Pharmacology Quiz: Naloxone And Opioid Overdose
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Naloxone And Opioid OverdoseQuestion 1 of 20

A 45-year-old patient in a methadone maintenance program is brought to the hospital for altered mental status. The patient is lethargic with a respiratory rate of 8 breaths/minute. An initial 0.4 mg IV dose of naloxone improves the respiratory rate to 14 breaths/minute and the patient becomes more alert. An hour later, the patient remains stable.

Given the opioid involved, what is the most crucial element of this patient's subsequent management plan?

Discharge with a prescription for a take-home naloxone kit after a 2-hour observation period.
Administration of activated charcoal to prevent further methadone absorption.
Initiation of a continuous naloxone infusion or admission for prolonged observation.
Immediate consultation for switching from methadone to buprenorphine therapy.
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Pharmacology Quiz: Naloxone And Opioid Overdose

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

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

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Question 1

A 45-year-old patient in a methadone maintenance program is brought to the hospital for altered mental status. The patient is lethargic with a respiratory rate of 8 breaths/minute. An initial 0.4 mg IV dose of naloxone improves the respiratory rate to 14 breaths/minute and the patient becomes more alert. An hour later, the patient remains stable.

Given the opioid involved, what is the most crucial element of this patient's subsequent management plan?

  1. Discharge with a prescription for a take-home naloxone kit after a 2-hour observation period.
  2. Administration of activated charcoal to prevent further methadone absorption.
  3. Initiation of a continuous naloxone infusion or admission for prolonged observation. (correct answer)
  4. Immediate consultation for switching from methadone to buprenorphine therapy.
Explanation: The correct answer is C. Methadone is a long-acting opioid with a half-life that can exceed 24 hours. The effects of a single bolus of naloxone (half-life ~60-90 minutes) will wear off long before the methadone is eliminated. Therefore, the patient is at extremely high risk for recurrent respiratory depression and requires either prolonged observation (at least 24 hours) or a continuous naloxone infusion to counteract the persistent effects of methadone. A is incorrect because discharging the patient would be unsafe due to the high likelihood of re-sedation once the initial naloxone dose wears off. B is incorrect because activated charcoal is only effective shortly after ingestion and this patient's presentation suggests the methadone was already systemically absorbed. D is incorrect because altering the patient's long-term opioid use disorder treatment is not the priority during an acute overdose.

Question 2

A 62-year-old male with metastatic lung cancer is on a stable regimen of long-acting morphine, 100 mg twice daily, for severe pain. His caregiver accidentally administers an extra dose. The patient becomes difficult to arouse with a respiratory rate of 6 breaths/minute. His pain is currently well-controlled.

What is the most appropriate initial strategy for administering naloxone in this patient?

  1. Administer the standard 2 mg intravenous bolus to ensure rapid and complete reversal.
  2. Withhold naloxone and provide bag-valve-mask ventilation until the opioid is metabolized.
  3. Administer small, dilute intravenous doses of naloxone (e.g., 0.04-0.1 mg) and titrate to an adequate respiratory rate. (correct answer)
  4. Administer 4 mg of intranasal naloxone as it is less likely to precipitate severe withdrawal.
Explanation: The correct answer is C. This patient is physically dependent on opioids for analgesia. The goal of naloxone administration is to restore adequate ventilation without fully reversing analgesia or precipitating a severe, painful withdrawal syndrome. This is best achieved by administering small, incremental doses of naloxone and titrating carefully to the desired effect (a respiratory rate >12/min), not to full consciousness. A is incorrect because a large bolus would likely cause abrupt, severe withdrawal, leading to intense pain, agitation, and autonomic instability. B is incorrect because withholding naloxone in the face of significant respiratory depression is inappropriate and potentially dangerous. D is incorrect because the 4 mg intranasal dose is a large dose equivalent to or greater than the 2 mg IV bolus and would also likely precipitate severe withdrawal. The route does not change this risk.

