Pain
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Clinical Trial Controlled Clinical Trial
Topical EMLA pre-treatment fails to decrease the pain induced by 1% topical capsaicin.
Topical capsaicin has been reported to be beneficial for the treatment of neurogenic pain. However, due to the burning pain associated with topical capsaicin, many patients discontinue treatment before therapeutic benefits are obtained. This study assessed the efficacy of EMLA (eutectic mixture of 2.5% prilocaine and 2.5% lidocaine) to block pain induced by the topical application of 1% capsaicin. ⋯ The 6 h treatment with high dose topical capsaicin (1%) produced significant desensitization to heat stimuli that was not affected by EMLA treatment. EMLA fails to produce a long lasting attenuation of the pain induced by topical application of 1% capsaicin. These results argue against the use of EMLA to block pain to topical capsaicin during the treatment of neurogenic pain.
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Complex regional pain syndrome (CRPS) remains a poorly understood chronic pain disorder. Little data has been published assessing the epidemiology of CRPS (and reflex sympathetic dystrophy, RSD). This study assessed epidemiological variables in 134 CRPS patients evaluated at a tertiary chronic pain clinic in the US, including demographic, health care utilization and legal/workman's compensation measures. ⋯ The duration of CRPS symptoms and the involvement of the upper extremity was significantly associated with the presence of myofascial dysfunction. Thus, this study found that most CRPS patients are referred to a pain specialty clinic after several years of symptoms and many failed therapies. The data also suggest the lack of utility of a diagnostic bone scan and highlight the prominence of myofascial dysfunction in a majority of CRPS patients.
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In the this study we have investigated the threshold plasma concentration of lidocaine for reversal of mechanical 'allodynia' in a neuropathic pain model in the rat, defined the concentration-dependent limits of that reversal and compared the acute reversal during intravenous drug infusion with the persistent relief of allodynia assayed 48 h later. Actions of i.v. lidocaine on ipsilateral and contralateral legs were also assessed. Forty rats were sorted into five groups (n = 7-10) and underwent spinal root (L5-6) ligation to produce allodynia, as quantified by a lower force of von Frey hairs at the plantar hindpaw required to elicit paw withdrawal (PWT, paw withdrawal threshold). ⋯ Contralateral allodynia, despite its acute reversal during infusion to 2.1 microg/ml and higher, was not persistently relieved after infusion of lidocaine to any concentration. Repeated infusions to subthreshold levels (<2 microg/ml) did not provide persisting relief of allodynia on either side, and infusions of saline were impotent. These findings show that experimental allodynia results from multiple factors, only some of which are sensitive to lidocaine treatment, and that prolonged reversal of allodynia is limited in extent and likely influenced by pre-existing factors.
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Randomized Controlled Trial Comparative Study Clinical Trial
Intra-subject variability in post-operative patient-controlled analgesia (PCA): is the patient equally satisfied with morphine, pethidine and fentanyl?
Our previous study suggested that when compared between patients, morphine, pethidine and fentanyl were equally satisfactory for use in patient-controlled analgesia (PCA), although quantitative differences in their side-effect profiles were detectable. The present study evaluated whether individual patients could detect differences or express preferences for individual opioids when treated by PCA with all three in random sequence finishing with the first administered opioid. The main side effects were pruritus, nausea and vomiting. ⋯ A plethora of factors will influence how an individual patient will respond to surgery and how he/she will recover. The physiological response to opioids is one variable which appears to be influenced by this complex set of factors and in turn will affect them. The findings of this study, like that of its predecessor, suggest that morphine, pethidine and fentanyl can be used successfully in PCA and that for some patients who are responding poorly, changing the opioid may be beneficial.
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Randomized Controlled Trial Clinical Trial
Topical lidocaine patch relieves postherpetic neuralgia more effectively than a vehicle topical patch: results of an enriched enrollment study.
This study compared the efficacy of topical lidocaine patches versus vehicle (placebo) patches applied directly to the painful skin of subjects with postherpetic neuralgia (PHN) utilizing an 'enriched enrollment' study design. All subjects had been successfully treated with topical lidocaine patches on a regular basis for at least 1 month prior to study enrollment. Subjects were enrolled in a randomized, two-treatment period, vehicle-controlled, cross-over study. ⋯ No statistical difference was noted between the active and placebo treatments with regards to side effects. Thus, topical lidocaine patch provides significantly more pain relief for PHN than does a vehicle patch. Topical lidocaine patch is a novel therapy for PHN that is effective, does not cause systemic side effects, and is simple to use.