Naltrexone is an FDA-approved medication that can help support your efforts to recover from opioid use disorder (OUD) or alcohol use disorder (AUD). One of the biggest obstacles to abstaining from opioids or alcohol is powerful cravings. Receiving naltrexone treatment as part of your recovery plan can help reduce cravings so that you find it easier to remove these substances from your life. With this in mind, you may be wondering, “How long does Naltrexone last to reduce cravings?” The answer lies in which form of naltrexone and dosage your provider prescribes. Whether you prefer in-person or online medication-assisted treatment, you should always access naltrexone care from a qualified provider. 

Convenient, online medication-assisted treatment is often a good fit for a busy lifestyle. Reach out to the professionals at Confidant Health for virtual Suboxone and naltrexone treatment for substance use disorder. Download our app today to schedule an assessment with a practitioner at our online Suboxone clinic

What Is Naltrexone?

Naltrexone is an opioid antagonist medication used to help manage opioid and alcohol use disorder. It is available as a daily tablet or monthly injection. Your provider can help determine which of these two administration methods may be right for you.

How It Works

As an opioid antagonist, naltrexone binds to opioid receptors in the brain. This prevents other opioids from being able to attach to these receptors and induce euphoria. Without the reinforcement of euphoric effects from opioids, cravings may be reduced, making it easier to abstain from opioid misuse. 

In the case of alcohol, naltrexone prevents endorphins from binding to opioid receptors and releasing the feel-good hormone dopamine. By blocking the release of dopamine, you do not experience the pleasurable effects of alcohol. Naltrexone helps your brain begin to disassociate positive feelings with alcohol consumption, which helps to minimize cravings.

Average Duration of Effects

Naltrexone is designed to bind with opioid receptors in the brain to prevent other opioids from interacting with these receptors. This action helps reduce cravings, but the average length of time naltrexone will last depends on the method of administration and the dosage. This medication is offered as either a 50 mg tablet or a 380 mg injection.

Naltrexone Pill/Tablet

Oral naltrexone is delivered as a short-acting pill with effects lasting between 24 to 72 hours. The standard naltrexone dosage is 50 mg daily. Your provider will likely prescribe one of these three dosages:

  • One 50 mg tablet daily

  • Two 100 mg tablets every other day

  • Three 150 mg tablets every third day

Although these are the most common dosages, your provider will factor in your current state of health to determine the appropriate dosage and schedule for your needs.

Naltrexone Injection/Shot (XR-NTX)

The naltrexone shot is delivered as an extended-release injection that blocks opioids for up to one month. This injection contains 380 mg of naltrexone. The effects of the naltrexone injection peak approximately two hours after administration and again two to three days later. Although the amount of the medication in your system begins to drop after about 14 days, you will still benefit from the full opioid-blocking effects of naltrexone for the remaining 14 days.

For some people, the convenience of a once-monthly injection may be preferable, but it is up to your provider to determine if this is the appropriate administration method for you. Unlike oral naltrexone, you will need to visit your provider's office to receive your monthly injection.

Naltrexone Half-Life

To know how long the effects of naltrexone last in the body, it is helpful to understand the half-life of the medication. The half-life of a medication is the length of time it takes for half of the drug to be metabolized and eliminated from your system. The half-life of naltrexone is largely dependent on the method of administration. However, other factors can also impact how long naltrexone lasts in your body.

Oral naltrexone has a half-life of four hours, which then breaks down into the metabolite 6-β-naltrexol, which has a half-life of 13 hours. On the other hand, injectable naltrexone has a half-life of five to 10 days. The general rule is that it takes five half-lives for a medication to be completely eliminated from your body. This means that oral naltrexone can last for 20 to 65 hours (approximately one to three days), and the naltrexone shot can last for 25 to 50 days (about one to two months). 

The specific amount of time naltrexone will last for you will depend on whether you receive oral or injectable naltrexone. It will also be impacted by other factors that may change over time, as noted in the next section. Speak with your provider about any concerns you have about your naltrexone medication wearing off more quickly than expected.

Factors Influencing Naltrexone’s Effects

How long naltrexone’s effects last in your body will be influenced by the following factors:


As mentioned above, the dosage of naltrexone your provider prescribes will impact how long the effects of oral naltrexone will last. A 50 mg dose will help block the effects of opioids for 24 hours, while a 150 mg dose will last up to 72 hours.

Administration Method

As mentioned above, naltrexone is available as a short-acting tablet or an extended-release injection (KR-NTX). You will experience the longest-lasting effects from a once-monthly injection of naltrexone.


The older you are, the longer it will take for naltrexone to leave your system. 


People with a faster metabolism will process naltrexone more quickly, so the effects may wear off faster. 

Liver and Kidney Health

Your liver and kidney play crucial roles in breaking down and processing the food, beverages, and medications that pass through your system. If your liver and kidney function are compromised, it can take longer for them to process naltrexone, which may prolong the effects.

Hydration Levels

The more well-hydrated you are, the faster naltrexone may pass through your system. Dehydration tends to slow down how efficiently your body can flush substances from your system. 

Body Mass

The more body fat you have, the longer it can take for naltrexone to leave your system. After your body breaks down naltrexone, the metabolites can accumulate in fatty tissues, extending the medication's elimination time.

As your treatment for OUD or AUD progresses, you may experience some changes in the above factors. Healthy lifestyle changes, such as losing weight or being more vigilant about your water intake, can change how long naltrexone lasts. An illness or health condition can also affect your naltrexone treatment, so you may want to speak with your provider about your dosage if you experience any changes in your health.

Confidant Health: Virtual Naltrexone Treatment for OUD and AUD

At Confidant Health, we understand that it can be challenging to fit treatment into your busy day. With the help of our online medication-assisted treatment, you can cut back on or completely eliminate opioids or alcohol from your life, all on a convenient schedule that works for you. Experience the difference virtual naltrexone treatment can make by scheduling an online assessment with our caring team today.