Low-Dose Naltrexone Use for Patients with Chronic Regional Pain Syndrome: A Systematic Literature Review.

Background: Complex regional pain syndrome is a rare, neuropathic disorder that affects fewer than 200,000 individuals in the United States annually. Current treatments often focus on pain management and fall short of relieving symptoms of pain and dystonia in patients.

Objective: The goal of this systematic qualitative review is to evaluate the evidence for the use of low-dose naltrexone in the treatment of chronic pain syndromes.

Study Design: This is a systematic review.

Methods: PubMed, Embase, and Web of Science were searched for articles containing the keywords "low-dose naltrexone" AND ("pain" OR "chronic pain" OR "fibromyalgia" OR "complex regional pain syndrome" OR "neuropathic pain" OR "nociceptive pain") between 1950 and July 17, 2020. A total of 30 publications were systematically reviewed. Exclusion criteria were articles that were unavailable in English, focused on acute pain only, and evaluated only animal models. Case studies were included for the purposes of our qualitative review.

Results: Out of 29 articles, we reviewed 11 prospective studies, 10 case studies, 3 systematic reviews, 2 retrospective studies, 2 simulation models, and one combination study. Articles focused on chronic pain syndromes as well as painful rheumatologic disorders and neurological disorders. We found that low-dose naltrexone treatment was positively associated with symptom relief in patients experiencing chronic pain, dystonia, and sleep disturbances.

Limitations: Due to the limited number of available articles focusing on the treatment of complex regional pain syndrome with low-dose naltrexone, the majority of studies analyzed focused on other chronic pain syndromes.

Conclusions: There is a need for additional prospective and interventional studies addressing the use of low-dose naltrexone in the treatment of complex regional pain syndrome symptoms.