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How Long Does Naltrexone Stay in Your System?

by Landmark Recovery

May 8, 2025
person sitting pensively thinking about naltrexone and its duration

When beginning medication-assisted treatment services for opioid or alcohol addiction, many people ask, “How long does naltrexone stay in your system?” This is an important question, especially for those planning their recovery journey.

Understanding the naltrexone half-life, how the body processes the medication, and what to expect when taking naltrexone can help set realistic expectations and improve treatment outcomes.

What is naltrexone’s duration?

Naltrexone’s duration in your system depends on how the medication is administered:

The oral form is typically taken once daily, while the injection is administered once a month, offering extended coverage against opioid and alcohol cravings.

How naltrexone works in the body

Naltrexone is an opioid antagonist, meaning it binds to opioid receptors without activating them, effectively blocking the euphoric and sedative effects of opioids and alcohol. This mechanism helps to reduce cravings and decrease the risk of relapse.

Patients typically begin to feel the medication’s effects, including reduced cravings, within one to two hours of ingestion or injection.

Naltrexone’s half-life and metabolism

Understanding a medication’s half-life provides insight into how long it stays in your body. A drug’s half-life refers to the time it takes to metabolize and eliminate half of the drug.

  • Oral naltrexone has a half-life of approximately four hours.
  • Its primary metabolite, 6-beta-naltrexol, has a half-life of about 13 hours.
  • Injectable naltrexone (Vivitrol®) has a longer half-life of five to 10 days.

Given these figures, oral naltrexone and its metabolites are usually cleared from the body within 20 to 78 hours. Injectable forms can remain in the system for several weeks.

Factors influencing how long naltrexone stays in your system

Several factors can influence the naltrexone duration in the body:

  • Age: Older individuals may process medications more slowly.
  • Liver function: As naltrexone is primarily metabolized by the liver, impaired liver function can extend the duration the drug remains in the body.
  • Overall health: Conditions affecting metabolism may alter drug processing.
  • Genetics: Some people have genetic variations that affect how quickly medications are metabolized.
  • Dosage and frequency: Higher doses and frequent use can lead to longer detectability.

Detection of naltrexone in drug testing

Standard drug tests do not typically screen for naltrexone, as it is a prescribed medication for substance use treatment. However, specialized tests can detect it in biological samples:

Sample Type

Detection Window

Urine

4 hours to several weeks

Blood

Up to 24 hours post-ingestion

Saliva

Up to 24 hours post-ingestion

Hair

Up to 90 days

Because naltrexone is not a substance of abuse, most employment or legal drug screenings will not test for it.

What to expect when taking naltrexone

Starting naltrexone treatment usually involves a brief adjustment period. Here’s what to expect when taking naltrexone:

  • Cravings for opioids or alcohol may significantly diminish within hours.
  • Patients might notice reduced pleasure if they attempt to use opioids or drink alcohol.
  • Some initially experience mild side effects such as nausea, headache, or fatigue, but these usually subside.

It’s essential to work closely with a medical team during the start of treatment, especially if transitioning from opioid use, to prevent precipitated withdrawal.

Begin your recovery journey with Landmark Recovery

If you or a loved one is considering medication-assisted treatment and wondering about options like naltrexone, Landmark Recovery is here to help.

Take the first step today. Call Landmark Recovery at (888) 448-0302 or complete our online form to learn more about our medication-assisted treatment services and how we can support you or your loved one.

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We're here 24/7 to help you get the care you need to live life on your terms, without drugs or alcohol. Talk to our recovery specialists today and learn about our integrated treatment programs.

About the Author

Landmark Recovery

Landmark Recovery

Landmark Recovery was founded with a determination to make addiction treatment accessible for all. Through our integrated treatment programs, we've helped thousands of people choose recovery over addiction and get back to life on their own terms. We're on a mission to save one million lives over the next century. We encourage all those struggling with substance use to seek professional help.