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Pain Management, Naltrexone, Quantitative, Urine

Test code(s) 93753

Question 1. What is naltrexone?

Naltrexone, an oxymorphone congener, is an opioid antagonist used primarily to treat alcohol dependence. According to the Sinclair Method of treatment, the patient takes naltrexone before drinking alcohol. The patient does this each time he or she has a drink. This results in a reduction of alcohol cravings (mechanism unknown) in the majority of patients. The Sinclair Method results in a greater reduction in cravings than taking naltrexone while abstaining from alcohol.1 Naltrexone is ineffective for reducing opioid cravings but has been FDA-approved for blocking opioid euphoric effects.

Naltrexone undergoes extensive first-pass metabolism with conjugated naltrexone and free and conjugated 6-beta-naltrexol appearing as the major metabolites. The elimination half-lifes for naltrexone and 6-beta-naltrexol are 4 hours and 13 hours, respectively. 6-Beta-naltrexol is the major urinary metabolite.

Oral naltrexone (as a hydrochloride salt) is marketed under the trade name ReVia® (FDA approved 1984). A once-per-month extended release, intramuscular injection version is marketed under the trade name of Vivitrol® (FDA approved 2006).

Naltrexone should not be confused with naloxone (used in emergency settings to treat opioid overdose) or methylnaltrexone (used to treat constipation).

Question 2. Why test for naltrexone and 6-beta-naltrexol?

Naltrexone and 6-beta-naltrexol detection in urine is used to obtain objective data regarding patient compliance with medication use. Testing can demonstrate whether the patient has taken the medication and whether the drug was absorbed and metabolized.

Question 3. Which tests are available for urine naltrexone testing?

Quest Diagnostics offers 1 test, which includes detection of naltrexone and its metabolite 6-beta-naltrexol.

  • Test code 93753, Pain Management, Naltrexone, Quantitative, Urine

This method uses liquid chromatography-tandem mass spectrometry (LC-MS/MS). The assay cutoff for detection is 5 ng/mL for both naltrexone and 6-beta-naltrexol.

Question 4. When should specimens be collected for naltrexone and 6-beta-naltrexol testing?

The optimal time to collect the urine specimen is when the patient is at steady state (approximately 1 week after onset of treatment).

Question 5. What does the test result mean?

Negative results indicate absence of drug and/or metabolite or concentrations below the assay cutoff. Positive results indicate presence of the respective drug and/or metabolite. Detection of naltrexone and 6-beta-naltrexol, or only 6-beta-naltrexol, suggests that the patient has taken and metabolized the drug. For patients prescribed oral medications, urinary detection of only the unchanged drug (naltrexone) and no metabolite (6-beta-naltrexol) may indicate tampering with the specimen and medication noncompliance.

There is no correlation between the time of dose, the dose taken, and the concentration of drug and/or metabolite in the urine. Measuring random urine creatinine will determine if the specimen is diluted. Diluted urine may affect the assay detection of the drug or metabolite around the cutoff concentration.

Question 6. Can specimens for naltrexone testing be sent in the same bag with other clinical specimens?

Yes. Prescription drug monitoring and urine drug testing are considered clinical tests; therefore, specimens may be placed in the same specimen bag (one patient per bag).



  1. Definitive Statement by John David Sinclair, Ph.D. C Three Foundation.http://www.cthreefoundation.org/statement-by-john-david-sinclair-phd.html.
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.182 Version: 0
Effective 06/06/2016 to present