Question 3

A public health program aims to distribute naloxone kits to laypersons for use in community settings. The program prioritizes a formulation that has a rapid onset of action, is simple to use for untrained individuals, and minimizes the risk of accidental exposure or injury. Which formulation and rationale best meets these criteria?

  1. Intravenous (IV) naloxone, because it provides the most rapid and reliable onset of action.
  2. Intramuscular (IM) auto-injector, because it provides higher bioavailability than intranasal formulations.
  3. Subcutaneous (SQ) injection, because it provides a longer duration of action to prevent re-sedation.
  4. Pre-filled intranasal (IN) spray device, because it has a rapid onset and is needle-free, making it easy and safe for laypersons. (correct answer)
Explanation: The correct answer is D. Pre-filled intranasal naloxone devices are designed for layperson use. They require no assembly, have a very low risk of injury (no needles), and provide rapid absorption through the nasal mucosa, with an onset of action comparable to IM injection in clinical studies. This combination of speed, safety, and ease of use makes it ideal for community distribution. A is incorrect because laypersons cannot administer IV medications. B is incorrect. While IM auto-injectors are also effective and used in the community, the intranasal device is generally considered easier and safer for untrained individuals as it eliminates needlestick risk. The slightly higher bioavailability of IM is not a decisive advantage over the safety and simplicity of IN. C is incorrect because rapid onset, not prolonged duration, is the priority for an initial reversal agent. Also, SQ administration can have delayed and variable absorption.

Question 4

A 60 kg patient with a suspected overdose from an illicit fentanyl analogue requires repeated IV boluses of naloxone. Over a period of 20 minutes, a total of 1.6 mg of naloxone was required to maintain a respiratory rate above 12 breaths/minute. A decision is made to start a continuous intravenous infusion of naloxone.

Based on a common clinical guideline for calculating the initial rate, which of the following is the most appropriate starting rate for the naloxone infusion?

  1. 1.6 mg/hour
  2. 2.4 mg/hour
  3. 3.2 mg/hour (correct answer)
  4. 4.8 mg/hour
Explanation: The correct answer is C. This is a multi-step calculation. First, calculate the total amount of naloxone required per hour to keep the patient stable. The patient needed 1.6 mg in 20 minutes. To find the hourly rate, multiply by 3 (since there are three 20-minute periods in an hour): 1.6 mg * 3 = 4.8 mg/hour. A common clinical rule of thumb is to start the continuous infusion at two-thirds (2/3) of the total hourly bolus requirement. (2/3) * 4.8 mg/hour = 3.2 mg/hour. This strategy provides a steady state of naloxone while minimizing the risk of overshoot and severe withdrawal. A is incorrect as it only considers the total bolus dose, not the timeframe. B is a miscalculation. D is incorrect because it represents the full hourly requirement, which may be excessive and precipitate withdrawal. Starting at two-thirds is a more cautious approach.

Question 5

A 28-year-old patient who is 34 weeks pregnant presents to the emergency department with profound respiratory depression (4 breaths/minute) and miosis after a suspected heroin overdose. Fetal heart monitoring shows recurrent late decelerations. What is the most appropriate course of action?

