What are the most common and rarest acute poisonings, their characteristic clinical triads and signs, and the recommended management including drug dosing?

Most Common and Rarest Acute Poisonings: Clinical Triads and Management

Most Common Poisonings

1. Paracetamol (Acetaminophen) Poisoning - MOST COMMON

Paracetamol is the most frequently involved drug in acute poisonings, accounting for 35% of cases, and is the leading cause of poisoning-related hospitalizations 1.

Clinical Triad:

• Initially asymptomatic or mild nausea/vomiting (first 24 hours)
• Hepatotoxicity signs: right upper quadrant pain, elevated transaminases (24-72 hours)
• Hepatocellular necrosis with coagulopathy and encephalopathy (72+ hours if untreated)

Management:

• Activated charcoal: Administer immediately if within 2 hours of ingestion 2
• N-acetylcysteine (NAC): Must be given within 24 hours, ideally within 8-10 hours 2
  • Loading dose: 150 mg/kg IV over 1 hour
  • Followed by 50 mg/kg over 4 hours
  • Then 100 mg/kg over 16 hours
• Increase NAC dosing during hemodialysis if required 3
• Serum paracetamol level guides treatment decisions using Rumack-Matthew nomogram

2. Opioid Poisoning - EXTREMELY COMMON

Opioid overdoses account for most poisoning-related deaths in recent years, particularly in young adults 4.

Clinical Triad:

• CNS depression/coma
• Miosis (pinpoint pupils)
• Respiratory depression/apnea 5

Management:

• Naloxone 5:
  • IV/IO/IM: 0.2-2 mg (adult), 0.1 mg/kg (pediatric)
  • Intranasal: 2-4 mg, repeat every 2-3 minutes as needed
  • Maintenance infusion: Two-thirds of waking dose per hour
  • Critical caveat: Titrate to restore respiratory drive and airway reflexes, NOT full consciousness
  • Duration of action shorter than most opioids—continuous monitoring mandatory 2

3. Benzodiazepine Poisoning - VERY COMMON

Benzodiazepines are implicated in large numbers of poisoning deaths, usually combined with opioids or alcohol 5.

Clinical Presentation:

• CNS depression via GABA-A receptor agonism
• Respiratory compromise from loss of airway reflexes
• Hypoxemia and hypercarbia

Management:

• Primary approach: Airway management, bag-mask ventilation, intubation when needed 5
• If combined opioid/benzodiazepine poisoning suspected: Give naloxone FIRST 5
• Flumazenil (highly selective use only):
  • Adult: 0.2 mg IV, titrate up to 1 mg
  • Pediatric: 0.01 mg/kg
  • CONTRAINDICATIONS (Class 3: Harm) 5:
    • Chronic benzodiazepine use (precipitates withdrawal seizures)
    • Seizure disorder history
    • Co-ingestion with tricyclic antidepressants or other dysrhythmogenic drugs
    • Unknown ingestion history
  • Only use in: Pure benzodiazepine poisoning in low-risk patients (pediatric exploratory ingestions, iatrogenic procedural sedation overdoses) 5

---

Most Rare but Clinically Important Poisonings

1. Cyanide Poisoning - RARE BUT LETHAL

Occurs from smoke inhalation (house fires), industrial exposures, or rarely suicidal ingestions 6.

Clinical Triad:

• CNS depression with cardiovascular collapse
• Bradycardia
• Elevated plasma lactate with metabolic acidosis 5, 6

Additional Signs:

• Headache, vertigo, agitation, confusion progressing to coma
• Convulsions
• Rapid progression to death

Management:

• 100% oxygen immediately 6
• Hydroxocobalamin (preferred antidote) 5, 6:
  • Adult: 5 g IV
  • Pediatric: 70 mg/kg
  • Rapid cyanide binding with minimal side effects even if cyanide absent
  • Superior to other antidotes due to safety profile
• Sodium thiosulfate 5:
  • Adult: 12.5 g IV
  • Pediatric: 250 mg/kg
  • Acts more slowly; use as adjunct or for subacute poisoning 6
• Sodium nitrite 5:
  • Adult: 300 mg IV
  • Pediatric: 6 mg/kg
  • Watch for hypotension
• Correct acidosis and support blood pressure 6
• Assisted ventilation as needed

2. Organophosphate/Carbamate Poisoning - UNCOMMON IN DEVELOPED COUNTRIES

Agricultural pesticide exposures; rare in urban emergency departments but life-threatening 5.

