Pain
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Case Reports
Topical application of clonidine relieves hyperalgesia in patients with sympathetically maintained pain.
Patients with reflex sympathetic dystrophy or causalgia characteristically have ongoing pain and pain to light touch (hyperalgesia). Some of these patients obtain relief of their pain following interruption of sympathetic function to the affected area and, therefore, have sympathetically maintained pain (SMP). Evidence suggests that the pain and hyperalgesia in SMP are related to activation of peripheral adrenergic receptors. ⋯ In two SMP patients, intradermal injection of norepinephrine or phenylephrine (a specific alpha 1-adrenergic agonist) at a site treated with clonidine evoked intense pain and rekindled the pre-clonidine hyperalgesia at that site. It is likely that clonidine locally blocks the release of norepinephrine via activation of alpha 2 receptors on the sympathetic terminals. This study suggests, therefore, that SMP is mediated via alpha 1-adrenergic receptors located in the affected tissue.
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Clinical Trial Controlled Clinical Trial
Early and late effects of prolonged topical capsaicin on cutaneous sensibility and neurogenic vasodilatation in humans.
Cutaneous sensibility and neurogenic vasodilatation (flare) were measured before, during and after long-term topical application of capsaicin in humans. Each subject applied a vehicle cream containing 0.075% capsaicin (Axsain, GalenPharma Inc.) to a 4 cm2 area of skin on one volar forearm and vehicle alone to an identical treatment area on the other forearm, according to a double-blind procedure. Each substance was applied 4 times/day for 6 weeks. ⋯ These studies demonstrate that prolonged application of capsaicin at low concentration selectively diminishes sensations of heat pain and neurogenic vasodilatation, presumably via desensitization of heat-sensitive nociceptors. It is also shown that the decrease in heat pain is temporary and is maintained with repeated capsaicin application. There appears to be a therapeutic role for capsaicin in cutaneous painful syndromes mediated, at least in part, by activity of heat-sensitive nociceptors.
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We report the case of a patient who developed myoclonus and hyperalgesia following administration of high-dose subarachnoid morphine. This complication occurred with 40-80 mg/day continuous infusion. The pathophysiology of these side effects is discussed.
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A growing number of investigators have used models of stress and coping to help explain the differences in adjustment found among persons who experience chronic pain. This article reviews the empirical research which has examined the relationships among beliefs, coping, and adjustment to chronic pain. Although preliminary, some consistent findings are beginning to emerge. ⋯ Although coping strategies appear to be associated with adjustment in chronic pain patients, methodological problems limit conclusions regarding the strength and nature of this association. Our recommendations for future research include the development of coping and belief measures which: (1) do not confound different dimensions (e.g., coping, beliefs, and adjustment) in the same measure; (2) assess specific (rather than composite) constructs; (3) are psychometrically sound; and (4) assess behavioral coping strategies more objectively. We also recommend a greater use of experimental research designs to examine causal relationships among appraisals, coping, and adjustment.