Pain analysis in patients with fibromyalgia. Effects of intravenous morphine, lidocaine, and ketamine

Sensory and motor effects of experimental muscle pain in patients with lateral epicondylalgia and controls with delayed onset muscle soreness

This study compares the effect of experimental muscle pain on deep tissue sensitivity and force attenuation in the wrist extensors of patients with lateral epicondylalgia (n=20), and healthy controls (n=20) with experimentally induced sensori-motor characteristics simulating lateral epicondylalgia. Delayed onset muscle soreness (DOMS) in wrist extensors of healthy controls was induced by eccentric exercise in one arm 24h prior to injection (Day 0). Saline-induced pain intensity (visual analogue scale, VAS), distribution, and quality were assessed quantitatively in both arms for both groups. Pressure pain thresholds (PPT) were assessed at three different sites in the wrist extensors. Maximal grip force and wrist extension force were recorded. In response to saline-induced pain in the extensor carpi radialis brevis, regardless of arm, the patient group demonstrated a significantly quicker pain onset (P<0.01), mapped larger pain areas and more referred pain areas, compared to healthy controls (P<0.03). Pain persisted significantly longer in the sore arm of the patient group, compared with all other arms (P<0.02). Patients demonstrated significant bilateral hyperalgesia at extensor carpi radialis brevis during and post saline-induced pain compared to pre-injection and healthy controls (P<0.04). The sore arm in patients and the DOMS arms in healthy subjects showed significantly reduced maximal force (P<0.0001), at all Day 1 times compared with the control arms. In patients, the bilateral increase in deep tissue sensitivity and enlarged referred pain areas during saline-induced pain might suggest involvement of central sensitisation.

EAU Guidelines on Chronic Pelvic Pain

OBJECTIVES

On behalf of the European Association of Urology (EAU) guidelines for diagnosis, therapy and follow-up of chronic pelvic pain patients were established.

METHOD

Guidelines were compiled by a working group and based on current literature following a systematic review using MEDLINE. References were weighted by the panel of experts.

RESULTS

The full text of the guidelines is available through the EAU Central Office and the EAU website (www.uroweb.org). This article is a short version of this text and summarises the main conclusions from the guidelines on management of chronic pelvic pain.

CONCLUSION

A guidelines text is presented including chapters on prostate pain and bladder pain syndromes, urethral pain, scrotal pain, pelvic pain in gynaecological practice, role of the pelvic floor and pudendal nerve, general treatment of chronic pelvic pain and neuromodulation. These guidelines have been drawn up to provide support in the management of the large and difficult group of patients suffering from chronic pelvic pain.

Perioperative intravenous lidocaine has preventive effects on postoperative pain and morphine consumption after major abdominal surgery

Sodium channel blockers are approved for IV administration in the treatment of neuropathic pain states. Preclinical studies have suggested antihyperalgesic effects on the peripheral and central nervous system. Our objective in this study was to determine the time course of the analgesic and antihyperalgesic mechanisms of perioperative lidocaine administration. Forty patients undergoing major abdominal surgery participated in this randomized and double-blinded study. Twenty patients received lidocaine 2% (bolus injection of 1.5 mg/kg in 10 min followed by an IV infusion of 1.5 mg. kg(-1). h(-1)), and 20 patients received saline placebo. The infusion started 30 min before skin incision and was stopped 1 h after the end of surgery. Lidocaine blood concentrations were measured. Postoperative pain ratings (numeric rating scale of 0-10) and morphine consumption (patient-controlled analgesia) were assessed up to 72 h after surgery. Mean lidocaine levels during surgery were 1.9 +/- 0.7 microg/mL. Patient-controlled analgesia with morphine produced good postoperative analgesia (numeric rating scale at rest, <or=3; 90%-95%; no group differences). Patients who received lidocaine reported less pain during movement and needed less morphine during the first 72 h after surgery (103.1 +/- 72.0 mg versus 159.0 +/- 73.3 mg; Student's t-test; P < 0.05). Because this opioid-sparing effect was most pronounced on the third postoperative day, IV lidocaine may have a true preventive analgesic activity, most likely by preventing the induction of central hyperalgesia in a clinically relevant manner.

IMPLICATIONS

The perioperative administration of systemic small-dose lidocaine reduces pain during surgery associated with the development of pronounced central hyperalgesia, presumably by affecting mechanoinsensitive nociceptors, because these have been linked to the induction of central sensitization and were shown to be particularly sensitive to small-dose lidocaine.

Hypersensitivity in muscle pain syndromes

The aim of this review is to present research that has a bearing on the pathogenesis of hypersensitivity in muscle pain syndromes. Allodynia and hyperalgesia in these syndromes can be segmental or generalized and temporary or permanent. Hypersensitivity in muscle pain conditions in the clinic is best diagnosed by determining the pressure pain threshold. In a disorder such as fibromyalgia, decreased pain thresholds also are found at sites where there is no tenderness. Pathogenetic mechanisms for allodynia and hyperalgesia can be identified at several levels of the nociceptive system, from the nociceptors in the muscle to the cortex. Central sensitization of nociceptive neurons in the dorsal horn and a disturbed balance between inhibitory and facilitatory impulses in the descending tracts from the brain stem to the dorsal horn are the main mechanisms for pain hypersensitivity. Changes in function, biochemical make-up, and synaptic connections in the nociceptive neurons in the dorsal horn are considered to be caused by neuronal plasticity.

Will ion-channel blockers be useful for management of nonneuropathic pain?

For neuropathic pain, there is evidence that the analgesic effect of intravenous sodium-channel blockers is robust and dose dependent. Oral agents are less impressive, but efficacious nonetheless, especially at higher doses. Despite the evidence from animal studies for a role of sodium channels in inflammatory hyperalgesia, the clinical evidence of analgesic effect of oral and intravenous sodium channel blockers in both acute and chronic nonneuropathic pain is equivocal. The results to date from human experimental pain models suggest a lack of effect of systemic lidocaine on acute nociceptive pain and that the effect on cutaneous hyperalgesia is modest, at best. Furthermore, the literature suggests that the systemic lidocaine analgesia is both dose and diagnosis dependent.

