The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Enlarged Areas of Pain and Pressure Hypersensitivityby Spatially Distributed Intramuscular Injections ofLow-Dose Nerve Growth Factor.
Intramuscular injection of nerve growth factor (NGF) causes muscle hyperalgesia without immediate pain. This double-blinded, randomized study assessed pain and muscle hypersensitivity after a single-site bolus NGF injection (5 µg) compared with 5 spatially distributed, low-dose NGF injections (1 µg, 4 cm distance) into the tibialis anterior (TA) muscles in 20 healthy subjects. Injection pain was rated on a visual analog scale. ⋯ Perspective: Spatially distributed low-dose NGF injections induced prolonged pain, mechanical muscle hypersensitivity, and enlarged contraction-evoked pain areas. These features mirror some clinical muscle pain conditions in which diffuse pain areas and muscle hypersensitivity are present during the activities of daily living. Low-dose NGF injections may be useful for further studies of prolonged pain conditions.
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Recent research has revealed robust cross-sectional and prospective associations among perceived injustice, pain, disability, and depressive symptoms in patients with chronic pain. To date, research has proceeded from the assumption that perceived injustice arises as a consequence of debilitating injury or illness. However, it is possible that perceived injustice might have trait-like characteristics, persisting even in the absence of an injustice-related eliciting event. ⋯ The results of the present study suggest that individuals vary in their trait-like propensity to experience negative life events as unjust and that trait perceived injustice contributes to adverse pain outcomes. PERSPECTIVE: The present findings suggest that perceived injustice might reflect an enduring tendency to experience negative life events as unjust. The findings also suggest that trait perceived injustice is associated with higher ratings of pain intensity and anger and more pronounced displays of pain behavior.
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Paclitaxel induces microglial activation and production of proinflammatory mediators in the dorsal horn, which contribute to the development and maintenance of central sensitization and pain behavior. MDA7, 1-([3-benzyl-3-methyl-2,3-dihydro-1-benzofuran-6-yl]carbonyl) piperidine, is a novel highly selective cannabinoid type 2 (CB2) agonist. We tested the hypothesis that activation of CB2 receptor by MDA7 modulates microglial dysregulation, suppresses the overexpression of brain-derived neurotrophic factor (BDNF) in microglia in the dorsal horn, and attenuates the central sensitization and pain behavior induced by paclitaxel. ⋯ Perspective: This study provides evidence that paclitaxel induced microglia dysregulation and epigenetically upregulated the microglial expression of BDNF, which led to sensitization of dorsal horn neurons and mechanical allodynia in rats. The CB2 agonist MDA7 alleviated these pathological processes. MDA7 represents an innovative therapeutic approach for treatment of chemotherapy-induced neuropathy.
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Review Meta Analysis
The blind leading the not so blind: a meta-analysis of blinding in pharmacological trials for chronic pain.
Patient blinding is a critical feature of double-blind placebo-controlled randomized controlled trials (RCTs). Yet, very little is known about practices for assessing and reporting blinding in chronic pain trials. We examined the rates and predictors of assessing blinding and its success in pharmacological RCTs for chronic pain. ⋯ The results indicated that blinding is rarely assessed and often fails. Some study characteristics were associated with lower rates of assessing blinding and its success, for example, pharmaceutical sponsorship and side effects. Implications and recommendations for chronic pain RCTs are discussed.
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Recent temporal trends in the population prevalence of chronic pain in Canada on a national and provincial level are unknown. Five cycles of the Canadian Community Health Survey (2000/2001, 2007/2008, 2009/2010, 2011/2012, and 2013/2014) were used to derive population-based estimates of the self-reported prevalence of chronic pain. Sensitivity analyses examined chronic pain prevalence among those reporting no other chronic health conditions. ⋯ Increasing chronic pain prevalence in Canada, most significantly occurring between 2010 and 2012, and including among healthy and young individuals, emphasizes the need for targeted research and resources to help alleviate chronic pain. PERSPECTIVE: This study uncovers a significant increase in chronic pain prevalence in Canada between 2009/2010 and 2011/2012, driven by younger Canadians that are free of the most common chronic health conditions. This discovery emphasizes the importance of further directed research and resources to help mitigate the trend of increasing chronic pain.