  1. Administer titrated doses of naloxone to the mother to restore ventilation, and prepare to manage neonatal withdrawal after delivery. (correct answer)
  2. Perform an emergency Cesarean section before administering naloxone to the mother.
  3. Withhold naloxone due to the risk of precipitating labor and worsening fetal distress.
  4. Focus solely on maternal ventilation with a bag-valve-mask to avoid exposing the fetus to any medication.
Explanation: When you encounter opioid overdose in pregnancy, you're balancing two critical priorities: maternal life-threatening respiratory depression and potential fetal effects. The key principle is that maternal survival takes precedence, as fetal survival depends entirely on maternal well-being. Why A is correct: Naloxone is the life-saving antidote for opioid overdose, and titrated dosing allows you to restore adequate ventilation while minimizing withdrawal severity. While naloxone crosses the placenta and can precipitate neonatal withdrawal, this is manageable with proper neonatal care. The fetal heart rate abnormalities are likely secondary to maternal hypoxemia, so improving maternal oxygenation will benefit both mother and fetus. Why the other answers are wrong:
  • B suggests emergency cesarean before naloxone, but this exposes both patients to surgical risks when the underlying problem (maternal hypoxemia) remains untreated. The fetal distress will likely resolve with maternal stabilization.
  • C withholds the life-saving antidote due to withdrawal concerns, prioritizing potential fetal complications over certain maternal death from respiratory failure.
  • D attempts supportive care alone, but bag-valve-mask ventilation is inadequate for ongoing opioid toxicity and doesn't address the root cause.
Study tip: In pregnancy emergencies, remember "mother first" - you cannot save the fetus if the mother dies. Naloxone-induced neonatal withdrawal is uncomfortable but treatable; maternal respiratory arrest is fatal. Always treat life-threatening maternal conditions promptly, even when medications cross the placenta.

Question 6

An unconscious patient is brought to the emergency department. The differential diagnosis includes opioid overdose, severe hypoglycemia, large ischemic stroke, and benzodiazepine overdose.

Which of the following physical examination findings is most specific for an opioid toxidrome?

  1. Bradycardia
  2. Hypotension
  3. Respiratory depression
  4. Symmetric, pinpoint pupils (correct answer)
Explanation: The correct answer is D. While respiratory depression, bradycardia, and hypotension can be seen in opioid overdose, they are not specific and can be caused by other conditions like benzodiazepine overdose or stroke. However, symmetric, miotic (pinpoint) pupils are a classic and highly specific sign of an opioid toxidrome, resulting from opioid effects on the Edinger-Westphal nucleus. A, B, and C are incorrect because they are non-specific findings. Respiratory depression is a key feature but can also be prominent in sedative-hypnotic overdose. Bradycardia and hypotension can occur in many forms of shock and CNS depression.

Question 7

A 25-year-old male is treated for a heroin overdose with intravenous naloxone. He awakens but shortly after develops severe dyspnea, tachypnea, and hypoxia. A chest radiograph reveals diffuse bilateral opacities consistent with pulmonary edema. There are no signs of fluid overload or cardiac dysfunction.

This patient's acute respiratory distress is most likely a result of which naloxone-related phenomenon?

  1. Non-cardiogenic pulmonary edema related to a catecholamine surge. (correct answer)
  2. Aspiration pneumonitis that occurred during the overdose period.
  3. Anaphylaxis to a preservative in the naloxone formulation.
  4. Acute respiratory distress syndrome (ARDS) from systemic inflammation.
Explanation: When you encounter naloxone reversal cases, think about the physiological rebound effects that occur when opioid receptors are suddenly blocked after prolonged activation. Naloxone rapidly displaces opioids from receptors, creating an abrupt reversal of opioid effects. This sudden blockade triggers a massive sympathetic nervous system response - essentially a catecholamine surge with high levels of epinephrine and norepinephrine. This sympathetic storm can cause acute pulmonary capillary leak, leading to non-cardiogenic pulmonary edema. The timing here is key: the patient develops respiratory distress shortly after naloxone administration, and the chest X-ray shows bilateral opacities without cardiac dysfunction. This pattern strongly suggests catecholamine-induced pulmonary edema, making choice A correct. Choice B (aspiration pneumonitis) would have occurred during the unconscious overdose period, not acutely after naloxone reversal, and typically shows different radiographic patterns. Choice C (anaphylaxis) would present with additional systemic signs like hypotension, urticaria, or bronchospasm, not isolated pulmonary edema. Choice D (ARDS) develops over hours to days from systemic inflammation and wouldn't occur this acutely after naloxone administration. Remember this pattern: naloxone-induced pulmonary edema is a well-recognized complication that occurs within minutes of reversal due to sympathetic overstimulation. Always consider this when patients develop acute respiratory distress immediately following opioid reversal, especially when cardiac function appears normal.

