Why does Adderall (amphetamine and dextroamphetamine) show up on a drug screen for amphetamine (AMP500) and methamphetamine (MET500)?

Why Adderall Shows Up on Drug Screens for AMP500 and MET500

Adderall shows up positive on drug screens for amphetamines (AMP500) because it contains amphetamine salts, and may cross-react with methamphetamine (MET500) tests due to structural similarities and metabolic pathways. 1

Chemical Composition of Adderall

• Adderall contains a mixture of amphetamine salts in a 3:1 ratio of d-enantiomer to l-enantiomer amphetamine 2, 3
• This specific mixture of amphetamine salts is directly detected by amphetamine immunoassay screens (AMP500) 4
• The presence of both d-enantiomer and l-enantiomer in Adderall creates a distinctive excretion profile that differs from single-enantiomer formulations like Dexedrine 2

Drug Testing Detection Mechanisms

• Standard immunoassay drug screens detect amphetamine and its metabolites through antibody binding to specific molecular structures 1
• Amphetamine and methamphetamine have similar chemical structures, which can lead to cross-reactivity in immunoassay testing 4
• Initial positive screening tests (immunoassays) are less specific than confirmatory tests like gas chromatography-mass spectrometry (GC/MS) 4

Why Adderall May Trigger Both AMP500 and MET500 Positives

• The structural similarity between amphetamine and methamphetamine can cause cross-reactivity in methamphetamine immunoassay screens 1
• Metabolic pathways for amphetamines may produce compounds that cross-react with methamphetamine testing panels 2
• The enantiomer composition changes over time after dosing, with the proportion of l-enantiomer increasing, which can affect cross-reactivity patterns 3

Timing and Detection Windows

• Peak amphetamine concentrations after a single 20mg dose of Adderall range from 2,645 to 5,948 ng/mL 2
• With repeated daily dosing (20mg), peak concentrations can reach 5,739 to 19,172 ng/mL 3
• Amphetamine can be detected above the standard 500 ng/mL cutoff for up to 47.5 hours after a single dose and up to 60 hours after the last dose in a multiple-dose regimen 2, 3

False Positive Considerations

• Certain medications can cause false-positive results for amphetamines on immunoassay screens 4
• Over-the-counter cold medications containing pseudoephedrine can trigger false-positive amphetamine results 4
• Other medications reported to cause false-positive amphetamine results include aripiprazole 5, atomoxetine 6, and metoprolol 7
• Confirmatory testing with GC/MS is highly specific and can distinguish between prescribed Adderall use and other substances 1

Clinical Implications

• When interpreting drug test results, clinicians should consider the patient's complete medication history, including prescribed medications like Adderall 4
• Drug testing cannot distinguish between appropriate use and misuse of prescribed medications like Adderall 4
• The presence of both d- and l-enantiomers in specific ratios can help differentiate prescribed Adderall use from some forms of illicit amphetamine use 3

Important Caveats

• Not all samples containing ≥500 ng/mL of amphetamine will test positive on immunoassay due to differing cross-reactivity of the enantiomers 3
• Urine pH and hydration status can significantly affect drug concentration and detection window 2
• When unexpected results occur, clinicians should consider confirmatory testing before making clinical decisions 1
• Establishing a relationship with laboratory toxicologists can help with proper interpretation of complex drug test results 1