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Fibromyalgia and Related Conditions

      Abstract

      Fibromyalgia is the currently preferred term for widespread musculoskeletal pain, typically accompanied by other symptoms such as fatigue, memory problems, and sleep and mood disturbances, for which no alternative cause can be identified. Earlier there was some doubt about whether there was an “organic basis” for these related conditions, but today there is irrefutable evidence from brain imaging and other techniques that this condition has strong biological underpinnings, even though psychological, social, and behavioral factors clearly play prominent roles in some patients. The pathophysiological hallmark is a sensitized or hyperactive central nervous system that leads to an increased volume control or gain on pain and sensory processing. This condition can occur in isolation, but more often it co-occurs with other conditions now being shown to have a similar underlying pathophysiology (eg, irritable bowel syndrome, interstitial cystitis, and tension headache) or as a comorbidity in individuals with diseases characterized by ongoing peripheral damage or inflammation (eg, autoimmune disorders and osteoarthritis). In the latter instance, the term centralized pain connotes the fact that in addition to the pain that might be caused by peripheral factors, there is superimposed pain augmentation occurring in the central nervous system. It is important to recognize this phenomenon (regardless of what term is used to describe it) because individuals with centralized pain do not respond nearly as well to treatments that work well for peripheral pain (surgery and opioids) and preferentially respond to centrally acting analgesics and nonpharmacological therapies.

      Abbreviations and Acronyms:

      CNS (central nervous system), FM (fibromyalgia), IBS (irritable bowel syndrome), NSAID (nonsteroidal anti-inflammatory drug), TMJD (temporomandibular joint disorder)
      CME Activity
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      Learning Objectives: On completion of this article, you should be able to (1) understand the three underlying mechanisms of chronic pain; (2) recognize centralized pain, either as a distinct entity or as a co-morbidity with other underlying pain mechanisms; (3) treat chronic pain based on the underlying mechanisms operative in each patient rather than based on the disease that is purported to be causing the pain.
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      In their editorial and administrative roles, William L. Lanier, Jr, MD, Terry L. Jopke, Kimberly D. Sankey, and Nicki M. Smith, MPA, have control of the content of this program but have no relevant financial relationship(s) with industry.
      Dr Clauw has performed consulting services for and/or served on scientific advisory boards of Pfizer, Lilly, Forest Laboratories, Johnson & Johnson, Purdue Pharma, Nuvo, Cerephex, Tonix, Iroko, Takaeda, Cerephex, IMC, Zynerba, and Samumed. He has received grant support from Pfizer, Forest, Merck, Nuvo, and Cerephex.
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      Clinicians often encounter individuals who present with pain that they cannot adequately explain on the basis of the degree of damage or inflammation noted in peripheral tissues. This typically prompts an evaluation for the cause of pain. If no cause is found, these individuals are often given a diagnostic label that merely connotes that they have chronic pain in a region of the body without an underlying mechanistic cause (eg, chronic low back pain, headache, and temporomandibular joint disorder [TMJD]). In other cases, the label given alludes to an underlying pathologic abnormality that may or may not be responsible for the individual’s pain (eg, endometriosis and facet syndrome). In other instances, the patients may be told that there is nothing wrong with them, advised that the disorder is “all in their head,” and given a label such as “somatizer” without being offered any treatment.
      Fibromyalgia (FM) is the currently preferred term for widespread musculoskeletal pain for which no alternative cause can be identified. Every subspecialist sees the same individuals, typically because these individuals present with pain in the region of the body the subspecialist specializes in. Gastroenterologists see the very same patients and focus on their gastroenterological symptoms and often use the terms such as functional gastrointestinal disorder, irritable bowel syndrome (IBS), nonulcer dyspepsia, or esophageal dysmotility to explain the patients’ symptoms. Urologists focus on their genitourinary symptoms and use terms such as interstitial cystitis or chronic prostatitis, and gynecologists use terms such as vulvodynia, vulvar vestibulitis, and endometriosis. Until recently these unexplained pain syndromes perplexed researchers, clinicians, and patients.
      We have come to understand that although individuals sometimes have only one of these idiopathic pain syndromes over the course of their lifetime, more commonly individuals with one of these entities will have many, and their family members also have high rates of pain in many regions of the body. Many terms have been used to describe these co-occurring syndromes and symptoms, such as functional somatic syndromes, somatization disorders, allied spectrum conditions, chronic multisymptom illnesses, and medically unexplained symptoms. Although some of these individuals will have comorbid psychiatric conditions, and these are often blamed by physicians as the cause of these otherwise unexplained pains, most individuals who have these conditions do not have a definable psychiatric disorder. There is now much evidence that these syndromes are clearly different and separable from depression and anxiety and have different (yet strong) genetic underpinnings. A hallmark of these conditions (eg, FM, IBS, TMJD, and headache) is that individuals display diffuse hyperalgesia (increased pain to normally painful stimuli) and/or allodynia (pain to normally nonpainful stimuli). This and many other pieces of evidence suggest that these individuals have a fundamental problem with augmented pain or sensory processing (ie, an increased gain setting) in the central nervous system (CNS) rather than a pathologic abnormality confined to the region of the body in which the person is currently experiencing pain.
      Even if a practitioner has a problem with considering FM as a discrete disorder, it is critical to understand the diagnostic and therapeutic importance of centralization of pain as exemplified by a typical patient with FM. Once this phenomenon is recognized, it helps determine what types of treatments will work (centrally acting analgesics and nondrug therapies) and, just as importantly, what will not (opioids and surgery).

