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15 Cards in this Set

  • Front
  • Back
What is lidocaine otherwise used for?
Anti-arrythmic effects.
What do anesthetics do?
Block axonal conduction.
What are three properties of a good local anesthetic?
Non-irritant to tissues, short onset, long enough but variable duration.
What is the chemistry of local anesthetics?
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.
What are the differences between amides and 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).

2 i's in their names.
No allergen metabolic end-product.
Metabolized in hepatocytes.
What is the difference between R and S isomers in local anesthetics?
S-isomers are 40x LESS CARDIOTOXIC.

Cardiotoxicity is due to decreased myocardial conduction with vasodilation.
Local anesthetics bind what ion channel? what states?
Primarily Na channels. Preferentially bind to open/inactive states. Net effect is to inhibit axonal conduction.
What properties of local anesthetics determine their action?
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.
If patient is given anesthetic and is not responding, what is a possibility?
ACIDITY! Weak bases are neutralized, speed of onset decreases.
Anesthetic in what state can be toxic?
FREE DRUG, not protein bound
What are alpha, beta, gamma phases?
Alpha - distribution to highly perfused parts of body. FAST!

Beta - slow distribution to less perfused parts of body. SLOWER!

Gamma - Metabolism and excretion
A drug that is more lipid soluble (higher lipid:water partition coefficient) has what properties?
Drugs with pKa's further from body's pH will take longer/shorter to ONSET!
LONGER! Greater difference in pKa from pH means a higher % of drug will be IONIZED. IONIZED CAN'T CROSS MEMBRANE
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
Esters bind to what protein in plasma?