Articles: hyperalgesia.
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Review
Opioids, pain, the brain, and hyperkatifeia: a framework for the rational use of opioids for pain.
Opioids have relieved more human suffering than any other medication, but their use is still fraught with significant concerns of misuse, abuse, and addiction. This theoretical article explores the hypothesis that opioid misuse in the context of pain management produces a hypersensitivity to emotional distress, termed hyperkatifeia. ⋯ Repeated engagement of opponent processes without time for the brain's emotional systems to reestablish homeostasis will further drive changes in emotional processes that may produce opioid abuse or addiction, particularly in individuals with genetic or environmental vulnerability.
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The use of opioids for the treatment of chronic pain has increased dramatically over the past decade. Whether these drugs provide considerable benefits in terms of pain reduction and improved function to balance the risks associated with their use, however, is unclear. Of particular importance to clinicians treating chronic musculoskeletal pain is opioid-induced hyperalgesia, the activation of pronociceptive pathways by exogenous opioids that results in central sensitization to pain. ⋯ Opioids also have powerful positive effects on the reward and reinforcing circuits of the brain that might lead to continued drug use, even if there is no abuse or misuse. The societal risk of increased opioid prescription is associated with increased nonmedical use, serious adverse events and death. Patients with chronic musculoskeletal pain should avoid the long-term use of opioids unless the benefits are determined to outweigh risks, in which case, the use of chronic opioids should be regularly re-evaluated.
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Neuropathic pain syndromes are characterised by the occurrence of spontaneous ongoing and stimulus-induced pain. Stimulus-induced pain (hyperalgesia and allodynia) may result from sensitisation processes in the peripheral (primary hyperalgesia) or central (secondary hyperalgesia) nervous system. The underlying pathophysiological mechanisms at the nociceptor itself and at spinal synapses have become better understood. ⋯ These mechanisms include reorganisation of cortical somatotopic maps in sensory or motor areas (highly relevant for phantom limb pain and CRPS), increased activity in primary nociceptive areas, recruitment of new cortical areas usually not activated by nociceptive stimuli and aberrant activity in brain areas normally involved in descending inhibitory pain networks. Moreover, there is evidence from PET studies for changes of excitatory and inhibitory transmitter systems. Finally, advanced methods of structural brain imaging (voxel-based morphometry, VBM) show significant structural changes suggesting that chronic pain syndromes may be associated with neurodegeneration.
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Opioids are invaluable in the treatment of moderate-to-severe pain. Unfortunately, their prolonged use may be associated with the onset of opioid-induced hyperalgesia (OIH). This review focuses on recent clinical studies that support or refute the existence of OIH in patients. ⋯ Improvements in paradoxical pain intensity upon discontinuation of opioid therapy suggests that a multidisciplinary method of pain relief is favoured for chronic-pain patients. Quantitative-sensory testing of pain is offered as the most appropriate way of diagnosing hyperalgesia. We can, thus far only reliably validate the existence of OIH development in normal human volunteers receiving acute-morphine infusions.
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Curr Pain Headache Rep · Dec 2009
ReviewMechanisms by which sleep disturbance contributes to osteoarthritis pain: a conceptual model.
Sleep disturbance is prevalent in aging and painful rheumatologic populations, but it has largely been a neglected dimension of the routine clinical care of arthritis patients. Pain associated with osteoarthritis (OA) is a leading cause of disability worldwide, and factors that contribute to pain in OA are poorly understood. Sleep disturbance is not only a consequence of pain, it is also likely to play an integral role in pain expression. ⋯ This article reviews the extant literature on sleep disturbance and hyperalgesia in patients with OA. We propose a conceptual working model describing pathways by which sleep disturbance interacts directly with central pain processing mechanisms and inflammatory processes, and indirectly with mood and physical functioning to augment clinical OA pain. The clinical and research implications of the model are discussed.