Fibromyalgia Syndrome: A Discussion of the Syndrome and Pharmacotherapy

Review of Fibromyalgia (FM) Syndrome Treatments

BACKGROUND

Fibromyalgia (FM) is a disease characterized by widespread musculoskeletal chronic pain that impairs the patient's quality of life and is considered a somatization disorder. The symptoms of the disease also affect the patient mentally, mainly since invisible pain is the only thing that indicates its existence. A typical symptom that characterizes FM patients is the lack of acceptance of the disease since its pathophysiology is not elucidated, hence the deficiencies in its management, or rather, cognitively, the belief that there is no disease to manage. The current paper aims to shed light on the new treatment methods at a holistic level, that is, cognitive, physical, and pharmacological therapies.

METHOD

A literature review was carried out that discusses treatment methods that help alleviate the pain, accept it, and manage the symptoms of the disease.

RESULTS

FM symptoms can be treated by taking a broad view of treatment that will include a response to the mind through pain management, response to the body through physical activity, and response to the pain through pharmacological treatment.

CONCLUSIONS

Today, there is an evolutionary view that accepts FM and chronic pain diseases as syndromes in which the pain is the disease; therefore, the response to this disease can be applied through three channels: physical, bodily, and mental.

The Efficacy of Capsaicin on Sleep Quality and Fatigue in Fibromyalgia

Capsaicin is a topical pain reliever that has been evaluated by randomized controlled trials (RCTs) as a potential adjunctive therapy for treating unmitigated fibromyalgia. Therefore, a review of English articles using PubMed and Embase was conducted from January 1, 1990 to February 9, 2022 in order to evaluate the utility of capsaicin for improvement of sleep quality and fatigue associated with fibromyalgia. The search terms included: "fibromyalgia" and "capsaicin". Articles included were RCTs evaluating capsaicin in adult patients with fibromyalgia. Two studies met criteria and included 175 patients that received either capsaicin or placebo for an average total treatment length of 5 weeks. The treatment outcomes assessed were changes in quality of sleep and fatigue by several standardized modalities. These include visual analog scale (VAS) of sleep quality and fatigue, fatigue severity scale, Pittsburgh Sleep Quality Index (PSQI), and global subjective improvement. Both studies demonstrated no changes in sleep quality, but one study did find a significant difference in global subjective improvement. This same study also found a significant improvement in fatigue. Consequently, this existing evidence is insufficient to warrant recommending capsaicin as adjunctive therapy for improvement in sleep quality and fatigue. Future studies regarding capsaicin therapy for fibromyalgia are needed.

IL-5 mediates monocyte phenotype and pain outcomes in fibromyalgia

ABSTRACT

Fibromyalgia (FM) is characterized by widespread chronic pain, fatigue, and somatic symptoms. The influence of phenotypic changes in monocytes on symptoms associated with FM is not fully understood. The primary aim of this study was to take a comprehensive whole-body to molecular approach in characterizing relationships between monocyte phenotype and FM symptoms in relevant clinical populations. Lipopolysaccharide-evoked and spontaneous secretion of IL-5 and other select cytokines from circulating monocytes was higher in women with FM compared to women without pain. In addition, greater secretion of IL-5 was significantly associated with pain and other clinically relevant psychological and somatic symptoms of FM. Furthermore, higher levels of pain and pain-related symptoms were associated with a lower percentage of intermediate monocytes (CD14++/CD16+) and a greater percentage of nonclassical monocytes (CD14+/CD16++) in women with FM. Based on findings from individuals with FM, we examined the role of IL-5, an atypical cytokine secreted from monocytes, in an animal model of widespread muscle pain. Results from the animal model show that IL-5 produces analgesia and polarizes monocytes toward an anti-inflammatory phenotype (CD206+). Taken together, our data suggest that monocyte phenotype and their cytokine profiles are associated with pain-related symptoms in individuals with FM. Furthermore, our data show that IL-5 has a potential role in analgesia in an animal model of FM. Thus, targeting anti-inflammatory cytokines such as IL-5 secreted by circulating leukocytes could serve as a promising intervention to control pain and other somatic symptoms associated with FM.

