False Positive Drug Test Results with Bupropion and Amphetamine
Bupropion is known to cause false positive urine drug screens for both amphetamine and methamphetamine, and confirmatory testing should be used to verify actual medication use in patients prescribed both medications.
Why False Positives Occur
- Bupropion (Wellbutrin) is the most frequent cause of false positive urine drug screens for amphetamines, with studies showing 41% of false positive amphetamine results were associated with bupropion use 1
- Standard immunoassay screening tests lack specificity and cannot reliably distinguish between prescribed medications and illicit substances 2
- The chemical structure of bupropion and its metabolites can cross-react with antibodies used in immunoassay tests for amphetamines and methamphetamines 3
Recommended Approach for Patients on Both Medications
Step 1: Understand the Testing Process
- Initial positive screening tests should always be considered preliminary until confirmed with more specific testing 4
- Inform the laboratory about all prescribed medications before testing to help with interpretation 4
Step 2: Request Confirmatory Testing
- Gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS) should be used to confirm positive screening results 1, 3
- These confirmatory tests can distinguish between bupropion and actual amphetamine compounds 2
Step 3: Provide Documentation
- Patients should carry documentation of their prescribed medications, including bupropion XL and amphetamine salt combination 4
- A letter from the prescribing physician explaining the expected test results may help prevent misunderstandings 4
Important Clinical Considerations
- False positive results can have serious consequences for patients, including inappropriate treatment decisions or legal implications 2
- Bupropion is sometimes used as an alternative to stimulants for ADHD treatment, particularly during pregnancy when there are concerns about stimulant use 4
- Bupropion has shown efficacy in reducing methamphetamine cravings and subjective effects, which may be beneficial in patients with history of substance use 5
Common Pitfalls to Avoid
- Never make clinical decisions based solely on immunoassay screening results without confirmation 4
- Do not assume a positive test means illicit drug use when a patient is taking prescribed medications known to cause false positives 2
- Avoid discontinuing necessary medications based on unconfirmed drug test results 4
Documentation Best Practices
- Document all prescribed medications in the patient's chart 4
- Record the specific type of drug test used and whether confirmatory testing was performed 4
- Note any discrepancies between patient-reported medication use and test results after confirmation 4
Remember that proper interpretation of drug test results requires understanding the limitations of the testing methodology and consideration of all medications the patient is taking 2.