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.
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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
Characterizing individual differences in heat-pain sensitivity.
Heat induced pain has been shown to follow a positively accelerating power function for groups of subjects, yet the extent to which this applies to individual subjects is unknown. Statistical methods were developed for assessing the goodness of fit and reliability of the power function for data from individual subjects with the aim of using such functions for characterizing individual differences in heat-pain sensitivity. 175 subjects rated ascending and random series of contact heat stimuli with visual analogue scales for pain intensity (VAS-I) and unpleasantness (VAS-A). Curve fitting showed excellent model fit. ⋯ Exponent reliability was high for the ascending series (VAS-I=.92; VAS-A=.91), but considerably lower for the random series (VAS-I=.69; VAS-A=.71). Individual differences constituted 60% of the total variance in pain ratings, whereas stimulus temperature accounted for only 40%. This finding underscores the importance of taking individual differences into account when performing pain studies.
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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.