Pharmacotherapy of Fibromyalgia
Although the diagnosis of fibromyalgia is best made by considering only the symptoms of widespread pain and tenderness, most patients experience other symptoms, including fatigue, stiffness, disordered sleep, and cognitive dysfunction.[25] Disorders such as anxiety and depression, migraine headaches, and irritable bowel syndrome are also common in patients with fibromyalgia.[26] Studies of pharmacologic treatment of fibromyalgia have addressed the issue of comorbid disorders in different ways. Some studies have explicitly excluded patients with depression or other comorbidities, while others have included such patients and analyzed treatment effects in both the entire study population and subgroups with and without comorbidities.
A number of tools have been developed to help clinicians and researchers measure the effects of different interventions for fibromyalgia. Clinical trials evaluating treatments for fibromyalgia symptoms have used a wide variety of measures. A brief description of some of the most important measurement tools is provided in Table 1.
An understanding of the nuances of fibromyalgia treatment trials is important in interpreting the study results. One nuance is the high rate of patient dropout in fibromyalgia trials. In trials lasting three months or longer, 30% or more of enrollees may drop out;[39] this may introduce bias into the data analysis, as patients may leave trials for reasons that are directly related to the study such as lack of effectiveness or intolerable adverse effects of the drugs being evaluated. Investigators have used various strategies to address this issue. Initially, studies used an observed-cases (OC) methodology, in which only data on patients completing a trial were included in the analysis; trials of older agents, such as tricyclic antidepressants (TCAs) and cyclobenzaprine, most often used OC methodology. More recently, last-observation-carried-forward (LOCF) and baseline-observation-carried-forward (BOCF) methods have become standard;[40] with those methods, dropouts are included in the analysis by imputing the LOCF or the BOCF for those patients. In practice, it appears that most contemporary investigators prespecify LOCF or BOCF as the process for obtaining the study endpoint and subsequently reanalyze the data by conducting sensitivity analyses in several ways. In the reanalysis, dropouts are often added to the final data using pessimistic assumptions (e.g., that all patients who left the trial early did so for lack of efficacy) in order to clarify whether the trial findings are statistically robust.[40,41]
Currently, three medications available in the United States (pregabalin, duloxetine, and milnacipran) are labeled for the treatment of fibromyalgia. In addition, a number of other medications have been studied for the treatment of fibromyalgia. There is wide variability in the extent and rigor of the available evidence.
Am J Health Syst Pharm. 2011;68(14):1307-1319. © 2011 American Society of Health-System Pharmacists, Inc.
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Cite this: Pharmacotherapy of Fibromyalgia - Medscape - Jul 15, 2011.
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