Pain
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The clinically available NMDA-receptor antagonist drug, amantadine, has been shown to result in morphine sparing effects in humans after surgery. However, no data are available to describe the exact form of interaction. The present study aims to profile the possible effects of amantadine (0, 12.5, 25 or 50 mgkg(-1) i.p.) pre-treatment on morphine (0, 0.63, 1.25, 2.5 or 5 mgkg(-1) s.c.) induced antinociception in rats. ⋯ No evidence was found to indicate that amantadine induced motor impairment at the doses potentiating morphine during the second phase of the formalin test. There was no evidence for a pharmacokinetic interaction between amantadine and morphine. Since, the second phase of the formalin test is dependent on activation of the NMDA receptor system it is concluded that an antagonistic activity of amantadine at the NMDA receptor most likely contributes to the synergistic interaction observed between amantadine and morphine in rats.
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Randomized Controlled Trial
The role of threat-expectancy in acute pain: effects on attentional bias, coping strategy effectiveness and response to pain.
The aims of this study were threefold. Firstly, to investigate the effect of increasing threat-expectancy on attentional biases towards pain-related words. Secondly, to determine the interaction between threat-expectancy and the effectiveness of two coping strategies on pain threshold and tolerance. ⋯ The present results provide support for the fear-avoidance model of pain [Vlaeyen JWS, Linton SJ. Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art. Pain 2000;85:317-332] and confirm the importance of threat-expectancy in hypervigilance towards pain and fear avoidance.
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Clinical Trial
The economic impact of chronic pain in adolescence: methodological considerations and a preliminary costs-of-illness study.
Chronic pain in adulthood is one of the most costly conditions in modern western society. However, very little is known about the costs of chronic pain in adolescence. This preliminary study explored methods for collecting economic-related data for this population and estimated the cost-of-illness of adolescent chronic pain in the United Kingdom. ⋯ The adolescents attending a specialised pain management unit, who had predominantly non-inflammatory pain, accrued significantly higher costs, than those attending rheumatology outpatient clinics, who had mostly inflammatory diagnoses. Extrapolating the mean total cost to estimated UK prevalence data of adolescent chronic pain demonstrates a cost-of-illness to UK society of approximately 3,840 million pounds in one year. The implications of the study are discussed.
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Nitric oxide (NO) acts as a neurotransmitter or neuromodulator involving in the modulation of thermal and/or inflammatory hyperalgesia. The neuronal nitric oxide synthase (nNOS) is a key enzyme for NO production in normal neuronal tissues, but its functional role in chronic pain remains unclear. The present study combined a genetic strategy with a pharmacologic approach to address the role of nNOS in the central mechanism of complete Freund's adjuvant (CFA)-induced chronic inflammatory pain. ⋯ Finally, spinal cord nNOS (but not endothelial NOS or inducible NOS) expression was up-regulated at 24h after CFA injection, occurring mainly in the ipsilateral superficial dorsal horn. Together, these data indicate that spinal cord nNOS may be essential for the maintenance of mechanical pain hypersensitivity and that it may also be sufficient for the development of mechanical pain hypersensitivity and for the development and maintenance of thermal pain hypersensitivity after chronic inflammation. Our findings suggest that spinal cord nNOS might play a critical role in central mechanisms of the development and/or maintenance of chronic inflammatory pain.
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Use of opioids for chronic non-cancer pain is increasing, but the clinical epidemiology and standards of care for this practice are poorly defined. Psychiatric disorders are associated with increased physical symptoms and may be associated with opioid use. We performed a secondary analysis of cross-sectional data from the Health Care for Communities (HCC) survey conducted in 1997-1998 (N=9279) to determine the association of psychiatric disorders and self-reported regular use of prescribed opioids within the past year. ⋯ In multivariate logistic regression models controlling for demographic and clinical variables, the presence of a common mental disorder remained a significant predictor of prescription opioid use (OR=3.15, 95% CI=1.69, 5.88, P<0.001), among individuals reporting low pain interference (N=8307); but not (OR=1.27, n.s.) among those reporting high pain interference (N=972). Depressive, anxiety and drug abuse disorders are associated with increased use of regular opioids in the general population. Depressive and anxiety disorders are more common and more strongly associated with prescribed opioid use than drug abuse disorders.