The FDA's patient page on unapproved use of approved drugs, or "off label" use, says that once the FDA approves a drug, healthcare providers generally may prescribe the drug for an unapproved use when they judge that it is medically appropriate for their patient. The page also says that FDA has not determined that the drug is safe and effective for the unapproved use. Reviews describe low-dose naltrexone as an off-label use, and that is the background for this guide.
What the FDA says about off-label use
The FDA page frames the choice as a shared one. It says: "If you and your healthcare provider decide to use an approved drug for an unapproved use to treat your disease or medical condition, remember that FDA has not determined that the drug is safe and effective for the unapproved use."
That wording is about approved drugs used for unapproved uses in general. It does not name naltrexone.
Where naltrexone fits
The label for the FDA-approved naltrexone hydrochloride 50 mg tablet states that the tablets are indicated in the treatment of alcohol dependence and for the blockade of the effects of exogenously administered opioids.
A 2026 narrative review abstract states that "Naltrexone is prescribed off-label at low doses, typically 0.5-6.0 mg, for a variety of therapeutic indications." A 2018 review abstract says low-dose naltrexone "has been used off-label for treatment of pain and inflammation in multiple sclerosis, Crohn's disease, fibromyalgia, and other diseases." Those are descriptions of use. They are not statements about approval or results for any condition.
What MedlinePlus and two drug labels list for those three conditions
This table reports what MedlinePlus health topic pages and two drug labels list. It is not a recommendation, and it does not compare any option with low-dose naltrexone.
| Question | What the source says |
|---|---|
| What does MedlinePlus say about fibromyalgia treatment? | There is no cure for fibromyalgia, so treatment focuses on relieving the symptoms. Providers usually use a combination of treatments, including medicines, lifestyle changes, talk therapy, and complementary therapies. The medicines it lists include "Certain antidepressants and anti-seizure medicines, which may help with pain or sleep problems." |
| Which fibromyalgia medicines do drug labels name? | The Savella (milnacipran hydrochloride) prescribing information says Savella is indicated for the management of fibromyalgia. The Lyrica (pregabalin) prescribing information, in its indications and usage section, lists management of fibromyalgia and management of neuropathic pain associated with spinal cord injury. |
| What does MedlinePlus say about Crohn's disease? | There is no cure for Crohn's disease, but treatments can decrease inflammation in the intestines, relieve symptoms, and prevent complications. Treatments include medicines, bowel rest, and surgery. |
| What does MedlinePlus say about multiple sclerosis? | There is no cure for MS, but treatment can help manage symptoms and slow the disease. It lists disease-modifying medicines, which help slow MS and reduce relapses and may be taken as pills, injections, or infusions. |
When the sources say to call for emergency help
The sources used here do not say when to see a clinician about low-dose naltrexone. They do give emergency and poison-control steps. These come from the 50 mg tablet label and from three general pages on opioids, poisoning and mental health. None of them says what to do at a low dose.
- The 50 mg tablet label tells prescribers to emphasize the importance of calling 911 or getting emergency medical help in all cases of known or suspected opioid overdose, even if an opioid overdose reversal agent is administered.
- The National Institute on Drug Abuse, on its opioids page, says: "If you suspect someone is overdosing, call 911." The page also says several signs can indicate that a person is experiencing an overdose and requires immediate medical attention, including unconsciousness or inability to wake up and slow or shallow breathing or difficulty breathing.
- A general MedlinePlus page on poisoning says: "If you suspect someone has been poisoned, call your local poison control center at 1-800-222-1222 right away." The page does not mention naltrexone.
- The National Institute of Mental Health, on a page about suicide prevention, says: "In life-threatening situations, call 911."
What this does not tell you
This guide does not say whether low-dose naltrexone is right for any person or condition, and it does not diagnose anything. The label statements above are about the 50 mg tablet. The emergency and poison-control statements come from general pages and are not about naltrexone. None of them says what to do at a low dose.
The table lists what MedlinePlus says about three conditions and what two drug labels say about fibromyalgia. It does not say that low-dose naltrexone belongs on any of those lists, and it does not rank the options. The review abstracts describe use. They do not report that any approach works.
The FDA page describes the decision to use an approved drug for an unapproved use as one made by the patient and the healthcare provider together. A licensed provider decides whether any naltrexone product suits a person.