CCS Toxicology: Overdose & Poisoning Management for Step 3

Toxicology on CCS: Antidotes & Toxidromes

Toxicology cases on CCS test your ability to recognize toxidromes (clusters of signs/symptoms), identify the toxin, and administer the correct antidote or supportive care. Success depends on recognizing patterns, knowing which antidotes to order, and understanding decontamination timing. This guide covers the high-yield toxins, toxidromes, specific antidotes, and the step-by-step management approach examiners expect.

Toxidrome Recognition: The Foundation

Toxidromes are clinical syndromes caused by groups of toxins. Recognizing the pattern narrows your differential diagnosis dramatically.

Anticholinergic Toxidrome

Mnemonic: "Dry as a bone, blind as a bat, red as a beet, mad as a hatter"

Toxins: Atropine, antihistamines (diphenhydramine), tricyclic antidepressants, anticholinergic drugs (benztropine), jimsonweed

Clinical findings:

• Tachycardia

• Hyperthermia (unresponsive to cooling)

• Dilated pupils

• Dry mouth, dry skin

• Urinary retention

• Decreased bowel sounds

• Agitation, hallucinations, confusion, delirium

• NO diaphoresis (key differentiator—cholinergic will have diaphoresis)

Management:

• Activated charcoal (if accessible ingestion)

• Supportive: Cooling measures, IV fluids, sedation with benzodiazepines

• Physostigmine 1-2 mg IV over 2-5 min (cholinesterase inhibitor) if life-threatening symptoms

◦ Caution: Can cause cholinergic crisis if toxidrome misidentified; avoid if tricyclic antidepressants suspected (risk of arrhythmias)

• Monitor EKG closely

Cholinergic Toxidrome

Mnemonic: "SLUDGE" (Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis)

Toxins: Organophosphates (pesticides), carbamates, nerve agents, mushrooms (Amanita muscaria)

Clinical findings:

• Muscarinic: Salivation, lacrimation, miosis (pinpoint pupils), muscle fasciculations, bronchospasm, bradycardia

• Nicotinic: Muscle fasciculations, tremor, paralysis

• Central: Confusion, anxiety, seizures

• Diaphoresis (profuse—key differentiator from anticholinergic)

• Bronchorrhea (excessive bronchial secretions)

Management:

• Decontamination: Remove clothing, skin washing

• Atropine 1-2 mg IV q5-10min until signs of atropinization (dry mouth, heart rate >100)

◦ Large doses may be needed (up to 100 mg+)

◦ Reverses muscarinic effects only

• Pralidoxime (2-PAM) 1-2 g IV over 30 min (reactivates acetylcholinesterase if given early)

◦ Timing critical: Most effective if given within hours of exposure

• Seizure management: Benzodiazepines

• Ventilatory support if bronchospasm/paralysis

Sympathomimetic Toxidrome

Hypertension, tachycardia, hyperthermia, agitation

Toxins: Cocaine, amphetamines, MDMA (ecstasy), pseudoephedrine, phentermine

Clinical findings:

• Severe hypertension (can be extreme, >200 mmHg systolic)

• Tachycardia, arrhythmias

• Hyperthermia (can reach 41-42°C+)

• Agitation, paranoia, hallucinations

• Tremor, mydriasis

• Diaphoresis

• Seizures (cocaine, amphetamines)

• Rhabdomyolysis, acute kidney injury

Management:

• Benzodiazepines: Lorazepam 2-4 mg IV, repeat q5-10min (first-line for agitation/seizures)

• Antihypertensives (only if severely elevated BP):

◦ Phentolamine 5-10 mg IV bolus (non-selective alpha-blocker, best for cocaine hypertension)

◦ OR Nitroprusside infusion (direct vasodilator; requires ICU monitoring)

◦ Avoid beta-blockers alone (unopposed alpha, worsens hypertension)

• Cooling: Ice packs, cold IV fluids, evaporative cooling for hyperthermia

• Rhabdomyolysis management: Aggressive IV fluids (LR preferred), urine alkalinization with sodium bicarbonate (target urine pH >6.5), monitor CK/myoglobin