Abnormal neuroinflammation in fibromyalgia and CRPS using [11C]-(R)-PK11195 PET

Purpose

Fibromyalgia (FM) and complex regional pain syndrome (CRPS) share many pathological mechanisms related to chronic pain and neuroinflammation, which may contribute to the multifactorial pathological mechanisms in both FM and CRPS. The aim of this study was to assess neuroinflammation in FM patients compared with that in patients with CRPS and healthy controls.

Methods

Neuroinflammation was measured as the distribution volume ratio (DVR) of [¹¹C]-(R)-PK11195 positron emission tomography (PET) in 12 FM patients, 11 patients with CRPS and 15 healthy controls.

Results

Neuroinflammation in FM patients was significantly higher in the left pre (primary motor cortex) and post (primary somatosensory cortex) central gyri (p < 0.001), right postcentral gyrus (p < 0.005), left superior parietal and superior frontal gyri (p < 0.005), left precuneus (p < 0.01), and left medial frontal gyrus (p = 0.036) compared with healthy controls. Furthermore, the DVR of [¹¹C]-(R)-PK11195 in FM patients demonstrated decreased neuroinflammation in the medulla (p < 0.005), left superior temporal gyrus (p < 0.005), and left amygdala (p = 0.020) compared with healthy controls.

Conclusions

To the authors’ knowledge, this report is the first to describe abnormal neuroinflammation levels in the brains of FM patients compared with that in patients with CRPS using [¹¹C]-(R)-PK11195 PET. The results suggested that abnormal neuroinflammation can be an important pathological factor in FM. In addition, the identification of common and different critical regions related to abnormal neuroinflammation in FM, compared with patients with CRPS and healthy controls, may contribute to improved diagnosis and the development of effective medical treatment for patients with FM.

Tramadol for management of fibromyalgia pain and symptoms: Systematic review

BACKGROUND

Fibromyalgia is a heterogeneous condition that appears to be associated with physiological and biochemical disturbances of pain modulation, and that consequently affects numerous other facets of life. Tramadol is currently being explored as an option to manage fibromyalgia pain and other symptoms because of its inhibitory activity of reuptake of neurotransmitters, but its safety and efficacy have not yet been established in these patients.

OBJECTIVE

To evaluate the effectiveness and safety of tramadol on the management of symptoms of the syndrome.

METHODS

We searched CENTRAL, MEDLINE, EMBASE, LILACS, Opengrey, ClinicalTrials.gov and WHO-ICTRP for randomised controlled trials analysing the association between tramadol used for fibromyalgia either single-agent or in combination with other drugs. Two reviewers independently extracted data and assessed risk of bias using the Cochrane risk-of-bias tool for all included studies. Quality of the evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

Four RCTs comprising 459 patients were included. Tramadol-either as a single-agent or in combination with an antidepressant or analgesic-had a positive effect on pain. Tramadol combined with analgesic showed improved quality of life over placebo as measured by the Fibromyalgia Impact Questionnaire at 91 days. However, this difference did not hold for tramadol as a single agent against placebo. The evidence in these articles was rated "low" using the GRADE approach. No serious adverse events were reported. No improvement in depression and quality of sleep were observed.

CONCLUSIONS

This systematic review found a dearth of clinical trials on tramadol in patients with fibromyalgia. Although the combination of monoamine and opioid mechanism of tramadol has shown positive effects for fibromyalgia, the available evidence is not sufficient to support or refute the use of tramadol in clinical practice for pain or symptom management. Protocol registration number in the PROSPERO database: CRD42017062139.

Current and Emerging Pharmacotherapy for Fibromyalgia

Introduction. Fibromyalgia syndrome (FMS) is a pain disorder with an estimated prevalence of 1–5%. It is associated with a variety of somatic and psychological disorders. Its exact pathogenesis is still unclear but is involved with neural oversensitization and decreased conditioned pain modulation (CPM), combined with cognitive dysfunction, memory impairment, and altered information processing. Connectivity between brain areas involved in pain processing, alertness, and cognition is increased in the syndrome, making its pharmacologic therapy complex. Only three drugs, pregabalin, duloxetine, and milnacipran are currently FDA-approved for FM treatment, but many other agents have been tested over the years, with varying efficacy. Areas Covered. The purpose of this review is to summarize current clinical experience with different pharmacologic treatments used for fibromyalgia and introduce future perspectives in developing therapies. Expert Opinion. Future insights into the fields of cannabinoid and opioid research, as well as an integrative approach towards the incorporation of genetics and functional imaging combined with additional fields of research relevant towards the study of complex CNS disorders, are likely to lead to new developments of novel tailor-made treatments for FMS patients.

