Can trazodone cause a false-positive result on a urine immunoassay for fentanyl?

Can Trazodone Cause a False-Positive Urine Test for Fentanyl?

Yes, trazodone is a well-documented cause of false-positive results on fentanyl immunoassay urine drug screens and should be considered a major interferent when interpreting positive fentanyl screening results.

The Evidence

The most recent and highest-quality study directly addressing this question found that trazodone was identified as one of the three major interferents causing false-positive fentanyl immunoassay results, accounting for a substantial portion of false positives 1. In this 2024 clinical evaluation of the FDA-cleared SEFRIA fentanyl immunoassay examining nearly 15,000 screening results, trazodone (along with labetalol and haloperidol) was responsible for 56% of false-positive results even after cutoff optimization 1.

Clinical Implications

When You See a Positive Fentanyl Screen:

• Always obtain a complete medication history before interpreting the result, specifically asking about trazodone use 2
• Recognize that screening immunoassays are susceptible to cross-reactivity with unrelated substances in urine, making false positives more likely than with confirmatory testing 2
• Order confirmatory testing with LC-MS/MS for any positive fentanyl immunoassay, as this is the gold standard and will definitively distinguish true fentanyl use from trazodone interference 1, 3

Understanding the Testing Limitations:

The initial false-positive rate in the 2024 study was 38% using the FDA-cleared cutoff, which improved to 17% with cutoff optimization, but trazodone remained a persistent interferent 1. This means that even with optimized testing parameters, trazodone can still trigger false positives.

Critical Pitfalls to Avoid

1. Never make clinical decisions based solely on screening immunoassay results when the patient is taking trazodone 2
2. Do not assume a positive screen equals illicit fentanyl use without confirmatory testing - this is particularly important for legal, employment, or child custody matters 2
3. Remember that the trazodone FDA label does not mention this interference 4, so you must rely on clinical laboratory medicine literature

Recommended Approach

When a patient on trazodone has a positive fentanyl screen:

1. Immediately order LC-MS/MS confirmatory testing before taking any clinical action 1, 3
2. Consult with the testing laboratory if results don't correlate with clinical findings 2
3. Document the trazodone use in the medical record as a potential cause of the positive screen
4. Wait for confirmatory results before making accusations, changing treatment plans, or reporting to authorities

The confirmatory LC-MS/MS test will accurately distinguish between true fentanyl/norfentanyl presence and trazodone interference, as it has outstanding specificity and sensitivity 3.