• NO antidote specific

Opioid Toxidrome

Respiratory depression, pinpoint pupils, coma

Toxins: Opioids (heroin, morphine, oxycodone, fentanyl, hydrocodone)

Clinical findings:

• Severe respiratory depression (RR <8-10, shallow)

• Pinpoint pupils (pathognomonic)

• Altered mental status, coma

• Hypoxia, hypercapnia

• Bradycardia (mild)

• Hypothermia

Management:

• Oxygen: High-flow initially; may need bag-valve-mask if apneic

• Naloxone (Narcan) 0.04 mg IV/IM/intranasal (opioid antagonist)

◦ Repeat q2-3min if inadequate response; can escalate to 2 mg

◦ Reverses respiratory depression within 1-2 minutes

◦ Duration: 30-120 min (shorter than many opioids → re-sedation possible; repeat dosing or infusion may be needed)

• Continued monitoring; may need naloxone infusion if long-acting opioid (methadone, sustained-release morphine)

• Agitation post-naloxone: Expected (acute withdrawal); reassure, no additional medication needed unless dangerous behavior

> Study Tip: The StudyCCS question bank includes 5+ toxicology cases showing toxidrome recognition in real clinical scenarios—and the exact moment when you give naloxone for opioid overdose versus phentolamine for sympathomimetic hypertension. These cases highlight the danger of mis-identifying toxidromes.

Sedative-Hypnotic Toxidrome

CNS depression, respiratory depression, hypotension

Toxins: Benzodiazepines, barbiturates, alcohol, gamma-hydroxybutyrate (GHB), chloral hydrate

Clinical findings:

• Altered mental status, coma

• Respiratory depression (often profound)

• Hypotension

• Hypothermia

• Decreased reflexes, flaccidity

• Miosis (pupils constricted)

Management:

• Airway management: Intubation if unable to protect airway or SpO₂ <90% despite O₂

• Supportive: IV fluids for hypotension

• Flumazenil 0.2 mg IV over 15-30 seconds, repeat q1min up to 3-4 mg total (benzodiazepine antagonist)

◦ Use with EXTREME CAUTION: Only for suspected benzodiazepine overdose (not mixed overdose)

◦ CONTRAINDICATED if: Tricyclic antidepressants, seizure disorder, chronic benzodiazepine use (risk of severe withdrawal seizures)

◦ Half-life shorter than many benzos → re-sedation common

• NO antidote for barbiturates/GHB/chloral hydrate: Supportive care only

• Activated charcoal if early presentation

Hallucinogenic/Stimulant Toxidrome

Pupils dilated, agitation, hallucinations, normal vital signs (often)

Toxins: LSD, psilocybin, PCP

Clinical findings:

• Hallucinations (visual, auditory)

• Agitation, paranoia

• Mydriasis

• Tremor

• Normal to mild tachycardia, hypertension

• Normal temperature (often)

• PCP specifically: Vertical/horizontal nystagmus, aggressive behavior, analgesia (feeling no pain)

Management:

• Reassurance, calm environment (key intervention for LSD/psilocybin)

• Benzodiazepines if agitation (lorazepam 2-4 mg IV)

• NO specific antidote

• Watch for rhabdomyolysis (PCP causes loss of pain sensation → self-injury risk)

Specific Toxins & Antidotes: The High-Yield Table

> Practice Alert: Antidote selection appears in nearly every toxicology CCS case. The StudyCCS question bank includes detailed cases showing when to use naloxone (opioid) versus flumazenil (benzo) versus fomepizole (toxic alcohol)—and the danger of wrong antidote selection. You'll practice the complete toxidrome recognition and antidote workup that examiners test.

Acetaminophen Overdose: The Rumack-Matthew Nomogram

Acetaminophen is the most common intentional overdose toxin in the U.S. The Rumack-Matthew nomogram determines if NAC (N-acetylcysteine) is needed.

