Pain
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Randomized Controlled Trial
Open-label placebo for chronic low back pain: a 5-year follow-up.
Long-term follow-up of patients treated with open-label placebo (OLP) are nonexistent. In this article, we report a 5-year follow-up of a 3-week OLP randomized controlled trial (RCT) in patients with chronic low back pain. We recontacted the participants of original RCT and reassessed their pain, disability, and use of pain medication. ⋯ By contrast, the use of alternative approaches to pain management increased (from 18% to 29%). Although the reduction in pain and medication is comparable with the improvements that occurred in the original study, a major limitation of this long-term follow-up is the absence of controls for spontaneous improvement and new cointerventions. Nonetheless, our data suggest that reductions in pain and disability after OLP may be long lasting.
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It has been proposed that complex regional pain syndrome (CRPS) is a posttraumatic autoimmune disease. Previously, we observed that B cells contribute to CRPS-like changes in a mouse tibia fracture model, and that early (<12 months duration) CRPS patient IgM antibodies have pronociceptive effects in the skin and spinal cord of muMT fracture mice lacking B cells. The current study evaluated the pronociceptive effects of intraplantar or intrathecal injections of early CRPS IgM (5 µg) in muMT fracture mice. ⋯ Intrathecal IgM injection also had pronociceptive effects with increased spinal cytokine expression, effects that were blocked by PMX53 or pentoxifylline treatment. Intrathecal injection of chronic (>12 months duration) CRPS patient IgM (but not IgG) caused nociceptive sensitization in muMT fracture mice, but intraplantar injection of chronic CRPS IgM or IgG had no effect. We postulate that CRPS IgM antibodies bind to neoantigens in the fracture limb skin and corresponding spinal cord to activate C5a complement signaling in macrophages and microglia, evoking proinflammatory cytokine expression contributing to nociceptive sensitization in the injured limb.
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Randomized Controlled Trial
A randomized, controlled trial of a β2-agonist in painful polyneuropathy.
Experimental data have suggested that in neuropathic pain, tricyclic antidepressants may work solely through a β2-agonist action. The aim of this study was to test if the β2-agonist terbutaline relieves painful polyneuropathy. The study was a randomized, double-blind, placebo-controlled and active-controlled, 3-way, cross-over trial among patients with painful polyneuropathy. ⋯ The median score for total pain on imipramine changed from NRS 6.6 to 4.8 with an average effect as compared with placebo of -1.17 (95% confidence interval -1.42 to -0.92, P < 0.001). Secondary outcomes were also unaltered by terbutaline but improved by imipramine. The β2-agonist terbutaline has no effect in painful polyneuropathy. β2-agonism seems not to be an important mechanism of action of tricyclic antidepressants in neuropathic pain.
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Many primary care clinics are resistant to accept new patients taking prescription opioids for chronic pain. It is unclear how much of this practice is specific to individuals who may be perceived to have aberrant opioid use. This study sought to determine whether clinics are more or less willing to accept and prescribe opioids to patients depending on whether their history is more or less suggestive of aberrant opioid use by conducting an audit survey of primary care clinics in 9 states from May to July 2019. ⋯ Clinics responding differently had greater odds (odds ratio = 1.83 confidence interval [1.23-2.76]) of willingness to prescribe when the previous doctor retired than when the doctor had stopped prescribing. These findings suggest that primary care access is limited for patients taking opioids for chronic pain, and differentially further reduced for patients whose histories are suggestive of aberrant use. This denial of care could lead to unintended harms such as worsened pain or conversion to illicit substances.
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Cranial hypersensitivity is a prominent symptom of migraine, exhibited as migraine headache exacerbated with physical activity, and cutaneous facial allodynia and hyperalgesia. The underlying mechanism is believed to be, in part, activation and sensitization of dural-responsive trigeminocervical neurons. Validated preclinical models that exhibit this phenotype have great utility for understanding putative mechanisms and as a tool to screen therapeutics. ⋯ These responses were aborted by olcegepant and LY344864. However, GR205171, which failed in clinical trial for both abortive and preventive treatment of migraine, had no effect. These data support the nitroglycerin model as a valid approach to study cranial hypersensitivity and putative mechanisms involved in migraine and as a screen to dissect potentially efficacious migraine therapeutic targets.