Stopping naltrexone does not cause physical withdrawal symptoms. Unlike opioid medications, naltrexone is not addictive and your body won’t go through the kind of painful detox associated with quitting drugs like oxycodone or heroin. However, stopping naltrexone does carry real risks, particularly a heightened vulnerability to opioid overdose and the return of cravings for alcohol or opioids. What happens next depends on why you were taking it, how long you were on it, and what form you were using.
Why Naltrexone Doesn’t Cause Withdrawal
Naltrexone works by blocking opioid receptors in the brain. It’s an antagonist, meaning it sits on the receptor and prevents anything from activating it. This is the opposite of how addictive opioids work. Drugs like heroin and oxycodone are agonists that flood those receptors with stimulation, and your brain adapts by demanding more. When you stop an agonist, the sudden absence creates withdrawal. Naltrexone never stimulates those receptors in the first place, so there’s nothing for the brain to miss when it’s gone.
After your last 50 mg oral dose, the blockade on opioid receptors fades gradually. Research published in The Journal of Nuclear Medicine found that the half-time for receptor occupancy to return to baseline is 72 to 108 hours, meaning it takes roughly three to four days for half the blocking effect to wear off. The drug itself clears faster: naltrexone has an elimination half-life of about 4 hours, while its active breakdown product lingers for around 13 hours. But the receptor-level effects outlast the drug’s presence in your blood.
The Overdose Risk After Stopping
This is the most dangerous consequence of discontinuing naltrexone, and it catches people off guard. While you’re on naltrexone, your opioid receptors become more sensitive because they haven’t been activated in weeks or months. Pharmacologists call this “upregulation.” Your brain essentially grows extra receptor sites or makes existing ones more responsive to compensate for the blockade.
If you stop naltrexone and then use opioids, even at a dose you previously tolerated, the effect can be dramatically stronger than expected. The Mayo Clinic warns that this increased sensitivity can lead to overdose and serious, potentially fatal complications. The dose of heroin or prescription painkillers that felt normal before treatment could now be enough to stop your breathing.
This risk is highest in the first days and weeks after stopping, before your receptor sensitivity normalizes. There’s no precise timeline for when your tolerance “resets,” which makes any opioid use during this window unpredictable and dangerous.
What Happens With the Injectable Form
If you were receiving Vivitrol (the extended-release injection given once a month), the timeline is longer. Vivitrol has an elimination half-life of 5 to 10 days, and it generally takes 25 to 50 days for the drug to fully leave your system after the last injection. For most people, the therapeutic blocking effect lasts about a month, which is why injections are scheduled every four weeks.
This means you can’t simply decide to stop on a particular day. After your last injection, naltrexone will continue working for weeks as it slowly releases from the injection site. The same overdose risk applies once the blockade finally wears off, but the transition is more gradual than with the oral form.
Return of Cravings and Relapse Rates
For people taking naltrexone to manage opioid or alcohol use disorder, the most common experience after stopping is that cravings come back. Naltrexone reduces the rewarding effects of alcohol and blocks the high from opioids, so when the medication leaves your system, those substances regain their pull.
The relapse numbers are sobering. A pilot study from NYU Langone Health tracked people released from jail who had been treated with extended-release naltrexone. Among those who received the injection, 38 percent relapsed within one month of release. In the control group that didn’t receive the medication, 88 percent relapsed in the same timeframe. While this study involved a specific population, it illustrates how powerfully naltrexone’s absence can affect relapse risk.
For alcohol use disorder specifically, no guidelines establish a firm stopping point. SAMHSA suggests treatment should last at least 6 months to a year. The American Psychiatric Association recommends individualizing the decision based on factors like relapse history, disorder severity, and how well the medication is working. Because a significant proportion of patients relapse within the first year, many clinicians lean toward maintaining treatment for at least 12 months before considering discontinuation.
Low Dose Naltrexone Is Different
If you’ve been taking low dose naltrexone (LDN), typically 1.5 to 4.5 mg for chronic pain or autoimmune conditions, the picture is simpler. According to the LDN Research Trust, there is no need to taper the dose, and patients should not experience withdrawal symptoms when stopping. LDN is generally well tolerated, and discontinuation is straightforward.
The main concern with stopping LDN is that whatever symptoms it was managing, whether pain, fatigue, or inflammation, will likely return. This isn’t withdrawal; it’s the underlying condition reasserting itself without the medication’s support. One uncommon exception: people with an extensive history of opioid use before starting LDN may experience withdrawal-like symptoms upon stopping, possibly because their internal endorphin system is already compromised. For most people, though, stopping LDN is uncomplicated.
Do You Need to Taper?
For standard-dose naltrexone (50 mg daily), there is no established medical need to taper. Because the drug doesn’t produce physical dependence, abrupt cessation is the clinical norm. This is a sharp contrast with many other psychiatric and addiction medications, where gradual dose reduction is essential to avoid rebound symptoms.
That said, stopping naltrexone is a decision that benefits from planning, not because of withdrawal risk, but because of what comes after. The protective effects of the medication disappear, cravings return, and opioid sensitivity increases. Ideally, stopping happens as part of a broader treatment plan that includes behavioral support, counseling, or other strategies to maintain the progress you’ve made while on the medication.