Synthetic cholinergic blocking agents – Orphenadrine citrate MCQs With Answer

Synthetic cholinergic blocking agents like Orphenadrine citrate are important anticholinergic (antimuscarinic) drugs taught in B. Pharm pharmacology. This introduction covers mechanism of action, therapeutic uses as a centrally acting muscle relaxant and analgesic, pharmacodynamic effects, adverse reactions, contraindications, drug interactions, and pharmaceutical forms. Emphasis is on clinical relevance, safe use, monitoring and counselling — key for exam readiness. Keywords: Synthetic cholinergic blocking agents, Orphenadrine citrate, anticholinergic, antimuscarinic, muscle relaxant, pharmacology, adverse effects, B. Pharm MCQs. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which pharmacological class does orphenadrine citrate belong to?

• Beta-blocker
• Anticoagulant
• Antimuscarinic (anticholinergic)
• ACE inhibitor

Correct Answer: Antimuscarinic (anticholinergic)

Q2. The primary mechanism of action of orphenadrine is:

• Inhibition of cyclooxygenase enzymes
• Competitive antagonism at muscarinic acetylcholine receptors
• Activation of GABA receptors
• Blockade of voltage-gated sodium channels

Correct Answer: Competitive antagonism at muscarinic acetylcholine receptors

Q3. Orphenadrine is chemically classified as a:

• Quaternary ammonium compound
• Tertiary amine
• Sulfonamide
• Peptide

Correct Answer: Tertiary amine

Q4. Because orphenadrine is a tertiary amine, it is able to:

• Be excreted unchanged in bile only
• Cross the blood–brain barrier
• Be active only in the gut lumen
• Bind exclusively to nicotinic receptors

Correct Answer: Cross the blood–brain barrier

Q5. Orphenadrine’s principal therapeutic use is as a:

• Antihypertensive
• Muscle relaxant for acute musculoskeletal pain
• Antiplatelet agent
• Antiviral therapy

Correct Answer: Muscle relaxant for acute musculoskeletal pain

Q6. A common central adverse effect of orphenadrine is:

• Hypoactivity and bradycardia
• Seizures in all patients
• Drowsiness and confusion
• Profound hypoglycemia

Correct Answer: Drowsiness and confusion

Q7. Which of the following is a typical peripheral anticholinergic side effect of orphenadrine?

• Excessive salivation
• Diarrhea
• Urinary retention
• Hypothermia

Correct Answer: Urinary retention

Q8. Which ocular effect is expected with antimuscarinic drugs like orphenadrine?

• Miosis and increased lacrimation
• Mydriasis and blurred vision
• Decreased intraocular pressure
• Improved night vision

Correct Answer: Mydriasis and blurred vision

Q9. Orphenadrine may worsen which existing condition due to its anticholinergic actions?

• Closed-angle glaucoma
• Hypothyroidism
• Type 1 diabetes mellitus
• Iron-deficiency anemia

Correct Answer: Closed-angle glaucoma

Q10. The citrate salt form of orphenadrine is used primarily to:

• Reduce central nervous system penetration
• Increase aqueous solubility for formulation
• Provide antimicrobial properties
• Convert it into a prodrug

Correct Answer: Increase aqueous solubility for formulation

Q11. Orphenadrine’s analgesic effect is thought to be due to:

• Peripheral COX-2 inhibition only
• Central anticholinergic and sedative actions
• Direct opioid receptor agonism
• Calcium channel blockade in muscle

Correct Answer: Central anticholinergic and sedative actions

Q12. Which route of administration provides more rapid onset for orphenadrine in acute settings?

• Oral tablet only
• Intramuscular or intravenous injection
• Topical cream
• Transdermal patch

Correct Answer: Intramuscular or intravenous injection

Q13. In anticholinergic overdose with orphenadrine, the specific antidote that may be used is:

• Naloxone
• Flumazenil
• Physostigmine
• Atropine

Correct Answer: Physostigmine

Q14. Which monitoring parameter is especially important in patients taking orphenadrine?

• Serum potassium daily
• Heart rate and urinary output
• Prothrombin time
• Fasting blood glucose hourly

Correct Answer: Heart rate and urinary output

Q15. Compared with quaternary antimuscarinics like glycopyrrolate, orphenadrine:

• Does not cross the blood–brain barrier
• Is more likely to produce central nervous system effects
• Has exclusively peripheral effects
• Is less lipid soluble

Correct Answer: Is more likely to produce central nervous system effects

Q16. Combining orphenadrine with other central depressants (e.g., alcohol, benzodiazepines) may cause:

• Reduced sedation
• Additive sedation and respiratory depression risk
• Immediate hypertension
• Enhanced cholinergic activity

Correct Answer: Additive sedation and respiratory depression risk

Q17. A patient with benign prostatic hyperplasia (BPH) should use orphenadrine with caution because it may:

• Improve urinary flow
• Cause urinary retention and worsen symptoms
• Reduce prostate size
• Increase ejaculatory volume

Correct Answer: Cause urinary retention and worsen symptoms

Q18. Which of the following is NOT an adverse effect commonly associated with orphenadrine?

