Synthetic cholinergic blocking agents – Methantheline bromide MCQs With Answer

Synthetic cholinergic blocking agents – Methantheline bromide MCQs With Answer
Methantheline bromide is a synthetic cholinergic blocking agent used in pharmacology to reduce gastrointestinal motility and secretions. This antimuscarinic compound, often taught in B.Pharm courses, acts by competitively antagonizing muscarinic receptors, has a quaternary ammonium structure with limited CNS penetration, and produces classic anticholinergic effects such as dry mouth, blurred vision, constipation and urinary retention. Understanding its mechanism, pharmacokinetics, clinical uses, contraindications and toxicity is essential for pharmacy students preparing for exams. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary pharmacological classification of methantheline bromide?

• Synthetic cholinergic blocking (antimuscarinic) agent
• Cholinesterase inhibitor
• Nicotinic receptor agonist
• Benzodiazepine receptor antagonist

Correct Answer: Synthetic cholinergic blocking (antimuscarinic) agent

Q2. The main mechanism of action of methantheline bromide is:

• Irreversible inhibition of muscarinic receptors
• Competitive antagonism at muscarinic receptors
• Inhibition of acetylcholinesterase
• Activation of nicotinic receptors

Correct Answer: Competitive antagonism at muscarinic receptors

Q3. Methantheline bromide primarily blocks which type of receptor?

• Muscarinic acetylcholine receptors
• Nicotinic acetylcholine receptors
• Beta-adrenergic receptors
• Histamine H1 receptors

Correct Answer: Muscarinic acetylcholine receptors

Q4. Which structural feature of methantheline bromide limits its penetration into the central nervous system?

• Quaternary ammonium positive charge
• Lipophilic tertiary amine group
• Large steroid nucleus
• Peptide backbone

Correct Answer: Quaternary ammonium positive charge

Q5. A key therapeutic use historically associated with methantheline bromide is:

• Treatment of peptic ulcer disease and hypermotility disorders
• Management of bacterial infections
• Control of epilepsy
• Treatment of insulin-dependent diabetes

Correct Answer: Treatment of peptic ulcer disease and hypermotility disorders

Q6. Which common anticholinergic adverse effect is expected with methantheline bromide?

• Excessive salivation
• Dry mouth (xerostomia)
• Increased lacrimation
• Bradycardia

Correct Answer: Dry mouth (xerostomia)

Q7. Which clinical sign is most suggestive of antimuscarinic (anticholinergic) toxicity?

• Diaphoresis and miosis
• Bradykinesia and hypersalivation
• Dry skin, hyperthermia, delirium
• Hypothermia and excessive sweating

Correct Answer: Dry skin, hyperthermia, delirium

Q8. Which of the following is the appropriate pharmacological antidote for severe antimuscarinic poisoning?

• Physostigmine
• Propranolol
• Atropine
• Flumazenil

Correct Answer: Physostigmine

Q9. Methantheline bromide is most similar in action to which classical agent?

• Atropine
• Neostigmine
• Nicotine
• Ampicillin

Correct Answer: Atropine

Q10. Because methantheline bromide is a quaternary ammonium compound, which statement is true about its clinical profile?

• It readily crosses the blood–brain barrier causing marked central effects
• It has limited CNS penetration and predominantly peripheral effects
• It is highly lipophilic and accumulates in brain tissue
• It is primarily used for central nervous system depression

Correct Answer: It has limited CNS penetration and predominantly peripheral effects

Q11. Blockade of which muscarinic receptor subtype by antimuscarinic drugs contributes most to increased heart rate?

• M2 receptor blockade
• M1 receptor blockade
• M4 receptor stimulation
• M5 receptor agonism

Correct Answer: M2 receptor blockade

Q12. Which gastrointestinal effect is expected after administration of methantheline bromide?