      Overview

      Fibromyalgia is generally considered to be the second most common “rheumatic” disorder, behind osteoarthritis. Depending on the diagnostic criteria used, the prevalence in the population ranges from 2% to 8%.
      • Wolfe F.
      • Ross K.
      • Anderson J.
      • Russell I.J.
      • Hebert L.
      The prevalence and characteristics of fibromyalgia in the general population.
      • Jones G.T.
      • Atzeni F.
      • Beasley M.
      • et al.
      The prevalence of fibromyalgia in the general population: a comparison of the american college of rheumatology 1990, 2010, and modified 2010 classification criteria.
      • Vincent A.
      • Lahr B.D.
      • Wolfe F.
      • et al.
      Prevalence of fibromyalgia: a population-based study in Olmsted County, Minnesota, utilizing the Rochester Epidemiology Project.
      The diagnostic criteria for FM published in 1990 require chronic widespread pain plus a certain number of tender points to make the diagnosis. According to this definition, FM was an almost exclusively female disease because women have many more tender points than do men (population-based studies suggest that women are 10 times as likely to have 11 tender points as do men
      • Wolfe F.
      • Ross K.
      • Anderson J.
      • Russell I.J.
      Aspects of fibromyalgia in the general population: sex, pain threshold, and fibromyalgia symptoms.
      ). The new diagnostic criteria for FM published in 2010 and 2011 no longer require performing a tender point count to make the diagnosis and instead ask about the constellation of nonpain somatic symptoms that are typically present in addition to widespread pain (eg, fatigue, sleep disturbance, memory, and mood problems). By using either of these criteria, substantially more men are diagnosed, with the female/male ratio being approximately 2:1 (instead of 9:1 with the 1990 criteria).
      • Vincent A.
      • Lahr B.D.
      • Wolfe F.
      • et al.
      Prevalence of fibromyalgia: a population-based study in Olmsted County, Minnesota, utilizing the Rochester Epidemiology Project.
      This female/male ratio is similar to those seen for almost all chronic pain conditions.
      • McBeth J.
      • Jones K.
      Epidemiology of chronic musculoskeletal pain.
      Fibromyalgia can develop at any age, including in childhood. It occurs in relatively equal frequency in different countries, cultures, and ethnic groups; there is no evidence that this condition occurs at increased rates in industrialized countries and cultures.
      • Jones G.T.
      • Atzeni F.
      • Beasley M.
      • et al.
      The prevalence of fibromyalgia in the general population: a comparison of the american college of rheumatology 1990, 2010, and modified 2010 classification criteria.
      Nearly all individuals eventually diagnosed with FM have several bouts of chronic pain in other regions of the body earlier in their life. A typical presentation is that of an individual who begins having regional pain conditions and/or somatic symptoms or syndromes earlier in life and finally progresses to having widespread pain later in life and receives this diagnosis. The prevalence of any (regional or widespread) chronic musculoskeletal pain in the population is approximately 30%, so identifying any patient who has had multiple episodes of chronic pain in different areas of their body over the course of their lifetime is an important clinical clue. This disorder often begins in childhood or adolescence, and individuals who eventually go on to develop FM are more likely to experience headaches, dysmenorrhea, TMJD, chronic fatigue, IBS and other functional gastrointestinal tract disorders, interstitial cystitis/painful bladder syndrome, endometriosis, and other regional pain syndromes (especially back and neck pain).
      • Hudson J.I.
      • Pope H.G.
      The concept of affective spectrum disorder: relationship to fibromyalgia and other syndromes of chronic fatigue and chronic muscle pain.
      • Aaron L.A.
      • Buchwald D.
      A review of the evidence for overlap among unexplained clinical conditions.
      What often looks to one health care provider as a new episode of acute or subacute pain is in fact simply the latest region of the body experiencing pain.
      • Warren J.W.
      • Howard F.M.
      • Cross R.K.
      • et al.
      Antecedent nonbladder syndromes in case-control study of interstitial cystitis/painful bladder syndrome.
      Because of this, many experts in the pain field have begun to believe that especially these “centralized” pain states are best thought of as a single lifelong disorder that begins in adolescence or young adulthood and merely tends to manifest in different regions of the body over time.
      • Williams D.A.
      • Clauw D.J.
      Understanding fibromyalgia: lessons from the broader pain research community.
      • Tracey I.
      • Bushnell M.C.
      How neuroimaging studies have challenged us to rethink: is chronic pain a disease?.
      • Woolf C.J.
      Central sensitization: implications for the diagnosis and treatment of pain.
      This knowledge might be particularly important for surgeons and proceduralists to integrate into clinical decision making because these individuals have much higher rates of surgical procedures performed to eliminate pain (eg, hysterectomy and back surgery),
      • Wolfe F.
      • Anderson J.
      • Harkness D.
      • et al.
      A prospective, longitudinal, multicenter study of service utilization and costs in fibromyalgia.
      and perhaps not surprisingly, data are beginning to emerge that this phenotype is a risk factor for individuals who fail to respond to peripherally directed procedures. Table 1 depicts that FM is the prototypical centralized pain state, differentiating it from other pain mechanisms (eg, nociceptive and neuropathic) that are typically easier to identify by clinicians.
      Table 1Underlying Mechanisms Operative in Chronic Pain States
      There are 3 underlying pain mechanisms: nociceptive, neuropathic, and centralized. It is important to assess every patient with chronic pain for each of these mechanisms, because any of the 3 can be present in any given patient. The diseases at the bottom of the figure are classic examples of each type of pain, but we now realize that all chronic pain states are mixed pain states, in which (within each disease) any of the 3 mechanisms might be present. It is particularly common to see centralized pain co-occur with either nociceptive or neuropathic pain.
      Copyright © (2014) American Medical Association. All rights reserved.
      Peripheral (nociceptive)NeuropathicCentralized
      • Pain due to inflammation or mechanical damage in tissues
      • Nonsteroidal anti-inflammatory drugs and opioids are responsive
      • Responds to procedures
      • Classic examples
        • Acute pain due to injury
        • Osteoarthritis
        • Rheumatoid arthritis
        • Cancer pain
      • Damage or entrapment of peripheral nerves
      • Responds to both peripheral and centralized pain therapies
      • Entrapment responds to surgery or injection
      • Classic examples
        • Diabetic neuropathic pain
        • Postherpetic neuralgia
      • Characterized by central disturbance in pain processing (diffuse hyperalgesia/allodynia)
      • Responsive to central nervous system–acting drugs altering neurotransmitters involved in pain, sleep, and mood disturbances
      • Classic examples
        • Fibromyalgia
        • Irritable bowel syndrome
        • Temporomandibular joint disorder
        • Tension headache
      a There are 3 underlying pain mechanisms: nociceptive, neuropathic, and centralized. It is important to assess every patient with chronic pain for each of these mechanisms, because any of the 3 can be present in any given patient. The diseases at the bottom of the figure are classic examples of each type of pain, but we now realize that all chronic pain states are mixed pain states, in which (within each disease) any of the 3 mechanisms might be present. It is particularly common to see centralized pain co-occur with either nociceptive or neuropathic pain.
