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52 Cards in this Set
- Front
- Back
What is the general method of action of LA?
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Nerve conduction is blocked by direct application to axon (In Na channels)
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What slows the uptake into circulation of LA?
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Vasoconstrictors (Epi)
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Are LA reversible?
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YES
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What type of molecules can cross the nerve membrane?
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uncharged
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What type of molecules interact with the Na+ channel receptor?
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Charged
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What does activity at the axoplasm occur?
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When the drug is in its ionized form
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What do LA do to the threshold?
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> it
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What nerve fibers are the most sensitive to a LA?
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high frequency or pain fibers
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What drug is used to tx cardiac disease and why?
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Lidocaine as it is a vasodilator and also slows Na channels in the heart
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As the LA becomes more lipid soluble, it is more/less potent
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More
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What maintain a receptor's sensitivity?
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PG, Thromboxane and prostacyclin
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Structurally, what 3 things make up a LA?
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aromatic ring (lipophilic/hydrophobic), ester or amide linkage and tertiary amine (hydrophilic)
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Which is metabolized in the liver, amide or ester?
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Amide
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Name 3 ester type LA
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Cocaine, Procaine, Tetracaine
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Name 2 amide type LA
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Lidocaine and Mepivacaine
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What LA is unique due to its vasoconstrictive properties?
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Cocaine
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Net lipophilic (Aromatic ring)
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Slower onset but longer duration of action (loves the receptor)
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Net Hydrophlic (Tertiary Amine)
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Faster onset, but shorter duration
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What determines the route of metabolism?
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Amide or ester
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Axoplasmic movement is proportional to what?
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Hydrophilicity (Tertiary amine)
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What is the normal ratio of ionized:un-ionized drug in the axoplasm?
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Same
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What will the pH of an infected tissue be?
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acidic
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What is the significance of acidic infected tissue and a LA?
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If pH <, > cationic form which < diffusion into nerves, thus < LA effectiveness
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What occurs in infected tissue that may shorten the duration of action?
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Vasodilation
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What allows for smaller nerve fibers to be most sensitive to LA?
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They have a larger SA:Volume ratio
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Low potency and short duration
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Procaine
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Intermediate potency and duration
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Lidocaine and mepivacaine
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High potency and long duration
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tetracaine
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Acidification of the urine would promote what?
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Drug ionization and excretion of weak bases (LA)
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What is a concern for toxicity of an ester?
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idiosyncrasy for plasma cholinesterase
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What is a concern for toxicity of an amide?
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hepatic dysfunction
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What 3 LA is epi most effective?
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Procaine, Lidocaine and mepivacaine
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What are the initial effects of a CV toxicity and LA?
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HT and tachycardia
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What are the intermediate effects of CV toxicity and LA?
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< cardiac output and HypOtension
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What is an allergy most likely to in a LA?
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ester types
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What is the concern for tissues supplied by end arteries and LA?
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gangrene (> oxygen consumption stimulated by epi or hypoxia due to vasoconstriction)
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What LA are effective topically?
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Cocaine, lidocaine and tetracaine
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What LA are effective infiltration?
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Lidocaine and procaine
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Linkage type of Procaine?
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ester
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Linkage type of Tetracaine?
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ester
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Linkage type of Cocaine?
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ester
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Linkage type of Lidocaine?
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amide
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Linkage type of mepivacaine?
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amide
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Metabolism of Procaine?
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hydrolyzed by plasmacholinesterase to PABA
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What 3 LA are detoxified by the liver?
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Tetracaine, Lidocaine and Mepivacaine
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Procaine Lipophilic or hyrophilic?
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hydrophilic
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Tetracaine Lipophilic or hyrophilic?
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Lypophilic
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Lidocaine Lipophilic or hyrophilic?
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Hydrophilic
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Mepivacaine Lipophilic or hyrophilic?
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Lypophilic
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Less potent, faster onset, shorter acting
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Hydrophilic
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Highly potent, slower onset, longer acting
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Lipophylic
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What is the LA choice for IV regional anesthesia?
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Lidocaine
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