Can Seroquel (quetiapine) cause false positive results on drug screens?

Can Seroquel Cause False Positive Drug Screen Results?

Yes, quetiapine (Seroquel) can cause false positive results on drug screens, particularly for tricyclic antidepressants (TCAs) due to structural similarities between these compounds. 1, 2, 3

Evidence for False Positive Results

Quetiapine has been documented to cross-react with several immunoassay-based drug screening tests:

• The FDA drug label for quetiapine specifically warns: "There have been literature reports suggesting false positive results in urine enzyme immunoassays for methadone and tricyclic antidepressants in patients who have taken quetiapine." 1

• Multiple studies have confirmed that quetiapine can cause false-positive TCA immunoassay results in both therapeutic use and overdose scenarios. 2, 3

• In laboratory testing, quetiapine has shown concentration-dependent cross-reactivity with TCA immunoassays, with positive results appearing at various concentrations depending on the specific assay used. 3

Mechanism of False Positives

The false positive results occur because:

1. Quetiapine has structural similarities to tricyclic antidepressants
2. Preliminary screening immunoassays have limited specificity
3. Cross-reactivity occurs with the antibodies used in these screening tests

Clinical Implications

When to Suspect a False Positive

• Patient taking quetiapine tests positive for TCAs without TCA use
• Unexpected positive test for methadone in a patient on quetiapine
• Discrepancy between patient's reported medication use and drug screen results

How to Confirm Results

• Preliminary screening tests should always be confirmed with more specific methods 4
• Confirmatory testing should be done using gas chromatography-mass spectrometry (GC-MS), which can distinguish between quetiapine and other substances 5
• Always obtain a complete medication history before interpreting drug test results 4

Recommendations for Clinicians

1. Always collect a thorough medication history before interpreting drug screen results, specifically asking about quetiapine use
2. Inform laboratory personnel about quetiapine use when ordering drug screens
3. Request confirmatory testing when results are unexpected or don't match clinical presentation
4. Document in patient records that quetiapine may cause false positive results for TCAs and methadone
5. Educate patients taking quetiapine that they may test falsely positive on certain drug screens

Important Considerations

• Different immunoassay products have varying cross-reactivity with quetiapine 2
• False positives can have serious consequences including inappropriate treatment, legal implications, or loss of child custody in some states 4
• The risk of false positives is higher with preliminary screening tests compared to confirmatory tests 4
• Other medications can also cause false positive results, including certain antidepressants, antihistamines, and antibiotics 5

Remember that a negative drug test doesn't necessarily rule out substance use, as timing of use, test cutoff levels, and test panel limitations can all affect results 4.