Pharmacology Quiz: Opioids
20 questions · exam conditions
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OpioidsQuestion 1 of 20

A patient receiving long-term methadone therapy for opioid use disorder is diagnosed with tuberculosis and started on a standard multi-drug regimen that includes rifampin. Within ten days, the patient reports symptoms of opioid withdrawal, including myalgia and intense cravings. This clinical presentation is best explained by rifampin's effect as a potent...

inducer of cytochrome P450 3A4 (CYP3A4), accelerating methadone metabolism.
inhibitor of cytochrome P450 2D6 (CYP2D6), shunting methadone to inactive pathways.
competitive antagonist at the mu-opioid receptor, blocking methadone's effects.
inducer of P-glycoprotein in the blood-brain barrier, reducing methadone's CNS penetration.
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Pharmacology Quiz

Pharmacology Quiz: Opioids

Practice Opioids in Pharmacology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Opioids, giving you a quick way to practice the rules, question types, and explanations that matter most for Pharmacology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A patient receiving long-term methadone therapy for opioid use disorder is diagnosed with tuberculosis and started on a standard multi-drug regimen that includes rifampin. Within ten days, the patient reports symptoms of opioid withdrawal, including myalgia and intense cravings. This clinical presentation is best explained by rifampin's effect as a potent...

  1. inducer of cytochrome P450 3A4 (CYP3A4), accelerating methadone metabolism. (correct answer)
  2. inhibitor of cytochrome P450 2D6 (CYP2D6), shunting methadone to inactive pathways.
  3. competitive antagonist at the mu-opioid receptor, blocking methadone's effects.
  4. inducer of P-glycoprotein in the blood-brain barrier, reducing methadone's CNS penetration.
Explanation: Methadone is primarily metabolized by CYP3A4 and CYP2B6. Rifampin is a powerful inducer of multiple CYP enzymes, most notably CYP3A4. By inducing these enzymes, rifampin significantly increases the metabolic clearance of methadone, leading to lower plasma concentrations and the onset of withdrawal symptoms in a patient on a stable maintenance dose. This is a classic and clinically significant drug-drug interaction.

Question 2

A patient on long-term, high-dose opioid therapy reports that their baseline pain has worsened and has spread to areas not previously affected. They also describe an increased sensitivity to normally non-painful stimuli. This clinical picture is most consistent with the development of...

  1. pharmacokinetic tolerance, requiring dose escalation.
  2. opioid-induced hyperalgesia. (correct answer)
  3. a factitious disorder motivated by drug-seeking behavior.
  4. severe, untreated opioid-induced constipation.
Explanation: Opioid-induced hyperalgesia (OIH) is a paradoxical phenomenon where chronic opioid use leads to a pro-nociceptive state, causing an increase in pain sensitivity. It is distinct from tolerance, which is a decreased effect from the same dose. OIH involves neuroplastic changes in the peripheral and central nervous systems, such as activation of NMDA receptors and enhanced descending pain facilitation pathways. Clinically, it presents as worsening pain, pain spreading, and allodynia, despite escalating opioid doses.

Question 3

An opioid-naïve patient is given an intravenous dose of morphine. Which of the following physiological effects is mediated by opioid receptors located outside the central nervous system?

  1. Respiratory depression
  2. Euphoria
  3. Analgesia
  4. Reduced gastrointestinal motility (correct answer)
Explanation: While opioids have profound CNS effects, they also act on peripheral receptors. The gastrointestinal tract is densely populated with mu-opioid receptors in the myenteric and submucosal plexuses. Agonism at these receptors inhibits acetylcholine release, which decreases peristaltic contractions, increases segmental contractions, and increases sphincter tone, leading to constipation. Respiratory depression, euphoria, and the central component of analgesia are all mediated by receptors within the CNS.

Question 4

One of the key cellular adaptations leading to opioid tolerance is the functional uncoupling of the mu-opioid receptor from its G-protein, followed by receptor internalization. Which of the following intracellular processes is most critical for initiating this desensitization?

  1. Receptor phosphorylation by G-protein coupled receptor kinases (GRKs) and subsequent binding of β-arrestin. (correct answer)
  2. Upregulation of genes coding for endogenous opioid peptides like endorphins.
  3. Permanent downregulation of adenylyl cyclase, leading to a profound decrease in cAMP.
  4. Increased expression of drug-metabolizing enzymes within the neuron.
Explanation: The development of acute pharmacodynamic tolerance begins with the phosphorylation of the activated mu-opioid receptor by GRKs. This phosphorylation event increases the receptor's affinity for a protein called β-arrestin. The binding of β-arrestin to the receptor physically blocks its interaction with the G-protein (uncoupling) and targets the receptor for clathrin-mediated endocytosis (internalization), removing it from the cell surface and reducing the cell's responsiveness to the agonist.

