Pain
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The objective of the present research was to develop a single measure of the major symptoms of both neuropathic and non-neuropathic pain that can be used in studies of epidemiology, natural history, pathophysiologic mechanisms, and treatment response. We expanded and revised the Short-form McGill Pain Questionnaire (SF-MPQ) pain descriptors by adding symptoms relevant to neuropathic pain and by modifying the response format to a 0-10 numerical rating scale to provide increased responsiveness in longitudinal studies and clinical trials. ⋯ The data suggest that the SF-MPQ-2 has excellent reliability and validity, and the results of both exploratory and confirmatory factor analyses provided support for four readily interpretable subscales-continuous pain, intermittent pain, predominantly neuropathic pain, and affective descriptors. These results provide a basis for use of the SF-MPQ-2 in future clinical research, including clinical trials of treatments for neuropathic and non-neuropathic pain conditions.
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Clinical Trial
Similar itch and nociceptive sensations evoked by punctate cutaneous application of capsaicin, histamine and cowhage.
Itch evoked by cowhage or histamine is reduced or blocked by capsaicin desensitization, suggesting that pruriceptive neurons are capsaicin-sensitive. Topical capsaicin can evoke both nociceptive sensations and itch, whereas intradermal injection of capsaicin evokes only burning pain. To dissociate the pruritic and nociceptive sensory effects caused by the chemical activation of sensory neurons, chemicals were applied in a punctiform manner to the skin of the forearm using individual, heat-inactivated cowhage spicules treated with various concentrations of capsaicin (1-200 mg/ml) or histamine (0.01-100 mg/ml). ⋯ Each type of spicule also produced comparable areas of dysesthesias (enhanced mechanically evoked itch or pain) and/or skin reactions (wheal and/or flare) in surrounding skin, though inconsistently. The incidence of flare was greater in response to histamine than to capsaicin or cowhage. These results suggest the possibility that capsaicin, histamine and cowhage activate common peripheral or central neural mechanisms that mediate pruritic sensations and associated dysesthesias.
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We used a large medical insurance claims database to identify three groups: chronic opioid use (>180 therapeutic days, N=3726); acute opioid use (<10 therapeutic days, N=37,108); and a non-opioid group (N=337,366) who filed at least one insurance claim but none for opioids. Our results showed that although chronic opioid users represented only 0.65% of the total population, they filed 4.56% of all insurance claims, used 45% of all opioid analgesics and had much more physical and psychiatric co-morbidity than the acute opioid or non-opioid samples. ⋯ Moreover, our data suggest that opioids were often used for conditions in which they are generally not indicated (e.g. arthritis and headaches) or contraindicated by co-existing physical ailments (COPD). Finally, we conclude that adherence to the WHO analgesic ladder and other pain treatment guidelines was relatively infrequent: first, opioid extended release preparations which are ideally suited for chronic pain were used only in one in four patients; and, second, the selection of a weak (propoxyphene, codeine, and tramadol) or strong opioid (e.g. morphine and oxycodone) seemed to be driven by numerous factors not necessarily related to the intensity or duration of pain.
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Fentanyl is an opioid with high lipid solubility, suitable for intravenous, spinal, transmucosal and transdermal administration. The transdermal fentanyl patch has become widely used in the treatment of both malignant and non-malignant chronic pain. The absorption of fentanyl from the patch is governed by the surface area of the patch, by skin permeability and by local blood flow. ⋯ Plasma fentanyl concentrations adjusted to dose were significantly lower at 48 and 72 h in cachectic patients than normal weight patients. The cachectic patients had a significantly thinner upper arm skin fold, but no differences were found in local blood flow, sweating, or skin temperature. Absorption of transdermal fentanyl is impaired in cachectic patients compared with that of normal weight cancer pain patients.