The standard naltrexone dose for alcohol use disorder is 50mg, taken roughly one hour before drinking (for the Sinclair Method) or once daily at the same time (for daily protocols). The dose is the same in both cases. What changes is when and how often you take it. This article is part of our Naltrexone hub, the complete guide to using naltrexone for alcohol use disorder.

The pillar covers the basics. This article goes deep on the practical dosing questions that come up once you have a prescription: why 50mg, why one hour, what to do when you miss a dose, when to consider splitting it, and the edge cases nobody warns you about. If you’ve just started or are about to, this is the operating manual for the tablet itself.

# Why 50mg

The 50mg dose comes from the original FDA approval trials in 1994 (for daily naltrexone) and the Sinclair Method trials shortly after. Across thousands of patients, 50mg was the dose that:

  • Reliably saturated opioid receptors enough to interrupt the alcohol-reward feedback loop
  • Produced manageable side effects in the majority of patients (nausea and headache being the main ones)
  • Showed the strongest treatment effect on drinking outcomes

Higher doses (100mg, 150mg) have been studied. The benefit plateaus around 50mg for most people. The side effect burden goes up. Lower doses (25mg, 12.5mg) work for some people and are useful as a starting point if you’re nausea-prone, but they are not the trial-validated effective dose.

The exception is low-dose naltrexone (LDN), typically 1.5mg to 4.5mg, which is a different protocol entirely with a different mechanism (immune modulation rather than opioid blockade). LDN for alcohol use disorder has weak evidence and is mostly used off-label for chronic pain and autoimmune conditions. We cover it in the Low-Dose Naltrexone for Alcohol article if you’ve been told it might help.

For mainline naltrexone treatment of alcohol use disorder, 50mg is the answer. If your prescriber starts you at 25mg for the first 1-2 weeks to ease side effects, that is reasonable and common practice. Just plan to step up to 50mg by week 3.

# The one-hour rule (for TSM)

For the Sinclair Method specifically, the rule is: take the tablet roughly one hour before your first drink. Not at the same time. Not after the first drink. One hour before.

This isn’t a suggestion. Naltrexone needs time to:

  1. Dissolve in the stomach (15-30 minutes)
  2. Absorb into the bloodstream (peak around 60 minutes after dosing)
  3. Saturate the mu-opioid receptors in the brain (within minutes once the drug is in the bloodstream)

If you drink before the medication is on board, you’ve drunk on partially blocked receptors, which is closer to drinking unmedicated than drinking medicated. The reward feedback gets through partially, the conditioning gets reinforced, and your TSM progress slows.

In practice, “one hour” has about thirty minutes of forgiveness on either side. Forty-five minutes is fine. Two hours is also fine. Fifteen minutes is not. We covered the practical patterns in the Sinclair Method explained article: the pub plan, the end-of-work-day signal, the dinner reservation. The mechanics are the same: build a routine where the tablet happens predictably ahead of the drinking.

For daily naltrexone (taken every day regardless of drinking), the one-hour rule doesn’t apply. You take the tablet at the same time each day, usually morning, and let it stay in your system. The half-life takes care of coverage.

# How long the tablet lasts

Naltrexone’s plasma half-life is about 4 hours, but its primary metabolite (6-beta-naltrexol) has a half-life of around 13 hours and provides most of the receptor blockade. The practical effect:

  • Onset: ~60 minutes after dosing
  • Peak effect: 2-4 hours after dosing
  • Effective coverage: roughly 12 hours, fading toward 24 hours
  • Full clearance: 3-5 days for the metabolite

For a typical 4-6 hour drinking session, one 50mg tablet covers you. For longer events (wedding receptions, festival days, all-day birthdays), you may need a redose.

A wristwatch on a wooden table, suggesting careful timing of medication.
Photo by Polina ⠀ on Pexels

# When to redose

The standard guidance: if your drinking session is going to run more than 8-10 hours, take a second 50mg tablet 6-8 hours after the first.

Examples:

Wedding starting at 1pm, going until midnight. Take the first tablet at noon. Take a second at 7-8pm.

Festival day starting at 11am, finishing at 11pm. First tablet at 10am, second at 5-6pm.

Christmas Day with drinks from breakfast onwards. First tablet at 9am. Second at 4-5pm. Probably stop drinking by 9pm to give your liver a break.

Two doses in one day at 50mg each (100mg total) is well within standard clinical ranges and most prescribers are comfortable with it. Worth confirming with yours, especially if you’re nausea-prone in the first weeks. If you’re new to naltrexone and still in the side-effects window (first 14-21 days, see our Naltrexone side effects guide), redosing the same day can amplify nausea. Try to avoid all-day drinking events during your first month on the medication if you can.

# What to do if you miss a dose

The honest answer depends on what kind of “missed” we’re talking about.

Forgot the morning dose for daily naltrexone. Take it as soon as you remember if it’s still the same day. If it’s already evening and you’d be taking it close to bedtime, skip and resume tomorrow. Don’t double up.

