Anti-inflammatory agents – Acetaminophen MCQs With Answer

Acetaminophen is a widely used anti-inflammatory agent with predominant analgesic and antipyretic effects, essential knowledge for B. Pharm students preparing for exams and clinical practice. This concise, SEO-friendly introduction covers mechanism of action, hepatic metabolism to toxic NAPQI, pharmacokinetics, therapeutic dosing, overdose management with N-acetylcysteine, drug interactions, and formulation differences. Understanding acetaminophen’s limitations as an anti-inflammatory compared to NSAIDs, laboratory markers of toxicity, and safe use in special populations enhances prescribing and counselling skills. These MCQs emphasize mechanistic depth, clinical scenarios, and dosage calculations to strengthen exam readiness and professional competence. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which statement best describes acetaminophen’s primary mechanism of analgesic and antipyretic action?

• Irreversible COX-1 inhibition in peripheral tissues
• Selective COX-2 inhibition in inflamed tissues
• Central inhibition of prostaglandin synthesis possibly via COX-3 and modulation of serotonergic pathways
• Inhibition of leukotriene synthesis through 5-lipoxygenase blockade

Correct Answer: Central inhibition of prostaglandin synthesis possibly via COX-3 and modulation of serotonergic pathways

Q2. Which metabolic pathway produces the toxic metabolite NAPQI from acetaminophen?

• Glucuronidation
• Sulfation
• CYP-mediated oxidation (primarily CYP2E1)
• Acetylation by N-acetyltransferase

Correct Answer: CYP-mediated oxidation (primarily CYP2E1)

Q3. What is the recommended maximum daily dose of acetaminophen for a healthy adult to avoid toxicity?

• 1 gram per day
• 2 grams per day
• 3 grams per day
• 4 grams per day

Correct Answer: 4 grams per day

Q4. Which antidote is indicated for acetaminophen overdose to replenish glutathione and detoxify NAPQI?

• Flumazenil
• N-acetylcysteine (NAC)
• Activated charcoal only
• Vitamin K

Correct Answer: N-acetylcysteine (NAC)

Q5. Which laboratory test is the most useful early indicator of acetaminophen-induced hepatic injury?

• Serum creatinine
• Alanine aminotransferase (ALT)
• Prothrombin time immediately on presentation
• Serum bilirubin at 2 hours post ingestion

Correct Answer: Alanine aminotransferase (ALT)

Q6. In which clinical scenario is acetaminophen preferred over NSAIDs?

• For strong anti-inflammatory effects in rheumatoid arthritis
• In patients with peptic ulcer disease due to lower GI bleeding risk
• To reduce platelet aggregation before surgery
• As a primary disease-modifying agent in osteoarthritis

Correct Answer: In patients with peptic ulcer disease due to lower GI bleeding risk

Q7. Which pharmacokinetic property describes acetaminophen’s absorption after oral administration?

• Poor oral absorption with Tmax >8 hours
• Rapid and nearly complete absorption with Tmax around 0.5–2 hours
• Absorption only in the presence of fatty meals
• Requires enterohepatic recirculation for bioavailability

Correct Answer: Rapid and nearly complete absorption with Tmax around 0.5–2 hours

Q8. What is the major phase II metabolic pathway for acetaminophen at therapeutic doses?

• Oxidation by CYP3A4
• Glucuronidation and sulfation
• Acetylation to form acetamide
• Direct renal excretion of unchanged drug

Correct Answer: Glucuronidation and sulfation

Q9. Which population requires lower maximum daily doses of acetaminophen to reduce risk of hepatotoxicity?

• Healthy young adults
• Patients with chronic alcohol use
• Athletes with increased muscle mass
• Patients on chronic proton pump inhibitors

Correct Answer: Patients with chronic alcohol use

Q10. Which statement about acetaminophen’s anti-inflammatory effect is correct?

• It has strong peripheral anti-inflammatory activity comparable to aspirin
• It lacks significant peripheral anti-inflammatory action at usual doses
• It directly inhibits leukocyte migration in inflamed tissue
• It is the first-line anti-inflammatory for systemic lupus erythematosus

Correct Answer: It lacks significant peripheral anti-inflammatory action at usual doses

Q11. Which enzyme induction increases acetaminophen toxicity risk by enhancing NAPQI formation?

• Induction of UDP-glucuronosyltransferase
• Induction of CYP2E1 by chronic ethanol or isoniazid
• Inhibition of CYP2E1 by antibiotics
• Induction of sulfotransferases by fruits

Correct Answer: Induction of CYP2E1 by chronic ethanol or isoniazid

Q12. What is the clinical significance of acetaminophen-protein adducts measurement?

