Toxidromes Practice Questions

25 multiple-choice questions on Toxidromes for paramedic and EMT students, from Chapter 28 (Toxicology). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. A 24-year-old man is agitated, hot, and diaphoretic with dilated pupils, HR 138, and BP 182/104. The most likely toxidrome is:

   1. A. Anticholinergic
   2. B. Cholinergic
   3. C. Sympathomimetic
   4. D. Sedative-hypnotic
   Show answer

   Answer: C. Sympathomimetic

   Stimulation with sweating points to sympathomimetic toxicity such as cocaine or methamphetamine. Anticholinergic patients look similar but have hot, dry, flushed skin.

2. The feature that best distinguishes sympathomimetic from anticholinergic toxicity is:

   1. A. Sweaty skin rather than dry skin
   2. B. Dilated rather than constricted pupils
   3. C. A fast rather than a slow heart rate
   4. D. Agitation rather than calm behavior
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   Answer: A. Sweaty skin rather than dry skin

   Both toxidromes cause mydriasis, tachycardia, and agitation. Anticholinergics block sweat glands, so the skin is dry, while sympathomimetics cause diaphoresis.

3. A 16-year-old who ate jimsonweed seeds is confused, flushed, and hot with dry skin, dilated pupils, and a distended bladder. This presentation is classic for:

   1. A. Cholinergic (SLUDGE) toxicity
   2. B. Anticholinergic toxicity
   3. C. Opioid toxicity
   4. D. Serotonin syndrome
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   Answer: B. Anticholinergic toxicity

   Hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter, and full as a flask describe anticholinergic poisoning. Cholinergic patients are wet, not dry.

4. A man who swallowed amitriptyline and oxycodone wakes up after naloxone and breathes well. Twenty minutes later he is agitated with HR 140 and a QRS that has widened from 100 to 150 ms. The best explanation is:

   1. A. Opioid withdrawal from naloxone
   2. B. An allergic reaction to naloxone
   3. C. Worsening tricyclic toxicity
   4. D. Recurrent opioid toxicity
   Show answer

   Answer: C. Worsening tricyclic toxicity

   Mixed overdoses are common, and treating one drug does not treat the other. The tricyclic keeps being absorbed and its sodium-channel blockade widens the QRS, which calls for sodium bicarbonate and close monitoring. Opioid withdrawal can cause agitation and tachycardia, but it does not widen the QRS. Recurrent opioid toxicity would bring back sedation and slow breathing, not agitation. Naloxone allergy is extremely rare and would cause hives, wheezing, or hypotension.

5. Which group of medications commonly causes anticholinergic toxicity?

   1. A. Diphenhydramine, TCAs, and scopolamine
   2. B. Metoprolol, diltiazem, verapamil, and digoxin
   3. C. Morphine, fentanyl, oxycodone, and methadone
   4. D. Lorazepam, diazepam, alprazolam, and clonazepam
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   Answer: A. Diphenhydramine, TCAs, and scopolamine

   Antihistamines, TCAs, antipsychotics, and belladonna plants all block muscarinic receptors. The other groups cause bradycardia, opioid, or sedative toxidromes.

6. A useful rule for withdrawal syndromes is that their signs tend to be:

   1. A. The same as the drug's own effects
   2. B. The opposite of the drug's own effects
   3. C. Limited to anxiety and poor sleep
   4. D. Seen only after many years of heavy use
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   Answer: B. The opposite of the drug's own effects

   Withdrawal reflects the body's adaptation to a drug, so stopping it produces the reverse picture: depressant (alcohol, benzodiazepine) withdrawal causes agitation, tachycardia, tremor, and seizures, and opioid withdrawal causes dilated pupils, yawning, and diarrhea instead of miosis and constipation. Withdrawal is not limited to anxiety and insomnia; alcohol and benzodiazepine withdrawal can kill. Physical dependence can develop within weeks, not only after years.

