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D1 Spring > Pharmacology - Local Anesthetics (Exam 3) > Flashcards

Pharmacology - Local Anesthetics (Exam 3) Flashcards

1
Q

Agents used to block pain sensation; absence or loss of sensation in a circumscribed area of the body

A

Local anesthetics

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2
Q

Local anesthetics depress _________ of nerve potentials and inhibit ___________ process in peripheral nerves

A

excitation; conduction

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3
Q

T/F local anesthetics can act on any part of the nervous system and on every type of nerve fibers by reversibly blocking the action potentials responsible for nerve conduction

A

True

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4
Q

Aqueous solutions, sprays, ointments, or gels for topical penetration

A

Topical anesthesia

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5
Q

Inject through skin using an electrical current

A

Inotophoresis

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6
Q

Inject directly into the area being anesthetized

A

Infiltration anesthesia

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7
Q

Inject closer to a larger terminal nerve branch; subcutaneous or submucosal

A

Field block anesthesia

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8
Q

Inject close to nerve trunk, but proximal to intended area of anesthesia

A

Nerve block anesthesia

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9
Q

Mechanism of action of local anesthetics

A

Reversible block of peripheral nerve conduction by inhibiting movement of nerve impulse

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10
Q

What 4 things can local anesthetic act on?

A

Fibers
Sensory endings
Myoneural junctions
Synapses

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11
Q

What prevents the local current from flowing across the membrane?

A

Myelin sheath

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12
Q

What does the current travel down?

A

Nodes of Ranvier

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13
Q

What has a high concentration of ion channels?

A

Nodes of Ranvier

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14
Q

What term describes an action potential jumping along the nerve fiber?

A

Saltatory conduction

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15
Q

Depolarization

A

Voltage gated Na+ channel opens

(- outside, + inside)

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15
Q

Resting potential

A

Na+/K+ pump

(+ outside, - inside)

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16
Q

Repolarization

A

Voltage gated K+ channel opens

(+ outside, - inside)

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17
Q

What 2 things allow peripheral nerve conduction to occur?

A
  1. Concentration of electrolytes in ECF and axoplasm
  2. Selective permeability of membrane to Na+ and K+ channels
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18
Q

What do local anesthetics bind to in order to block the generation/conduction of action potentials?

A

Voltage gated Na+ channels

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19
Q

What region does local anesthetic bind to? Where is this located?

A

Inactivation region, located between alpha subunits III and IV

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20
Q

What are the properties of local anesthetic? (8 things)

A
  1. Compatible w/ tissue
  2. Reversible
  3. Absence of local and systemic rxns
  4. Absence of allergic rxns
  5. Potent (high solubility)
  6. Rapid onset
  7. Effective in low doses far below toxic level
  8. Sufficient duration of action for procedure
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21
Q

What are the 2 types of local anesthetics?

A

Esters
Amides

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22
Q

First group of LA, commonly used topically

A

Esters

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23
Q

What are ester LAs metabolized to?

A

Para-amino benzoic acid (PABA)

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24
Q

What has the highest association of allergic reactions to LA?

A

Para-amino benzoic acid (PABA)

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25
Q

What are ester LAs metabolized in the tissue by?

A

Pseudocholinesterase

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26
Q

Allergic reactions are extremely rare in which type of LA?

A

Amides

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27
Q

Where are amide LAs metabolized and eliminated?

A

Metabolized: in liver
Eliminated: through kidneys

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28
Q

Which LA has better lipid solubility, potency, duration of action, and ionization constant?

A

Amides

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29
Q

What do amide LAs bind to?

A

Plasma proteins
RBCs

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30
Q

Where are amide LAs distributed to?

A

All tissue types

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31
Q

Which 2 factors affect LA properties?

A

Lipophilicity
Hydrophilicity

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32
Q

The aromatic residue is _________

A

lipophilic

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33
Q

The amino terminus is _________

A

hydrophilic

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34
Q

Which factor is essential for the drug to permeate the nerve sheath and nerve membrane?

A

Lipophilicity

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35
Q

_________ drugs gain access by crossing hydrophobic route (lipid bilayer/hydrophobic domains of Na+ channels)

A

Lipophilic

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36
Q

Which factor allows drugs to be dissolved in aqueous solutions and prevents the drug from precipitating in interstitial fluids?

A

Hydrophilicity

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37
Q

__________ drugs can access site of action via the aqueous route within Na+ channels?

A

Hydrophilic

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38
Q

What is the pH of the lipophilic region of LA?

A

7.4 - alkaline

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39
Q

What is the pH of the hydrophilic region of LA?

A

4.5-6 - acidic

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40
Q

Which region is uncharged and non-ionized?

A

Lipophilic

41
Q

Which region is a free-base?

A

Lipophilic

42
Q

Which region is unstable?

A

Lipophilic

43
Q

Which region is a charged cation?

A

Hydrophilic

44
Q

Which region is stable?

A

Hydrophilic

45
Q

LA agents in solution are ______ _______ in equilibrium between the nonionized (free base) and ionized (protonated) forms

A

weak bases

46
Q

What is the proportion of drug in each form (nonionized/ionized) dictated by?

A

pKa and pH

47
Q

Acid dissociation or equilibrium constant for the reaction

A

Ka

48
Q

pH at which non-ionized and ionized forms of LA are =

A

pKa

49
Q

What can the pKa of LA be affected by?

A

pH of tissue

50
Q

Inflamed tissue tends to be more ________ (basic/acidic), which can ionize the LA and prevent __________ into the nerve

A

acidic; absorption

51
Q

What term defines site of injection and uptake of LA?

A

Absorption

52
Q

What 6 things are involved with absorption?

