Will a patient with a history of substance use, taking Vyvanse (lisdexamfetamine) or Strattera (atomoxetine), test positive for methamphetamine use?

Will Vyvanse or Strattera Cause a Positive Methamphetamine Test?

Vyvanse (lisdexamfetamine) will cause a positive amphetamine test but should NOT produce a positive methamphetamine result on confirmatory testing, while Strattera (atomoxetine) will NOT cause a positive result for either amphetamine or methamphetamine. 1, 2

Understanding Vyvanse (Lisdexamfetamine) and Drug Testing

Vyvanse is a prodrug that metabolizes to dextroamphetamine, meaning it will produce a positive result on amphetamine immunoassay screening tests. 3 However, the critical distinction is:

• Screening immunoassays (initial urine drug screens) will show positive for amphetamines when taking Vyvanse 1, 2
• Confirmatory GC-MS testing can differentiate between prescribed amphetamine and illicit methamphetamine by identifying specific enantiomer composition 1
• Lisdexamfetamine is metabolized by erythrocyte cells to dextroamphetamine after ingestion, which is why it appears on amphetamine panels 4

Key Clinical Pitfall to Avoid

Many immunoassay screening tests have cross-reactivity issues and false-positive rates of 3.9-9.9% for amphetamine screens. 2 This means:

• A positive "methamphetamine" result on an initial screening test in a patient taking Vyvanse may be a false-positive due to cross-reactivity 5
• Never make consequential decisions based solely on immunoassay results without confirmatory GC-MS testing 1, 2
• Confirmatory testing will distinguish prescribed dextroamphetamine (from Vyvanse) from illicit methamphetamine 1

Understanding Strattera (Atomoxetine) and Drug Testing

Atomoxetine is a selective norepinephrine reuptake inhibitor that is NOT a stimulant and will NOT cause positive results on amphetamine or methamphetamine drug screens. 6

• Atomoxetine has high selectivity for norepinephrine transporters with little affinity for other neurotransmitter receptors 6
• It is specifically recommended for patients at risk of substance abuse precisely because it has negligible abuse potential and is not a controlled substance 4, 6
• The mechanism of action is completely different from amphetamines, so there is no cross-reactivity on drug testing 6

Essential Clinical Approach When Interpreting Results

Before interpreting any drug test result, you must obtain a complete medication history including all prescription medications, over-the-counter drugs, and supplements. 1, 2 Specifically:

• Ask specifically about ADHD medications including amphetamine salts, lisdexamfetamine, and atomoxetine 1
• Note that methylphenidate (Ritalin, Concerta) is NOT detected on routine amphetamine panels, so cannot explain positive results 1, 7
• Pseudoephedrine in over-the-counter cold medications can cause false-positive amphetamine/methamphetamine results 1, 2

When Confirmatory Testing is Mandatory

Request GC-MS confirmatory testing when: 1, 2

• Results are unexpected based on the clinical history
• The patient denies illicit drug use and is prescribed Vyvanse
• Results will impact patient management, legal decisions, or treatment program participation
• There is a discrepancy between screening results and clinical presentation

Critical Warning About Interpretation Errors

Many healthcare providers have inadequate training in interpreting urine drug test results, and incorrect interpretation can have severe consequences including loss of child custody or legal implications. 1, 2 Therefore:

• Establish a working relationship with your local toxicologist for consultation on complex results 1, 2
• Discuss unexpected positive results with laboratory personnel before making clinical decisions 1, 2
• Understand your specific testing panel's limitations, as standard panels have varying sensitivities 1

Detection Timeline Considerations

If you need to verify abstinence from methamphetamine in a patient taking Vyvanse:

• Methamphetamine is detectable in urine for 2-4 days after use, with initial detection within 1-4 hours 7, 2
• The 2-4 day detection window means negative results only indicate no use in the past several days, not overall abstinence 7, 2
• Consider alternative matrices: oral fluid detects use within 24-48 hours, while hair testing detects historical use over 90 days but cannot detect use within the previous 7-10 days 7, 2