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15 Cards in this Set
- Front
- Back
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What is lidocaine otherwise used for?
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Anti-arrythmic effects.
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What do anesthetics do?
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Block axonal conduction.
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What are three properties of a good local anesthetic?
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Non-irritant to tissues, short onset, long enough but variable duration.
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What is the chemistry of local anesthetics?
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WEAK BASES, three components. LIPOPHILIC AROMATIC RING, intermediate bond, TERTIARY AMINES.
Higher lipid solubility means higher potency and longer duration (get stuck in nerve membrane). Easier to penetrate nerve bilayer. |
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What are the differences between amides and esters??
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Esters:
Have 1 i in their names (cocaine) PABA is allergen, metabolic end-product. Metabolized in the blood by pseudocholinesterase. Ester group at intermediate chain (cleaved during metabolism). AMIDES: 2 i's in their names. No allergen metabolic end-product. Metabolized in hepatocytes. |
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What is the difference between R and S isomers in local anesthetics?
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S-isomers are 40x LESS CARDIOTOXIC.
Cardiotoxicity is due to decreased myocardial conduction with vasodilation. |
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Local anesthetics bind what ion channel? what states?
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Primarily Na channels. Preferentially bind to open/inactive states. Net effect is to inhibit axonal conduction.
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What properties of local anesthetics determine their action?
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Lipid solubility (potency b/c enters nerve membrane easier and duration b/c gets stuck in nerve membrane).
Speed of onset. Determined by pKa. Closer pKa to body pH has faster onset. Major amount of anesthetic exists in UNCHARGED form, crosses membrane easier. |
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If patient is given anesthetic and is not responding, what is a possibility?
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ACIDITY! Weak bases are neutralized, speed of onset decreases.
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Anesthetic in what state can be toxic?
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FREE DRUG, not protein bound
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What are alpha, beta, gamma phases?
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Alpha - distribution to highly perfused parts of body. FAST!
Beta - slow distribution to less perfused parts of body. SLOWER! Gamma - Metabolism and excretion |
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A drug that is more lipid soluble (higher lipid:water partition coefficient) has what properties?
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GREATER POTENCY AND GREATER DURATION (LONGER HALF-LIFE B/C LESS EASILY REMOVED FROM NERVE MEMBRANES)
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Drugs with pKa's further from body's pH will take longer/shorter to ONSET!
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LONGER! Greater difference in pKa from pH means a higher % of drug will be IONIZED. IONIZED CAN'T CROSS MEMBRANE
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How do you treat cardiotoxicity?
What are other toxicities? |
Lipid infusion into blood. Lipid-soluble anesthetics more easily removed from organs.
CNS toxicity comes first (EXCEPT BUPIVICAINE) - metallic taste, lightheaded |
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Esters bind to what protein in plasma?
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ALBUMIN
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