What are the side effects of naltrexone for alcohol use disorder?
This article describes medications used for alcohol use disorder. It is educational and not medical advice. Talk to a licensed clinician about whether any specific medication fits your situation.
Asking what naltrexone will actually feel like is the most sensible question to bring to it — and the honest answer is calmer than a page of search results makes it look.
So, what are the side effects of naltrexone when it's prescribed for alcohol use disorder? For most people: nausea, headache, dizziness, and tiredness, showing up in the first days to weeks and often fading as the body adjusts. A shorter list — liver cautions, mood changes, and one hard rule about opioid painkillers — deserves real attention. Here's how to tell the nuisances from the warnings.
What are the most common side effects?
Nausea, more than anything else. On the FDA label for naltrexone tablets, the effects people report most often when taking it for alcohol dependence are nausea, headache, dizziness, tiredness, trouble sleeping, and stomach discomfort or cramping. Some people also feel more anxious or keyed-up in the first stretch.
Two details take the edge off that list. These effects are usually mild to moderate, and they're front-loaded — most noticeable in the first week or two, then easing as your body adapts. There's no universal timeline, but "bad forever" isn't the typical story. If a symptom is still wrecking your day after those early weeks, that's not something to white-knuckle; it's a reason to call your prescriber, who can look at food, timing, the formulation, or a different medication entirely.
Why would a pill for drinking upset your stomach?
Because of where it works. Naltrexone blocks the brain's opioid receptors — the docking sites your own feel-good chemicals, endorphins, normally use. SAMHSA describes it as binding to those endorphin receptors and blocking the effects and feelings of alcohol, which is why drinking on naltrexone tends to feel flatter and cravings lose some of their pull. A review in American Family Physician makes the same point from the mechanism side: those receptors likely help produce alcohol's pleasant lift, so blocking them takes the shine off a drink.
That endorphin system isn't only about the buzz, though. It's threaded through mood, gut, and energy, so turning its volume down can register early on as queasiness, a dull head, a low battery. For most people the system recalibrates within weeks — which is exactly why the common side effects tend to fade rather than pile up.
Will it make me sick if I drink?
No — and this is worth clearing up, because there is an alcohol medication designed to do exactly that, and people mix the two up. Disulfiram (Antabuse) blocks the breakdown of alcohol partway through, so a toxic byproduct called acetaldehyde builds up and leaves you flushed, pounding-hearted, and ill within minutes of drinking; its label frames it as a deterrent for people who have decided to stay away from alcohol entirely. Naltrexone is a different animal: its own label states plainly that it is not aversive therapy and does not cause a disulfiram-like reaction if you drink. Instead of punishing alcohol, it mutes the reward.
The third FDA-approved option, acamprosate, does yet another job: it leaves the reward system alone and instead helps re-steady brain chemistry that stays restless and off-balance after quitting, which is why it's used to help people who have already stopped stay stopped. A peer-reviewed overview of the three medicines lays out how genuinely different they are — deterrent, reward-blocker, re-stabilizer. So here's a simple sorting rule: feeling awful every time you drink on disulfiram is the design. Feeling awful on naltrexone whether or not you drink is a side effect — report it.
The serious ones — rare, but know them cold
Three things belong on your actually-watch-for-this list.
Your liver. The naltrexone label carries liver-related cautions, and heavy drinking has often already asked a lot of that organ. Watch for dark urine, yellowing of the skin or eyes, or a deep ache under the right ribs that doesn't ease. Many prescribers order liver blood tests before starting and again along the way — that's routine care, not a red flag. Any history of liver trouble belongs in the very first conversation.
Your mood. Some people notice anxiety, irritability, or a lower mood, usually mild and early. If it deepens instead of lifting — and especially if you have any thoughts of harming yourself — call or text 988 right away, and tell your prescriber what shifted.
A true allergic reaction. Rash, intense itching, swelling of the face or throat, trouble breathing: that's an emergency. Call 911.
One hard rule: opioids
Naltrexone and opioids don't mix, full stop. The label rules it out for anyone taking opioid painkillers, currently dependent on opioids, or in opioid withdrawal. The reason follows from the mechanism: naltrexone parks in the same receptors opioid medications need, so painkillers won't work while you're on it — and in someone with opioids still in their system, it can set off sudden, severe withdrawal.
The practical version: every clinician who treats you — including your dentist, and especially before any surgery — needs to know you take naltrexone, so pain control can be planned around it.
What helps while your body adjusts
A few moves that make the early weeks easier and the follow-up visit more useful:
- Food first: many people find the nausea settles when they take it with a meal — worth confirming with your prescriber rather than improvising.
- Keep a two-line log: each day, jot what you felt and roughly when. Two weeks of that turns "it's been rough" into a pattern a clinician can actually act on.
- Raise it early: side effects are a standard agenda item, not a confession. Prescribers expect the question and have answers ready.
- Don't just stop quietly: if a symptom makes you quit on your own, the whole medication conversation dies with it. Saying "this isn't working for me" keeps the options open — an adjustment, a different formulation, or a different medicine.
When it's more than a side-effect question
If vomiting won't settle, if any of the liver warning signs above appear, or if your mood keeps sliding, contact your prescriber promptly — same week, not next month. Those check-ins exist for exactly these moments.
One boundary worth stating, too: naltrexone is not a withdrawal treatment. If your real worry is what happens when you stop drinking — shaking, sweating, confusion, hallucinations, or a seizure after cutting back — that's a medical emergency in the making, and the answer is 911 or an emergency room, not a prescription question. Understanding alcohol withdrawal walks through what safe stopping looks like.
NIAAA counts 27.9 million people ages 12 and older with past-year alcohol use disorder in 2024, and about 2.1 million of them — 7.6% — received any alcohol treatment that year.
American Family Physician notes that most people with alcohol use disorder are never offered medication at all. That's a gap in access and awareness, not a verdict on the medicines — and it means that by researching side effects, you're already further into the question than most people ever get.
If you don't have a prescriber to bring this to, Clero connects you with a licensed clinician through telehealth who can go over your liver history, your other medications, and your goals, and help you decide whether naltrexone earns a place in your plan.
For related reading, see how naltrexone works, the naltrexone FAQ, and the broader medication for alcoholism overview.
Side effects are a real part of this decision, but for most people they're the temporary part. The pattern to remember is simple: the common ones fade, the serious ones announce themselves with specific signs, and all of them go better when you say something early.
This article is general education — not medical advice, a dosing guide, or a prescription. If you ever have thoughts of harming yourself, call or text 988. If cutting back on alcohol brings shaking, confusion, hallucinations, or a seizure, call 911 or go to an emergency room. For confidential treatment referrals, SAMHSA's National Helpline is 1-800-662-4357.
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