Can Naloxone Cause a False Positive on a Drug Test?
Evidence-based answer reviewed against SAMHSA cutoffs and FDA assay documentation · Updated September 2026
Quick answer: Possibly — at the screening stage. None — naloxone has no documented cross-reactivity with any standard drug immunoassay. Confirmation testing (GC–MS/LC–MS/MS) distinguishes true positives from assay artifacts, so documented false positives almost never survive to final results.
How Naloxone interacts with drug tests
Naloxone is an opioid antagonist used to reverse opioid overdoses — it is not a drug of abuse and produces no intoxication. It appears on no standard or expanded drug panel, and it does not cause positives for opioids or any other screened drug.
If you administered naloxone to someone else (or received it yourself during an overdose), it will not show up on your own drug test. The only interaction to know about is medical, not testing: naloxone can precipitate withdrawal in opioid-dependent people.
The 'does Narcan show up on a drug test' question is common because people carry or administer it in emergencies. The answer is no: no panel screens for it, and it has no cross-reactivity with any standard immunoassay.
The documented false-positive table
| Screen flagged | Documented cross-reactants (immunoassay tier only) |
|---|---|
| Amphetamines | Bupropion (bupropion), trazodone, phentermine, pseudoephedrine, labetalol, promethazine, methylphenidate |
| PCP | Dextromethorphan (dextromethorphan cough syrup), diphenhydramine (diphenhydramine), doxylamine (multi-symptom cold remedies), tramadol, venlafaxine (venlafaxine), ketamine |
| Opiates | Poppy seeds (true positive), quinine, dextromethorphan, ofloxacin/levofloxacin, rifampin |
| Benzodiazepines | Sertraline (sertraline), oxaprozin (case reports) |
| Methadone | Diphenhydramine, doxylamine, verapamil, quetiapine (quetiapine), clomipramine |
| Tricyclics (TCA) | Cyclobenzaprine (cyclobenzaprine), hydroxyzine, carbamazepine, diphenhydramine |
| Cannabinoids (THC) | Efavirenz, pantoprazole (isolated reports); dronabinol/dronabinol = true positive |
How to defend a disputed result
- Declare everything at collection — prescriptions, sleep aids, poppy bagels. The collector's questionnaire feeds the MRO review.
- Answer the MRO call (three attempts over 24 hours in DOT programs). Missed calls convert positives automatically.
- Request split-specimen retest within 60 days if you dispute — the sealed second vial exists exactly for this.
- Bring documentation: pharmacy printouts, physician letters, discharge summaries.
Certified labs nationwide · Results in 1–2 days
Need a test? Order online, test same-day →People also ask
Does Naloxone Show up on a Drug Test?
No — Naloxone is absent from standard drug panels. Full guide →
Can Narcan Cause a Positive Drug Test?
Can Naloxone trigger a false positive? Cross-reactivity evidence, confirmation testing, and how to clear your name with the MRO. Full guide →
Naloxone Drug Test Guide: Panels, Detection Windows & More?
Complete Naloxone drug test guide: which panels detect it, urine/hair/saliva/blood detection windows, cutoff levels and prescription verification. Full guide →
How Long Does Naloxone Stay in Urine?
How long Naloxone stays detectable in urine — urine, hair, saliva & blood windows explained with cutoffs. Full guide →
Do prescriptions count against me?
No — verified prescriptions report as negative through the Medical Review Officer. Declare medications at collection and answer the follow-up call.
Sources & further reading
- SAMHSA — Mandatory Guidelines for Federal Workplace Drug Testing Programs (cutoffs, MRO process)
- DOT — 49 CFR Part 40 procedures for transportation workplace testing
- Brahm NC et al., Mayo Clinic Proceedings 2008;83(1):66–76 — false-positive cross-reactivity reference
- FDA — drug-of-abuse test device labeling (detection window conventions)