Clopidogrel MCQs With Answer

Clopidogrel MCQs With Answer

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Clopidogrel MCQs With Answer

Clopidogrel is a thienopyridine antiplatelet prodrug widely used in cardiovascular pharmacotherapy. This introduction covers key concepts B. Pharm students must master: mechanism of action as an irreversible P2Y12 receptor inhibitor, hepatic bioactivation (notably CYP2C19), pharmacokinetics, dosing (loading and maintenance), clinical indications (ACS, stent thrombosis prevention, stroke), drug interactions (e.g., proton pump inhibitors), adverse effects (bleeding, TTP), and laboratory monitoring (VerifyNow, aggregometry). The focus is on mechanistic detail, formulation and therapeutic implications relevant to pharmacy practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which best describes the primary mechanism of action of clopidogrel?

  • Competitive reversible blockade of thromboxane A2 receptors
  • Irreversible inhibition of platelet P2Y12 ADP receptors via an active metabolite
  • Direct inhibition of cyclooxygenase-1 enzyme
  • Antagonism of glycoprotein IIb/IIIa receptor on platelets

Correct Answer: Irreversible inhibition of platelet P2Y12 ADP receptors via an active metabolite

Q2. Clopidogrel is classified chemically as which type of compound?

  • Sulfonylurea
  • Thienopyridine
  • Benzodiazepine
  • Biguanide

Correct Answer: Thienopyridine

Q3. What is the clinical significance of CYP2C19 polymorphisms in patients taking clopidogrel?

  • Polymorphisms alter absorption from the gut but not clinical effect
  • Loss-of-function alleles reduce conversion to active metabolite and decrease antiplatelet effect
  • Gain-of-function alleles cause clopidogrel accumulation and hepatic toxicity
  • Polymorphisms only affect renal clearance of clopidogrel

Correct Answer: Loss-of-function alleles reduce conversion to active metabolite and decrease antiplatelet effect

Q4. Which statement about clopidogrel pharmacokinetics is TRUE?

  • Clopidogrel is active as administered and does not require metabolism
  • It is a prodrug requiring hepatic biotransformation to an active thiol metabolite
  • It is primarily eliminated unchanged in urine
  • Clopidogrel has a long plasma half-life of the active metabolite (>24 hours)

Correct Answer: It is a prodrug requiring hepatic biotransformation to an active thiol metabolite

Q5. Typical loading and maintenance doses for clopidogrel in acute coronary syndrome are:

  • Loading 600 mg, maintenance 150 mg once daily
  • Loading 300–600 mg, maintenance 75 mg once daily
  • Loading 75 mg, maintenance 75 mg twice daily
  • No loading dose; maintenance 300 mg once daily

Correct Answer: Loading 300–600 mg, maintenance 75 mg once daily

Q6. Which adverse effect is most specifically associated (though rare) with clopidogrel?

  • Clostridium difficile infection
  • Thrombotic thrombocytopenic purpura (TTP)
  • Nephrogenic diabetes insipidus
  • Ototoxicity

Correct Answer: Thrombotic thrombocytopenic purpura (TTP)

Q7. In a patient requiring dual antiplatelet therapy after PCI with stent placement, clopidogrel is combined primarily with:

  • Warfarin
  • Aspirin
  • Heparin
  • Thrombolytic agents

Correct Answer: Aspirin

Q8. Which laboratory test is commonly used to assess platelet P2Y12 inhibition by clopidogrel?

  • Prothrombin time (PT)
  • VerifyNow P2Y12 assay
  • Serum troponin I
  • Creatinine clearance

Correct Answer: VerifyNow P2Y12 assay

Q9. Which drug interaction is of clinical concern when co-administered with clopidogrel?

  • Simvastatin causing competitive P2Y12 blockade
  • Omeprazole inhibiting CYP2C19 and reducing clopidogrel activation
  • Metformin increasing clopidogrel renal clearance
  • Warfarin enhancing clopidogrel metabolic activation

Correct Answer: Omeprazole inhibiting CYP2C19 and reducing clopidogrel activation

Q10. What is the mechanism by which clopidogrel reduces platelet aggregation?

