Pain
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Although more severe acute postoperative pain increases the risk of chronic pain following breast cancer surgery, few studies have examined the characteristics of patients who develop greater acute pain. To identify risk factors for acute pain and its persistence one month following breast cancer surgery, a sample of 114 women scheduled for breast cancer surgery was assessed preoperatively for demographic, clinical, and emotional functioning variables that were hypothesized to be associated with acute pain severity. ⋯ In multiple logistic regression analyses, greater preoperative anxiety was the only variable that made an independent contribution to predicting clinically meaningful acute pain at 2 days after surgery whereas younger age, being unmarried, and preoperative anxiety each made an independent contribution to predicting clinically meaningful acute pain that persisted from 2 to 30 days after surgery. These results increase understanding of neurobiologic mechanisms and psychosocial processes that contribute to the development of acute pain following breast cancer surgery and have implications for the development of interventions to prevent it.
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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.
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P2X3 and P2X2/3 receptors in dorsal root ganglia (DRG) appear to participate in producing nociceptive responses after nerve injury. However, the mechanisms underlying the receptor-mediated nociception in the neuropathic state remain unclear. Using spared nerve injury (SNI) rats, we found that allodynic and nocifensive (flinch) behavioral responses developed after injury can be reversed by P2X receptor antagonists, indicating an involvement of P2X receptors. ⋯ ATP-induced P2X3 receptor-mediated currents in DRG neurons is 2.5-fold larger after SNI. The expression of P2X3 receptors on the cell membrane is significantly enhanced while the total expression of P2X3 receptors remained unchanged. Thus, the enhancement of trafficking of P2X3 receptors is likely an important mechanism contributing to the increase in receptor function after nerve injury.
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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
A randomized, double-blind, placebo-controlled trial of duloxetine in the treatment of women with fibromyalgia with or without major depressive disorder.
This was a 12-week, randomized, double-blind, placebo-controlled trial to assess the efficacy and safety of duloxetine, a selective serotonin and norepinephrine reuptake inhibitor, in 354 female patients with primary fibromyalgia, with or without current major depressive disorder. Patients (90% Caucasian; mean age, 49.6 years; 26% with current major depressive disorder) received duloxetine 60 mg once daily (QD) (N=118), duloxetine 60 mg twice daily (BID) (N=116), or placebo (N=120). The primary outcome was the Brief Pain Inventory average pain severity score. ⋯ Compared with patients on placebo, patients treated with duloxetine 60 mg QD or duloxetine 60 mg BID had significantly greater improvement in remaining Brief Pain Inventory pain severity and interference scores, Fibromyalgia Impact Questionnaire, Clinical Global Impression of Severity, Patient Global Impression of Improvement, and several quality-of-life measures. Both doses of duloxetine were safely administered and well tolerated. In conclusion, both duloxetine 60 mg QD and duloxetine 60 mg BID were effective and safe in the treatment of fibromyalgia in female patients with or without major depressive disorder.