Articles: narcotic-antagonists.
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The heat pain threshold was assessed in 32 healthy participants after a mild burn on the dorsal surface of each hand, after injection of an opioid antagonist (80 microg naloxone) or vehicle alone (0.2 mL saline) into the burnt skin of 1 hand, and after repeated painful immersion of this hand in cold water for up to 180 seconds. We hypothesized that sensitivity to heat would decrease at the burn-injured site after the immersions, due to local release of opioids into the burnt skin. Naloxone augmented cold-induced pain during the immersions in participants who tolerated the longest immersions, implying that release of endogenous opioids suppressed cold-pain. After the immersions, sensitivity to heat decreased at the burn-injured site in the immersed hand, but naloxone did not block this effect. Instead, naloxone altered sensitivity to heat in unburnt skin, implying that thermal hyperalgesia at sites of burn injury masked the modulatory effects of opioids. In particular, naloxone blocked a decrease in sensitivity to heat at an unburnt site on the contralateral hand of participants who tolerated the longest immersions, consistent with central or systemic opioid release. Naloxone reduced sensitivity to heat at unburnt sites in participants who tolerated medium-length immersions, suggesting that an increase in systemic or central opioid activity evoked thermal hyperalgesia in this group. In addition, in a small group of participants who tolerated only brief immersions, naloxone blocked decreases in sensitivity to heat at an unburnt site in the immersed hand. These findings suggest that repeated painful immersions trigger local opioid release in participants who tolerate only brief immersions, and elicit central or systemic opioid release in participants who tolerate longer immersions. ⋯ This article demonstrates that repeated immersion of the hand in painfully cold water increases opioid activity and that the increase in opioid activity exerts multiple opposing effects on sensitivity to heat. Individual differences in the response to opioids might contribute to individual differences in pain tolerance.
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The amplitude-integrated electroencephalogram (aEEG) is a useful tool to assess brain function after perinatal asphyxia in term infants. We report a full-term newborn with moderate perinatal asphyxia, who accidentally received an overdose of morphine (5000 microg/kg). The overdose of morphine resulted in a clear and immediate change of aEEG background activity from a continuous (C) to discontinuous (DC) background pattern. After administration of naloxone, the background activity restored immediately to continuous background pattern. The aEEG was used to monitor the stepwise reduction in continuous naloxone infusion. ⋯ An overdose of morphine leads to clear and immediate changes in aEEG which restore after naloxone treatment. The aEEG can be used to monitor naloxone infusion.
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J Paediatr Child Health · Dec 2007
Use of naloxone during neonatal resuscitation in Australia: compliance with published guidelines.
The aims of this study were to describe the use of naloxone during neonatal resuscitation in Australia, and to assess this against the published guidelines for use. ⋯ Despite a steady decrease in the use of naloxone for neonatal resuscitation, there is a considerable lack of compliance with published guidelines for use. Given the scant evidence supporting naloxone use during neonatal resuscitation and increasing documentation of potential deleterious effects, perhaps it is time to remove naloxone from our resuscitaires.
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Prescrire international · Dec 2007
Buprenorphine + naloxone: new combination. Opiate dependence: no proof of reduced risk of self-administered injection.
(1) Two drugs with similar efficacy are available in France for heroin replacement therapy: methadone and buprenorphine. (2) Buprenorphine is sold in the form of sublingual tablets, but some patients dissolve and inject them. Methadone is the main alternative for these patients. Other intravenous opiate derivatives can also be tried, although they have not been approved for this indication. (3) In order to help prevent patients from injecting themselves with buprenorphine, a sublingual combination of buprenorphine + naloxone is to be marketed in France. (4) From a pharmacological point of view, this combination makes sense. ⋯ However, clinical studies are needed to determine whether or not this prevents injection. (5) A double-blind trial in 326 patients compared replacement therapy with buprenorphine 16 mg + naloxone 4 mg/day versus buprenorphine 16 mg + placebo. The addition of naloxone did not reduce the efficacy of sublingual buprenorphine, but the frequency with which patients injected the drugs was not studied in this trial. (6) This combination of buprenorphine + naloxone has not been directly compared with methadone. (7) In addition to the classical adverse effects of opiates, buprenorphine can cause hepatic adverse effects. (8) Little evidence is available on the effects of intravenous injection of buprenorphine + naloxone. According to an epidemiological survey conducted in Finland, where the combination is also marketed, about 8% of patients regularly inject it intravenously. (9) Patients who are likely to inject buprenorphine should be switched to methadone.
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For thousands of years mu opioid agonists such as morphine have been utilized for their analgesic properties. Today, morphine and related compounds are still used as a first line therapy in the treatment of moderate to severe pain. However, despite the clear benefits of mu agonists in pain management, severe side effects such as dependence and respiratory depression are associated with use of these drugs. ⋯ These compounds are of special interest as they are peripherally restricted. This attribute enables treatment of peripheral side effects induced by opioid agonists without reversal of the centrally mediated analgesia of the agonist. In this article we discuss the structural classes of mu opioid antagonists, their potential clinical applications, and review the relevant patents of the last ten years.