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Anesthesia Pharm - Spring 2025 > Local Anesthetics I (Exam IV) > Flashcards

Local Anesthetics I (Exam IV) Flashcards

1
Q

What was the first local anesthetic?

A

Cocaine

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2
Q

Is cocaine an ester or amide?

A

Cocaine is a natural ester.

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3
Q

What was cocaine first used for and what was the effect?

A

Ophthalmology (1884)

Local vasoconstriction: shrinks the nasal mucosa.

cerebral stimulating qualities (sniff sniff)

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4
Q

What was the first synthetic ester developed in 1905?

A

Procaine

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5
Q

What was the first synthetic amide developed in 1943?

A

Lidocaine

Gold Standard

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6
Q

What are the uses for Local Anesthetics (LAs)?

A
  • Treat dysrhythmias
  • Analgesia: Acute and chronic pain
  • Anesthesia- ANS Blockade, Sensory Anesthesia, Skeletal Muscle Paralysis
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7
Q

What antiarrhythmic Drug Class is lidocaine in?

A

Class I: Sodium Channel Blockers

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8
Q

MAGA: What is the intra-op infusion dose of lidocaine?

A

1 mg/kg over 1 hour

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9
Q

What is the IV dose of Lidocaine?

A
  • 1 to 2 mg/kg IV (initial bolus) over 2 - 4 min.
  • 1 to 2 mg/kg/hour (drip)
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10
Q

When should lidocaine be terminated?

A

Terminate within 12 - 72 hours

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11
Q

What should we monitor with lidocaine?

A

Careful monitoring: cardiac, hepatic, & renal dysfunction.

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12
Q

Dose Dependent Effects of Lidocaine if plasma lidocaine concentration is 1-5 mcg/ml.

A

Analgesia

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13
Q

Dose Dependent Effects of Lidocaine if plasma lidocaine concentration is 5-10 mcg/ml.

A
  • Circum-oral numbness
  • Tinnitus
  • Skeletal muscle twitching
  • Systemic hypotension
  • Myocardial depression
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14
Q

Dose Dependent Effects of Lidocaine if plasma lidocaine concentration is 10-15 mcg/ml.

A
  • Seizures
  • Unconsciousness
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15
Q

Dose Dependent Effects of Lidocaine if plasma lidocaine concentration is 15-25 mcg/ml.

A
  • Apnea
  • Coma
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16
Q

Dose Dependent Effects of Lidocaine if plasma lidocaine concentration is >25 mcg/ml.

A
  • Cardiovascular Depression
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17
Q

Describe the components that make up the molecular structure of lidocaine.

A

Has Lipophilic Portion (Aromatic Section) connected by Hydrocarbon Chain to the Hydrophilic (Amino Group)

Bond between the lipophilic portion and the hydrocarbon chain will determine if LA is an ester or an amide.

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18
Q

What structural component of a LA determines if it is an ester or an amide?

A

Bond between the lipophilic portion and the hydrocarbon chain will determine if LA is an ester or an amide.

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19
Q

What type of local anesthetic would you anticipate from the figure below?

A

Ester due to the ester bond between the aromatic and the intermediate chain

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20
Q

What type of local anesthetic would you anticipate from the figure below?

A

Amide due to the amide bond between the aromatic and the intermediate chain

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21
Q

Local anesthetics will typically have a pH of _____ and are weak _______. ?

A

pH of 6 (HCl salts) ; weak bases

A majority of LA are weak bases

  • Epinephrin & sodium bisulfite
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22
Q

Increased potency generally correlates to increased __________.

A

duration

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23
Q

Which ester is the most potent?

A

Tetracaine

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24
Q

Which local anesthetics will exhibit the highest degree of protein binding?

A
  • Bupivacaine
  • Levobupivacaine
  • Ropivacaine
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25
Q

Which two local anesthetics will have the most rapid onset?

A

Chloroprocaine
Lidocaine

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26
Q

Which 3 LA will have the highest protein binding?

A

Levobupivacaine (>97%)
Bupivacaine (95%)
Ropivacaine (94%)

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27
Q

Lipid solubility correlates to _______ of the drug.

Which LA has the highest lipid solubility?