Question 8

A patient is being treated for a severe methadone overdose with a continuous naloxone infusion. After 18 hours, the patient is awake, alert, and has a stable respiratory rate of 16 breaths/minute. The naloxone infusion is currently running at 2 mg/hour.

What is the most appropriate next step in managing the naloxone infusion?

  1. Wean the infusion rate by 50% (to 1 mg/hour) and continue to monitor for re-sedation. (correct answer)
  2. Increase the infusion rate to 4 mg/hour for 2 hours to clear any residual methadone.
  3. Stop the infusion abruptly and discharge the patient if they remain stable for 1 hour.
  4. Convert the infusion to an equivalent dose given as an hourly intramuscular bolus.
Explanation: When managing opioid overdoses with naloxone, you must understand the pharmacokinetic mismatch between the antidote and the toxin. Methadone has an exceptionally long half-life (15-60 hours) compared to naloxone (30-90 minutes), creating a high risk of re-sedation when naloxone levels drop below therapeutic thresholds. After 18 hours of continuous infusion with good clinical response, the appropriate strategy is gradual weaning while maintaining vigilant monitoring. Answer A correctly advocates for a 50% reduction (from 2 mg/hour to 1 mg/hour) with continued observation for re-sedation. This approach maintains adequate opioid receptor blockade while testing whether the methadone concentration has decreased sufficiently. Answer B is dangerous because increasing the naloxone dose is unnecessary when the patient is clinically stable and won't "clear" residual methadone—naloxone is a competitive antagonist, not a drug that enhances elimination. Answer C represents a critical error: abrupt discontinuation with only one hour of observation ignores methadone's prolonged duration of action and virtually guarantees re-sedation once naloxone clears. Answer D offers no clinical advantage over intravenous administration and creates unnecessary patient discomfort and nursing burden. The key principle here is that naloxone weaning must be gradual and deliberate, with each reduction step followed by several hours of monitoring. Remember: in methadone overdoses, patients can re-sedate up to 24-48 hours after apparent recovery, making conservative weaning protocols essential for patient safety.

Question 9

An 84-year-old resident of a long-term care facility is prescribed oxycodone 5 mg every 6 hours as needed for pain. After receiving a dose, she is found to have a respiratory rate of 8 breaths/minute. She is given a small dose of naloxone and her respiratory rate improves, but she remains unusually groggy and confused for the next 8 hours.

Which age-related physiological change is the most likely contributor to this patient's prolonged sedation after opioid administration?

  1. Decreased number of mu-opioid receptors in the central nervous system.
  2. Reduced hepatic metabolism and renal excretion of the opioid and its metabolites. (correct answer)
  3. Increased production of endogenous endorphins that potentiate the opioid effect.
  4. A paradoxical excitatory reaction to naloxone commonly observed in the elderly.
Explanation: The correct answer is B. Elderly patients often have reduced hepatic blood flow and decreased glomerular filtration rate. This leads to slower metabolism (Phase I oxidation) and clearance of drugs like oxycodone and their active metabolites. The result is a prolonged half-life and an increased area under the curve (AUC), meaning the drug stays in their system longer and at higher effective concentrations, leading to prolonged sedation and increased risk of toxicity. A is incorrect. While receptor sensitivity may change with age, it is the pharmacokinetic changes that have the most pronounced effect on duration of action. C is incorrect. There is no evidence for increased endorphin production potentiating opioids in the elderly. D is incorrect. Paradoxical reactions to naloxone are not a recognized, common phenomenon in this population; the prolonged sedation is due to the opioid.

Question 10

Paramedics respond to a person found in cardiac arrest at home, surrounded by drug paraphernalia. They perform CPR and administer a total of 12 mg of intravenous naloxone over 15 minutes. Despite these efforts and advanced cardiac life support, the patient never achieves return of spontaneous circulation.