• Dry mouth
• Constipation
• Excessive sweating
• Tachycardia

Correct Answer: Excessive sweating

Q19. Orphenadrine is structurally related to which common antihistamine?

• Loratadine
• Diphenhydramine
• Fexofenadine
• Cetirizine

Correct Answer: Diphenhydramine

Q20. Which patient advice is appropriate when starting orphenadrine therapy?

• Expect immediate improvement in vision
• Avoid driving or operating heavy machinery until you know how it affects you
• Increase alcohol intake to reduce side effects
• Take with a high-dose stimulant

Correct Answer: Avoid driving or operating heavy machinery until you know how it affects you

Q21. In the elderly, the use of orphenadrine should be cautious because it may:

• Prevent falls by improving balance
• Increase risk of confusion, delirium and falls
• Enhance cognition
• Completely eliminate pain without sedation

Correct Answer: Increase risk of confusion, delirium and falls

Q22. Which of the following drug interactions is most likely with orphenadrine?

• Antagonism of warfarin’s anticoagulant effect
• Additive anticholinergic effects with tricyclic antidepressants
• Direct enhancement of insulin secretion
• Chelation with tetracyclines

Correct Answer: Additive anticholinergic effects with tricyclic antidepressants

Q23. Anticholinergic toxidrome from orphenadrine typically includes all EXCEPT:

• Flushed, dry skin
• Hyperthermia
• Small, pinpoint pupils
• Agitation and hallucinations

Correct Answer: Small, pinpoint pupils

Q24. Which organ mainly metabolizes orphenadrine?

• Liver
• Kidney exclusively
• Pancreas
• Thyroid gland

Correct Answer: Liver

Q25. The excretion of orphenadrine and its metabolites is primarily via:

• Renal route
• Expired air as unchanged drug
• Saliva only
• Feces exclusively

Correct Answer: Renal route

Q26. Which of the following is a clinical contraindication to orphenadrine therapy?

• Open-angle glaucoma
• Acute angle-closure glaucoma
• Mild seasonal allergic rhinitis
• Controlled asthma with inhaler

Correct Answer: Acute angle-closure glaucoma

Q27. Which of the following statements about orphenadrine’s receptor selectivity is true?

• It selectively blocks only M2 receptors
• It is a nonselective muscarinic receptor antagonist
• It is a nicotinic receptor agonist
• It specifically activates M3 receptors

Correct Answer: It is a nonselective muscarinic receptor antagonist

Q28. For enhanced analgesia in muscle spasm, orphenadrine is often combined with:

• Paracetamol (acetaminophen)
• Oral insulin
• Warfarin
• Levothyroxine

Correct Answer: Paracetamol (acetaminophen)

Q29. Which patient would be at higher risk of adverse effects from orphenadrine?

• A young, healthy adult with no comorbidities
• An elderly patient with cognitive impairment and BPH
• A patient using short-acting bronchodilators only
• A patient with controlled seasonal allergies

Correct Answer: An elderly patient with cognitive impairment and BPH

Q30. Which sign would suggest orphenadrine-induced anticholinergic toxicity in an emergency?

• Excessive salivation, pinpoint pupils
• Dry mucous membranes, dilated pupils, high temperature
• Bradycardia and slow bowel sounds
• Profuse sweating and hypothermia

Correct Answer: Dry mucous membranes, dilated pupils, high temperature

Q31. Which clinical use is NOT typical for orphenadrine?

• Treatment of acute musculoskeletal pain
• Adjunct in chronic muscle spasm management
• First-line bronchodilator in COPD
• Symptomatic relief of muscle stiffness

Correct Answer: First-line bronchodilator in COPD

Q32. Patient counselling point for orphenadrine regarding mouth care should include:

• No need for fluids as dry mouth is beneficial
• Maintain good oral hygiene and use sugar-free lozenges for dry mouth
• Immediately stop all oral hygiene
• Increase intake of caffeinated beverages

Correct Answer: Maintain good oral hygiene and use sugar-free lozenges for dry mouth

Q33. Which of the following is an important nursing assessment before administering orphenadrine?

• Check for history of prostatic hypertrophy and angle-closure glaucoma
• Ensure patient has eaten within 5 minutes
• Measure blood lactate concentration
• Confirm patient has received influenza vaccine

Correct Answer: Check for history of prostatic hypertrophy and angle-closure glaucoma

Q34. In pharmacology exams, orphenadrine is used as an example of an agent that:

• Is an antimuscarinic with both central and peripheral effects
• Acts exclusively at nicotinic receptors at the neuromuscular junction
• Is a pure peripheral ganglionic blocker
• Has no central nervous system penetration

Correct Answer: Is an antimuscarinic with both central and peripheral effects

Q35. If a patient on orphenadrine develops severe agitation and hallucinations, the pharmacist should consider:

• Increasing the dose
• Discontinuing the drug and evaluating for anticholinergic toxicity
• Adding another anticholinergic agent
• Ignoring symptoms as they are unrelated

Correct Answer: Discontinuing the drug and evaluating for anticholinergic toxicity

Q36. Which laboratory investigation is most relevant when hepatotoxicity is suspected with orphenadrine?

