From the Guidelines
Certain medications and substances can cause false positives for methamphetamine in a urine drug screen.
Common Causes of False Positives
- Pseudoephedrine, found in over-the-counter cold medications, can cause false-positive screening results for amphetamines, including methamphetamine 1.
- Prescription medications, such as amphetamine and dextroamphetamine, used to treat attention-deficit/hyperactivity disorder, can also lead to false-positive results for amphetamines 1.
Importance of Medical History and Test Interpretation
It is essential to consider an individual's complete medical history, including prescribed medications, to accurately interpret drug test results 1.
Limitations of Drug Testing
Drug testing cannot distinguish between appropriate use and misuse of prescribed medications, highlighting the need for careful interpretation of test results in the context of a patient's medical history 1.
From the Research
Medications Causing False Positives for Methamphetamine
- The following medications have been reported to cause false-positive results for methamphetamine in urine drug screens:
- Antihistamines: brompheniramine, diphenhydramine, doxylamine 2
- Antidepressants: bupropion, clomipramine, sertraline, trazodone, venlafaxine 2
- Antibiotics: quinolones (ofloxacin and gatifloxacin) 2
- Analgesics: ibuprofen, naproxen 2
- Antipsychotics: chlorpromazine, quetiapine, thioridazine 2
- Beta-blockers: metoprolol 3
- Antipsychotics: aripiprazole 4
- Anti-arrhythmics: mexiletine 5
Mechanism of False Positives
- False-positive results are often caused by cross-reactivity between the medication and the immunoassay used in the urine drug screen 2, 3, 6
- Cross-reactivity can occur with both the parent drug and its metabolites 3