Commonalities and differences in abnormal peripheral metabolites between patients with fibromyalgia and complex regional pain syndrome

Background: Fibromyalgia (FM) and complex regional pain syndrome (CRPS) share many pathological mechanisms related to chronic pain that could contribute to multifactorial pathological mechanisms.Methods: We investigated peripheral metabolites in FM and CRPS patients compared to healthy controls based on cross-sectional study.Results: Mean corpuscular hemoglobin (p < 0.001), mean corpuscular volume (p = 0.014), and total bilirubin levels (p = 0.017) were lower in FM patients than in healthy controls. On the other hand, CRPS patients showed lower levels of total bilirubin than healthy controls (p = 0.037). Creatinine level was lower in FM patients (p = 0.057) compared to healthy controls, particularly when comparing the low-hemoglobin subgroup among FM patients (p = 0.035) with the low-hemoglobin subgroup among healthy controls. Red blood cell count (r = -0.620, p = 0.031), hematocrit (r = -0.593, p = 0.042), and creatinine level (r = -0.598, p = 0.040) showed negative correlations with McGill Pain Questionnaire-Affective (MPQ-A) scores in FM patients. A negative correlation was observed between MCV and McGill Pain Questionnaire-Sensory scores (r = -0.680, p = 0.015) in CRPS patients.Conclusion: We found specific peripheral metabolites that may exhibit different tendency between FM and CRPS patients as well as some common metabolites, which may be associated with peripheral pathology in the patients. Considering this study had a few limitations such as a small sample sizes and using a liberal threshold of significance in the correlation analysis, future studies with larger sample sizes may be needed to generalize these findings.

Primary Headache Disorders- Part 2: Tension-type headache and medication overuse headache

In Part 2 of Primary Headache disorders, we discuss the fourth Primary Headache Disorder, Tension-Type Headache (TTHA). We are again using the ICHD-III (Beta) definitions of such headaches, taking into consideration episodic and chronic TTHA, as well as the presence or absence of pericranial muscle tenderness. We discuss the pathophysiology and pharmacotherapeutic treatment of TTHA, and the aspects of the Myofascial Pain Syndrome that enhance and help the development of TTHA. We then discuss Medication Overuse Headache (MOH), itself a Secondary headache disorder, but one that is extremely important as it assists with the chronification of both migraine and TTHA. Finally we discuss how to manage and treat those patients with MOH. Chronic migraine, which is TTHA, Migraine as well as, in many patients, MOH, is discussed along with the treatment of this multifaceted disorder.

Clinical Manifestations Associated with Overweight/Obesity in Puerto Ricans with Fibromyalgia Syndrome

Objective. To determine the clinical manifestations associated with overweight/obesity in Hispanics from Puerto Rico with fibromyalgia syndrome (FMS). Methods. A cross-sectional study was performed in 144 patients with FMS (per American College of Rheumatology (ACR) classification criteria). Sociodemographic features, FMS-related symptoms, tender points (per ACR criteria), comorbidities, and FMS treatment were examined. BMI was calculated and patients were grouped into two categories: BMI ≤ 24.9 kg/m(2) (nonoverweight/obese) and BMI ≥ 25 kg/m(2) (overweight/obese). Bivariate and multivariate analyses were used to evaluate differences between the study groups. Results. The mean (standard deviation (SD)) age of patients was 50.2 (9.9) years; 95.1% were females and 75.7% were overweight/obese. In the bivariate analysis, overweight/obese patients were more likely to have self-reported memory impairment, anxiety, shortness of breath, and urinary frequency than nonoverweight/obese patients. In addition, the tender point count was higher in the overweight/obese group. In the logistic regression analyses, self-reported memory impairment and urinary frequency differences remained significant after adjusting for confounding variables. Conclusion. In this population of Puerto Ricans with FMS, overweight/obese patients experienced more FMS-related manifestations than nonoverweight/obese individuals. However, prospective studies are needed to confirm these associations and to elucidate if weight reduction interventions could favorably impact the severity of FMS.

