Narcotic antagonists – Nalorphine hydrochloride MCQs With Answer

Narcotic antagonists – Nalorphine hydrochloride MCQs With Answer

Nalorphine hydrochloride is a classical opioid antagonist and mixed agonist-antagonist important in pharmacology education for B.Pharm students. This topic covers mechanism of action, receptor selectivity (mu, kappa, delta), clinical uses, adverse effects, pharmacokinetics, drug interactions, and differences from modern antagonists like naloxone. Understanding nalorphine’s competitive antagonism at mu receptors and kappa agonism helps explain withdrawal precipitation and dysphoric side effects. These MCQs focus on core concepts, therapeutic implications, and exam-relevant details to strengthen your grasp of narcotic antagonists and opioid pharmacology. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which receptor action best describes nalorphine?

• Full mu receptor agonist
• Competitive mu antagonist and kappa agonist
• Selective delta receptor agonist
• Non-competitive NMDA antagonist

Correct Answer: Competitive mu antagonist and kappa agonist

Q2. Nalorphine hydrochloride is best classified as which of the following?

• Pure opioid agonist
• Mixed opioid agonist-antagonist
• Non-opioid analgesic
• Synthetic cannabinoid

Correct Answer: Mixed opioid agonist-antagonist

Q3. The common clinical effect produced by nalorphine due to kappa receptor activation is:

• Euphoria
• Dysphoria and hallucinations
• Strong analgesia without side effects
• Bronchodilation

Correct Answer: Dysphoria and hallucinations

Q4. Nalorphine can precipitate which condition in opioid-dependent patients?

• Enhanced analgesia
• Opioid withdrawal syndrome
• Prolonged sedation without withdrawal
• Serotonin syndrome

Correct Answer: Opioid withdrawal syndrome

Q5. Compared with naloxone, nalorphine is:

• More selective for delta receptors
• Less likely to cause dysphoria
• A mixed antagonist with kappa agonist activity
• Not an opioid receptor ligand

Correct Answer: A mixed antagonist with kappa agonist activity

Q6. The primary mechanism by which nalorphine reverses opioid-induced respiratory depression is:

• Enhancing GABAergic inhibition
• Competitive antagonism at mu opioid receptors
• Inhibiting cytochrome P450 enzymes
• Blocking NMDA receptors

Correct Answer: Competitive antagonism at mu opioid receptors

Q7. Nalorphine hydrochloride is administered in which chemical form for clinical use?

• Free base only
• Hydrochloride salt
• Sodium phosphate ester
• As a lipid emulsion

Correct Answer: Hydrochloride salt

Q8. Which pharmacological property explains nalorphine’s ability to block morphine analgesia?

• Irreversible receptor binding
• Competitive antagonism at mu receptors
• Enhancement of morphine metabolism
• Activation of peripheral alpha receptors

Correct Answer: Competitive antagonism at mu receptors

Q9. A major adverse effect associated with nalorphine related to its kappa activity is:

• Severe hypotension without CNS effects
• Psychotomimetic effects and dysphoria
• Excessive euphoria leading to abuse
• Nephrotoxicity

Correct Answer: Psychotomimetic effects and dysphoria

Q10. Nalorphine’s clinical use has declined mainly because:

• It is too selective for mu receptors
• More effective and safer antagonists like naloxone are available
• It is a non-opioid and irrelevant for opioid toxicity
• It cannot cross the blood–brain barrier

Correct Answer: More effective and safer antagonists like naloxone are available

Q11. Which statement about nalorphine’s onset and duration is generally correct?

• Very slow onset and extremely long duration compared with naloxone
• Rapid onset with variable duration; often longer than naloxone
• No central effects due to inability to penetrate CNS
• Onset and duration identical to morphine

Correct Answer: Rapid onset with variable duration; often longer than naloxone

Q12. Nalorphine binds to which opioid receptor subtypes?

