A 24-year-old woman presents 10 hours after taking an unknown number of acetaminophen 500-mg tablets. She is nauseated but alert. Her serum acetaminophen concentration at 10 hours after ingestion is 120 mcg/mL (treatment line at 10 hours is about 50 mcg/mL). AST is 38 units/L and INR 1.0. Which action is most appropriate?

Start IV acetylcysteine without delay

Repeat the level in 4 hours before deciding

Start acetylcysteine only if AST rises

An 82-year-old woman with heart failure and atrial fibrillation takes digoxin 0.25 mg daily; clarithromycin was started 5 days ago. She presents with nausea, yellow vision, and lightheadedness. HR is 38 beats/min with high-grade AV block, BP 82/50 mm Hg, K 5.4 mEq/L, SCr 1.6 mg/dL, and digoxin level 3.1 ng/mL. Which treatment is most appropriate?

Hold digoxin and recheck in 24 hours

A 36-year-old woman in the ICU developed serotonin syndrome after linezolid was added to her duloxetine. Both were stopped 6 hours ago, and she has received lorazepam 2 mg IV twice with supportive care. She remains agitated with temperature 38.8°C, HR 118 beats/minute, diaphoresis and inducible clonus, and she can take oral medications. Which therapy should be added?

Cyproheptadine 12 mg load, then 2 mg every 2 hours

Bromocriptine 2.5 mg orally every 8 hours, titrated up

Acetaminophen 1 g orally every 6 hours

A 45-year-old man (80 kg) ingested about 40 tablets of amlodipine 10 mg 3 hours ago. He is alert, BP 74/40 mm Hg and HR 96 beats/minute despite 2 L of crystalloid and calcium gluconate 3 g IV. Glucose is 210 mg/dL and K 3.9 mEq/L. Which therapy should be started next?

Insulin 1 unit/kg IV bolus plus dextrose

Lipid emulsion 20% 1.5 mL/kg IV, then infusion

Sodium bicarbonate 1–2 mEq/kg IV bolus

A 45-year-old man is brought to the emergency department after smoking crack cocaine. He is severely agitated and diaphoretic with temperature 40.6°C, HR 142 beats/minute, BP 186/108 mm Hg and CK 3,200 units/L. ECG shows sinus tachycardia without ST changes. Active external cooling has been started. Which medication is most appropriate?

Diazepam 10 mg IV, repeated as needed

Acetaminophen 1 g IV every 6 hours

Propranolol 1 mg IV every 5 minutes

Dantrolene 2.5 mg/kg IV, repeated as needed

A 68-year-old man is brought in after eating jimsonweed seeds. He has agitated delirium, picking at the air, dry flushed skin, mydriasis, urinary retention, temperature 38.9°C and HR 124 beats/minute. ECG shows sinus tachycardia with QRS 88 ms and QTc 440 ms. He has no seizures or history of reactive airway disease. Which medication is most appropriate?

Physostigmine 1 mg IV over 5 minutes

Neostigmine 1 mg IV over 5 minutes

Haloperidol 5 mg IV, repeated every 30 minutes

A 38-year-old man is found confused next to an open container of antifreeze. Labs: Na 140 mEq/L, Cl 100 mEq/L, HCO3 12 mEq/L, BUN 14 mg/dL, glucose 90 mg/dL, measured osmolality 330 mOsm/kg, ethanol undetectable, SCr 1.1 mg/dL. Calcium oxalate crystals are seen in the urine. Which treatment should be started immediately?

Fomepizole 15 mg/kg IV loading dose

Pyridoxine and thiamine IV alone

Ethanol 10% IV to a blood level of 100 mg/dL

Sodium bicarbonate infusion alone

A 75-year-old woman with metastatic cancer pain takes oxycodone ER 60 mg twice daily. She is found minimally responsive with RR 6 breaths/minute, SpO2 84% on room air and pinpoint pupils after an extra dose was given in error. Bag-mask ventilation is started and she has IV access. Which naloxone regimen is most appropriate?

