Parasympathomimetics MCQs With Answer

Introduction:

Parasympathomimetics MCQs With Answer provide B. Pharm students a focused review of cholinergic agonists, including direct (acetylcholine, bethanechol, pilocarpine) and indirect agents (neostigmine, physostigmine). This concise, keyword-rich guide highlights mechanism of action at muscarinic and nicotinic receptors, pharmacokinetics, clinical uses (glaucoma, urinary retention, myasthenia gravis), adverse effects, contraindications, and antidotes. Emphasis on receptor selectivity, dose-response, and drug interactions prepares students for exams and clinical application. Each question reinforces core pharmacology concepts, therapeutic rationale, and safety considerations relevant for pharmacy practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which receptor subtype primarily mediates miosis produced by topical pilocarpine in glaucoma?

• Alpha-1 adrenergic receptor
• Muscarinic M3 receptor on sphincter pupillae
• Nicotinic receptor at the neuromuscular junction
• Dopamine D2 receptor

Correct Answer: Muscarinic M3 receptor on sphincter pupillae

Q2. Which drug is a direct-acting muscarinic agonist used to treat urinary retention by increasing detrusor tone?

• Bethanechol
• Pilocarpine
• Neostigmine
• Atropine

Correct Answer: Bethanechol

Q3. Which statement best describes neostigmine?

• Direct muscarinic agonist with high CNS penetration
• Reversible acetylcholinesterase inhibitor that does not cross the blood–brain barrier
• Irreversible organophosphate inhibitor of cholinesterase
• Nicotinic receptor antagonist used for myasthenia gravis

Correct Answer: Reversible acetylcholinesterase inhibitor that does not cross the blood–brain barrier

Q4. Which adverse effect is most characteristic of parasympathomimetic overdose?

• Tachycardia and dry mouth
• Bradycardia, sweating, salivation, and bronchospasm
• Hyperthermia and mydriasis
• Urinary retention and constipation

Correct Answer: Bradycardia, sweating, salivation, and bronchospasm

Q5. Which agent is used topically to lower intraocular pressure by contracting ciliary muscle and opening trabecular meshwork?

• Timolol
• Pilocarpine
• Atropine
• Latanoprost

Correct Answer: Pilocarpine

Q6. Which drug would be the best choice to reverse neuromuscular blockade from non-depolarizing agents after surgery?

• Pralidoxime
• Neostigmine
• Suxamethonium
• Bethanechol

Correct Answer: Neostigmine

Q7. Physostigmine differs from neostigmine because it:

• Is an irreversible cholinesterase inhibitor
• Has no muscarinic effects
• Crosses the blood–brain barrier and treats anticholinergic toxicity
• Is a selective nicotinic agonist

Correct Answer: Crosses the blood–brain barrier and treats anticholinergic toxicity

Q8. Which parasympathomimetic is most appropriate for treating open-angle glaucoma by increasing outflow through trabecular meshwork?

• Bethanechol orally
• Pilocarpine ophthalmic
• Neostigmine systemic
• Physostigmine oral

Correct Answer: Pilocarpine ophthalmic

Q9. The primary mechanism of action of organophosphate poisoning involves:

• Competitive blockade of muscarinic receptors
• Irreversible inhibition of acetylcholinesterase
• Direct nicotinic receptor activation
• Inhibition of catecholamine reuptake

Correct Answer: Irreversible inhibition of acetylcholinesterase

Q10. Which is the recommended antidote to treat acute muscarinic effects of organophosphate poisoning?

• Propranolol
• Atropine
• Pilocarpine
• Neostigmine

Correct Answer: Atropine

Q11. Which parasympathomimetic is useful in the diagnosis of asthma due to bronchoconstriction when assessing bronchial hyperreactivity?

• Methacholine
• Pilocarpine
• Bethanechol
• Physostigmine

Correct Answer: Methacholine

Q12. Which property distinguishes bethanechol from acetylcholine for clinical use?

• Bethanechol is rapidly hydrolyzed by cholinesterase
• Bethanechol is selective for muscarinic receptors and resistant to acetylcholinesterase
• Bethanechol primarily activates nicotinic receptors
• Bethanechol has strong central nervous system effects

Correct Answer: Bethanechol is selective for muscarinic receptors and resistant to acetylcholinesterase

Q13. Which adverse effect limits the systemic use of pilocarpine?

• Dryness of mouth
• Excessive sweating and salivation
• Severe hypertension
• Urinary retention

Correct Answer: Excessive sweating and salivation

Q14. Which nicotinic receptor location is primarily involved in autonomic ganglionic transmission?

• Nicotinic N1 (muscle) at neuromuscular junction
• Nicotinic Nn (neuronal) at autonomic ganglia
• Muscarinic M2 in the heart
• Alpha-2 adrenergic receptors

Correct Answer: Nicotinic Nn (neuronal) at autonomic ganglia

Q15. Which drug is contraindicated in asthma due to risk of bronchospasm with parasympathomimetics?

• Bethanechol for urinary retention
• Pilocarpine eye drops for glaucoma
• Neostigmine for myasthenia gravis
• Atropine administration

Correct Answer: Bethanechol for urinary retention

Q16. Which statement about cholinesterase inhibitors and Alzheimer’s disease is correct?