Question 5

A patient in the emergency department for an opioid overdose is given several doses of intravenous naloxone. The patient awakens but is extremely agitated, combative, and complains of 10/10 diffuse body pain. This response is a direct consequence of naloxone's action as a...

  1. non-competitive antagonist that irreversibly binds to mu-opioid receptors.
  2. partial agonist with a ceiling effect, providing inadequate analgesia.
  3. competitive antagonist that displaces the opioid from its receptors, unmasking withdrawal and underlying pain. (correct answer)
  4. pro-convulsant agent that directly stimulates the central nervous system.
Explanation: Naloxone is a pure, competitive antagonist at opioid receptors, with the highest affinity for the mu-receptor. In an overdose situation, it rapidly displaces the agonist (e.g., heroin, fentanyl) from these receptors, reversing the life-threatening respiratory depression. However, this action also abruptly reverses the analgesic and euphoric effects and, in a physically dependent individual, precipitates an acute, severe withdrawal syndrome characterized by pain, agitation, and autonomic hyperactivity.

Question 6

A patient is brought to the emergency department after an overdose of methadone. They are given an IV bolus of naloxone and their respiratory rate improves from 4 to 16 breaths per minute. One hour later, a nurse finds the patient somnolent with a respiratory rate of 6 breaths per minute. This recurrence of respiratory depression is best explained by...

  1. the development of acute tolerance to the effects of naloxone.
  2. the redistribution of methadone from peripheral tissues back into the central nervous system.
  3. a shorter duration of action of naloxone compared to the long duration of action of methadone. (correct answer)
  4. naloxone's metabolism being saturated, leading to a rapid decline in plasma concentration.
Explanation: This is a critical concept in overdose management. Naloxone has a relatively short half-life (30-90 minutes). Methadone is a very long-acting opioid with a half-life that can exceed 24 hours. A single bolus of naloxone can temporarily reverse the overdose, but as the naloxone is metabolized and cleared, the methadone remaining in the body re-occupies the opioid receptors, leading to a return of life-threatening respiratory depression (re-narcosis). This necessitates continuous patient monitoring and often requires repeated naloxone doses or a continuous infusion.

Question 7

A patient requires analgesia for moderate pain. The selected agent is a weak mu-opioid receptor agonist that also significantly inhibits the reuptake of both norepinephrine and serotonin. Which drug matches this pharmacological profile?

  1. Tapentadol
  2. Tramadol (correct answer)
  3. Methadone
  4. Oxycodone
Explanation: Tramadol is an atypical analgesic with a dual mechanism of action. It is a weak agonist at the mu-opioid receptor, and its primary metabolite, O-desmethyltramadol, is a more potent mu-agonist. Additionally, tramadol and its metabolite inhibit the reuptake of both norepinephrine and serotonin, which contributes to analgesia via descending inhibitory pain pathways. Tapentadol is also a dual-mechanism agent, but it is a moderate mu-agonist and primarily a norepinephrine reuptake inhibitor with little effect on serotonin.

Question 8

A patient with a known seizure disorder is experiencing severe pain. The use of which of the following opioids should be approached with the most caution due to its propensity to lower the seizure threshold, particularly in high doses or with co-administration of other serotonergic drugs?

  1. Morphine
  2. Fentanyl
  3. Hydromorphone
  4. Tramadol (correct answer)
Explanation: When evaluating opioid safety in patients with seizure disorders, you need to consider each medication's unique mechanism of action and side effect profile beyond standard opioid receptor binding. Tramadol (D) is the correct answer because it has a dual mechanism that significantly increases seizure risk. Unlike traditional opioids, tramadol not only binds to opioid receptors but also inhibits the reuptake of serotonin and norepinephrine. This serotonergic activity, combined with its active metabolite M1, can lower the seizure threshold, especially at higher doses or when combined with other serotonergic medications like SSRIs or MAOIs. The risk is particularly pronounced in patients with pre-existing seizure disorders. The other options pose much lower seizure risk: Morphine (A) is a pure opioid receptor agonist with minimal effect on neurotransmitter reuptake systems. Fentanyl (B), while potent, primarily acts through opioid receptors without significant serotonergic activity. Hydromorphone (C) is also a traditional opioid agonist without the dual mechanism that makes tramadol problematic. Study tip: Remember that tramadol is the "atypical opioid" with serotonergic properties. When you see seizure-related questions involving pain medications, immediately consider tramadol's unique dual mechanism. Also watch for contraindications involving tramadol with other serotonergic drugs - this combination creates a perfect storm for seizure activity in susceptible patients.