7. The mnemonic SLUDGEM describes cholinergic toxicity. The 'S' and 'L' stand for:

   1. A. Sweating and lethargy
   2. B. Seizures and lymphadenopathy
   3. C. Shivering and laryngospasm
   4. D. Salivation and lacrimation
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   Answer: D. Salivation and lacrimation

   SLUDGEM is salivation, lacrimation, urination, defecation, GI upset, emesis, and miosis. The 'killer Bs' of bradycardia, bronchorrhea, and bronchospasm cause death.

8. In cholinergic poisoning, the findings most likely to cause death are:

   1. A. Bronchorrhea and bronchospasm
   2. B. Lacrimation and profuse diarrhea
   3. C. Miosis and urination
   4. D. Salivation and vomiting
   Show answer

   Answer: A. Bronchorrhea and bronchospasm

   Airway secretions and bronchospasm drown the patient, which is why atropine is titrated to drying of the lungs. Tearing and diarrhea are unpleasant but not lethal.

9. A 30-year-old found next to a syringe has RR 4 and cyanosis, but his pupils are midsize. Which conclusion is best?

   1. A. Opioid toxicity has been ruled out
   2. B. Naloxone is now contraindicated
   3. C. A cholinergic agent is the cause
   4. D. Opioid toxicity is still possible
   Show answer

   Answer: D. Opioid toxicity is still possible

   Pinpoint pupils support an opioid overdose, but their absence does not exclude it: hypoxic brain injury, a coingested stimulant or anticholinergic, or meperidine can leave pupils normal or large. Ventilate and give naloxone as usual. Naloxone is not contraindicated by pupil size. A cholinergic poison would cause small pupils with heavy secretions, so midsize pupils do not point to it.

10. The classic triad of opioid toxicity is:

    1. A. Agitation, tachycardia, and mydriasis
    2. B. Coma, hyperthermia, and dry flushed skin
    3. C. Coma, respiratory depression, and miosis
    4. D. Seizures, bradycardia, and diaphoresis
    Show answer

    Answer: C. Coma, respiratory depression, and miosis

    Respiratory depression is the cause of death in opioid overdose. Agitation with mydriasis describes stimulants, and dry flushed skin is anticholinergic.

11. Which opioid characteristically causes normal or dilated pupils rather than miosis?

    1. A. Heroin (diacetylmorphine)
    2. B. Meperidine
    3. C. Morphine
    4. D. Fentanyl
    Show answer

    Answer: B. Meperidine

    Meperidine has anticholinergic properties and may not cause miosis, so normal pupils do not rule out opioids. Mixed ingestions and hypoxic brain injury can also dilate pupils.

12. A 50-year-old man took a large number of his wife's lorazepam tablets. He is drowsy and slurring words with RR 14, normal pupils, and stable vitals. This is most consistent with:

    1. A. Sedative-hypnotic toxicity
    2. B. Opioid toxicity
    3. C. Anticholinergic toxicity
    4. D. Cholinergic nerve agent toxicity
    Show answer

    Answer: A. Sedative-hypnotic toxicity

    Benzodiazepines alone cause CNS depression with relatively preserved breathing and normal pupils. A low respiratory rate with pinpoint pupils would point instead to an opioid.

13. Benzodiazepine overdose alone rarely causes death unless:

    1. A. The patient is younger than 40 years old
    2. B. The drug was taken on an empty stomach
    3. C. The patient has taken it for many years
    4. D. It is combined with alcohol or opioids
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    Answer: D. It is combined with alcohol or opioids

    Combining CNS depressants produces synergistic respiratory depression. Pure benzodiazepine overdoses usually cause sedation with protected breathing.

