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VIDEO: Calming microglia might control fibromyalgia



– Activated microglia may be a root cause of fibromyalgia, and bringing them back to a resting state an effective path to symptom relief.

Jarred Younger, PhD, is particularly interested in dextronaltrexone, the right-handed isomer of the drug commonly employed in addiction medicine, for calming microglia in fibromyalgia.

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Unlike the commercially available levo-naltrexone, which binds at both the mu-opioid receptor and Toll-like receptor 4 (TLR4), dextronaltrexone blocks only TLR4. Blocking this receptor interferes with the cells’ ability to recruit peripheral immune cells, which may enter the brain, release cytokines, and induce a proinflammatory environment. By targeting only TLR4 and sparing opioid receptors, treating fibromyalgia with dextronaltrexone would potentially leave open the possibility of coadministration with an opioid, Dr. Younger said in a video interview at the annual Congress of Clinical Rheumatology.

He already has investigated low-dose levo-naltrexone in a small positive crossover trial in 31 fibromyalgia patients. While taking the drug, patients reported significantly less pain and improved mood.

Dr. Younger also recently published a study suggesting that low-dose naltrexone actively improves peripheral proinflammatory cytokine levels.

The placebo-controlled crossover trial enrolled eight women with moderately severe fibromyalgia who took 4.5 mg naltrexone daily for 8 weeks. Compared with baseline, they had significantly reduced plasma levels of a variety of interleukin (IL) subtypes. Also reduced were interferon-alpha, transforming growth factor-alpha and -beta, TNF-alpha, and granulocyte-colony stimulating factor. Patients experienced a mean 15% reduction in fibromyalgia pain and an 18% reduction in overall symptoms.

But proving the drug’s method of action continues to be a challenge, he admitted. It’s not easy to observe microglial trafficking and cellular response to immune signaling in the brain.

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