• Only mu receptors
• Mu and kappa receptors predominantly
• Only delta receptors
• Only non-opioid receptors

Correct Answer: Mu and kappa receptors predominantly

Q13. In pharmacology, nalorphine is often used experimentally to:

• Enhance opioid analgesia
• Delineate mu vs kappa mediated effects
• Act as an antidepressant
• Inhibit acetylcholinesterase

Correct Answer: Delineate mu vs kappa mediated effects

Q14. Which of the following best describes nalorphine’s effect on pain in non-opioid-dependent patients?

• Produces profound analgesia without side effects
• May provide modest analgesia via kappa agonism but causes dysphoria
• Has no effect on pain perception
• Causes analgesia and euphoria

Correct Answer: May provide modest analgesia via kappa agonism but causes dysphoria

Q15. The risk when administering nalorphine to a patient on high-dose opioids is primarily:

• Cardiac arrest unrelated to opioid effects
• Massive parasympathetic stimulation
• Sudden and severe opioid withdrawal
• Development of tolerance to benzodiazepines

Correct Answer: Sudden and severe opioid withdrawal

Q16. Which laboratory process is primarily responsible for nalorphine metabolism?

• Renal excretion of unchanged drug only
• Hepatic metabolism (biotransformation)
• Excretion through bile unchanged
• Metabolism by gut microbiota only

Correct Answer: Hepatic metabolism (biotransformation)

Q17. Nalorphine’s ability to reverse opioid effects is due to which pharmacodynamic principle?

• Non-competitive antagonism that destroys receptors
• Competitive receptor blockade at opioid binding sites
• Direct enzymatic degradation of opioids
• Sequestration of opioids in plasma

Correct Answer: Competitive receptor blockade at opioid binding sites

Q18. Which clinical scenario is nalorphine historically indicated for?

• Treatment of bacterial infections
• Reversal of opioid-induced respiratory depression
• Chronic neuropathic pain management
• Long-term opioid maintenance therapy

Correct Answer: Reversal of opioid-induced respiratory depression

Q19. A difference between nalorphine and naloxone is that nalorphine:

• Is a pure antagonist with no agonist effects
• Has kappa agonist activity leading to dysphoria
• Is exclusively peripheral in action
• Is an NMDA receptor agonist

Correct Answer: Has kappa agonist activity leading to dysphoria

Q20. Nalorphine hydrochloride chemically is derived from which parent structure?

• Phenothiazine nucleus
• Morphine (opiate) structure
• Benzodiazepine core
• Barbiturate scaffold

Correct Answer: Morphine (opiate) structure

Q21. Which adverse cardiac effect may occur after rapid reversal of opioid toxicity with antagonists like nalorphine?

• Bradycardia without hypertension
• Tachycardia and hypertension due to acute withdrawal
• Complete heart block independent of withdrawal
• Prolonged QT unrelated to autonomic changes

Correct Answer: Tachycardia and hypertension due to acute withdrawal

Q22. For examination purposes, nalorphine is often contrasted with naloxone because naloxone:

• Is a kappa agonist like nalorphine
• Is a pure opioid antagonist with minimal agonist effects
• Has stronger dysphoric effects than nalorphine
• Is used primarily as an antidepressant

Correct Answer: Is a pure opioid antagonist with minimal agonist effects

Q23. Which clinical sign would most strongly suggest opioid overdose reversible by nalorphine?

• Hyperreflexia and agitation
• Pinpoint pupils, respiratory depression, reduced consciousness
• Pale, hot, dry skin without miosis
• Profound hypertension and diaphoresis

Correct Answer: Pinpoint pupils, respiratory depression, reduced consciousness

Q24. Nalorphine’s psychotomimetic effects are mediated principally through activation of which receptor?

• Mu receptor agonism
• Kappa receptor agonism
• Delta receptor blockade
• Peripheral opioid receptors only

Correct Answer: Kappa receptor agonism

Q25. Which statement about nalorphine’s role in modern practice is true?

• It is first-line in all opioid overdoses worldwide
• It is largely historical, replaced by naloxone and naltrexone for most uses
• It is commonly used for chronic pain management
• It is the preferred agent for opioid maintenance therapy

Correct Answer: It is largely historical, replaced by naloxone and naltrexone for most uses

Q26. Which complication is most likely if nalorphine is given to a patient with mixed overdose (opioids plus stimulants)?