Ketamine in chronic pain management: an evidence-based review

Ketamine has diverse effects that may be of relevance to chronic pain including: N-methyl-D-aspartic acid, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, gamma-aminobutyric acid(A) receptors; inhibition of voltage gated Na(+) and K(+) channels and serotonin, dopamine re-uptake. Ketamine has been in clinical practice for over 30 yr; however, there has been little formal research on the effectiveness of ketamine for chronic pain management. In this review we evaluate the available clinical data as a basis for defining the potential use of ketamine for chronic pain. Literature referenced in this review was obtained from a computer search of EMBASE and MEDLINE from 1966 through August, 2002. Search terms included ketamine, ketalar, pain, painful, analgesic, and analgesia. Abstracts were screened for relevance and publications relating to chronic pain use were obtained. Levels of evidence were stratified according to accepted guidelines (level I-IV). For central pain, there is level II and level IV evidence of efficacy for parenteral and oral ketamine. For complex regional pain syndromes, there is only level IV evidence of efficacy of epidural ketamine. For fibromyalgia, there is level II evidence of pain relief, reduced tenderness at trigger points, and increased endurance. For ischemic pain, a level II study reported a potent dose-dependent analgesic effect, but with a narrow therapeutic window. For nonspecific neuropathic pain, level II and level IV studies reported divergent results with questionable long-term effects on pain. For phantom limb pain and postherpetic neuralgia, level II and level II studies provided objective evidence of reduced hyperpathia and pain relief was usually substantial either after parenteral or oral ketamine. Acute on chronic episodes of severe neuropathic pain represented the most frequent use of ketamine as a "third line analgesic," often by IV or subcutaneous infusion (level IV). In conclusion, the evidence for efficacy of ketamine for treatment of chronic pain is moderate to weak. However, in situations where standard analgesic options have failed ketamine is a reasonable "third line" option. Further controlled studies are needed.

Pharmacological modulation of experimental phasic and tonic muscle pain by morphine, alfentanil and ketamine in healthy volunteers

BACKGROUND

Muscle pain is a major clinical problem but the underlying mechanisms and its pharmacological modulation need further investigation. This study on 15 volunteers evaluates if two experimental muscle pain models are sensitive to micro -receptor agonists and to an N-methyl-D-aspartate (NMDA)-receptor antagonist.

METHODS

In the left tibialis anterior, intramuscular electrical (IMES) pain thresholds were determined for single (SPTmuscle) and five (RPTmuscle) repeated stimuli. Also pain to suprathreshold stimulation at 150% of RPTmuscle, 10 s, was assessed on a visual analog scale (VAS) as AUCimes (area under the VAS curve). In the right TA muscle, pain intensity on infusion of 0.5 ml of hypertonic saline, 5% (AUCsaline) and pain distribution indicated as local and referred were evaluated. Pain variables were assessed before, during and after intravenous infusions of morphine (10 microg x kg-1 min-1, 10 min), alfentanil (target-controlled infusion, plasma concentration; 60 ng ml-1, 60 min) and ketamine (10 microg x kg-1 min-1, 60 min). All data were normalized to baseline pain values (before drug infusions were initiated) and compared with placebo (midazolam, 2 microg x kg-1 min-1, 10 min).

RESULTS

SPTmuscle increased (log mean values +/- SD, mA) with morphine (0.11 +/- 0.17, P < 0.05), alfentanil (0.28 +/- 0.24, P < 0.001) and ketamine (0.19 +/- 0.18, P < 0.01) as compared with placebo (-0.03 +/- 0.12). Alfentanil and ketamine also increased RPTmuscle (0.25 +/- 0.21, P < 0.01 and 0.21 +/- 0.19, P < 0.05, respectively) as compared with placebo (0.00 +/- 0.17). Pain to IMES (AUCimes) was reduced (median values [25th-75th percentiles], cm x s) by alfentanil and ketamine (-19.7 [-14.6 - -29.6] and-12.8 [-8.3 - -27.8], P < 0.05, respectively) vs. placebo (-0.8 [1.6 - -12.3]). Similar drug effects were seen when pain to infusion of hypertonic saline (AUCsaline) was assessed (alfentanil:-388 [-99 - -677] and ketamine:-326 [-227 - -573], P < 0.05 compared with placebo: 150 [449--240]). Ketamine also reduced the size of the local pain area (-58.4 [-21.2 - -176.1], < 0.05) as compared with placebo (-0.4 [70.6 - -13.4]). The frequency of referred pain was also lower when ketamine was given (3/13, P < 0.05) vs. placebo (9/14).

CONCLUSION

The study demonstrates that experimental muscle pain induced in humans by electrical stimulation and infusion of hypertonic saline is sensitive to pharmacological modulation similar to preclinical animal tests and clinical trials. The data suggest that these models can be valuable tools in analgesic drug development.

Pharmacological therapies in fibromyalgia

The fibromyalgia syndrome (FMS) is a common, chronic, widespread pain disorder that mainly affects middle-aged women. In addition to pain complaints, fatigue and disturbed sleep are symptoms frequently reported by these patients. Many FMS patients also meet diagnostic criteria for mood disorders (e.g. depression) as well as other so-called 'functional somatic syndromes', including irritable bowel syndrome, temporomandibular joint disorder, and subsets of chronic low-back pain. A wide variety of medications are used to manage the eclectic symptomatology of FMS patients, although relatively few have been rigorously tested. This chapter provides a contemporary update of the state of FMS pharmacotherapy, with an emphasis on compounds that have been tested in double-blind, randomized, controlled trials. Particular attention is paid to the efficacy of these therapies on the associated symptoms and co-morbid syndromes commonly seen in FMS patients.

The effectiveness of intravenous ketamine and lidocaine on peripheral neuropathic pain

BACKGROUND

Neuropathic pain is often severe and resistant to pharmacological treatment. The aims of the present study were to assess the analgesic effect of ketamine and lidocaine and to investigate if measurement of different variables of sensibility could be used to identify responders. We also wanted to study if treatment resulted in changes of sensibility.

METHODS

Twelve patients with long-lasting peripheral neuropathic pain of traumatic origin were included. The effects of ketamine hydrochloride (Ketalar, Parke Davis) 0.4 mg/kg and lidocaine hydrochloride (Xylocain, Astra) 2.5 mg/kg were investigated. Saline was used as placebo. The intensity of continuous pain was measured by a visual analogue scale (VAS). Warm and cold perception as well as heat and cold pain thresholds were assessed. Sensibility to touch was also tested. Systemic plasma concentrations of lidocaine and ketamine were assessed.

RESULTS

The mean reduction in VAS-scores was 55%, 34% and 22% for ketamine, lidocaine and placebo, respectively. A significant difference was registered between ketamine and placebo (P = 0.009). Response to treatment (50% reduction in VAS-score during infusion) was recorded in 7/12 in the ketamine, 4/12 in the lidocaine and 2/12 in the placebo group. Quantitative sensory testing (QST) of thermal sensitivity and sensory tests for mechanical stimuli could not separate responders from non-responders and neither were the results from these assessments changed by the infusion of the drugs. Lidocaine and particularly ketamine were associated with frequent side-effects, the most common being somnolence and dizziness.

CONCLUSION

Ketamine showed a significant analgesic effect. The clinical usefulness is, however, limited by disturbing side-effects.

Tricyclic antidepressants and fibromyalgia: what is the mechanism of action?

