Low-dose naltrexone as an orphan drug for complex regional pain syndrome

Soin Therapeutics has been granted orphan drug designation by the Food and Drug Administration (FDA) for the use of low-dose naltrexone to treat complex regional pain syndrome (CRPS).

According to the company, anecdotal reports suggest that naltrexone, an opioid antagonist, may relieve symptoms associated with CRPS, a rare condition characterized by severe, debilitating pain, swelling, and changes in the structure of the skin or bones.

“Low-dose naltrexone has unique properties to specifically support the CRPS disease cascade, including attenuating microglial cells involved in pain transmission, reducing proinflammatory cytokines, antagonism of toll-like receptor 4 (TLR4) and stimulation the release of endorphins, which are the body’s natural pain relievers, ”explains Dr. Amol Soin, Founder and CEO of Soin Therapeutics.

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Naltrexone is currently approved for the treatment of alcohol and opioid use disorders. Previous reports have shown that approximately one-tenth the dose used for these approved indications may be beneficial for patients with CRPS. The company is developing its own novel formulation of low dose naltrexone for evaluation. “We look forward to conducting a large-scale clinical trial and ultimately FDA approval to help patients with CRPS,” added Soin.

FDA orphan drug status is granted to drugs that are intended to treat or prevent rare diseases or disorders that affect fewer than 200,000 people.

Although there is currently no FDA-approved treatment for CRPS, the results of small studies suggest benefits with bisphosphonates, gabapentin, short-term steroids, ketamine, and botulinum toxin A.


  1. The FDA grants Soin Therapeutics orphan drug status for low-dose naltrexone (LDN) for the treatment of complex regional pain syndrome (CRPS). Press release. September 9, 2021. -regional-pain-syndrome-crps-301372111.html.
  2. Taylor SS, Noor N, Urits I, et al. Complex Regional Pain Syndrome: A Comprehensive Review. Pain and therapy. Published online June 24, 2021.

This article originally appeared on MPR


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