• They indicate renal tubular damage
• They are specific markers of acetaminophen hepatotoxicity
• They measure gastric mucosal injury
• They quantify platelet inhibition

Correct Answer: They are specific markers of acetaminophen hepatotoxicity

Q13. Which dosing adjustment is recommended for acetaminophen in severe hepatic impairment?

• No adjustment necessary
• Increase dose to overcome reduced efficacy
• Reduce dose and/or increase dosing interval
• Switch to high-dose intermittent therapy

Correct Answer: Reduce dose and/or increase dosing interval

Q14. Which formulation of acetaminophen provides a rapid onset suitable for intravenous use in hospital settings?

• Extended-release oral tablets
• Rectal suppository only
• IV acetaminophen (paracetamol) formulation
• Topical acetaminophen gel

Correct Answer: IV acetaminophen (paracetamol) formulation

Q15. Which adverse effect is most specifically associated with acetaminophen overdose?

• Gastrointestinal bleeding
• Acute liver failure due to centrilobular necrosis
• Bronchospasm and asthma exacerbation
• Thrombocytopenia

Correct Answer: Acute liver failure due to centrilobular necrosis

Q16. Which statement about acetaminophen and pregnancy is true?

• It is absolutely contraindicated in all trimesters
• It is generally considered safe at recommended doses during pregnancy
• It causes teratogenic effects in the first trimester at therapeutic doses
• It should be replaced by high-dose NSAIDs in pregnancy

Correct Answer: It is generally considered safe at recommended doses during pregnancy

Q17. Which laboratory nomogram is used to predict hepatotoxicity risk after acetaminophen overdose?

• MELD score
• Rumack-Matthew nomogram
• Child-Pugh score
• APACHE II score

Correct Answer: Rumack-Matthew nomogram

Q18. What is the role of activated charcoal in acetaminophen poisoning?

• Neutralizes NAPQI in the bloodstream
• Reduces gastrointestinal absorption if given within 1–2 hours of ingestion
• Replenishes glutathione stores
• Prevents hepatic necrosis when given after 24 hours

Correct Answer: Reduces gastrointestinal absorption if given within 1–2 hours of ingestion

Q19. Which co-administered drug class can increase acetaminophen hepatotoxicity by inducing CYP enzymes?

• Proton pump inhibitors
• Rifampin and other enzyme-inducing antituberculars
• H2 receptor antagonists
• Calcium channel blockers

Correct Answer: Rifampin and other enzyme-inducing antituberculars

Q20. Which metabolite pathway becomes prominent in neonates altering acetaminophen handling?

• Reduced glucuronidation and relatively increased sulfation
• Enhanced CYP2E1 activity compared to adults
• Increased renal excretion of unchanged drug
• Complete lack of sulfation pathway

Correct Answer: Reduced glucuronidation and relatively increased sulfation

Q21. What is the chemical name of acetaminophen?

• N-acetyl-para-aminophenol (paracetamol)
• 2-Acetylbenzoyl peroxide
• 4-hydroxybenzoic acid
• Acetylsalicylic acid

Correct Answer: N-acetyl-para-aminophenol (paracetamol)

Q22. Which plasma protein binding characteristic applies to acetaminophen?

• Highly protein-bound (>95%)
• Moderately protein-bound (60–80%)
• Low protein binding (~20%)
• Negligible protein binding (<1%)

Correct Answer: Low protein binding (~20%)

Q23. How does chronic alcoholism influence acetaminophen toxicity risk?

• It decreases toxicity by increasing glucuronidation capacity
• It increases toxicity via CYP2E1 induction and depleted glutathione
• It has no effect on acetaminophen metabolism
• It prevents NAPQI formation

Correct Answer: It increases toxicity via CYP2E1 induction and depleted glutathione

Q24. Which clinical sign is classically seen in the initial 24 hours after a large acetaminophen overdose?

• Marked RUQ pain and jaundice immediately
• Nonspecific symptoms like nausea, vomiting, and malaise
• Profuse bleeding and coagulopathy within 2 hours
• Severe renal colic

Correct Answer: Nonspecific symptoms like nausea, vomiting, and malaise

Q25. What is the principal route of acetaminophen elimination?

• Renal excretion of glucuronide and sulfate conjugates
• Excretion unchanged in bile
• Exhalation as CO2
• Metabolism to active metabolites excreted in sweat

Correct Answer: Renal excretion of glucuronide and sulfate conjugates

Q26. Which drug interaction with acetaminophen can potentiate hepatotoxicity?

• Concurrent use of topical emollients
• Chronic high-dose isoniazid therapy
• Co-administration with oral glucose
• Ingestion with antacids only

Correct Answer: Chronic high-dose isoniazid therapy

Q27. Which dosing regimen is appropriate for pediatric acetaminophen (oral) for fever reduction?