Fibromyalgia is a chronic pain disorder of which other clinical features, such as persistent fatigue and disordered sleep, may be a secondary consequence. The initial pharmacological approach to treating the disorder is the management of the pain. Tricyclic antidepressants are the most effective drugs in use so far, especially when administered in combination with other therapies (e.g., selective serotonin re-uptake inhibitors), which suggests modulation of the neurotransmitters serotonin and noradrenaline. The effectiveness of amitriptyline and related tricyclic antidepressants, however, is consistent with the involvement of mechanisms, such as potassium channel modulation and NMDA receptor antagonism, in addition to or in place of the modulation of monoamine neurotransmitters. Investigation of the importance of each of the pharmacological properties of amitriptyline and related molecules in the management of fibromyalgia could provide clues for the rational design of new drugs.

Efficacy and adverse effects of intravenous lignocaine therapy in fibromyalgia syndrome

BACKGROUND

To investigate the effects of intravenous lignocaine infusions (IV lignocaine) in fibromyalgia.

METHODS

Prospective study of the adverse effects of IV lignocaine in 106 patients with fibromyalgia; retrospective questionnaire study of the efficacy of IV lignocaine in 50 patients with fibromyalgia.

RESULTS

Prospective study: Two major (pulmonary oedema and supraventricular tachycardia) and 42 minor side-effects were reported. None had long-term sequelae. The commonest was hypotension (17 cases). Retrospective study: Pain and a range of psychosocial measures (on single 11-point scales) improved significantly after treatment. There was no effect of the treatment on work status. The average duration of pain relief after the 6-day course of treatment was 11.5 +/- 6.5 weeks.

CONCLUSIONS

Intravenous lignocaine appears to be both safe and of benefit in improving pain and quality of life for patients with fibromyalgia. This needs to be confirmed in prospective randomised controlled trials.

Enhanced temporal summation of second pain and its central modulation in fibromyalgia patients

We have previously shown that fibromyalgia (FMS) patients have enhanced temporal summation (windup) and prolonged decay of heat-induced second pain in comparison to control subjects, consistent with central sensitization. It has been hypothesized that sensory abnormalities of FMS patients are related to deficient pain modulatory mechanisms. Therefore, we conducted several analyses to further characterize enhanced windup in FMS patients and to determine whether it can be centrally modulated by placebo, naloxone, or fentanyl. Pre-drug baseline ratings of FMS and normal control (NC) groups were compared with determine whether FMS had higher pain sensitivity in response to several types of thermal tests used to predominantly activate A-delta heat, C heat, or cold nociceptors. Our results confirmed and extended our earlier study in showing that FMS patients had larger magnitudes of heat tap as well as cold tap-induced windup when compared with age- and sex-matched NC subjects. The groups differed less in their ratings of sensory tests that rely predominantly on A-delta-nociceptive afferent input. Heat and cold-induced windup were attenuated by saline placebo injections and by fentanyl (0.75 and 1.5 microg/kg). However, naloxone injection had the same magnitudes of effect on first or second pain as that produced by placebo injection. Hypoalgesic effects of saline placebo and fentanyl on windup were at least as large in FMS as compared to NC subjects and therefore do not support the hypothesis that pain modulatory mechanisms are deficient in FMS. To the extent that temporal summation of second pain (windup) contributes to processes underlying hyperalgesia and persistent pain states, these results indirectly suggest that these processes can be centrally modulated in FMS patients by endogenous and exogenous analgesic manipulations.

Effects of NMDA and non-NMDA ionotropic glutamate receptor antagonists on the development and maintenance of hyperalgesia induced by repeated intramuscular injection of acidic saline

Two unilateral injections of pH 4.0 saline into the gastrocnemius muscle result in a bilateral decrease in mechanical withdrawal threshold after the second injection. This decrease is significant by 4h and lasts through 1 week. The purpose of this study was to characterize the involvement of both N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors in the spinal cord dorsal horn in the development and maintenance of mechanical hyperalgesia from repeated intramuscular injections of acidic saline. 2-amino-5-phosphonovaleric acid (AP5) (2-20 nmol, 10 microl, pH 7) or 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo[f]quinoxaline-7-sulfonamide (NBQX) (1-10 nmol, 10 microl, pH 8-9) was administered intrathecally to the lumbar spinal cord to block NMDA and non-NMDA ionotropic glutamate receptors in the dorsal horn, respectively. Drugs were administered at one of three different time points: (1) prior to the first intramuscular injection of pH 4.0 saline on Day 0, (2) prior to the second intramuscular injection of pH 4.0 saline on Day 5, and (3) 1 week after the second injection. Mechanical withdrawal thresholds were measured with von Frey filaments before, 4h, and 24h after injection 1 and before, 4h, 24h, and 1 week after injection 2. AP5 had no effect on mechanical withdrawal thresholds when administered prior to the first intramuscular injection of pH 4.0 saline. When AP5 was administered before the second intramuscular injection, the bilateral decrease in mechanical withdrawal thresholds was delayed for up to 24h. Intrathecal administration of AP5 1 week after the second intramuscular injection of pH 4.0 saline produced a bilateral increase in mechanical withdrawal thresholds. Blockade of non-NMDA glutamate receptors in the spinal cord dorsal horn prior to either the first or second intramuscular injection of pH 4.0 saline had no effect on the development of mechanical hyperalgesia. However, spinal injection of NBQX 1 week after the second intramuscular injection of pH 4.0 saline resulted in an increase in mechanical withdrawal thresholds when compared to vehicle controls. These data suggest that both NMDA and non-NMDA glutamate receptors are involved in the maintenance of chronic, muscle-induced hyperalgesia.

The rational management of fibromyalgia patients

The exponential increase in pain research over the last 10 years has established fibromyalgia (FM) as a common chronic pain syndrome with similar neurophysiologic aberrations to other chronic pain states. As such, the pathogenesis is considered to involve an interaction of augmented sensory processing (central sensitization) and peripheral pain generators. The notion, that FM symptomatology results from an amplification of incoming sensory impulses, has revolutionized the contemporary understanding of this enigmatic problem and provided a more rational approach to treatment. To date, the management of FM has been mainly palliative, with the aims of reducing pain, improving sleep, maintaining function, treating psychologic distress and diminishing the impact of associated syndromes. The rapidly evolving neurophysiologic, psychophysiologic and molecular biologic basis for chronic pain states has already opened up new avenues for management which should be applicable to this difficult group of patients. Indeed, it is now possible to think about a "rational" approach to managing FM patients that was unthinkable just a few years ago.

The promise of N-methyl-D-aspartate receptor antagonists in fibromyalgia

There is strong evidence that intravenous administration of ketamine following a standardized protocol could be used as a diagnostic test for a central sensitization in the central nervous system in patients with FM. The combination of a weak opioid and an NMDA-receptor antagonist with few side effects is presently a promise for treatment of pain in a subgroup of patients with FM. The response to intravenously administered ketamine may help select patients for this treatment modality.