Naloxone 0.04 mg IV, repeated every 2 minutes

Naloxone 2 mg IV, repeated every 2 minutes

Naloxone 0.4 mg IV, repeated every 2 minutes

Naloxone 4 mg intranasal, repeated every 2 minutes

BCPS Toxicology: Toxidromes and Their Antidotes

1Six toxidromes and their tells

Core toxidromes, the classic findings and the sign that separates each from its look-alike
Toxidrome	Classic findings	Separating sign
Sympathomimetic (cocaine, amphetamines)	Tachycardia, hypertension, hyperthermia, dilated pupils, agitation	Skin is sweaty
Anticholinergic (diphenhydramine, tricyclics, some plants)	Tachycardia, hyperthermia, dilated pupils, flushed skin, urinary retention, delirium	Skin is dry and bowel sounds are quiet
Cholinergic (organophosphate and carbamate insecticides)	Salivation, lacrimation, urination, diarrhea, vomiting; bradycardia, bronchorrhea, bronchospasm; fasciculations	Wet everywhere, with small pupils
Opioid	Depressed consciousness, slow shallow breathing, pinpoint pupils	The respiratory rate is the number that matters
Sedative-hypnotic (benzodiazepines, barbiturates)	Depressed consciousness, slurred speech, ataxia	Pupils often normal; breathing better kept with a benzodiazepine alone
Serotonin syndrome	Agitation, tremor, hyperreflexia, clonus, diarrhea, hyperthermia	Clonus, most marked in the legs

Mixed ingestions blur every row; treat the findings in front of you, and check acetaminophen and salicylate levels in any intentional overdose.

2Serotonin syndrome or neuroleptic malignant syndrome

≠ marks rows where the two differ.

The two hyperthermic syndromes pharmacists are asked to separate
Point of comparison	Serotonin syndrome	Neuroleptic malignant syndrome
Differs: Usual trigger	Two or more serotonergic drugs, or a dose increase: SSRIs, SNRIs, MAO inhibitors, tramadol	Dopamine antagonists such as antipsychotics or metoclopramide, or abrupt withdrawal of levodopa
Differs: Onset	Hours after the change	Days to weeks
Differs: Muscle findings	Clonus and hyperreflexia	Lead-pipe rigidity with slow reflexes
Differs: Mental status and gut	Agitation; hyperactive bowel, diarrhea	Stupor or mutism; bowel not overactive
Differs: Course	Usually settles within about a day once the drugs stop	Resolves over days, longer after depot antipsychotics
Differs: Drug therapy beyond supportive care	Benzodiazepines; cyproheptadine, a 5-HT2A antagonist, as the adjunct	Benzodiazepines; dantrolene or bromocriptine in severe cases

First steps are the same for both: stop the causative drugs, cool, and give fluids and benzodiazepines.

3Antidotes that need more than a name

Knowing which antidote fits a toxidrome is half the answer. The other half is when it does harm, and that half is the one flashcards tend to skip.

3.1Flumazenil

It reverses benzodiazepines, but the label carries a boxed warning about seizures. In a patient who takes benzodiazepines long term, or who may have co-ingested a drug that lowers the seizure threshold such as a tricyclic, reversal can trigger seizures that are then hard to treat. That is why it is not a routine step in an unknown overdose.

3.2Atropine and pralidoxime

In organophosphate poisoning they do different jobs. Atropine blocks the muscarinic effects and is titrated to dry the airway secretions, not to a heart rate. Pralidoxime reactivates acetylcholinesterase and reaches the nicotinic weakness atropine cannot, but only before the enzyme-poison bond ages.

The airway findings in that toxidrome come from the same muscarinic receptors that long-acting antimuscarinic inhalers block on purpose in COPD; the inhaler side is covered in asthma vs COPD inhaler therapy.

3.3Naloxone

Its effect is shorter than that of many opioids, especially long-acting and extended-release products, so a patient who wakes up can stop breathing again. Observation after reversal is part of the treatment.

4Poisoned patients, one syndrome each

Each case describes a poisoning by its findings. Name the toxidrome to yourself first; the treatment follows from it.

Study cases written by our editors, not BPS items. The real BCPS exam is computer-based multiple choice, answered in order with no going back.

Case 1 of 9 · 0 answered

How case rounds work

Pick an option to see the verdict and a note on every option. Keys while the round has focus: 1–5 or A–E answer, ← → move between cases. Nothing is saved or sent anywhere.