      In addition to patients with FM who have a lifetime history of chronic pain, their families often have a history of chronic pain. First-degree relatives of patients with FM are 8.5 times as likely to have this condition as do the family members of controls and also have high rates of other chronic pain states.
      • Arnold L.M.
      • Hudson J.I.
      • Hess E.V.
      • et al.
      Family study of fibromyalgia.
      The strong familial predisposition to pain is shared by many chronic pain conditions, and recently there has been an expansion of knowledge about the strong predisposing role of genetic factors in leading to chronic pain states.
      • Woolf C.J.
      Central sensitization: implications for the diagnosis and treatment of pain.
      • Holliday K.L.
      • McBeth J.
      Recent advances in the understanding of genetic susceptibility to chronic pain and somatic symptoms.
      Many of the genes that have been identified to date to play a role in increasing or decreasing the frequency of chronic pain states, or of pain sensitivity, are involved in regulating the breakdown or binding of neurotransmitters that modulate pain sensitivity. The facts that pain sensitivity is polygenic and that different individuals develop increased pain sensitivity because of imbalances or altered activity of many different neurotransmitters likely, in part, explain the therapeutic issue found with nearly all currently available analgesics (they work either fairly well or not at all in a given individual). Twin studies suggest that approximately 50% of the risk of developing FM and related conditions such as IBS and headache is genetic and 50% environmental.
      • Kato K.
      • Sullivan P.F.
      • Evengård B.
      • Pedersen N.L.
      A population-based twin study of functional somatic syndromes.
      The environmental factors that are most likely to trigger the development of FM are various types of “stressors,” typically that involve acute pain for at least a few weeks. Fibromyalgia or similar illnesses can be triggered by certain types of infections
      • Buskila D.
      • Atzeni F.
      • Sarzi-Puttini P.
      Etiology of fibromyalgia: the possible role of infection and vaccination.
      (eg, Epstein-Barr virus, Lyme disease, Q fever, and viral hepatitis), trauma
      • McLean S.A.
      • Diatchenko L.
      • Lee Y.M.
      • et al.
      Catechol O-methyltransferase haplotype predicts immediate musculoskeletal neck pain and psychological symptoms after motor vehicle collision.
      (motor vehicle collisions), or deployment to war.
      • Lewis J.D.
      • Wassermann E.M.
      • Chao W.
      • Ramage A.E.
      • Robin D.A.
      • Clauw D.J.
      Central sensitization as a component of post-deployment syndrome.
      Psychological stress is but one such stressor that can trigger this complex symptom.
      Fibromyalgia is also commonly seen as a comorbidity in other chronic pain conditions such as osteoarthritis, rheumatoid arthritis, and lupus. Approximately 10% to 30% of individuals with these established rheumatic disorders meet criteria for FM.
      • Phillips K.
      • Clauw D.J.
      Central pain mechanisms in rheumatic diseases: future directions.
      This phenomenon had previously been termed secondary fibromyalgia. However, a well-accepted term used for this phenomenon is central sensitization, which means that these individuals have centralized their pain or have central sensitization. This term is most appropriate when CNS factors likely play a prominent role in amplifying or magnifying pain as well as in leading to other comorbid somatic symptoms such as fatigue, memory problems, and sleep and mood disturbances.
      • Phillips K.
      • Clauw D.J.
      Central pain mechanisms in rheumatic diseases: future directions.
      This term does not mean that ongoing peripheral nociceptive input does not contribute to this individual’s pain (ie, central and peripheral factors are better considered to be “additive” rather than mutually exclusive). The term central sensitization is sometimes also used to describe this phenomenon, but many believe that this particular term should be reserved for the original and specific spinal mechanism that was identified and called by this name, rather than the more general phenomenon we now believe can result via a multitude of different spinal and supraspinal mechanisms.
      • Woolf C.J.
      Central sensitization: implications for the diagnosis and treatment of pain.
      • Woolf C.J.
      • Thompson S.W.
      The induction and maintenance of central sensitization is dependent on N-methyl-d-aspartic acid receptor activation: implications for the treatment of post-injury pain hypersensitivity states.
      Regardless of the semantic term used, it is becoming increasingly important to identify this phenomenon because emerging evidence suggests that therapies that work best for peripheral nociceptive pain (eg, nonsteroidal anti-inflammatory drugs [NSAIDs], opioids, injections, and surgical procedures) are less likely to be effective in these individuals.
      • Woolf C.J.
      Central sensitization: implications for the diagnosis and treatment of pain.
      The physiological hallmark of centralized pain, central sensitization, or FM is augmented CNS pain processing. This was originally identified in FM by noting that these patients are diffusely tender to palpation. The scientific terms for this phenomenon are diffuse hyperalgesia and allodynia. In the absence of an identifiable diffuse peripheral inflammatory process involving body tissues, diffuse hyperalgesia and allodynia strongly suggests that the CNS (ie, spinal cord and brain) is somehow augmenting pain processing. In 1990 when the original criteria for FM were first published, the feature of diffuse tenderness was incorporated into the diagnostic criteria, which required that an individual had a certain number of tender points (≥11), in addition to chronic widespread pain, to qualify for this diagnosis.
      • Wolfe F.
      • Smythe H.A.
      • Yunus M.B.
      • et al.
      The American College of Rheumatology 1990 Criteria for the Classification of Fibromyalgia; report of the Multicenter Criteria Committee.
      Subsequent studies using more sophisticated measures of experimental pain testing reported that individuals with FM are more tender throughout the body, not just in the 18 regions considered to be tender points.
      • Petzke F.
      • Gracely R.H.
      • Park K.M.
      • Ambrose K.
      • Clauw D.J.
      What do tender points measure? Influence of distress on 4 measures of tenderness.
      • Petzke F.
      • Clauw D.J.
      • Ambrose K.
      • Khine A.
      • Gracely R.H.
      Increased pain sensitivity in fibromyalgia: effects of stimulus type and mode of presentation.
      These initial observations that individuals with FM were diffusely tender led to subsequent functional, chemical, and structural brain neuroimaging studies, which gave the best “objective” evidence that the pain in FM and related pain amplification syndrome is “real.”
      • Harris R.E.
      • Clauw D.J.
      How do we know that the pain in fibromyalgia is “real”?.
      These methods such as functional magnetic resonance imaging clearly demonstrate that when individuals with FM are given a mild pressure or heat stimulus that most individuals would feel as “touch” rather than “pain,” they experience pain and similar brain activation patterns in brain areas involved in pain processing.
      • Gracely R.H.
      • Petzke F.
      • Wolf J.M.
      • Clauw D.J.
      Functional magnetic resonance imaging evidence of augmented pain processing in fibromyalgia.
      • Cook D.B.
      • Lange G.
      • Ciccone D.S.
      • Liu W.C.
      • Steffener J.
      • Natelson B.H.
      Functional imaging of pain in patients with primary fibromyalgia.
      A more recent advance in the use of functional magnetic resonance imaging is to look at the extent brain regions are “connected” to each other, that is, simultaneously activated (or deactivated).
      • Ploner M.
      • Lee M.C.
      • Wiech K.
      • Bingel U.
      • Tracey I.
      Prestimulus functional connectivity determines pain perception in humans.
      Studies have shown that individuals with FM have increased connectivity between brain regions involved in increasing pain transmission and decreased connectivity to key antinociceptive regions.
      • Napadow V.