  • Prevention of fibrinogen binding to glycoprotein IIb/IIIa
  • Inhibition of ADP-induced expression of the glycoprotein IIb/IIIa complex via P2Y12 blockade
  • Blockade of thrombin receptors on platelets
  • Inhibition of platelet-derived growth factor release

Correct Answer: Inhibition of ADP-induced expression of the glycoprotein IIb/IIIa complex via P2Y12 blockade

Q11. Platelet function typically returns to baseline how long after stopping clopidogrel?

  • Within 4–6 hours
  • After one platelet lifespan, roughly 7–10 days
  • In 24 hours with supportive therapy
  • Immediately after dialysis

Correct Answer: After one platelet lifespan, roughly 7–10 days

Q12. Which patient population should be considered for alternative therapy due to likely reduced clopidogrel response?

  • Patients with CYP2C19 loss-of-function alleles (poor metabolizers)
  • Patients with high body mass index (>30 kg/m2) only
  • Young healthy adults under 25 years
  • Patients with controlled hypothyroidism

Correct Answer: Patients with CYP2C19 loss-of-function alleles (poor metabolizers)

Q13. Which statement about clopidogrel and bleeding risk is CORRECT?

  • Clopidogrel causes coagulopathy measurable by PT/INR
  • Bleeding risk increases when clopidogrel is combined with other antithrombotics
  • Clopidogrel does not increase major bleeding risk
  • Bleeding only occurs in the presence of renal failure

Correct Answer: Bleeding risk increases when clopidogrel is combined with other antithrombotics

Q14. Which of the following best describes the active metabolite of clopidogrel?

  • Stable metabolite with prolonged half-life causing reversible inhibition
  • Short-lived thiol metabolite that irreversibly binds P2Y12 receptors
  • Inactive metabolite excreted unchanged
  • Metabolite that primarily acts on fibrinolysis pathways

Correct Answer: Short-lived thiol metabolite that irreversibly binds P2Y12 receptors

Q15. Which clinical indication is NOT a standard approved use of clopidogrel?

  • Prevention of atherothrombotic events after recent myocardial infarction or stroke
  • Prevention of stent thrombosis after percutaneous coronary intervention
  • Treatment of acute ischemic stroke as a thrombolytic agent
  • Secondary prevention in peripheral arterial disease

Correct Answer: Treatment of acute ischemic stroke as a thrombolytic agent

Q16. In which scenario is genetic testing for CYP2C19 most relevant before prescribing clopidogrel?

  • Elective cosmetic surgery patients
  • Patients undergoing high-risk PCI or with prior stent thrombosis
  • All patients with seasonal allergies
  • Patients with stable hyperlipidemia only

Correct Answer: Patients undergoing high-risk PCI or with prior stent thrombosis

Q17. Which alternative P2Y12 inhibitor is a direct-acting reversible antagonist (not a thienopyridine prodrug)?

  • Prasugrel
  • Ticagrelor
  • Clopidogrel
  • Dipyridamole

Correct Answer: Ticagrelor

Q18. Which formulation consideration is important for clopidogrel tablets in pharmacy practice?

  • Tablets must be refrigerated at 2–8°C
  • Store at room temperature away from moisture and light; do not crush extended-release forms because no ER formulation exists for clopidogrel
  • Tablets must be mixed with alkaline solution before administration
  • Only available as an intravenous formulation

Correct Answer: Store at room temperature away from moisture and light; do not crush extended-release forms because no ER formulation exists for clopidogrel

Q19. How does concomitant use of strong CYP2C19 inhibitors (e.g., omeprazole) generally affect clopidogrel therapy?

  • Increase formation of active metabolite and bleeding risk
  • Decrease formation of active metabolite, potentially reducing efficacy
  • Enhance renal excretion of clopidogrel
  • No clinically relevant interaction

Correct Answer: Decrease formation of active metabolite, potentially reducing efficacy

Q20. Which monitoring parameter is most useful to detect clopidogrel-related efficacy failure?