Forgot to take it before drinking on TSM. This is the harder case. If you’ve already had a drink unmedicated, taking the tablet now doesn’t undo the reinforcement that drink provided. The receptors aren’t blocked from drink one. Two options:

  1. Take it now anyway. Subsequent drinks are at least partially medicated. Imperfect, but better than continuing fully unmedicated.
  2. Skip this session entirely. Stop drinking, take it correctly next time. Some TSM practitioners argue this is the cleaner choice.

There’s no consensus on which is better. Practical reality: most people take it late and continue drinking. The protocol still works on average; missed doses just slow it.

Took it but then didn’t drink. No issue. Naltrexone with no alcohol is essentially a non-event for most people. The tablet was wasted in the sense that it didn’t reinforce extinction (no alcohol to extinguish), but it didn’t harm you either.

# Splitting the dose

Some people, especially those with strong nausea on full 50mg doses, ask about splitting the tablet into two 25mg halves taken closer together (e.g. 30 minutes apart).

The medical literature doesn’t strongly support this. The 50mg dose is what’s been studied. Splitting doesn’t reduce nausea reliably; it just delays the peak slightly. If you’re struggling with side effects:

  1. Better strategy: take the tablet with food (a small meal, not a snack). Reduces nausea for most people.
  2. Step-up strategy: ask your prescriber to start you at 25mg for week 1, then 50mg from week 2. This approach is reasonably common and well-tolerated.
  3. Time-of-day strategy: for daily protocols, taking the tablet at bedtime instead of morning lets you sleep through the worst of the early-onset nausea.

Splitting a single 50mg dose into two 25mg doses given in the same session doesn’t appear in any major treatment guideline.

A simple breakfast with a glass of water on a wooden kitchen table in morning light.
Photo by Ela Haney on Pexels

# Naltrexone with food vs without

You can take naltrexone with or without food. With food slightly delays peak absorption (by maybe 30 minutes) and substantially reduces nausea.

For TSM specifically, this matters slightly. If you take the tablet at 5pm with dinner and plan to drink at 6pm, the food may delay peak effect to closer to 7pm. The receptors aren’t fully saturated yet at the moment of your first drink. In practice, the tablet is still effective because partial coverage is still meaningful coverage, but the optimum is to allow the full hour even with food.

Practical rule: take it with food during the side-effects window (first 3-4 weeks). After that, take it however suits the routine. Most people forget to overthink it after the first month.

# Naltrexone and other medications

Naltrexone interacts with:

  • Opioid pain medications. This is an absolute contraindication. Naltrexone blocks the same receptors opioids work on, so you’ll get no pain relief AND can trigger acute withdrawal if you have any opioids in your system. Our Naltrexone vs Acamprosate vs Disulfiram article covers what to consider if you might need pain control.
  • Tramadol. Even though it’s “weak”, it’s still an opioid agonist. Same problem.
  • Codeine, in cough syrups. Often forgotten. Check labels.
  • Buprenorphine, methadone. Used in opioid use disorder treatment. Naltrexone is not compatible with these.

Mostly fine alongside:

  • SSRIs and other antidepressants (no significant interaction)
  • Most blood pressure medications
  • Most cholesterol medications
  • Acamprosate (some clinicians combine them; evidence is mixed but no safety issue)
  • Disulfiram (some clinicians combine them; rare)
  • Common over-the-counter painkillers like paracetamol/acetaminophen and ibuprofen (these aren’t opioids)

If you’re on any prescription medication when starting naltrexone, mention all of it to your prescriber. Don’t assume an OTC supplement is fine without checking. Kratom in particular acts on opioid receptors and would conflict.

# How long to stay on it

For daily naltrexone, the standard course is 3-6 months minimum, with many patients staying on it indefinitely if it’s helping and side effects are tolerable. Some prescribers will reassess at 6 months and discuss tapering.

For TSM, the protocol is open-ended. The Sinclair Method is designed to be taken for as long as you drink alcohol. Some people use it for a year and then transition to abstinence. Some use it indefinitely as a maintenance tool. There’s no fixed endpoint.

In both cases, when you stop:

  • Receptors are clear within 3-5 days
  • The drinking-craving feedback loop returns to whatever state you’ve trained it into
  • For TSM patients with good extinction, the underlying urge to drink is much lower than baseline; for daily-naltrexone patients, the urge typically returns to its prior level

If you’re stopping after long use, it’s worth doing it under prescriber guidance, not because of withdrawal (naltrexone has none) but because the behavioural rebound is real and worth planning for.

# How AlcoLog helps with dosing

AlcoLog’s Medications card has a dedicated naltrexone entry alongside six other alcohol-related preparations. Each dose gets a timestamp via the 24-hour time picker. The redose timer (set in hours + minutes) reminds you when a long session needs a second tablet, useful for the 8-10 hour event scenarios above.

The last-24h dose list shows what you’ve taken and when at a glance, so you know where you are in the coverage window without doing mental math. Pro-tier location reminders fire when you arrive at a saved location (the pub, a friend’s house) so the tablet is one of the first things you do, not the last.

AlcoScore deliberately excludes medication use from its scoring. The app’s view: medication is a tool you choose to use, not a behaviour the app should grade you on. So your dose log informs you, not your score. All your data stays on your device, no account required. CSV export of your last 10 sessions is free; unlimited export and PDF reports are on Pro if you want a printout for your doctor.

Try AlcoLog free →

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