Local Anesthetics Flashcards

(63 cards)

1
Q

Local anesthetics are weak _____ and are partially ionized at pH 7.4.

A

bases

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2
Q

What form of the anesthetic binds to the Na+ channel pore?

A

both, but the cationic form has a stronger affinity

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3
Q

How does the local anesthetic reach its binding site?

A

via the intracellular pore entrance

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4
Q

Local anesthetics have a ____ structure, typically consisting of 1. a lipophilic aromatic portion; 2. an intermediate alkyl chain; 3. a hydrophilic amine portion.

A

tripartite

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5
Q

Name the toxin:

  • one of the most potent toxins known
  • found in marine dinoflagellates (red tide)
  • binds to and blocks the extracellular entrance of voltage-gated Na+ channels –> death by paralysis of respiratory muscles
A

saxitoxin (STX)

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6
Q

What is the advantage of nerve block anesthesia?

A

large body regions can be anesthesized

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7
Q

What can local anesthetic toxicity cause?

A
  • convulsions
  • respiratory depression
  • arrhythmias
  • arterial dilation
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8
Q

When can local anesthetics reach their binding sites?

A

when the channel is open BUT they are also able to traverse the plasma membrane in the neutral form

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9
Q

Name 3 topical anesthetics.

A
  1. lidocaine
  2. tetracaine
  3. cocaine
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10
Q

How are amide local anesthetics terminated?

A

in the liver

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11
Q

Which local anesthetics are used in intravenous regional anesthesia/Bier’s Block?

A

lidocaine

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12
Q

Virtually all local anesthetics end in -_____.

A

-caine

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13
Q

Why are amide-linked local anesthetics contraindicated in pts with hepatic insufficiency?

A

the drug is only metabolized by the liver

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14
Q

Why is it important that local anesthetics are in the charged and neutral forms in the body?

A

the neutral forms can enter the cell in spite of a closed Na+ channel but the cationic form binds to the Na+ channel pore with a much higher affinity

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15
Q

Name 3 infiltration anesthetics.

A
  1. lidocaine
  2. procaine
  3. bupivacaine
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16
Q

Local anesthetics have a tripartite structure, typically consisting of 1. ______; 2. an intermediate alkyl chain; 3. a hydrophilic amine portion.

A

a lipophilic aromatic portion

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17
Q

What is a disadvantage of epidural anesthesia?

A

plasma level are high and can lead to toxicity

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18
Q

What opens Na+ channels?

A

membrane depolarization

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19
Q

What determines speed of conduction blockade in local anesthetics? Why?

A

pKa; lower pKa increases lipid solubility and tissue penetrance by increasing the fraction of local molecules that are uncharged –> enter membranes more readily

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20
Q

The intermediate chain in local anesthetics can either be an ____ or ____ moiety.

A

ester; amide

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21
Q

What determines the duration of action of local anesthetics? Why?

A

protein-binding capacity; it maintains the free concentration of anesthetic at an effective concentration for a longer period of time

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22
Q

What is use-dependent block?

A

the more the channel is open, the greater degree of local anesthetic binding and block; with more depolarization, the size of the inwards current decreases

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23
Q

What is a disadvantage of topical anesthetics?

A

the drug enters circulation

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24
Q

Name the toxin:

  • one of the most potent toxins known
  • found in Pufferfish, newts, and frogs
  • binds to and blocks the extracellular entrance of voltage-gated Na+ channels –> death by paralysis of respiratory muscles
A

tetrodotoxin (TTX)