Irritable bowel syndrome: an integrated explanatory model for clinical practice

BACKGROUND

Although irritable bowel syndrome (IBS) is a symptom-based diagnosis, clinicians' management of and communication about the disorder is often hampered by an unclear conceptual understanding of the nature of the problem. We aimed to elucidate an integrated explanatory model (EM) for IBS from the existing literature for pragmatic use in the clinical setting.

METHODS

Systematic and exploratory literature searches were performed in PubMed to identify publications on IBS and EMs.

KEY RESULTS

The searches did not identify a single, integrated EM for IBS. However, three main hypotheses were elucidated that could provide components with which to develop an IBS EM: (i) altered peripheral regulation of gut function (including sensory and secretory mechanisms); (ii) altered brain-gut signaling (including visceral hypersensitivity); and (iii) psychological distress. Genetic polymorphisms and epigenetic changes may, to some degree, underlie the etiology and pathophysiology of IBS and could increase the susceptibility to developing the disorder. The three model components also fit into one integrated explanation for abdominal symptoms and changes in stool habit. Additionally, IBS may share a common pathophysiological mechanism with other associated functional syndromes.

CONCLUSIONS & INFERENCES

It was possible to elucidate an integrated, three-component EM as a basis for clinicians to conceptualize the nature of IBS, with the potential to contribute to better diagnosis and management, and dialog with sufferers.

A Review of Select Centralized Pain Syndromes: Relationship With Childhood Sexual Abuse, Opiate Prescribing, and Treatment Implications for the Primary Care Physician

Pain can be broadly divided into 3 classes, including nociceptive or inflammatory pain (protective), neuropathic (pathological, occurring after damage to the nervous system), or centralized (pathological, due to abnormal function but with no damage or inflammation to the nervous system). The latter has been posited to occur when descending analgesic pathways are attenuated and/or glutamatergic transmission is facilitated. Additionally, this "pain prone phenotype" can be associated with early life trauma and a suboptimal response to opiates. This article will review the relationships between centralized pain syndromes (ie, fibromyalgia, chronic low back pain), childhood sexual abuse, and opiate misuse. Finally, treatment implications, potentially effecting primary care physicians, will be discussed.

Exercise and neurologic disease

PURPOSE OF REVIEW

This article provides a practical clinical approach for the role of exercise in the treatment and management of neurologic disorders.

RECENT FINDINGS

A number of clinical studies have reported positive benefits from exercise in various neurologic disease states, suggesting that this mode of intervention should be considered as another option in clinical management.

SUMMARY

Significant evidence-based data exists confirming the positive effects of exercise in otherwise healthy populations. Good evidence also exists that physical activity may benefit people with long-term neurologic conditions. Despite this evidence, exercise is often neglected in patients with normal aging or neurologic disease progression. Neurologists should counsel patients on this therapeutic adjunct and provide specific recommendations when possible.

Fibromyalgia and arachnoiditis presented as an acute spinal disorder

BACKGROUND

Adhesive arachnoiditis is a chronic, insidious condition that causes debilitating intractable pain and a range of other neurological problems. Its pathophysiology is not well understood. This manuscript discusses its presentations, which can mimic an acute spinal disorder, its hypothetical pathophysiology, treatment, and its relationship with fibromyalgia.

CASE DESCRIPTION

The authors present a case of a 47-year-old female who presented with clinical features mimicking an acute spinal disorder but later found to have an adhesive arachnoiditis. She was admitted following a trauma with complaints of back pain and paraplegia. On examination, there was marked tenderness over thoracolumbar spine with lower limbs upper motor neuron weakness. An urgent magnetic resonance imaging (MRI) of the spine revealed multiple lesions at her thoracic and lumbar spinal canals, which did not compress the spinal cord. Therefore, conservative management was initiated. Despite on regular therapies, her back and body pain worsened and little improvement in her limbs power was noted. Laminectomy was pursued and found to have spinal cord arachnoiditis. Subsequently, she was operated by other team members for multiple pelvic masses, which later proved to be benign. After gathering all the clinical information obtained at surgery and after taking detailed history inclusive of cognitive functions, diagnosis of an adhesive arachnoiditis syndrome was made. Currently, she is managed by neuropsychologist and pain specialist.

