Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
A comparison of intrathecal fentanyl and sufentanil for labor analgesia.
The use of intrathecal opioids for labor analgesia continues to gain popularity, but there are limited data to guide this use. Previously, the authors established the ED50 for 60 min of labor analgesia from intrathecal sufentanil using an up-down sequential allocation study design. The current study first establishes an ED50 for intrathecal fentanyl using this same study design to establish an intrathecal potency ratio for fentanyl and sufentanil and then uses this ratio to compare the efficacy, duration of analgesia, and side effects from comparable doses of intrathecal fentanyl and sufentanil. ⋯ The relative potency of intrathecal sufentanil to fentanyl for labor analgesia is 4.4:1. When using intrathecal opioids alone for early labor analgesia, 8 microg sufentanil produces labor analgesia lasting approximately 25 min longer than from 36 microg fentanyl, without a statistically significant increase in side effects. However, when making a choice between fentanyl and sufentanil, one must consider other important factors, such as the higher cost of sufentanil and the greater risk of dosing error due to the higher potency of sufentanil compared with fentanyl.
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It has been generally considered that supraspinal morphine activates the serotonergic descending inhibitory system and releases serotonin (5-hydroxytryptamine [5-HT]) in the spinal cord, producing antinociception through activation of 5-HT receptors. The involvement of a spinal gamma-aminobutyric acid-mediated (GABAergic) system is also suggested in supraspinal morphine antinociception. It has been reported that spinal GABAergic system contributes to 5-HT3 receptor-mediated antinociception. In this study, the authors investigated the contribution of spinal 5-HT3 receptor and the GABAergic system in the intracerebroventricular morphine-induced antinociception. ⋯ Intracerebroventricular morphine evokes spinal GABA release via the activation of 5-HT3 receptors in the spinal cord, resulting in antinociceptive effect.
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This study tests the hypothesis that loss of spinal activity of gamma-aminobutyric acid (GABA) contributes to the allodynia and hyperalgesia observed after peripheral nerve injury. ⋯ Pharmacologic inhibition of intrinsic GABA tone in normal rats resulted in tactile allodynia and thermal hyperalgesia, consistent with the hypothesis being tested. Exogenous administration of GABA agonists reversed spinal nerve ligation-induced allodynia and hyperalgesia, also consistent with this hypothesis. Isoguvacine produced specific antihyperalgesic and antiallodynic effects, whereas assessment of the effects of baclofen was complicated by motor dysfunction. Spinal GABAA agonists may provide a specific therapy for neuropathic pain.
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Randomized Controlled Trial Clinical Trial
Dextromethorphan and memantine in painful diabetic neuropathy and postherpetic neuralgia: efficacy and dose-response trials.
There are few repeated dose-controlled trials of N-methyl-d-aspartate glutamate receptor antagonists in patients with neuropathic pain. The authors sought to evaluate two low-affinity N-methyl-d-aspartate antagonists using a novel two-stage design. ⋯ Dextromethorphan is effective in a dose-related fashion in selected patients with DN. This was not true of PHN, suggesting a difference in pain mechanisms. Selective approaches to pain-relevant N-methyl-d-aspartate receptors are warranted.
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Postherpetic neuralgia is pain that persists long after the disappearance of the cutaneous lesions of herpes zoster. However, the mechanisms of this delayed pain are unclear. Herpes simplex virus infection induces cutaneous lesions and pain-related responses in mice. The authors examined whether such responses would persist after the disappearance of the cutaneous lesions and whether some analgesics would be effective against them. ⋯ The authors show a mouse model of delayed postherpetic pain. This may be useful for manifesting the mechanisms of postherpetic neuralgia and the factors contributing to the transition from acute herpetic pain to delayed postherpetic pain. This may also be useful for the development of new analgesics against postherpetic neuralgia.