  • Serial PT/INR measurements
  • Platelet function testing (e.g., light transmission aggregometry or VerifyNow)
  • Serum transaminases weekly
  • Blood glucose monitoring

Correct Answer: Platelet function testing (e.g., light transmission aggregometry or VerifyNow)

Q21. Which adverse hematologic effect has been reported with clopidogrel use?

  • Aplastic anemia as a common effect
  • Neutropenia and rare cases of hematologic dyscrasias
  • Polycythemia vera induction
  • Macrocytic anemia due to folate antagonism

Correct Answer: Neutropenia and rare cases of hematologic dyscrasias

Q22. What is the recommended management if urgent surgery is required in a patient on clopidogrel?

  • Immediate platelet transfusion without stopping the drug
  • Stop clopidogrel and, if possible, delay surgery for 5–7 days to allow platelet function recovery
  • Give an extra loading dose preoperatively
  • Administer vitamin K to reverse the effect

Correct Answer: Stop clopidogrel and, if possible, delay surgery for 5–7 days to allow platelet function recovery

Q23. Which hepatic enzyme is primarily involved in the two-step bioactivation of clopidogrel to its active metabolite?

  • CYP3A4 exclusively
  • CYP2C19 among other CYP enzymes
  • CYP1A2 only
  • Monoamine oxidase

Correct Answer: CYP2C19 among other CYP enzymes

Q24. Compared with clopidogrel, prasugrel is characterized by:

  • Slower onset and less potent platelet inhibition
  • More predictable and generally greater platelet inhibition but higher bleeding risk
  • Being reversible and not requiring metabolic activation
  • Exclusive renal excretion and safer in hepatic impairment

Correct Answer: More predictable and generally greater platelet inhibition but higher bleeding risk

Q25. Which patient factor increases the risk of poor response to clopidogrel therapy?

  • High dietary fiber intake
  • Use of CYP2C19 inhibitors, diabetes mellitus, or genetic poor metabolizer status
  • Young age under 30 without comorbidities
  • Concomitant aspirin therapy

Correct Answer: Use of CYP2C19 inhibitors, diabetes mellitus, or genetic poor metabolizer status

Q26. For an acute STEMI patient undergoing primary PCI, a 600 mg loading dose of clopidogrel is preferred over 300 mg primarily because:

  • It reduces the need for anticoagulants during PCI
  • Higher loading dose achieves faster and greater platelet inhibition
  • It decreases contrast-induced nephropathy
  • It prolongs prothrombin time for anticoagulation

Correct Answer: Higher loading dose achieves faster and greater platelet inhibition

Q27. Which statement about clopidogrel use in pregnancy is most appropriate for pharmacy counseling?

  • Clopidogrel is absolutely contraindicated in all trimesters
  • Use only if clearly needed; discuss risks and benefits as data are limited
  • Clopidogrel is proven safe and recommended for routine use in pregnancy
  • Replace clopidogrel with high-dose aspirin routinely

Correct Answer: Use only if clearly needed; discuss risks and benefits as data are limited

Q28. Which adverse event would prompt immediate discontinuation and hematology referral when linked to clopidogrel?

  • Mild headache
  • Sudden thrombocytopenia with signs of hemolysis suggesting TTP
  • Transient mild nausea
  • Occasional muscle cramp

Correct Answer: Sudden thrombocytopenia with signs of hemolysis suggesting TTP

Q29. Which statement about dosing adjustment of clopidogrel in renal impairment is TRUE?

  • Clopidogrel dose must be doubled in renal failure
  • No dosage adjustment is generally required for renal impairment
  • Clopidogrel is contraindicated if creatinine clearance <60 mL/min
  • Maintenance dose should be reduced to 25 mg daily in renal impairment

Correct Answer: No dosage adjustment is generally required for renal impairment

Q30. Which pharmacologic measure can be used to overcome poor clopidogrel response due to CYP2C19 loss-of-function?

  • Increase omeprazole dose to boost absorption
  • Switch to alternative antiplatelet agents like prasugrel or ticagrelor
  • Reduce aspirin dose
  • Administer vitamin K

Correct Answer: Switch to alternative antiplatelet agents like prasugrel or ticagrelor

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