      • LaCount L.
      • Park K.
      • As-Sanie S.
      • Clauw D.J.
      • Harris R.E.
      Intrinsic brain connectivity in fibromyalgia is associated with chronic pain intensity.
      • Napadow V.
      • Kim J.
      • Clauw D.J.
      • Harris R.E.
      Decreased intrinsic brain connectivity is associated with reduced clinical pain in fibromyalgia.
      • Jensen K.B.
      • Loitoile R.
      • Kosek E.
      • et al.
      Patients with fibromyalgia display less functional connectivity in the brain’s pain inhibitory network.
      • Jensen K.B.
      • Kosek E.
      • Petzke F.
      • et al.
      Evidence of dysfunctional pain inhibition in fibromyalgia reflected in rACC during provoked pain.
      Other imaging techniques have been used to identify the neurotransmitter abnormalities that may be driving the pain amplification seen in FM and other chronic pain disorders. Together with previous studies that had examined levels of neurotransmitters in the cerebrospinal fluid, these neurotransmitter plus imaging studies give us an insight into likely pathogenic mechanisms in FM and centralized pain states. Figure 1 demonstrates the neurotransmitter systems that are generally believed to exert influences on CNS pain processing and indicates that FM increases in neurotransmitters that augment pain or sensory perception (eg, glutamate or nerve growth factor) and decreases in neurotransmitters that generally inhibit pain or sensory processing (eg, serotonin, norepinephrine, or γ-aminobutyric acid). Adjacent to each neurotransmitter are the pharmacological therapies that are thought to be working via these mechanisms.
      Figure thumbnail gr1
      Figure 1Central nervous system (CNS) neurotransmitters influencing pain. These neurotransmitters set the gain or volume control on the CNS pain processing. The CNS (spinal cord and brain) set the gain on pain processing and can act to either facilitate or inhibit pain transmission. The neurotransmitter systems on the left have a tendency to increase or facilitate pain transmission, whereas those on the right generally inhibit pain transmission. The arrows indicate the direction of the abnormality in levels of that neurotransmitter in fibromyalgia. Nearly all neurotransmitter systems that increase the gain are increased in fibromyalgia, whereas nearly all the systems that generally decrease the gain are decreased. The endogenous opioid system is the exception, with increases in endogenous opioid activity in fibromyalgia. This may be one reason why opioids appear to be less effective in fibromyalgia. Adjacent to each neurotransmitter are the drug classes that are effective in fibromyalgia and likely exert their effects at least in part via that neurotransmitter system. GABA = γ-aminobutyric acid; SNRI = serotonin norepinephrine reuptake inhibitor.
      For example, Harris and colleagues have used proton spectroscopy to probe other neurotransmitters. Several groups have shown that brain concentrations of the body’s major excitatory neurotransmitter, glutamate, increase in pain-processing regions such as the insula in FM.
      • Harris R.E.
      Elevated excitatory neurotransmitter levels in the fibromyalgia brain.
      Drugs such as pregabalin and gabapentin likely work in part in FM by reducing glutamatergic activity.
      • Maneuf Y.P.
      • Hughes J.
      • McKnight A.T.
      Gabapentin inhibits the substance P-facilitated K(+)-evoked release of [(3)H]glutamate from rat caudial trigeminal nucleus slices.
      Conversely, proton spectroscopy has recently been used to demonstrate low levels of one of the body’s major inhibitory neurotransmitters, γ-aminobutyric acid.
      • Foerster B.R.
      • Petrou M.
      • Edden R.A.
      • et al.
      Reduced insular γ-aminobutyric acid in fibromyalgia.
      This likely accounts for the efficacy of drugs such as γ-hydroxybutyrate, or even low doses of daily alcohol, in FM.
      • Russell I.J.
      • Holman A.J.
      • Swick T.J.
      • Alvarez-Horine S.
      • Wang Y.G.
      • Guinta D.
      Sodium Oxybate 06-008 FM Study Group
      Sodium oxybate reduces pain, fatigue, and sleep disturbance and improves functionality in fibromyalgia: results from a 14-week, randomized, double-blind, placebo-controlled study.
      • Kim C.H.
      • Vincent A.
      • Clauw D.J.
      • et al.
      Association between alcohol consumption and symptom severity and quality of life in patients with fibromyalgia.
      These imbalances between excitatory and inhibitory neurotransmitters are not diffusely noted in brain structures and seem to be confined to brain regions that are known to be involved in pain or sensory processing, such as the insula,
      • Craig A.D.
      How do you feel? Interoception: the sense of the physiological condition of the body.
      • Brooks J.C.
      • Tracey I.
      The insula: a multidimensional integration site for pain.
      which is concordant with the notion that there is a global problem with sensory hyperresponsiveness that is partly responsible for the pathophysiology of FM and related conditions.
      • Yunus M.B.
      Fibromyalgia and overlapping disorders: the unifying concept of central sensitivity syndromes.
      • Ablin K.
      • Clauw D.J.
      From fibrositis to functional somatic syndromes to a bell-shaped curve of pain and sensory sensitivity: evolution of a clinical construct.
      The same group has used positron emission tomography imaging to identify a neurotransmitter system that appears to be working paradoxically in FM: the endogenous opioid system. Although this system is generally thought to be antinociceptive, several studies suggest that endogenous opioid function might be increased in FM, with positron emission tomography showing evidence of decreased mu-opioid receptor availability in FM.
      • Wood P.B.
      • Schweinhardt P.
      • Jaeger E.
      • et al.
      Fibromyalgia patients show an abnormal dopamine response to pain.
      • Harris R.E.
      • Clauw D.J.
      • Scott D.J.
      • McLean S.A.
      • Gracely R.H.
      • Zubieta J.K.
      Decreased central mu-opioid receptor availability in fibromyalgia.
      The latter finding, as well as the results of previous studies showing increases in endogenous opioids in the cerebrospinal fluid of patients with FM, have been suggested as evidence of why opioid analgesics appear not to be efficacious in FM and why blocking endogenous opioid activity with low-dose naltrexone might be a promising therapy.
      • Younger J.
      • Mackey S.
      Fibromyalgia symptoms are reduced by low-dose naltrexone: a pilot study.
      In addition to central neurotransmitter systems that are dysregulated in FM and play a role in pathogenesis, there are many other potential pathogenic mechanisms that are being actively explored. Both the hypothalamic-pituitary-adrenal and autonomic nervous systems have been shown to be abnormal in FM.
      • Crofford L.J.
      The hypothalamic-pituitary-adrenal axis in the pathogenesis of rheumatic diseases.
      • Petzke F.
      • Clauw D.J.
      Sympathetic nervous system function in fibromyalgia.
      • Clauw D.J.
      • Chrousos G.P.
      Chronic pain and fatigue syndromes: overlapping clinical and neuroendocrine features and potential pathogenic mechanisms.
      However, these findings are inconsistent from study to study and may in part be driven by comorbidities common to FM such as inactivity, childhood trauma, and psychiatric disorders such as posttraumatic stress disorder and depression. Other theories regarding the pathogenesis of FM that are actively being pursued are the possible role of inflammation and/or glial cell activation,
      • Younger J.
      • Mackey S.
      Fibromyalgia symptoms are reduced by low-dose naltrexone: a pilot study.
      • Maletic V.
      • Raison C.L.
      Neurobiology of depression, fibromyalgia and neuropathic pain.
      small fiber neuropathy,
      • Kim S.H.
      • Kim D.H.
      • Oh D.H.
      • Clauw D.J.
      Characteristic electron microscopic findings in the skin of patients with fibromyalgia—preliminary study.
      • Üçeyler N.
      • Zeller D.
      • Kahn A.K.
      • et al.
      Small fibre pathology in patients with fibromyalgia syndrome.
      and viral reactivation in subsets of individuals.