• Complete resolution of stimulant toxicity
• Unmasking of stimulant-induced agitation and hypertension
• Prevention of stimulant cardiotoxicity
• Enhancement of opioid-induced sedation

Correct Answer: Unmasking of stimulant-induced agitation and hypertension

Q27. Which pharmacological test in the lab might use nalorphine to differentiate receptor subtype effects?

• Beta-adrenergic receptor assay
• Opioid receptor binding competition assays
• Acetylcholine esterase inhibition assay
• Cyclooxygenase activity measurement

Correct Answer: Opioid receptor binding competition assays

Q28. When teaching drug interactions, nalorphine is cited because it can:

• Potentiate benzodiazepines synergistically
• Precipitate withdrawal when combined with full opioid agonists
• Block acetaminophen toxicity
• Enhance opioid metabolism via induction

Correct Answer: Precipitate withdrawal when combined with full opioid agonists

Q29. Nalorphine’s route of elimination primarily involves:

• Exhalation unchanged via lungs
• Hepatic metabolism followed by renal excretion of metabolites
• Sweat and salivary excretion primarily
• Direct biliary excretion unchanged only

Correct Answer: Hepatic metabolism followed by renal excretion of metabolites

Q30. Which property of nalorphine contributes to limited therapeutic use?

• High selectivity for peripheral opioid receptors only
• Agonist activity at kappa receptors causing unpleasant CNS effects
• Complete lack of CNS penetration
• Excessive oral bioavailability with long half-life

Correct Answer: Agonist activity at kappa receptors causing unpleasant CNS effects

Q31. Nalorphine is most likely to be taught in B.Pharm pharmacology as an example of:

• A selective serotonin reuptake inhibitor
• A mixed agonist-antagonist opioid
• A local anesthetic prototype
• An antiplatelet agent

Correct Answer: A mixed agonist-antagonist opioid

Q32. Which symptom would suggest nalorphine was working in an opioid-intoxicated patient?

• Increased miosis and depressed respiration
• Improved respiratory rate and increased consciousness
• Progressive hypothermia
• Worsening sedation without change in respiration

Correct Answer: Improved respiratory rate and increased consciousness

Q33. Nalorphine’s clinical disadvantages include all except:

• Precipitation of withdrawal
• Kappa-mediated dysphoria
• High abuse potential similar to morphine
• Availability of better alternatives

Correct Answer: High abuse potential similar to morphine

Q34. For exam-style receptor questions: nalorphine acts as a competitive antagonist at mu receptors because it:

• Irreversibly inactivates the receptor
• Competes with agonists at the same binding site
• Enhances agonist-induced receptor activation
• Stimulates receptor internalization permanently

Correct Answer: Competes with agonists at the same binding site

Q35. In toxicology lectures, nalorphine is historically significant because it was among the first agents used to:

• Treat hypertensive emergencies
• Antagonize opioid overdoses
• Manage diabetic ketoacidosis
• Reverse benzodiazepine sedation

Correct Answer: Antagonize opioid overdoses

Q36. Which best explains why nalorphine can both reverse opioid effects and cause some analgesia?

• It is a mixture of two separate drugs
• Kappa receptor agonism provides analgesia while mu antagonism blocks opioid analgesia
• It does not cross the blood–brain barrier
• It irreversibly blocks all opioid receptors

Correct Answer: Kappa receptor agonism provides analgesia while mu antagonism blocks opioid analgesia

Q37. When designing an MCQ on nalorphine metabolism, which enzyme system would most likely be relevant?

• Monoamine oxidase in plasma
• Cytochrome P450 hepatic enzymes
• Cholinesterases in red blood cells
• Pancreatic lipases

Correct Answer: Cytochrome P450 hepatic enzymes

Q38. Which patient population requires extreme caution when considering nalorphine use?