• Neostigmine is the first-line oral therapy for Alzheimer’s
• Physostigmine is preferred due to peripheral action
• Donepezil and rivastigmine are cholinesterase inhibitors used in Alzheimer’s
• Cholinesterase inhibitors irreversibly destroy cholinergic neurons

Correct Answer: Donepezil and rivastigmine are cholinesterase inhibitors used in Alzheimer’s

Q17. Which drug interaction increases the effect of parasympathomimetics?

• Anticholinergic antihistamines
• Beta-adrenergic blockers
• Cholinesterase inhibitors with succinylcholine
• Muscarinic antagonists like atropine

Correct Answer: Beta-adrenergic blockers

Q18. Which is a common muscarinic effect on the gastrointestinal tract?

• Decreased motility and constipation
• Increased motility and secretion
• Inhibition of gastric acid secretion
• Relaxation of intestinal smooth muscle

Correct Answer: Increased motility and secretion

Q19. Which clinical sign helps differentiate muscarinic from nicotinic toxicity in organophosphate poisoning?

• Muscle fasciculations suggest muscarinic toxicity
• Miosis and bronchorrhea indicate muscarinic overactivation
• Tachycardia only occurs with muscarinic toxicity
• Hyperthermia is specific for nicotinic toxicity

Correct Answer: Miosis and bronchorrhea indicate muscarinic overactivation

Q20. Pralidoxime (2-PAM) is most effective when administered in organophosphate poisoning because it:

• Reverses muscarinic effects immediately
• Reactivates phosphorylated acetylcholinesterase if given early
• Blocks muscarinic receptors permanently
• Acts as a central muscarinic agonist

Correct Answer: Reactivates phosphorylated acetylcholinesterase if given early

Q21. A patient with myasthenia gravis is treated with pyridostigmine. Its primary therapeutic action is:

• Direct stimulation of nicotinic receptors
• Irreversible inhibition of acetylcholinesterase
• Reversible inhibition of acetylcholinesterase increasing ACh at NMJ
• Blocking acetylcholine release

Correct Answer: Reversible inhibition of acetylcholinesterase increasing ACh at NMJ

Q22. Which of the following is a quaternary amine and therefore has limited CNS penetration?

• Physostigmine
• Neostigmine
• Donepezil
• Pilocarpine

Correct Answer: Neostigmine

Q23. Which parasympathomimetic effect would be useful in treating Sjögren’s syndrome?

• Inhibition of salivary secretion
• Stimulation of salivation with pilocarpine or cevimeline
• Blocking muscarinic receptors to reduce saliva
• Using beta-agonists to increase saliva

Correct Answer: Stimulation of salivation with pilocarpine or cevimeline

Q24. Which describes the pharmacokinetic advantage of using topical ophthalmic pilocarpine?

• Enhanced systemic absorption and effects
• Localized action with reduced systemic adverse effects
• Long half-life leading to daily dosing only
• Complete resistance to hydrolysis by cholinesterase

Correct Answer: Localized action with reduced systemic adverse effects

Q25. Which receptor primarily mediates the negative chronotropic effect of acetylcholine on the heart?

• Muscarinic M1 on sinoatrial node
• Muscarinic M2 on SA and AV node
• Nicotinic receptors in ventricular muscle
• Beta-1 adrenergic receptors

Correct Answer: Muscarinic M2 on SA and AV node

Q26. Which clinical condition is a contraindication for parasympathomimetics due to risk of worsening symptoms?

• Urinary retention
• Glaucoma (narrow-angle)
• Asthma or chronic obstructive pulmonary disease
• Myasthenia gravis

Correct Answer: Asthma or chronic obstructive pulmonary disease

Q27. Carbachol is used in ophthalmology because it:

• Is selective for muscarinic M2 receptors only
• Is resistant to acetylcholinesterase and activates both muscarinic and nicotinic receptors
• Crosses BBB to treat central disorders
• Has long systemic half-life when given orally

Correct Answer: Is resistant to acetylcholinesterase and activates both muscarinic and nicotinic receptors

Q28. Which lab finding is consistent with severe organophosphate poisoning?

• Increased plasma cholinesterase (pseudocholinesterase) activity
• Reduced erythrocyte cholinesterase activity
• Elevated serum potassium due to nicotinic blockade
• Marked hyperglycemia from muscarinic overactivity

Correct Answer: Reduced erythrocyte cholinesterase activity

Q29. Which therapeutic strategy reduces muscarinic side effects when giving systemic cholinesterase inhibitors?

• Administering atropine to block muscarinic receptors while preserving nicotinic benefit
• Adding pilocarpine to counteract muscarinic effects
• Increasing dose of cholinesterase inhibitor
• Co-administering beta-agonists to enhance muscarinic activity

Correct Answer: Administering atropine to block muscarinic receptors while preserving nicotinic benefit

Q30. Which feature best explains why some cholinomimetic drugs cause more GI effects than others?

• Degree of nicotinic vs muscarinic selectivity and susceptibility to cholinesterase hydrolysis
• Ability to block adrenergic receptors
• Presence of alpha-adrenergic agonist activity
• Their capacity to irreversibly bind to muscarinic receptors

Correct Answer: Degree of nicotinic vs muscarinic selectivity and susceptibility to cholinesterase hydrolysis

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