Reversible inhibitors – Ambenonium chloride MCQs With Answer

Reversible inhibitors – Ambenonium chloride MCQs With Answer

Ambenonium chloride is an important reversible acetylcholinesterase (AChE) inhibitor studied in B.Pharm pharmacology. This quaternary ammonium drug is commonly associated with management of myasthenia gravis and illustrates key concepts: mechanism of action, pharmacokinetics (poor CNS penetration, oral use), therapeutic dosing, adverse effects (muscarinic and nicotinic), contraindications, and drug interactions. Understanding ambenonium deepens knowledge of cholinergic transmission, cholinesterase inhibition kinetics, and clinical decision-making. These focused, exam-oriented MCQs emphasize mechanism, clinical use, safety monitoring, and comparison with other AChE inhibitors to prepare B.Pharm students for practical and theoretical questions. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which enzyme is directly inhibited by ambenonium chloride?

• Butyrylcholinesterase
• Monoamine oxidase
• Acetylcholinesterase
• Choline acetyltransferase

Correct Answer: Acetylcholinesterase

Q2. Ambenonium chloride is classified as a:

• irreversible organophosphate
• reversible acetylcholinesterase inhibitor
• muscarinic antagonist
• nicotinic receptor blocker

Correct Answer: reversible acetylcholinesterase inhibitor

Q3. The primary therapeutic use of ambenonium chloride is:

• Alzheimer’s disease
• Glaucoma
• Myasthenia gravis
• Parksinson’s disease

Correct Answer: Myasthenia gravis

Q4. Which property explains poor central nervous system (CNS) penetration of ambenonium?

• High lipid solubility
• It is a quaternary ammonium compound
• Strong protein binding in plasma
• Rapid hepatic metabolism

Correct Answer: It is a quaternary ammonium compound

Q5. Compared to edrophonium, ambenonium generally has:

• a shorter duration of action
• no clinical cholinergic effects
• a longer duration of action
• greater CNS penetration

Correct Answer: a longer duration of action

Q6. The predominant autonomic adverse effects of ambenonium are due to stimulation of:

• alpha-adrenergic receptors
• beta-adrenergic receptors
• muscarinic receptors
• histamine receptors

Correct Answer: muscarinic receptors

Q7. A common muscarinic side effect of ambenonium is:

• dry mouth
• constipation
• bradycardia
• urinary retention

Correct Answer: bradycardia

Q8. Which medication is commonly used to counteract muscarinic toxicity from ambenonium?

• Propranolol
• Atropine
• Physostigmine
• Pilocarpine

Correct Answer: Atropine

Q9. Ambenonium’s effect at the neuromuscular junction primarily increases:

• acetylcholine release from presynaptic terminals
• acetylcholine concentration in the synaptic cleft
• choline acetyltransferase activity
• adrenergic transmission

Correct Answer: acetylcholine concentration in the synaptic cleft

Q10. Which statement about the absorption of oral ambenonium is correct?

• Well absorbed and crosses BBB easily
• Poorly absorbed due to quaternary structure
• Only effective if given intravenously
• Absorption unaffected by food

Correct Answer: Poorly absorbed due to quaternary structure

Q11. In myasthenia gravis, ambenonium is mainly used for:

• short diagnostic testing
• long-term symptomatic control
• immunosuppression
• treating infection

Correct Answer: long-term symptomatic control

Q12. Which of the following is a nicotinic effect that may occur with excessive ambenonium dosing?

• Bronchodilation
• Muscle cramps and fasciculations
• Hyperglycemia
• Peripheral vasodilation

Correct Answer: Muscle cramps and fasciculations

Q13. Which of the following drugs might have enhanced cholinergic effects when co-administered with ambenonium?

• Beta-agonists
• Anticholinergics
• Pilocarpine
• Loop diuretics

Correct Answer: Pilocarpine

Q14. A distinguishing pharmacologic feature of ambenonium compared to physostigmine is:

• Ambenonium readily crosses the blood–brain barrier
• Ambenonium is a tertiary amine
• Ambenonium has minimal CNS effects
• Ambenonium is irreversible

Correct Answer: Ambenonium has minimal CNS effects

Q15. Which lab value or clinical sign helps monitor therapeutic response to ambenonium in myasthenia gravis?

• Serum cholesterol
• Daily grip strength and fatigability
• White blood cell count
• Serum creatinine only

Correct Answer: Daily grip strength and fatigability

Q16. Which of the following is a contraindication or precaution for ambenonium use?

• Mechanical intestinal obstruction
• Hyperthyroidism without symptoms
• Mild dermatologic rash
• History of migraine

Correct Answer: Mechanical intestinal obstruction

Q17. Which statement about the mechanism of reversible cholinesterase inhibitors like ambenonium is true?

• They covalently and permanently modify AChE
• They form a reversible complex with AChE, increasing synaptic ACh
• They block acetylcholine release presynaptically
• They block nicotinic receptors directly

Correct Answer: They form a reversible complex with AChE, increasing synaptic ACh

Q18. Overdose of ambenonium primarily produces which syndrome?

