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Fibromyalgia is an idiopathic, chronic, nonarticular pain syndrome that affects 2-4% of the general population in the US and is predominantly seen in women.[1,2] Although their use as a diagnostic tool in clinical practice has been questioned,[3,4] the 1990 American College of Rheumatology criteria[3] defined fibromyalgia as widespread aching pain for at least 3 months and hyperalgesia at a minimum of 11 of the 18 specified muscle-tendon sites. Possible accompanying symptoms included fatigue, sleep disturbances, morning stiffness, parathesias, headache and anxiety.[2]
Although the pathophysiology of fibromyalgia is unclear and no widely accepted model of the disorder currently exists, the syndrome appears to involve a dysfunction of neuroendocrine and autonomic nervous system function.[5] In particular, dysfunction of the serotonin and norepinephrine systems is a potential mechanism for the pain experienced by patients with fibromyalgia. Genetic and family influences, environmental triggers (e.g. co-morbid disease, infections or physical trauma) and psychological factors (e.g. somatization, anxiety, depression) may also contribute to the development of the syndrome.[2,5]
There is no known cure for fibromyalgia; however, nonpharmacological (e.g. exercise, cognitive behavioural therapy and patient education) and pharmacological therapies are recommended to help reduce pain and treat other symptoms.[6,7] The use of antidepressant medications has been associated with improvements in pain, depression, fatigue, sleep disturbances and health-related quality of life in patients with fibromyalgia.[8,9] Dual serotonin and norepinephrine reuptake inhibitors such as duloxetine (Cymbalta®), milnaciprin and venlafaxine that enhance serotonin and norepinephrine neurotransmission may reduce pain and improve mood-related symptoms in patients with fibromyalgia.
This article reviews the pharmacology, therapeutic efficacy and tolerability of duloxetine (available in delayed-release capsules for oral use) in patients with fibromyalgia. A discussion of the use of duloxetine in other indications approved in the US[10] or EU,[11] namely acute and maintenance treatment of major depressive disorder, acute treatment of generalized anxiety disorder, neuropathic pain associated with diabetic peripheral neuropathy and female stress urinary incontinence (in the EU only[11]) is beyond the scope of this article.
Medical literature on the use of duloxetine in patients with fibromyalgia was identified using Medline and EMBASE, supplemented by AdisBase (a proprietary database of Wolters Kluwer Health |" Adis). Additional references were identified from the reference lists of published articles.
1. Pharmacodynamic Profile
* The exact mechanisms of the central...