CONCLUSION

This case report highlights the importance of knowing an adhesive arachnoiditis syndrome - a rarely discussed pathology by the neurosurgeon, which discloses a significant relationship between immune and nervous systems.

Fibromyalgia: disease synopsis, medication cost effectiveness and economic burden

Fibromyalgia (FM) primarily affects women, and it is increasingly recognized by health care providers as more patients seek assistance for their chronic pain conditions. FM patients suffer from reduced quality of life, daily functioning and productivity. A single FM patient can cost society tens of thousands of dollars each year, with the overall expense increasing alongside disease severity. Indirect costs account for the majority of total expenditures and involve losses in productivity, reduced work hours, absenteeism, disability, unemployment, early retirement, informal care and other out-of-pocket costs. Health care utilization increases in concert with the severity of illness. Moreover, FM patients often have several comorbid illnesses (e.g. depression, anxiety and sleep disturbances), resulting in extreme escalation of overall health care expenditures. Medications with the best efficacy in the treatment of FM include the tricyclic antidepressants amitriptyline and nortriptyline, cyclobenzaprine (a skeletal muscle relaxant), tramadol, duloxetine, milnacipran, pregabalin and gabapentin. Corticosteroids, nonsteroidal anti-inflammatory drugs, benzodiazepines and opioid analgesics, with the exception of tramadol, are not considered efficacious. Medication selection should be individualized and influenced by the severity of illness and the presence of comorbidities and functional disabilities.

A critical appraisal of the evidence for botulinum toxin type A in the treatment for cervico-thoracic myofascial pain syndrome

Myofascial pain syndrome (MPS) is a musculoskeletal condition characterized by regional pain and muscle tenderness associated with the presence of myofascial trigger points (MTrPs). The last decade has seen an exponential increase in the use of botulinum toxin (BTX) to treat MPS. To understand the medical evidence substantiating the role of therapeutic BTX injections and to provide useful information for the medical practitioner, we applied the principles of evidence-based medicine to the treatment for cervico-thoracic MPS. A search was conducted through MEDLINE (PubMed, OVID, MDConsult), EMBASE, SCOPUS and the Cochrane database for the period 1966 to 2012 using the following keywords: myofascial pain, muscle pain, botulinum toxin, trigger points, and injections. A total of 7 trials satisfied our inclusion criteria and were evaluated in this review. Although the majority of studies found negative results, our analysis identified Gobel et al.'s as the highest quality study among these prospectively randomized investigations. This was due to appropriate identification of diagnostic criteria, excellent study design and objective endpoints. The 6 other identified studies had significant failings due to deficiencies in 1 or more major criteria. We conclude that higher quality, rigorously standardized studies are needed to more appropriately investigate this promising treatment modality.

Milnacipran for fibromyalgia: a useful addition to the treatment armamentarium

INTRODUCTION

Antidepressants are used to treat a variety of chronic pain conditions including peripheral neuropathy, headache, and more recently, fibromyalgia. The antidepressant milnacipran blocks the reuptake of norepinephrine and serotonin and is used for the management of fibromyalgia.

AREAS COVERED

The article contains data primarily obtained from the MEDLINE database using a PubMed search of the keywords including milnacipran, fibromyalgia and depression. Of the available serotonin norepinephrine reuptake inhibitors, milnacipran has greater potency in inhibiting reuptake of norepinephrine relative to serotonin and is proposed to work by attenuating pain signals. Milnacipran is well tolerated and effective for fibromyalgia pain when given in divided doses of 100 - 200 mg daily. Studies show that milnacipran may be effective for fibromyalgia-associated symptoms including depression and fatigue.

EXPERT OPINION

Milnacipran provides modest fibromyalgia pain relief and is best used as part of a multidisciplinary treatment approach. While milnacipran was not studied in fibromyalgia patients with major depression, it may be a wise choice for fibromyalgia patients with depressive symptoms and patients for whom sedation, dizziness, edema or weight gain with gabapentin and pregabalin is a problem. Milnacipran has been found to be beneficial for treating some troublesome fibromyalgia-associated symptoms, including fatigue and cognitive dysfunction.