• Increased gastric motility and diarrhea
• Reduced gastrointestinal motility and constipation
• Enhanced salivary secretion
• Increased pancreatic enzyme secretion

Correct Answer: Reduced gastrointestinal motility and constipation

Q13. Methantheline bromide would be contraindicated or used cautiously in patients with:

• Angle-closure glaucoma
• Hypothyroidism
• Iron deficiency anemia
• Viral hepatitis

Correct Answer: Angle-closure glaucoma

Q14. One expected ocular effect of methantheline bromide is:

• Miosis (pupil constriction)
• Mydriasis and blurred vision due to cycloplegia
• Improved accommodation for near vision
• Decreased intraocular pressure in angle-closure glaucoma

Correct Answer: Mydriasis and blurred vision due to cycloplegia

Q15. A key pharmacokinetic consequence of methantheline being a quaternary ammonium salt is:

• High oral bioavailability and CNS penetration
• Poor lipid solubility and reduced CNS entry
• Rapid passive diffusion across blood–brain barrier
• Extensive enterohepatic circulation in the CNS

Correct Answer: Poor lipid solubility and reduced CNS entry

Q16. Combining methantheline bromide with antihistamines that have anticholinergic activity may result in:

• Antagonism of antimuscarinic effects
• Additive anticholinergic side effects
• Complete neutralization of both drugs
• Reduced risk of urinary retention

Correct Answer: Additive anticholinergic side effects

Q17. Which clinical use is least appropriate for methantheline bromide?

• Reducing gastric secretions in peptic ulcer disease
• Treating urinary retention caused by prostate enlargement
• Managing intestinal hypermotility and spasms
• As a primary therapy for bacterial infection

Correct Answer: As a primary therapy for bacterial infection

Q18. The presence of a bromide ion in methantheline bromide indicates:

• It is a free base with no salt form
• It exists as a bromide salt of a positively charged amine
• It is an organic peroxide compound
• It must be administered only by inhalation

Correct Answer: It exists as a bromide salt of a positively charged amine

Q19. Which symptom is NOT typically caused by antimuscarinic therapy like methantheline?

• Constipation
• Bradycardia
• Dry mouth
• Urinary retention

Correct Answer: Bradycardia

Q20. Which of the following best explains reduced sweating with methantheline use?

• Stimulation of sympathetic cholinergic receptors on sweat glands
• Blockade of muscarinic receptors on eccrine sweat glands
• Direct antagonism at alpha-adrenergic receptors controlling sweat
• Inhibition of thyroid hormone that controls thermoregulation

Correct Answer: Blockade of muscarinic receptors on eccrine sweat glands

Q21. Which drug property most contributes to renal excretion of methantheline bromide?

• High lipophilicity and protein binding
• Quaternary charge leading to water solubility
• Covalent binding to tissue proteins
• Extensive hepatic metabolism to nonpolar metabolites only

Correct Answer: Quaternary charge leading to water solubility

Q22. During an exam question about drug interactions, which agent would most likely reverse peripheral antimuscarinic effects of methantheline?

• Physostigmine (centrally active cholinesterase inhibitor)
• Propranolol (beta-blocker)
• Neostigmine (peripherally active cholinesterase inhibitor)
• Diazepam (benzodiazepine)

Correct Answer: Neostigmine (peripherally active cholinesterase inhibitor)

Q23. Methantheline’s competitive blockade of muscarinic receptors means that:

• Its effects cannot be overcome by increasing acetylcholine
• Increasing acetylcholine (or agonist) can surmount the blockade
• It covalently modifies the receptor protein
• It permanently inactivates the receptor until new receptors are synthesized

Correct Answer: Increasing acetylcholine (or agonist) can surmount the blockade

Q24. Which patient population should be given methantheline with caution due to increased risk of urinary retention?

• Young healthy adults with no comorbidities
• Patients with benign prostatic hyperplasia (BPH)
• Patients with iron deficiency anemia
• Individuals receiving topical ocular antihistamines

Correct Answer: Patients with benign prostatic hyperplasia (BPH)

Q25. Which of the following respiratory effects is associated with antimuscarinic agents like methantheline?

• Increased bronchial secretions and bronchoconstriction
• Bronchodilation and reduced bronchial secretions
• Direct stimulation of beta-2 receptors causing bronchoconstriction
• Excessive surfactant production in alveoli

Correct Answer: Bronchodilation and reduced bronchial secretions

Q26. An elderly patient given methantheline bromide is at particular risk of which central adverse effect despite limited CNS penetration?

• Severe hypoglycemia
• Cognitive impairment and confusion
• Marked weight gain
• Osteoporosis

Correct Answer: Cognitive impairment and confusion

Q27. Which clinical sign would indicate ocular toxicity from an antimuscarinic like methantheline?