Toxicity Threshold

• Normal: <150 mcg/mL at 4 hours post-ingestion

• 150-300 mcg/mL: Nomogram line—risk of hepatotoxicity

• >300 mcg/mL: Definite hepatotoxicity

Management by Time Since Ingestion

<4 hours post-ingestion:

• Plot serum acetaminophen level on nomogram

• If above nomogram line: Start NAC immediately

• If below nomogram line: No NAC needed

4-24 hours:

• Use nomogram (nomogram valid)

• If above line: Start NAC

• If below: No NAC needed

>24 hours:

• Nomogram not applicable

• If ANY acetaminophen ingestion + concern for toxicity: Start NAC (better safe than sorry; NAC safe even if not toxic)

• Check INR, LFTs to assess liver dysfunction

NAC Dosing & Administration

IV NAC (preferred):

1. Loading: 150 mg/kg IV in 200 mL of 5% dextrose or normal saline over 1 hour

2. Second phase: 50 mg/kg IV in 500 mL D5W over 4 hours

3. Third phase: 100 mg/kg IV in 1000 mL D5W over 16 hours

• Total course: ~20 hours

Oral NAC (if IV unavailable):

• Loading: 140 mg/kg PO

• Then: 70 mg/kg q4h × 17 doses

• Unpleasant taste; mix with juice/soda

Mechanism

NAC replenishes glutathione stores in liver, allowing conjugation of toxic acetaminophen metabolite (NAPQI) into harmless compounds.

Decontamination: Timing & Approach

Activated Charcoal

• Timing: Most effective if given within 1-2 hours of ingestion

• Dose: 25-100 g (pediatric: 0.5-1 g/kg) as slurry in water

• Mechanism: Binds toxin in GI tract, prevents absorption

• Efficacy drops significantly after 2 hours (some toxins: 4 hours)

• Not effective for: Metals (iron, lithium), alcohols, hydrocarbons

• Caution: Risk of aspiration if altered mental status; may require intubation first

Gastric Lavage (Stomach Pumping)

• Outdated: Not recommended routinely (ineffective, risk of aspiration, esophageal rupture)

• Limited role: Only if ingestion of highly toxic substance within 30-60 minutes AND mental status intact

Induced Vomiting (Ipecac)

• Not recommended: Dangerous, ineffective, delays definitive treatment

Whole Bowel Irrigation

• Polyethylene glycol (GoLYTELY): 500 mL/hr PO/NG until clear

• Indications: Iron, lithium, sustained-release medications (not amenable to charcoal)

Essential Toxicology Workup

Labs for Any Overdose/Poisoning Case

1. Serum acetaminophen level (present in many combination products)

2. Salicylate level (aspirin overdose)

3. Alcohol levels: Ethanol, methanol, ethylene glycol

4. Troponin, EKG (cardiac toxins: tricyclics, sympathomimetics, digoxin, calcium channel blockers)

5. Lactate (hypoxia, sepsis, cyanide)

6. Urinalysis: Crystals (ethylene glycol shows Ca oxalate crystals), myoglobin (rhabdomyolysis)

7. BMP: Potassium (hyperkalemia with digitalis, anticholinergics; hypokalemia with beta-blockers), glucose, creatinine

8. LFTs: AST, ALT, bilirubin (acetaminophen hepatotoxicity)

9. INR/PT: Liver synthetic function (late sign of acetaminophen toxicity)

10. Methemoglobin level (if suspected nitrate/aniline exposure)

11. Carboxyhemoglobin (if carbon monoxide suspected)

12. Urine drug screen (detects common drugs; not always available/reliable)

Poison Control & Risk Assessment

Call Poison Control: 1-800-222-1222 (in U.S.)