What is the most plausible explanation for the complete lack of response to high-dose naloxone in this scenario?

  1. The patient overdosed on a naloxone-resistant synthetic opioid.
  2. The patient suffered irreversible anoxic brain injury and circulatory collapse prior to naloxone administration. (correct answer)
  3. The naloxone was administered too rapidly, causing a paradoxical cardiovascular collapse.
  4. The paramedics likely used an expired batch of naloxone with no pharmacological activity.
Explanation: The correct answer is B. Naloxone can only reverse opioid-induced respiratory depression; it cannot reverse the downstream consequences of prolonged, severe hypoxia, such as irreversible anoxic brain injury and cardiovascular collapse leading to cardiac arrest. Once the patient has been in arrest for a significant period, naloxone will be ineffective because the vital organs have already failed. This is a far more common reason for failure to respond in the setting of cardiac arrest than the presence of a truly 'naloxone-resistant' opioid. A is incorrect. While some potent synthetics like carfentanil require very high doses of naloxone, they are not completely 'resistant'. A 12 mg dose would be expected to produce at least some effect if the patient were still viable. C is incorrect. This is not a known pharmacological effect of naloxone. D is highly unlikely and less plausible than the patient having irreversible injury from being down for too long.

Question 11

A patient with opioid-induced respiratory arrest is given intravenous naloxone. Within one minute, the patient's spontaneous respirations are restored. This rapid reversal of opioid effects is a direct result of which pharmacological principle?

  1. Naloxone acts as a non-competitive antagonist, permanently inactivating mu-opioid receptors.
  2. Naloxone acts as an inverse agonist, producing effects opposite to those of opioids at the receptor site.
  3. Naloxone acts as a partial agonist, providing a ceiling effect on respiratory depression.
  4. Naloxone acts as a competitive antagonist, displacing the opioid agonist from the mu-opioid receptor. (correct answer)
Explanation: The correct answer is D. Naloxone is a pure, high-affinity, competitive antagonist at the mu-opioid receptor. It has a higher affinity for the receptor than most opioid agonists (like morphine or heroin). When administered, it rapidly displaces the agonist from the receptor binding sites, thereby reversing the agonist's effects, including respiratory depression. A is incorrect. Non-competitive antagonists bind to an allosteric site or bind irreversibly, which is not naloxone's mechanism. Its effects are surmountable with higher agonist concentrations. B is incorrect. While inverse agonists exist, naloxone is considered a neutral antagonist, meaning it has no intrinsic activity of its own. C is incorrect. Buprenorphine is an example of a partial agonist. Naloxone is a pure antagonist.

Question 12

A 35-year-old man with opioid use disorder is given a 2 mg IV bolus of naloxone for an overdose. He awakens immediately but is extremely agitated, diaphoretic, and vomiting. His heart rate is 150/min and blood pressure is 200/120 mmHg.

Which of the following is the most appropriate pharmacologic intervention to manage this patient's severe precipitated withdrawal syndrome?

  1. Administer a small dose of morphine to alleviate the withdrawal symptoms.
  2. Administer a beta-blocker such as propranolol to control the hypertension and tachycardia.
  3. Administer an intravenous benzodiazepine, such as diazepam, for sedation and agitation. (correct answer)
  4. Administer an additional dose of naloxone to ensure all opioid has been cleared from receptors.
Explanation: The correct answer is C. The patient is experiencing severe opioid withdrawal precipitated by naloxone. The primary goal is supportive care to manage the symptoms. Benzodiazepines are effective for treating the agitation, anxiety, and muscle cramps associated with withdrawal. Adjunctive agents like clonidine (an alpha-2 agonist) can also be used for autonomic instability, but benzodiazepines are a mainstay for agitation. A is incorrect. Administering an opioid in this acute setting is dangerous as it can be difficult to titrate and may lead to re-sedation and respiratory depression. B is incorrect. Using a beta-blocker is not recommended as first-line therapy because unopposed alpha-adrenergic stimulation could worsen hypertension. D is incorrect. Administering more naloxone would only worsen the withdrawal syndrome.