• Improved near vision
• Photophobia and blurred near vision due to mydriasis and cycloplegia
• Pinpoint pupils and excessive tearing
• Decreased intraocular pressure in closed-angle glaucoma

Correct Answer: Photophobia and blurred near vision due to mydriasis and cycloplegia

Q28. Which of the following best describes methantheline bromide’s effect on gastric acid secretion?

• It increases acid secretion by stimulating parietal cells
• It reduces acid secretion by blocking vagal cholinergic stimulation
• It neutralizes acid by acting as an antacid
• It acts as a proton pump inhibitor at H+/K+ ATPase

Correct Answer: It reduces acid secretion by blocking vagal cholinergic stimulation

Q29. When counselling patients about side effects, which symptom should be warned as a potentially serious antimuscarinic adverse effect?

• Excessive salivation
• Severe urinary retention with abdominal pain
• Improved sweating in hot weather
• Sudden weight loss

Correct Answer: Severe urinary retention with abdominal pain

Q30. Which drug property differentiates methantheline from tertiary amine antimuscarinics like atropine?

• Methantheline is a tertiary amine and easily crosses BBB
• Methantheline is a quaternary ammonium salt and crosses BBB poorly
• Methantheline exclusively stimulates muscarinic receptors
• Methantheline irreversibly binds acetylcholinesterase

Correct Answer: Methantheline is a quaternary ammonium salt and crosses BBB poorly

Q31. The most likely route of elimination for unchanged methantheline due to its water solubility is:

• Renal excretion
• Excretion in exhaled air
• Secretion in bile only
• Metabolism to volatile gases

Correct Answer: Renal excretion

Q32. Which of the following drug combinations with methantheline would most likely increase anticholinergic adverse effects?

• Concomitant use of cholinesterase inhibitors
• Concomitant use of tricyclic antidepressants or antihistamines
• Concurrent therapy with pilocarpine eye drops (muscarinic agonist)
• Administration with physostigmine

Correct Answer: Concomitant use of tricyclic antidepressants or antihistamines

Q33. In toxicology questions, which feature distinguishes anticholinergic from sympathomimetic toxidromes?

• Presence of dry skin and dry mucous membranes in anticholinergic toxicity
• Excessive sweating in anticholinergic toxicity
• Bradycardia in anticholinergic toxicity
• Miosis in anticholinergic toxicity

Correct Answer: Presence of dry skin and dry mucous membranes in anticholinergic toxicity

Q34. Which pharmacological action of methantheline explains its use in reducing abdominal cramps?

• Stimulation of enteric cholinergic neurons
• Inhibition of muscarinic-mediated smooth muscle contraction
• Activation of nicotinic receptors in gut smooth muscle
• Enhancement of prostaglandin release

Correct Answer: Inhibition of muscarinic-mediated smooth muscle contraction

Q35. For an MCQ about drug design, which rationale explains synthesizing quaternary antimuscarinics like methantheline?

• To enhance central sedative effects
• To limit central side effects by reducing BBB penetration and to target peripheral sites
• To increase oral bioavailability and CNS accumulation
• To create irreversible enzyme inhibitors

Correct Answer: To limit central side effects by reducing BBB penetration and to target peripheral sites

Q36. Which sign would most likely improve after administration of physostigmine in antimuscarinic overdose?

• Persistent mydriasis and central agitation
• Improved central agitation and delirium
• Worsened urinary retention
• Increased dry mouth symptoms

Correct Answer: Improved central agitation and delirium

Q37. When comparing methantheline to atropine, which statement is correct regarding central adverse effects?

• Methantheline causes more central delirium than atropine
• Methantheline causes fewer central adverse effects than atropine
• Both have identical central penetration and effects
• Atropine is a quaternary ammonium like methantheline

Correct Answer: Methantheline causes fewer central adverse effects than atropine

Q38. Which muscarinic effect is responsible for the antispasmodic benefit of methantheline in the gut?

• Increased acetylcholine release in enteric neurons
• Blockade of M3-mediated contraction of intestinal smooth muscle
• Stimulation of enteric nicotinic receptors causing relaxation
• Activation of serotonin receptors to decrease motility

Correct Answer: Blockade of M3-mediated contraction of intestinal smooth muscle

Q39. Which laboratory or clinical monitoring is most relevant when a patient is started on methantheline?