Case 01
A 24-year-old woman presents 10 hours after taking an unknown number of acetaminophen 500-mg tablets. She is nauseated but alert. Her serum acetaminophen concentration at 10 hours after ingestion is 120 mcg/mL (treatment line at 10 hours is about 50 mcg/mL). AST is 38 units/L and INR 1.0. Which action is most appropriate?
Pick an option: the verdict and a note on every option open here.
Best answer: C.
A level above the Rumack-Matthew treatment line at a known time after ingestion is an indication for acetylcysteine, and its protection is greatest when started within 8–10 hours, so treatment should begin immediately. Waiting for a repeat level is the tempting cautious choice, but the decision line has already been crossed and delay increases hepatotoxicity. Normal AST does not exclude evolving liver injury, and activated charcoal is of little benefit 10 hours after ingestion and is not an antidote.
A
The level is already above the treatment line at a known time, so another level only delays the antidote.
B
A normal AST does not rule out evolving liver injury, and waiting for it to rise loses acetylcysteine’s best window.
C
Correct. A 10-hour level of 120 mcg/mL is well above the nomogram line, and acetylcysteine works best when started by 8–10 hours.
D
Charcoal does little 10 hours after ingestion and is not an antidote for acetaminophen.
Case 02
An 82-year-old woman with heart failure and atrial fibrillation takes digoxin 0.25 mg daily; clarithromycin was started 5 days ago. She presents with nausea, yellow vision, and lightheadedness. HR is 38 beats/min with high-grade AV block, BP 82/50 mm Hg, K 5.4 mEq/L, SCr 1.6 mg/dL, and digoxin level 3.1 ng/mL. Which treatment is most appropriate?
Pick an option: the verdict and a note on every option open here.
Best answer: A.
Symptomatic bradyarrhythmia with hypotension, hyperkalemia, and a markedly elevated level (raised by clarithromycin’s P-glycoprotein inhibition) are indications for digoxin immune Fab, which binds digoxin and reverses toxicity within an hour. IV calcium for the hyperkalemia is a tempting choice, but it does not treat the cause and has historically been discouraged in digoxin toxicity. Hemodialysis removes little digoxin because of its large volume of distribution, and simply holding the drug is inadequate for an unstable patient.
A
Correct. Bradycardia with AV block, hypotension, K 5.4 and a level of 3.1 are clear indications for digoxin immune Fab.
B
Digoxin’s large volume of distribution means dialysis removes very little of it.
C
Calcium does not treat the cause, and its use in digoxin toxicity has long been discouraged.
D
She is unstable with high-grade AV block; holding the drug alone is far too passive.
Case 03
A 36-year-old woman in the ICU developed serotonin syndrome after linezolid was added to her duloxetine. Both were stopped 6 hours ago, and she has received lorazepam 2 mg IV twice with supportive care. She remains agitated with temperature 38.8°C, HR 118 beats/minute, diaphoresis and inducible clonus, and she can take oral medications. Which therapy should be added?
Pick an option: the verdict and a note on every option open here.
Best answer: A.
For moderate serotonin syndrome that persists after the causative drugs are stopped and benzodiazepines are given, cyproheptadine, a 5-HT2A antagonist available only orally or by tube, is the recommended adjunct (12 mg load, then 2 mg every 2 hours while symptoms continue). Dantrolene is the tempting choice for a hyperthermic rigid patient, but it has no proven benefit in serotonin syndrome. Bromocriptine treats neuroleptic malignant syndrome and can worsen serotonin toxicity, and acetaminophen does not lower hyperthermia driven by muscle activity.
A
Correct. Cyproheptadine, an oral 5-HT2A antagonist, is the adjunct for moderate serotonin syndrome still active after benzodiazepines.
B
Bromocriptine is a dopamine agonist for NMS and can worsen serotonin toxicity.
C
Dantrolene is tempting for a hot, rigid patient but has no proven benefit in serotonin syndrome.
D
Her fever comes from muscle activity, not a hypothalamic set point, so antipyretics do not help.
Case 04
