What if a confirmation test still shows the presence of methamphetamine in a patient taking bupropion (Wellbutrin) XL and amphetamine (Adderall) salt combination?

Managing False Positive Methamphetamine Results in Patients on Bupropion and Amphetamine Medications

If a confirmation test still shows methamphetamine in a patient taking bupropion (Wellbutrin) XL and amphetamine (Adderall) salt combination, this likely represents a true positive from the amphetamine medication, not a false positive from bupropion.

Understanding Drug Testing and False Positives

• Bupropion (Wellbutrin) is a common cause of false positive results for amphetamines on initial immunoassay screening tests, with one study showing it was responsible for 41% of false positive amphetamine screens 1
• However, confirmatory testing using gas chromatography/mass spectrometry (GC/MS) should be able to differentiate between true methamphetamine use and false positives caused by bupropion 1, 2
• Amphetamine salt combinations (Adderall) contain mixed amphetamine salts that will produce true positive results for amphetamines on both screening and confirmation tests 3

Interpreting Confirmation Test Results

• If a confirmation test specifically shows methamphetamine (not just amphetamines):

  • This is unlikely to be caused by bupropion, as bupropion causes false positives only on initial screening tests, not on confirmation tests 1
  • This is also unlikely to be caused by prescribed Adderall, which contains amphetamine but not methamphetamine 3
  • The most likely explanation is either methamphetamine use or another medication causing a false positive on the confirmation test 3

• Possible explanations for confirmed methamphetamine:

  • Actual methamphetamine use (most likely if confirmation test is positive) 3
  • Metabolism of certain medications to methamphetamine (rare) 2
  • Laboratory error in the confirmation testing process 3

Clinical Approach to Positive Confirmation Tests

• Discuss the unexpected results with the patient in a non-judgmental manner, as recommended by clinical guidelines 3
• Ask about use of any other prescription medications, over-the-counter products, or supplements that might explain the result 3
• Consider consulting with the laboratory toxicologist about the specific testing methodology used and potential cross-reactivity 3
• Document the discussion and clinical decision-making process carefully 3

Important Considerations

• Do not dismiss patients from care based solely on unexpected drug test results, as this could constitute patient abandonment 3
• Unexpected results should be used to improve patient safety and treatment planning, not as punitive measures 3
• Consider the possibility of laboratory error and request retesting if clinically indicated 3
• Remember that the goal of drug testing is to improve patient care and safety, not to "catch" patients 3

Pharmacological Interactions

• Bupropion actually reduces methamphetamine clearance and may reduce some of its subjective effects 4, 5
• Bupropion has been studied as a potential treatment for methamphetamine dependence due to its dopaminergic effects 4
• Co-administration of bupropion and methamphetamine has not shown evidence of additive cardiovascular effects in research settings 5

Clinical Decision Making

• If confirmation testing repeatedly shows methamphetamine in a patient prescribed only bupropion and amphetamine salts, consider:
  • Requesting a different confirmation method or laboratory 3
  • Evaluating for potential substance use disorder 3
  • Discussing the results openly with the patient to understand potential explanations 3
  • Implementing more frequent monitoring if clinically indicated 3