Does Naltrexone Make You Sleepy or Tired?

Sleepiness and insomnia are both more common than on placebo

In a safety study of about 570 people taking naltrexone tablets for alcohol, 4% had new tiredness, 3% insomnia and 2% sleepiness.^5,6 That study had no placebo group.⁶ In placebo-controlled trials, the 2010 Cochrane review counted sedation, along with stomach upset, among naltrexone's main side effects: about 9 more people per 100 had daytime sleepiness than on placebo (95% CI, 5 to 14).¹ A 2019 review pooled 12-week trials of 50 mg a day. In 4 trials with 529 people, the odds of daytime sleepiness were 1.85 times those on placebo (95% CI, 1.19-2.87). In 4 trials with 514 people, the odds of insomnia were 1.99 times (95% CI, 1.16-3.39).² Almost all of these data come from people reporting side effects rather than sleep-lab measurements.²

Source: the 2019 review's table of included trials, plus the Vivitrol label for the shot.² The COMBINE row matches the trial's own adverse-event table: 112 of 309 people on naltrexone alone and 72 of 309 on placebo, with each group pooled across the behavioral-therapy arms.⁷ COMBINE and Oslin 2008 used 100 mg, twice the 50 mg label dose for alcohol.⁵ The label's all-doses column for the shot (5% sleepiness) includes 190 mg and 400 mg groups.⁴ See Vivitrol side effects.

Early sobriety disrupts sleep too

Sleep recovers only partly in the first 30 days without alcohol.⁸ Insomnia after stopping drinking can last weeks to years, so if you started naltrexone and stopped drinking in the same week, either change could be making you tired.³

It tends to start early; how long it lasts is barely studied

Reports collected after the tablet's approval show that most side effects "usually occur early in the course of drug therapy and are transient."⁵ The VA/DoD guideline says side effects tend to appear early and can typically resolve within 1 to 2 weeks after a dose adjustment.⁹ Neither gives a day count for sleepiness.

The one duration figure in these sources comes from a small trial of older adults (44 people). Sleep problems were about as common on placebo (38%) as on naltrexone (35%), but lasted 2.9 weeks on average on naltrexone and 1.4 weeks on placebo; the review marks the result not significant.² Tell your doctor if drowsiness is severe or does not go away.¹⁰ The wider early-weeks timeline is on how long naltrexone takes to work.

Alcohol feels more sedating on naltrexone

In human laboratory studies of drinking on naltrexone, alcohol felt more sedating than on placebo (18 studies, 777 people), though the effect was small.¹¹ What else changes when you drink on it is on naltrexone and alcohol.

When tiredness is a warning sign

• Very drowsy with slowed breathing, or faint and confused, after using opioids. These are overdose signs: call 911. Naloxone can reverse an opioid overdose, but call 911 even if it is given.⁴ The overdose risk after stopping naltrexone is covered on naltrexone side effects.
• Tired or sleepy all the time, sleeping much more or less than usual, or feeling sad and losing interest in things. The Vivitrol Medication Guide lists each of these as a depression sign that needs a call to your provider right away.⁴ For thoughts of self-harm, call or text 988.¹²
• Tiredness with dark urine, yellowing eyes or stomach pain lasting more than a few days. These can be signs of liver injury.^4,10
• Taking thioridazine. Lethargy and sleepiness have been reported with the combination.⁵

Both labels advise against driving or using heavy machinery until you know how naltrexone affects you, because it can cause dizziness.^4,5

Low-dose naltrexone and Contrave have their own sleep effects

Low-dose naltrexone (LDN), an off-label use: in one research group's LDN trials, about 37% of participants reported more vivid dreams, and a minority had nightmares. Vivid dreams were also the most common complaint while those participants took placebo, so expectation may explain some cases.¹³ See low-dose naltrexone side effects.

Contrave, a weight-loss pill that combines naltrexone with bupropion, had insomnia in 9.2% of people against 5.9% on placebo in trials of the combination.¹⁴ See naltrexone and bupropion (Contrave).

Your experience: If naltrexone changed how you sleep, you can share your story. Stories appear on naltrexone reviews only with permission.

How we checked

• Rates come from the current tablet, Vivitrol and Contrave labels on DailyMed.^4,5,14 Trial rows come from the full text of Panin and Peana 2019; the COMBINE row was also checked against the trial report.^2,7
• Other figures come from PubMed abstracts or full texts, all read on October 17, 2026.