Question 9

A patient develops intense facial and truncal pruritus shortly after receiving an intrathecal injection of morphine for postoperative analgesia. This localized itching is primarily caused by...

  1. massive, IgE-mediated histamine release from mast cells in the dermis.
  2. a direct toxic effect of the morphine preservative on cutaneous nerve endings.
  3. systemic absorption of morphine leading to a generalized urticarial reaction.
  4. opioid receptor activation in the dorsal horn and trigeminal nucleus, which is not mediated by histamine. (correct answer)
Explanation: When you encounter questions about opioid-induced pruritus, especially after neuraxial administration, focus on the unique mechanism that distinguishes this from typical allergic reactions. Intrathecal morphine-induced itching occurs through direct activation of opioid receptors in the central nervous system, particularly in the dorsal horn of the spinal cord and trigeminal nucleus. This creates a localized pruritogenic effect that's completely independent of histamine release. The facial and truncal distribution is characteristic because these areas have dense innervation from regions where opioid receptors are highly concentrated. Importantly, this reaction doesn't respond to antihistamines, which is a key clinical clue that histamine isn't involved. Option A is incorrect because true IgE-mediated reactions would cause systemic symptoms beyond localized itching, and morphine rarely causes genuine allergic reactions. Option B misidentifies preservatives as the culprit – while preservatives can cause reactions, the pattern described is classic for opioid receptor-mediated pruritus. Option C suggests systemic absorption, but intrathecal morphine produces minimal systemic levels, and the localized pattern contradicts a generalized urticarial reaction. Remember this key distinction: opioid-induced pruritus from neuraxial administration is a pharmacological effect, not an allergic reaction. Look for the combination of localized itching (especially facial/truncal), recent neuraxial opioid administration, and lack of other allergic symptoms. This helps you distinguish between true allergic reactions (which need immediate intervention) and expected pharmacological effects (which are manageable but different mechanistically).

Question 10

A 72-year-old female with severe COPD and an estimated glomerular filtration rate (eGFR) of 20 mL/min/1.73m² requires parenteral opioid analgesia for a hip fracture. Which of the following opioids, when used repeatedly, poses the greatest risk of neurotoxicity and prolonged respiratory depression in this specific patient?

  1. Fentanyl, due to its high lipid solubility and redistribution into fat tissue.
  2. Hydromorphone, because its primary metabolite accumulates in renal failure.
  3. Morphine, due to the accumulation of its active metabolite, morphine-6-glucuronide. (correct answer)
  4. Buprenorphine, because of its ceiling effect on analgesia which necessitates higher doses.
Explanation: Morphine is metabolized in the liver to morphine-6-glucuronide (M6G) and morphine-3-glucuronide (M3G). M6G is a potent analgesic and respiratory depressant, while M3G can be neuroexcitatory. Both metabolites are cleared by the kidneys. In a patient with severe renal impairment (eGFR < 30), M6G and M3G can accumulate to toxic levels, causing prolonged sedation, respiratory depression, and myoclonus. Fentanyl and hydromorphone are considered safer choices in severe renal insufficiency as their metabolites are inactive or less clinically significant.

Question 11

A patient on chronic opioid therapy is treated for severe constipation with methylnaltrexone. The drug effectively relieves the constipation without reversing the centrally-mediated analgesia. This selective peripheral action is attributable to which property of the methylnaltrexone molecule?

  1. It has high selectivity for mu-receptors located only in the myenteric plexus.
  2. It is a quaternary amine with a positive charge, limiting its ability to cross the blood-brain barrier. (correct answer)
  3. It is rapidly metabolized by plasma esterases, preventing it from reaching the central nervous system.
  4. It functions as an agonist in the CNS but an antagonist in the gastrointestinal tract.
Explanation: Methylnaltrexone is a peripherally acting mu-opioid receptor antagonist (PAMORA). It is a derivative of naltrexone that has a quaternary amine group. This group carries a permanent positive charge, making the molecule highly polar and hydrophilic. This property severely restricts its ability to cross the lipophilic blood-brain barrier, so it antagonizes mu-receptors in the periphery (e.g., in the gut, relieving constipation) without affecting the desired analgesic effects in the CNS.