A 55-year-old man started haloperidol 10 mg daily 5 days ago. He now has temperature 40.4°C, lead-pipe rigidity, fluctuating consciousness, BP swinging between 90/50 and 180/110 mm Hg, and CK 22,000 units/L. Haloperidol has been stopped, and IV fluids, cooling and lorazepam have been started, but rigidity and hyperthermia persist. Which medication should be added?
Pick an option: the verdict and a note on every option open here.
Best answer: A.
Severe neuroleptic malignant syndrome with persistent hyperthermia and rigidity despite stopping the drug and supportive care calls for dantrolene, which relaxes skeletal muscle by blocking calcium release, reducing heat production and rhabdomyolysis (bromocriptine is the dopaminergic alternative). Benztropine is the tempting choice for antipsychotic motor effects, but it treats dystonia, not NMS, and its anticholinergic effect impairs heat loss. Cyproheptadine treats serotonin syndrome, and giving another antipsychotic such as olanzapine worsens NMS.
A
Correct. Persistent rigidity and hyperthermia in severe NMS call for dantrolene, which reduces muscle heat production and rhabdomyolysis.
B
Benztropine treats acute dystonia, not NMS, and its anticholinergic effect impairs heat loss.
C
Cyproheptadine is the serotonin syndrome antidote; this picture is NMS after haloperidol.
D
Another antipsychotic, even an atypical one, worsens NMS.
Case 05
A 45-year-old man (80 kg) ingested about 40 tablets of amlodipine 10 mg 3 hours ago. He is alert, BP 74/40 mm Hg and HR 96 beats/minute despite 2 L of crystalloid and calcium gluconate 3 g IV. Glucose is 210 mg/dL and K 3.9 mEq/L. Which therapy should be started next?
Pick an option: the verdict and a note on every option open here.
Best answer: C.
High-dose insulin euglycemia therapy (1 unit/kg bolus, then an infusion, with dextrose and potassium monitoring) is first-line for calcium channel blocker poisoning with shock once fluids and calcium have failed; it improves myocardial glucose use and contractility. Glucagon is a β-blocker antidote with little proven benefit in calcium channel blocker poisoning. Lipid emulsion is a last-resort rescue for refractory instability, and bicarbonate treats sodium channel blockade (wide QRS), which is not present here.
A
Lipid emulsion is a last-resort rescue for refractory instability, not the next step after calcium.
B
Bicarbonate treats sodium channel blockade with a wide QRS, which is not described here.
C
Correct. High-dose insulin with dextrose is first-line once fluids and calcium fail in CCB shock; it restores myocardial glucose use.
D
Glucagon is an antidote for beta-blocker poisoning and has little proven benefit with calcium channel blockers.
Case 06
A 45-year-old man is brought to the emergency department after smoking crack cocaine. He is severely agitated and diaphoretic with temperature 40.6°C, HR 142 beats/minute, BP 186/108 mm Hg and CK 3,200 units/L. ECG shows sinus tachycardia without ST changes. Active external cooling has been started. Which medication is most appropriate?
Pick an option: the verdict and a note on every option open here.
Best answer: B.
Cocaine hyperthermia is driven by psychomotor agitation and central sympathetic outflow, so titrated IV benzodiazepines plus rapid cooling are first-line; they reduce muscle heat production, HR and BP. Propranolol is the tempting choice for the tachycardia, but β-blockade leaves α-stimulation unopposed, which can worsen hypertension and coronary vasospasm. Acetaminophen does not lower hyperthermia that is not mediated by the hypothalamic set point, and dantrolene is for malignant hyperthermia, with no proven benefit in cocaine toxicity.
A
Cocaine hyperthermia is driven by agitation and muscle activity, not a hypothalamic set point, so acetaminophen does not help.
B
Correct. Titrated IV benzodiazepines calm the agitation and lower heat production, HR and BP; cooling continues alongside.
C
A beta-blocker leaves alpha-stimulation unopposed, which can worsen hypertension and coronary vasospasm.
D
Dantrolene is the malignant hyperthermia drug and has no proven benefit in cocaine toxicity.
Case 07
A 68-year-old man is brought in after eating jimsonweed seeds. He has agitated delirium, picking at the air, dry flushed skin, mydriasis, urinary retention, temperature 38.9°C and HR 124 beats/minute. ECG shows sinus tachycardia with QRS 88 ms and QTc 440 ms. He has no seizures or history of reactive airway disease. Which medication is most appropriate?