• Patients with acute opioid overdose needing reversal but opioid-dependent
• Patients with seasonal allergies only
• Patients taking no medications at all
• Healthy individuals with no prior opioid exposure

Correct Answer: Patients with acute opioid overdose needing reversal but opioid-dependent

Q39. In receptor affinity studies, nalorphine is likely to show high affinity for:

• Mu and kappa opioid receptors
• Beta-adrenergic receptors
• Histamine H2 receptors
• Muscarinic acetylcholine receptors

Correct Answer: Mu and kappa opioid receptors

Q40. Which therapeutic objective is NOT appropriate for nalorphine?

• Immediate reversal of life-threatening opioid-induced respiratory depression
• Chronic maintenance therapy for opioid dependence instead of methadone
• Pharmacological research into opioid receptor function
• Educational demonstration of mixed agonist-antagonist properties

Correct Answer: Chronic maintenance therapy for opioid dependence instead of methadone

Q41. A key teaching point about nalorphine pharmacology is that antagonists that also have agonist activity can:

• Have no clinical effects at all
• Produce complex outcomes including reversal and novel side effects
• Always be safer than pure antagonists
• Be used interchangeably with full agonists

Correct Answer: Produce complex outcomes including reversal and novel side effects

Q42. Which monitoring is essential after giving an opioid antagonist like nalorphine for overdose?

• Continuous respiratory and cardiovascular monitoring
• Only blood glucose checks
• No monitoring required once patient awakens
• Monitoring of skin pH only

Correct Answer: Continuous respiratory and cardiovascular monitoring

Q43. Nalorphine’s historical significance in B.Pharm curriculum mainly lies in illustrating:

• Principles of antibiotic resistance
• Opioid receptor pharmacology and antagonist strategies
• Dietary supplement interactions
• Mechanisms of anticoagulants

Correct Answer: Opioid receptor pharmacology and antagonist strategies

Q44. Which clinical effect differentiates nalorphine from a pure antagonist in terms of patient experience?

• Complete abolishment of all side effects
• Induction of dysphoria or psychotomimetic sensations
• Production of euphoria and dependence
• Absence of CNS penetration

Correct Answer: Induction of dysphoria or psychotomimetic sensations

Q45. In drug design, nalorphine is an example showing that modifying an opioid structure can:

• Convert an agonist into a mixed agonist-antagonist
• Make it non-bioactive completely
• Ensure it binds only to peripheral receptors
• Prevent any receptor binding

Correct Answer: Convert an agonist into a mixed agonist-antagonist

Q46. Which contraindication is most relevant to nalorphine administration?

• Known allergy to penicillin
• Patients actively dependent on opioids where precipitated withdrawal is dangerous
• History of migraine headaches only
• Use in patients with stable chronic pain who need continuous opioid therapy without interruption

Correct Answer: Patients actively dependent on opioids where precipitated withdrawal is dangerous

Q47. Nalorphine’s effect on gastrointestinal motility compared to full opioid agonists is expected to be:

• Similar constipating effects due to peripheral mu antagonism
• Complex: may reverse some mu-mediated effects but kappa activity may still influence motility
• Profound prokinetic action always
• No effect because it is not an opioid derivative

Correct Answer: Complex: may reverse some mu-mediated effects but kappa activity may still influence motility

Q48. For B.Pharm students learning assay techniques, nalorphine could be useful as a standard in:

• Opioid receptor binding assays and competitive displacement studies
• Measuring blood glucose by enzymatic assay
• Assessing antibiotic potency against Gram-negative bacteria
• Evaluating vitamin levels in serum

Correct Answer: Opioid receptor binding assays and competitive displacement studies

Q49. Which effect is least likely with nalorphine administration?

• Precipitation of opioid withdrawal
• Kappa-mediated dysphoria
• Strong, prolonged opioid-like euphoria
• Reversal of respiratory depression caused by opioids

Correct Answer: Strong, prolonged opioid-like euphoria

Q50. When preparing exam notes, a concise statement about nalorphine would be:

• A pure mu agonist often used for chronic pain
• A mixed mu antagonist/kappa agonist historically used to reverse opioid effects but limited by dysphoria
• An antibiotic with opioid-like side effects
• A benzodiazepine receptor antagonist

Correct Answer: A mixed mu antagonist/kappa agonist historically used to reverse opioid effects but limited by dysphoria

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