Local Anesthetics Worksheet Flashcards

1
Q

LA consists of a ____ and a _____ portion.

A

Lipophillic

hydrophilic

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2
Q

the lipophilic and hydrophilic portions of a LA are separated by a connecting:

A

hydrocarbon chain

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3
Q

LA’s are poorly soluble in

A

water

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4
Q

Because of the poor solubility in water, LA’s are marketed as water soluble:

A

Hydrochloride salts

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5
Q

hydrochloride salt solutions are acidic or alkalodic? pH?

A

Acidic

pH 6

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6
Q

hydrochloride salt solutions contribute to the LA’s what?

A

stability

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7
Q

what is it that contributes to the stability of LA’s?

A

the hydrochloride salt solutions

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8
Q

substituting a butyl group for the amine group on the benzene ring of procaine results in:

A

tetracaine

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9
Q

Tetracaine is water or lipid soluble?

A

Lipid soluble

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10
Q

Compared to procaine, tetracaine is more

A

lipid soluble

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11
Q

How many times more potent is tetracaine than procaine?

A

10 times more potent

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12
Q

Which LA has a longer duration; procaine or tetracaine?

A

tetracaine

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13
Q

the longer duration of tetracaine corresponds to a ___ fold decrease rate of _______.

A

4-5
fold decreased rate of
metabolism

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14
Q

compared to the commercially available racemic mixtures of bupivacaine and mepivacaine, what appears to be less toxic?

A

the S Enantiomers of bupivacaine and mepivacaine

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15
Q

what LA is known for cardio toxicity?

A

bupivacaine

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16
Q

the S enantiomers of Bupivacaine and mepivacaine produce less of this _____ _____ (two things) than the racemic mixtures or the R enantiomers of LA.

A

Neurotoxicity

Cardiotoxicity

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17
Q

What 2 LAs are available for clinical use as racemic mixtures (50:50) of the enantiomers:

A

Mepivacaine and bupivacaine

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18
Q

Mepivacaine, bupivacaine, ropivacaine, and levobupivacaine are all:

A

chiral drugs that may have S or R configurations

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19
Q

Name 4 LA that are chiral drugs that may have S or R configurations:

A

Mepivacaine,
bupivacaine,
ropivacaine,
levobupivacaine

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20
Q

Halogenation of procaine to _______

A

Chloroprocaine

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21
Q

Halogentation of procaine to chloroprocaine results in a ____ fold increase of what?

A

3-4 fold incease

in hyrolysis rate of chloroprocaine

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22
Q

hydrolysis of chloroprocaine is done by:

A

plasma cholinesterase

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23
Q

Etidocaine resembles:

A

Lidocaine

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24
Q

Etidocaine resembles lidocaine but has a 50 fold increase in:

A

lipid solubility

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25
Q

Etidocaine resembles lidocaine but has a 2-3 fold

A

increase in the duration of action

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26
Q

What LA is 35 times more lipid soluble than mepivacaine?

A

bupivacaine

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27
Q

Bupivacaine has a potency and DOA _____ times that of mepivacaine.

A

3-4 times

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28
Q

These drugs have been incorporated into liposomes to prolong the DOA and decrease toxicity:

A

Lidocaine, tetracaine, and bupivacaine

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29
Q

Lidocaine, tetracaine, and bupivacaine have been incorporated into liposomes to do what two things?

A

Prolong DOA

Decrease toxicity

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30
Q

The FDA has approved this for local infiltration of anesthesia for hemorrhoidectomy and bunionectomy:

A

bupivacaine extended release liposome injection

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31
Q

LAs bind to specific sites in:

A

voltage gated Na+ channels

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32
Q

Na+ channels are

A

the binding sites for LA

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33
Q

LA blocks what? (main moa)

A

Na+ current

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34
Q

LA blocks Na+ current reducing excitability of:

A

1) neuronal
2) cardiac
3) central nervous system tissue

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35
Q

LA prevents transmission of nerve impulses by inhibition passage of _______ through _______ in nerve membranes.

A

Sodium ions through ion-selective sodium channels

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36
Q

This is a specific receptor for LA molecules

A

The sodium channel itself

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37
Q

Describe how AP is not propagated d/t Na+ ion channels

A
  • -failure of Na-channel permeability to increase slows rate of depolarization.
  • Threshold potential is not reached thus,
  • AP is not propagated
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38
Q

Pregnancy may do what to LA’s?

A

Increased sensitivity

*more rapid onset of conduction blockade

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39
Q

When might there be an increased sensitivity that would generate a more rapid onset of a LA blockade?

A

pregnancy

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40
Q

Name 3 esters :

table 10-1

A

Tetracaine
Procaine
Chloroprocaine

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41
Q

Name 2 rapid onset LA:

table 10-1

A

Chloroprocaine

Lidocaine

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42
Q

Chloroprocaine and Lidocaine both have:

A

a rapid onset

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43
Q

Procaine
Chloroprocaine
Tetracaine

Are all examples of:

A

esters

*in order of potency least to greatest

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44
Q

Which LA has the greatest protein binding?

