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

Management of Trimipramine Overdose

Sodium bicarbonate administration is the cornerstone of treatment for trimipramine overdose, with a recommended dose of 1-2 mEq/kg IV for QRS prolongation >100 ms. 1

Initial Assessment and Stabilization

• Airway management:

  • Secure airway immediately if consciousness is impaired
  • Provide supplemental oxygen and ventilatory support as needed
  • Consider early endotracheal intubation in patients with severe CNS depression 2

• Cardiac monitoring:

  • Obtain ECG immediately and initiate continuous cardiac monitoring
  • QRS duration ≥100 ms indicates increased risk of seizures
  • QRS duration ≥160 ms indicates increased risk of ventricular dysrhythmias 2, 3

• IV access:

  • Establish intravenous line for medication administration
  • Maintain adequate fluid resuscitation for hypotension management

Gastrointestinal Decontamination

• Gastric lavage:

  • Perform large volume gastric lavage if patient presents within 1-2 hours of ingestion
  • Secure airway prior to lavage if consciousness is impaired

• Activated charcoal:

  • Administer 30-50g orally or via nasogastric tube
  • May add sorbitol 0.5g/kg or 30g magnesium sulfate as a cathartic
  • Emesis is contraindicated 2, 3

Cardiovascular Management

• Sodium bicarbonate therapy:

  • Administer for QRS duration ≥100 ms or terminal right-axis deviation >120 degrees
  • Initial dose: 1-2 mEq/kg IV bolus
  • Goal: maintain serum pH between 7.45-7.55
  • May repeat as needed based on ECG monitoring and pH 1, 2, 3

• Management of dysrhythmias:

  • For dysrhythmias unresponsive to sodium bicarbonate:
    • Consider lidocaine, bretylium, or phenytoin
    • Avoid Type 1A and 1C antiarrhythmics (quinidine, disopyramide, procainamide) 2

• Hypotension management:

  • Administer IV fluids for initial management
  • Consider vasopressors if hypotension persists despite fluid resuscitation and sodium bicarbonate

Seizure Management

• First-line treatment:

  • Benzodiazepines (e.g., diazepam, lorazepam) for seizure control

• Second-line treatment:

  • If benzodiazepines are ineffective, consider phenobarbital or phenytoin
  • Physostigmine is not recommended except for life-threatening symptoms unresponsive to other therapies, and only in consultation with poison control 2

Monitoring and Follow-up

• Minimum monitoring period:

  • At least 6 hours of cardiac monitoring and observation
  • Extended monitoring if signs of toxicity occur during this period
  • Be aware that fatal dysrhythmias can occur late after overdose 2

• Psychiatric evaluation:

  • Arrange psychiatric consultation once medically stable
  • Consider suicide risk assessment and appropriate follow-up 2

Special Considerations

• Avoid certain medications:

  • Type 1A and 1C antiarrhythmics are contraindicated
  • Use caution with neuromuscular blockers in patients with mixed overdoses 1

• Hemodialysis:

  • Generally ineffective for tricyclic antidepressant poisoning
  • Consider hemoperfusion only in cases of acute refractory cardiovascular instability 2

Pitfalls and Caveats

• Plasma drug levels may not reflect poisoning severity and should not guide management alone
• Deaths from tricyclic overdose can occur despite seemingly adequate initial stabilization
• Patients may appear to improve clinically but deteriorate rapidly later
• QRS interval prolongation is a better predictor of complications than serum drug levels 3
• Tricyclic antidepressant overdose is the most common cause of death from prescription drugs 4
• Patients with mixed overdoses (especially with other cardiotoxic drugs) may have unpredictable responses to treatment

By following this structured approach with early sodium bicarbonate administration for QRS prolongation, aggressive supportive care, and careful monitoring, mortality and morbidity from trimipramine overdose can be significantly reduced.