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Latest News

Naltrexone Offers Novel Approach to Pain Relief

Posted: April 29, 2009

Why do many medications prescribed to treat fibromyalgia offer limited benefits? The answer may have something to do with the cells that the drugs target. All meds designed to treat pain, sleep, fatigue and cognition work by altering the chemical transmissions between one neuron and the next. But other cells, called microglia, work right along side your neurons and are capable of drastically altering the way your neurons function. What if your fibromyalgia symptoms are produced by microglial cells that have gotten out of control and are raising a ruckus in your nervous system?

This possibility was put to a preliminary test by Jarred Younger, Ph.D. and Sean Mackey, M.D., Ph.D., of Stanford University, who used low nightly doses of naltrexone in a small trial of ten fibromyalgia patients.* Naltrexone is commonly used at 10 to 20 times the dose to reduce drug cravings in addicts, but at high doses it also interferes with the body’s ability to fight pain. Yet in small quantities, naltrexone should not have much effect on pain relief, but it can quiet down microglial cells that could be at the root of your pain and possibly your other symptoms as well.

Six out of ten fibromyalgia patients in the study achieved greater than a 30 percent reduction in pain. It took about a month to achieve the maximum benefits from the drug. In fact, one 39-year-old woman who had been couch-bound went back to work as an interior decorator after the naltrexone reduced her fibromyalgia pain by more than 40 percent. Daytime fatigue was also relieved.

A trial of ten patients is small, and caution needs to be used when interpreting the results. However, if you are wondering if 4.5 mg per night of naltrexone might work for you, it may depend upon your erythrocyte sedimentation rate (ESR), a blood test used as a general marker of inflammation. Those patients who had the best response to naltrexone also had a slightly elevated erythrocyte sedimentation rate (ESR). The four patients who had low or normal ESRs did not appear to respond to the drug (e.g., their ESR was 20 mm/hr or less).

The American Fibromyalgia Syndrome Association (AFSA) funded Younger and Mackey over a year ago to conduct a blinded, placebo-controlled trial with 40 fibromyalgia patients. Each patient is serving as her own control in a crossover design study (they get a placebo for eight weeks and naltrexone for eight weeks in a blinded fashion). To validate the patient response with objective testing, pain thresholds will be measured every two weeks.

Low dose naltrexone (4.5 mg) may occasionally cause vivid dreams for the first few nights, but may be eased by backing down on the dose. For the most part, the drug is benign in terms of side effects. Naltrexone does have to be specially compounded in the low dose. The lowest commercially available dose is 50 mg. The monthly cost of compounded naltrexone is $40, and is inexpensive because its drug patent expired long ago.

The decision to try naltrexone is entirely up to you and your doctor. If you are relying upon an opioid for pain relief (even mild formulas such as tramadol), naltrexone will interfere with the opioid’s ability to treat your pain. People with low ESRs may not be good candidates for naltrexone, but if you do decide to test this novel form of treatment, be prepared to give it at least four weeks before you decide if it is working for you. The Fibromyalgia Network will report the results of the larger study as it becomes available.

* Younger J, Mackey S. Pain Medicine April 2009.

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