      Psychological, behavioral, and social issues can both contribute to the underlying pathogenesis of FM and complicate its treatment

      Individuals with FM are more likely to have virtually any psychiatric disorder, including depression, anxiety, obsessive-compulsive disorder, and posttraumatic stress disorder, likely because there are common triggers to both sets of conditions (eg, early life stress or trauma) as well as shared pathophysiology (ie, most of the neurotransmitters that affect pain transmission also affect mood, memory, fatigue, and sleep). Other potentially modifiable risk factors for developing FM include poor sleep, obesity, physical inactivity, and poor job or life satisfaction. Similarly, cognitive factors such as catastrophizing (the feeling that pain is bad and associated with a poor prognosis for recovery) or fear of movement have been shown to be poor prognostic factors in FM and other chronic pain states. Most of these issues are addressed as part of the cognitive behavioral therapy programs for FM and other chronic pain states that have been shown to be effective but are rarely used in clinical practice. Many individuals are seen in routine clinical practice with FM or FM-like syndromes who may respond well to these simple interventions (ie, reduce stress, get enough sleep, and become active and then begin exercising) and not need drug therapy.

      Diagnosis of FM

      The original 1990 American College of Rheumatology criteria for FM were never intended to be used as strict diagnostic criteria for use in clinical practice. Many individuals who clearly have FM will not have pain throughout their entire body or may not have 11 tender points. Moreover, pain and tenderness occur across a continuum in the population, and it is impossible to know where to draw the line between an individual with symptoms and someone with an “illness.”
      • Wolfe F.
      The relation between tender points and fibromyalgia symptom variables: evidence that fibromyalgia is not a discrete disorder in the clinic.
      For this and many other reasons, the alternative 2010 fibromyalgia criteria may represent a preferred manner of diagnosing, or thinking about, FM.
      • Goldenberg D.L.
      • Clauw D.
      • Fitzcharles M.
      • et al.
      How to use the new ACR Fibromyalgia diagnostic criteria.
      • Wolfe F.
      • Clauw D.J.
      • Fitzcharles M.A.
      • et al.
      Fibromyalgia criteria and severity scales for clinical and epidemiological studies: a modification of the ACR Preliminary Diagnostic Criteria for Fibromyalgia.
      • Wolfe F.
      • Clauw D.J.
      • Fitzcharles M.A.
      • et al.
      The American College of Rheumatology preliminary diagnostic criteria for fibromyalgia and measurement of symptom severity.
      The survey criteria for FM are entirely self-reported by patients and can be administered on a single piece of paper. There is a body map with 19 areas (Figure 2) and a symptom survey that asks about the presence and severity of fatigue, sleep disturbances, memory difficulties, and mood problems. When used as a dichotomous measure with various cut points, this measure will roughly identify the same group of individuals as did the old criteria (except more men).
      • Wolfe F.
      • Clauw D.J.
      • Fitzcharles M.A.
      • et al.
      Fibromyalgia criteria and severity scales for clinical and epidemiological studies: a modification of the ACR Preliminary Diagnostic Criteria for Fibromyalgia.
      • Wolfe F.
      • Clauw D.J.
      • Fitzcharles M.A.
      • et al.
      The American College of Rheumatology preliminary diagnostic criteria for fibromyalgia and measurement of symptom severity.
      However, when FM is considered more as a constellation of symptoms that helps determine where on the continuum of pain sensitivity an individual is, this survey can be used as a continuous measure (ie, degree of “fibromyalgia-ness” or the degree to which pain is centralized).
      • Wolfe F.
      Fibromyalgianess.
      Figure thumbnail gr2
      Figure 2The 2011 survey criteria for fibromyalgia.
      • Wolfe F.
      • Clauw D.J.
      • Fitzcharles M.A.
      • et al.
      Fibromyalgia criteria and severity scales for clinical and epidemiological studies: a modification of the ACR Preliminary Diagnostic Criteria for Fibromyalgia.
      These criteria were intended to be used in epidemiological studies, but can also be used in clinical settings to give clinicians a sense of where individuals fall on the fibromyalgia continuum. The instrument is scored by giving 1 point for each location checked on the body map (0-19), 0 to 3 points depending on the presence of fatigue, memory problems, and sleep disturbances (0-9), and 1 point each for irritable bowel, depression, and headache. Although specific cut points have been published regarding the total score that is generally indicative of fibromyalgia (12-13), it is more useful to consider this problem as a continuum rather than discrete illness and understand that in patients with chronic pain higher scores likely indicate that their pain will be less likely to respond to drugs and procedures that generally work well for nociceptive pain (surgery and opioids) and instead behave much more like fibromyalgia pain (ie, respond to centrally acting analgesics and nonpharmacological therapies). ACR = American College of Rheumatology.
      In clinical practice, one should suspect centralized pain or FM in individuals with multifocal pain that cannot be fully explained on the basis of damage or inflammation in those regions of the body. In most cases, musculoskeletal pain is the most prominent feature, but because pain pathways throughout the body are amplified, pain can occur anywhere. Thus, chronic headaches, visceral pain, and symptoms of hyperresponsiveness to other sensory stimuli are common in individuals with FM.
      Although the physical examination is generally unremarkable in individuals with FM, it is helpful to assess diffuse tenderness, and there are many ways that this can be done clinically other than performing a tender point count examination. For example, individuals with FM are more sensitive to the inflation of a blood pressure cuff.
      • Chandran A.B.
      • Coon C.D.
      • Martin S.A.
      • McLeod L.D.
      • Coles T.M.
      • Arnold L.M.
      Sphygmomanometry-evoked allodynia in chronic pain patients with and without fibromyalgia.
      Another way to assess the overall pain threshold is to perform a rapid examination of the hands and arms by applying firm pressure over several interphalangeal joints and adjacent phalanges and then caudally to include firm palpation of the muscles of the forearm. If the individual is tender in many of these areas or just in the muscles of the forearm, the individual is likely diffusely tender (ie, have a low central pain threshold). However, if the individual is tender only in the interphalangeal joints and not the other regions, and especially if there is any swelling in these joints, one should be more concerned about a systemic autoimmune disorder leading to tenderness confined to inflamed joints.
      Laboratory testing is generally not useful, except for the purpose of differential diagnosis. The intensity of the diagnostic work-up can be largely guided by the duration of time the patient has had symptoms. Individuals with long-standing symptoms and a lifetime history of regional pain and other somatic symptoms need little testing, whereas those with acute or subacute onset of those symptoms require a much more aggressive work-up. Simple testing should be limited to complete blood cell count and routine serum chemistries, along with thyroid-stimulating hormone and erythrocyte sedimentation rate and/or C-reactive protein. Serological tests such as antinuclear antibody and rheumatoid factor assays should generally be avoided unless there are features not seen in FM.
      Once a clinician rules out other potential disorders that might be causing the pain and treats potential peripheral causes of the pain, an important and at times controversial consideration to make is whether it is of benefit to use the FM “label.” Despite editorials bemoaning that this label is typically harmful and will increase health care utilization,
      • Hadler N.M.
      “Fibromyalgia” and the medicalization of misery.
      this is not borne out of the existing evidence. The diagnosis of FM is often a tremendous source of relief for patients because they have often visited many providers before this diagnosis is made and there is an explanation for their symptoms. Several studies have shown that the diagnosis can lead to decreased health care utilization because of a reduction in referrals and diagnostic testing “looking for the cause of the pain.”
      • Annemans L.
      • Wessely S.
      • Spaepen E.
      • et al.
      Health economic consequences related to the diagnosis of fibromyalgia syndrome.

