Naltrexone for Fibromyalgia

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Naltrexone is a medication used for the treatment of drug and alcohol addiction. It is a member of the drug class known as opiate antagonists, and works by decreasing the cravings for alcohol and blocking the effects of opioid medications and opioid street drugs (such as heroin). It does not prevent or relieve withdrawal symptoms. Naltrexone is marketed under the brand names ReVia and Depade. It is generally taken in tablet form once per day, and common side effects include the following: nausea, vomiting, stomach pain, stomach cramps, diarrhea, constipation, decreased appetite, headache, dizziness, anxiety, nervousness, irritability, tearfulness, insomnia, changes in energy level, drowsiness, muscle or joint pain, and rash. Serious side effects include confusion, hallucinations, blurred vision, and severe vomiting or diarrhea.

Naltrexone and Fibromyalgia

In the hunt for an ever-elusive cause of fibromyalgia, some researchers have hypothesized that certain endorphins within the body may somehow be associated with the distorted pain perception that afflicts most Fibromyalgia sufferers. Endorphins are a group of hormones that act as the body’s natural painkillers. Opiate pain medications mimic the actions of endorphins in the body, thereby relieving pain. Based on these assumptions, emerging research has investigated the use of naltrexone as a treatment for fibromyalgia-related pain in recent years.

The first such study was published in 2009 by Younger et al. This randomized controlled study (considered the “gold standard” for research study design) treated 10 women with fibromyalgia and 10 control subjects (matched to the age and gender of the fibromyalgia patients) with 50mg naltrexone or placebo (one at each of two sessions). All participants were evaluated to determine any changes in their sensitivity to heat, cold, and pain. At the outset of the study, those patients in the fibromyalgia group had more symptoms, greater sensitivity to sensory stimuli, more symptoms associated with opioid withdrawal, and lower pain and cold tolerances than the controls. Following administration of naltrexone, neither group experienced changes in cold or pain sensitivity, nor did anyone in either group experience positive changes in self-reported withdrawal symptoms or mood. The authors concluded that the findings of their study did not support a role for endorphin activity in the symptoms of women with fibromyalgia (Younger et al., 2009).

A subsequent study, also led by Younger, evaluated the effectiveness of low-dose (4.5 mg) naltrexone in the treatment of fibromyalgia symptoms among 10 women who met the American College of Rheumatology (ACR) diagnostic criteria for fibromyalgia and who were not taking any opioid pain medications. In this study, each participant was followed for an initial 2 week baseline period, then received treatment with a placebo for 2 weeks, then received naltrexone for 8 weeks. After treatment was finished, each participant was also followed for a 2 week “wash-out” period during which they received no drug or placebo. Using a handheld computer, each participant recorded the severity of their symptoms on a daily basis, and also visited the laboratory every 2 weeks to be tested for mechanical, heat, and cold pain sensitivity. At the conclusion of the study, the researchers found that all participants experienced a reduction in their fibromyalgia symptoms, including improvements in mechanical and heat pain thresholds. Side effects were rare in this study, and included insomnia and vivid dreams. Based on their findings, the authors concluded that naltrexone might be an effective, tolerable, and inexpensive option for the treatment of fibromyalgia (Younger & Mackey, 2009).

Most recently, Ramanathan et al., (2012) presented a case report of a 37 year old male who presented with a two-year history of widespread pain, eye pain, sleep difficulties, concentration problems, and anxiety. This individual also reported a family history of adult-onset chronic pain (in particular his mother and brother). The patient had previously received diagnoses of carpal tunnel syndrome, hypoparathyroidism, and fibromyalgia. Following unsuccessful treatment with naproxen, amitriptyline (Elavil), and milnacipran (Savella) due to unwanted side effects, the authors placed this patient on the following regimen of naltrexone: 1mg for 2 nights, 2mg for 2 nights, and then 4.5mg for a 2 week period. After a 2 week rest period, treatment with naltrexone resumed at the 4.5mg dose for a 14 week period. Within one week of treatment, the patient reported a significant improvement in tender point pain, and after one month, dull pain previously reported in his neck and back had improved considerably. Self-reported measures of pain severity steadily declined throughout his course of treatment, while his self-reported mood and quality of life improved. The authors conclude that low-dose naltrexone may be a safe, effective, and affordable option for treating fibromyalgia-related symptoms (Ramanathan et al., 2012).

 

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References

1.        U.S. National Library of Medicine; PubMed Health. Naltrexone. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0000853/  Accessed September 17, 2012; Last revision: February 1, 2009.

2.        Younger JW, Zautra AJ, Cummins ET. Effects of naltrexone on pain sensitivity and mood in fibromyalgia: no evidence for endogenous opioid pathophysiology. PLoS One. 2009;4(4):e5180.

3.        Younger J, Mackey S. Fibromyalgia symptoms are reduced by low-dose naltrexone: a pilot study. Pain Med. 2009;10(4):663-72.  Ramanathan S, Panksepp J, Johnson B. Is Fibromyalgia An Endocrine/Endorphin Deficit Disorder? Is Low Dose Naltrexone a New Treatment Option? Psychosomatics. 2012 Apr 3.Epub ahead of print.

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