Yes, a positive naloxone test in a patient taking Suboxone is normal and expected.
Naloxone is detectable in the urine of patients taking sublingual buprenorphine/naloxone (Suboxone) despite previous assumptions that it was poorly absorbed. This is an important clinical finding that contradicts older teaching about this medication.
Key Evidence
The FDA label for Suboxone states that "blood levels of the drug were measurable" when naloxone is administered sublingually, even though it has "no clinically significant effect when administered by the sublingual route" 1. More importantly, recent research demonstrates that:
- Naloxone metabolites are detected in 88-91% of patients taking sublingual buprenorphine/naloxone 2
- In a large cohort of 425 patients prescribed sublingual buprenorphine/naloxone, naloxone-glucuronide (the primary metabolite) was found in the vast majority of urine samples 2
- Multiple studies confirm that naloxone is routinely detectable in urine during compliant use of Suboxone 3, 4, 5
Clinical Interpretation
The presence of naloxone in urine drug testing indicates medication adherence, not misuse. When interpreting these results:
- Expected naloxone levels: Most patients show naloxone concentrations between 5-200 ng/mL, with a median around 60-70 ng/mL 3
- Absence of naloxone with positive buprenorphine suggests the patient may be taking buprenorphine alone (not the combination product) 3
- Extremely high naloxone levels (>2000 ng/mL) may indicate specimen tampering or "spiking" 4
Important Caveats
The 2021 Mayo Clinic perioperative guideline notes a specific exception: Naloxegol (a peripherally-acting opioid antagonist) may result in false-positive naloxone screening results due to conversion to naloxone during metabolism 6. Verify the patient is not taking this medication before interpreting results.
Do not dismiss or penalize patients based on positive naloxone results when they are prescribed Suboxone - this represents appropriate medication adherence. The CDC guidelines emphasize that clinicians should not dismiss patients from care based on urine drug test results, as this could have adverse consequences for patient safety 7.