Pain
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Randomized Controlled Trial Comparative Study Clinical Trial
The hypoalgesic effect of imipramine in different human experimental pain models.
In a randomized, placebo-controlled, double-blind, cross-over study, the hypoalgesic effect of a single oral dose of 100 mg imipramine was investigated in 12 healthy volunteers. Test procedures performed before, 3, 6, and 9 h after medication included determination of (1) pain detection and tolerance thresholds to heat and pressure; (2) the thresholds of quadriceps femoris muscle withdrawal reflex to single and repeated electric stimulation of the sural nerve; (3) amplitude of the reflex evoked by 1.5 times the premedication reflex threshold; and (4) continuous pain rating during the cold pressor test. Imipramine significantly increased pain tolerance thresholds to heat (P = 0.03) and pressure (P = 0.01), and both the psychophysical pain tolerance threshold and the reflex threshold to single electric stimulation (P = 0.02 and P = 0.03, respectively). ⋯ Pain detection thresholds to heat and pressure, the amplitude of the reflex to single suprathreshold stimulation, and pain ratings during the cold pressor test were unaltered by imipramine. It is concluded that imipramine has a differential hypoalgesic effect on different human experimental pain tests. This provides new possibilities of assessing the differential effect of different tricyclic antidepressants on different pain modalities and intensities.
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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.
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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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A patient suffered multiple fractures of the right leg and a left brain-stem infarction involving the anterolateral fasciculus of the central nociceptive system following multiple trauma. Later, the right leg was amputated, resulting in spontaneous and touch-evoked phantom pain and mechanical stump allodynia. However, quantitative sensory testing revealed considerable impairment of sensations normally mediated by cutaneous nociceptors and central spinothalamic systems on the right body side, including the stump but nearly intact touch and vibration senses. ⋯ We concluded the following. (i) Painful somatosensory memories that are responsible for phantom limb pain are located in the brain, most probably in the thalamus or cortex. (ii) Touch-evoked phantom pain and stump allodynia are not mediated by cutaneous nociceptive C and A delta fibers and spinal nociceptive pathways (spinothalamic tract). Activity in the lemniscal system (low-threshold mechanoreceptive A beta afferents, dorsal columns and medial lemnicus system) may be transferred to central pain signaling neurons in the thalamus or cortex resulting in touch-evoked pain sensations. (iii) Ongoing activity in cutaneous nociceptive C fibers and spinal nociceptive systems is not necessary to maintain central processes that account for spontaneous and touch-evoked pain sensations. Activity in nociceptors of deep somatic tissues might be more important.
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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.