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what do local anesthetics do?
Stop axonal conduction by blocking Na+ channels in the axonal membrane, bringing conduction to a halt. Nonselective modifiers of neuronal function, meaning they will block action potentials in all neurons they have access to. Small, nonmyelinated neurons are blocked easier than large, myelinated neurons. These drugs can also block conduction in motor neurons
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what are the 2 types of local anesthetics and how do they differ?
Ester-type and Amide-type; differ in their methods of inactivation and promotion of allergic responses
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How do Ester-type work (local anesthetics)?
contain an ester linkage in their structure; plasma esterases rapidly convert the drug to inactive, nontoxic drugs, but it has a much greater risk of allergic responses.
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How do Amide-type work (local anesthetics) ?
they contain an amide linkage in their structure; inactivation is by hepatic metabolism and rare allergic reations occur
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What drugs are associated with Ester-type (local anesthetics) ?
procaine (injection) and cocaine (topical)
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What drugs are associated with Amide-type (local anesthetics) ?
Lidocaine (topical and injection)
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What do general anesthetics do?
they produce unconsciousness and a lask of responsiveness to all painful stimuli
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What are they 2 types of general anesthetics?
inhalation and intravenous injections
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How do inhaled general anesthetics work?
by enhacing transmission at inhibitory synapses and by depressing transmission at excitatory synapses; enhance activation of receptors for GABA, promoting generalized inhibition of the CNS; must determine the minimum alveolar concentration (MAC) to know how much to give to patient
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what are some general anesthetic drugs?
nitrous oxide, halothane, desflurane, enflurane, isoflurane, sevoflurane
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How do intravenous general anesthetics work?
they can permit dosage of inhalation anesthetic to be reduced and produce effects that cannot be achieved with an inhalation alone
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what are 3 types of intravenous general anesthetics?
short acting barbiturates, benzodiazepines and neuroleptic opiod combinations
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what are short acting intravenous general anesthetics used for?
they are employed for induction of anesthesia: example is thiopental which is highly lipid soluble and crosses the BBB rapidly
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what are benzodiazipines (general anesthetics) used for?
to produce unconsciousness and amnesia: examples include diazepam, midazolam, and lorazepam
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what are neuroleptic-opiod combinations (general anesthetics) used for?
droperidol plus fentanyl causes neuroleptic analgesia; the patient appears to be asleep but is not
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