By Pat Anson, PNN Editor

Low-dose naltrexone (LDN) is already being used to treat a wide variety of chronic pain conditions, from fibromyalgia and interstitial cystitis to Ehlers Danlos syndrome and temporomandibular joint disorder (TMJ). Some doctors believe the drug may even be useful treating symptoms of a condition so painful it’s been called the “suicide disease.”

Soin Therapeutics, a small pharmaceutical startup based in Ohio, announced this month it has been granted orphan drug status from the Food and Drug Administration to explore using LDN as a treatment for Complex Regional Pain Syndrome (CRPS), a disorder of the nervous system that causes severe, intractable nerve pain.

"Obtaining Orphan Status from the FDA is an important milestone step for us at Soin Therapeutics. We look forward to running a large-scale clinical trial and eventually FDA approval to help patients suffering from CRPS," Dr. Amol Soin, the founder and CEO of Soin Therapeutics, said in a statement.

Currently, naltrexone is only approved by the FDA as a treatment for substance abuse. In 50mg doses, the drug blocks opioid receptors in the brain and decreases the desire to take opiates or alcohol. But in smaller doses of 5mg or less, some patients have found LDN to be a surprisingly effective pain reliever.

How LDN works is not fully understood, but supporters believe the drug modulates the immune system, reduces inflammation and stimulates the production of endorphins, chemicals produced by the body that reduce pain and anxiety.

It's important to note that because naltrexone is an opioid antagonist, it should never be taken with opioid medication – even in small doses -- because it may cause severe withdrawal.

"Low Dose Naltrexone has unique properties to specifically help the disease cascade of CRPS including attenuation of microglial cells involved in pain transmission, reduction of proinflammatory cytokines, antagonism of the Toll-like receptor 4 (TLR4), as well as stimulating release of endorphins which are the body's natural pain killers,” said Soin, who is a practicing pain management physician.

“Basically, this drug seems very well suited to treat several mechanisms of the disease process. All those properties would seemingly be quite helpful in CRPS patients. Best of all, this is a non-addicting and non-sedating drug that could be a new way to treat complex regional pain syndrome."

Soin Therapeutics hopes to develop a novel formulation of LDN and submit an Investigational New Drug application to the FDA before starting a clinical trial.

Because the patent on naltrexone expired decades ago, it’s a generic and cheap drug – perhaps the main reason it is not more widely used as a pain reliever. There is little incentive for pharmaceutical companies to market LDN or conduct expensive clinical trials to prove its effectiveness in treating pain.

Patients interested in trying LDN often encounter doctors who refuse to prescribe it “off label” or don’t know anything about it. The LDN Research Trust includes a list of LDN-friendly doctors and pharmacies on its website.