Wellbutrin (Bupropion) Can Cause False Positive Urine Drug Screens for Amphetamines
Bupropion hydrochloride extended-release tablets (Wellbutrin) can cause false-positive urine test results for amphetamines, as explicitly stated in the FDA drug label. 1
Mechanism and Frequency of False Positives
Bupropion is a commonly prescribed antidepressant that appears to be the most frequent cause of false positive urine drug screens for amphetamines in some populations:
- Studies show that 41% of false positive amphetamine screens were associated with bupropion use 2
- The false positive result occurs with certain immunoassay tests, particularly:
Detection Thresholds and Metabolites
- False positive results typically occur when bupropion metabolites are present in concentrations greater than 500 ng/mL 3
- It's primarily the metabolites of bupropion, rather than the parent drug itself, that cross-react with the amphetamine screening tests 3
Confirmatory Testing
When a positive amphetamine screen occurs in a patient taking Wellbutrin:
- Confirmatory testing using gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) is essential 5
- These confirmatory methods can differentiate between true amphetamine use and bupropion-induced false positives 6
- Without confirmation, patients may face unwarranted consequences, including potential legal or employment issues
Clinical Implications and Best Practices
Documentation is crucial: Always document any medications the patient is taking, including Wellbutrin/bupropion, to help interpret drug screen results 5
Patient communication: Discuss unexpected positive results with patients rather than taking immediate punitive action 5
Laboratory collaboration: Establish a working relationship with laboratory toxicologists to assist with result interpretation 5
Awareness of other medications: Be aware that other commonly prescribed medications can also cause false positives on urine drug screens, including:
Common Pitfalls to Avoid
- Failing to order confirmatory testing when a patient on bupropion tests positive for amphetamines
- Not informing patients taking Wellbutrin about the possibility of false positive drug screens
- Dismissing patients from care based solely on unconfirmed positive urine drug test results 5
- Assuming that all drug screening methods have the same cross-reactivity with bupropion
By understanding that Wellbutrin can cause false positive amphetamine results and following appropriate confirmatory testing protocols, clinicians can avoid misinterpretation of drug screening results and prevent potential harm to patients.