Methods
Participants
This clinical protocol and patient consent forms were designed following the revised Declaration of Helsinki and the Good Clinical Practice of the International Conference on Harmonization (ICH-GCP) and approved by the Ethics Committee of the School of Pharmaceutical Sciences of Ribeirão Preto and the School of Medicine of Ribeirão Preto, University of São Paulo (USP) (CAAE: 34175314.3.0000.5403). Thirty-two patients were invited to participate and provided written informed consent. The study was registered in Clinicaltrials.gov under the identifier NCT03047278.
Eligible subjects were adult patients (n=32), from 18 to 59 years old, with neuropathic pain with pain scores ≥ 4 on VAS. All patients were recruited from the Pain Ambulatory or Diabetes Ambulatory of the Clinical Hospital of the School of Medicine of Ribeirão Preto, University of São Paulo (FMRP-USP) or from the Health Basic Unity (UBS) Cuiabá of the FMRP-USP. The diagnosis of neuropathic pain was based on the presence of daily moderate to severe chronic pain in the extremities for more than 90 days and a score of 4 cm (or greater than 4 cm) on a 10 cm visual analogue pain scale (0 = no pain; 10 = worst possible pain) [45,46]. The diagnosis of diabetes was based on the criteria by the American Diabetes Association [18]. Only participants with DM2 diagnosis for more than 6 months were included. Exclusion criteria were creatinine clearance ≤ 30 mL/min, gastrointestinal diseases, history of alcohol or drug abuse and chronic use of medicines that interact with GBP. Three patients were excluded from the final analysis due to incomplete data.