• 15 mg/kg per dose every 4–6 hours as needed, not to exceed recommended daily limit
• 50 mg/kg single dose once daily
• 1 mg/kg every 24 hours
• 30 mg/kg every hour until afebrile

Correct Answer: 15 mg/kg per dose every 4–6 hours as needed, not to exceed recommended daily limit

Q28. Which feature distinguishes acetaminophen from NSAIDs in analgesic therapy?

• Acetaminophen produces significant anti-platelet effects
• Acetaminophen has minimal anti-inflammatory and anti-platelet properties compared to NSAIDs
• Acetaminophen causes GI mucosal damage similar to aspirin
• Acetaminophen is a strong inhibitor of COX-1 in peripheral tissues

Correct Answer: Acetaminophen has minimal anti-inflammatory and anti-platelet properties compared to NSAIDs

Q29. Which clinical parameter is most important to monitor during N-acetylcysteine therapy?

• Serum glucose hourly
• Liver function tests and INR
• Pulmonary function tests
• Serum calcium

Correct Answer: Liver function tests and INR

Q30. Which structural feature of acetaminophen contributes to its action as an analgesic?

• Carboxylic acid group conferring COX inhibition like NSAIDs
• Para-aminophenol moiety involved in central prostaglandin inhibition
• Large lipophilic steroid nucleus
• Peptide backbone for receptor binding

Correct Answer: Para-aminophenol moiety involved in central prostaglandin inhibition

Q31. Which statement best describes acetaminophen’s effect on platelet function?

• It causes irreversible platelet inhibition
• It has negligible effect on platelet aggregation at therapeutic doses
• It enhances platelet aggregation significantly
• It selectively inhibits thromboxane synthase

Correct Answer: It has negligible effect on platelet aggregation at therapeutic doses

Q32. Which clinical situation increases the risk of delayed acetaminophen toxicity despite apparently low ingested dose?

• Co-ingestion with activated charcoal
• Co-ingestion with a CYP2E1 inhibitor
• Fasting or malnutrition leading to low glutathione stores
• Use of enteric-coated aspirin

Correct Answer: Fasting or malnutrition leading to low glutathione stores

Q33. Which organ besides the liver can be affected in severe acetaminophen toxicity?

• Lungs causing diffuse alveolar hemorrhage
• Kidneys causing acute tubular necrosis
• Pancreas causing acute pancreatitis
• Thyroid causing thyrotoxicosis

Correct Answer: Kidneys causing acute tubular necrosis

Q34. How does renal impairment affect acetaminophen dosing and safety?

• Renal impairment has no impact as acetaminophen is only hepatically cleared
• Conjugated metabolites may accumulate, so dose adjustment or monitoring is recommended in severe renal impairment
• It converts acetaminophen to more NAPQI in renal disease
• It completely prevents acetaminophen absorption

Correct Answer: Conjugated metabolites may accumulate, so dose adjustment or monitoring is recommended in severe renal impairment

Q35. Which monitoring parameter helps determine need for liver transplant after acetaminophen-induced acute liver failure?

• Serum potassium only
• MELD score and clinical criteria including INR, encephalopathy, and pH
• Blood pressure trends alone
• White blood cell count exclusively

Correct Answer: MELD score and clinical criteria including INR, encephalopathy, and pH

Q36. Which statement about combination products containing acetaminophen is critical for patient counseling?

• All cough-cold products are acetaminophen-free
• Patients must check labels to avoid inadvertent cumulative acetaminophen from multiple products
• It is safe to double dose combination products to achieve faster relief
• Combining with ibuprofen eliminates hepatotoxicity risk

Correct Answer: Patients must check labels to avoid inadvertent cumulative acetaminophen from multiple products

Q37. Which clinical effect explains acetaminophen’s antipyretic action?

• Peripheral vasoconstriction to retain heat
• Resetting the hypothalamic thermoregulatory center by reducing prostaglandin E2
• Direct cooling of the blood through sweat induction
• Stimulation of brown adipose tissue thermogenesis

Correct Answer: Resetting the hypothalamic thermoregulatory center by reducing prostaglandin E2

Q38. In a suspected acute acetaminophen overdose, which initial step is most appropriate in the emergency department?

• Wait 24 hours for ALT to rise before any intervention
• Obtain a timed serum acetaminophen concentration and use Rumack-Matthew nomogram
• Immediately start high-dose corticosteroids
• Perform immediate CT abdomen

Correct Answer: Obtain a timed serum acetaminophen concentration and use Rumack-Matthew nomogram

Q39. What is a common reason for acetaminophen therapeutic failure in clinical pain management?

• Excessive protein binding preventing penetration
• Insufficient dosing or underestimation of pain severity where opioid or NSAID adjunct may be required
• Acetaminophen causing rapid tolerance within hours
• Drug accumulation leading to paradoxical hyperalgesia

Correct Answer: Insufficient dosing or underestimation of pain severity where opioid or NSAID adjunct may be required

Q40. Which overdose patient would benefit from immediate empiric N-acetylcysteine even before lab results?

