Cholinesterase inhibitors – reversible MCQs With Answer

Cholinesterase inhibitors – reversible MCQs With Answer

Reversible cholinesterase inhibitors are key drugs studied in B.Pharm pharmacology, covering acetylcholinesterase and butyrylcholinesterase inhibition, mechanisms of action, pharmacokinetics, and clinical applications. This SEO-friendly introduction highlights important keywords like cholinesterase inhibitors, reversible cholinesterase inhibitors, B.Pharm, MCQs, acetylcholinesterase, myasthenia gravis, Alzheimer’s therapy, and adverse effects. The content emphasizes distinctions between edrophonium, carbamates (neostigmine, pyridostigmine), and tertiary amines (physostigmine, donepezil), CNS penetration, drug interactions, monitoring, and therapeutic rationale. It’s designed to help B.Pharm students deepen understanding and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which of the following is a short-acting reversible cholinesterase inhibitor commonly used in the diagnostic edrophonium test for myasthenia gravis?

• Neostigmine
• Edrophonium
• Pyridostigmine
• Donepezil

Correct Answer: Edrophonium

Q2. Carbamate inhibitors such as neostigmine inhibit acetylcholinesterase by which mechanism?

• Covalent phosphorylation of serine residue
• Reversible electrostatic binding only
• Carbamylation of the active site serine
• Allosteric modulation at peripheral site

Correct Answer: Carbamylation of the active site serine

Q3. Which reversible cholinesterase inhibitor readily crosses the blood–brain barrier due to its tertiary amine structure and is used in Alzheimer’s disease?

• Neostigmine
• Rivastigmine
• Pyridostigmine
• Edrophonium

Correct Answer: Rivastigmine

Q4. Which of the following best distinguishes reversible from irreversible cholinesterase inhibitors?

• Reversible inhibitors permanently phosphorylate the enzyme
• Reversible inhibitors form non-permanent interactions permitting enzyme recovery
• Reversible inhibitors only affect butyrylcholinesterase
• Reversible inhibitors have longer duration than organophosphates

Correct Answer: Reversible inhibitors form non-permanent interactions permitting enzyme recovery

Q5. Which adverse effect is most characteristic of cholinesterase inhibitor toxicity?

• Hyperthermia and dry skin
• Anticholinergic syndrome
• SLUDGE symptoms (salivation, lacrimation, urination, defecation, GI upset, emesis)
• Hypersomnolence without autonomic signs

Correct Answer: SLUDGE symptoms (salivation, lacrimation, urination, defecation, GI upset, emesis)

Q6. Pyridostigmine is preferred over neostigmine for long-term management of myasthenia gravis because:

• It is more lipid soluble and crosses BBB
• It has a longer duration of action and fewer CNS effects
• It irreversibly inhibits acetylcholinesterase
• It selectively inhibits butyrylcholinesterase only

Correct Answer: It has a longer duration of action and fewer CNS effects

Q7. Which reversible inhibitor is used topically in glaucoma to increase aqueous outflow by contracting the iris sphincter?

• Physostigmine
• Donepezil
• Rivastigmine
• Pyridostigmine

Correct Answer: Physostigmine

Q8. Edrophonium’s duration of action is short because its binding to acetylcholinesterase is primarily:

• Covalent and permanent
• Noncovalent and reversible
• Carbamylating and long-lasting
• Irreversible phosphorylation

Correct Answer: Noncovalent and reversible

Q9. Which cholinesterase inhibitor is a tertiary amine used in Alzheimer’s disease and also acts as an allosteric potentiator of nicotinic receptors?

• Galantamine
• Neostigmine
• Pyridostigmine
• Edrophonium

Correct Answer: Galantamine

Q10. Which statement about neostigmine is correct regarding its pharmacologic properties?

• It is a tertiary amine that crosses the BBB easily
• It is a quaternary ammonium compound with poor CNS penetration
• It is used primarily for Alzheimer’s disease
• It irreversibly inhibits acetylcholinesterase

Correct Answer: It is a quaternary ammonium compound with poor CNS penetration

Q11. In organophosphate poisoning causing irreversible AChE inhibition, which drug is used to reactivate AChE but is not effective for carbamate-inhibited AChE?

• Atropine
• Pralidoxime (2-PAM)
• Neostigmine
• Physostigmine

Correct Answer: Pralidoxime (2-PAM)

Q12. Which lab assay measures plasma pseudocholinesterase (butyrylcholinesterase) activity commonly affected by some cholinesterase inhibitors?