Question 13

An 18-month-old, 12 kg child is brought to the emergency department after being found playing with a grandparent's used fentanyl patch. The child is lethargic with a respiratory rate of 10 breaths/minute. The patch is removed from the child's hand.

In addition to initial resuscitation and naloxone administration, which management principle is most critical for this child's safety?

  1. Administering ipecac syrup to induce emesis and remove any ingested fentanyl.
  2. Prolonged inpatient observation for at least 24 hours, even if initially asymptomatic. (correct answer)
  3. Avoiding naloxone due to the high risk of paradoxical seizures in toddlers.
  4. Obtaining a blood toxicology screen before administering any naloxone.
Explanation: The correct answer is B. Transdermal fentanyl patches create a depot of the drug in the skin. Even after the patch is removed, fentanyl will continue to be absorbed systemically from this depot for many hours. This puts the child at high risk for delayed or recurrent respiratory depression. Therefore, prolonged observation in a monitored setting is essential, regardless of their initial response to naloxone. A is incorrect. Ipecac is no longer recommended, and the primary route of exposure is transdermal/transmucosal, not ingestion. C is incorrect. Naloxone is the life-saving antidote for opioid overdose in all age groups, including toddlers. The risk of untreated respiratory depression far outweighs any risks of the medication. D is incorrect. Treatment of a life-threatening overdose should never be delayed while waiting for laboratory confirmation.

Question 14

A 22-year-old is brought to the ED after ingesting an unknown substance at a concert. The patient is diaphoretic, agitated, and has a heart rate of 130 bpm, BP of 160/100 mmHg, and pupils are 6 mm. However, the respiratory rate is 7 breaths/minute with an SpO2 of 89%. Which clinical finding is the strongest indication for the immediate administration of naloxone?

  1. Tachycardia
  2. Hypertension
  3. Mydriasis (pupil size 6 mm)
  4. Bradypnea (respiratory rate 7/min) (correct answer)
Explanation: The correct answer is D. This patient presents with a mixed toxidrome, likely a sympathomimetic (causing agitation, tachycardia, hypertension, mydriasis) and an opioid. The life-threatening feature of opioid overdose is respiratory depression (bradypnea). Despite the other signs pointing towards a stimulant, the profoundly low respiratory rate is the classic and most urgent sign of opioid toxicity that must be treated with naloxone. The other vital signs are inconsistent with a pure opioid overdose but do not preclude a dangerous co-ingestion. A, B, and C are all signs of sympathomimetic or anticholinergic toxicity and are opposite to what would be expected in a pure opioid overdose. They are distractors that might confuse a test-taker who is looking for the classic opioid triad.

Question 15

A college student is brought to the emergency department after being found unconscious. Empty blister packs of alprazolam and oxycodone are found nearby. The patient has a respiratory rate of 6 breaths/minute. After administration of 2 mg of intravenous naloxone, the respiratory rate improves to 12 breaths/minute, but the patient remains comatose with a Glasgow Coma Scale (GCS) of 5.

What is the most likely reason for the patient's persistent coma despite an improved respiratory rate?

  1. The naloxone dose was insufficient to overcome the high affinity of oxycodone for mu-receptors.
  2. The patient has suffered an irreversible anoxic brain injury from prolonged hypoxia.
  3. Co-ingestion of alprazolam is causing profound sedation via GABA-A receptor agonism. (correct answer)
  4. Naloxone has a paradoxical effect in the setting of polysubstance overdose, worsening sedation.
Explanation: The correct answer is C. Naloxone is a specific antagonist for opioid receptors and will not reverse the sedative effects of other drug classes. Alprazolam is a benzodiazepine, which causes sedation by potentiating the effect of the inhibitory neurotransmitter GABA. The improvement in respiratory rate indicates successful reversal of the opioid component of the overdose, but the persistent coma is due to the co-ingested benzodiazepine. This is a classic presentation of a mixed opioid-benzodiazepine overdose. A is incorrect because the significant improvement in respiratory rate suggests the naloxone dose was effective against the opioid. B, while possible in any overdose, is less likely given the immediate improvement in respiratory function. The more direct explanation is the effect of the other ingested drug. D is incorrect; naloxone does not have a paradoxical sedative effect.