A
  • potency
  • Tetracaine
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28
Q

pK values closer to a pH of ___________ will have the fastest onset of action.

A

7.35 - 7.45

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29
Q

Which three local anesthetics have pK values closest to 7.35-7.45 ?

A
  • Lidocaine (pK = 7.9)
  • Prilocaine (pK = 7.9)
  • Mepivacaine (pK = 7.6)
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30
Q

Which ester has the greatest degree of lipid solubility?

A

Tetracaine

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31
Q

Which amide has the greatest degree of lipid solubility?

A

Bupivacaine

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32
Q

What are some liposomes?

A

lidocaine, tetracaine, and bupivacaine.

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33
Q

How do liposomes and local anesthetics interact?
What is the result?

A
  • Liposomes unload LA’s into tissue at a controlled rate.
  • Prolonged duration of action & decreased toxicity
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34
Q

The FDA released this local anesthetic that contains liposomes and can last up to 96 hours.

A

Exparel ER (Bupivacaine)

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35
Q

What is the mechanism of action of Local Anesthetics?

A
  • Binds to voltage-gated Na+ channels
  • Block/inhibit Na+ passage in nerve membranes, causing no action potential in the cell.

LA must be non-ionized and lipid-soluble to go through the cell membrane and block the Na+ gated channel from within the cell.

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36
Q

What two things will cause a local anesthetic to not work anymore?

A

Becoming water-soluble and ionized.

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37
Q

What factors affect the degree of blockade seen from local anesthetics?

A
  • Lipid solubility or non-ionized form
  • Repetitively stimulated nerve (↑ sensitivity)
  • Diameter of the nerve (↑ diameter, ↑ LA need)
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38
Q

What happens when you expose LA (a weak base) to an acidic environment?

A

LA becomes ionized.

When LA becomes ionized, it will not cross cell membrane to block Na+ gated channels.

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39
Q

What other receptors can be targeted by local anesthetics besides sodium channels?

A
  • Potassium channels
  • Calcium Ion Channels
  • G protein-coupled receptors
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40
Q

Minimum Effective Concentration or Cm (LAs) = _________ (Volatile Agents)

A

MAC

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41
Q

What component of the local anesthetic is required for the conduction block?

A

Non-ionized form (equates with lipid solubility)

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42
Q

Larger fibers need _____ concentrations of LAs.

A

higher

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43
Q

The diameter of motor nerve is how many times larger than the diameter of the sensory nerve.

44
Q

How many nodes of Ranvier need to be blocked to equate to 1 cm of local anesthesia?

A

At least 2, preferably 3 Nodes of Ranvier to prevent the conduction (Minimum Effect Concentration)

45
Q

If a LA were given intravascularly, which fibers would be affected the fastest?

What signs and symptoms would you see?

A

Pre-ganglionic B fibers (SNS)

Hypotension and bradycardia

46
Q

What fibers are blocked if the patient can’t tell if they are being poked by a sharp needle?

A
  • Myelinated A (medium) and B fibers (faster)
47
Q

What nerve types are typically affected when pain & temperature are affected?

What sensations are the last to be affected?

A
  • Myelinated A-δ and unmyelinated C-fibers
  • touch/pressure & Proprioception & Motor
48
Q

Place in order the fibers that are affected first to last when administering a local anesthetic.

A
  1. Preganglionic B fibers
  2. Alpha-myelinated fibers and Beta fibers
  3. Myelinated A-δ and unmyelinated C-fibers
49
Q

Which patient population will have increased sensitivity?

50
Q

pKa values closer to physiologic pH result in a _____ rapid onset

51
Q

Because the pKA of LA’s are 8, less than ______% of the drug is in lipid-soluble nonionized form.

52
Q

If a LA has vasodilator activity, what happens to its potency?

What happens to the duration of action?

A

LA is less potent

↓ Duration of action

53
Q

Because Lidocaine is a vasodilator, it will have ________ systemic absorption.

54
Q

Because Lidocaine has vasodilator activity, there is (greater/less) _______ systemic absorption. Resulting in a (shorter/longer) ________ duration of action at the site of injection.