The neuropharmacology of centrally-acting analgesic medications in fibromyalgia

As demonstrated above, the anatomy and neuropharmacology of the pain pathways within the CNS, even to the level of the midbrain, are extraordinarily complex. Indeed, discussions of the effects of these agents on the neuropharmacology of the thalamus, hypothalamus, and cortex were excluded from this review owing to their adding further to this complexity. Also, the dearth of data regarding FMS pain pathophysiology necessitated a relatively generic analysis of the pain pathways. As mentioned in the introduction, the current thought is that central sensitization plays an important role in FMS. However, we see in this chapter that the behavioral state of central sensitization may be a result of alterations in either the ascending systems or in one or more descending systems. Studies to assess the presence or relative importance of such changes in FMS are difficult to perform in humans, and to date there are no animal models of FMS. Accepting these limitations, it is apparent that many drugs considered to date for the treatment of FMS do target a number of appropriate sites within both the ascending and descending pain pathways. The data regarding clinical efficacy on some good candidate agents, however, is extremely preliminary. For example, it is evident from the present analysis that SNRIs, alpha 2 agonists, and NK1 antagonists may be particularly well suited to FMS, although current data supporting their use is either anecdotal or from open-label trials [114,149]. Other sites within the pain pathways have not yet been targeted. Examples of these include the use of CCKB antagonists to block on-cell activation or of nitric oxide synthetase antagonists to block the downstream mediators of NMDA activation. Efficacy of such agents may give considerable insight into the pathophysiology of FMS. Finally, as indicated previously, FMS consists of more than just chronic pain, and the question of how sleep abnormalities, depression, fatigues, and so forth tie into disordered pain processing is being researched actively. Future research focusing on how the various manifestations of FMS relate to one another undoubtedly will lead to a more rational targeting of drugs in this complex disorder.

Rational and targeted pharmacologic treatment of fibromyalgia

Despite disappointing results when subjected to randomized clinical trials, pharmacologic agents remain an important component of FM management. Addressing the main symptoms of pain, disturbed sleep, mood disturbances, fatigue, and associated conditions is essential to improve patient functioning and enhanced quality of life. However, much work remains to design clinical trials which address the complexity of FM, while satisfying evidence based medicine paradigms.

Management of fibromyalgia: what are the best treatment choices?

Fibromyalgia still represents an enigma to modern medicine and the aetiopathogenesis is far from explored. The management of patients with fibromyalgia is thus mostly based on empirical research, and only a few controlled studies have been performed. Basic drug therapy rests on the administration of amitriptyline and conventional analgesics. Such therapy should be initiated only after careful patient information and delineation of therapeutic goals are provided. Any drug therapy should be administered in combination with physical treatment and cognitive behavioural therapy. Because of the appearing contours of pathogenic mechanisms, hopefully a number of new drugs will be available to the patients with this complex pain syndrome in the near future.

The meaning of fatigue and tiredness as narrated by women with fibromyalgia and healthy women

1. The aim of this study was to elucidate the meaning of fatigue and tiredness as narrated by women with fibromyalgia (FM) and healthy women. Twenty-five women with FM were interviewed with a narrative approach about the meaning of the lived experience of fatigue and tiredness. A reference group of 25 healthy women was interviewed about the same topic. 2. A phenomenological-hermeneutic method inspired by the French philosopher Ricoeur was used to interpret the interview text. 3. The meaning of fatigue and tiredness was related differently by women with FM and healthy women. The findings are presented in four major themes for women with FM -- the body as a burden, an absent presence, an interfering obstacle and being in hope of alleviation -- and in one major theme for healthy women: needing recovery. 4. Women with FM narrated fatigue as making it obvious that I have a body, instead of I am my body; the lived body becomes urgently present, as an 'it'. Healthy women narrated tiredness as a natural phenomenon when they need recovery and time to rest. 5. The findings are interpreted in the light of the phenomenological work on the lived body by Leder, Toombs and Merleau-Ponty.

Neuroendocrine and immune aspects of fibromyalgia

Fibromyalgia is a form of non-articular rheumatism characterised by long term (>3 months) and widespread musculoskeletal aching, stiffness and pressure hyperalgesia at characteristic soft tissue sites, called soft tissue tender points. The biophysiology of fibromyalgia, however, has remained elusive and the treatment remains mainly empirical. This article reviews the neuroendocrine-immune pathophysiology of fibromyalgia. There is no major evidence that fibromyalgia is accompanied by activation of the inflammatory response system, by immune activation or by an inflammatory process. There is some evidence that fibromyalgia is accompanied by some signs of immunosuppression, suggesting that immunomodifying drugs could have potential in the treatment of fibromyalgia. Recent trials with cytokines, such as interferon-alpha, have been undertaken in patients with fibromyalgia. Immunotherapy with these agents, however, may induce symptoms reminiscent of fibromyalgia and depression in a considerable number of patients. Lowered serum activity of prolyl endopeptidase (PEP), a cytosolic endopeptidase that cleaves peptide bonds on the carboxyl side of proline in proteins of relatively small molecular mass, may play a role in the biophysiology of fibromyalgia through diminished inactivation of algesic and depression-related peptides, e.g. substance P. Trials with PEP agonists could be worthwhile in fibromyalgia. The muscle energy depletion hypothesis of fibromyalgia is supported by findings that this condition is accompanied by lowered plasma levels of branched chain amino acids (BCAAs), i.e. valine, leucine and isoleucine. Since there is evidence that BCAA supplementation decreases muscle catabolism and has ergogenic values, a supplemental trial with BCAAs in fibromyalgia appears to be justified.

Neuroendocrine mechanisms in fibromyalgia-chronic fatigue

Fibromyalgia and chronic fatigue syndrome are poorly understood disorders that share similar demographic and clinical characteristics. Because of the clinical similarities between both disorders it was suggested that they share a common pathophysiological mechanism, namely, central nervous system dysfunction. This chapter presents data demonstrating neurohormonal abnormalities, abnormal pain processing and autonomic nervous system dysfunction in fibromyalgia and chronic fatigue syndrome. The possible contribution of the central nervous system dysfunction to the development and symptomatology of these conditions is discussed. The chapter concludes by reviewing the effect of current treatments and emerging therapeutic modalities in fibromyalgia and chronic fatigue syndrome.

Transitions experienced by women with fibromyalgia

Fibromyalgia (FM) is a chronic pain syndrome the hallmarks of which are a chronic diffuse musculoskeletal pain, tender points, and fatigue. The majority of those who have FM are middle-aged women. The aim of this study was to illuminate the transitions experienced by women with FM. Twenty-five women with FM were interviewed about living with FM. The interviews were analyzed using thematic content analysis. The analysis revealed five categories; transitions in patterns of daily life, family life, social life, and working life, and learning to live with the changes brought about by FM. The categories were subsumed into one theme: FM as the choreographer of activity and relationships. The transitions experienced were illuminated in a core story. The experience of transitions is apparently something that is invisible to almost everyone except the women themselves. Paradoxically, the women described transitions in life due to the illness, but they felt that other people saw them as healthy. It is like living in two worlds simultaneously, the world of the sick and the world of the healthy.

