sexual function in male patients on guanethidine?

• Priapism
• Retrograde ejaculation
• Impotence (erectile dysfunction)
• Hypoactive sexual desire disorder

Correct Answer: Impotence (erectile dysfunction)

Q10. A patient on guanethidine develops severe postural hypotension. Which counselling point is most appropriate?

• Avoid grapefruit juice while taking the drug
• Rise slowly from sitting or lying positions to reduce dizziness
• Increase physical exertion to improve tolerance
• Stop all other antihypertensive drugs immediately

Correct Answer: Rise slowly from sitting or lying positions to reduce dizziness

Q11. Combining guanethidine with which drug would most likely produce an unpredictable pressor response?

• Tricyclic antidepressants
• Phenylephrine (direct sympathomimetic)
• Nitroprusside
• Hydrochlorothiazide

Correct Answer: Phenylephrine (direct sympathomimetic)

Q12. Which laboratory or clinical parameter should be monitored in patients receiving guanethidine?

• Fasting lipid profile every week
• Orthostatic blood pressure and heart rate
• Serum bilirubin monthly
• Pulmonary function tests

Correct Answer: Orthostatic blood pressure and heart rate

Q13. What is a major pharmacodynamic distinction between guanethidine and reserpine?

• Guanethidine blocks postsynaptic receptors; reserpine blocks uptake-1
• Guanethidine requires neuronal uptake and acts peripherally; reserpine inhibits vesicular storage via VMAT
• Both drugs have identical mechanisms and side effect profiles
• Reserpine enhances norepinephrine release, while guanethidine inhibits release

Correct Answer: Guanethidine requires neuronal uptake and acts peripherally; reserpine inhibits vesicular storage via VMAT

Q14. Which patient condition is a relative contraindication to starting guanethidine?

• Controlled essential hypertension on monotherapy
• History of severe orthostatic hypotension
• Mild seasonal allergic rhinitis
• Well‑controlled type 2 diabetes mellitus

Correct Answer: History of severe orthostatic hypotension

Q15. How does guanethidine alter the amplitude of sympathetic nerve impulses reaching the vasculature?

• Increases nerve conduction velocity leading to tachycardia
• Stabilizes membranes preventing norepinephrine release on nerve stimulation
• Enhances synaptic cleft norepinephrine concentration
• Directly blocks voltage‑gated calcium channels on vascular smooth muscle

Correct Answer: Stabilizes membranes preventing norepinephrine release on nerve stimulation

Q16. What effect does guanethidine have on resting heart rate in most patients?

• Marked reflex tachycardia in all patients
• Little or no reflex tachycardia due to sympathetic blockade
• Profound bradycardia requiring pacemaker insertion
• Immediate arrhythmogenic effect leading to atrial fibrillation

Correct Answer: Little or no reflex tachycardia due to sympathetic blockade

Q17. Which description best fits the onset of antihypertensive effect with guanethidine therapy?

• Immediate effect within minutes after a single dose
• Delayed onset over days as neuronal norepinephrine stores are depleted
• Onset only after co‑administration with an ACE inhibitor
• Effect only when administered intracerebroventricularly

Correct Answer: Delayed onset over days as neuronal norepinephrine stores are depleted

Q18. Which adverse gastrointestinal effect is frequently reported with guanethidine?

• Constipation resistant to laxatives
• Diarrhoea due to altered autonomic gut regulation
• Peptic ulcer formation within days
• Pancreatitis

Correct Answer: Diarrhoea due to altered autonomic gut regulation

Q19. If a patient on guanethidine requires surgery, what perioperative concern is most relevant?

• Risk of excessive bleeding due to platelet dysfunction
• Pronounced hypotension with anesthesia and reduced sympathetic compensatory responses
• Increased risk of thromboembolism due to hypercoagulability
• Unpredictable hypoglycemia during fasting

Correct Answer: Pronounced hypotension with anesthesia and reduced sympathetic compensatory responses

Q20. Which patient counseling point is important regarding sudden withdrawal of guanethidine?

