While there have been no clinical trials yet using LDN in CRPS, there has been scientific literature published—in the form of a large literature review, a retrospective chart review, and several case reports.

In July 2021, a large cross-institutional research collaboration published an article "Low-Dose Naltrexone Use for Patients with Complex Regional Pain Syndrome: A Systematic Literature Review" which summarized and assessed the quality of the available evidence for the use of LDN in treating chronic pain syndromes, including complex regional pain syndrome. They reported finding that low-dose naltrexone treatment was positively associated with symptom relief in patients experiencing chronic pain, dystonia, and sleep disturbances.

Previously, in April 2016, a retrospective chart review was published in the Journal of Pain. Twenty-seven patients with chronic pain, including some with CRPS, were treated with LDN 4.5 mg daily. They were asked to complete symptom surveys between 31 to 60 days after starting treatment and then again between 61 and 90 days. Patients taking LDN reported “significantly lower average pain scores, lower “lowest” pain scores, and improved physical function”. Depression scores were also significantly reduced and physical function improved. LDN was reported as being well-tolerated.

In addition to those studies, case reports have also been published by doctors describing what happened when they used LDN to treat patients with CRPS. Also in July 2021, Dr. Amol Soin reported success using LDN to treat one patient with pediatric CPRS. In another report published in the International Journal of Pharmaceutical Compounding in February 2016, LDN “dramatically improved the patient’s pain symptoms”.

Two other case reports were described in the Journal of Neuroimmune Pharmacology in January 2013:

1. Regarding one patient, a 48 year old male who developed CRPS with severe skin changes, the clinicians reported that, after two months of taking LDN, “he recovered from his flares more quickly, felt more energetic, and tolerated pain better. He became physically more active and his sleep improved significantly. His spasms stopped and he was able to walk without a cane”.
2. Regarding the other patient, a 12 year old girl, she had repeated dislocations of her right shoulder and ankle and subsequently developed CRPS. After being on 4.5 mg daily for one month, her pain scores dropped to 3 to 5 out of 10. She had less sensitivity to pain, touch and temperature change. At the time of publication of the report, she had been on LDN for 18 months with no side effects.