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Low-Dose Naltrexone (LDN) as a Fibromyalgia & Chronic Fatigue Syndrome Treatment


Updated October 20, 2009

What LDN Is:

Naltrexone is a drug that, at a normal dose of 50 to 100 mg, blocks the effects of opioids.

At very low doses, however, some researchers believe the drug may be beneficial in people with fibromyalgia and chronic fatigue syndrome; autoimmune/inflammatory diseases, including multiple sclerosis and Crohn's disease; and other immune-related diseases, like HIV/AIDS.

LDN is an inexpensive drug that's already on the market, which has fueled excitement about its possible uses.

How LDN Works:

Researchers don't yet understand the drug's exact mechanism of action. Some researchers theorize that LDN blocks certain receptors in the nervous system that cause symptoms of fibromyalgia and chronic fatigue syndrome. It's also believed to reverse inflammation.

LDN for Fibromyalgia:

A Stanford University pilot study tested LDN on 10 women with fibromyalgia. LDN appeared to improve pain thresholds (the point at which sensation becomes pain) and lower overall symptoms. Stanford is now preparing larger studies on LDN for fibromyalgia (in adults) and juvenile fibromyalgia.

While this is the first study of LDN for fibromyalgia, the drug has been prescribed off-label for several years.

LDN for Chronic Fatigue Syndrome:

So far, LDN has not been studied for chronic fatigue syndrome. However, some doctors and patients say they've used LDN successfully. As with fibromyalgia, LDN is sometimes prescribed off-label for chronic fatigue syndrome.

LDN Dosage:

For use in treating fibromyalgia or chronic fatigue syndrome, naltrexone is generally given in doses of 5mg or less.

LDN Side Effects:

While LDN appears to be well-tolerated, known side effects of naltrexone include:

  • Dizziness & syncope (fainting)
  • Headache
  • Insomnia
  • Anxiety & nervousness
  • Sleepiness & fatigue
  • Nausea, vomiting, diarrhea, abdominal pain/cramping, decreased appetite
  • Injection site pain & swelling
  • Joint pain
  • Excessive muscle contraction
  • Upper respiratory tract infection
  • Sore throat

In the Stanford study, side effects were reported as rare, mild and transient.

People with kidney or liver disease may need special tests or dosages to safely take LDN. This drug may be harmful to an unborn baby. It not known whether LDN passes into breast milk.


Pain medicine. 2009 Apr 22. (Epub ahead of print) "Fibromyalgia Symptoms Are Reduced by Low-Dose Naltrexone: A Pilot Study."

Stanford University School of Medicine. "Low Dose Naltrexone for the Treatment of Fibromyalgia"

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