Pharmacologic treatment of fibromyalgia

Fibromyalgia is a chronic syndrome characterized by widespread pain, unrefreshed sleep, disturbed mood, and fatigue. Until such time as we have a clearer understanding of the trigger and/or pathophysiologic mechanisms producing these symptoms, pharmacologic treatment should be aimed at individual symptoms. Such treatment should ideally be offered as part of a multidisciplinary treatment program using both pharmacologic and nonpharmacologic treatment modalities. Critical components of any successful fibromyalgia treatment program include addressing physical fitness, work and other functional activities, and mental health, in addition to symptom-specific therapies. The main symptoms that should be addressed include pain, sleep disturbances including restless leg syndrome, mood disturbances, and fatigue. Pharmacologic therapy should also be considered for syndromes commonly associated with fibromyalgia including irritable bowel syndrome, interstitial cystitis, migraine headaches, temporomandibular joint dysfunction, dysequilibrium including neurally mediated hypotension, sicca syndrome, and growth hormone deficiency. This article provides general guidelines in initiating a successful pharmacologic treatment program for fibromyalgia.

Common etiology of posttraumatic stress disorder, fibromyalgia, chronic fatigue syndrome and multiple chemical sensitivity via elevated nitric oxide/peroxynitrite

Three types of overlap occur among the disease states chronic fatigue syndrome (CFS), fibromyalgia (FM), multiple chemical sensitivity (MCS) and posttraumatic stress disorder (PTSD). They share common symptoms. Many patients meet the criteria for diagnosis for two or more of these disorders and each disorder appears to be often induced by a relatively short-term stress which is followed by a chronic pathology, suggesting that the stress may act by inducing a self-perpetuating vicious cycle. Such a vicious cycle mechanism has been proposed to explain the etiology of CFS and MCS, based on elevated levels of nitric oxide and its potent oxidant product, peroxynitrite. Six positive feedback loops were proposed to act such that when peroxynitrite levels are elevated, they may remain elevated. The biochemistry involved is not highly tissue-specific, so that variation in symptoms may be explained by a variation in nitric oxide/peroxynitrite tissue distribution. The evidence for the same biochemical mechanism in the etiology of PTSD and FM is discussed here, and while less extensive than in the case of CFS and MCS, it is nevertheless suggestive. Evidence supporting the role of elevated nitric oxide/peroxynitrite in these four disease states is summarized, including induction of nitric oxide by common apparent inducers of these disease states, markers of elevated nitric oxide/peroxynitrite in patients and evidence for an inductive role of elevated nitric oxide in animal models. This theory appears to be the first to provide a mechanistic explanation for the multiple overlaps of these disease states and it also explains the origin of many of their common symptoms and similarity to both Gulf War syndrome and chronic sequelae of carbon monoxide toxicity. This theory suggests multiple studies that should be performed to further test this proposed mechanism. If this mechanism proves central to the etiology of these four conditions, it may also be involved in other conditions of currently obscure etiology and criteria are suggested for identifying such conditions.

Potential mechanisms in chemical intolerance and related conditions

The symptom of chemical intolerance may occur in isolation, but often occurs in conjunction with other chronic symptoms such as pain, fatigue, memory disturbances, etc. This frequent clustering of symptoms in individuals has led to the definition of several chronic multisymptom syndromes, such as multiple chemical sensitivity, fibromyalgia, chronic fatigue syndrome, and Gulf War illnesses. The aggregate research into these syndromes has suggested some unifying mechanisms that contribute to symptomatology. Multiple lines of evidence suggest that there is aberrant function of numerous efferent neural pathways, such as the autonomic nervous system and hypothalamic-pituitary axes, in subsets of individuals with these conditions. There is perhaps the greatest evidence for abnormal sensory processing in these syndromes, with a low "unpleasantness threshold" for multiple types of sensory stimuli. Psychological and behavioral factors are known to play a significant role in initiating or perpetuating symptoms in some persons with these illnesses. In the field of pain research, the interrelationship between physiologic and psychologic factors in symptom expression has been well studied. Using both established and novel methodologies, studies have suggested that psychologic factors such as hypervigilance and expectancy are playing a relatively minor role in most individuals with fibromyalgia and that clear evidence exists of physiologic amplification of sensory stimuli. These studies need to be extended to more sensory tasks and to larger numbers of subjects with related conditions. It is of note, though, that existing data on this spectrum of illnesses would suggest that there may be greater psychologic contributions to symptomatology if an illness is defined in part by behavior (e.g., avoidance of chemical exposures) rather than on the basis of symptoms alone.

Glutamate receptors and nociception: implications for the drug treatment of pain

Evidence from the last several decades indicates that the excitatory amino acid glutamate plays a significant role in nociceptive processing. Glutamate and glutamate receptors are located in areas of the brain, spinal cord and periphery that are involved in pain sensation and transmission. Glutamate acts at several types of receptors, including ionotropic (directly coupled to ion channels) and metabotropic (directly coupled to intracellular second messengers). Ionotropic receptors include those selectively activated by N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid and kainate. Metabotropic glutamate receptors are classified into 3 groups based on sequence homology, signal transduction mechanisms and receptor pharmacology. Glutamate also interacts with the opioid system, and intrathecal or systemic coadministration of glutamate receptor antagonists with opioids may enhance analgesia while reducing the development of opioid tolerance and dependence. The actions of glutamate in the brain seem to be more complex. Activation of glutamate receptors in some brain areas seems to be pronociceptive (e.g. thalamus, trigeminal nucleus), although activation of glutamate receptors in other brain areas seems to be antinociceptive (e.g. periaqueductal grey, ventrolateral medulla). Application of glutamate, or agonists selective for one of the several types of glutamate receptor, to the spinal cord or periphery induces nociceptive behaviours. Inhibition of glutamate release, or of glutamate receptors, in the spinal cord or periphery attenuates both acute and chronic pain in animal models. Similar benefits have been seen in studies involving humans (both patients and volunteers); however, results have been inconsistent. More research is needed to clearly define the role of existing treatment options and explore the possibilities for future drug development.

Targeting the N-methyl-D-aspartate receptor for chronic pain management. Preclinical animal studies, recent clinical experience and future research directions

A 1967-1999 MEDLINE search of published reports evaluating the role of the glutamate N-methyl-D-aspartate (NMDA) receptor in pain identified 378 animal studies and 132 human studies. There is convincing evidence in these studies that the NMDA receptor mediates prolonged nociceptive behaviors in animal models and various chronic pain symptoms in the clinical population. Administration of older compounds, such as ketamine, dextromethorphan, and amantadine, which are now known to act as NMDA receptor antagonists, have recently been shown to alleviate chronic pain. For years, the pharmaceutical industry has been attempting to produce novel compounds that modulate NMDA receptor activity; however, the adverse effects associated with this class of drugs have prevented their widespread clinical use. Collaborative studies between basic researchers, clinical scientists, and clinicians are needed to delineate characteristics of NMDA receptor antagonism that predict optimal analgesic activity and an acceptable toxicity profile in patients with chronic pain.

