Naltrexone, an opioid antagonist, is FDA-approved for treating Alcohol Use Disorder (AUD) and Opioid Use Disorder (OUD). Its active end-product, 6-beta-naltrexol, binds to and occupies opioid receptors. As a result, opioids cannot bind to their receptors and produce the feelings of euphoria that substance misusers are seeking. This discourages opioid and alcohol misuse.  

In this article, the experts at Confidant Health break down when is the best time for you to take Naltrexone. Read on to learn more. 

When Should You Take Naltrexone?

Manufacturers do not appoint one specific time of day as being better than another to take Naltrexone. Thus, users can decide when is the best time to take Naltrexone, based on their preferences and lifestyle. 

Why you may Prefer to Take Naltrexone in the Morning

Some users prefer to take Naltrexone in the morning. Here’s why: 

  • Pairing your dose of Naltrexone with breakfast makes it easier to remember. This means fewer missed doses and better results. 

  • Naltrexone can aid weight loss. Studies show Naltrexone can reduce appetite by up to 30%. This means that taking it early in the morning can help reduce food cravings throughout the day and enable you to lose weight. 

  • Research shows Naltrexone can cause insomnia (difficulty falling and staying asleep) in 10% of users. This is because Naltrexone decreases the release of endorphins (or feel-good hormones) by suppressing opioid activity. As a result, the body may not be able to adequately relax for sleep. So, taking Naltrexone in the morning may better suit users who experience difficulty sleeping. 

Why you may Prefer to Take Naltrexone at Night

Some users choose to take Naltrexone at night for many reasons; some of these include:

  • Some users report daytime sleepiness when taking Naltrexone. Thus, patients that operate heavy machinery during the day should take the medication at night. 

  • Studies show that low-dose Naltrexone may relieve pain and symptoms of chronic fatigue syndrome. It achieves this by suppressing the release of chemicals (cytokines) that cause pain. So, people with chronic fatigue syndrome may sleep more comfortably if they take Naltrexone before bed. 

  • 90% of men in a clinical trial experienced sexual dysfunction while taking Naltrexone. To avoid the potential impact of these symptoms, most male users prefer taking the medication right before they sleep.

Who Should Take Naltrexone With Food?

Gastrointestinal disturbances, such as nausea and vomiting, can affect up to 15% of Naltrexone users. Luckily, patients can minimize these symptoms by taking Naltrexone with food. 

How do you take Naltrexone?

Naltrexone is available in two main formulations, these are either an oral tablet or intramuscular injection. Doctors recommend abstaining from opioids and alcohol for at least seven days before taking the first dose of Naltrexone. Otherwise, Naltrexone may induce withdrawal by dislodging existing opioids from their receptors.   

The Sinclair Method: An Alternative

The Sinclair Method is an evidence-based treatment for Alcohol Use Disorder that allows users to take alcohol with Naltrexone (as opposed to traditional treatments). 

This treatment aims to retrain the brain to no longer associate feelings of euphoria with alcohol use. In other words, users no longer feel a ‘buzz’ when they take Naltrexone before alcohol. Over time, the brain adapts to no longer associating that ‘buzz’ with drinking alcohol and eventually reduces cravings for alcohol. 

What to Consider Before Taking Naltrexone?


Naltrexone, like any other medication, can cause an allergic reaction, which can be dangerous. If you notice a rash, breathing difficulty, or other symptoms of an allergic reaction after taking the medication, visit your nearest ER immediately. 

Drug Interactions

Naltrexone can alter the effects of many medications on the body. So, you should consult a qualified professional before taking Naltrexone if you are already taking:

  • Opioid analgesics

  • Cough and cold medications

  • Anti-diarrheal preparations

  • CNS depressants

  • Disulfiram

  • Thioridazine

Medical Problems

Doctors recommend users avoid Naltrexone, or only use the drug when necessary, if they have any of the following medical conditions:

Frequently Asked Questions

Does Naltrexone Work Right Away? 

Generally, patients can feel the effects of Naltrexone within one hour of taking it. Though, this can vary greatly between users, depending on the overall status of their medical health.

How Long Does Naltrexone Remain in the System?

The oral formulation of Naltrexone has a half-life (the time it takes for its concentration to half) of 4 hours. The body takes between 4-5 half-lives to eliminate most drugs. This means that oral Naltrexone may remain in the system for up to 30 hours. 

Injectable depot Naltrexone, on the other hand, has a half-life of 5-10 days. So, it takes the body between 25-50 days to completely eliminate this injectable formulation of Naltrexone. 

What to do if you Miss a Naltrexone Dose?

If you miss a dose of Naltrexone, take the medicine as soon as possible.

However, if it is almost time for your next dose, doctors do not recommend making up for the missed dose. As always, it's best to consult your healthcare provider before taking or discontinuing any medications. 

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