• Anticholinergic crisis
• Cholinergic crisis
• Serotonin syndrome
• Neuroleptic malignant syndrome

Correct Answer: Cholinergic crisis

Q19. Which of the following clinical tests historically used edrophonium but could be confused by longer-acting drugs like ambenonium?

• Tensilon test for myasthenia gravis
• Apgar score
• Glasgow coma scale
• Romberg test

Correct Answer: Tensilon test for myasthenia gravis

Q20. When managing cholinergic toxicity from ambenonium, which supportive measure is appropriate besides atropine?

• Naloxone administration
• Respiratory support and airway management
• Immediate dialysis in all cases
• Administration of beta blockers

Correct Answer: Respiratory support and airway management

Q21. Which route is commonly used for chronic administration of ambenonium in myasthenia gravis?

• Topical ocular
• Intramuscular every 2 hours
• Oral dosing
• Continuous intravenous infusion at home

Correct Answer: Oral dosing

Q22. A pharmacokinetic consequence of ambenonium being a quaternary compound is:

• Extensive hepatic first-pass metabolism leading to CNS levels
• Minimal renal excretion
• Limited distribution into the CNS
• High oral bioavailability in neonates

Correct Answer: Limited distribution into the CNS

Q23. Which clinical condition may worsen with cholinesterase inhibitors like ambenonium?

• Urinary retention
• Peptic ulcer disease due to increased gastric secretions
• Hyperthyroidism improves always
• Hypertension

Correct Answer: Peptic ulcer disease due to increased gastric secretions

Q24. How does ambenonium primarily affect acetylcholine metabolism?

• Enhances synthesis of ACh by choline acetyltransferase
• Prevents breakdown of ACh by inhibiting AChE
• Inhibits release of ACh from vesicles
• Converts ACh to inactive metabolites

Correct Answer: Prevents breakdown of ACh by inhibiting AChE

Q25. In elderly patients, dosing of ambenonium may require:

• Higher doses due to tolerance
• No monitoring as pharmacokinetics are unchanged
• Caution and possible dose reduction due to increased sensitivity
• Switch to intravenous route only

Correct Answer: Caution and possible dose reduction due to increased sensitivity

Q26. Which of the following agents is most useful to distinguish a cholinergic crisis from myasthenic crisis?

• Atropine challenge test
• Edrophonium (Tensilon) test
• Beta-blocker challenge
• Glucagon challenge

Correct Answer: Edrophonium (Tensilon) test

Q27. Which cardiovascular effect is most likely with therapeutic doses of ambenonium?

• Reflex tachycardia
• Bradycardia
• Severe hypertension
• Atrial fibrillation

Correct Answer: Bradycardia

Q28. Which patient condition requires caution when prescribing ambenonium due to risk of bronchospasm?

• Asthma or COPD
• Hypothyroidism
• Hyperlipidemia
• Osteoporosis

Correct Answer: Asthma or COPD

Q29. Which of the following best describes ambenonium’s effect duration relative to neostigmine?

• Ambenonium is shorter-acting than neostigmine
• Ambenonium and neostigmine have identical duration
• Ambenonium is longer-acting than neostigmine in many cases
• Neither drug has any clinical duration

Correct Answer: Ambenonium is longer-acting than neostigmine in many cases

Q30. Which monitoring parameter is important during chronic ambenonium therapy?

• Serum calcium
• Pulmonary function and signs of respiratory weakness
• Daily ECG only
• Serum potassium weekly

Correct Answer: Pulmonary function and signs of respiratory weakness

Q31. Which statement regarding drug interactions is correct?

• Concurrent use of anticholinesterases and succinylcholine has no interaction
• Anticholinesterase therapy may prolong the action of succinylcholine by inhibiting plasma cholinesterase
• Anticholinesterases decrease the effects of cholinergic agonists
• Ambenonium inactivates antibiotics

Correct Answer: Anticholinesterase therapy may prolong the action of succinylcholine by inhibiting plasma cholinesterase

Q32. Which adverse ocular effect might be expected with ambenonium use?

• Mydriasis
• Miosis and increased lacrimation
• Intraocular pressure elevation in all patients
• Permanent blindness

Correct Answer: Miosis and increased lacrimation

Q33. Which statement is true regarding the onset of action for orally administered ambenonium?

• Has an immediate onset within seconds
• Onset is slower than IV edrophonium and suited for chronic control
• Onset is identical to intramuscular epinephrine
• Never used orally due to toxicity

Correct Answer: Onset is slower than IV edrophonium and suited for chronic control

Q34. Ambenonium is least likely to cause which of the following effects?

• Increased gut motility
• Excessive sweating
• Central nervous system agitation
• Bradyarrhythmia

Correct Answer: Central nervous system agitation

Q35. Which pharmacologic group does ambenonium share most properties with?