Question 16

A 28-year-old male with a history of intravenous heroin use is brought to the emergency department after being found unresponsive. On arrival, his respiratory rate is 4 breaths/minute and pupils are pinpoint. He is given 0.8 mg of naloxone intravenously. Within two minutes, his respiratory rate increases to 16 breaths/minute and he becomes responsive. Forty-five minutes later, a nurse finds him somnolent again with a respiratory rate of 6 breaths/minute.

Which of the following best explains the patient's recurrent respiratory depression?

  1. The patient has developed acute tachyphylaxis to the effects of naloxone.
  2. The duration of action of naloxone is shorter than that of the opioid the patient used. (correct answer)
  3. The initial dose of naloxone was insufficient to fully reverse the opioid's effects.
  4. The opioid has been redistributed from peripheral fatty tissues back into the central nervous system.
Explanation: The correct answer is B. Naloxone has a relatively short half-life (30-90 minutes), while many opioids, especially illicit fentanyl analogues often mixed with heroin, have a longer duration of action. After the naloxone is metabolized, the opioid can re-engage the mu-receptors, causing recurrent respiratory depression, also known as 're-narcanization'. This pharmacokinetic mismatch is a critical concept in overdose management. A is incorrect because tachyphylaxis (rapidly diminishing response to successive doses of a drug) is not a characteristic feature of naloxone, which acts as a pure competitive antagonist. C is incorrect because the patient initially had a complete response, indicating the dose was sufficient to temporarily reverse the effects. The issue is duration, not initial potency. D is incorrect. While lipid-soluble opioids like fentanyl do redistribute, the primary reason for the patient's decline is the clearance of naloxone, not a sudden massive redistribution of the opioid.

Question 17

A 45-year-old patient in a methadone maintenance program is brought to the hospital for altered mental status. The patient is lethargic with a respiratory rate of 8 breaths/minute. An initial 0.4 mg IV dose of naloxone improves the respiratory rate to 14 breaths/minute and the patient becomes more alert. An hour later, the patient remains stable.

Given the opioid involved, what is the most crucial element of this patient's subsequent management plan?

  1. Discharge with a prescription for a take-home naloxone kit after a 2-hour observation period.
  2. Administration of activated charcoal to prevent further methadone absorption.
  3. Initiation of a continuous naloxone infusion or admission for prolonged observation. (correct answer)
  4. Immediate consultation for switching from methadone to buprenorphine therapy.
Explanation: The correct answer is C. Methadone is a long-acting opioid with a half-life that can exceed 24 hours. The effects of a single bolus of naloxone (half-life ~60-90 minutes) will wear off long before the methadone is eliminated. Therefore, the patient is at extremely high risk for recurrent respiratory depression and requires either prolonged observation (at least 24 hours) or a continuous naloxone infusion to counteract the persistent effects of methadone. A is incorrect because discharging the patient would be unsafe due to the high likelihood of re-sedation once the initial naloxone dose wears off. B is incorrect because activated charcoal is only effective shortly after ingestion and this patient's presentation suggests the methadone was already systemically absorbed. D is incorrect because altering the patient's long-term opioid use disorder treatment is not the priority during an acute overdose.

Question 18

A college student is brought to the emergency department after being found unconscious. Empty blister packs of alprazolam and oxycodone are found nearby. The patient has a respiratory rate of 6 breaths/minute. After administration of 2 mg of intravenous naloxone, the respiratory rate improves to 12 breaths/minute, but the patient remains comatose with a Glasgow Coma Scale (GCS) of 5.

