Articles: hyperalgesia.
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Drug combinations have the potential advantage of greater analgesia over monotherapy. The present study was aimed to assess any possible interaction (additive or potentiation) in the antinociceptive effects of etoricoxib; a novel cyclooxygenase-2 inhibitor, and tramadol; a typical opioid agonist when administered in combination against mechanical hyperalgesia induced by spinal cord injury in rats. The nature of interaction was analyzed using surface of synergistic interaction (SSI) analysis and an isobolographic analysis. ⋯ The SSI was calculated from the total antihyperalgesic effect produced by the combination after the subtraction of the antihyperalgesic effect produced by each of the individual drug. In the isobolographic analysis, the experimental ED50 was found to be far below the line of additivity also indicating a significant (P < 0.05) synergistic antihyperalgesic effect when etoricoxib and tramadol was co-administered to rats. The synergistic antihyperalgesic effect of etoricoxib and tramadol combination suggests that these combinations may have clinical utility in mechanical hyperalgesia associated with spinal injury.
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Comparative Study
Reliability of pain threshold measurement in young adults.
The objective was to examine reliability of pressure and thermal (cold) pain threshold assessment in persons less than 25 years of age, using intra-class correlation (ICC) and coefficients of repeatability and variability. We measured thresholds to pain from pressure algometry and ice placed at the hand and head in 10 healthy volunteers aged 18-25. Intra-rater reliability was examined with ICC. ⋯ Reliability of repeat assessments was high as assessed by ICC, although coefficients of repeatability and variation indicated considerable inter-individual variation in repeat measurements. Pressure algometry and strategically placed ice appear to be reliable techniques for assessing pain processing in young adults. Reliability studies employing ICC may benefit from complementary estimation of CR and CV.
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Opioid analgesics are effective for treating many pain conditions. Opioid analgesic tolerance is a pharmacologic phenomenon that could affect the clinical use of opioid analgesics. ⋯ Thus, exposure to opioids could lead to two seemingly unrelated cellular processes (ie, the development of opioid tolerance and opioid-induced pain sensitivity). Their converging effects may be part of the mechanisms leading to the reduced opioid analgesic efficacy in chronic opioid therapy.
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Wien. Klin. Wochenschr. · Feb 2006
Controlled Clinical TrialHyperalgesia against capsaicin in persons with un-investigated dyspepsia: potential as a new diagnostic test.
Lack of understanding of the pathogenesis of functional dyspepsia is one reason for the paucity of effective treatment options. Whereas mechanical sensitivity in persons suffering from dyspepsia might be impaired, chemically induced hypersensitivity has received little attention. The aim of this study was to evaluate whether vanilloid receptors stimulated by capsaicin are hypersensitive in persons with dyspepsia. ⋯ Jejunal sensitivity to capsaicin is increased in persons with un-investigated dyspepsia, and vanilloid receptors might be involved in the pathophysiology of this condition. Patients with hypersensitivity to chemical stimuli may represent a distinct subpopulation based on the underlying pathophysiology and may require specific treatment to restore normal visceral sensitivity.
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Melittin, which is a principal protein of honeybee venom, can induce mechanical hyperalgesia in humans. The characteristics of the melittin induced mechanical hyperalgesia are quantitatively and qualitatively different from those evoked by capsaicin. The aim of the present study was to investigate in detail secondary heat hyperalgesia induced by melittin in humans. ⋯ The pain rating index at 60 min was significantly larger than at 5 min (P=0.04) and at 30 min (P=0.03). These results demonstrated slowly developing secondary heat hyperalgesia after injection of melittin. A possible contribution of peripheral inflammatory responses to the manifestation of secondary heat hyperalgesia is suggested, which in reality render the distinction between the primary and secondary area of heat hyperalgesia unnecessary.