• Sudden withdrawal causes severe hypertension due to rebound sympathetic activity
• Drug must be stopped abruptly to avoid side effects
• There are no withdrawal-related effects
• Withdrawal leads to permanent loss of blood pressure control

Correct Answer: Sudden withdrawal causes severe hypertension due to rebound sympathetic activity

Q21. Which laboratory test is most likely to be useful if a patient develops unexplained fainting on guanethidine?

• Orthostatic blood pressure measurement
• Liver function tests
• Serum amylase
• Pulmonary function testing

Correct Answer: Orthostatic blood pressure measurement

Q22. What interaction might occur if guanethidine is coadministered with a beta‑blocker?

• The beta‑blocker prevents guanethidine uptake into neurons
• Enhanced hypotension and potential bradycardia due to additive autonomic blockade
• Complete antagonism of guanethidine’s antihypertensive effect
• Increased risk of serotonin syndrome

Correct Answer: Enhanced hypotension and potential bradycardia due to additive autonomic blockade

Q23. Which formulation of guanethidine monosulphate is commonly referenced in clinical use?

• Topical cream for local vasodilation
• Parenteral injectable salt (monosulphate) and oral salts historically
• Transdermal patch for chronic pain
• Inhaled aerosol for pulmonary hypertension

Correct Answer: Parenteral injectable salt (monosulphate) and oral salts historically

Q24. Which of the following best explains reduced efficacy of guanethidine when combined with cocaine?

• Cocaine increases renal excretion of guanethidine
• Cocaine blocks neuronal uptake-1, preventing guanethidine entry into nerve endings
• Cocaine induces metabolism of guanethidine via CYP3A4
• Cocaine enhances guanethidine uptake leading to toxicity

Correct Answer: Cocaine blocks neuronal uptake-1, preventing guanethidine entry into nerve endings

Q25. In which physiological system does guanethidine primarily act to lower blood pressure?

• Central nervous system via medullary depression
• Peripheral sympathetic nervous system at postganglionic nerve terminals
• Renin–angiotensin–aldosterone system by inhibiting renin directly
• Parasympathetic ganglia by enhancing acetylcholine release

Correct Answer: Peripheral sympathetic nervous system at postganglionic nerve terminals

Q26. Which symptom indicates excessive autonomic blockade from guanethidine in the elderly?

• Excessive sweating while active
• Frequent falls due to orthostatic dizziness
• Impaired hearing
• Uncontrolled cough

Correct Answer: Frequent falls due to orthostatic dizziness

Q27. Which statement about guanethidine and pregnancy is most appropriate for B. Pharm counselling?

• It is first‑line antihypertensive in pregnancy
• Use in pregnancy requires careful risk–benefit assessment and specialist input
• It is absolutely safe and requires no monitoring in pregnancy
• It enhances fetal growth when taken during pregnancy

Correct Answer: Use in pregnancy requires careful risk–benefit assessment and specialist input

Q28. Which pharmacological property explains why guanethidine has limited central nervous system side effects?

• High lipid solubility leading to rapid CNS clearance
• Poor penetration of the blood–brain barrier
• Selective blockade of central α1 receptors only
• Strong inhibition of central monoamine oxidase

Correct Answer: Poor penetration of the blood–brain barrier

Q29. What practical measure can reduce the risk of orthostatic hypotension in a patient starting guanethidine?

• Recommend standing quickly after getting out of bed
• Start at a low dose and titrate slowly while monitoring blood pressure
• Combine with another sympatholytic from the first day
• Advise a low‑salt diet immediately

Correct Answer: Start at a low dose and titrate slowly while monitoring blood pressure

Q30. Which clinical finding suggests guanethidine is producing its intended pharmacologic effect?

• Marked increase in resting tremor
• Reduction in standing and supine blood pressure with diminished sympathetic responses
• Elevation of fasting blood glucose
• Persistent tachycardia and diaphoresis

Correct Answer: Reduction in standing and supine blood pressure with diminished sympathetic responses

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com