Central sensitization in tension-type headache--possible pathophysiological mechanisms

The aim of the present thesis was to investigate the pathophysiology of chronic tension-type headache with special reference to central mechanisms. Increased tenderness to palpation of pericranial myofascial tissues is the most apparent abnormality in patients with tension-type headache. A new piece of equipment, a so-called palpometer, that makes it possible to control the pressure intensity exerted during palpation, was developed. Thereafter, it was demonstrated that the measurement of tenderness could be compared between two observers if the palpation pressure was controlled, and that the Total Tenderness Scoring system was well suited for the scoring of tenderness during manual palpation. Subsequently, it was found that pressure pain detection and tolerance thresholds were significantly decreased in the finger and tended to be decreased in the temporal region in chronic tension-type headache patients compared with controls. In addition, the electrical pain threshold in the cephalic region was significantly decreased in patients. It was concluded that the central pain sensitivity was increased in the patients probably due to sensitization of supraspinal neurones. The stimulus-response function for palpation pressure vs. pain was found to be qualitatively altered in chronic tension-type headache patients compared with controls. The abnormality was related to the degree of tenderness and not to the diagnosis of tension-type headache. In support of this, the stimulus-response function was found to be qualitatively altered also in patients with fibromyalgia. It was concluded that the qualitatively altered nociception was probably due to central sensitization at the level of the spinal dorsal horn/trigeminal nucleus. Thereafter, the prophylactic effect of amitriptyline, a non-selective serotonin (5-HT) reuptake inhibitor, and of citalopram, a highly selective 5-HT reuptake inhibitor, was examined in patients with chronic tension-type headache. Amitriptyline reduced headache significantly more than placebo, while citalopram had only a slight and insignificant effect. It was concluded that the blockade of 5-HT reuptake could only partly explain the efficacy of amitriptyline in tension-type headache, and that also other actions of amitriptyline, e.g. reduction of central sensitization, were involved. Finally, the plasma 5-HT level, the platelet 5-HT level and the number of platelet 5-HT transporters were found to be normal in chronic tension-type headache. On the basis of the present and previous studies, a pathophysiological model for tension-type headache is presented. According to the model, the main problem in chronic tension-type headache is central sensitization at the level of the spinal dorsal horn/trigeminal nucleus due to prolonged nociceptive inputs from pericranial myofascial tissues. The increased nociceptive input to supraspinal structures may in turn result in supraspinal sensitization. The central neuroplastic changes may affect the regulation of peripheral mechanisms and thereby lead to, for example, increased pericranial muscle activity or release of neurotransmitters in the myofascial tissues. By such mechanisms the central sensitization may be maintained even after the initial eliciting factors have been normalized, resulting in the conversion of episodic into chronic tension-type headache. Future basic and clinical research should aim at identifying the source of peripheral nociception in order to prevent the development of central sensitization and at ways of reducing established sensitization. This may lead to a much needed improvement in the treatment of chronic tension-type headache and other chronic myofascial pain conditions.

Evidence for metabolic abnormalities in the muscles of patients with fibromyalgia

Widespread muscle pain, fatigue, and weakness are defining characteristics of patients with fibromyalgia (FM). The aim of this review is to summarize recent investigations of muscle abnormalities in FM, which can be classified as structural, metabolic, or functional in nature. Histologic muscle abnormalities of membranes, mitochondria, and fiber type have been well described at both the light microscopic and ultrastructural levels. These structural abnormalities often correlate with biochemical abnormalities, defective energy production, and the resultant dysfunction of FM muscles. The observed abnormalities in FM muscles are consistent with neurologic findings and disturbances in the hypothalamic-pituitary-adrenal axis. Functional changes in FM muscles are assessed most directly by strength and endurance measurements, but pain and psychologic factors may interfere with accurate assessments. To compensate for diminished effort, the decreased efficiency of the work performance by patients with FM can be verified from P-31 magnetic resonance spectroscopy (MRS) data by calculation of the work/energy-cost ratio for various tasks. In the disease course, muscle abnormalities may be elicited by intrinsic changes within the muscle tissue itself and/or extrinsic neurologic and endocrine factors. The accurate assignment of intrinsic or extrinsic factors has been substantially clarified by a recent surge of experimental findings. Irrespective of the multifaceted causes of muscle dysfunction and pain, an in-depth understanding of the muscle defects may provide ideas for characterization of the underlying pathogenesis and development of new therapeutic approaches for fibromyalgia syndrome.

Ketamine reduces muscle pain, temporal summation, and referred pain in fibromyalgia patients

Central mechanisms related to referred muscle pain and temporal summation of muscular nociceptive activity are facilitated in fibromyalgia syndrome (FMS) patients. The present study assessed the effects of an NMDA-antagonist (ketamine) on these central mechanisms. FMS patients received either i.v. placebo or ketamine (0.3 mg/kg, Ketalar((R))50% decrease in pain intensity at rest by active drug on two consecutive VAS assessments). Fifteen out of 17 ketamine-responders were included in the second part of the study. Before and after ketamine or placebo, experimental local and referred pain was induced by intramuscular (i.m.) infusion of hypertonic saline (0.7 ml, 5%) into the tibialis anterior (TA) muscle. The saline-induced pain intensity was assessed on an electronic VAS, and the distribution of pain drawn by the subject. In addition, the pain threshold (PT) to i.m. electrical stimulation was determined for single stimulus and five repeated (2 Hz, temporal summation) stimuli. The pressure PT of the TA muscle was determined, and the pressure PT and pressure pain tolerance threshold were determined at three bilaterally located tenderpoints (knee, epicondyle, and mid upper trapezius). VAS scores of pain at rest were progressively reduced during ketamine infusion compared with placebo infusion. Pain intensity (area under the VAS curve) to the post-drug infusion of hypertonic saline was reduced by ketamine (-18. 4+/-0.3% of pre-drug VAS area) compared with placebo (29.9+/-18.8%, P<0.02). Local and referred pain areas were reduced by ketamine (-12. 0+/-14.6% of pre-drug pain areas) compared with placebo (126.3+/-83. 2%, P<0.03). Ketamine had no significant effect on the PT to single i.m. electrical stimulation. However, the span between the PT to single and repeated i.m. stimuli was significantly decreased by the ketamine (-42.3+/-15.0% of pre-drug PT) compared with placebo (50. 5+/-49.2%, P<0.03) indicating a predominant effect on temporal summation. Mean pressure pain tolerance from the three paired tenderpoints was increased by ketamine (16.6+/-6.2% of pre-drug thresholds) compared with placebo (-2.3+/-4.9%, P<0.009). The pressure PT at the TA muscle was increased after ketamine (42.4+/-9. 2% of pre-drug PT) compared with placebo (7.0+/-6.6%, P<0.011). The present study showed that mechanisms involved in referred pain, temporal summation, muscular hyperalgesia, and muscle pain at rest were attenuated by the NMDA-antagonist in FMS patients. It suggested a link between central hyperexcitability and the mechanisms for facilitated referred pain and temporal summation in a sub-group of the fibromyalgia syndrome patients. Whether this is specific for FMS patients or a general phenomena in painful musculoskeletal disorders is not known.

