The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial Multicenter Study
The Contribution of Differential Opioid Responsiveness to Identification of Opioid Risk in Chronic Pain Patients.
The Screener and Opioid Assessment for Patients with Pain-Revised (SOAPP-R) predicts increased risk of opioid misuse in chronic pain patients. We evaluated whether higher SOAPP-R scores are associated with greater opioid reinforcing properties, potentially contributing to their predictive utility. Across 2 counterbalanced laboratory sessions, 55 chronic low back pain sufferers completed the SOAPP-R at baseline and measures of back pain intensity, evoked pain responsiveness (thermal, ischemic), and subjective opioid effects after receiving intravenous morphine (.08 mg/kg) or saline placebo. Morphine effect measures were derived for all outcomes, reflecting the difference between morphine and placebo condition values. Higher SOAPP-R scores were significantly associated with greater desire to take morphine again, less feeling down and feeling bad, and greater reductions in sensory low back pain intensity following morphine administration. This latter effect was due primarily to SOAPP-R content assessing medication-specific attitudes and behavior. Individuals exceeding the clinical cutoff (18 or higher) on the SOAPP-R exhibited significantly greater morphine liking, desire to take morphine again, and feeling sedated; less feeling bad; and greater reductions in sensory low back pain following morphine. The SOAPP-R may predict elevated opioid risk in part by tapping into individual differences in opioid reinforcing effects. ⋯ Based on placebo-controlled morphine responses, associations were observed between higher scores on a common opioid risk screener (SOAPP-R) and greater desire to take morphine again, fewer negative subjective morphine effects, and greater analgesia. Opioids may provide the best analgesia in those patients at greatest risk of opioid misuse.
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Randomized Controlled Trial
Efficacy of Inhaled Cannabis on Painful Diabetic Neuropathy.
A randomized, double-blinded, placebo controlled crossover study was conducted in 16 patients with painful diabetic peripheral neuropathy to assess the short-term efficacy and tolerability of inhaled cannabis. In a crossover design, each participant was exposed to 4 single dosing sessions of placebo or to low (1% tetrahydrocannabinol [THC]), medium (4% THC), or high (7% THC) doses of cannabis. Baseline spontaneous pain, evoked pain, and cognitive testing were performed. Subjects were then administered aerosolized cannabis or placebo and the pain intensity and subjective "highness" score was measured at 5, 15, 30, 45, and 60 minutes and then every 30 minutes for an additional 3 hours. Cognitive testing was performed at 5 and 30 minutes and then every 30 minutes for an additional 3 hours. The primary analysis compared differences in spontaneous pain over time between doses using linear mixed effects models. There was a significant difference in spontaneous pain scores between doses (P < .001). Specific significant comparisons were placebo versus low, medium, and high doses (P = .031, .04, and <.001, respectively) and high versus low and medium doses (both P < .001). There was a significant effect of the high dose on foam brush and von Frey evoked pain (both P < .001). There was a significant negative effect (impaired performance) of the high dose on 2 of the 3 neuropsychological tests (Paced Auditory Serial Addition Test, Trail Making Test Part B. ⋯ This small, short-term, placebo-controlled trial of inhaled cannabis demonstrated a dose-dependent reduction in diabetic peripheral neuropathy pain in patients with treatment-refractory pain. This adds preliminary evidence to support further research on the efficacy of the cannabinoids in neuropathic pain.
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The Centrality of Pain Scale (COPS) is a recently developed patient-centered, 10-item self-report measure designed to assess how central, or dominating, in their lives individuals with chronic pain perceive pain to be. The COPS underwent initial development and validation previously; preliminary results suggested that the measure had excellent psychometric properties and that COPS scores were associated with important clinical factors. The purpose of the present study was to examine the psychometric properties of the COPS in a sample of individuals with mixed chronic pain diagnoses (N = 178) being treated at a U.S. Veterans Affairs Medical Center. Principal components analysis of COPS items revealed a single factor, and all items loaded highly. The COPS had high internal consistency (Cronbach's alpha = .902) and was significantly correlated with other measures of pain, mental health, psychological factors associated with pain, and chronic pain coping styles, suggesting convergent and divergent validity. Hierarchical linear regression analyses indicated that COPS score was independently associated with both pain severity and interference. Future research should evaluate the generalizability of the COPS in different samples, its responsiveness to treatment, and the extent to which pain centrality may be a focus of nonpharmacologic interventions for chronic pain. ⋯ We conducted psychometric testing of the COPS, a recently developed patient-centered self-report measure designed to examine how central or dominating pain is to a person's life. Study results indicated a reliable and valid measure, which was significantly associated with pain severity and interference, even after controlling for demographic and clinical factors.
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The μ-opioid receptor 1 (OPRM1) binds endogenous opioids. Increasing evidence suggests that endogenous OPRM1 agonists released at the time of trauma may contribute to the development of posttraumatic musculoskeletal pain (MSP). In this prospective observational study, we evaluated the hypothesis that individuals with an AG or GG genotype at the OPRM1 A118 G allele, which results in a reduced response to opioids, would have less severe MSP 6 weeks after motor vehicle collision (MVC). Based on previous evidence, we hypothesized that this effect would be sex-dependent and most pronounced among women with substantial peritraumatic distress. European American men and women ≥ 18 years of age presenting to the emergency department after MVC and discharged to home after evaluation (N = 948) were enrolled. Assessments included genotyping and 6-week evaluation of overall MSP severity (0-10 numeric rating scale). In linear regression modeling, a significant A118 G Allele × Sex interaction was observed: an AG/GG genotype predicted reduced MSP severity among women with substantial peritraumatic distress (β = -.925, P = .014) but not among all women. In contrast, men with an AG/GG genotype experienced increased MSP severity at 6 weeks (β = .827, P = .019). Further studies are needed to understand the biologic mechanisms mediating observed sex differences in A118 G effects. ⋯ These results suggest a sex-dependent mechanism by which an emotional response to trauma (distress) contributes to a biologic mechanism (endogenous opioid release) that increases MSP in the weeks after stress exposure. These results also support the hypothesis that endogenous opioids influence pain outcomes differently in men and women.
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There is increasing interest in the measurement of "readiness to change," or willingness to engage in a self-management approach to pain coping, as a predictor of treatment response in pediatric pain populations. The primary aim of the present study was to provide cross-validation of the Pain Stages of Change Questionnaire-Adolescent and -Parent versions in a new, independent pediatric chronic pain sample by examining aspects of reliability, validity, and generalizability of the factor structures identified in the initial validation study. Secondary aims were to 1) expand upon previously identified differences between the Pain Stages of Change Questionnaire-Adolescent and -Parent versions and 2) examine previously unreported aspects of father data. Although slight differences emerged, the factor structures identified in the initial validation were largely replicated, suggesting that the psychometric properties of the measure are robust across pediatric outpatient chronic pain samples. Variability between parent and adolescent reports suggests that there may be meaningful differences in the interpretation of each measure and that factors other than readiness to change may influence response patterns. Findings highlight the need for more fine-tuned analyses of the way the construct operates in youth with pediatric pain and their parents. ⋯ Findings provide further validation of the Pain Stages of Change Questionnaire-Adolescent and -Parent versions measures in a new outpatient pediatric chronic pain sample. Previously uninvestigated father data showed good reliability and patterns of findings similar to validated mother reports. Moreover, the study suggests that the adolescent and parent versions may function in meaningfully different ways.