Circulating Brain-Derived Neurotrophic Factor (BDNF) and Multimodal Opioid-Based Analgesia in Chronic Pain: Plasma BDNF as an Indicator of Pain Intensity and Neuropathic Pain

Background: Brain-derived neurotrophic factor (BDNF) is crucial in the nociception and mechanisms underlying chronic and neuropathic pain. The evaluation of circulating BDNF in patients with multimodal analgesia has not been reported previously. We hypothesized that opioid-based multi-analgesia induces changes in BDNF values and that BDNF correlates with pain intensity in neuropathic pain. Methods: Adult patients who met low back pain (LBP) criteria and received multimodal opioid-based therapy were included. The control group included patients with LBP who did not receive any pharmacotherapy. Plasma measurements obtained with the ELISA test were analyzed. The study was registered at Clinical Trials.gov (NCT04227223). Results: Patients with multimodal opioid-based analgesia had significantly higher BDNF values compared to the monotherapy: 3.6 ng/mL vs. 2.7 ng/mL, p = 0.01. No statistical differences were observed compared to the non-pharmacologically treated group: 3.6 ng/mL vs. 5.0 ng/mL, p = 0.75. The median BDNF values were lowest in the mild-pain group, and significant differences were observed between the severe and moderate-pain groups (p = 0.006) and the mild-pain group (p = 0.0001). BDNF was significantly higher in the neuropathic-pain group compared to the group of patients without neuropathic pain (p = 0.0005). A significant correlation was demonstrated between the BDNF and numerical rating pain score (NRS) in the neuropathic-pain component (rho = 0.6, p = 0.001). Conclusions: Multimodal opioid-based analgesia decreases plasma BDNF concentrations less than opioid monotherapy, which offers an opportunity to limit opioid-induced adverse effects. BDNF influences pain intensity and predicts neuropathic pain in multimodal opioid-based analgesia.