• Serum AST/ALT
• Plasma cholinesterase (Butyrylcholinesterase) assay
• Serum creatinine kinase
• Complete blood count

Correct Answer: Plasma cholinesterase (Butyrylcholinesterase) assay

Q13. Which reversible cholinesterase inhibitor is used to reverse residual neuromuscular blockade after non-depolarizing muscle relaxants in anesthesia?

• Edrophonium or neostigmine
• Atropine alone
• Succinylcholine
• Donepezil

Correct Answer: Edrophonium or neostigmine

Q14. Which property determines a cholinesterase inhibitor’s ability to affect central cholinergic pathways?

• Affinity for muscarinic receptors
• Lipid solubility and tertiary amine status
• Rate of renal excretion only
• Ability to carbamylate butyrylcholinesterase exclusively

Correct Answer: Lipid solubility and tertiary amine status

Q15. Donepezil primarily inhibits which enzyme isoform in Alzheimer’s therapy?

• Butyrylcholinesterase only
• Acetylcholinesterase (CNS predominant)
• Monoamine oxidase
• Choline acetyltransferase

Correct Answer: Acetylcholinesterase (CNS predominant)

Q16. Which of the following interactions is a clinical concern when a patient on cholinesterase inhibitors receives succinylcholine?

• Accelerated metabolism of succinylcholine
• Prolongation of succinylcholine effect due to inhibited pseudocholinesterase
• Complete antagonism of succinylcholine action
• No interaction is expected

Correct Answer: Prolongation of succinylcholine effect due to inhibited pseudocholinesterase

Q17. Which cholinesterase inhibitor can be given orally for symptomatic treatment of myasthenia gravis with fewer dosing intervals?

• Edrophonium
• Pyridostigmine
• Physostigmine
• Pralidoxime

Correct Answer: Pyridostigmine

Q18. Which adverse cardiovascular effect can occur with systemic cholinesterase inhibitor overdose?

• Tachycardia without bradycardia
• Bradycardia and conduction block due to excessive vagal stimulation
• Hypertensive crisis
• Isolated QT prolongation only

Correct Answer: Bradycardia and conduction block due to excessive vagal stimulation

Q19. What is the primary therapeutic rationale for using reversible cholinesterase inhibitors in Alzheimer’s disease?

• To increase dopamine levels in cortex
• To enhance cholinergic transmission by increasing synaptic acetylcholine
• To inhibit amyloid plaque formation directly
• To block NMDA receptors

Correct Answer: To enhance cholinergic transmission by increasing synaptic acetylcholine

Q20. Which reversible inhibitor is often used topically in the eye but can cross the BBB and treat severe anticholinergic toxicity?

• Neostigmine
• Physostigmine
• Pyridostigmine
• Rivastigmine

Correct Answer: Physostigmine

Q21. Which statement about edrophonium testing is true?

• It permanently cures myasthenia gravis
• Improvement in muscle strength after edrophonium suggests myasthenic rather than cholinergic crisis
• It is the definitive test for Alzheimer’s disease
• It is used to treat organophosphate poisoning

Correct Answer: Improvement in muscle strength after edrophonium suggests myasthenic rather than cholinergic crisis

Q22. Which reversible cholinesterase inhibitor has dual inhibition of acetylcholinesterase and butyrylcholinesterase and is used in Alzheimer’s?

• Neostigmine
• Rivastigmine
• Edrophonium
• Succinylcholine

Correct Answer: Rivastigmine

Q23. Which of the following is a clinical contraindication to giving cholinesterase inhibitors?

• Asthma or COPD with active bronchospasm
• Myasthenia gravis
• Alzheimer’s disease
• Postoperative urinary retention

Correct Answer: Asthma or COPD with active bronchospasm

Q24. Which structural feature typically reduces CNS penetration of cholinesterase inhibitors?

• Tertiary amine and lipophilicity
• Quaternary ammonium group and high polarity
• Small molecular weight and lipophilicity
• Strong binding to plasma albumin

Correct Answer: Quaternary ammonium group and high polarity

Q25. In enzyme kinetics, reversible cholinesterase inhibitors that compete with acetylcholine for the active site are classified as:

• Noncompetitive inhibitors
• Competitive inhibitors
• Irreversible inhibitors
• Suicide substrates

Correct Answer: Competitive inhibitors

Q26. Which clinical monitoring parameter is most important when initiating a cholinesterase inhibitor in elderly Alzheimer’s patients?