      General treatment approach

      The best treatment of FM involves an integrated pharmacological and nonpharmacological approach in which patients play an active role in their treatment. Fibromyalgia should generally be diagnosed and treated in a primary care setting, with referral only for individuals in whom the diagnosis is in question (eg, to rheumatology or neurology, depending on symptoms) or for patients refractory to therapy (eg, to multidisciplinary pain clinics) or with significant comorbid psychiatric issues (eg, to psychiatrist or psychologists). Creating a team of providers (either in the same setting or “virtually”) that includes individuals who can help provide education (eg, mid-level providers or nurse educators) as well as exercise (eg, physical or occupational therapists) and cognitive behavioral treatments can be extremely beneficial to both patients and providers.
      The evidence for various treatments in FM has recently been comprehensively reviewed by the group publishing the Canadian Fibromyalgia Treatment Guidelines,
      • Fitzcharles M.A.
      • Ste-Marie P.A.
      • Goldenberg D.L.
      • et al.
      National Fibromyalgia Guideline Advisory Panel
      2012 Canadian Guidelines for the diagnosis and management of fibromyalgia syndrome: executive summary.
      and this group’s assessment of level of evidence for each therapy is used in this review. These treatments are summarized in Tables 2 (nonpharmacological therapies) and 3 (pharmacological therapies).
      Table 2Nonpharmacological Therapies Useful in the Treatment of Fibromyalgia
      TreatmentCostSpecificsEvidence levelAdverse effectsClinical pearls
      General recommendations
       Patient education
      • Häuser W.
      • Bernardy K.
      • Arnold B.
      • Offenbächer M.
      • Schiltenwolf M.
      Efficacy of multicomponent treatment in fibromyalgia syndrome: a meta-analysis of randomized controlled clinical trials.
      LowIncorporate principles of self-management including a multimodal approach1, AAfter the initial diagnosis, spend several visits (or use separate educational sessions) to explain the condition and set treatment expectations
      Nonpharmacological therapies
       Graded exercise
      • Häuser W.
      • Klose P.
      • Langhorst J.
      • et al.
      Efficacy of different types of aerobic exercise in fibromyalgia syndrome: a systematic review and meta-analysis of randomised controlled trials.
      LowAerobic exercise has been shown to be the best, but strengthening and stretching have also been shown to be of value1, AWorsening of symptoms when the program begins too rapidlyCounsel patients to “start low, go slow”

      For many patients, focusing first on increasing daily “activity” is more helpful before actually starting exercise
       Cognitive behavioral therapy (CBT)
      • Bernardy K.
      • Füber N.
      • Köllner V.
      • Häuser W.
      Efficacy of cognitive-behavioral therapies in fibromyalgia syndrome—a systematic review and metaanalysis of randomized controlled trials.
      LowPain-based CBT programs have been shown to be effective in 1-on-1 settings, in small groups, and via the Internet1, ANo significant adverse effects of CBT per se, but patient acceptance is often poor when they view this as a “psychological” interventionInternet-based programs are gaining acceptance and are more convenient for working patients
       Complementary and alternative medicine (CAM) therapies
      • Porter N.S.
      • Jason L.A.
      • Boulton A.
      • Bothne N.
      • Coleman B.
      Alternative medical interventions used in the treatment and management of myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia.
      VariableMost CAM therapies have not been rigorously studied1, AGenerally safeThere is emerging evidence that CAM treatments such as tai chi, yoga, balneotherapy, and acupuncture might be effective

      Allowing patients to choose which CAM therapies to incorporate into an active treatment program can increase self-efficacy
       Central nervous system (CNS) neurostimulatory therapies
      • Hargrove J.B.
      • Bennett R.M.
      • Simons D.G.
      • Smith S.J.
      • Nagpal S.
      • Deering D.E.
      A randomized placebo-controlled study of noninvasive cortical electrostimulation in the treatment of fibromyalgia patients.
      Several types of CNS neurostimulatory therapies have been shown to be effective in fibromyalgia and other chronic pain statesInconsistent findingsHeadacheThese treatments continue to be refined as we learn about optimal stimulation targets, “dosing,” etc
      Table 3Pharmacological Therapies Useful in the Treatment of Fibromyalgia
      TreatmentCostSpecificsEvidence levelAdverse effectsClinical pearls
      Pharmacological therapiesPharmacological therapy is best chosen on the basis of the predominant symptoms and initiated in low dose with slow dose escalationLevel 5, consensusSome practitioners find that getting patients on a drug regimen that helps improve symptoms before initiating nonpharmacological therapies can help improve adherence
       Tricyclic compounds
      • Arnold L.M.
      Duloxetine and other antidepressants in the treatment of patients with fibromyalgia.
      • Arnold L.M.
      • Keck Jr., P.E.
      • Welge J.A.
      Antidepressant treatment of fibromyalgia: a meta-analysis and review.
      Amitriptyline, 10-70 mg every night at bedtime