Question 12

A patient presents to the emergency department with CNS depression, respiratory rate of 8 breaths/min, and heart rate of 50 bpm. Physical examination reveals mydriasis (dilated pupils). Naloxone administration results in no clinical improvement. Which co-ingested agent, along with an opioid, would best explain this presentation?

  1. Clonidine (correct answer)
  2. Diazepam
  3. Cocaine
  4. Zolpidem
Explanation: This presentation suggests a mixed overdose with clonidine and an opioid. Clonidine (alpha-2 agonist) causes CNS depression, bradycardia, and respiratory depression similar to opioids, but can cause mydriasis rather than miosis. Critically, clonidine toxicity does not respond to naloxone reversal. The lack of response to naloxone in a patient with apparent opioid-like symptoms should prompt consideration of co-ingestion with a non-opioid CNS depressant like clonidine.

Question 13

A 45-year-old male with chronic back pain managed with high-dose, extended-release oxycodone is transitioned to buprenorphine/naloxone for opioid use disorder. The first dose is administered 8 hours after his last oxycodone dose. Two hours later, he develops severe anxiety, yawning, lacrimation, and intense musculoskeletal pain. Which pharmacological principle best explains this patient's acute deterioration?

  1. Buprenorphine's high affinity for and partial agonism at mu-opioid receptors displaced the full agonist, leading to a net decrease in receptor stimulation. (correct answer)
  2. Naloxone, present in the sublingual formulation, was absorbed systemically and acted as a competitive antagonist, precipitating withdrawal.
  3. The patient developed a rapid allergic reaction to buprenorphine, manifesting as a pseudo-withdrawal syndrome.
  4. The short time interval since the last oxycodone dose resulted in a synergistic effect, causing profound CNS excitation and hyperalgesia.
Explanation: This scenario describes precipitated withdrawal. Buprenorphine is a partial mu-opioid agonist with very high affinity for the receptor. When given to a patient who is physically dependent on a full agonist like oxycodone, buprenorphine competitively displaces oxycodone from the mu-receptors. Because buprenorphine has lower intrinsic activity (it's a partial agonist), this displacement results in a rapid and significant reduction in the overall level of receptor stimulation, precipitating a withdrawal syndrome.

Question 14

A 72-year-old female with severe COPD and an estimated glomerular filtration rate (eGFR) of 20 mL/min/1.73m² requires parenteral opioid analgesia for a hip fracture. Which of the following opioids, when used repeatedly, poses the greatest risk of neurotoxicity and prolonged respiratory depression in this specific patient?

  1. Fentanyl, due to its high lipid solubility and redistribution into fat tissue.
  2. Hydromorphone, because its primary metabolite accumulates in renal failure.
  3. Morphine, due to the accumulation of its active metabolite, morphine-6-glucuronide. (correct answer)
  4. Buprenorphine, because of its ceiling effect on analgesia which necessitates higher doses.
Explanation: Morphine is metabolized in the liver to morphine-6-glucuronide (M6G) and morphine-3-glucuronide (M3G). M6G is a potent analgesic and respiratory depressant, while M3G can be neuroexcitatory. Both metabolites are cleared by the kidneys. In a patient with severe renal impairment (eGFR < 30), M6G and M3G can accumulate to toxic levels, causing prolonged sedation, respiratory depression, and myoclonus. Fentanyl and hydromorphone are considered safer choices in severe renal insufficiency as their metabolites are inactive or less clinically significant.

Question 15

A patient is administered an opioid that produces significant spinal analgesia, miosis, and sedation, but is also associated with a high incidence of dysphoria, hallucinations, and psychotomimetic effects. This distinct profile of effects is most characteristic of a drug that is a selective agonist for which receptor?

  1. Mu (μ) opioid receptor
  2. Kappa (κ) opioid receptor (correct answer)
  3. Delta (δ) opioid receptor
  4. Nociceptin/orphanin FQ (NOP) receptor
Explanation: Activation of kappa (κ) opioid receptors is associated with spinal analgesia, miosis, and sedation. However, unlike mu-receptor agonists which typically cause euphoria, kappa agonists are known for producing adverse psychotomimetic effects, including dysphoria, depersonalization, and hallucinations. These effects limit their clinical utility. Mu agonism is associated with euphoria and profound respiratory depression, while delta agonism is primarily involved in analgesia and mood.

Question 16

A patient receiving an equianalgesic continuous infusion of fentanyl develops muscle rigidity, particularly in the chest wall, making ventilation difficult. This adverse effect, known as 'rigid chest syndrome', is most associated with which of the following?

