Pharmacotherapy of Fibromyalgia: Focus on Duloxetine

Abstract

Context: Fibromyalgia syndrome (FMS) is a frequent medical condition characterized by chronic widespread pain and reduced pain threshold. Associated symptoms include fatigue, non restorative sleep, and psychological distress. As usual in medicine, even if the pathogenesis is unclear, some treatments are useful to help patients. Objectives: Tricyclic antidepressants were the first drugs used to treat FMS. More recently, among serotonin-norepinephrine reuptake inhibitors, duloxetine was approved by US Food and Drug Administration to treat FMS. Duloxetine is used for the management of major depressive disorder, neuropathic pain, generalized anxiety disorder, and stress incontinence. In the pharmacotherapy of fibromyalgia, a focus is presented on the drug duloxetine. Results: Mechanism of action, metabolism and pharmacokinetic profile are presented. Clinical studies of Duloxetine showed an acceptable efficacy for this chronic condition: Number Need to Treat (NTT) of 4.7 to 9.9, through two 3-month placebo-controlled trials and two 6-month trials. Evaluation criteria are discussed. Safety of this medication has been found to be satisfactory, with nausea as the most common adverse event, in almost 20% of cases. Conclusion: Treatment algorithm for duloxetine is presented inside FMS treatment strategy. With duloxetine, it is important to start low and increase slowly to prevent or minimize adverse events: 30 mg/day up to 60 mg/day in the second week and if necessary up to 90–120 mg/day. It is possible to treat for 3 to 6 months, possibly up to 12 months. The drug could be decreased 2 to 4 weeks before stopping, with regular assessments during this time. International recommendations insist on multimodal treatments: drug and non drug. Also effective for anxiety and depression, duloxetine ranks among the first place drugs for FMS.