      Cyclobenzaprine, 5-20 mg every night at bedtime
      1, ADry mouth, weight gain, constipation, and “groggy” or drugged feelingWhen effective, they can improve a wide range of symptoms including pain, sleep, and bowel and bladder syndromes

      Taking these drugs several hours before bedtime improves the adverse effect profile
      Serotonin norepinephrine reuptake inhibitors
      • Arnold L.M.
      Duloxetine and other antidepressants in the treatment of patients with fibromyalgia.
      Duloxetine is generic, but milnacipran is notDuloxetine, 30-120 mg/d

      Milnacipran, 100-200 mg/d
      1, ANausea, palpitations, headache, fatigue, tachycardia, and hypertensionWarning patients about transient nausea, taking with food, and slowly increasing dose can increase tolerability

      Milnacipran might be slightly more noradrenergic than duloxetine and thus potentially more helpful for fatigue and memory problems, but also more likely to cause hypertension
      Gabapentinoids
      • Häuser W.
      • Bernardy K.
      • Uçeyler N.
      • Sommer C.
      Treatment of fibromyalgia syndrome with gabapentin and pregabalin—a meta-analysis of randomized controlled trials.
      Gabapentin is generic, but pregabalin is notGabapentin, 800-2400 mg/d in divided doses

      Pregabalin, up to 600 mg/d in divided doses
      1, ASedation, weight gain, and dizzinessGiving most or all of the dose at bedtime can increase tolerability
      γ-Hydroxybutyrate
      • Russell I.J.
      • Holman A.J.
      • Swick T.J.
      • Alvarez-Horine S.
      • Wang Y.G.
      • Guinta D.
      Sodium Oxybate 06-008 FM Study Group
      Sodium oxybate reduces pain, fatigue, and sleep disturbance and improves functionality in fibromyalgia: results from a 14-week, randomized, double-blind, placebo-controlled study.
      Available for treating narcolepsy and cataplexy4.5-6.0 g every night in divided doses1, ASedation, respiratory depression, and deathShown to be efficacious but not approved by the US Food and Drug Administration because of safety concerns
      Low-dose naltrexone
      • Younger J.
      • Noor N.
      • McCue R.
      • Mackey S.
      Low-dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double-blind, placebo-controlled, counterbalanced, crossover trial assessing daily pain levels.
      Low4.5 mg/d2 small single-center randomized controlled trials
      Cannabinoids
      • Lynch M.E.
      • Campbell F.
      Cannabinoids for treatment of chronic non-cancer pain: a systematic review of randomized trials.
      Not applicableNabilone, 0.5 mg poqhs to 1.0 mg bid1, ASedation, dizziness, and dry mouthNo synthetic cannabinoid is approved in the United States for the treatment of pain
      Selective serotonin reuptake inhibitors (SSRIs)
      • Arnold L.M.
      Duloxetine and other antidepressants in the treatment of patients with fibromyalgia.
      SSRIs that should be used in fibromyalgia (see Pearls) are all genericFluoxetine, sertraline, and paroxetine1, ANausea, sexual dysfunction, weight gain, and sleep disturbanceOlder, less selective SSRIs may have some efficacy in improving pain, especially at higher doses that have more prominent noradrenergic effects

      Newer SSRIs (citalopram, escitalopran, and desvenlafaxine) are less effective or ineffective as analgesics
      Nonsteroidal anti-inflammatory drugsNo evidence of efficacy

      Can be helpful to treat comorbid “peripheral pain generators”
      5, DGastrointestinal, renal, and cardiac adverse effectsUse the lowest dose for the shortest period of time to reduce adverse effects
      OpioidsTramadol with or without acetaminophen, 50-100 mg every 6 h

      No evidence of efficacy for stronger opioids
      5, DSedation, addiction, tolerance, and opioid-induced hyperalgesiaThere is increasing evidence that opioids are less effective in treating chronic pain than previously thought and that their risk-benefit profile is worse than that of other classes of analgesics
      bid = twice daily; poqhs = at bedtime.

      Nonpharmacological therapies

      The 3 best-studied nonpharmacological therapies are education, cognitive behavioral therapy, and exercise, and all these have strong evidence (level I, A) for use in FM. In fact, the effect size of these therapies often exceeds that of drug therapies, especially for improving function, which should be the therapeutic focus in treating chronic pain.
      • Williams D.A.
      • Cary M.A.
      • Glazer L.J.
      • Rodriguez A.M.
      • Clauw D.J.
      Randomized controlled trial of CBT to improve functional status in fibromyalgia.
      • Goldenberg D.L.
      • Burckhardt C.
      • Crofford L.
      Management of fibromyalgia syndrome.
      Another advantage of these treatments is that they can lead to sustained (eg, >1 year) improvements. Access and adherence are the biggest issues with these therapies. These types of nonpharmacological approaches are increasingly available via websites (eg, www.fibroguide.com
      • Williams D.A.
      • Kuper D.
      • Segar M.
      • Mohan N.
      • Sheth M.
      • Clauw D.J.
      Internet-enhanced management of fibromyalgia: a randomized controlled trial.
      ) and smartphone apps to increase patient accessibility.
      Complementary and alternative therapies can be a useful adjunct in the treatment of FM. As in other disorders, there are relatively few controlled trials to advocate their general use. Trigger point injections, chiropractic manipulation, tai chi, yoga, acupuncture, and myofascial release therapy all have some evidence of efficacy and are among the more commonly used modalities.
      • Mist S.D.
      • Firestone K.A.
      • Jones K.D.
      Complementary and alternative exercise for fibromyalgia: a meta-analysis.
      There is also some evidence that the use of such alternative therapies gives patients a greater sense of control over their illness and that giving patients a choice of therapies might make it more likely that improvement via the body’s internal analgesic mechanisms (ie, the placebo response) is engendered. Thus, even in the absence of strong evidence of efficacy for all such therapies, as long as the treatment does no harm, the threshold for recommending such therapies should be low because overall treatment options for chronic pain are limited.
      Although FM is still generally thought not to be due to peripheral damage or inflammation, there is emerging evidence that identifying and treating peripheral pain generators may be helpful, perhaps because peripheral nociceptive input is known to drive central sensitization. Thus, a recent study reported that individuals with FM with comorbid osteoarthritis or myofascial pain had improvement in their overall FM pain and tenderness when these were treated with local therapies.
      • Lee Y.C.
      • Nassikas N.J.
      • Clauw D.J.
      The role of the central nervous system in the generation and maintenance of chronic pain in rheumatoid arthritis, osteoarthritis and fibromyalgia.
      • Affaitati G.
      • Costantini R.
      • Fabrizio A.
      • Lapenna D.
      • Tafuri E.
      • Giamberardino M.A.
      Effects of treatment of peripheral pain generators in fibromyalgia patients.
      There is also emerging evidence that some individuals with FM exhibit a small fiber neuropathy on biopsy,
      • Caro X.J.
      • Winter E.F.
      • Dumas A.J.
      A subset of fibromyalgia patients have findings suggestive of chronic inflammatory demyelinating polyneuropathy and appear to respond to IVIg.
      although the treatment implications of this finding are still not clear.
      Various neurostimulatory therapies can be effective in treating musculoskeletal pain. For some time, transcutaneous electrical nerve stimulation has been used to treat peripheral musculoskeletal pain, but a new set of therapies is being developed to stimulate the CNS, and these are beginning to show promise in treating centralized pain states such as FM.
      • Williams J.A.
      • Imamura M.
      • Fregni F.
      Updates on the use of non-invasive brain stimulation in physical and rehabilitation medicine.
      • Foerster B.R.
      • Nascimento T.D.
      • DeBoer M.
      • et al.
      Excitatory and inhibitory brain metabolites as targets of motor cortex transcranial direct current stimulation therapy and predictors of its efficacy in fibromyalgia.

