Opioid antagonists MCQs With Answer

Introduction

Opioid antagonists MCQs With Answer provide B. Pharm students a focused review of pharmacology, mechanism, clinical use and safety of agents such as naloxone, naltrexone, nalmefene and peripheral antagonists (methylnaltrexone). This concise, keyword-rich introduction covers opioid receptors (mu, delta, kappa), competitive antagonism, precipitated withdrawal, overdose reversal, routes and pharmacokinetics, and therapeutic roles in addiction and opioid-induced constipation. Designed for exam preparation and deeper understanding, these questions emphasize receptor affinity, onset/duration, clinical scenarios and important drug interactions. Clear explanations reinforce core concepts needed in pharmacy practice and therapeutics. ‘Now let’s test your knowledge with 30 MCQs on this topic.’

Q1. Which of the following best describes the primary mechanism of action of naloxone?

• Agonist at mu-opioid receptors
• Competitive antagonist at opioid receptors
• Irreversible antagonist at opioid receptors
• Monoamine reuptake inhibitor

Correct Answer: Competitive antagonist at opioid receptors

Q2. Which opioid receptor subtype is most responsible for analgesia and respiratory depression targeted by opioid antagonists?

• Delta (δ) receptor
• Kappa (κ) receptor
• Mu (μ) receptor
• Nociceptin receptor

Correct Answer: Mu (μ) receptor

Q3. Which clinical situation is naloxone most commonly indicated for?

• Chronic neuropathic pain management
• Acute opioid overdose with respiratory depression
• Maintenance therapy for opioid dependence
• Opioid-induced constipation only

Correct Answer: Acute opioid overdose with respiratory depression

Q4. Compared to naloxone, naltrexone differs primarily by which characteristic?

• Faster onset of action
• Longer duration of antagonism when given orally
• Selective kappa agonism
• Exclusive peripheral activity

Correct Answer: Longer duration of antagonism when given orally

Q5. A major clinical risk when giving naloxone to opioid-dependent patients is:

• Prolonged sedation
• Precipitated withdrawal
• Hypertensive crisis due to MAOI interaction
• Serotonin syndrome

Correct Answer: Precipitated withdrawal

Q6. Which property of buprenorphine explains its ability to block effects of full opioid agonists?

• Low receptor affinity with rapid dissociation
• High affinity partial agonist at mu receptors
• Full agonist at delta receptors
• Non-competitive antagonism at mu receptors

Correct Answer: High affinity partial agonist at mu receptors

Q7. Which antagonist is a peripherally acting opioid antagonist primarily used for opioid-induced constipation?

• Naltrexone
• Nalmefene
• Methylnaltrexone
• Naloxone

Correct Answer: Methylnaltrexone

Q8. One pharmacokinetic concern with naloxone is:

• Very long half-life causing prolonged blockade
• Short half-life leading to possible renarcotization
• High oral bioavailability
• Hepatic accumulation causing delayed onset

Correct Answer: Short half-life leading to possible renarcotization

Q9. Which route provides the fastest onset of action for naloxone in emergency reversal?

• Oral
• Intranasal
• Intravenous
• Subcutaneous

Correct Answer: Intravenous

Q10. Naltrexone is commonly used in which of the following therapeutic roles?

• Acute opioid overdose reversal in the emergency room
• Maintenance therapy to reduce alcohol craving and prevent opioid relapse
• First-line analgesic for severe pain
• Treatment of opioid-induced constipation

Correct Answer: Maintenance therapy to reduce alcohol craving and prevent opioid relapse

Q11. Nalmefene differs from naloxone in that it:

• Has no activity at opioid receptors
• Has a longer duration of action than naloxone
• Is only used orally for alcohol dependence
• Acts as a selective delta agonist

Correct Answer: Has a longer duration of action than naloxone

Q12. Which statement about naloxone and pregnancy is most accurate?

• Naloxone is absolutely contraindicated in pregnancy
• Naloxone may be used in maternal opioid overdose to restore respiration, with caution for precipitated fetal withdrawal
• Naloxone causes teratogenic effects in animal studies
• Naloxone is ineffective in neonates and should not be used

Correct Answer: Naloxone may be used in maternal opioid overdose to restore respiration, with caution for precipitated fetal withdrawal

Q13. Which pharmacodynamic term describes drugs like naloxone that compete with agonists at the same receptor site?

• Allosteric modulator
• Non-competitive antagonist
• Competitive antagonist
• Partial agonist

Correct Answer: Competitive antagonist

Q14. A high-affinity partial agonist can produce which clinical effect compared to full agonists?

• Greater maximal respiratory depression
• Ceiling effect on respiratory depression and analgesia
• Irreversible receptor activation
• Enhanced risk of serotonin toxicity

Correct Answer: Ceiling effect on respiratory depression and analgesia

Q15. Which laboratory parameter or test is essential before starting oral naltrexone for opioid-dependent patients?

• Serum creatinine only
• Liver function tests (LFTs)
• Thyroid function tests
• Electrocardiogram in all patients

Correct Answer: Liver function tests (LFTs)

Q16. Which clinical consequence is most likely when a long-acting opioid is reversed with a single dose of naloxone?