A mechanism-based classification of pain in multiple sclerosis

Pharmacological treatment of pain in multiple sclerosis (MS) is challenging due to the many underlying pathophysiological mechanisms. Few controlled trials show adequate pain control in this population. Emerging evidence suggests that pain might be more effectively classified and treated according to symptoms and underlying mechanisms. The new mechanism-based classification we propose here distinguishes nine types of MS-related pain: trigeminal neuralgia and Lhermitte's phenomenon (paroxysmal neuropathic pain due to ectopic impulse generation along primary afferents), ongoing extremity pain (deafferentation pain secondary to lesion in the spino-thalamo-cortical pathways), painful tonic spasms and spasticity pain (mixed pains secondary to lesions in the central motor pathways but mediated by muscle nociceptors), pain associated with optic neuritis (nerve trunk pain originating from nervi nervorum), musculoskeletal pains (nociceptive pain arising from postural abnormalities secondary to motor disorders), migraine (nociceptive pain favored by predisposing factors or secondary to midbrain lesions), and treatment-induced pains. Identification of various types of MS-related pain will allow appropriate targeted pharmacological treatment and improve clinical practice.

A review of duloxetine 60 mg once-daily dosing for the management of diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain due to chronic osteoarthritis pain and low back pain

BACKGROUND

Duloxetine is a selective dual neuronal serotonin (5-Hydroxytryptamine, 5-HT) and norepinephrine reuptake inhibitor (SSNRI). It is indicated in the United States for treatment of major depressive disorder (MDD), generalized anxiety disorder (GAD), and several chronic pain conditions, including management of diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain due to chronic osteoarthritis (OA) pain and chronic low back pain (LBP). Its use for antidepressant and anxiolytic actions has been extensively reviewed previously. We here review the evidence for the efficacy of 60 mg once-daily dosing of duloxetine for chronic pain conditions.

METHOD

The literature was searched for clinical trials in humans conducted in the past 10 years involving duloxetine.

RESULTS

There were 199 results in the initial search. Studies not in the English language were excluded. We then included only studies of diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain (OA and LBP). Studies of painful symptoms reported in mental health studies were excluded. This resulted in 32 studies. Articles that did not include a 60 mg/day daily dose as a study arm were excluded. This resulted in 30 studies, broken down as follows: 12 for diabetic peripheral neuropathy, 9 for fibromyalgia, 6 for LBP, and 3 for OA pain.

CONCLUSIONS

The studies reviewed report that duloxetine 60 mg once-daily dosing is an effective option for the management of diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain due to chronic OA pain and chronic LBP. As these pains are often comorbid with MDD or GAD, duloxetine might possess the pharmacologic properties to be a versatile agent able to address several symptoms in these patients. With adequate attention to FDA prescribing guidance regarding safety and drug-drug interactions, duloxetine 60 mg once-daily dosing appears to be an effective option in the appropriate pain patient population.

Duloxetine in the management of chronic musculoskeletal pain

Chronic musculoskeletal pain is among the most frequent painful complaints that healthcare providers address. The bulk of these complaints are chronic low back pain and chronic osteoarthritis. Osteoarthritis is the most common form of arthritis in the United States. It is a chronic degenerative disorder characterized by a loss of cartilage, and occurs most often in older persons. The management of osteoarthritis and chronic low back pain may involve both nonpharmacologic (eg, weight loss, resistive and aerobic exercise, patient education, cognitive behavioral therapy) and pharmacologic approaches. Older adults with severe osteoarthritis pain are more likely to take analgesics than those with less severe pain. The pharmacologic approaches to painful osteoarthritis remain controversial, but may include topical as well as oral nonsteroidal antiinflammatory drugs, acetaminophen, duloxetine, and opioids. The role of duloxetine for musculoskeletal conditions is still evolving.

Should Rheumatologists be Managing Fibromyalgia?

Fibromyalgia has always struggled to be taken seriously. The vague mixture of aches, pains, stiffness and fatigue with no clear clinical or investigational findings has led many to doubt its very existence. Evidence is accumulating, however, of demonstrable abnormalities of pain processing and psychosocial factors in fibromyalgia subjects. These may ‘prove’ its existence, but do they suggest it is rheumatological?

Pregabalin suppresses spinal neuronal hyperexcitability and visceral hypersensitivity in the absence of peripheral pathophysiology

BACKGROUND

Opioid-induced hyperalgesia is recognized in the laboratory and the clinic, generating central hyperexcitability in the absence of peripheral pathology. We investigated pregabalin, indicated for neuropathic pain, and ondansetron, a drug that disrupts descending serotonergic processing in the central nervous system, on spinal neuronal hyperexcitability and visceral hypersensitivity in a rat model of opioid-induced hyperalgesia.

