Pain
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N-Methyl-D-aspartate (NMDA) receptor antagonists have been shown to block the development of antinociceptive tolerance to morphine. Assessment of the effects of NMDA antagonists on development of antinociceptive tolerance to selective opioid mu (mu) and delta (delta) agonists, however, has not been reported. In these experiments, selective mu and delta receptor agonists, and morphine, were repeatedly administered to mice either supraspinally (i.c.v.) or systemically (s.c.), alone or after pretreatment with systemic NMDA antagonists. ⋯ Further, MK801 pretreatment also did not affect the development of tolerance to the antinociception resulting from a cold-water swim-stress episode, previously shown to be a delta-opioid mediated effect. These data lead to the suggestion that the mechanisms of tolerance to receptor selective mu and delta opioids may be regulated differently from those associated with morphine. Additionally, these findings emphasize that conclusions reached with studies employing morphine cannot always be extended to 'opiates' in general.
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The problem of pain following spinal cord injury challenges the health care community to develop new treatment strategies for patients requiring pain management. A number of pain syndromes are associated with spinal injury based on the nature of the lesion, neurological structures damaged, and secondary pathophysiological changes. Efforts to identify specific characteristics of each syndrome are an important beginning to the successful diagnosis and treatment of spinal injury pain. ⋯ Future research related to these hypotheses will need to focus on the use of appropriate injury models that simulate the pathological changes associated with human injuries and which lead to clinically relevant pain-related behaviors. Continued research directed towards an examination of these proposed mechanisms will also require new research strategies and a cooperative working relationship between basic and clinical scientists. In this review the clinical characteristics of spinal injury pain and the results of experimental studies are discussed.
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The objective of this study was to review the effectiveness and safety of antidepressants in neuropathic pain. In a systematic review of randomised controlled trials, the main outcomes were global judgements, pain relief or fall in pain intensity which approximated to more than 50% pain relief, and information about minor and major adverse effects. Dichotomous data for effectiveness and adverse effects were analysed using odds ratio and number needed-to-treat (NNT) methods. ⋯ Compared with placebo, of 100 patients with neuropathic pain who are given antidepressants, 30 will obtain more than 50% pain relief, 30 will have minor adverse reactions and four will have to stop treatment because of major adverse effects. With very similar results for anticonvulsants it is still unclear which drug class should be first choice. Treatment would be improved if we could harness the dramatic improvement seen on placebo in some of the trials.
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Clinical Trial Controlled Clinical Trial
Effect of present pain and mood on the memory of past postoperative pain in women treated surgically for breast cancer.
In our recent retrospective study on breast cancer patients, the intensity of the past postoperative pain was a primary factor in predisposing the development of chronic post-treatment pain. The present prospective study was designed to find out if the remembered intensity of postoperative pain (RIPP) after breast surgery was influenced by the development of chronic pain and if the RIPP had any correlation with the development of depression or anxiety. The patient's estimation of the severity of the RIPP was determined three times in the year after surgery. ⋯ Their depression remained at a higher level during the first year after surgery. The results suggest that the amount of postoperative pain may play a role in the development of chronic pain. However, the development of chronic pain is connected to a tendency to overestimate previous pain and to higher levels of depression.
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Comparative Study Clinical Trial
Secondary hyperalgesia to mechanical but not heat stimuli following a capsaicin injection in hairy skin.
A psychophysical investigation was carried out to examine whether heat hyperalgesia exists within the secondary mechanical hyperalgesia zone surrounding a capsaicin injection site on hairy skin. A non-contact laser stimulator was used to deliver temperature controlled stimuli to sites within and outside the zone of mechanical hyperalgesia. Heat testing was carried out before and after the intradermal injection of 50 micrograms of capsaicin into the volar forearm. ⋯ Thus, there was no evidence for heat hyperalgesia within the zone of secondary hyperalgesia to punctate mechanical stimuli. Though the areas of punctate and stroking hyperalgesia were correlated, no correlation existed between the magnitude of capsaicin evoked pain and the areas mechanical hyperalgesia to punctuate and stroking stimuli or the area of flare. This suggests that independent mechanisms may mediate evoked pain, central sensitization that leads to mechanical hyperalgesia, and axon reflexive flare.