Clinical Triad (Cholinergic Crisis):

• Bronchospasm and bronchorrhea (excessive secretions)
• Bradycardia
• Seizures

SLUDGE Syndrome:

• Salivation, Lacrimation, Urination, Defecation, GI cramping, Emesis

Management:

• Personal protective equipment mandatory for healthcare workers (Class 1, C-LD) 5
• Dermal decontamination immediately (Class 1, C-EO) 5
• Atropine (Class 1, A) 5:
  • Initial: 1-2 mg IV, doubled every 5 minutes until atropinization achieved
  • Pediatric: 0.02 mg/kg, doubled every 5 minutes
  • Atropinization endpoints: Clear chest auscultation, HR >80/min, SBP >80 mmHg
  • Maintenance infusion: 10-20% of loading dose per hour (up to 2 mg/h adults)
  • Much higher doses required than typical bradycardia treatment
• Pralidoxime (for organophosphates) (Class 2a, A) 5:
  • Adult: 1-2 g IV loading
  • Pediatric: 20-50 mg/kg
  • Maintenance: 400-600 mg/h (adult), 10-20 mg/kg/h (pediatric)
  • Do NOT withhold in unknown cholinesterase poisoning 5
• Benzodiazepines for seizures/agitation (Class 1, C-LD): Diazepam first-line or midazolam 5
• Early endotracheal intubation for life-threatening cases (Class 1, B-NR) 5
• AVOID: Succinylcholine and mivacurium (metabolized by cholinesterase) (Class 3: No Benefit) 5

3. Sodium Channel Blocker Poisoning - UNCOMMON BUT HIGH MORTALITY

Includes tricyclic antidepressants (TCAs), cocaine, carbamazepine, diphenhydramine, flecainide, quinidine 5.

Clinical Triad:

• QRS prolongation (>100 ms)
• Hypotension (cardiogenic or vasodilatory)
• Ventricular dysrhythmias/cardiovascular collapse

ECG Findings:

• Intraventricular conduction delay
• Terminal rightward axis deviation (R wave in aVR)
• These changes precede ventricular dysrhythmias 5

Management:

• Sodium bicarbonate (Class 1, highest evidence) 5:
  • Bolus: 50-150 mEq IV (adult), 1-3 mEq/kg (pediatric)
  • Infusion: Prepare 150 mEq/L solution, infuse at 1-3 mL/kg/h
  • Hypertonic sodium (1000 mEq/L adults, 500 mEq/L children)
  • Monitor: Hypernatremia, alkalemia, hypokalemia, hypochloremia 5
  • Both hypertonic sodium and alkalemia contribute to benefit
• Seizure management with benzodiazepines
• Avoid Class Ia and Ic antiarrhythmics

4. Digoxin/Cardiac Glycoside Poisoning - RARE

Yellow oleander and Bufo toad venom also cause cardiac glycoside toxicity 5.

Clinical Presentation:

• Bradycardia, heart block
• Ventricular dysrhythmias
• Hyperkalemia in acute overdose
• GI symptoms (nausea, vomiting)

Management:

• Digoxin immune Fab 5:
  • Acute overdose: 1 vial per 0.5 mg digoxin ingested
  • Chronic poisoning: Dose (vials) = [serum digoxin (ng/mL) × weight (kg)] / 100
  • Critically ill, unknown dose: 10-20 vials
  • Yellow oleander: 1200 mg (30 vials)
  • 1 vial = 40 mg Fab
  • Lower doses may be equally effective
• Atropine for bradycardia: 0.5-1 mg every 3-5 min up to 3 mg (adult), 0.02 mg/kg (pediatric) 5

---

Critical Pitfalls to Avoid

1. DO NOT delay supportive care waiting for toxicology results—most poisons lack rapid laboratory confirmation 5
2. DO NOT use gastric lavage routinely—serious adverse effects, only justified when life-threatening and drug not adsorbed by charcoal 2
3. NEVER use ipecac syrup 2
4. DO NOT use flumazenil in undifferentiated coma or mixed overdoses—risk of seizures and dysrhythmias outweighs benefits 5
5. Contact Poison Control (1-800-222-1222 in US) for expert guidance—board-certified toxicologists available 24/7 5
6. Adjust antidote dosing during extracorporeal treatments (NAC, ethanol, fomepizole require increased dosing during hemodialysis) 3

---

General Approach Algorithm

1. Immediate resuscitation: Airway, breathing, circulation—takes priority over poison identification 5
2. Recognize toxidrome if possible (opioid, cholinergic, anticholinergic, sympathomimetic, sedative-hypnotic)
3. Time-critical interventions:
   • Activated charcoal within 2 hours if appropriate
   • Specific antidotes when indicated
4. Supportive care: Correct acidosis, hypotension, seizures, dysrhythmias
5. Enhanced elimination when indicated (hemodialysis, urinary alkalinization)
6. Psychiatric evaluation for intentional ingestions once medically stable 2

555555526314