Pain
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Recent data suggest that comorbid substance use disorders (SUDs) are common among chronic non-cancer pain (CNCP) patients; however, prevalence rates vary across studies and findings are limited regarding treatment options for CNCP patients with comorbid SUD. The purpose of this systematic review is to assess the prevalence, associated demographic and clinical characteristics, and treatment outcomes for CNCP patients with comorbid SUD. We conducted searches from Ovid MEDLINE, PsychINFO, and PubMED from 1950 through February 2010 and retrieved the references. ⋯ Limited data are available to identify predictors of treatment outcome. Although clinical experience and research suggests that SUDs are common among CNCP patients, only limited data are available to guide clinicians who treat this population. Research is needed to increase understanding of the prevalence, correlates, and responses to treatment of CNCP patients with comorbid SUDs.
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Sphingosine-1-phosphate (S1P) is an important mediator of inflammation recently shown in in vitro studies to increase the excitability of small-diameter sensory neurons, at least in part, via activation of the S1P(1) receptor subtype. Activation of S1PR(1) has been reported to increase the formation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived superoxide (O(2)(·-)) and nitric oxide synthase (NOS)-derived nitric oxide (NO). This process favors the formation of peroxynitrite (ONOO(-) [PN]), a potent mediator of hyperalgesia associated with peripheral and central sensitization. ⋯ The development of S1P-induced hyperalgesia was blocked by apocynin, a NADPH oxidase inhibitor; N(G)-nitro-l-arginine methyl ester, a nonselective NOS inhibitor; and by the potent PN decomposition catalysts (FeTM-4-PyP(5+) and MnTE-2-PyP(5+)). Our findings provide mechanistic insight into the signaling pathways engaged by S1P in the development of hyperalgesia and highlight the contribution of the S1P(1) receptor-to-PN signaling in this process. Sphingosine-1-phosphate (S1P)-induced hyperalgesia is mediated by S1P1 receptor activation and mitigated by inhibition or decomposition of peroxynitrite, providing a target pathway for novel pain management strategies.
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The transient receptor potential ankyrin 1 (TRPA1) ion channel is expressed on nociceptive primary afferent neurons. On the proximal nerve ending within the spinal dorsal horn, TRPA1 regulates transmission to spinal interneurons, and thereby pain hypersensitivity. Here we assessed whether the contribution of the spinal TRPA1 channel to pain hypersensitivity varies with the experimental pain model, properties of test stimulation or the behavioral pain response. ⋯ Conversely, i.t. administration of a TRPA1 channel agonist, cinnamon aldehyde, induced mechanical hypersensitivity. The results indicate that the spinal TRPA1 channel exerts an important role in secondary (central) pain hypersensitivity to low-intensity mechanical stimulation in various pain hypersensitivity conditions. The spinal TRPA1 channel provides a promising target for the selective attenuation of a central mechanism contributing to pathophysiological pain.
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Randomized Controlled Trial Comparative Study Clinical Trial
A randomised, five-parallel-group, placebo-controlled trial comparing the efficacy and tolerability of analgesic combinations including a novel single-tablet combination of ibuprofen/paracetamol for postoperative dental pain.
Combination analgesia is often recommended for the relief of severe pain. This was a double-blind, 5-arm, parallel-group, placebo-controlled, randomised, single-dose study designed to compare the efficacy and tolerability of a novel single-tablet combination of ibuprofen and paracetamol with that of an ibuprofen/codeine combination, and a paracetamol/codeine combination, using the dental impaction pain model. Subjects with at least 3 impacted third molars and experiencing moderate to severe postoperative pain were randomised to receive: 1 or 2 tablets of a single-tablet combination of ibuprofen 200mg/paracetamol 500mg; 2 tablets of ibuprofen 200 mg/codeine 12.8mg; 2 tablets of paracetamol 500mg/codeine 15mg; or placebo. ⋯ Adverse events were uncommon during this study and treatment emergent adverse events were statistically significantly less frequent in the groups taking the ibuprofen/paracetamol combination compared with codeine combinations. In conclusion, 1 or 2 tablets of a single-tablet combination of ibuprofen 200mg/paracetamol 500mg provided highly effective analgesia that was comparable with, or superior to, other combination analgesics currently indicated for strong pain. A single-tablet combination of ibuprofen 200mg/paracetamol 500mg provides highly effective analgesia, comparable or superior to other combination analgesics indicated for strong pain.