Fibromyalgia is a complex generalized and diffuse musculoskeletal chronic pain; and
pharmacological approaches are widely used to relieve pain and increase life quality. In this
context, low-dose naltrexone (LDN) was able to increase nociceptive threshold in patients
with fibromyalgia. Moreover, non-pharmacological techniques, like Transcranial Direct Current
Stimulation (tDCS), have been shown effective for pain management. This study aims to
evaluate the analgesic and neuromodulatory effect of combined LDN followed by tDCS in
fibromyalgia patients. This is a randomized, double-blinded, parallel,
placebo/sham-controlled trial, in which 92 (10% loss) women with fibromyalgia will be
included included and signed the informed consent. Patients will be allocated into 4 groups:
tDCS+LDN (n=21), Sham-tDCS+LDN (n=22), tDCS+Placebo (n=22), and Sham-tDCS+Placebo (n=21). LDN
or placebo (p.o.) intervention lasts 26 days, in the last five, tDCS will be applied (sham or
active, 20min, 2mA). Questionnaires assessed are: Sociodemographic, Visual Analog Pain Scale
(VAS), Pain Catastrophizing Scale (PCS), State-Trait Anxiety Inventory (STAI), Fibromyalgia
Impact Questionnaire (FIQ), Beck Depression Inventory (BDI-II), Chronic Pain Profile Scale
(CPP). Also, pain measures were taken: Pain Pressure Threshold (PPT) and Conditioned Pain
Modulation (CPM). Blood samples will be collected to analyze Brain Derived Neurotrophic
Factor (BDNF) serum levels.