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Low-Dose Naltrexone (LDN) for Fibromyalgia & Chronic Fatigue Syndrome

What Research Shows


Updated June 27, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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, complex regional pain syndrome 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 It 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.

Some evidence suggests that it works as an anti-inflammatory in the central and peripheral nervous system, possibly by inhibiting the activity of specialized cells called microglia.

Learn more about inflammation in these illnesses:

For Fibromyalgia:

A series of Stanford University studies has shown positive results -- as much as a 30 percent decline in symptoms compared to placebo. Researchers say results are best in people with higher sedimentation rates, which indicates an inflammatory response in the body.

Results also indicate that the drug is well tolerated.

However, these studies have all been small and more work is done before we know how safe and effective LDN is for this condition.

LDN is not FDA approved for fibromyalgia but is sometimes prescribed off-label.

For Chronic Fatigue Syndrome:

So far, LDN has not been studied for chronic fatigue syndrome. However, some doctors and patients say they've used it successfully.

With recent evidence pointing to the possibility of neuroinflammation in chronic fatigue syndrome and LDN's possible impact on inflammation in the nervous system, we may be seeing why this is an effective treatment for some.

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.

The effects attributed to this low dosage are not seen at higher doses.

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 studies, 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 it passes into breast milk.


Younger J, Mackey S. Pain medicine. 2009 May-Jun;10(4):663-72. "Fibromyalgia Symptoms Are Reduced by Low-Dose Naltrexone: A Pilot Study."

Younger J, et al. Arthritis and rheumatism. 2013 Feb;65(2):529-38. Low-dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double-blind, placebo-controlled, counterbalanced, crossover trial assessing daily pain levels.

Younger J, Parkitny L, McLain D. Clinical rheumatology. 2014 Apr;33(4):451-9. The use of low-dose naltrexone (LDH as a novel anti-inflammatory treatment for chronic pain.

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