• Available 24/7

• Provides toxin-specific guidance

• No cost

• Patient confidentiality maintained

Risk stratification:

• Minimal risk: Non-toxic dose, asymptomatic

• Moderate risk: Symptomatic but stable, amenable to decontamination

• High risk: Life-threatening symptoms, large ingestion, unknown substance, self-harm history

Psychiatric clearance: Required before discharge for intentional overdose; suicidality assessment

Don't-Miss Toxicological Diagnoses

When a patient presents with altered mental status, seizures, or cardiopulmonary instability of unclear etiology:

• Cyanide poisoning: Cherry-red skin, normal O₂ sat but metabolic acidosis; give hydroxocobalamin/sodium thiosulfate

• Carbon monoxide: Headache, confusion, carboxyhemoglobin >30%; give high-flow oxygen, consider hyperbaric oxygen

• Salicylate toxicity: Mixed respiratory alkalosis + metabolic acidosis; pulmonary edema risk; urine alkalinization

• Metformin-associated lactic acidosis: Metformin + renal impairment; high lactate, severe acidosis; dialysis needed

• Serotonin syndrome: Serotonin agonists (SSRIs, tramadol, linezolid); agitation, tremor, hyperreflexia, hyperthermia; benzodiazepines + cyproheptadine

• Neuroleptic malignant syndrome: Antipsychotics; fever, rigidity, altered mental status, CK elevation; dopamine agonist (bromocriptine) + supportive care

• Malignant hyperthermia: Anesthetic exposure; extreme fever, muscle rigidity, CK elevation; stop anesthesia, give dantrolene 2.5 mg/kg IV

Complete Order Set: Toxicology Workup

Immediate (All Toxicology Cases)

• ABG or venous blood gas (pH, pCO₂, assess respiratory status)

• EKG (baseline, cardiac toxins)

• Continuous cardiac monitoring

• IV access × 2

• Oxygen therapy

• Glucose check (fingerstick)

Labs (Stat)

• Acetaminophen level

• Salicylate level

• Alcohol levels (ethanol, methanol, ethylene glycol)

• CBC, BMP, LFTs

• Troponin

• Lactate

• Urinalysis (myoglobin, crystals)

• Urine drug screen

Secondary (Based on Presentation)

• Chest X-ray (if respiratory symptoms, aspiration risk)

• Head CT (if altered mental status + focal findings)

• Methemoglobin level

• Carboxyhemoglobin

• Serum osmolality (toxic alcohols)

• INR/PT

• Comprehensive metabolic panel

Specific to Suspected Toxin

• Digoxin level (digoxin toxicity)

• Theophylline level

• Lithium level

• Phenytoin/phenobarbital levels

• Chloroquine/quinine levels (cardiac toxins)

2-Minute Screen

Toxicology recognition in 120 seconds:

1. Anticholinergic: Dry mouth, dilated pupils, no diaphoresis, agitation; consider physostigmine

2. Cholinergic: Salivation, pinpoint pupils, bronchorrhea, diaphoresis; atropine + pralidoxime

3. Sympathomimetic: Hypertension, tachycardia, hyperthermia, agitation; benzodiazepines + phentolamine

4. Opioid: Respiratory depression, pinpoint pupils, coma; naloxone 0.04 mg IV

5. Sedative-hypnotic: CNS depression, respiratory depression; airway management; flumazenil ONLY if isolated benzo

6. Acetaminophen: Rumack-Matthew nomogram; NAC if above nomogram line

7. Toxic alcohols: Fomepizole to block metabolism

8. Cyanide: Hydroxocobalamin

9. Decontamination: Activated charcoal <2 hours post-ingestion

10. Always: Poison control 1-800-222-1222; psychiatric clearance for intentional overdose

Related Articles

• CCS Altered Mental Status: DDx and Workup

• CCS Cardiac Arrhythmias: Recognition & Acute Management

• CCS Seizures: Status Epilepticus Management

• CCS Rhabdomyolysis: Diagnosis & Acute Kidney Injury Prevention

Ready to practice? The StudyCCS question bank includes 8+ toxicology cases covering high-yield overdoses—from opioid respiratory depression requiring naloxone to acetaminophen toxicity with Rumack-Matthew nomogram application, sympathomimetic hypertension, and toxic alcohol management. Each case walks you through toxidrome recognition, antidote selection, and the exact workup sequence. Real-time scoring shows where you earn points on rapid antidote administration and decontamination timing. Try a case today.