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25
What is epidural anesthesia?
injection of local anesthetic just outside the dura of the spinal canal
26
What are the disadvantages of infiltration anesthesia?
* large doses are needed * absorption into circulation
27
What can be used as an alternative anesthetic in pts allergic to amide and ester local anesthetics?
high dose promethazine
28
Is the fractional block greater in small diameter or large diameter axons? Why is this important?
small; therefore pain sensation is the first functionality lost
29
What is EMLA cream?
a mixture of lidocaine and prilocaine that exists as an oil at room temp and can thereby penetrate the skin
30
What protein do local anesthetics bind to?
α-1 acid glycoprotein (only amide anesthetics)
31
What is infiltration anesthesia?
injection of drug into tissue w/o consideration of the underlying nerves
32
Which is the only local anesthetic that produces local vasoconstriction? How?
cocaine; it blocks NE reuptake
33
What is saxitoxin (STX)?
* one of the most potent toxins known * found in marine dinoflagellates (red tide) * binds to and blocks the extracellular entrance of voltage-gated Na+ channels --\> death by paralysis of respiratory muscles
34
Where does conduction block occur?
in smaller diameter, myelinated axons
35
Local anesthetics have a tripartite structure, typically consisting of 1. a lipophilic aromatic portion; 2. an intermediate alkyl chain; 3. \_\_\_\_\_\_.
a hydrophilic amine portion
36
What is nerve block anesthesia?
injection of a high conc of local anesthetic near a peripheral nerve or nerve plexus
37
How do local anesthetics work?
block voltage-gated Na+ channels in peripheral nerves
38
What happens in allergies to local anesthetics?
PABA is produced --\> hypersensitivity
39
Local anesthetics increase the stability of the _____ to prolong the refractory period.
inactivated state of the channel
40
In local anesthetics, the names of the _____ have a single "I" whereas the names of the _____ have two "i's."
esters = 1 I amides - 2 i's
41
Local anesthetics block conduction in small diameter, myelinated and unmyelinated axons, such as the ____ fibers that signal pain sensation.
C
42
What is intravenous regional anesthesia/Bier's Block?
when blood is squeezed out of the limb or part of the body and a tourniquet placed, followed by injection of local anesthetic via a catheter
43
This is injection of drug into tissue w/o consideration of the underlying nerves.
infiltration anesthesia
44
What is tetrodotoxin (TTX)?
* one of the most potent toxins known * found in Pufferfish, newts, and frogs * binds to and blocks the extracellular entrance of voltage-gated Na+ channels --\> death by paralysis of respiratory muscles
45
Where is the only place that blockade of APs can occur?
nodes of Ranvier
46
Local anesthetics have a tripartite structure, typically consisting of 1. a lipophilic aromatic portion; 2. \_\_\_\_\_\_; 3. a hydrophilic amine portion.
an intermediate alkyl chain
47
This is injection of a high conc of local anesthetic near a peripheral nerve or nerve plexus.
nerve block anestheisa
48
What makes a local anesthetic more potent?
higher lipid solubility
49
What is the binding site for local anesthetics?
the water-filled pore of the Na+ channel
50
What is spinal anesthesia?
injection of anesthetic into the CSF
51
What is the definition of local anesthesia?
loss of sensation in an area of the body
52
Which kinds of anesthetics have longer durations of actions?
the amides
53
Which local anesthetics are used for spinal anesthesia?
* lidocaine (short) * bupivacaine (intermediate) * tetracaine (long lasting)
54
Which vasoconstrictor often is added to local anesthetics?
epi
55
How are ester local anesthetics terminated?
they're hydrolyzed by an esterase (pseudocholinesterase) and by the liver
56
Since block is use-dependent, unblock is \_\_\_\_\_.
also use-dependent
57
Which local anesthetics are used in epidurals?
* lidocaine (short) * bupivacaine (longer) * low conc bupivacaine + fentanyl for labor
58
What does local anesthetic binding to its site cause?
physical obstruction of Na+ ion flow through the Na+ channels, preventing membrane depolarization and terminating APs
59
How come cocaine analogs are safer than cocaine?
they are unable to block catecholamine reuptake
60
Local anesthetics block ____ and ____ of nerve impulses (APs) by blocking the voltage-gated Na+ channels.
initiation; conduction
61
Name 2 nerve block anesthetics.
1. lidocaine (short duration) 2. bupivacaine (longer duration)
62
Where does excretion of local anesthetics occur?
in the kidney
63
Why are vasoconstrictors added to local anesthetics?
* to prolong duration of conduction blockade * reduce blood flow to the area (limit absorption) * prevent toxicity