Effects of staphylococcus toxoid vaccine on pain and fatigue in patients with fibromyalgia/chronic fatigue syndrome

Positive results of pilot studies of the effect of staphylococcus toxoid vaccine in patients with fibromyalgia and chronic fatigue syndrome were the incitement to the present, placebo-controlled study. It included 28 patients who fulfilled the criteria for both fibromyalgia and chronic fatigue syndrome. The effect of vaccination with a staphylococcus toxoid was compared with the effect of injections of sterile water. Psychometric assessment was made using 15 items from the comprehensive psychopathological rating scale (CPRS), Zung's self-rating depression scale and clinical global impressions (CGI). The visual analogue scale (VAS) was used to measure pain levels, and a hand-held electronic pressure algometer was used to measure pressure pain thresholds. Significant improvement was seen in seven of the 15 CPRS items in the vaccine group when pretreatment values were compared to post-treatment values. In CPRS <<fatiguability>>, there were significant intergroup differences, and in CPRS <<pain>> intergroup differences bordered on significance. There was no significant improvement in CPRS items in the placebo group. Clinical global impressions showed significant improvement in the vaccine-treated group, and VAS did so in both groups. In a follow-up study of 23 patients, the vaccine treatment was continued for 2-6 years. Fifty percent were rehabilitated successfully and resumed half-time or full-time work. The results of this study support the authors>> hypothesis that treatment with staphylococcus toxoid may be a fruitful strategy in patients with fibromyalgia and chronic fatigue syndrome. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.

Low-dose lidocaine reduces secondary hyperalgesia by a central mode of action

Sodium channel blockers are approved for intravenous administration in the treatment of neuropathic pain states. Preclinical studies have suggested antihyperalgesic effects on the peripheral as well as the central nervous system. The objective of this study was to determine mechanisms of action of low-dose lidocaine in experimental induced, secondary hyperalgesia. In a first experimental trial, participants (n=12) received lidocaine systemically (a bolus injection of 2 mg/kg in 10 min followed by an intravenous infusion of 2 mg kg(-1)h(-1) for another 50 min). In a second trial, a modified intravenous regional anesthesia (IVRA) was administered to exclude possible central analgesic effects. In one arm, patients received an infusion of 40 ml lidocaine, 0.05%; in the other arm 40 ml NaCl, 0.9%, served as a control. In both trials capsaicin, 20 microgram, was injected intradermally and time course of capsaicin-induced pain, allodynia and hyperalgesia as well as axon reflex flare was determined. The capsaicin-induced pain was slightly reduced after systemic and regional application of the anesthetic. The area of pin-prick hyperalgesia was significantly reduced by systemic lidocaine, whereas the inhibition of hyperalgesia was absent during regional administration of lidocaine. In contrast, capsaicin-induced flare was significantly decreased after both treatments. We conclude that systemic lidocaine reduces pin-prick hyperalgesia by a central mode of action, which could involve blockade of terminal branches of nociceptors. A possible role for tetrodotoxin resistant sodium channels in the antihyperalgesic effect of low-dose lidocaine is discussed.

Generalised muscular hyperalgesia in chronic whiplash syndrome

The whiplash syndrome has immense socio-economic impact. Despite extensive studies over the past years, the mechanisms involved in maintaining the pain in chronic whiplash patients are poorly understood. The aim of the present experimental study was to examine the muscular sensibility in areas within and outside the region involved in the whiplash trauma. Eleven chronic whiplash patients and 11 sex and age matched control subjects were included in the study. Before the experiment, the whiplash patients had pain in the neck and shoulder region with radiating pain to the arm. Five patients reported pain that was more widespread. The somatosensory sensibility in the areas over the infraspinatus, brachioradial, and anterior tibial muscles was assessed by pressure stimulation, pin-prick stimulation, and cotton swap stimulation. Infusion of hypertonic saline (5.85%, 0.5 ml) into the infraspinatus and anterior tibial muscles was performed to assess the muscular sensibility and referred pain pattern. The saline-induced muscle pain intensity was assessed on a continuous visual analogue scale (VAS). The distribution of pain was drawn on an anatomical map. The pressure pain thresholds were significantly lower in patients (P<0. 01) compared with controls: infraspinatus (mean 152.2 vs. 172.7 kPa), brachioradial (mean 70.0 vs. 363.8 kPa), and anterior tibial muscle (mean 172.7 vs. 497.8 kPa). The skin sensibility to pin-prick stimulation and cotton swap stimulation was not different between patients and controls. Infusion of hypertonic saline caused significantly higher VAS scores with longer duration in patients compared to control subjects (P<0.01). The area under the VAS-time curve was significantly (P<0.01) increased in patients compared to control subjects after injection into the infraspinatus muscle (mean 4138.1 vs. 780.0 cm s) and anterior tibial muscle (mean 4370.8 vs. 978.7 cm s). The saline infusion caused local pain defined as pain located around the injection site and referred pain areas not included in the local pain area. The area of local and referred pain were significantly larger in patients compared to control subjects (P<0.01). In the control group, the referred pain areas to infusion of hypertonic saline into the anterior tibial muscle were found at the dorsal aspect of the ankle. In contrast, the areas of referred pain were quite widespread in the patient group with both distal and proximal referred pain areas. In the present study, muscular hyperalgesia and large referred pain areas were found in patients with chronic whiplash syndrome compared to control subjects both within and outside the traumatised area. The findings suggest a generalised central hyperexcitability in patients suffering from chronic whiplash syndrome. This indicates that the pain might be considered as a neurogenic type of pain, and new pharmacological treatments should be investigated accordingly.

Drug therapy

Because of the lack of understanding of the basis of fibromyalgia, therapy remains empiric. This article reviews the different drug elements used in fibromyalgia, including psychotropic agents (antidepressants, sedatives and hypnotics), anti-inflammatories, analgesics and other pharmacological compounds. The strength of evidence for the therapeutic effect of each medicinal modality is presented, with the emphasis on results of randomized controlled trials. The importance of the expected effects of the current drug modalities, and whether these drugs have short- or long-term effects, are also discussed. Future directions, including testing of newer antidepressants, analgesics and non-steroidal anti-inflammatory drugs (Cox-2 selective inhibitors), as well as the need for long-term comparative trials of both drug efficacy and toxicity, are discussed.

Analgesic effect of oral ketamine in chronic neuropathic pain of spinal origin: a case report

Ketamine is an injectable anesthetic induction agent that has been reported to have analgesic activity in pain from a variety of mechanisms, but predominantly in neuralgic and dysesthetic neuropathic pain. In this case report we illustrate the effectiveness of ketamine in a patient with neuropathic pain resulting from cauda equina trauma. Among the issues addressed are the role of pretreatment with haloperidol to prevent ketamine-induced psychomimetic effects, the potential for fewer side effects and a need for lower doses when ketamine is administered orally, and the need for further study regarding appropriate monitoring parameters during the titration phase. Oral ketamine can be effective in treatment refractory chronic neuropathic pain of spinal origin.

