The journal of pain : official journal of the American Pain Society
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Clinical Trial
Associations between catastrophizing and endogenous pain-inhibitory processes: sex differences.
Pain catastrophizing is among the most robust predictors of pain outcomes, and a disruption in endogenous pain-inhibitory systems is 1 potential mechanism that may account for increased pain among individuals who report higher pain catastrophizing. Pain catastrophizing may negatively influence diffuse noxious inhibitory controls (DNIC), a measure of endogenous pain inhibition, through complex anatomical circuitry linking cortical responses to pain with processes that modulate pain. The current study examined whether DNIC mediated the relationship between catastrophizing and pain among 35 healthy young adults and examined the moderating effects of sex to determine whether the magnitude or direction of associations differed among men and women. DNIC was assessed using pressure pain thresholds on the forearm before and during a cold pressor task. Using bias-corrected bootstrapped confidence intervals, results showed that diminished DNIC was a significant partial mediator of the relation between greater pain-related catastrophizing and more severe pain ratings. Participant sex moderated these associations; higher catastrophizing predicted lower DNIC for men and women, however, the effect of catastrophizing on pain ratings was partially mediated by DNIC for women only. These findings further support the primary role of pain catastrophizing in modulation of pain outcomes. ⋯ These findings support the hypothesis that the heightened pain reported by individuals higher in pain catastrophizing may be related to a disruption in the endogenous modulation of pain, operationalized by assessing DNIC. Whether interventions that reduce pain catastrophizing affect pain outcomes via effects on DNIC is in need of investigation.
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The purpose of the study was to examine the effect of 3 different application strategies for transcutaneous electrical nerve stimulation (TENS) on neuropathy-induced allodynia and dorsal horn neurotransmitter content. Rats were treated with high-frequency, low-frequency, or a combination of high and low-frequency stimulation. TENS was delivered through self-adhesive electrodes daily for 1 hour to rats with a right-sided chronic constriction injury (CCI). Stimulation was delivered to skin or acupuncture points on the left and mechanical and thermal pain thresholds were assessed in the right hind paw. Neurotransmitter content was assessed bilaterally in the dorsal horn of the spinal cord. Daily, high-frequency or a combination of high- and low-frequency TENS reduced mechanical (P < .001), but not thermal allodynia in the right hind paw when compared with untreated CCI rats. Daily high frequency TENS elevated the dorsal horn synaptosomal content of GABA bilaterally (P < .014) and a combination of high- and low-frequency TENS elevated the dorsal horn content of aspartate (P < .001), glutamate (P < .001) and glycine (P < .001) bilaterally over that seen in untreated CCI rats. The present findings support a contralateral approach to the application of TENS and suggest that distinct strategies for TENS application may differentially alter neurotransmission in the central nervous system. ⋯ Because CCI rats are reminiscent of humans with neuropathy, daily high or a combination of high- and low-frequency TENS may reduce mechanical allodynia in humans with neuropathic pain. Because the 2 intervention strategies produce distinctive alterations in spinal cord neurotransmitter content, each may represent a distinctive option for treatment.
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Practice Guideline
Clinical guidelines for the use of chronic opioid therapy in chronic noncancer pain.
Use of chronic opioid therapy for chronic noncancer pain has increased substantially. The American Pain Society and the American Academy of Pain Medicine commissioned a systematic review of the evidence on chronic opioid therapy for chronic noncancer pain and convened a multidisciplinary expert panel to review the evidence and formulate recommendations. Although evidence is limited, the expert panel concluded that chronic opioid therapy can be an effective therapy for carefully selected and monitored patients with chronic noncancer pain. However, opioids are also associated with potentially serious harms, including opioid-related adverse effects and outcomes related to the abuse potential of opioids. The recommendations presented in this document provide guidance on patient selection and risk stratification; informed consent and opioid management plans; initiation and titration of chronic opioid therapy; use of methadone; monitoring of patients on chronic opioid therapy; dose escalations, high-dose opioid therapy, opioid rotation, and indications for discontinuation of therapy; prevention and management of opioid-related adverse effects; driving and work safety; identifying a medical home and when to obtain consultation; management of breakthrough pain; chronic opioid therapy in pregnancy; and opioid-related policies. ⋯ Safe and effective chronic opioid therapy for chronic noncancer pain requires clinical skills and knowledge in both the principles of opioid prescribing and on the assessment and management of risks associated with opioid abuse, addiction, and diversion. Although evidence is limited in many areas related to use of opioids for chronic noncancer pain, this guideline provides recommendations developed by a multidisciplinary expert panel after a systematic review of the evidence.
