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15 Cards in this Set
- Front
- Back
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504-2 PHARM: LOCAL ANESTHETICS
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504-2 PHARM: LOCAL ANESTHETICS
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Examples of local anesthetic drugs?
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1. procaine
2. benzocaine 3. tetracaine 4. lidocaine 5. bupivacaine |
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Physiochemical properties and metabolism of local anesthetics?
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1. weak bases with pKa 8-9
2. ester or amide |
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Ester type
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Rapidly hydrolyzed in plasma
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Amide type
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Resistant to hydrolysis
N-alklylation first then hydrolysis in liver. Extensively bound to plasma proteins, particularly to alpha-1 glycoprotein. |
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Mechanism of action of local anethetic drugs?
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1. reversibly block conduction of nerve impulses (via blocking Na channels)
2. major site of action quaternary analogs are on the INTRAcellular side of membrane. |
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What are the factors that influence the effectiveness of nerve block?
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1. size of nerve fiber: block develops faster with smaller size fiber.
2. position of nerve fiber: block is faster on fibers near to surface. 3. pKa and hydrophobicity (non-ionized) of drug. 4. inflammation: reduces pH of extracellular fluid. Inflammed tissue is more resistant to local block. 5. blood flow at site of injection: vasoconstriction can slow washout of drug. Therefore, EPI is given to prolong effect. 6. firing rate of nerve: anesthetic action increases with increasing firing rate. Therefore, block is more prominent in a partially depolarized, or rapidly firing neurons called "USE-DEPENDENT" |
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Toxicity of local anesthetics?
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1. CNS
2. heart: arryhthmias, cardiac arrest 3. blood vessel: vasodilation--> dec BP 4. allergic rxn: asthmatic rxn, anaphylactic shock |
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Procaine
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Short acting
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Benzocaine
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short acting
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Tetracaine
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Intermediate to long acting
Most toxic Used for spinal anesthesia |
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Lidocaine (xylocaine)
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More intense, longer lasting
Also used as an anti-arrhythmi |
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Bupivacaine (marcaine)
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Used for prolonged anesthesia
Produces more cardiac toxicity |
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Proparacaine
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Replaced cocaine for anesthesia of the cornea.
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Amide or Ester?
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Amide: lidocaine and bupivacaine
Ester: procaine, benzocaine, and tetracaine. |