METHODS

Male Sprague-Dawley rats (180-200 g) were implanted with osmotic mini-pumps filled with morphine (90 μg · μl⁻¹ · h⁻¹) or saline (0.9% w/v). On days 7-10 in isoflurane anesthetized animals, we evaluated the effects of (1) systemic pregabalin on spinal neuronal and visceromotor responses, and (2) spinal ondansetron on dorsal horn neuronal response. Messenger ribonucleic acid concentrations of α2δ-1, 5HT3A, and μ-opioid receptor in the dorsal root ganglia of all animals were analyzed.

RESULTS

In morphine-treated animals, evoked spinal neuronal responses were enhanced to a subset of thermal and mechanical stimuli. This activity was attenuated by pregabalin (by at least 71%) and ondansetron (37%); the visceromotor response to a subset of colorectal distension pressures was attenuated by pregabalin (52.8%; n = 8 for all measures, P < 0.05). Messenger ribonucleic acid concentrations were unchanged.

CONCLUSIONS

The inhibitory action of pregabalin in opioid-induced hyperalgesia animals is neither neuropathy-dependent nor reliant on up-regulation of the α₂δ-1 subunit of voltage-gated calcium channels-mechanisms proposed as being essential for pregabalin's efficacy in neuropathy. In opioid-induced hyperalgesia, which extends to colonic distension, a serotonergic facilitatory system may be up-regulated, creating an environment that is permissive for pregabalin-mediated analgesia without peripheral pathology.

Hypofunction of the sympathetic nervous system is an etiologic factor for a wide variety of chronic treatment-refractory pathologic disorders which all respond to therapy with sympathomimetic amines

The hypothesis set forth is that the basis for a great many chronic debilitating conditions that involve almost all of the physiologic systems of the body may have as the underlying cause and a common link between them, i.e., hypofunction of the sympathetic nervous system. The hypothesis considers that one of the main functions of the sympathetic nervous system is to diminish cellular permeability. Thus sympathetic hypofunction may lead to absorption of chemicals and toxins into tissues that were supposed to be impervious leading to inflammation and other adverse consequences which then cause a wide variety of symptoms. These symptoms may include pain or diminished muscular function leading to various pain syndromes or conditions related to diminished muscular function. Furthermore since the sympathetic nervous system is involved in body homeostasis and temperature regulation, sympathetic nervous system hypofunction could lead to disorders in these areas, e.g., vasomotor symptoms and edema. This defect in sympathetic nervous system has a genetic predisposition but relatives, e.g., siblings or children may manifest in a different manner which suggests some influence of external factors causing one physiological system to be more prone than another to malfunction under conditions of sympathetic hypofunction. Evidence to support this hypothesis has been provided by a large number of published anecdotes demonstrating the quick and long lasting considerable improvement in symptoms following treatment with the sympathomimetic amine dextroamphetamine sulfate (with return of symptoms if treatment is temporarily ceased thus diminishing the likelihood of spontaneous remission) despite failure to respond to a plethora of other pharmacologic agents and other therapies over many years. The physiological systems with various chronic disorders that have responded included the gastrointestinal system, skin, genitourinary system, the nervous system, the musculoskeletal system, the temperature regulation system, peripheral vasculature system, and the endocrine system. Despite the multitude of very convincing anecdotal reports showing its efficacy (and to date no reports refuting this hypothesis), there has only been one controlled study which showed the benefit of dextroamphetamine sulfate on edema and weight gain in diet-refractory patients. The flaw to date for general acceptance of this hypothesis is that most positive studies are coming from one clinical center. Furthermore, more controlled studies are needed. There has been a recent interest amongst physiologists and recent studies have been published confirming a deficiency of sympathetic nerve fibers in some of these disorders which hopefully will encourage more research into other physiologic systems leading to corroboration of this hypothesis.

