What is the treatment for a tricyclic (TCA) antidepressant overdose?

Treatment of Tricyclic Antidepressant (TCA) Overdose

Sodium bicarbonate administration is the cornerstone of treatment for life-threatening tricyclic antidepressant overdose, with initial doses of 1-2 mEq/kg IV bolus followed by additional doses as needed to maintain arterial pH of 7.45-7.55. 1

Initial Assessment and Management

• Airway and Breathing

  • Immediately assess airway patency and breathing status
  • Provide bag-mask ventilation for respiratory depression
  • Consider early endotracheal intubation for severe toxicity or respiratory failure

• Circulation

  • Establish IV access and initiate cardiac monitoring
  • Obtain 12-lead ECG to assess for QRS prolongation (>100 ms), which predicts serious complications 2
  • Monitor vital signs continuously

• Decontamination

  • Administer activated charcoal (30-50g) if within 1-2 hours of ingestion and patient has intact airway reflexes 2

Specific Interventions for Cardiotoxicity

First-Line Treatment

• Sodium Bicarbonate Therapy
  • Administer 1-2 mEq/kg IV bolus for:
    • QRS duration >100 ms
    • Ventricular arrhythmias
    • Hypotension unresponsive to fluids
    • Metabolic acidosis
  • Repeat doses as needed to maintain arterial pH 7.45-7.55 1
  • Mechanism: Sodium loading and serum alkalinization have additive effects in reversing sodium channel blockade 1

Fluid Resuscitation

• For hypotension, administer 5-10 mL/kg boluses of normal saline 1
• If hypotension persists, epinephrine and norepinephrine are more effective than dopamine 1

Second-Line Treatments

• For Refractory Cases
  • Consider extracorporeal life support (ECMO) for cardiac arrest or refractory shock due to TCA toxicity 1
  • Avoid Class IA (quinidine, procainamide), Class IC (flecainide, propafenone), or Class III (amiodarone, sotalol) antiarrhythmics, which may worsen cardiac toxicity 1

Management of Other Complications

Seizures

• Administer benzodiazepines (diazepam or midazolam) as first-line therapy 3
• If seizures persist, consider phenobarbital
• For refractory seizures, muscular paralysis and mechanical ventilation may be necessary 3

Hyperthermia

• Aggressive cooling measures for temperature >39°C
• Avoid medications that may worsen anticholinergic effects

Monitoring and Disposition

• Continuous cardiac monitoring for at least 6 hours after ingestion
• Extended monitoring (24 hours) for patients with:
  • QRS >100 ms at any time
  • Arrhythmias
  • Altered mental status
  • Signs of significant toxicity

Common Pitfalls to Avoid

• Delayed recognition of cardiotoxicity: QRS prolongation may precede clinical deterioration
• Inadequate sodium bicarbonate dosing: Don't hesitate to give repeated doses to maintain alkalemia
• Premature discontinuation of monitoring: Toxicity can be delayed or recurrent
• Using contraindicated antiarrhythmics: Class IA, IC, and III agents can worsen sodium channel blockade
• Overlooking mixed overdoses: TCAs are often ingested with other substances that may require specific treatments

Special Considerations

• TCAs have anticholinergic, quinidine-like, alpha-adrenergic blocking, and CNS depressant properties 2
• The terminal 40 ms right axis deviation in lead aVR is a sensitive marker for TCA toxicity 1
• Physostigmine is no longer routinely recommended due to risk of seizures and asystole 3, 4
• Lipid emulsion therapy may be considered in refractory cases, though evidence is limited 1

By following this algorithm and prioritizing sodium bicarbonate therapy for cardiotoxicity, mortality from TCA overdose can be significantly reduced.