      Pharmacological therapies

      Several drugs or classes of drugs have strong evidence (level I, A) for efficacy in FM,
      • Hauser W.
      • Petzke F.
      • Sommer C.
      Comparative efficacy and harms of duloxetine, milnacipran, and pregabalin in fibromyalgia syndrome.
      including tricyclic compounds
      • Arnold L.M.
      Duloxetine and other antidepressants in the treatment of patients with fibromyalgia.
      (amitriptyline and cyclobenzaprine), gabapentinoids
      • Tzellos T.G.
      • Toulis K.A.
      • Goulis D.G.
      • et al.
      Gabapentin and pregabalin in the treatment of fibromyalgia: a systematic review and a meta-analysis.
      (pregabalin and gabapentin), serotonin-norepinephrine reuptake inhibitors (duloxetine
      • Arnold L.M.
      • Clauw D.J.
      • Wohlreich M.M.
      • et al.
      Efficacy of duloxetine in patients with fibromyalgia: pooled analysis of 4 placebo-controlled clinical trials.
      and milnacipran
      • Geisser M.E.
      • Palmer R.H.
      • Gendreau R.M.
      • Wang Y.
      • Clauw D.J.
      A pooled analysis of two randomized, double-blind, placebo-controlled trials of milnacipran monotherapy in the treatment of fibromyalgia.
      ), and γ-hydroxybutyrate.
      • Russell I.J.
      • Holman A.J.
      • Swick T.J.
      • Alvarez-Horine S.
      • Wang Y.G.
      • Guinta D.
      Sodium Oxybate 06-008 FM Study Group
      Sodium oxybate reduces pain, fatigue, and sleep disturbance and improves functionality in fibromyalgia: results from a 14-week, randomized, double-blind, placebo-controlled study.
      Drugs with more limited evidence of efficacy include older selective serotonin reuptake inhibitors with greater noradrenergic activity when used at higher doses (eg, fluoxetine,
      • Arnold L.M.
      • Hess E.V.
      • Hudson J.I.
      • Welge J.A.
      • Berno S.E.
      • Keck Jr., P.E.
      A randomized, placebo-controlled, double-blind, flexible-dose study of fluoxetine in the treatment of women with fibromyalgia.
      paroxetine, and sertraline), low-dose naltrexone,
      • Younger J.
      • Mackey S.
      Fibromyalgia symptoms are reduced by low-dose naltrexone: a pilot study.
      esreboxetine
      • Arnold L.M.
      • Hirsch I.
      • Sanders P.
      • Ellis A.
      • Hughes B.
      Safety and efficacy of esreboxetine in patients with fibromyalgia: a fourteen-week, randomized, double-blind, placebo-controlled, multicenter clinical trial.
      (a selective norepinephrine reuptake inhibitor not available in the United States), cannabinoids, and memantine.
      • Skrabek R.Q.
      • Galimova L.
      • Ethans K.
      • Perry D.
      Nabilone for the treatment of pain in fibromyalgia.
      • Olivan-Blázquez B.
      • Herrera-Mercadal P.
      • Puebla-Guedea M.
      • et al.
      Efficacy of memantine in the treatment of fibromyalgia: a double-blind, randomised, controlled trial with 6-month follow-up.
      Just as with treating most other chronic illnesses of a complex polygenic nature, it is often necessary to use several of these drugs with different action mechanisms in combination.
      Of note are the classes of drugs that have not been found to be efficacious in FM, such as NSAIDs, opioids, and corticosteroids, because these are the mainstay of therapy in other peripheral pain states. Although there is a sense in clinical practice that the “FM drugs” do not work as well for these patients as other classes of analgesics work for other types of pain, this is simply not true. All oral analgesics are at best modestly effective in treating any type of chronic pain (ie, work well in a third of patients), including NSAIDs and opioids.
      • Clauw D.J.
      Pain management: fibromyalgia drugs are ‘as good as it gets’ in chronic pain.
      In fact, there is emerging concern that opioids might even be in part driving the hyperalgesia seen in FM and other centralized pain states or frequently leading to opioid-induced hyperalgesia.

      Conclusion

      Many, if not most, in the pain field now believe that FM is the prototypical centralized pain state. This can occur either in the absence of damage or inflammation of tissues or in a subset of individuals with any chronic pain condition. In the former instance, individuals will typically begin having pain in various regions of the body early in life, and then when the pain finally becomes widespread later in life, it is termed fibromyalgia. Conversely, in individuals with diseases known to be associated with damage or inflammation (eg, autoimmune disorders) or damage (eg, osteoarthritis), the same phenomenon can occur and seems to be driven by ongoing peripheral nociceptive input. If this is true, we might be able to “prevent” FM by identifying individuals with this centralized pain prone phenotype and treating them aggressively when they have acute or subacute pain due to peripheral nociceptive input so that it does not centralize and becomes chronic. Once pain centralization occurs, regardless of the underlying “disease” that might have originally led to pain, it is likely to respond to the same types of treatments as FM. Most importantly, once centralization/FM occurs, these individuals will be less responsive to our mainstays of treating ongoing peripheral nociceptive pain (eg, opioids, injections, and surgical procedures) and more responsive to centrally acting analgesic and nondrug therapies.

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