In an adult who has ingested a bupropion overdose (≥2–3 g), what conduction abnormality should be monitored and what is the first‑line treatment?

Bupropion Overdose: Conduction Abnormalities and Management

In bupropion overdose (≥2-3 g), monitor for QRS prolongation and wide-complex tachycardia, but recognize that sodium bicarbonate is likely ineffective for bupropion-induced cardiotoxicity—instead, provide aggressive supportive care with readiness for extracorporeal membrane oxygenation (ECMO) in refractory cases.

Key Conduction Abnormality to Monitor

QRS prolongation is the primary conduction abnormality in bupropion overdose 1. The FDA label specifically notes "ECG changes such as conduction disturbances or arrhythmias" in overdose cases 1. However, bupropion's mechanism differs critically from typical sodium channel blockers:

• Bupropion blocks cardiac gap junctions (Connexin 43) rather than sodium channels directly 2, 3
• This produces QRS widening, QTc prolongation, and terminal R waves 3
• Wide-complex tachycardia can develop 4
• Sinus tachycardia is common initially, though tachycardia resolution does NOT guarantee recovery 5

Critical Monitoring Points:

• Continuous cardiac monitoring for QRS duration
• Serial ECGs to track QRS changes (can worsen up to 16 hours post-ingestion) 5
• Monitor for ventricular dysrhythmias
• Delayed cardiac decompensation can occur >30 hours after ingestion 5

First-Line Treatment: The Sodium Bicarbonate Controversy

Sodium bicarbonate should NOT be considered first-line therapy for bupropion overdose, despite its effectiveness in other sodium channel blocker poisonings. Here's why:

Evidence Against Sodium Bicarbonate in Bupropion:

The 2023 AHA guidelines recommend sodium bicarbonate for sodium channel blocker poisoning 6, but bupropion is mechanistically different. Recent high-quality evidence demonstrates:

• No significant QRS narrowing with sodium bicarbonate in bupropion overdose (median change -2.0 ms, p=0.42) 2
• No association between bicarbonate dosing and QRS improvement 2
• Multiple case reports of unresponsiveness to bicarbonate therapy 7, 5
• The gap junction blockade mechanism explains why alkalinization fails 2, 8

When Bicarbonate Might Be Considered:

One case report showed response to bicarbonate in wide-complex tachycardia 4, suggesting a trial dose may be reasonable if:

• Life-threatening ventricular dysrhythmia is present
• QRS >120 ms with hemodynamic instability
• Use 1-2 mmol/kg bolus as a therapeutic trial 8

However, do not delay definitive supportive care waiting for bicarbonate response.

Recommended Management Algorithm

1. Immediate Supportive Care (Priority)

• Airway management and intubation if altered mental status
• Seizure prophylaxis/treatment with benzodiazepines (seizures occur in ~33% of cases) 1
• Continuous cardiac monitoring
• IV access and fluid resuscitation

2. Cardiovascular Support

• Vasopressors for hypotension (norepinephrine preferred based on sodium channel blocker data) 6
• Correct electrolyte abnormalities (hypokalemia, hypocalcemia can worsen QTc)
• Avoid antiarrhythmics like amiodarone that prolong QTc 4

3. Consider ECMO Early

ECMO is the definitive rescue therapy for bupropion-induced cardiogenic shock 5:

• Successful case reports with full neurologic recovery 5
• Should be considered for refractory shock or cardiac arrest
• The 2023 AHA guidelines support ECMO for sodium channel blocker poisoning refractory to other treatments 6
• Don't wait too long—arrange transfer to ECMO-capable center early if deteriorating

4. Prolonged Monitoring

• Minimum 24 hours cardiac monitoring for all significant ingestions
• Extend to 48+ hours if QRS prolongation or delayed presentation 5
• Cardiac decompensation can be delayed beyond typical timeframes

Common Pitfalls to Avoid

1. Assuming tachycardia resolution means recovery—cardiac collapse can occur hours later 5
2. Over-relying on sodium bicarbonate—it likely won't work and delays definitive care 2, 8
3. Administering excessive bicarbonate doses (>6 mmol/kg) causing hypernatremia and cerebral edema 8
4. Mistaking wide-complex rhythm for pure VT and giving amiodarone, which worsens toxicity 4
5. Premature discontinuation of monitoring—observe for at least 24-48 hours 5
6. Missing coingestions (particularly olanzapine) that can alter presentation 5

Additional Considerations

• No specific antidote exists 1
• Seizures occur in approximately one-third of cases and require aggressive benzodiazepine therapy 1
• Deaths have been reported with ingestions of large doses, with multiple uncontrolled seizures and cardiac arrest 1
• Bupropion is increasingly common as a cause of drug-induced QRS prolongation, now rivaling tricyclic antidepressants 9

The key is recognizing that bupropion cardiotoxicity requires a different approach than traditional sodium channel blockers—focus on aggressive supportive care and early ECMO consideration rather than relying on sodium bicarbonate.