  1. High-dose, rapid intravenous administration of a highly potent, lipophilic opioid. (correct answer)
  2. Accumulation of a neuroexcitatory metabolite unique to fentanyl.
  3. A paradoxical withdrawal reaction occurring during continuous infusion.
  4. Selective activation of kappa-receptors in the intercostal muscles.
Explanation: Opioid-induced muscle rigidity, including chest wall rigidity, is a known but uncommon complication. It is most strongly associated with the high-dose, rapid IV administration of potent, lipid-soluble opioids like fentanyl and its derivatives (sufentanil, remifentanil). The mechanism is thought to involve central mu-receptor effects on dopaminergic and GABAergic pathways that regulate muscle tone. It is not due to a metabolite or kappa-receptor activation.

Question 17

A patient requires analgesia for moderate pain. The selected agent is a weak mu-opioid receptor agonist that also significantly inhibits the reuptake of both norepinephrine and serotonin. Which drug matches this pharmacological profile?

  1. Tapentadol
  2. Tramadol (correct answer)
  3. Methadone
  4. Oxycodone
Explanation: Tramadol is an atypical analgesic with a dual mechanism of action. It is a weak agonist at the mu-opioid receptor, and its primary metabolite, O-desmethyltramadol, is a more potent mu-agonist. Additionally, tramadol and its metabolite inhibit the reuptake of both norepinephrine and serotonin, which contributes to analgesia via descending inhibitory pain pathways. Tapentadol is also a dual-mechanism agent, but it is a moderate mu-agonist and primarily a norepinephrine reuptake inhibitor with little effect on serotonin.

Question 18

A patient on long-term, high-dose opioid therapy reports that their baseline pain has worsened and has spread to areas not previously affected. They also describe an increased sensitivity to normally non-painful stimuli. This clinical picture is most consistent with the development of...

  1. pharmacokinetic tolerance, requiring dose escalation.
  2. opioid-induced hyperalgesia. (correct answer)
  3. a factitious disorder motivated by drug-seeking behavior.
  4. severe, untreated opioid-induced constipation.
Explanation: Opioid-induced hyperalgesia (OIH) is a paradoxical phenomenon where chronic opioid use leads to a pro-nociceptive state, causing an increase in pain sensitivity. It is distinct from tolerance, which is a decreased effect from the same dose. OIH involves neuroplastic changes in the peripheral and central nervous systems, such as activation of NMDA receptors and enhanced descending pain facilitation pathways. Clinically, it presents as worsening pain, pain spreading, and allodynia, despite escalating opioid doses.

Question 19

A patient presents to the emergency department with CNS depression, respiratory rate of 8 breaths/min, and heart rate of 50 bpm. Physical examination reveals mydriasis (dilated pupils). Naloxone administration results in no clinical improvement. Which co-ingested agent, along with an opioid, would best explain this presentation?

  1. Clonidine (correct answer)
  2. Diazepam
  3. Cocaine
  4. Zolpidem
Explanation: This presentation suggests a mixed overdose with clonidine and an opioid. Clonidine (alpha-2 agonist) causes CNS depression, bradycardia, and respiratory depression similar to opioids, but can cause mydriasis rather than miosis. Critically, clonidine toxicity does not respond to naloxone reversal. The lack of response to naloxone in a patient with apparent opioid-like symptoms should prompt consideration of co-ingestion with a non-opioid CNS depressant like clonidine.

Question 20

A patient receiving long-term methadone therapy for opioid use disorder is diagnosed with tuberculosis and started on a standard multi-drug regimen that includes rifampin. Within ten days, the patient reports symptoms of opioid withdrawal, including myalgia and intense cravings. This clinical presentation is best explained by rifampin's effect as a potent...

  1. inducer of cytochrome P450 3A4 (CYP3A4), accelerating methadone metabolism. (correct answer)
  2. inhibitor of cytochrome P450 2D6 (CYP2D6), shunting methadone to inactive pathways.
  3. competitive antagonist at the mu-opioid receptor, blocking methadone's effects.
  4. inducer of P-glycoprotein in the blood-brain barrier, reducing methadone's CNS penetration.
Explanation: Methadone is primarily metabolized by CYP3A4 and CYP2B6. Rifampin is a powerful inducer of multiple CYP enzymes, most notably CYP3A4. By inducing these enzymes, rifampin significantly increases the metabolic clearance of methadone, leading to lower plasma concentrations and the onset of withdrawal symptoms in a patient on a stable maintenance dose. This is a classic and clinically significant drug-drug interaction.