A

Levobupivacaine (>97%)

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45
Q

Levobupivacaine has the greatest what?

A

protein binding

>97%

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46
Q

LAs are all weak:

A

bases

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47
Q

at physiologic pH what % of LA exists in a lipid soluble, non-ionized form?

A

< 50%

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48
Q

What type of environment would increase the ionized fraction of the LA if injected into it?

A

Acidic (as present with tissue infection)

*Acidosis

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49
Q

If LA is injected into an infected area, more of the drug becomes ________.

This is consistent with what kind of quality (of the block)?

A

Ionized (base in an acid)

–> poor quality blockade results; not as much being absorbed in ionized form

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50
Q

What 4 characteristics of LA effect the absorption of LA from its site of injection to the systemic circulation?

A
  1. site of injection
  2. dose
  3. use of epinephrine
  4. pharmacologic characteristics of the drug
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51
Q

The ultimate plasma concentration of LA is determined by what two factors?

A
  • rate of tissue distribution
  • rate of clearance of the drug

*p.287

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52
Q

Name 3 LA the lungs are able to extract from the circulation:

A
  1. Lidocaine
  2. bupivacaine
  3. prilocaine

*amides

53
Q

Bupivacaine’s first-pass pulmonary extraction is

A

dose dependent

54
Q

This LA has a dose dependent first pass pulmonary extraction:

A

bupivacaine

55
Q

What drug impairs the extraction of bupivacaine from the lungs?

A

Propranolol

56
Q

Propranolol is known to do what with certain local anesthetics?

A
  • impair bupivacaine’s extraction by the lungs

- decrease plasma clearance of lidocaine and bupivacaine

57
Q

What decreases the plasma clearance of lidocaine and bupivacaine?

A

Propranolol

58
Q

Propranolol decreases the plasma clearance of which LA?

A

Lidocaine

bupivacaine

59
Q

D/t their rapid hydrolysis, this classification of LA are not available to cross the placenta in significant amounts:

A

Ester LA

60
Q

What causes LA molecules to accumulate in the fetus?

A

Acidosis

61
Q

What is the process of ion accumulation in the fetus called?

A

ion-trapping

62
Q

Ion trapping in a fetus, is a result of what type of environment?

A

acidosis

63
Q

Do LA’s have good/limited/poor renal excretion?

A

limited renal excretion

64
Q

Renal excretion of LA’s is limited because they are:

A

poorly water soluble

65
Q

This LA has a 10-12% unchanged drug recovery in the urine

A

Cocaine

66
Q

Less than what % of the LA is excreted in the urine unchanged?

A

< 5%

67
Q

Cocaine is the exception to what?

A

renal excretion; unlike other LA’s 10-12% of cocaine is excreted unchanged.
Also it is an ester that is metabolized in the Liver instead of plasma.

68
Q

Where are Amide LA’s primarily metabolized?

A

Liver

69
Q

Name the most rapid metabolized amide(s):

A

Prilocaine

70
Q

Name the intermediate metabolized amide(s):

A

Lidocaine

Mepivacaine

71
Q

Name the slowest metabolized amide(s):

A

Bupivacaine
Etidocaine
Ropivacaine

72
Q

What class of LA has the slower metabolism?

A

Amide

73
Q

Amides have a slower ___________ compared to esters

A

metabolism

74
Q

The principle metabolic pathway of Lidocaine is:

A

oxidative dealkylation

75
Q

oxidative dealkylation of lidocaine occurs where?

A

Liver

76
Q

Lidocaine metabolizes in the liver through oxidative dealkylation in to what?

A

monoethyglycinexylidide

77
Q

Once lidocaine goes through oxidative dealkylation to monoethyglycinexylidide, what happens next?

A

hydrolysis

78
Q

monoethyglycinexylidide hydrolyzes to this metabolite:

A

xylidide

79
Q

xylidide has what % of the cardiac protection against dysrhythmias of lidocaine?

A

10%

80
Q

Xylidide is hydrolyzed from

A

monoethyglycinexylidide

81
Q

monoethyglycinexylidide is a result of

A
  • Oxidative dealkylation of Lidocaine

- in the liver

82
Q

In liver dysfunction, elimination half-time of lidocaine is

A

increased more than fivefold

83
Q

There is more than a fivefold increase in the elimination half-time of lidocaine in patients with

A

liver dysfunction

84
Q

Prilocaine is metabolized to

A

orthotoluidine

85
Q

Prilocaine is associated with what life threatening complication?

A

methemoglobinemia

86
Q

Orthotoluidine is the byproduct of what?

A

prilocaine metabolism

87
Q

Orthotoluidine is an oxidizing compound capable of converting what?

A

hgb in to its oxidized form: methemoglobin

—> methemoglobinemia

88
Q

What is the reversal drug and dose for methemoglobinemia?