What is the most likely reason for the patient's persistent coma despite an improved respiratory rate?

  1. The naloxone dose was insufficient to overcome the high affinity of oxycodone for mu-receptors.
  2. The patient has suffered an irreversible anoxic brain injury from prolonged hypoxia.
  3. Co-ingestion of alprazolam is causing profound sedation via GABA-A receptor agonism. (correct answer)
  4. Naloxone has a paradoxical effect in the setting of polysubstance overdose, worsening sedation.
Explanation: The correct answer is C. Naloxone is a specific antagonist for opioid receptors and will not reverse the sedative effects of other drug classes. Alprazolam is a benzodiazepine, which causes sedation by potentiating the effect of the inhibitory neurotransmitter GABA. The improvement in respiratory rate indicates successful reversal of the opioid component of the overdose, but the persistent coma is due to the co-ingested benzodiazepine. This is a classic presentation of a mixed opioid-benzodiazepine overdose. A is incorrect because the significant improvement in respiratory rate suggests the naloxone dose was effective against the opioid. B, while possible in any overdose, is less likely given the immediate improvement in respiratory function. The more direct explanation is the effect of the other ingested drug. D is incorrect; naloxone does not have a paradoxical sedative effect.

Question 19

A patient with opioid-induced respiratory arrest is given intravenous naloxone. Within one minute, the patient's spontaneous respirations are restored. This rapid reversal of opioid effects is a direct result of which pharmacological principle?

  1. Naloxone acts as a non-competitive antagonist, permanently inactivating mu-opioid receptors.
  2. Naloxone acts as an inverse agonist, producing effects opposite to those of opioids at the receptor site.
  3. Naloxone acts as a partial agonist, providing a ceiling effect on respiratory depression.
  4. Naloxone acts as a competitive antagonist, displacing the opioid agonist from the mu-opioid receptor. (correct answer)
Explanation: The correct answer is D. Naloxone is a pure, high-affinity, competitive antagonist at the mu-opioid receptor. It has a higher affinity for the receptor than most opioid agonists (like morphine or heroin). When administered, it rapidly displaces the agonist from the receptor binding sites, thereby reversing the agonist's effects, including respiratory depression. A is incorrect. Non-competitive antagonists bind to an allosteric site or bind irreversibly, which is not naloxone's mechanism. Its effects are surmountable with higher agonist concentrations. B is incorrect. While inverse agonists exist, naloxone is considered a neutral antagonist, meaning it has no intrinsic activity of its own. C is incorrect. Buprenorphine is an example of a partial agonist. Naloxone is a pure antagonist.

Question 20

A 22-year-old is brought to the ED after ingesting an unknown substance at a concert. The patient is diaphoretic, agitated, and has a heart rate of 130 bpm, BP of 160/100 mmHg, and pupils are 6 mm. However, the respiratory rate is 7 breaths/minute with an SpO2 of 89%. Which clinical finding is the strongest indication for the immediate administration of naloxone?

  1. Tachycardia
  2. Hypertension
  3. Mydriasis (pupil size 6 mm)
  4. Bradypnea (respiratory rate 7/min) (correct answer)
Explanation: The correct answer is D. This patient presents with a mixed toxidrome, likely a sympathomimetic (causing agitation, tachycardia, hypertension, mydriasis) and an opioid. The life-threatening feature of opioid overdose is respiratory depression (bradypnea). Despite the other signs pointing towards a stimulant, the profoundly low respiratory rate is the classic and most urgent sign of opioid toxicity that must be treated with naloxone. The other vital signs are inconsistent with a pure opioid overdose but do not preclude a dangerous co-ingestion. A, B, and C are all signs of sympathomimetic or anticholinergic toxicity and are opposite to what would be expected in a pure opioid overdose. They are distractors that might confuse a test-taker who is looking for the classic opioid triad.