• Serum creatinine kinase only
• Liver function tests (ALT, AST)
• Complete lipid profile
• Urinary ketones

Correct Answer: Liver function tests (ALT, AST)

Q37. Orphenadrine should be used with caution in patients taking which class of psychiatric medication due to additive anticholinergic effects?

• Selective serotonin reuptake inhibitors (SSRIs)
• Tricyclic antidepressants (TCAs)
• Monoamine oxidase inhibitors (MAOIs) only
• Typical antipsychotics with no anticholinergic activity

Correct Answer: Tricyclic antidepressants (TCAs)

Q38. Which statement about orphenadrine’s effect on the gastrointestinal tract is correct?

• It increases GI motility and causes diarrhea
• It reduces GI motility and may cause constipation
• It selectively increases gastric acid secretion
• It has no effect on GI function

Correct Answer: It reduces GI motility and may cause constipation

Q39. Which of the following is an example of a quaternary antimuscarinic that contrasts with orphenadrine in CNS penetration?

• Atropine
• Scopolamine
• Glycopyrrolate
• Orphenadrine itself

Correct Answer: Glycopyrrolate

Q40. Best practice for a pharmacist dispensing orphenadrine includes advising patients to avoid:

• Concomitant use of other anticholinergic medications unless directed
• Sunlight exposure only
• Consuming leafy green vegetables
• Regular exercise while on therapy

Correct Answer: Concomitant use of other anticholinergic medications unless directed

Q41. Which effect on the cardiovascular system can be caused by orphenadrine?

• Marked bradycardia in all patients
• Tachycardia due to vagal blockade
• Immediate heart block in healthy subjects
• Profound hypotension via alpha blockade

Correct Answer: Tachycardia due to vagal blockade

Q42. In a patient with a history of seizure disorder, orphenadrine should be:

• Used with caution because it may lower seizure threshold
• Used in high doses to prevent seizures
• Combined with stimulants to prevent drowsiness
• Considered completely safe with no precautions

Correct Answer: Used with caution because it may lower seizure threshold

Q43. Which counselling point addresses anticholinergic effect on vision for patients taking orphenadrine?

• Expect improved night vision
• Use caution when reading or driving if you experience blurred vision
• Immediate contact lenses usage is recommended
• No visual effects are expected

Correct Answer: Use caution when reading or driving if you experience blurred vision

Q44. In an acute overdose of orphenadrine presenting with severe agitation, hyperthermia and tachycardia, an appropriate immediate measure is:

• Administer physostigmine if no contraindications and manage supportively
• Give high-dose oral insulin
• Perform immediate hemodialysis as first-line
• Administer naloxone

Correct Answer: Administer physostigmine if no contraindications and manage supportively

Q45. Which patient population requires dose adjustment or special caution when prescribing orphenadrine?

• Young athletes with no comorbidities
• Patients with severe hepatic impairment
• Healthy children over 12 only
• Patients with controlled seasonal allergies

Correct Answer: Patients with severe hepatic impairment

Q46. Which of the following best describes orphenadrine’s effect on respiratory secretions?

• It increases bronchial secretions markedly
• It reduces secretions due to antimuscarinic action
• It has no effect on respiratory secretions
• It acts as a mucolytic agent

Correct Answer: It reduces secretions due to antimuscarinic action

Q47. When preparing an exam question on synthetic cholinergic blocking agents, which learning point is MOST important for B. Pharm students?

• Mechanism of action, clinical uses, adverse effects, contraindications and drug interactions
• Only the chemical synthesis steps
• Irrelevance of patient counselling
• Focus solely on storage conditions

Correct Answer: Mechanism of action, clinical uses, adverse effects, contraindications and drug interactions

Q48. Which of the following signs would MOST likely prompt immediate discontinuation of orphenadrine?

• Mild transient dry mouth
• Severe urinary retention with bladder distension
• Temporary mild sedation that improves
• Minor constipation manageable with diet

Correct Answer: Severe urinary retention with bladder distension

Q49. The use of orphenadrine in combination with which class increases the risk of severe anticholinergic effects?

• Antibiotics with no anticholinergic activity
• Other antimuscarinic or anticholinergic medications
• Topical emollients
• Vitamin supplements

Correct Answer: Other antimuscarinic or anticholinergic medications

Q50. For exam preparation, which clinical scenario best tests understanding of orphenadrine’s pharmacology?

• A patient with acute musculoskeletal pain who develops dry mouth, blurred vision and urinary retention after starting orphenadrine
• A patient with well-controlled hypertension taking no other medications
• A healthy volunteer given a topical moisturizer
• A person taking vitamin C for scurvy prevention

Correct Answer: A patient with acute musculoskeletal pain who develops dry mouth, blurred vision and urinary retention after starting orphenadrine

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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