• Patient who ingested a single therapeutic dose accidentally
• Unconscious patient with history of unknown time and possible large acetaminophen ingestion
• Patient with isolated minor headache
• Patient who took only NSAIDs

Correct Answer: Unconscious patient with history of unknown time and possible large acetaminophen ingestion

Q41. Which statement about the half-life of acetaminophen is correct at therapeutic doses?

• Approximately 1–2 hours in adults
• Approximately 2–3 hours, prolonged in hepatic impairment
• More than 48 hours due to enterohepatic recycling
• Half-life is negligible because it is not metabolized

Correct Answer: Approximately 2–3 hours, prolonged in hepatic impairment

Q42. Which clinical sign indicates progression to fulminant hepatic failure after acetaminophen overdose?

• Resolution of nausea and vomiting
• Development of coagulopathy and hepatic encephalopathy
• Normalization of ALT
• Isolated mild headache improvement

Correct Answer: Development of coagulopathy and hepatic encephalopathy

Q43. Which mechanism explains why N-acetylcysteine is effective even when given late in acetaminophen poisoning?

• It permanently blocks CYP enzymes
• It replenishes intracellular glutathione and may have antioxidant, anti-inflammatory, and improved microcirculatory effects
• It directly binds NAPQI in plasma forming inert complexes
• It enhances sulfation pathways exclusively

Correct Answer: It replenishes intracellular glutathione and may have antioxidant, anti-inflammatory, and improved microcirculatory effects

Q44. Which laboratory pattern is typical in late-stage acetaminophen hepatotoxicity?

• Markedly elevated ALT/AST with rising bilirubin and prolonged INR
• Isolated elevated amylase only
• Low transaminases with normal INR
• Isolated hyperkalemia with normal liver tests

Correct Answer: Markedly elevated ALT/AST with rising bilirubin and prolonged INR

Q45. Which statement about rectal acetaminophen formulation is correct?

• Rectal bioavailability is always identical to oral immediate-release
• Rectal absorption can be variable; dosing must account for reduced and inconsistent bioavailability
• Rectal route produces no systemic absorption
• Rectal acetaminophen is preferred for chronic high-dose therapy

Correct Answer: Rectal absorption can be variable; dosing must account for reduced and inconsistent bioavailability

Q46. Which dosing frequency best describes standard adult immediate-release acetaminophen tablets?

• Every 12–24 hours
• Every 4–6 hours as needed, not to exceed maximum daily dose
• Continuous infusion only
• Once weekly dosing

Correct Answer: Every 4–6 hours as needed, not to exceed maximum daily dose

Q47. Which pharmacodynamic interaction is a concern when acetaminophen is combined with alcohol acutely?

• Acute alcohol ingestion prevents NAPQI formation thereby reducing toxicity
• Acute alcohol may inhibit CYP2E1 transiently, but chronic alcohol induces CYP2E1 increasing toxicity risk
• Alcohol enhances glucuronidation eliminating risk
• Alcohol and acetaminophen interact to cause increased platelet inhibition

Correct Answer: Acute alcohol may inhibit CYP2E1 transiently, but chronic alcohol induces CYP2E1 increasing toxicity risk

Q48. Which clinical use is NOT an approved indication for acetaminophen?

• Management of mild to moderate pain and fever
• Primary anti-inflammatory therapy for severe rheumatoid arthritis flares
• Adjunct analgesic in multimodal pain management
• Antipyretic in pediatric fever management

Correct Answer: Primary anti-inflammatory therapy for severe rheumatoid arthritis flares

Q49. Which statement about acetaminophen metabolism variability is correct?

• Genetic polymorphisms have no effect on acetaminophen metabolism
• Polymorphisms in UGT and SULT enzymes can alter phase II metabolism and affect susceptibility to toxicity
• CYP enzymes exclusively determine acetaminophen therapeutic effect
• Sulfation pathway is absent in all adults

Correct Answer: Polymorphisms in UGT and SULT enzymes can alter phase II metabolism and affect susceptibility to toxicity

Q50. Which counseling point is most important for a pharmacist advising a patient taking nightly acetaminophen for chronic headache?

• Encourage exceeding the label dose to ensure relief
• Assess total daily acetaminophen intake from all products and avoid chronic high-dose use due to hepatotoxicity risk
• Recommend combining with multiple over-the-counter cold products for added effect
• Tell the patient that prolonged use has no risks and requires no monitoring

Correct Answer: Assess total daily acetaminophen intake from all products and avoid chronic high-dose use due to hepatotoxicity risk

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.

Mail- Sachin@pharmacyfreak.com