Q: Can low-dose naltrexone treat back pain and other conditions?
A: Its safety and efficacy are unknown. Most of the research on low-dose naltrexone has been lab or animal studies or else small human studies that have methodological problems.
Naltrexone is a prescription drug that was approved by the FDA decades ago to treat opioid addiction at daily doses of 50 to 100 milligrams. But lately websites have been touting low doses of the drug as a treatment for everything from cancer, fibromyalgia, and rheumatoid arthritis to multiple sclerosis, Crohn’s disease, and irritable bowel syndrome. The lower dose is usually 1 to 5 milligrams a day.
It’s theorized that naltrexone has anti-inflammatory effects that may be responsible for some of the claimed benefits, since many conditions involve inflammation. Other notions are that low-dose naltrexone may cause a rebound in the body’s own production of pain-relieving opioids or that it may suppress overactivity of the immune system (as occurs with autoimmune diseases).
A 2014 review paper published in Clinical Rheumatology concluded that, though there’s some evidence of anti-inflammatory properties, clinical trials on low-dose naltrexone are still in their infancy.
In 2014, the Cochrane Collaboration evaluated two studies on low-dose naltrexone for Crohn’s disease and concluded that there wasn’t enough evidence to determine safety or efficacy. In 2015, a report from the Norwegian Institute of Public Health evaluated the research on low-dose naltrexone’s use for dozens of conditions and found that the drug’s safety and efficacy could not be determined because of the studies’ methodological problems, short duration, and small number of subjects.
Naltrexone is not FDA-approved for inflammatory or chronic pain conditions or any other medical disorders, but some doctors prescribe it “off-label” for such conditions, especially if patients ask for it. Though the drug doesn’t have the well-known potential risks of nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen, its long-term effects are not known. The most commonly reported side effects are vivid dreams and headaches. There have also been anecdotal reports of high heart rate (tachycardia) and anxiety, and some animal studies suggest that frequent use may increase tumor growth.
Bottom line: Larger, better-designed clinical trials on low-dose naltrexone are needed before we could recommend it for any off-label purposes.
Also see What to Do About Low Back Pain.