A
  • greater
  • shorter
55
Q

Factors that influence the absorption of LA. (pharmacokinetics)

A
  • Site of injection
  • Dosage
  • Epinephrine use
  • Pharmacologic characteristics of the drug
56
Q

List the uptake of Local Anesthetics Based on Regional Anesthesia Technique from the highest blood concentration to the lowest blood concentration.

57
Q

________is the primary determinant of potency

A

Lipid solubility

58
Q

The rate of clearance is dependent on what two factors?

A
  • Cardiac output
  • Protein binding:

Note: % bound is inversely related to % plasma.

(40% albumin-bound means 60% will float freely in plasma.)

59
Q

Which LA will metabolize the fastest?

A

Chloroprocaine > Procaine d/t the smallest % of protein binding.

60
Q

Which amides will metabolize the slowest?

A
  • Bupivacaine
  • Levobupivacaine
  • Ropivacaine
61
Q

Which Amide is most rapidly metabolized?

A

Prilocaine (lowest protein binding)

62
Q

Which Amides exhibit intermediate metabolism?

A
  • Lidocaine
  • Mepivacaine
63
Q

Which Amides exhibit the slowest metabolism?

A
  • Bupivacaine
  • Ropivacaine
64
Q

How are esters metabolized?

A

Hydrolyzed by cholinesterases in plasma > liver

65
Q

Cocaine, being an ester, is primarily metabolized via plasma cholinesterases. T/F?

A

False. Primarily hydrolyzed by liver cholinesterases > plasma cholinesterases. All other esters hydrolyzed by plasma > liver

66
Q

What is the metabolite of esters?

What is the significance of this metabolite?

A
  • ParaAminoBenzoic acid (PABA)
  • Common cause of Allergies
67
Q

Is there cross-sensitivity between an amide allergy to an ester allergy?

68
Q

Are amides or esters, generally slower at metabolizing?

A

Amides are slower at metabolism.

(CYP450s instead of plasma cholinesterases)

69
Q

What are the most common LAs that have first-pass pulmonary extraction?

A
  • Lidocaine
  • Bupivacaine (dose dependent)
  • Prilocaine
70
Q

The poor water solubility of local anesthetics usually limits renal excretion of unchanged drug to less than ______%

The exception is ______, of which 10% to 12% of unchanged drug can be recovered in urine.

Water-soluble metabolites of local anesthetics, such as _______ resulting from metabolism of ester local anesthetics, are readily excreted in urine.

A

The poor water solubility of local anesthetics usually limits renal excretion of unchanged drug to less than 5%

The exception is cocaine, of which 10% to 12% of unchanged drug can be recovered in urine.

Water-soluble metabolites of local anesthetics, such as PABA resulting from metabolism of ester local anesthetics, are readily excreted in urine.

71
Q

In general, the more lipid soluble the local anesthetic is, the greater the potency. T/F

72
Q

Which local anesthetic property is most important regarding the duration of action?

A

Lipid Solubility (most important)

73
Q

Place the three factors below in order of importance for affecting duration of action?

  • Protein Binding
  • Clearance
  • Lipophilicity
A
  1. Lipid Solubility (most important)
  2. Clearance
  3. Protein binding
74
Q

What are the considerations for pregnancy and local anesthetics?

A

Lower levels of plasma cholinesterases in pregnant patients.

Caution with LA that are esters, bigger impact with normal doses

Ester LAs are still given to pregnant women because the effects of the amide LAs are detrimental to the fetus.

75
Q

What classification of LAs is more likely to cause ion trapping thus affecting fetal health?

A

Amides

Ion trapping will lead to LA toxicity in the placenta.

76
Q

What is ion trapping?

A

The pH in the fetal environment is more acidic than in maternal circulation.

77
Q

If there is ion trapping in the placenta, what can be given to adjust the pH?

A

Sodium Bicarb

78
Q

Bupivacaine
Protein Bound:
Arterial Concentration:

A

Bupivacaine
Protein Bound: 95%
Arterial Concentration: 0.32

79
Q

Lidocaine
Protein Bound :
Arterial Concentration:

A

Lidocaine
Protein Bound: 70%
Arterial Concentration: 0.73

80
Q

Prilocaine
Protein Bound:
Arterial Concentration:

A

Prilocaine
Protein Bound: 55%
Arterial Concentration: 0.85

81
Q

How is lidocaine metabolized?

