Soin Therapeutics has been granted the Food and Drug Administration (FDA)’s Orphan Drug designation for the use of low dose naltrexone in the treatment of complex regional pain syndrome (CRPS).

According to the Company, anecdotal reports have suggested that naltrexone, an opioid antagonist, may alleviate symptoms associated with CRPS, a rare disorder characterized by severe, debilitating pain, swelling, and skin or bone structure changes.

“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,” explained Dr Amol Soin, the founder and CEO of Soin Therapeutics.

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Naltrexone is currently approved for the management of alcohol and opioid use disorders. Previous reports have shown that about one-tenth of 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 running a large-scale clinical trial and eventually FDA approval to help patients suffering from CRPS,” added Soin.

The FDA’s Orphan Drug designation is granted to medicines intended to treat or prevent rare diseases or disorders that affect fewer than 200,000 individuals.

While there is currently no FDA-approved treatment for CRPS, findings from small studies suggest benefits with bisphosphonates, gabapentin, short-course steroids, ketamine, and botulinum toxin A.


  1.  FDA grants Orphan Drug status to Soin Therapeutics for low dose naltrexone (LDN) to treat complex regional pain syndrome (CRPS). News release. September 9, 2021.
  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