European journal of pain : EJP
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Randomized Controlled Trial
Population pharmacokinetic-pharmacodynamic modeling of ketamine-induced pain relief of chronic pain.
Pharmacological treatment of chronic (neuropathic) pain is often disappointing. In order to enhance our insight in the complex interaction between analgesic drug and chronic pain relief, we performed a pharmacokinetic-pharmacodynamic (PK-PD) modeling study on the effect of S(+)-ketamine on pain scores in Complex Regional Pain Syndrome type 1 (CRPS-1) patients. ⋯ Long-term S(+)-ketamine treatment is effective in causing pain relief in CRPS-1 patients with analgesia outlasting the treatment period by 50 days. These data suggest that ketamine initiated a cascade of events, including desensitization of excitatory receptor systems in the central nervous system, which persisted but slowly abated when ketamine molecules were no longer present.
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Autonomic neuropathy seems to play a central role in the development of gastrointestinal symptoms in diabetes. In order to explore the neuronal mechanisms behind the symptoms we evaluated the brain processing of painful visceral stimuli. ⋯ There is evidence of altered central processing to visceral stimulation, and both peripheral and central mechanisms seem involved. Central neuronal reorganisation may contribute to our understanding of the gastrointestinal symptoms in patients with diabetic autonomic neuropathy and this may guide development and evaluation of new treatment modalities.
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Persistent postsurgical pain has been reported following cosmetic breast augmentation, but little is known about the underlying mechanisms. ⋯ Sensory changes and persistent pain are common following cosmetic breast augmentation and may have a negative impact on daily activities and satisfaction after surgery. Findings suggest that neuropathic pain should be considered in these patients. Preoperative information about the risk of developing sensory changes and chronic pain after breast augmentation is important.
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Insensitivity to pain is a rare disorder that is commonly associated with Hereditary Sensory and Autonomic Neuropathies (HSAN I-V) resulting often in autonomic dysfunction and premature death. Very few individuals have been reported with pain insensitivity lacking such autonomic neuropathies. We performed genetic, neurologic, psychological, and psychophysical evaluations in such an individual (OMIM 243000) and her first degree relatives. ⋯ Congenital insensitivity to pain in our IC was associated with two novel SCN9A mutations which most likely resulted in a Nav1.7 channelopathy. However, in contrast to individuals with other SCN9A mutations, the observed pain insensitivity was relative and not absolute, which may be consistent with hypomorphic effects of one or both mutations. The ability to sense at least some danger signals may be advantageous and ameliorate the otherwise increased morbidity and mortality of some individuals with congenital insensitivity to pain.
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Motor cortex stimulation (MCS) has been used to treat patients with neuropathic pain resistant to other therapeutic approaches; however, the mechanisms of pain control by MCS are still not clearly understood. We have demonstrated that MCS increases the nociceptive threshold of naive conscious rats, with opioid participation. In the present study, the effect of transdural MCS on neuropathic pain in rats subjected to chronic constriction injury of the sciatic nerve was investigated. ⋯ Zif268 results were similar to those obtained for Fos, although no changes were observed for Zif268 in the anterior cingulate cortex and the central amygdaloid nucleus after MCS. The present findings suggest that MCS reverts neuropathic pain phenomena in rats, mimicking the effect observed in humans, through activation of the limbic and descending pain inhibitory systems. Further investigation of the mechanisms involved in this effect may contribute to the improvement of the clinical treatment of persistent pain.