Pain
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This study compared individuals with fibromyalgia (FM) and individuals with chronic low back pain (CLBP) on repetition-induced summation of activity-related pain (RISP). Fear of movement, pain catastrophizing and depression were examined as potential mediators of group differences. The sample consisted of 50 women with FM and 50 women with CLBP who were matched on age, pain severity and pain duration. ⋯ Discussion addresses the processes by which individuals with FM might have increased RISP responses. The findings of this study point to possible neurophysiological mechanisms that could help explain the high levels of pain-related disability seen in individuals with FM. Patients with fibromyalgia showed greater activity-related summation of pain than patients with chronic low back pain.
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Randomized Controlled Trial Clinical Trial
On the importance of placebo timing in rTMS studies for pain relief.
The efficacy of repetitive transcranial magnetic stimulation (rTMS) of the motor cortex for neuropathic pain relief is founded on double-blind studies versus placebo. In these studies, however, the analgesic effect of active interventions remained modest compared with the placebo effect. This observation led us to re-evaluate the intrinsic placebo action on pain relief according to the relative timing of active and sham rTMS interventions. ⋯ The fact that placebo effects could be enhanced by a previous rTMS with an analgesic effect as low as 10% suggests that a 30% pain decrease threshold in therapeutic trials may be too severe because smaller analgesic effects may have a clinical significance too. Sham rTMS induces significant analgesia only when preceded by a successful active stimulation. Such a placebo modulation is probably related to an unconscious conditioned learning.
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Randomized Controlled Trial
Tropisetron blocks analgesic action of acetaminophen: a human pain model study.
Because the mechanism underlying the analgesic action of acetaminophen remains unclear, we investigated the possible interaction of acetaminophen with central serotonergic pathways. The effects of acetaminophen, tropisetron, the combination of both drugs, and saline on pain perception and central sensitization in healthy volunteers were compared. Sixteen healthy volunteers were included in this randomized, double-blind, placebo-controlled crossover study. ⋯ In summary, while the combination of acetaminophen and tropisetron showed no analgesic action, each drug administered alone led to decreased pain ratings as compared to saline. In an electrically evoked human pain model, the combination of acetaminophen with tropisetron was free of any analgesic potential. However, when administered on its own, both acetaminophen and tropisetron were mildly analgesic.
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Randomized Controlled Trial
Effects of COX inhibition on experimental pain and hyperalgesia during and after remifentanil infusion in humans.
Opioids may enhance pain sensitivity resulting in opioid-induced hyperalgesia (OIH). Activation of spinal cyclooxygenase may play a role in the development of OIH. The aim of this study was to demonstrate remifentanil-induced postinfusion hyperalgesia in an electrical pain and a cold pain model, and to investigate whether COX-2 (parecoxib) or COX-1 (ketorolac) inhibition could prevent hyperalgesia after remifentanil infusion. ⋯ These results demonstrated OIH in both models, and may suggest that COX-2 inhibition is more important than COX-1 inhibition in reducing hyperalgesia. Remifentanil-induced hyperalgesia was demonstrated for both electrically induced pain and cold-pressor pain. Both parecoxib and ketorolac prevented hyperalgesia in the electrical model, parecoxib to a larger extent.