Pain
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Randomized Controlled Trial Clinical Trial
Analgesic effects of dextromethorphan and morphine in patients with chronic pain.
N-methyl-aspartate (NMDA) receptor antagonists have been shown to improve opioid analgesia in the animal model. The cough suppressant dextromethorphan is a clinically available NMDA-receptor antagonist. In this randomised, double-blind, placebo-controlled study 20 patients with chronic pain of several years duration were given 100 mg of oral dextromethorphan or matching placebo 4 h prior to an intravenous infusion of morphine 15 mg. ⋯ The most common adverse effects reported were dizziness, nausea and sedation. There were no significant differences in either the incidence or severity of adverse effects. In conclusion, oral dextromethorphan 100 mg had no effect on pain relief by intravenous morphine 15 mg in patients with chronic pain.
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The spinothalamic tract (STT) is a major ascending nociceptive pathway, interruption of which by cordotomy is used for pain relief, whereas the dorsal column (DC) pathway is usually not considered to be involved in pain transmission. However, recent clinical studies showed good relief of visceral pain in cancer patients after a DC lesion. Electrophysiological recordings in animals suggest that the analgesic effect is due to interruption of axons ascending from postsynaptic dorsal column (PSDC) neurons located in the vicinity of the central canal. ⋯ Intradermal capsaicin injection almost abolished exploratory activity in naïve animals or in rats after a DC lesion, but did not change it in rats after ipsilateral dorsal rhizotomy or a lesion of the lateral funiculus on the side opposite to the injection. In contrast, a bilateral DC lesion counteracted the decrease in exploratory activity induced by noxious visceral stimuli for at least 180 days after the surgery. Although neurons projecting in both the STT and the PSDC path can be activated by noxious stimuli of cutaneous or visceral origin, our results suggest that the STT plays a crucial role in the perception of acute cutaneous pain and that the DC pathway is important for transmission of visceral pain.
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Randomized Controlled Trial Clinical Trial
Lamotrigine in spinal cord injury pain: a randomized controlled trial.
The objective was to investigate the effectiveness of lamotrigine for the treatment of spinal cord injury pain and clinical signs of neuronal hyperexcitability. Thirty patients with spinal cord injury (SCI) and at or below level neuropathic pain participated in a randomized double blind, placebo-controlled, crossover trial. A 1-week baseline period was followed by two treatment periods of 9 weeks duration with lamotrigine slowly increased to a maximum of 400 mg or placebo separated by a 2-week washout period. ⋯ Patients with brush evoked allodynia and wind-up-like pain in the area of maximal pain were more likely to have a positive effect to lamotrigine than patients without these evoked pains (7 of 7 vs. 1 of 14). Lamotrigine was generally well tolerated. While this trial showed no significant effect on spontaneous and evoked pain in complete and incomplete spinal cord injury, lamotrigine reduced spontaneous pain in patients with incomplete spinal cord injury and evoked pain in the area of spontaneous pain.
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Comparative Study
Group differences in pain modulation: pain-free women compared to pain-free men and to women with TMD.
Previously reported differences in sensitivity to experimental pain stimuli between the sexes, as well as between temporomandibular disorder (TMD) patients and healthy control subjects, may be attributable in part to group differences in two pain modulatory mechanisms: the baroreceptor reflex arc and the endogenous opioid system. Twenty-two pain-free (PF) men, 20 PF women and 20 women with TMD underwent two testing sessions in which heat pain and ischemic arm pain threshold and tolerance were measured during both sessions, but followed relaxation during one session and laboratory stress tasks during the other. Blood pressure (BP) and plasma -endorphin (E) concentration were measured during a baseline rest and during the stress or relaxation periods. ⋯ Thus, it appears that a BP-related analgesic mechanism (probably baroreceptor-mediated) predominates in PF men, while an endogenous opioid mechanism predominates in PF women. Stress enhances the expression of these central mechanisms. Female TMDs appear unable to effectively engage normal pain-inhibitory systems; opioid receptor desensitization and/or downregulation are probably implicated, because TMDs' production of E appears normal.
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Clinical Trial
Pitfalls of opioid rotation: substituting another opioid for methadone in patients with cancer pain.
The successful use of methadone in cancer pain has been supported by numerous case reports and clinical studies. Methadone is usually used as a second or third line opioid medication. As the use of methadone increases we are facing the challenge of converting methadone to other opioids as part of sequential opioid trials. ⋯ These symptoms may not improve despite upward titration of the second opioid. A uniformly accepted conversion ratio for substituting methadone with another opioid is currently not available. More data on the rotation from methadone to other opioids are needed.