Which medications can cause false positive results for amphetamines on urine drug tests, including antidepressants like bupropion, antacids like ranitidine, and cold medications?

From the Guidelines

Several medications, including bupropion, ranitidine, and cold medications containing pseudoephedrine, can cause false positive results for amphetamines on urine drug tests. These medications have chemical structures similar to amphetamines, which can trigger false positives on immunoassay screening tests 1. Common culprits include:

• Bupropion (Wellbutrin), an antidepressant with a chemical structure similar to amphetamines
• Ranitidine (Zantac), an antacid and H2 blocker that can trigger false positives
• Cold medications containing pseudoephedrine, phenylephrine, or ephedrine, which are structurally related to amphetamines Other medications that may lead to false positives include:
• Certain antipsychotics like chlorpromazine and promethazine
• The antibiotic rifampin
• The Parkinson's medication selegiline
• The weight loss drug phentermine
• The ADHD medication atomoxetine (Strattera) It is essential to inform the testing facility beforehand if you're taking any of these medications and need to undergo drug testing, as confirmatory testing using more specific methods like gas chromatography-mass spectrometry may be necessary to distinguish between true amphetamines and similar compounds 1.

From the FDA Drug Label

False-positive urine immunoassay screening tests for amphetamines have been reported in patients taking bupropion. This is due to lack of specificity of some screening tests. False-positive test results may result even following discontinuation of bupropion therapy Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish bupropion from amphetamines.

• Bupropion can cause false positive results for amphetamines on urine drug tests 2.
• The false-positive results are due to the lack of specificity of some screening tests.
• Confirmatory tests, such as gas chromatography/mass spectrometry, can distinguish bupropion from amphetamines.

From the Research

Medications Causing False Positive Amphetamine Results

The following medications can cause false positive results for amphetamines on urine drug tests:

• Antidepressants:
  • Bupropion 3
  • Atomoxetine 4
  • Sertraline 5
  • Venlafaxine 5
  • Trazodone 5
• Antipsychotics:
  • Aripiprazole 6
  • Quetiapine 5
  • Chlorpromazine 5
  • Thioridazine 5
• Antihistamines:
  • Brompheniramine 5
  • Diphenhydramine 5
  • Doxylamine 5
  • Promethazine 5
• Analgesics:
  • Ibuprofen 5
  • Naproxen 5
• Antibiotics:
  • Quinolones (ofloxacin and gatifloxacin) 5
• Non-prescription agents:
  • Ranitidine 5
  • Dextromethorphan 5
  • Non-prescription nasal inhaler 5
• Other medications:
  • Labetalol 7
  • Fenofibrate 7
  • Metformin 7

Mechanism of False Positive Results

False positive results for amphetamines are often caused by cross-reactivity with other substances in immunoassay urine drug screens 5, 7. Confirmatory testing with gas chromatography-mass spectrometry (GC-MS) or mass spectrometry (MS) can help to rule out false positive results 6, 4, 7.

Clinical Implications

False positive results for amphetamines can have significant clinical implications, including unnecessary treatment and monitoring of patients, impairment of physician-patient relationship, and legal implications 6, 7. Therefore, it is essential to be aware of the medications that can cause false positive results and to use confirmatory testing when necessary.