Articles: anesthetics.
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Biophysical journal · Jul 1984
Mechanisms of use-dependent block of sodium channels in excitable membranes by local anesthetics.
Many local anesthetics promote reduction in sodium current during repetitive stimulation of excitable membranes. Use-, frequency-, and voltage-dependent responses describe patterns of peak INa when pulse width, pulse frequency, and pulse amplitude are varied. Such responses can be viewed as reflecting voltage-sensitive shifts in equilibrium between conducting, unblocked channels and nonconducting, blocked channels. ⋯ We develop analytical expressions characterizing guarded receptors as "apparently" variable-affinity binding sites and predicting shifts in "apparent" channel inactivation in the hyperpolarizing direction. These results were confirmed with computer simulations. Furthermore, these results are in quantitative agreement with recent investigations of lidocaine binding in cardiac sodium channels.
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Studies with an emulsion formulation of ICI 35 868 (2,6- diisopropylphenol ) indicate that this new formulation has anaesthetic properties in rats and mice, and haemodynamic effects in the mini-pig which are similar to those of the previously available Cremophor formulation. Administration of the emulsion formulation to dogs produced no untoward effect, whereas the Cremophor formulation produced a marked increase in plasma histamine concentration. In the mini-pig, no adverse response was produced by the repeated administration of the emulsion formulation of ICI 35 868, whereas the Cremophor formulation produced anaphylactoid responses when a second injection was given 1 week after an uneventful first exposure to this formulation. Behavioural responses in the rat suggest that the emulsion formulation may produce less discomfort on i.v. injection.
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A 2-month-old infant developed severe methemoglobinemia following topical pharyngeal application of a common benzocaine containing agent ( Cetacaine ). Although a number of reports of this complication have appeared in recent years, this is apparently the first case reported in the Otolaryngology literature. The pathophysiology, pharmacology, and treatment of this condition are reviewed.
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We treated 72 patients, referred to a pain clinic for acute herpes zoster neuralgia, with local anesthetics administered by nerve block and infiltration. Only those patients with severe pain initially proved to be at risk for the development of chronic postherpetic neuralgia (defined as pain in the involved dermatomes lasting at least six months). Although local anesthetic injections effectively relieved the acute pain of active herpes zoster, they did not prevent the development of chronic postherpetic neuralgia.
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Can. J. Physiol. Pharmacol. · Jun 1984
Comparative StudyComparison of the effects of Althesin, chloralose-urethane, urethane, and pentobarbital on mammalian physiologic responses.
Physiological responses to anesthetic doses of four chemically dissimilar agents, namely, Althesin, urethane, chloralose-urethane, and pentobarbital sodium were compared in rats. The tail-flick test revealed Althesin had greater antinociceptive potency than urethane, chloralose-urethane, and pentobarbital, but its duration of action was shorter than that of chloralose-urethane. ⋯ It is concluded that Althesin is a suitable anesthetic for short-term surgery and for studies of body temperature, heart rate, and mean arterial pressure. Because release of gonadotropin-releasing hormone into hypophysial portal blood can be observed under Althesin but is suppressed or blocked by chloralose-urethane, urethane, and pentobarbital, Althesin is the anesthetic of choice in studies concerned with the neural control of ovulatory hormone release.