• Benzodiazepines
• Acetylcholinesterase inhibitors like pyridostigmine
• Proton pump inhibitors
• ACE inhibitors

Correct Answer: Acetylcholinesterase inhibitors like pyridostigmine

Q36. Which sign differentiates organophosphate poisoning from reversible AChE inhibitor overdose?

• Organophosphates cause irreversible AChE phosphorylation
• Reversible inhibitors always cause permanent paralysis
• Organophosphates never affect muscarinic receptors
• Reversible inhibitors are treated with pralidoxime only

Correct Answer: Organophosphates cause irreversible AChE phosphorylation

Q37. In pregnancy, use of ambenonium should be:

• Automatically continued without consultation
• Avoided or used with caution weighing risks and benefits
• Used in very high doses only
• Replaced by aspirin therapy

Correct Answer: Avoided or used with caution weighing risks and benefits

Q38. Which symptom suggests underdosing rather than toxicity in a myasthenia gravis patient on ambenonium?

• Excessive salivation and sweating
• Worsening muscle weakness and fatigability
• Bradycardia and miosis
• Increased bowel movements

Correct Answer: Worsening muscle weakness and fatigability

Q39. Which is an appropriate counseling point for patients taking oral ambenonium?

• Take the drug only once monthly
• Expect possible increased salivation and carry anticholinergic if prescribed
• Stop immediately if muscle strength improves
• It will cause permanent cure of myasthenia gravis

Correct Answer: Expect possible increased salivation and carry anticholinergic if prescribed

Q40. Which monitoring is least relevant during ambenonium therapy?

• Respiratory function
• Heart rate and rhythm
• Liver enzyme levels routinely in all patients
• Gastrointestinal symptoms and weight

Correct Answer: Liver enzyme levels routinely in all patients

Q41. Which receptor type mediates the therapeutic action of increased acetylcholine at the neuromuscular junction?

• Muscarinic M2 receptors
• Nicotinic N1 (muscle-type) receptors
• Dopamine D2 receptors
• Histamine H1 receptors

Correct Answer: Nicotinic N1 (muscle-type) receptors

Q42. Which clinical scenario suggests cholinergic crisis requiring immediate intervention?

• Gradual improvement in muscle strength after dose
• Sudden respiratory distress with salivation and pinpoint pupils
• Isolated headache without weakness
• Improved swallowing function

Correct Answer: Sudden respiratory distress with salivation and pinpoint pupils

Q43. Which advantage does ambenonium have over long-term immunosuppressant therapy in MG?

• It reverses the autoimmune cause
• Provides symptomatic relief without immunosuppression
• Eliminates the need for any monitoring
• Completely prevents MG exacerbations

Correct Answer: Provides symptomatic relief without immunosuppression

Q44. For a patient taking ambenonium who develops severe bradycardia, the immediate pharmacologic treatment is:

• Intravenous epinephrine first-line
• IV atropine
• Oral beta blocker
• Neostigmine

Correct Answer: IV atropine

Q45. Which is true regarding discontinuation of ambenonium therapy?

• It requires gradual tapering based on clinical response
• Immediate cessation never produces symptoms
• There is permanent cholinesterase inhibition after stopping
• Stopping requires antidote administration

Correct Answer: It requires gradual tapering based on clinical response

Q46. Which pharmacologic class does ambenonium belong to?

• Beta-blocker
• Anticholinesterase (cholinesterase inhibitor)
• Corticosteroid
• Calcium channel blocker

Correct Answer: Anticholinesterase (cholinesterase inhibitor)

Q47. In pediatric use for myasthenia gravis, ambenonium dosing considerations include:

• Children require a single lifetime dose
• Dosing adjusted by weight and careful monitoring for cholinergic effects
• No monitoring required as children tolerate higher doses
• Use is contraindicated in all pediatric cases

Correct Answer: Dosing adjusted by weight and careful monitoring for cholinergic effects

Q48. Which exam-focused fact about ambenonium is important for B.Pharm students?

• It is an irreversible AChE inhibitor used for organophosphate poisoning
• It is a reversible, quaternary AChE inhibitor used in MG with limited CNS action
• It is primarily an antidepressant
• It enhances acetylcholine breakdown

Correct Answer: It is a reversible, quaternary AChE inhibitor used in MG with limited CNS action

Q49. Which symptom would most likely prompt dose reduction of ambenonium?

• Persistent mild fatigue only
• Marked diarrhea and bradycardia
• Improved muscle strength without side effects
• Asymptomatic slight lab value change unrelated to cholinergic activity

Correct Answer: Marked diarrhea and bradycardia

Q50. When comparing ambenonium with pyridostigmine for chronic MG control, a practical teaching point is:

• Both are anticholinesterases but may differ in duration and patient tolerance
• Only pyridostigmine crosses the BBB easily
• Ambenonium is an antipsychotic, not comparable
• Neither drug affects neuromuscular transmission

Correct Answer: Both are anticholinesterases but may differ in duration and patient tolerance

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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