14. A patient with serotonin syndrome has a temperature of 41.5 °C (106.7 °F) and worsening muscle rigidity despite benzodiazepines. The receiving team will most likely need to:

    1. A. Give acetaminophen for fever
    2. B. Apply physical restraints
    3. C. Paralyze, intubate, and cool
    4. D. Give haloperidol to calm him
    Show answer

    Answer: C. Paralyze, intubate, and cool

    In severe serotonin syndrome the heat comes from muscle activity, not from a reset thermostat, so the definitive step is sedation, nondepolarizing paralysis, intubation, and aggressive cooling. Antipyretics such as acetaminophen do not work because the hypothalamic set point is not raised. Restraints alone make patients fight harder and generate more heat. Haloperidol is avoided: it can worsen hyperthermia and confuses the picture with neuroleptic malignant syndrome.

15. A patient with suspected neuroleptic malignant syndrome is confused, rigid, and febrile at 40.5 °C (104.9 °F). Along with airway support and cooling, prehospital care should include:

    1. A. IV haloperidol to calm him
    2. B. IV fluids and a benzodiazepine
    3. C. Acetaminophen to treat the fever
    4. D. Physostigmine for rigidity
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    Answer: B. IV fluids and a benzodiazepine

    Neuroleptic malignant syndrome is treated by stopping the dopamine blocker and giving supportive care: cooling, IV fluids for dehydration and muscle breakdown, and benzodiazepines for agitation. Giving more haloperidol adds to the dopamine blockade that caused the syndrome. Acetaminophen does little because the fever comes from rigid muscles and impaired heat regulation. Physostigmine treats anticholinergic delirium and has no role here.

16. Pinpoint pupils are expected with both opioid toxicity and:

    1. A. Cocaine or amphetamine intoxication
    2. B. Diphenhydramine overdose
    3. C. Alcohol withdrawal
    4. D. Organophosphate poisoning
    Show answer

    Answer: D. Organophosphate poisoning

    Both opioids and cholinergic agents cause miosis, so look at secretions and heart rate to separate them. Cocaine and anticholinergics dilate the pupils.

17. A teenager who swallowed a large amount of diphenhydramine is delirious, and the monitor shows a new QRS of 130 ms. The QRS widening is caused by:

    1. A. Muscarinic receptor blockade alone
    2. B. Hypokalemia caused by vomiting
    3. C. Cardiac sodium channel blockade
    4. D. An underlying bundle branch block
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    Answer: C. Cardiac sodium channel blockade

    In large overdoses diphenhydramine blocks cardiac sodium channels, like a tricyclic, which widens the QRS and can cause wide-complex dysrhythmias and seizures; sodium bicarbonate is used as for a tricyclic. Muscarinic blockade explains the tachycardia, dry skin, and delirium but not the wide QRS. Hypokalemia flattens T waves and causes U waves. A QRS that is new after the overdose points to the drug, not to a preexisting block.

18. A toxidrome that features hyperthermia, tachycardia, and agitation is dangerous mainly because of:

    1. A. Rhabdomyolysis, seizures, multiorgan failure
    2. B. Respiratory depression and aspiration of vomit
    3. C. Bradycardia and complete heart block
    4. D. Hypothermia, coagulopathy, and bleeding
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    Answer: A. Rhabdomyolysis, seizures, multiorgan failure

    Excess heat from muscle activity breaks down muscle and damages organs, so aggressive cooling and sedation are priorities. Respiratory depression is the main threat in depressant toxidromes.

19. A 30-year-old found with a syringe has pinpoint pupils and RR 6. You are ventilating well with a BVM, but two 2-mg naloxone doses produce no change. Glucose is 104 mg/dL and SpO2 is 96% with ventilation. The best next step is to:

    1. A. Give flumazenil for a possible benzodiazepine
    2. B. Keep ventilating; look for a non-opioid cause
    3. C. Stop ventilating to see if he breathes alone
    4. D. Give physostigmine to reverse the sedation
    Show answer