A

First, oxidative dealkylation in the liver, and then hydrolysis.

82
Q

What is the major metabolite of lidocaine?

What will affect this process?

A

Xylidide

  • hepatic diesease will affect metabolism and elimination.
83
Q

What is Lidocaine’s max infiltration dose?

A
  • 300 mg solo
  • 500 mg with epi
84
Q

Lidocaine will have prolonged clearance with ______

A

Pregnancy Induced Hypertension

85
Q

What is prilocaine’s primary metabolite?

What is the issue with this metabolite?

A

Metabolite: Orthotoluidine

The metabolite converts Hemoglobin to Methemoglobin, resulting in Methemoglobinemia.

86
Q

What is the result of Methemoglobinemia?

A

Fe3+ (ferric iron) is not capable of carrying O2

Cyanosis

87
Q

What is the max dose of prilocaine?

88
Q

What is the treatment for methemoglobinemia secondary to prilocaine overdose?

A

Methylene Blue

  • 1 to 2 mg/kg IV over 5 mins (initial dose)
  • Total dose not to exceed 8 mg/kg (over 24 hours)
89
Q

Mepivacaine is similar to Lidocaine except:

A
  • Longer duration of action
  • Lacks vasodilator activity
90
Q

Can Mepivacaine be given in pregnant patients?

A

No. Prolonged elimination in fetus

91
Q

What plasma protein does Bupivacaine bind to?

A

95% bound to α1-Acid glycoprotein

92
Q

What is the metabolism of Bupivacaine?

A

metabolism: aromatic hydroxylation, N-dealkylation, amide hydrolysis, and conjugation.

93
Q

Ropivacaine
Metabolism:

Metabolite:

Protein Binding:

A

Ropivacaine
Metabolism: Hepatic cytochrome P450 enzymes

Metabolites: Can accumulate with uremic patients
Lesser system toxicity than Bupivacaine

Protein Binding: α1-acid glycoprotein

94
Q

Dibucaine
Metabolism:
MOA:

A

Dibucaine
Metabolism: Liver
MOA: inhibits the activity of normal butyrylcholinesterase (plasma cholinesterase) by more than 70%

95
Q

What is procaine’s primary metabolite?

A

PABA; excreted unchanged in urine.

96
Q

Tetracaine metabolism is slower than ______

97
Q

Chloroprocaine: Metabolism and pregnancy considerations?

A

Metabolism: Plasma cholinesterase (3.5x faster)

Pregnancy decreased plasma cholinesterase by 40%

98
Q

Which of the following local anesthetics will have the highest rate of metabolism?

Procaine
Chloroprocaine
Tetracaine

A

Chloroprocaine (fastest level of metabolism) > procaine > tetracaine (slowest)

99
Q

What is Benzocaine used for?

What procedures do we use benzocaine for?

A

Uses: Topical anesthesia of mucous membranes.

  • TEE, endoscopy, tracheal intubation, bronchoscopy.
100
Q

Overdose of Benzocaine can lead to ________.

A

OD of Benzocaine can lead to Methemoglobinemia

101
Q

What makes Benzocaine unique?

A

Weak acid instead of a weak base, like most LA.
pKa = 3.5

102
Q

Benzocaine: onset, duration, and dose?

A

onset: rapid
Duration: 30 to 60 mins
Dose: brief spray (20%) = 200 to 300 mg

103
Q

How is cocaine metabolized?

Who should receive decreased amounts of cocaine?

A

Metabolized by liver & plasma cholinesterase

Decrease cocaine use in parturients, neonates, the elderly, and severe hepatic disease.

104
Q

When should one be cautious when administering cocaine?

A

Cocaine can cause coronary vasospasm, ventricular dysrhythmias, HTN, tachycardia, and CAD.

105
Q

Cocaine: elimination?

A

Urine (24 to 36 hrs)

106
Q

Cocaine: peak & duration?

A

Peak: 30 to 45 mins

Duration: 60 minutes after peak.

Anesthesia Pharm - Spring 2025 (20 decks)

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