Emerging concepts in the neurobiology of chronic pain: evidence of abnormal sensory processing in fibromyalgia

Chronic pain often differs from acute pain. The correlation between tissue pathology and the perceived severity of the chronic pain experience is poor or even absent. Furthermore, the sharp spatial localization of acute pain is not a feature of chronic pain; chronic pain is more diffuse and often spreads to areas beyond the original site. Of importance, chronic pain seldom responds to the therapeutic measures that are successful in treating acute pain. Physicians who are unaware of these differences may label the patient with chronic pain as being neurotic or even a malingerer. During the past decade, an exponential growth has occurred in the scientific underpinnings of chronic pain states. In particular, the concept of nonnociceptive pain has been refined at a physiologic, structural, and molecular level. This review focuses on this new body of knowledge, with particular reference to the chronic pain state termed "fibromyalgia."

Pain in fibromyalgia

Just as our caveman forebears were frail in the face of predatory animals, we are frail in today's society of childhood neglect or abuse, bumper-to-bumper traffic, frustration at work, and multiple daily hassles. The same neuroendocrine systems and pain regulatory mechanisms that protected early man during acute stress are still encoded in our genome, but may be maladaptive in psychologically and physiologically vulnerable people faced with chronic stress. Many patients with fibromyalgia become vulnerable because of the long-lasting psychological and neurophysiological effects of negative experiences in childhood. Ill-equipped with positive cognitive, emotional, and behavioral skills as adults, they display maladaptive coping strategies, low self-efficacy, and negative mood when confronted with the inevitable stressors of life. Psychological distress ensues, which reduces thresholds for pain perception and tolerance (already relatively low in women) even further. Converging lines of psychological and neurobiological evidence strongly suggest that chronic stress-related blunting of the HPA, sympathetic, and other axes of the stress response together with associated alterations in pain regulatory mechanisms may finally explain the pain and fatigue of fibromyalgia. Vulnerable people who can be classified by the ACR criteria as having fibromyalgia do not have a discrete disease. They are simply the most ill in a continuum of distress, chronic pain, and painful tender points in the general population.

Advances in the treatment of fibromyalgia: current status and future directions

Despite significant efforts devoted to understanding the etiopathogenesis of fibromyalgia, its treatment still presents a challenge to practicing clinicians, who must recognize the disorder and quantify the different symptoms in order to treat it. This article discusses recent research to identify sensitive and reliable measures for determining response to treatment among patients with FM, and the elements of therapeutic programs (pharmacologic and nonpharmacologic) for patients with FM along with the empirical or theoretical basis for their use. Future directions, including the need for systematic, controlled outcome studies of therapies and evaluation of variables which may mediate the effects of treatment, as well as demonstration that the effects produced in outcome studies generalize to settings beyond those in which the studies are initially conducted, are also discussed.

Systemic local-anaesthetic-type drugs in chronic pain: a systematic review

Basic research indicates that systemic local-anaesthetic-type drugs that block sodium channels are effective in pain due to nerve damage. These drugs were first used as analgesics in the 1950s and they are still commonly used to try to relieve neuropathic pain and incident pain caused by cancer. As they are potentially toxic, these drugs should not be used without proven effectiveness. For these reasons, a systematic review of randomized controlled trials of systemically administered local-anaesthetic-type drugs in chronic pain was performed. Main outcomes were pain relief or pain intensity difference and adverse effects. Twenty-one reports were found, and four publications were excluded. In the remaining 17 studies (450 patients), 10 used intravenous lignocaine, two used intranasal lignocaine, four used oral mexiletine and one used oral tocainide. The best documented effective dose of intravenous lignocaine was 5 mg/kg, and when infused over 30 min it was well tolerated. Intravenous lignocaine was effective in all four studies in non-cancer-related neuropathic pain. In migraine, lignocaine produced an inconsistent effect. Lignocaine was without effect in all three studies in cancer-related pain. Oral mexiletine showed some efficacy in all three studies in pain due to peripheral nerve damage, but lacked effect in the only study in central pain. Only minor dose-related adverse effects were reported in the 85 patients given mexiletine 225-750 mg. Local-anaesthetic-type drugs are effective in pain due to nerve damage, but there is little or no evidence to support their use in cancer-related pain. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.

The information transmitted by ensembles of primary spindle afferents is diminished when ketamine is used as a pre-anaesthetic

The effect of pre-anaesthetic ketamine on ensemble coding of different stimuli consisting of muscle stretches of various amplitudes was studied for ensembles of simultaneously recorded primary muscle spindle afferents (MSAs). The experiments were conducted on 8 alpha-chloralose anaesthetised cats. Three of the cats received a pre-anaesthetic dose of ketamine (25 mg/kg) injected subcutaneously (ketamine group), while the remaining five animals did not (non-ketamine group). Data for ensemble coding were collected both before and after cutting the ventral root. A method based on principal component analysis and algorithms was used to quantify stimulus discrimination and an ANOVA tested differences between groups as well as differences due to ventral root cutting. When the fusimotor supply was intact, a general trend of an increase in the ability to discriminate stimuli with increasing ensemble size was observed for both groups, however, this trend was significantly greater for the non-ketamine group as compared to the ketamine group. When the ventral root was cut, the discrimination pattern for the non-ketamine group decreased significantly (as compared to before ventral root cutting), however, no change occurred for the ketamine group. Consequently, no difference in discrimination pattern was detected between groups after ventral root cutting. The reduction in information transmitted by ensembles of primary MSAs when ketamine is used as a pre-anaesthetic may suggest that ketamine elicits an adverse affect on the fusimotor system.

Dermal IgG deposits and increase of mast cells in patients with fibromyalgia--relevant findings or epiphenomena?

Skin biopsies from 25 patients with fibromyalgia, 5 healthy controls, 8 patients with rheumatoid arthritis, and 9 patients with local chronic pain after whiplash injury, were examined for the occurrence of IgG deposits and collagen types, using direct and indirect immunofluorescence, and for dermal connective tissue mast cells, using semithin Epon sections. Fibromyalgia skin biopsies had significantly higher values of IgG deposits in the dermis and vessel walls and showed a higher reactivity for collagen III. They also had a higher mean number of mast cells. There was a correlation between the percentage of damaged/degranulated mast cells and the individual IgG immunofluorescence scores. These findings support the hypothesis of neurogenic inflammation involvement in fibromyalgia.

Temporal summation in muscles and referred pain areas: an experimental human study

The aim of the present study was to assess temporal summation within saline-induced, localized and referred muscle pain areas. The sensibility to single and repeated electrical stimuli were assessed in the muscle by means of needle electrodes and in the referred pain area by surface stimulation. The study demonstrates that temporal summation of nociceptive input from muscles exists and that the responses to single and repeated nociceptive stimuli of the referred pain area are facilitated.