Cost-utility and Physiological Effects of LDN in Patients With Fibromyalgia

Background: Low-dose naltrexone (LDN) may be useful in managing the pathologies that alter inflammatory markers, such as Crohn's disease or fibromyalgia (FM). The anti-inflammatory effect of LDN should be produced through the inhibition of Toll-like receptor 4 activity expressed in the membrane of various immune system cells (e.g. microglia). Conversely, due to a rebound effect, LDN could exercise an analgesic effect that strengthens the endogenous inhibitory system. According to this hypothesis, the low-intensity and intermittent blocking of the opioid receptors generated by LDN should induce a compensatory mechanism that should facilitate an increase in the production of endogenous opioids and greater sensitivity of the system to their effects. To date, the effects of LDN in patients with FM have been evaluated through crossover studies that have yielded promising results. Given that the studies conducted up to now have had small sample sizes and crossover designs, and given that there are still no studies in which its potential cost-utility is assessed, studies with greater methodological rigor and larger samples are necessary to confirm the effectiveness of LDN in FM. Jointly evaluating the effectiveness and cost-utility, the changes in metabolites in certain areas of the brain, and systemic inflammatory markers potentially linked to the etiopathogenesis of FM, should allow us to gain a more detailed knowledge of the neurobiological mechanisms underlying the effectiveness of LDN in this population. Objectives: To evaluate the effectiveness and safety of LDN in patients with FM and analyse its cost-utility both from the government and the healthcare perspective at 1-year follow-up. Brain metabolites and systemic inflammatory biomarkers will be included to evaluate neurobiological mechanisms behind LDN therapeutic effects. Design: Randomized, Controlled Trial. Centre: Parc Sanitari Sant Joan de Déu (St. Boi de Llobregat, Spain). Participants: 120 patients with