Pain
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Randomized Controlled Trial Multicenter Study
Psychosocial factors predict opioid analgesia via endogenous opioid function.
Use of opioid analgesics for management of chronic nonmalignant pain has become common, yet there are presently no well-validated predictors of optimal opioid analgesic efficacy. We examined whether psychosocial factors (eg, depressive symptoms) predicted changes in spontaneous low back pain after administration of opioid analgesics, and whether endogenous opioid (EO) function mediated these relationships. Participants with chronic low back pain but who were not chronic opioid users (N = 89) underwent assessment of low back pain intensity pre- and post-drug in 3 (counterbalanced) conditions: (1) placebo, (2) intravenous naloxone, and (3) intravenous morphine. ⋯ Bootstrapped mediation analyses showed that links between morphine analgesic responses and depressive symptoms, trait anxiety, pain catastrophizing, and perceived disability were partially mediated by EO function. Results suggest that psychosocial factors predict elevated analgesic responses to opioid-based medications, and may serve as markers to identify individuals who benefit most from opioid therapy. Results also suggest that people with greater depressive symptoms, trait anxiety, pain catastrophizing, and perceived disability may have deficits in EO function, which may predict enhanced response to opioid analgesics.
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Health utilities are a preference-based measure of health-related quality of life that facilitates comparison of disease burden across conditions. We estimated utilities using a population-based, matched sample of adolescents and adults with and without chronic pain, controlling for comorbidity. Ontarians aged ≥12 years with and without chronic pain were identified from the Canadian Community Health Survey (CCHS) 2000-2001 and 2009-2010 and linked to their provincial health care administrative data. ⋯ The matched cohort with chronic pain had a mean utility of 0.59 (95% confidence interval 0.58-0.59), and the decrement associated with chronic pain was 0.32 (95% confidence interval 0.31-0.32). Utilities in people with chronic pain were lower than, and decrements larger than, those seen with most other chronic diseases including heart disease, diabetes, and chronic obstructive pulmonary disease. These data will be useful to inform priorities and future strategies for the prevention and control of chronic pain.
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Attitudes to pain medication are important aspects of adjustment to chronic pain. They are measured by the 47-item Pain Medication Attitudes Questionnaire (PMAQ). To measure those attitudes more quickly and easily, we developed and evaluated a 14-item PMAQ using data from 3 separate surveys of people with pain in the general population. ⋯ Confirmatory factor analysis showed that the 14-item PMAQ retained the 7-factor structure of the 47-item version, and correlations with other measures showed that it retained the validity of the 47-item version. The PMAQ scale Need was the most significant independent predictor of analgesic dependence in each of 4 separate multiple regression analyses. This short form of the PMAQ allows attitudes to pain medications to be measured in a valid and more efficient way.
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Several factors may accelerate opioid discontinuation rates, including lack of information about the long-term effectiveness of opioids for chronic pain, heightened awareness about opioid-related adverse events, closer monitoring of patients for opioid-related aberrant behaviors, and greater restrictions around opioid prescribing. Rates of discontinuation may be most pronounced in patients deemed to be at "high risk." The purpose of this study was to compare reasons for discontinuation of long-term opioid therapy (LTOT) between patients with and without substance use disorder (SUD) diagnoses receiving care within a major U. S. health care system. ⋯ Relative to patients without SUD diagnoses, those with SUD diagnoses were more likely to discontinue LTOT because of aberrant behaviors (81% vs 68%), most notably abuse of alcohol or other substances. This is the first study to document reasons for discontinuation of LTOT in a sample of patients with and without SUD diagnoses. Treatments that concurrently address SUD and chronic pain are needed for this high-risk population.
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Tactile allodynia, a condition in which innocuous mechanical stimuli are perceived as painful, is a common feature of chronic pain. However, how the brain reorganizes in relation to the emergence of tactile allodynia is still largely unknown. This may stem from the fact that experiments in humans are cross-sectional in nature, whereas animal brain imaging studies typically require anaesthesia rendering the brain incapable of consciously sensing or responding to pain. ⋯ In contrast, nucleus accumbens and prefrontal brain areas displayed abnormal activity to normally innocuous stimuli when such stimuli induced tactile allodynia at 28 days after peripheral nerve injury, which had not been the case at 5 days after injury. Our data indicate that tactile allodynia-related nociceptive inputs are not observable in the primary somatosensory cortex BOLD response. Instead, our data suggest that, in time, tactile allodynia differentially engages neural circuits that regulate the affective and motivational components of pain.