The antioxidant protection of CELLFOOD against oxidative damage in vitro

CELLFOOD (CF) is an innovative nutritional supplement containing 78 ionic/colloidal trace elements and minerals combined with 34 enzymes and 17 amino acids, all suspended in a solution of deuterium sulfate. The aim of this study was to investigate, for the first time, the antioxidant properties of CF in vitro in different model systems. Three pathophysiologically relevant oxidants were chosen to evaluate CF protection against oxidative stress: hydrogen peroxide, peroxyl radicals, and hypochlorous acid. Both biomolecules (GSH and plasmid DNA) and circulating cells (erythrocytes and lymphocytes) were used as targets of oxidation. CF protected, in a dose-dependent manner, both GSH and DNA from oxidation by preserving reduced GSH thiol groups and supercoiled DNA integrity, respectively. At the same time, CF protected erythrocytes from oxidative damage by reducing cell lysis and GSH intracellular depletion after exposure to the oxidant agents. In lymphocytes, CF reduced the intracellular oxidative stress induced by the three oxidants in a dose-dependent manner. The overall in vitro protection of biomolecules and cells against free radical attacks suggests that CF might be a valuable coadjuvant in the prevention and treatment of various physiological and pathological conditions related to oxidative stress, from aging to atherosclerosis, from neurodegeneration to cancer.

Alpha 2 Delta (α(2)δ) Ligands, Gabapentin and Pregabalin: What is the Evidence for Potential Use of These Ligands in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a complex disorder that is characterized by abdominal pain and altered bowel habit, and often associates with other gastrointestinal symptoms such as feelings of incomplete bowel movement and abdominal bloating, and extra-intestinal symptoms such as headache, dyspareunia, heartburn, muscle pain, and back pain. It also frequently coexists with conditions that may also involve central sensitization processes, such as fibromyalgia, irritable bladder disorder, and chronic cough. This review examines the evidence to date on gabapentin and pregabalin which may support further and continued research and development of the α₂δ ligands in disorders characterized by visceral hypersensitivity, such as IBS. The distribution of the α₂δ subunit of the voltage-gated calcium channel, possible mechanisms of action, pre-clinical data which supports an effect on motor–sensory mechanisms and clinical evidence that points to potential benefits in patients with IBS will be discussed.

Pharmacotherapy for fibromyalgia

Fibromyalgia (FM) is a chronic disorder characterized by multifocal pain and other associated somatic symptoms including fatigue, insomnia, cognitive/memory problems, and even psychological distress. It appears that 2–4% of the general population suffers from FM. FM negatively impacts the physical functioning of its patients, as evidenced by difficulties with multiple daily activities, as well as affecting emotional health, social functioning, and health related quality of life. This review will discuss the potential theories that possibly contribute to the pathogenesis of FM, although the precise mechanism is unknown. The evolution of the assessment of FM will also be examined, with the waning use of tender point examinations and the appearance of new simple, practical diagnostic criteria. Although non-pharmacologic therapeutic options (exercise, education, cognitive–behavioral therapy) have been shown to be extremely effective in FM, the focus of this article will be on pharmacologic strategies. Non-Food and Drug Administration (FDA) approved as well as FDA approved agents will be presented. Each agent's therapeutic “niche” in FM management will be discussed based on its pharmacologic profile, patient responsiveness, and tolerability. Finally a clinical algorithm will be presented for the step-wise management of pain and other associated symptoms of FM.

Duloxetine: a review of its safety and efficacy in the management of fibromyalgia syndrome

Fibromyalgia (FM) is a chronic disorder characterized by widespread pain and other associated symptoms including fatigue, insomnia, cognitive/memory problems, and even psychological distress. Duloxetine is one of three FDA approved medications (the other two being milnacipran and pregabalin) for the treatment of FM. It has been demonstrated that FM patients possess low central nervous system levels of serotonin and norepinephrine. Duloxetine, which is classified pharmacologically as a serotonin-norepinephrine reuptake inhibitor (SNRI), may be beneficial for FM patients by increasing these levels. This review will touch briefly upon the pathophysiology of FM, diagnostic tools, currently available therapeutic options (both pharmacologic and non-pharmacologic), as well as the pharmacokinetic/pharmacodynamic properties of duloxetine. In addition, the efficacy and safety/tolerability of duloxetine exclusively in FM will be assessed through examination of 5 randomized controlled trials, as well as pooled analyses of current data. Suggestions for a therapeutic niche for duloxetine in FM are discussed based on a presentation of the characteristics of duloxetine.