What is the dose of bicarbonate (sodium bicarbonate) for treating bupropion (Wellbutrin) toxicity?

Sodium Bicarbonate Dosing for Bupropion Toxicity

The recommended initial dose of sodium bicarbonate for bupropion toxicity with life-threatening cardiotoxicity is 1-2 mEq/kg IV bolus, which can be repeated as needed to achieve clinical stability while avoiding extreme hypernatremia or alkalemia. 1

Mechanism and Indications

Bupropion toxicity can cause:

• QRS prolongation
• Seizures
• Ventricular dysrhythmias
• Cardiovascular collapse

Unlike tricyclic antidepressants (TCAs), bupropion's cardiotoxicity primarily results from inhibition of cardiac gap junctions rather than pure sodium channel blockade 2, 3. This distinction is important because:

• Sodium bicarbonate is highly effective for TCA toxicity
• Bupropion-induced QRS widening often shows limited response to sodium bicarbonate 2, 4

Administration Protocol

1. Initial dose: 1-2 mEq/kg IV bolus of hypertonic (8.4%, 1 mEq/mL) sodium bicarbonate 1
2. Subsequent dosing: Repeat as needed based on clinical response
3. Maximum dose: Do not exceed 6 mEq/kg total to avoid hypernatremia, fluid overload, and cerebral edema 3
4. Administration strategy:
   • Combine with hyperventilation (target PCO₂ ~30-35 mmHg) for optimal alkalinization 3
   • Target serum pH ~7.45-7.55 rather than normalizing QRS duration 3

Monitoring During Treatment

• ECG (QRS duration, QTc interval)
• Arterial blood gases
• Serum electrolytes (particularly potassium and calcium)
• Blood pressure and heart rate
• Mental status 5

Important Caveats and Pitfalls

• Limited efficacy: Recent evidence suggests sodium bicarbonate may not significantly decrease QRS duration in bupropion overdose 2
• Response assessment: If no improvement after initial bolus, consider alternative treatments 3
• Electrolyte disturbances: Monitor for hypocalcemia and hypokalemia which can worsen QTc prolongation 3
• Avoid excessive dosing: Don't continue dosing until QRS <100ms; this approach often leads to sodium bicarbonate overdose 3
• Consider ECMO: For refractory cardiogenic shock from bupropion toxicity unresponsive to sodium bicarbonate 1, 6

Special Considerations

• Bupropion toxicity may present with atypical features including delayed cardiac decompensation 6
• Resolution of tachycardia is typically prognostic of recovery but can sometimes represent worsening cardiotoxicity 6
• Misidentifying the rhythm as pure ventricular tachycardia may lead to administration of medications like amiodarone that can worsen QTc prolongation and sodium channel blockade 7

While sodium bicarbonate remains first-line therapy for sodium channel blocker toxicity including bupropion, clinicians should be prepared to escalate to mechanical support such as VA-ECMO if the patient shows limited response to sodium bicarbonate or develops refractory cardiogenic shock.