Pain
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Morphine-6-glucuronide (M-6-G) is an active metabolite of morphine that may contribute to drug effects. To understand better the relationship between morphine and M-6-G in cancer patients receiving chronic therapy, we employed high performance liquid chromatography with electrochemical detection to measure: (1) morphine and M-6-G plasma concentrations following discontinuation of dosing in 2 patients, one receiving oral therapy and the other an intravenous infusion; (2) morphine and M-6-G concentrations in random blood samples taken at apparent steady state from 8 patients, 7 with normal renal function and 1 with mild renal insufficiency, who were receiving continuous morphine infusions; and (3) morphine and M-6-G concentrations in random blood samples taken over a period of weeks from 4 patients, 2 with stable and 2 with declining renal function. Results demonstrated a slightly slower decline in plasma M-6-G than morphine concentrations following drug discontinuation, as would be expected for metabolite and parent relationship; roughly similar M-6-G: morphine ratios (mean molar ratio = 1.22) across a broad range of morphine doses in patients with normal renal function; and an increase in this ratio over time in patients with progressive renal dysfunction. These data illustrate the kinetics of M-6-G in cancer patients receiving chronic morphine therapy and confirm the importance of renal function in determining the concentration of the metabolite.
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Clinical Trial Controlled Clinical Trial
Morphine differentially affects the sensory and affective pain ratings in neurogenic and idiopathic forms of pain.
In a double-blind, placebo controlled crossover study, the effect of morphine on the affective and sensory pain ratings in different forms of chronic pain was investigated. Six patients suffering from central neurogenic pain, 8 from peripheral neurogenic pain and 6 from idiopathic pain participated in the study. Morphine (0.3 mg/kg bodyweight) and placebo (saline) were administered intravenously. ⋯ From our results it appeared that morphine reduced the affective but not the sensory dimension of pain sensation in both groups of neurogenic pain patients. In the idiopathic pain group, neither the affective nor the sensory dimension of pain sensation were affected. The observed differences in opioid responsiveness were neither the result of differences in opioid consumption nor of differences in baseline pain levels.
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To determine the level of pain that acutely burned children experience, we obtained pain scores before, during and after burn dressing change (BDC). Pain scores were higher during the BDC, consistent with severe pain during this procedure. A positive correlation between pain scores and the body surface area (BSA) burned suggests that pain increases with the size of the burn. ⋯ Regardless of wide variations in patient characteristics, fixed doses of oral narcotics were usually prescribed for pain. Patients with BSA greater than 70% experienced severe pain during BDC despite the type, dose or route of opioids. These findings suggest the need for (a) education to correct the myth that 'third-degree burns don't hurt'; (b) revision of analgesic prescribing patterns in the burned child; and (c) research to determine the mechanisms (e.g., tolerance or deafferentation) underlying the opioid-resistant nature of pain after large burns.