Predictors of treatment response to serotonin and noradrenaline reuptake inhibitors in fibromyalgia

Abstract

Introduction: Fibromyalgia (FM) is often comorbid with anxiety and depression. The serotonin and noradrenalin reuptake inhibitors (SNRI) are used in treatment of FM, depression, anxiety, but are ineffective in a substantial number of patients. Recently it was reported that FM is associated with impaired glucose metabolism.

Objectives: The aim was to explore the associations between insulin resistance, psychiatric comorbidity and treatment response to SNRI in FM.

Patients and methods: 59 FM patients and 30 healthy controls (HC) were recruited. Patients were classified as treatment non-responsive if SNRI treatment resulted in <30% reduction in reported pain. All participants were examined by a physician and filled self-report questionnaires. Blood samples were drawn to assess fasting glucose and insulin levels and calculate HOMA-IR. Multivariable logistic regression models were constructed to analyze the associations between insulin resistance, psychiatric comorbidity and the lack of response to treatment with SNRI.

Results: Non-responders (FM [T-]) had higher BMI, fasting insulin and HOMA-IR levels than responders (FM [T+]) and HC. FM [T+] patients did not significantly differ from HC in the BMI, levels of fasting glucose, fasting insulin, HOMA-IR. Depression, anxiety and personality disorders were significantly more prevalent in FM [T-] than in FM [T+]. Insulin resistance, depression, anxiety and personality disorders were predictors of the lack of treatment response to SNRI. The effect of BMI on lack of response to SNRI treatment was fully mediated by the insulin resistance.

Conclusions: Significant differences in clinical, metabolic parameters and psychiatric comorbidities could explain the treatment response to SNRI in FM patients.