Pick an option: the verdict and a note on every option open here.
Best answer: D.
Physostigmine is a tertiary-amine cholinesterase inhibitor that crosses the blood-brain barrier and reverses central anticholinergic delirium; it is safe here because the QRS is narrow (it should be avoided with QRS widening such as in TCA poisoning). Neostigmine is the tempting look-alike, but as a quaternary amine it does not enter the CNS and cannot reverse delirium. Haloperidol adds anticholinergic and QT effects and can worsen hyperthermia, and cyproheptadine is itself anticholinergic.
A
Neostigmine is a quaternary amine that does not cross into the CNS, so it cannot reverse the delirium.
B
Haloperidol adds anticholinergic and QT effects and can worsen hyperthermia.
C
Cyproheptadine is itself anticholinergic and would add to the toxidrome.
D
Correct. Physostigmine crosses the blood-brain barrier and reverses central anticholinergic delirium; the narrow QRS makes it safe.
Case 08
A 38-year-old man is found confused next to an open container of antifreeze. Labs: Na 140 mEq/L, Cl 100 mEq/L, HCO3 12 mEq/L, BUN 14 mg/dL, glucose 90 mg/dL, measured osmolality 330 mOsm/kg, ethanol undetectable, SCr 1.1 mg/dL. Calcium oxalate crystals are seen in the urine. Which treatment should be started immediately?
Pick an option: the verdict and a note on every option open here.
Best answer: A.
An anion gap of 28 with an osmolal gap of about 40 mOsm/kg and oxalate crystals indicates ethylene glycol poisoning, and fomepizole blocks alcohol dehydrogenase so the toxic metabolites (glycolate, oxalate) stop forming; hemodialysis is added for severe acidosis or kidney injury. IV ethanol also blocks the enzyme, but it causes CNS depression and hypoglycemia, needs level monitoring, and is reserved for when fomepizole is unavailable. Bicarbonate, pyridoxine and thiamine are adjuncts that do not stop metabolite formation.
A
Correct. High anion and osmolal gaps with oxalate crystals mean ethylene glycol; fomepizole blocks the metabolism that makes the toxins.
B
These vitamins help shunt metabolism toward less toxic products but do nothing to stop toxic metabolites forming.
C
Ethanol also blocks alcohol dehydrogenase but brings CNS depression and hypoglycemia; it is used when fomepizole is unavailable.
D
Bicarbonate treats the acidosis but does not halt the formation of glycolate and oxalate.
Case 09
A 75-year-old woman with metastatic cancer pain takes oxycodone ER 60 mg twice daily. She is found minimally responsive with RR 6 breaths/minute, SpO2 84% on room air and pinpoint pupils after an extra dose was given in error. Bag-mask ventilation is started and she has IV access. Which naloxone regimen is most appropriate?
Pick an option: the verdict and a note on every option open here.
Best answer: B.
In a patient physically dependent on opioids, naloxone should be diluted and given in small increments (about 0.04 mg every 2 minutes) titrated to adequate respiration rather than full alertness, which restores breathing without precipitating withdrawal and a pain crisis. Repeated doses of 0.4–2 mg are standard for opioid-naive overdoses but risk abrupt withdrawal, severe pain, agitation and catecholamine surge in this patient. The 4-mg intranasal device is meant for lay rescuers in the field and delivers a large, non-titratable dose.
A
2 mg boluses suit opioid-naive overdoses; in a tolerant cancer patient they can trigger severe withdrawal and a pain crisis.
B
Correct. In an opioid-dependent patient naloxone is diluted and given 0.04 mg at a time, titrated to breathing rather than full alertness.
C
0.4 mg is a standard naive-patient dose that still risks abrupt withdrawal in someone on high-dose oxycodone.
D
The 4-mg nasal spray is a lay-rescuer device that delivers a large dose that cannot be titrated.

5References

Flumazenil prescribing information, boxed warning (DailyMed). As of October 27, 2026.
Pralidoxime chloride prescribing information (DailyMed). As of October 27, 2026.
Naloxone hydrochloride injection prescribing information (DailyMed). As of October 27, 2026.

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