Naltrexone is not available over the counter. It is a prescription-only medication in the United States, classified “Rx only” by the FDA. You need a prescription from a licensed healthcare provider to obtain it in any form, whether that’s the standard 50 mg tablet or the injectable version. The same is true in other major countries, including the UK, Canada, and Australia.
Why Naltrexone Requires a Prescription
Naltrexone works by blocking the receptors in your brain that respond to opioids and, to a lesser extent, alcohol. This blocking action is what makes it useful for treating alcohol use disorder and preventing opioid relapse, but it’s also what makes unsupervised use risky. If someone takes naltrexone while opioids are still in their system, it can trigger severe, sudden withdrawal symptoms. Before prescribing it, a provider needs to confirm you’ve been opioid-free for a sufficient period, typically 7 to 10 days for most opioids.
Liver health is another reason medical oversight matters. Naltrexone carries a risk of liver toxicity, though researchers aren’t entirely sure whether the drug itself causes liver damage or whether it’s more common simply because many people prescribed naltrexone already have underlying liver conditions from heavy alcohol use. Either way, the drug is contraindicated in people with acute hepatitis, liver failure, or severe liver insufficiency. Your provider will check your liver function before you start and monitor it periodically while you’re on the medication. If liver problems develop, the medication may need to be stopped.
How to Get a Prescription
Any licensed physician, nurse practitioner, or physician assistant can prescribe naltrexone. Unlike some other medications used in addiction treatment, naltrexone does not require a special waiver or certification for the prescriber. This makes access relatively straightforward compared to other options in the same category.
Telehealth has made the process even simpler. Several online platforms now connect patients with providers who can evaluate you, order necessary lab work, and write a prescription remotely. The medication is then filled at a standard pharmacy. If you’re using naltrexone for alcohol use disorder, some providers follow the Sinclair Method, where you take a pill about one hour before drinking rather than taking it daily. This still requires a prescription and medical guidance.
What About Low-Dose Naltrexone (LDN)?
Low-dose naltrexone, commonly called LDN, uses much smaller amounts of the same drug (usually 1.5 to 4.5 mg instead of the standard 50 mg). People use it off-label for conditions like fibromyalgia, chronic pain, and certain autoimmune disorders. LDN also requires a prescription. Because no manufacturer sells naltrexone in such small doses, your doctor must write a prescription specifically for a compounding pharmacy, which custom-prepares the medication in the lower dose.
Compounding pharmacies that handle LDN can be local or mail-order, but both require a valid prescription. If your doctor isn’t familiar with LDN, published research on its use for conditions like fibromyalgia can help open that conversation.
What to Expect at Your Appointment
When you see a provider about naltrexone, the visit typically covers your substance use history (if applicable), current medications, and liver health. You’ll likely need blood work to check liver enzymes before starting. If you’ve recently used opioids, your provider will want confirmation that enough time has passed to safely begin the medication. For people using naltrexone for alcohol use disorder, there’s no required detox period from alcohol, though your provider may want to assess your overall health first.
Common side effects include nausea, headache, dizziness, and fatigue, particularly in the first few days. These tend to ease as your body adjusts. The more serious concern, liver toxicity, is why ongoing monitoring matters and why this medication isn’t sold without a prescription.
Cost and Insurance Coverage
Generic naltrexone tablets are widely available and relatively affordable, often under $50 per month without insurance. Many insurance plans and Medicaid cover it, especially when prescribed for alcohol or opioid use disorder. The injectable form, given once a month, is significantly more expensive but is also covered by many plans. Compounded low-dose naltrexone is rarely covered by insurance, and out-of-pocket costs vary by pharmacy.