The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Assessing the influence of non-ischaemic A-fiber conduction blockade on offset analgesia: an experimental study.
Offset analgesia (OA) is believed to reflect the efficiency of the endogenous pain modulatory system. However, the underlying mechanisms are still being debated. Previous research suggested both, central and peripheral mechanisms, with the latter involving the influence of specific A-delta-fibers. ⋯ However, further studies are needed to substantiate a central rather than peripheral influence on OA. PERSPECTIVE: This article presents the observation of OA before, during, and after a successful A-fiber conduction blockade in healthy volunteers. A better understanding of the mechanisms of OA and endogenous pain modulation, in general, may help to explain the underlying aspects of pain disorders.
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Depression commonly co-occurs with chronic pain and can worsen pain outcomes. Recent theoretical work has hypothesized that pain localized to the left hemibody is a risk factor for worse depression due to overlap in underlying neural substrates. This hypothesis has not been tested a priori. ⋯ Although a more rigorous assessment of pain laterality is needed, our findings do not support the hypothesis that left-lateralized pain is associated with worse depression. PERSPECTIVE: Pain lateralized to the left side of the body has been hypothesized as a risk factor for worse depression in chronic pain, despite never being tested in a large, real-world sample of patients with chronic pain. Findings showed that more widespread pain, not pain laterality, was associated with worse depression.
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Several person variables predate injury or pain onset that increase the probability of maladjustment to pain and opioid misuse. The aim of this study was to evaluate the role of 2 diathesis variables (impulsiveness and anxiety sensitivity [AS]) in the adjustment of individuals with chronic noncancer pain and opioid misuse. The sample comprised 187 individuals with chronic noncancer pain. ⋯ The findings support the hypothesis that both impulsiveness and AS are vulnerability factors for maladaptive adjustment to chronic pain and opioid misuse. PERSPECTIVE: This article adds to the empirical literature by including AS and impulsiveness as antecedent variables in a model of dual vulnerability to chronic pain maladjustment and opioid misuse. The findings suggest the potential utility of assessing both factors in individuals in the first stages of chronic pain.
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Comparative Study
Comparison of Morphine and Endomorphin Analog ZH853 for Tolerance and Immunomodulation in a Rat Model of Neuropathic Pain.
µ-Opioid receptor agonists, the gold standard for analgesia, come with significant side effects when used chronically. Tolerance, defined as the decrease in analgesic activity after repeated use, remains a vital therapeutic obstacle as it increases the likelihood of dose escalation and potentially lethal side effects like respiratory depression. Previous experiments have shown that the endomorphin-1 analog, ZH853, is a specific µ-opioid receptor agonist with reduced side effects like tolerance and glial activation following chronic central administration in pain-naive animals. ⋯ This study demonstrates the effectiveness of chronic ZH853 for providing analgesia in a neuropathic pain state with reduced tolerance compared with morphine, potentially due to reductions in spinal glial activation. PERSPECTIVE: Neuropathic pain is generally undertreated and resistant to medication, and side-effects limit opioid treatment. Here, we show that, compared with an equiantinociceptive dose of morphine, chronic intravenous administration of endomorphin analog ZH853 led to prolonged antiallodynia, reduced tolerance, and inhibition of spinal cord neuroinflammation in male spared nerve-injured rats.
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Randomized Controlled Trial
Temporal Summation but not Expectations of Pain Relief Predict Response to Acupuncture Treatment in Fibromyalgia.
Fibromyalgia (FM) is a common chronic pain condition for which acupuncture treatment is increasingly utilized. However, there is no universally accepted measure to predict whether a specific patient will benefit from acupuncture. This is a single-center, single-blind, sham-controlled, randomized, noncrossover, longitudinal trial of 76 subjects with FM, assigned to either electroacupuncture (EA) or a placebo control, mock laser (ML) acupuncture. ⋯ Our results support using a quantitative sensory testing metric, temporal summation of pain, but not expectations, to predict analgesia following acupuncture treatment for pain. PERSPECTIVE: A randomized study of acupuncture in FM found baseline temporal summation, but not expectations of pain relief, to be predictive of treatment response. CLINICAL TRIAL REGISTRATION: Registered under ClinicalTrials.gov identifier NCT02064296.