Pain
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Randomized Controlled Trial Clinical Trial
Transdermal clonidine compared to placebo in painful diabetic neuropathy using a two-stage 'enriched enrollment' design.
Because a variety of mechanisms may generate pain in neuropathic pain syndromes, conventional clinical trial methods may fail to identify some potentially useful drugs; a drug affecting just a single mechanism may work in too few patients to yield a statistically significant result for the trial. To test a previous clinical observation that approximately one-quarter of patients with painful diabetic neuropathy appear responsive to clonidine, we conducted a formal clinical trial of transdermal clonidine in painful diabetic neuropathy patients using a 2-stage enriched enrollment design. In the first stage (study 1), 41 patients with painful diabetic neuropathy completed a randomized, 3-period crossover comparison of transdermal clonidine (titrated from 0.1 to 0.3 mg/day) to placebo patches. ⋯ In study II, however, the 12 apparent responders from study I had 20% less pain with clonidine than placebo (95% confidence interval (CI): 4-35% pain reduction; P = 0.015), confirming that their pain was responsive to clonidine. None of the 3 consistent clonidine responders who were tested with the alpha-adrenergic blocker phentolamine had relief of pain, suggesting that clonidine's pain relief is not mediated by a decrease in sympathetic outflow. A post-hoc analysis of many variables suggested that patients who described their pain as sharp and shooting may have a greater likelihood of responding to clonidine.(ABSTRACT TRUNCATED AT 250 WORDS)
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Rats in which the sciatic nerve is partially transected develop hyperalgesia which is relieved by sympathectomy. We carried out experiments using this model of experimental peripheral neuropathy to examine the peripheral mechanisms underlying sympathetically maintained pain. Subcutaneous injection of noradrenaline (NA) into the affected paw exacerbated the hyperalgesia but had no effect in control animals. ⋯ Following a chemical sympathectomy, hyperalgesia was eliminated and injection of NA into the hyperalgesic paw had no effect on pain thresholds. We concluded that NA exacerbates hyperalgesia in this experimental model by acting on alpha 2-adrenoreceptors which are located on post-ganglionic sympathetic terminals. Our results are consistent with the proposal (Levine et al. 1986) that activation of these adrenoreceptors brings about an increased release of prostaglandins which sensitises nociceptors.
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In this study, changes in plasma levels of calcitonin gene-related peptide (CGRP) and substance P (SP) during a spontaneous-like cluster headache attack provoked by nitroglycerin were evaluated. Peptide variations after spontaneous or sumatriptan-induced remission were also assessed. Blood was collected from the external jugular vein homolateral to the pain side of 30 male cluster headache patients; 18 men were in an active and 12 in a remission one. ⋯ On the contrary, nitroglycerin neither provoked a cluster headache attack nor altered CGRP-LI in the patients in a remission period. The augmented levels of CGRP-LI measured before and after nitroglycerin administration, when the provoked attack reached the maximum intensity, suggest an activation of the trigeminovascular system during the active period of cluster headache. Moreover, the clinical and biochemical actions showed by sumatriptan stress the involvement of serotonin in cluster headache mechanisms.
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Extending the earlier work of Mikail et al. (1993), a confirmatory factor analysis (CFA; LISREL VII) of a 4-factor model of pain assessment was tested. This model, comprised of the Beck Depression Inventory (BDI) and 13 subscales of the McGill Pain Questionnaire (MPQ) and the West Haven-Yale Multidimensional Pain Inventory (WHYMPI), adequately accounted for the pain experience with minimal overlap. Subjects were 306 outpatient chronic pain patients seen at a multidisciplinary chronic pain clinic. ⋯ The 4 factors were identified as Affective Distress, Support, Pain Description, and Functional Capacity. Results supported the hypothesis that the MPQ, WHYMPI and BDI are representative of the multidimensionality of the pain experience with minimal overlap among measures. Theoretical and clinical implications of reducing the overlap among existing measures in the assessment of pain patients are discussed.
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This paper describes the development and validation of a measure of strategies used by patients to cope with chronic pain, the Chronic Pain Coping Inventory (CPCI). A 104-item measure of pain coping responses and 3 measures of functioning were completed by 176 chronic pain patients. Two-week retest data were provided by 111 of these patients. ⋯ The results support the reliability of the CPCI scales. Four scales (Guarding, Resting, Asking for Assistance, and Task Persistence) predicted patient- and significant other-reported patient adjustment. Eight scales (Guarding, Opioid Medication Use, NSAID Use, Sedative-Hypnotic Medication Use, Resting, Asking for Assistance, and Exercise/Stretch) demonstrated moderate-to-strong relationships between patient and significant-other versions, further supporting their validity.