Effect of Duloxetine on the Serum BDNF in Fibromyalgia Patients and its Comparison with Non-Fibromyalgia Chronic Pain Disorders

Objectives: We sought to compare the serum BDNF level in patients with two different type of pain: nociplastic pain (FM) and non-FM nociceptive pain (non-FM NP). We also investigated the effect of Cymbalta® (duloxetine) antidepressant on serum BDNF in patients with FM and also assessing direction of BDNF changes relation to clinical parameters’ alteration.
Methods: This is a prospective study on 81 patients with FM diagnosis based on the 2016 ACR classification criteria and 23 patients with non-FM NP. Patients with FM underwent standardized FM treatment with duloxetine maximized up to 60 mg per day. Patients assessed by Revised Fibromyalgia Impact Questionnaire (FIQR), Short-Form Health Survey (SF-12), pain visualized analogue scale (pain VAS), Beck Depression Inventory-II (BDI-II), polysymptomatic distress scale (PSD) and serum BDNF measured at baseline and 4 weeks after treatment.
Results: There was non-significant difference in the adjusted BDNF level for depression in FM group rather than non-FM NP group. Surprisingly, Cymbalta decreased significantly serum BDNF level in FM patient with depression but not in FM patients without depression. Serum BDNF drop off was associated with improvement in fibromyalgianess, pain, depression and disease severity.
Conclusion: Not significant BDNF difference between nociplastic FM pain and pure nociceptive pain indicated peripheral BDNF is not a pathophysiological feature of FM. The decreased BDNF after Cymbalta treatment especially in depressed patients supports the role of BDNF in pain modulation probably through complex pathways that involved the psychobiological and plasticity of nervous system.