Pain
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The evidence on the patterns of nonsteroidal anti-inflammatory drug (NSAID) use according to pain prevalence and clinical guidelines in older people is sparse. This cross-sectional study examined the patterns of NSAID use according to pain prevalence and concordance with clinical guideline recommendations for safe NSAID use in older people, in relation to duration of use, patterns of use, concomitant use of proton pump inhibitors (PPIs), and prevalence of specific drug interactions. Community-dwelling men (n=1696) age ≥ 70 years living in Sydney were studied. 8.2% (n=139) of participants reported regular NSAID use compared with 2.9% (n=50) reporting as-needed use. ⋯ In relation to pain prevalence, regular NSAID users were significantly more likely to report chronic pain (P<.0001), recent pain (P=.0001), and chronic intrusive pain (P<.0001) compared with nonregular users. The findings of this study indicate that NSAID prescribing practices do not align with clinical guidelines for safe use in older people. This difference between the guideline recommendations and what is happening in the real world should be explored further.
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Candidate gene studies have revealed limited genetic bases for opioid analgesic response variability. Genome-wide association studies facilitate impartial queries of common genetic variants, allowing identification of novel genetic contributions to drug effect. Illumina (Illumina Inc, San Diego, CA, USA) single nucleotide polymorphism (SNP) arrays were used to investigate SNP associations with total morphine requirement as a quantitative trait locus and with postoperative pain in a retrospective population of opioid-naïve children ages 4-18years who had undergone day surgery tonsillectomy and adenoidectomy. ⋯ No association with morphine dose was detected in African Americans (AA) (n=241). Postoperative pain scores ≥ 7/10 were associated with rs795484 (G>A) in the EC cohort (odds ratio 2.35, 95% CI 1.56-3.52, P<0.00005) and this association replicated in AA children (odds ratio 1.76, 95% CI 1.14-2.71, P<0.01). Variants in TAOK3 encoding the serine/threonine-protein kinase, TAO3, are associated with increased morphine requirement in children of EC ancestry and with increased acute postoperative pain in both EC and AA subjects.
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Biological differences in sensory processing between human and model organisms may present significant obstacles to translational approaches in treating chronic pain. To better understand the physiology of human sensory neurons, we performed whole-cell patch-clamp recordings from 141 human dorsal root ganglion (hDRG) neurons from 5 young adult donors without chronic pain. Nearly all small-diameter hDRG neurons (<50 μm) displayed an inflection on the descending slope of the action potential, a defining feature of rodent nociceptive neurons. ⋯ Compared to electrically evoked action potentials, chemically induced action potentials were triggered from less depolarized thresholds and showed distinct afterhyperpolarization kinetics. These data indicate that most small/medium hDRG neurons can be classified as nociceptors, that they respond directly to compounds that produce pain and itch, and that they can be activated and sensitized by inflammatory mediators. The use of hDRG neurons as preclinical vehicles for target validation is discussed.
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Cervical facet joint injury induces persistent pain and central sensitization. Preventing the peripheral neuronal signals that initiate sensitization attenuates neuropathic pain. Yet, there is no clear relationship among facet joint afferent activity, development of central sensitization, and pain, which may be hindering effective treatments for this pain syndrome. ⋯ Silencing afferent activity during the development of neuronal hyperexcitability (4 hours, 8 hours, 1 day) attenuated hyperalgesia and neuronal hyperexcitability (P<.045) only for the treatment given 4 hours after injury. This study suggests that early afferent activity from the injured facet induces development of spinal sensitization via spinal excitatory glutamatergic signaling. Peripheral intervention blocking afferent activity is effective only over a short period of time early after injury and before spinal modifications develop, and is independent of modulating spinal glial activation.
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The effective management of pain is a longstanding public health concern. Morphine-like opioids have long been front-line analgesics, but produce undesirable side effects that can limit their application. Slow progress in the introduction of novel improved medications for pain management over the last 5 decades has prompted a call for innovative translational research, including new preclinical assays. ⋯ Next, sessions were conducted in which the temperature of the thermode was increased stepwise until responding stopped, permitting the determination of stable nociceptive thresholds. Tests revealed that several opioid analgesics, but not d-amphetamine or Δ(9)-THC, produced dose-related increases in threshold that were antagonist sensitive and efficacy dependent, consistent with their effects using traditional measures of antinociception. Unlike traditional reflex-based measures, however, the results also permitted the concurrent evaluation of response disruption, providing an index with which to characterize the behavioral selectivity of antinociceptive drugs.