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Intraplantar injection of bee venom (BV) produces persistent spontaneous nociception (PSN) and hyperalgesia, as well as obvious inflammatory swelling, in the paws of injected rats. The present study was designed to determine the peripheral roles of mitogen-activated protein kinase (MAPK) signal transduction pathways in BV-induced nociception and inflammation. We examined the effect of intraplantar injection of an ERK1/2 inhibitor, PD98059, and a p38 inhibitor, SB202190, on BV-induced PSN, mechanical hyperalgesia, and inflammatory swelling. We found that (1) pretreatment with SB202190 (0.1 to 10 microg) had no effect on BV-induced PSN, whereas pretreatment with PD98059 (0.1 to 100 microg) produced a significant and dose-dependent inhibition of BV-induced PSN; (2) pretreatment with PD98059 (0.1 to 100 microg) had no effect on BV-induced decreases in paw withdrawal mechanical threshold (PWMT), while pretreatment with SB202190 (0.1 to 10 microg) produced an obvious prevention of the BV-induced decrease in PWMT; and (3) pretreatment with PD98059 (0.1 to 100 microg) had no effect on BV-induced increase in paw volume (PV), whereas pretreatment with SB202190 (0.1 to 10 microg) produced a dose-related inhibition of BV-induced increases in PV. No contralateral drug treatments, even at the highest dose, had any effect on BV-induced PSN, PWMT or PV, ruling out the systemic effect of these drugs. These results suggest that peripheral MAPK signal transduction pathways may play differential roles in bee venom-induced nociception and inflammation. Targeting specific peripheral MAPKs might prove effective in the treatment of persistent pain and inflammation. ⋯ The present article showed that intraplantar injection of different MAPK inhibitors produced differential effects on bee venom-induced nociception and inflammation, suggesting that the peripheral MAPK signal transduction pathways have differential roles. Targeting specific peripheral MAPKs might prove effective in the treatment of persistent pain and inflammation.
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Optimal methods to predict risk of aberrant drug-related behaviors before initiation of opioids for chronic noncancer pain and to identify aberrant behaviors after therapy is initiated are uncertain. We systematically reviewed published literature identified through searches of Ovid MEDLINE and the Cochrane databases through July 2008. Diagnostic test characteristics and accompanying confidence intervals were calculated with data extracted from the studies. Four prospective studies evaluated diagnostic accuracy of risk prediction instruments. Two higher-quality derivation studies found that high scores on the Screener and Opioid Assessment for Patients with Pain (SOAPP) Version 1 and the Revised SOAPP (SOAPP-R) instruments weakly increased the likelihood for future aberrant drug-related behaviors (positive likelihood ratios [PLR], 2.90 [95% CI, 1.91 to 4.39] and 2.50 [95% CI, 1.93 to 3.24], respectively). Low scores on the SOAPP Version 1 moderately decreased the likelihood for aberrant drug-related behaviors (negative likelihood ratio [NLR], 0.13 [95% CI, 0.05 to 0.34]) and low scores on the SOAPP-R weakly decreased the likelihood (NLR, 0.29 [95% CI, 0.18 to 0.46]), but estimates are too imprecise to determine if there is a difference between these instruments. One lower-quality study found that categorization as high risk using the Opioid Risk Tool strongly increased the likelihood for future aberrant drug-related behaviors (PLR, 14.3 [95% CI, 5.35 to 38.4]) and classification as low risk strongly decreased the likelihood (PLR, 0.08 [95% CI, 0.01 to 0.62]). Nine studies evaluated monitoring instruments for identification of aberrant drug-related behaviors in patients on opioid therapy. One higher-quality derivation study found higher scores on the Current Opioid Misuse Measure (COMM) weakly increased the likelihood of current aberrant drug-related behaviors (PLR, 2.77 [95% CI, 2.06 to 3.72]) and lower scores weakly decreased the likelihood (NLR, 0.35 [95% CI, 0.24 to 0.52]). In 8 studies of other monitoring instruments, diagnostic accuracy was poor, results were difficult to interpret due to methodological shortcomings, or standard diagnostic test characteristics were not reported. Definitions for aberrant drug-related behaviors were not standardized across studies and did not account for seriousness of identified behaviors. No reliable evidence exists on accuracy of urine drug screening, pill counts, or prescription drug monitoring programs; or clinical outcomes associated with different assessment or monitoring strategies. ⋯ Evidence on prediction and identification of aberrant drug-related behaviors is limited. Although several screening instruments may be useful, evidence is sparse and primarily based on derivation studies, and methodological shortcomings exist in all studies. Research that performs external validation, uses standardized definitions for clinically relevant aberrant drug-related behaviors, and evaluates clinical outcomes associated with different assessment and monitoring strategies is needed.