• Serum electrolyte panel for immediate changes
• Monitoring for anticholinergic side effects such as urinary retention and tachycardia
• Frequent liver biopsy
• Serum methantheline concentration for routine dosing

Correct Answer: Monitoring for anticholinergic side effects such as urinary retention and tachycardia

Q40. A multiple-choice question on contraindications: which condition is a relative contraindication for methantheline?

• Open-angle glaucoma without symptoms
• Myasthenia gravis
• Hyperthyroidism without cardiovascular symptoms
• Controlled hypertension

Correct Answer: Myasthenia gravis

Q41. Which of the following describes the expected effect of methantheline on salivary glands?

• Increased salivation leading to drooling
• Marked decrease in salivary secretion causing dry mouth
• No effect on salivation
• Transient hyperstimulation of saliva followed by rebound hypersalivation

Correct Answer: Marked decrease in salivary secretion causing dry mouth

Q42. In pharmacology MCQs, which feature distinguishes quaternary antimuscarinics like methantheline from tertiary ones regarding absorption?

• Quaternary agents are more lipophilic and better absorbed orally
• Quaternary agents have poorer oral absorption and less CNS penetration
• Tertiary agents are water soluble and poorly absorbed from gut
• Quaternary agents readily cross the placenta and BBB

Correct Answer: Quaternary agents have poorer oral absorption and less CNS penetration

Q43. Which adverse cardiac effect is most commonly associated with antimuscarinic agents like methantheline?

• Marked bradycardia leading to syncope
• Tachycardia due to vagal blockade
• Complete atrioventricular block at therapeutic doses
• Direct myocardial necrosis

Correct Answer: Tachycardia due to vagal blockade

Q44. In exams about drug interactions, which class of drugs might have reduced efficacy when combined with methantheline?

• Beta-agonists for asthma
• Cholinesterase inhibitors used for Alzheimer’s disease
• Proton pump inhibitors for acid suppression
• Diuretics for hypertension

Correct Answer: Cholinesterase inhibitors used for Alzheimer’s disease

Q45. Which of the following best summarizes why methantheline can be useful in irritable bowel syndrome with diarrhea?

• It stimulates intestinal secretion and motility
• It reduces intestinal spasms and slows transit via muscarinic blockade
• It acts as an antibiotic to alter gut flora
• It increases vagal tone to enhance digestion

Correct Answer: It reduces intestinal spasms and slows transit via muscarinic blockade

Q46. What is a classic central sign that helps differentiate anticholinergic toxicity from opioid toxicity?

• Pinpoint pupils and respiratory depression seen in anticholinergic toxicity
• Delirium, hallucinations and agitation seen in anticholinergic toxicity
• Bradycardia and hypothermia seen in anticholinergic toxicity
• Improved consciousness and miosis seen in anticholinergic toxicity

Correct Answer: Delirium, hallucinations and agitation seen in anticholinergic toxicity

Q47. Which sign would be least expected in a patient taking therapeutic doses of methantheline?

• Dry mouth
• Excessive sweating
• Constipation
• Blurred near vision

Correct Answer: Excessive sweating

Q48. When teaching B.Pharm students about receptor pharmacology, which statement about methantheline is correct?

• It is a muscarinic receptor agonist that mimics acetylcholine
• It is a competitive muscarinic receptor antagonist that blocks acetylcholine actions
• It irreversibly activates cholinesterase enzymes
• It selectively activates M5 receptors to produce GI effects

Correct Answer: It is a competitive muscarinic receptor antagonist that blocks acetylcholine actions

Q49. Which clinical scenario would prompt avoidance of methantheline due to risk of exacerbation?

• Patient with acute urinary retention due to prostatic hypertrophy
• Patient with seasonal allergic rhinitis only
• Patient with well-controlled type 2 diabetes on metformin
• Patient with mild eczema using topical emollients

Correct Answer: Patient with acute urinary retention due to prostatic hypertrophy

Q50. Which early symptom might indicate too high a dose of an antimuscarinic agent like methantheline during therapy?

• Excessive salivation and tearing
• Dry mouth and difficulty speaking or swallowing
• Sudden improvement in vision
• Increased sweating and hypothermia

Correct Answer: Dry mouth and difficulty speaking or swallowing

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