The journal of pain : official journal of the American Pain Society
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Review Comparative Study
Systematic review of the comparative effectiveness of antiepileptic drugs for fibromyalgia.
Fibromyalgia is a difficult-to-treat chronic pain syndrome that affects 2% of the US population. Pregabalin is an antiepileptic recently FDA approved for fibromyalgia treatment. Other antiepileptics have been suggested for treatment. This systematic review examines the relative benefits and harms of antiepileptic drugs in the treatment of fibromyalgia. A literature search was conducted and 8 studies matched criteria (7 studies of pregabalin, 1 of gabapentin). Both drugs reduced mean pain scores more than placebo at a modest rate (pregabalin, 38% to 50%; gabapentin, 51%). In a 6-month trial of pregabalin responders, 32% continued to have response at 6 months, with a mean time to loss of response of 34 days. Compared to placebo, the drugs had similarly high rates of adverse events and withdrawals. Without a head-to-head trial it is not possible to conclude if 1 antiepileptic is more effective or harmful than the other, although limited evidence suggests potential differences. Future studies must directly compare the drugs, include a more broadly defined population, examine long term benefits and harms, and include cointerventions. We conclude that pregabalin and gabapentin are modestly effective for the treatment of fibromyalgia but that their long-term safety and efficacy remain unknown. ⋯ This systematic review evaluates the benefits and harms of using the antiepileptic drugs gabapentin and pregabalin for the treatment of fibromyalgia. Conclusions from this paper can help clinicians to more effectively treat the pain associated with fibromyalgia.
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A large proportion of oncology outpatients with bone metastasis report unrelieved pain that significantly interferes with daily functioning and quality of life. However, little is known about the longitudinal pattern of pain intensity and analgesic prescriptions or use. Moreover, despite considerable advantages, the use of sophisticated statistical techniques, such as hierarchical linear modeling (HLM) has not been applied to the study of pain and analgesic outcomes. In a prospective longitudinal study, HLM was used to explore predictors of pain intensity and analgesic prescription and intake at the time of enrollment into the study (intercept) and over the course of 6 weeks (trajectory) in a sample of oncology outpatients with bone metastasis who received standard care for pain. In addition to corroborating known predictors of pain intensity, previously unrecognized variables were found that appear to affect both pain and analgesic outcomes. Importantly, some of the predictors of the trajectories of pain intensity and analgesic use (ie, pain-related distress and Pain Management Index (PMI) scores) are particularly amenable to interventions. Findings from this study suggest that sophisticated statistical modeling can be used in pain research to identify individual risk factors and propose novel targets that can be used to improve pain management in oncology outpatients with bone metastasis. ⋯ Findings from this study suggest that a large amount of inter-individual variability exists in patients' experiences with cancer pain and analgesic use. Future studies need to elucidate the mechanisms that underlie these differences.
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To investigate the pain-modulatory effects of a local inflammatory stimulus on pain elsewhere in the body, capsaicin was applied topically to the forearm of 14 healthy female volunteers. Pressure-pain thresholds and sensitivity to sharpness were assessed on each side of the forehead twice per day during 48 hours of capsaicin treatment, and in the treated and contralateral forearm before and at the end of treatment. Heat was applied to the treated area to rekindle pain at times of forehead assessment. Hyperalgesia to sharpness, but not pressure pain, developed in the treated area whereas sensations remained stable in the contralateral forearm. Sharpness ratings decreased bilaterally in the forehead after 6 hours of treatment, and ipsilateral analgesia to pressure pain developed in the forehead when the capsaicin site was heated after 48 hours of treatment. These findings suggest that pain modulation involves unilateral regulatory mechanisms in addition to local and generalized pain control. The dissociated changes to sharpness and pressure pain indicate distinct cutaneous and deep central pain pathways. ⋯ The findings lend support to an increasing body of research which demonstrates that pain modulation involves hemilateral mechanisms in addition to local and generalized controls. Elucidation of mechanisms that modulate ipsilateral pain processing may help to clarify the pathophysiology of complex regional pain syndrome, which is characterized by hemilateral hyperalgesia.
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Single-word descriptors are commonly used to label and communicate pain in lay as well as clinical settings. Research has shown that the pool of 84 pain descriptors from the McGill Pain Questionnaire (MPQ) can be refined into a parsimonious subset of 36 descriptors that fit into 12 categories. However, the past 3 studies on this issue have been confined to college student samples. The present study investigated the classification structure and calibration of this new system of pain descriptors in 43 chronic pain patients. Employing a 3-point decision rule, a relatively unambiguous classification structure emerged with 3 descriptors for each of the 12 categories. Within and across categories, the intensities implied by these words could be meaningfully rank ordered. The intensities correlated positively and significantly with those previously derived from student samples as well as those of matching MPQ words previously rated by pain patients. This confirms the stability of the intensity ratings of pain words. Information theoretic analysis revealed transmission of 83% of the maximum (3.6 bits) potentially transmissible in a system of such configuration. This lends support to the idea that the 36 pain descriptors are parsimonious and can be used with efficiency to describe chronic pain. ⋯ This study found that in the English language, 36 words (classified into 12 subcategories) can be efficiently used to describe pain. These words can also be reliably ordered in terms of implied pain intensity. This has implications for the qualitative and quantitative assessment of pain patients.
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Fibromyalgia (FM) is a chronic, widespread musculoskeletal pain disorder that is very prevalent in the general population (approximately 5%). Accumulating evidence suggests that FM is associated with central pain processing abnormalities, ie, central sensitization. Several previous studies of chronic pain patients, including FM, have shown gray matter atrophy of brain areas associated with sensory and affective pain processing. These findings, however, have not been confirmed in all FM studies. In this study, we investigated gray matter volumes of brain areas associated with pain-related areas of FM patients identified by functional brain imaging. Using voxel-based morphometric (VBM) analysis of magnetic resonance brain images, we compared 19 pain-related brain areas of 14 female FM patients and 11 healthy controls (NC). We found that FM patients had significantly less gray matter volumes than NC in 3 of these brain regions, including the anterior and mid-cingulate, as well as mid-insular cortices. Importantly, FM patients demonstrated neither global gray matter atrophy nor gray matter changes associated with depression, as shown in some studies. Using a more stringent analysis than other VBM studies, we provide evidence for decreased gray matter volumes in a number of pain-related brain areas in FM. Although the mechanisms for these gray matter changes are presently unclear, they may contribute to some of the core features of this chronic disorder including affective disturbances and chronic widespread pain. ⋯ Increasing evidence supports the association of chronic pain with accelerated gray matter atrophy in pain disorders like low back pain, IBS, and FM syndrome. However, cause-effect relationships between chronic pain and decreased gray matter volumes have not been established yet and will require future prospective studies.