Pharmacology - Test 2 - Local Anesthetics Flashcards Preview

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Flashcards in Pharmacology - Test 2 - Local Anesthetics Deck (26):
1

Goals for LA use

minimize local irritation.
minimize systemic toxicity.
rapid onset: high % needed
sufficient duration

2

amide metabolism

in the liver. protein binding

3

ester metabolism

plasma pseudocholinesterase

4

Mechanism of action for LA

Identical to one of the Anti convuls/epilep drug mechanisms. Block Na channels from the inside of channel. Stabilize inactived state.

5

Quartenary lidocane and nerve effects

ineffective from outside. must be injected directly into nerve.

6

Effect of block on nerve myelination and diameter.

Small and unmyelinated are most sensitive to effect.

7

Order of sensory/motor nerve block sequence

pain > cold > touch > deep pressure > motor function

8

7 factors influencing effectiveness of LA

Fiber diameter, firing rate (action potential duration - use dependent block), position of fiber in nerve bundle, local blood flow, drug size and hydrophobicity, liver function (amines). Tissue pH - consequence of inflammation

9

2 Considerations when using epinepherine in local.

Location of block (distal portion also being blocked). Slows local blood flow.

10

PkA of lidocaine

7.9

11

At more acidic pH (lidocaine)

less drug is uncharged and less drug crosses nerve membranes, and therefore less nerve block.

12

Toxicity of LA on CNS

Drowsiness, seizures (excitation), followed by general depression, coma

13

Toxicity of LA on Cardiac

Depressed pacemaker activity, decreased conduction, arrhythmias, potentiated by hperkalemia, amides synergize with anti-arrhythmic drugs to induce arrythmias

14

Toxicity of LA on vessels

vasodilation leading to hypotension (except cocaine - HTN caused by block of NE reuptake)

15

LA common allergies

esters: PABA derivatives. Amides: Preservatives

16

Most broadly used local anesthetic

lidocaine

17

Lidocaine, Amide or ester?

amide

18

Duration of lidocaine

30-60 minute, 2hr spinal

19

Toxicity of lidocaine

higher systemic toxicity than ester-linked drugs

20

Metabolism of lidocaine

metabolized by liver

21

Uses of lidocaine

spinal, epidural, local, topical anesthesia

22

Drug to be cautious of with Lidocaine

amiodarone (muscarinic antagonist)

23

Procaine, ester or amide?

esters: PABA derivatives. Amides: Preservatives

24

Toxicity of procaine

low

25

Main use of Procaine

infiltration and regional anesthesia

26

Procaine interaction

PABA blocks sulfonamide.