A

methlyene blue
1-2mg/kg IV over 5 mins
-do not exceed 8mg/kg

89
Q

Name the LA(s) lacking vasodilator activity:

A
  • Mepivacaine

- Ropivacaine (added)

90
Q

When adding epinephrine to a LA (in order to extend its DOA by vasoconstriction) is not recommended, what LA could you add to the mix as an alternative?

A

mepivacaine

91
Q

Compare clearance and elimination half time of ropivacaine and bupivacaine:

A

-Ropivacaine has a shorter elimination half-time and higher clearance.

92
Q

Ropivacaine has a shorter elimination half-time and higher clearance than bupivacaine. This may offer an advantage over bupivacaine in terms of :

A

systemic toxicity

93
Q

In order of greatest to least LIPID solubility:

[lidocaine, bupivacaine and ropivacaine]

A

Bupivacaine
Ropivacaine
Lidocaine

94
Q

Ropivacaine is metabolized by

A

P450

95
Q

Which LA is the slowest eliminated amide?

A

Dibucaine

96
Q

Dibucaine is known for its ability to inhibit the activity of normal:

A

butyrylcholinesterase by more than 70%

97
Q

Dibucaine inhibits butytylcholinesterase activity by how much?

A

more than 70%

98
Q

Atypical plasma cholinesterases account for prolonged effects and toxicity of drugs such as

A

succinylcholine

chloroprocaine

99
Q

What LA is used for pseudocholinesterase difficency testing?

A

dibucaine

100
Q

Cocaine undergoes metabolism where?

A

in the liver

101
Q

All ester LA’s undergo hydrolysis by

A

cholinesterase enzymes

102
Q

This ester LA is the only one that does not undergo hydrolysis by cholinestearse enzymes:

A

cocaine

103
Q

Cocaine is metabolized by

A

plasma and liver cholinesterase

104
Q

CSF contains little to no

A

cholinesterase enzyme.

105
Q

Anesthesia produced by subarachnoid placement of Tetracaine will persist until

A

the drug is absorbed by systemic circulation

106
Q

What contributes to the persistent effects of Tetracaine when injected into the CSF?

A
  • CSF has no cholinesterase enzymes

- drug must be absorbed by systemic circulation

107
Q

What is unique about benzocaine?

A

a weak acid (pka 3.5)

predominantely in non-ionized form

108
Q

How long can cocaine remain in the urine?

A

24-36hrs

1-1.5 days

109
Q

Alkalization of LA does what?

A

shortens onset of neural blockade

  • enhances depth of sensory and motor blockade
  • increases spread of epidural blockade
  • increase the % of LA in the lipid soluble form that is available to diffuse across lipid cell barriers
110
Q

The effect of the addition of epi to lidocaine and mepivacaine?

A
  • prolongs duration of conduction blockade

- decreases systemic absorption of LA (by 20-30%)

111
Q

The effect of the addition of epi to bupivacaine?

A
  • prolongs duration of conduction
  • decreases systemic absorption of LA (by 10-20%)

*slightly less than lidocaine and mepivacaine

112
Q

Most LA possess intrinsic vasodilator properties except: (choose two)

A

Ropivacaine and mepivacaine

113
Q

Ropivacaine and mepivacaine lack:

A

vasodilator properties like other LA’s

114
Q

Most likely class of LA to have an allergic reaction to?

A

Esters

-b/c of metabolite paraaminobenzoic acid

115
Q

Name the metabolite likely to evoke an allergic reaction in LAs

A

paraaminobenzoic acid

*ester metabolite

116
Q

Is there a cross sensitivity b/w esters and amides?

A

NO

-more of a reflection of a sensitivity to the metabolite paraaminobenzoic acid

117
Q

The plasma concentration of Lidocaine that causes:

ANALGESIA

A

1-5mcg/mL

118
Q

The plasma concentration of Lidocaine that causes:

MYOCARDIAL DEPRESSION

A

5-10 mcg/ml

119
Q

The plasma concentration of Lidocaine that causes:

TINNITUS

A

5-10 mcg/ml

120
Q

The plasma concentration of Lidocaine that causes:

SEIZURES

A

10-15 mcg/ml

121
Q

The plasma concentration of Lidocaine that causes:

APNEA

A

15-25 mcg/ml

122
Q

The plasma concentration of Lidocaine that causes:

CARDIOVASCULAR DEPRESSION

A

> 25 mcg/ml

123
Q

What is the recommended adult dose of lidocaine with epi for regional anesthesia:

A

7mg/kg

124
Q

In tumescent liposuction the dose of lidocaine may range from

A

35-55mg/kg

125
Q

What drug can be used to tx cocaine induced MI?

A

Nitroglycerin

126
Q

What drug class should be used with caution with a cocaine overdose?

A

beta blockers

127
Q

Beta blockers in the presence of catecholamine-induced HTN and tachycardia has been associated with:

A

profound cardiovascular collapse and cardiac arrest

128
Q

What is the drug of choice for catecholaimine-induced HTN in cocaine OD?

A

Nitroprusside

129
Q

There is evidence that Beta blockade accentuates [what] in the acute cocaine OD?

A

coronary artery vasospasm