    Answer: B. Keep ventilating; look for a non-opioid cause

    Ventilation, not naloxone, is what keeps this patient alive. When adequate naloxone does not restore breathing, think of non-opioid sedatives mixed into the street supply, benzodiazepines, alcohol, clonidine, hypoxic brain injury, or a structural cause, and keep supporting the airway while transporting (further naloxone per protocol is reasonable but does not replace ventilation). Flumazenil is avoided in an unknown overdose because it can precipitate seizures in dependent or TCA-poisoned patients. Stopping ventilation to test spontaneous effort invites hypoxic arrest. Physostigmine is reserved for anticholinergic delirium and can cause bradycardia and seizures; it does not reverse sedative or opioid toxicity. (AHA 2023 toxicology focused update, opioid section; NASEMSO National Model EMS Clinical Guidelines, opioid poisoning.)

20. Withdrawal from opioids typically presents with:

    1. A. Yawning, rhinorrhea, diarrhea, dilated pupils
    2. B. Pinpoint pupils, coma, and slow breathing
    3. C. Seizures, hallucinations, and hyperthermia
    4. D. Dry skin, urinary retention, and confusion
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    Answer: A. Yawning, rhinorrhea, diarrhea, dilated pupils

    Opioid withdrawal is miserable but rarely life threatening and looks like the opposite of intoxication. Seizures and hallucinations are typical of alcohol or sedative withdrawal.

21. Which withdrawal syndrome is most likely to be life threatening?

    1. A. Opioid or heroin withdrawal symptoms
    2. B. Alcohol or benzodiazepine withdrawal
    3. C. Cannabis or marijuana withdrawal syndrome
    4. D. Nicotine or tobacco withdrawal
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    Answer: B. Alcohol or benzodiazepine withdrawal

    Alcohol and sedative withdrawal can cause seizures and delirium tremens with high mortality. Opioid withdrawal causes great discomfort but rarely death in healthy adults.

22. A patient with suspected toxidrome has a normal heart rate, normal pupils, and normal skin. You should conclude that:

    1. A. The patient cannot have taken a poison
    2. B. The ingestion was only a placebo
    3. C. No transport or evaluation is needed
    4. D. A serious ingestion is still possible
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    Answer: D. A serious ingestion is still possible

    Many dangerous toxins, such as acetaminophen or toxic alcohols, cause no early toxidrome. Normal findings early on cannot rule out a significant ingestion.

23. A patient taking sertraline is admitted for a skin infection. After a new drug is started, she becomes agitated, febrile, and tremulous with ankle clonus. Which new drug is the most likely trigger?

    1. A. Amoxicillin, an antibiotic
    2. B. Acetaminophen, a pain reliever
    3. C. Linezolid, an antibiotic
    4. D. Famotidine, an acid reducer
    Show answer

    Answer: C. Linezolid, an antibiotic

    Linezolid is also a weak monoamine oxidase inhibitor, so combining it with an SSRI can cause serotonin syndrome (agitation, fever, tremor, clonus). Amoxicillin has no serotonergic effect, which is why it is a trap: both options are antibiotics, but only linezolid blocks monoamine oxidase. Acetaminophen and famotidine do not raise serotonin.

24. A 4-year-old has bradycardia, wheezing, drooling, and diarrhea after playing in a garden shed. The antidote you would expect to give first is:

    1. A. Naloxone
    2. B. Flumazenil
    3. C. Physostigmine
    4. D. Atropine
    Show answer

    Answer: D. Atropine

    These cholinergic signs suggest an insecticide, and atropine blocks the muscarinic effects that cause bronchorrhea and bradycardia. Physostigmine increases acetylcholine and would make this patient worse.

25. Bradycardia with hypotension and a normal mental status in an overdose suggests toxicity from:

    1. A. Cocaine or a methamphetamine
    2. B. A beta or calcium channel blocker
    3. C. Diphenhydramine or another antihistamine
    4. D. Heroin or a different opioid
    Show answer

    Answer: B. A beta or calcium channel blocker

    Cardiovascular drugs can cause profound bradycardia and shock while the patient remains awake early on. Stimulants and anticholinergics cause tachycardia.