• Serum potassium only
• Heart rate and signs of bradycardia or syncope
• Fasting glucose exclusively
• Arterial blood gases routinely

Correct Answer: Heart rate and signs of bradycardia or syncope

Q27. Which reversible inhibitor is known to cause peripheral cholinergic adverse effects like diarrhea and nausea, limiting tolerability?

• Donepezil
• Rivastigmine and donepezil (both can cause GI side effects)
• Pralidoxime
• Atropine

Correct Answer: Rivastigmine and donepezil (both can cause GI side effects)

Q28. Which of the following best explains why neostigmine does not improve central cognitive symptoms in Alzheimer’s disease?

• It selectively increases GABAergic transmission
• It is a quaternary ammonium that poorly crosses the blood–brain barrier
• It is rapidly metabolized to an inactive metabolite in the CNS
• It irreversibly destroys acetylcholine

Correct Answer: It is a quaternary ammonium that poorly crosses the blood–brain barrier

Q29. Which reversible inhibitor is used in neuropathic pain and dementia but has transdermal formulations to reduce GI adverse effects?

• Rivastigmine (transdermal patch available)
• Edrophonium
• Neostigmine
• Pyridostigmine

Correct Answer: Rivastigmine (transdermal patch available)

Q30. Which pharmacokinetic factor is crucial when choosing between neostigmine and pyridostigmine for myasthenia gravis?

• Route of metabolism by CYP450 only
• Duration of action and oral bioavailability
• Ability to irreversibly inhibit AChE
• Renal tubular secretion exclusively

Correct Answer: Duration of action and oral bioavailability

Q31. Which clinical sign helps differentiate cholinergic crisis from myasthenic crisis?

• Improvement with additional cholinesterase inhibitor indicates cholinergic crisis
• Worsening with edrophonium suggests cholinergic crisis, improvement suggests myasthenic crisis
• Presence of hyperreflexia only
• Both crises are clinically identical and indistinguishable

Correct Answer: Worsening with edrophonium suggests cholinergic crisis, improvement suggests myasthenic crisis

Q32. Which enzyme primarily degrades acetylcholine in the synaptic cleft of neuromuscular junctions?

• Monoamine oxidase
• Acetylcholinesterase
• Butyrylcholinesterase exclusively
• Choline acetyltransferase

Correct Answer: Acetylcholinesterase

Q33. Which agent is useful to treat organophosphate-induced muscarinic symptoms but does not reactivate phosphorylated AChE?

• Atropine
• Pralidoxime
• Neostigmine
• Physostigmine

Correct Answer: Atropine

Q34. Which reversible inhibitor can be used systemically to treat urinary retention due to postoperative atony?

• Atropine
• Neostigmine
• Donepezil
• Pralidoxime

Correct Answer: Neostigmine

Q35. Which concept explains why carbamate inhibitors have intermediate duration of action compared to edrophonium and organophosphates?

• Carbamylated enzyme undergoes slow spontaneous hydrolysis, allowing recovery
• Carbamates irreversibly phosphorylate enzyme
• Carbamates are not enzyme inhibitors but receptor agonists
• Carbamylation permanently denatures the enzyme

Correct Answer: Carbamylated enzyme undergoes slow spontaneous hydrolysis, allowing recovery

Q36. Which adverse effect is more likely with cholinesterase inhibitors that penetrate the CNS?

• Peripheral neuropathy only
• Agitation, insomnia, vivid dreams, or delirium
• Isolated hypertension
• Renal failure

Correct Answer: Agitation, insomnia, vivid dreams, or delirium

Q37. Which monitoring parameter is most useful when patients start rivastigmine or donepezil therapy?

• Liver enzymes exclusively
• Weight, GI symptoms, heart rate, and blood pressure
• Serum sodium only
• Pulmonary function tests routinely

Correct Answer: Weight, GI symptoms, heart rate, and blood pressure

Q38. Which of the following is true about butyrylcholinesterase (pseudocholinesterase)?

• It is the primary enzyme at neuromuscular junctions
• It hydrolyzes succinylcholine and is found in plasma and liver
• It is exclusively neuronal and absent peripherally
• It synthesizes acetylcholine from choline and acetate

Correct Answer: It hydrolyzes succinylcholine and is found in plasma and liver

Q39. Which drug interaction increases the risk of cholinergic adverse effects when combined with cholinesterase inhibitors?

