Short summary

The primary aim of this study is to investigate the analgesic effect of Low Dose Naltrexone compared to placebo in a randomized, double-blind placebo controlled cross over study. In addition, following clinical outcome parameters are registered; fatigue, daily level of function, sleep, side effects and physical and social level of activity. Additionally, experimental testing (Cold Pressor Test, Pressure Algometry, Heat-Capsaicin Test) is included for the analysis of the pain modulation system.

Rationale

Fibromyalgia (FM) is a chronic nociplastic, musculoskeletal disease with an unknown etiology characterized by widespread fluctuating pain, fatigue, low quality of sleep, and high incidences of depression and anxiety disorders. 2-8 % of the population in Europe, -including Denmark, suffer from FM, affecting women more frequently than men. The motivation of this study is the awareness of multiple side effects from existing recommended pharmacological opportunities such as antidepressants, anticonvulsants and opioids are not recommendable because of the pharmacokinetic and risk of addiction, tolerance and pain-aggravation. Other treatment options are therefor in demand by both patients and pain therapists. Since reports from small scale studies indicate analgesic efficacy of Low Dose Naltrexone (LDN) with patients experiencing few and mild side effects, our rationale for this study is to verify the potential of LDN in a study with a larger statistical power. The main purpose of this study, are to examine if LDN is associated with a significant higher analgesic efficacy and anti-inflammatory profile compared to placebo. Secondary outcome parameters are pressure algometry, fatigue, daily level of function, sleep, side effects and physical and social level of activity. Additionally, experimental testing (Cold Pressor Test, Pressure Algometry, Heat-Capsaicin Test) is included for the analysis of the pain modulation system. Blood samples are taken in measure pharmacokinetics of naltrexone and the main metabolite 6-β-naltrexone.

Description of the cohort

Adult men and women -All candidates are screened by a specialist in rheumatology and are required to meet the ACR's (American College of Rheumatology) criteria of FM

Data and biological material

Questionnaires -Quantitative experimental testing (Cold Pressor Test, Pressure Algometry, Heat-Capsaicin Test)

Collaborating researchers and departments

Department of Multidisciplinary Pain Clinic, Friklinikken Grindsted

• MD Anette Bendiksen, DMSc
• RN Lotte Marie Jensen, MSc
• RN Grete Tarp
• MSc. Pharm Trine Andresen, PhD

Department of Multidisciplinary Pain Clinic, Rigshospitalet

• Professor, MD Mads U. Werner, PhD, DMSc

Department of Biochemistry and Immunology, Lillebaelt Hospital

• Professor MD Jonna Skov Madsen, PhD

University of Southern Denmark

• Statistician, PhD-Student Torben Johansen