Home-based Transcranial Direct Current Stimulation (tDCS) Compared to Duloxetine:On-inferiority Clinical Trial (FIBROSTIM)

Participants will be randomized to receive 28 sessions of active anodal tDCS (2 mA) or sham, with the anode over the left M1 and the cathode over the right supraorbital area, for 20 minutes, combined with pain neuroscience education and physical exercises. Sessions will be self-administered at home, daily for 4 weeks. Electrodes (35 cm²) will be placed using neoprene caps (sizes S to XL), adjusted according to head circumference. Monitoring: the device records session time, duration, and adherence, interrupting the session if impedance exceeds 1 mA (5-second interval) or if current varies \>10%. Developed in partnership with HCPA's Biomedical Engineering, the device is licensed by UFRGS/HCPA and registered with ANVISA (No. 80079190028).

"Duloxetine (30 mg and 60 mg) will be purchased from a commercial pharmacy and fractionated by a compounding pharmacy, which will also prepare the placebo. Capsules will be transferred into standardized jars based on dosing schedule:~* Jar 01 (white cap): 7 capsules of 30 mg~* Jar 02 (green cap): 16 capsules of 60 mg~* Jar 03 (green cap): 42 capsules of 60 mg~* Jar 04 (white cap): 7 capsules of 30 mg Placebo and duloxetine capsules will be identical in appearance. Kits will be labeled with CAEE number, participant ID (RedCap), pharmacist and PI names, and storage/use instructions. Kits will be stored at the HCPA Pharmacy Service under controlled conditions and dispensed during visits AV1 (Jars 1 and 2), AV2 (Jar 3), and AV3 (Jar 4)."

Participants will be randomized to receive 28 sessions of active anodal tDCS (2 mA) anode over the left M1 and the cathode over the right supraorbital area, for 20 minutes

"Duloxetine (30 mg and 60 mg) will be purchased from a commercial pharmacy and fractionated by a compounding pharmacy, which will also prepare the placebo. Capsules will be transferred into standardized jars based on dosing schedule:~* Jar 01 (white cap): 7 capsules of 30 mg~* Jar 02 (green cap): 16 capsules of 60 mg~* Jar 03 (green cap): 42 capsules of 60 mg~* Jar 04 (white cap): 7 capsules of 30 mg Placebo and duloxetine capsules will be identical in appearance. Kits will be labeled with CAEE number, participant ID (RedCap), pharmacist and PI names, and storage/use instructions. Kits will be stored at the HCPA Pharmacy Service under controlled conditions and dispensed during visits AV1 (Jars 1 and 2), AV2 (Jar 3), and AV3 (Jar 4)."