• Concomitant anticholinergics like oxybutynin
• Beta-blockers that reduce heart rate
• Concurrent use of cholinergic agonists or drugs that increase cholinergic tone
• Loop diuretics only

Correct Answer: Concurrent use of cholinergic agonists or drugs that increase cholinergic tone

Q40. In which situation is physostigmine contraindicated?

• Severe asthma with bronchospasm
• Anticholinergic toxicity with severe agitation
• Alzheimer’s mild cognitive impairment
• Glaucoma treatment when needed topically

Correct Answer: Severe asthma with bronchospasm

Q41. Which reversible inhibitor would you choose for symptomatic relief of muscle weakness in a patient who cannot tolerate high-frequency dosing?

• Edrophonium due to long duration
• Pyridostigmine for longer duration of action
• Physostigmine for peripheral-only effect
• Pralidoxime for symptomatic relief

Correct Answer: Pyridostigmine for longer duration of action

Q42. Which pharmacodynamic effect describes galantamine’s additional action beyond AChE inhibition?

• NMDA receptor antagonism
• Allosteric modulation of nicotinic acetylcholine receptors
• Beta-adrenergic blockade
• GABA-A receptor agonism

Correct Answer: Allosteric modulation of nicotinic acetylcholine receptors

Q43. Which is a valid counselling point for patients starting oral pyridostigmine?

• Take on an empty stomach to decrease absorption
• Take 30 minutes before meals to improve muscle strength during eating
• Avoid reporting any GI symptoms as they are unrelated
• Stop medication abruptly if symptoms persist

Correct Answer: Take 30 minutes before meals to improve muscle strength during eating

Q44. Which diagnostic change in electrophysiology supports efficacy of cholinesterase inhibitor therapy in myasthenia gravis?

• Decreased jitter on single-fiber EMG after dosing
• Increased resting muscle membrane potential
• Complete block of neuromuscular transmission
• Loss of compound muscle action potentials permanently

Correct Answer: Decreased jitter on single-fiber EMG after dosing

Q45. A patient with Alzheimer’s on donepezil complains of vivid dreams and insomnia. What is the likely cause?

• Anticholinergic side effect of donepezil
• CNS cholinergic stimulation from donepezil crossing the BBB
• Drug-induced hepatotoxicity
• Dehydration

Correct Answer: CNS cholinergic stimulation from donepezil crossing the BBB

Q46. Which reversible cholinesterase inhibitor is most suitable for a patient with impaired renal function requiring Alzheimer treatment?

• Galantamine without dose adjustment
• Rivastigmine which has hepatic metabolism and transdermal option
• Pyridostigmine exclusively
• Edrophonium for chronic therapy

Correct Answer: Rivastigmine which has hepatic metabolism and transdermal option

Q47. What is the effect of cholinesterase inhibitors on ventilatory function in severe overdose?

• Bronchodilation and improved ventilation
• Bronchoconstriction, increased secretions, and potential respiratory failure
• No effect on respiratory system
• Only central respiratory stimulation without peripheral effects

Correct Answer: Bronchoconstriction, increased secretions, and potential respiratory failure

Q48. For exam preparation, which concept about cholinesterase inhibitors is most important for B.Pharm students to understand?

• Only their chemical names without clinical correlations
• Mechanism of enzyme inhibition, clinical uses, adverse effects, and interactions
• That all are interchangeable and have identical profiles
• That they cure neurodegenerative diseases permanently

Correct Answer: Mechanism of enzyme inhibition, clinical uses, adverse effects, and interactions

Q49. Which reversible inhibitor is least likely to produce significant bradycardia because of peripheral selectivity and limited CNS penetration?

• Donepezil
• Neostigmine
• Galantamine
• Rivastigmine

Correct Answer: Neostigmine

Q50. Which practical laboratory parameter may be useful in monitoring toxicity or exposure to cholinesterase inhibitors or organophosphates in occupational settings?

• Plasma butyrylcholinesterase activity and red blood cell acetylcholinesterase activity
• Serum troponin only
• Urine pH exclusively
• Fasting blood glucose only

Correct Answer: Plasma butyrylcholinesterase activity and red blood cell acetylcholinesterase activity

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.

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