• Permanent opioid tolerance
• Immediate and permanent cure of dependence
• Temporary reversal followed by renarcotization as naloxone wears off
• No effect because naloxone cannot reverse long-acting opioids

Correct Answer: Temporary reversal followed by renarcotization as naloxone wears off

Q17. Which opioid antagonist is available as a long-acting depot injection for relapse prevention?

• Intranasal naloxone
• Oral naloxone tablets
• Extended-release injectable naltrexone
• Methylnaltrexone subcutaneous infusion

Correct Answer: Extended-release injectable naltrexone

Q18. Peripheral opioid antagonists like methylnaltrexone are designed to:

• Cross the blood–brain barrier to reverse CNS effects
• Block peripheral opioid receptors to treat constipation without affecting analgesia
• Act as long-acting central antagonists for relapse prevention
• Enhance mu receptor signaling in the gut

Correct Answer: Block peripheral opioid receptors to treat constipation without affecting analgesia

Q19. Which factor increases the likelihood that naloxone will precipitate severe withdrawal?

• Administration to opioid-naïve patient
• Giving naloxone slowly in low incremental doses
• High-dose naloxone given to a chronically opioid-dependent patient
• Use of peripheral antagonists only

Correct Answer: High-dose naloxone given to a chronically opioid-dependent patient

Q20. In opioid overdose, the first sign that naloxone is effective is usually:

• Immediate resolution of miosis
• Improvement in respiratory rate and consciousness
• Onset of severe pain
• Development of fever

Correct Answer: Improvement in respiratory rate and consciousness

Q21. Which statement about naloxone’s bioavailability is correct?

• Oral naloxone has high bioavailability and is preferred for overdose
• Intranasal naloxone provides noninvasive systemic delivery with variable bioavailability
• Subcutaneous naloxone is always ineffective
• Naloxone is highly protein bound and accumulates in adipose tissue causing prolonged effect

Correct Answer: Intranasal naloxone provides noninvasive systemic delivery with variable bioavailability

Q22. Which of the following is a contraindication to initiating naltrexone therapy?

• Current physiological opioid dependence or positive opioid urine screen
• History of treated alcohol dependence
• Stable abstinence from opioids for >7–10 days
• Prior failure of behavioral therapy alone

Correct Answer: Current physiological opioid dependence or positive opioid urine screen

Q23. Which opioid antagonist has the longest duration of action when administered parenterally among commonly used agents?

• Naloxone
• Nalmefene
• Methylnaltrexone
• Buprenorphine

Correct Answer: Nalmefene

Q24. An advantage of intranasal naloxone kits for community use is:

• They require advanced airway skills to administer
• They minimize need for needle handling and are easily used by bystanders
• They have 100% bioavailability compared to IV
• They permanently prevent opioid relapse

Correct Answer: They minimize need for needle handling and are easily used by bystanders

Q25. Which receptor interaction is most associated with dysphoria and psychotomimetic effects that some antagonists or agonists may influence?

• Mu receptor activation
• Delta receptor blockade
• Kappa receptor activation
• Nociceptin receptor antagonism

Correct Answer: Kappa receptor activation

Q26. Which is true regarding naloxone dosing strategy in suspected opioid overdose?

• Give a single large bolus dose to minimize renarcotization
• Start with titrated small doses to restore adequate ventilation and reduce precipitated withdrawal
• Only administer after full respiratory arrest has occurred
• Administer orally for fastest effect

Correct Answer: Start with titrated small doses to restore adequate ventilation and reduce precipitated withdrawal

Q27. Which metabolic pathway is primarily responsible for naltrexone clearance?

• Renal excretion unchanged only
• Hepatic metabolism with active metabolites
• Pulmonary elimination
• Conjugation in the gut lumen only

Correct Answer: Hepatic metabolism with active metabolites

Q28. Which patient population benefits most from methylnaltrexone therapy?

• Opioid-naïve patients with diarrhea
• Patients on chronic opioids suffering from opioid-induced constipation who need peripheral antagonism
• Patients needing acute reversal of CNS opioid effects
• Patients with alcohol use disorder receiving naltrexone

Correct Answer: Patients on chronic opioids suffering from opioid-induced constipation who need peripheral antagonism

Q29. Which phenomenon explains why high-affinity partial agonists can displace full agonists from receptors?

• Higher intrinsic activity compared to full agonists
• Greater receptor affinity and slower dissociation kinetics
• Irreversible covalent binding to receptors
• Allosteric enhancement of full agonist binding

Correct Answer: Greater receptor affinity and slower dissociation kinetics

Q30. In designing MCQs for B. Pharm students on opioid antagonists, which focus best promotes deeper learning?

• Only memorizing brand names
• Integrating mechanism, pharmacokinetics, clinical scenarios and safety considerations
• Exclusively testing rare anecdotal case reports
• Focusing solely on cost comparisons

Correct Answer: Integrating mechanism, pharmacokinetics, clinical scenarios and safety considerations

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