Laboratory Testing for Wellbutrin (Bupropion) Overdose
In bupropion overdose, obtain basic metabolic panel (including electrolytes with particular attention to potassium), ECG, and consider urine drug screen—though be aware that bupropion metabolites cause false-positive amphetamine results on immunoassay testing.
Essential Laboratory Tests
Electrolytes and Metabolic Panel
- Serum potassium is critical: Hypokalemia has been documented in bupropion overdose, with levels ranging from 2.6-4.2 mEq/L (mean 3.3 mEq/L) in reported cases 1
- Complete metabolic panel including:
- Serum electrolytes (sodium, potassium, chloride, bicarbonate)
- Blood urea nitrogen (BUN) and creatinine
- Glucose
Cardiac Monitoring
- 12-lead ECG on admission is recommended for all bupropion overdoses 2
- Monitor for:
- QRS widening
- QTc prolongation
- Conduction delays
- Tachycardia (most common cardiovascular finding)
- Continuous cardiac monitoring for patients with significant ingestions, as conduction abnormalities may develop over 2-4 days 2
Additional Laboratory Considerations
Creatine kinase (CK): Consider if seizures occur, to assess for rhabdomyolysis—a potential complication of prolonged seizure activity
Liver function tests: May be warranted in severe cases, though hepatotoxicity is not a primary concern in acute overdose
Arterial blood gas: If respiratory depression or metabolic acidosis is suspected, particularly in severe cases with seizures
Important Caveats About Drug Screening
False-Positive Amphetamine Results
Bupropion metabolites cross-react with amphetamine immunoassays, causing false-positive results 3, 4, 5:
- This occurs with concentrations of bupropion metabolites >500 ng/mL 4
- False positives can persist even after discontinuation of bupropion 3
- Confirmatory testing with gas chromatography/mass spectrometry (GC/MS) is required to distinguish bupropion from true amphetamines 3, 4, 5
- In one study, 41% of patients with false-positive amphetamine screens were taking bupropion 5
Quantitative Bupropion Levels
- Serum bupropion and metabolite levels are not routinely available or clinically useful for acute management
- Results typically return after clinical decisions have been made 6
- Levels do not reliably predict severity or duration of toxicity
- The active metabolite hydroxybupropion is more stable than bupropion itself, but measurement is not standard of care in overdose 7
Clinical Context
The primary toxicities of bupropion overdose are neurological (seizures, tremors, lethargy, agitation) rather than cardiovascular 1. However, ECG monitoring remains essential as conduction delays can occur, particularly in massive ingestions 2.
Seizures are the most concerning complication and may be refractory to treatment. Both benzodiazepines and phenytoin have been effective in controlling bupropion-induced seizures 1.
Bupropion toxicity can mimic alcohol withdrawal syndrome with agitation, hallucinations, tremors, and autonomic instability 6, making the clinical history and comprehensive laboratory evaluation particularly important when the ingestion history is unclear.