Clinicians treating patients with fibromyalgia may want to consider low-dose naltrexone (LDN) as a treatment option, even if the appropriate dosage is still undetermined.

Presenting at the 32nd Annual Meeting of the American Academy of Pain Medicine (AAPM), Sean Mackey, MD, PhD, professor of anesthesiology at Stanford University, reviewed why he believes prescribing LDN can be an effective way to treat patients with fibromyalgia.

Typically prescribed for opioid dependence or alcohol dependence, LDN, a typical dose being 4.5mg/day, can be used to help patients with HIV/AIDS, autoimmune diseases, and central system disorders. Clinicians can also prescribe it to reduce symptom severity in patients with fibromyalgia.


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Using low doses of naltrexone will block microglia receptors without blocking opioid receptions on neurons.1 Patients undergoing treatment with LDN have reported improvements to their symptoms.2 Specifically, mechanical and heat pain thresholds are improved by the drug. The greatest reduction of symptoms in response to LDN occur in individuals with high sedimentation rates. 

Even though side effects of LDN are rare, and often described as described as minor and transient, they do include insomnia and vivid dreams. “I get patients who report to us that they get technicolor dreams,” he said. “Generally it’s not nightmares.”

Other benefits of using LDN: it is cheap, it is well-tolerated, and it is generic and of little interest to drug companies, he noted.

The appropriate dosage of LDN for patients with fibromyalgia is still unknown. “We have no idea whether it’s 4.5, or 6, or 3, and we need to have additional studies,” he said. There is also a lack of long-term safety data. 

“I think it’s a great option for you because it’s been so incredibly safe and easy to use,” he said. “In my experience, I either find people get dramatic results or they get nothing.”


Summary and Clinical Applicability

Fibromyalgia is a chronic pain disorder characterized by diffuse musculoskeletal pain, fatigue, sleep disturbance and cognitive impairment. A significant number of fibromyalgia patients do not respond adequately to the current drugs approved for fibromyalgia treatment by the Food and Drug Administration (pregabalin, milnacipran, duloxetine), thus there is a need to identify safe and effective adjunctive fibromyalgia pharmacotherapy. 

It is hypothesized that low dose naltrexone (LDN) causes transient blockade of opioid receptors centrally resulting in a rebound of endorphin function which may attenuate pain in fibromyalgia.3 Results presented at the 32nd Annual Meeting of the American Academy of Pain Medicine suggest that LDN may be an effective, highly tolerable and inexpensive treatment for fibromyalgia. 

Critical parameters such as dosing still need to be defined.  Other dosing schedules, such as twice a day, have not yet been explored in clinical studies. Proper dosing studies need to be performed to determine the therapeutic range of the drug and to identify a process for determining an individual’s optimal dosage.  Additionally little is known about the long-term safety of the drug when used chronically in low dosages.

Reference

1. Younger J, Mackey S. Fibromyalgia symptoms are reduced by low-dose naltrexone: a pilot study. Arthritis & Rheumatology. 2009;10(4):663-72. doi: 10.1111/j.1526-4637.2009.00613.

2.Younger J, Noor N, Mccue R, Mackey S. Low-dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double-blind, placebo-controlled, counterbalanced, crossover trial assessing daily pain levels. Arthritis Rheum. 2013;65(2):529-38.

3. Ramanathan S, Panksepp J, Johnson B. Is fibromyalgia an endocrine/endorphin deficit disorder?Is it low dose naltrexone a new treatment option? Psychosomatics 2012;53:591-4.

This article originally appeared on Clinical Pain Advisor