A

Route
Dose
Potency
Hydrophilic vs lipophilic
pH
Reduce systemic absorption and toxicity

53
Q

System absorption is ________, especially with _________

A

greater; inflammation

54
Q

What does the addition of vasoconstrictors to LA cause? (3 things)

A
  1. Decreased systemic absorption and risk of toxicity
  2. Increased duration of action and depth of anesthesia
  3. Decreased bleeding
55
Q

What do you have to watch out for when using LA with a vasoconstrictor?

A

Cardiovascular effects in patients with uncontrolled cardiac history

56
Q

What are 2 examples of vasoconstrictors used with LA?

A

Epinephrine
Levonordefrin

57
Q

What does the selection of a vasoconstrictor depend on? (3 things)

A
  1. Length of procedure
  2. Requirement for post-op pain control
  3. Medical status of pt
58
Q

What are the typical ratios of epinephrine in LA in dentistry?

A

1:50,000
1:100,000
1:200,000

59
Q

What term defines lipid solubility and protein binding?

A

Distribution

60
Q

Highly vascular organs receive ________ concentration of anesthetics

A

higher

61
Q

What dictates the potency of LA?

A

Lipid solubility (free base)

62
Q

What is the duration of action of LA strongly dependent on?

A

Protein binding

63
Q

What term is defined by metabolism and excretion?

A

Elimination

64
Q

How are ester LAs metabolized?

A

Plasma pseudocholinesterase
Liver esterase

65
Q

How are amide LAs metabolized?

A

Hepatic metabolism

66
Q

Which drug has:

pKa: 8.9
Onset: 2-5 mins (moderate)
T1/2: 40 seconds
Duration: 60 mins (short)
Metabolism: plasma esterases
Adverse rxns: allergy
Low potency, not used in dentistry today

A

Procaine (Novocaine)

67
Q

Which drug has:

pKa: 2.78
Onset: <1 min
T1/2: 162-210 mins
Duration: 5-10 mins
Formulations: 20% conc, gel, topical
Adverse rxn: methemoglobinemia, contraindicated in children under 2
Poor water solubility

A

Benzocaine (Orajel)

68
Q

Which drug has:

pKa: 8.4
Onset: 5-10 mins (moderate)
T1/2: 5.2 hrs
Duration: 2-3 hrs
Formulations: nasal spray
Adverse rxns: contact dermatitis, burning, stinging, angioderma
High potency

A

Tetracaine

69
Q

Which drug has:

pKa: 7.8
Dose: w/ and w/o epi
Onset: 2-3 mins (fast)
T1/2: 80-96 mins
Duration: alone: 40-100 mins; w/ epi: 170-190 mins
Formulations: injections, ointment, spray
Adverse rxns: sedation, hypotension, headache, shivering
Moderate potency
Infiltration, block, and surface anesthesia

A

Lidocaine

70
Q

Which drug has:

pKa: 7.7
Dose: 6.6mg/kg
Onset: 1.5-2 mins (fast)
T1/2: 114 mins
Duration: alone: 30-160 mins; w/ levonordefrin: 60-190 mins (moderate)
Formulations: plain or w/ levonordefrin
Adverse rxns: dizziness, tremors, blurred vision
Moderate potency
Not topical
Infiltration or block anesthesia

A

Mepivacaine

71
Q

When is Mepivacaine plain used?

A

When avoiding vasoconstrictors

72
Q

Which drug has:

pKa: 7.7
Dose: 8 mg/kg
Onset: 2-4 mins (fast)
T1/2: 93-96 mins
Duration: alone: 30-170 mins; w/ epi: 90-205 mins (moderate)
Formulations: w/ or w/o epi
Adverse rxns: paresthesia; methemoglobinemia
Moderate potency

A

Prilocaine

73
Q

Which drug has:

pKa: 8.1
Dose: 2 mg/kg
Onset: 6-10 mins (moderate)
T1/2: 162-210 mins
Duration: 340-440 mins (long)
Formulations: w/ epi
Adverse rxns: increased risk of post-op injury; higher cardiovascular toxicity
High potency (higher affinity for Na+ channels)
Helps with pain post-op (bc of prolonged duration)

A

Bupivacaine

74
Q

Which drug has:

pKa: 8.1
Dose: 7.5-15 mg
Onset: 3-15 mins (moderate)
T1/2: 3-7 hrs
Duration: 0.5-8 hrs (long)
Formulations: 0.5% or 0.75%
Adverse rxns: hypotension, nausea, vomiting, bradycardia
High potency
Not available as dental cartridge

A

Ropivacaine

75
Q

Which drug has:

pKa: 7.8
Dose: toxic dose 7mg/kg
Onset: 2-3 mins (fast)
T1/2: 30-146 mins (majority metabolized in blood)
Duration: 180-230 mins (moderate)
Formulations: w/ epi
Adverse rxns: paresthesia; methemoglobinemia
Moderate potency

A

Articaine

76
Q

Which drug has:

pKa: 9
Onset: 2-10 mins (moderate)
Duration: 30-60 mins
Formulations: topical
Adverse rxns: CVS and CNS similar to those of other local anesthetics
Slight irritation and sting when applied
No cross-reactivity with other LAs

A

Dyclonine

77
Q

Reaction due to insertion of the needle

A

Psychogenic rxn

78
Q

What are the psychogenic reactions?

A
  1. vasovagal
  2. hyperventilation
  3. anaphylactoid rxn
79
Q

What reactions are involved with vasovagal?

A

Syncope
Fainting
Bradycardia
Hypotension

80
Q

Name the things involved with idiosyncratic reactions (6 things)

A

Toxic rxn at small dose
Anxiety induced
Associated w/ vasoconstrictor
Accidental IV injection
Sulfite in vasoconstrictor containing solutions
Ingested, inhaled, and spray formulations in pts with asthma

81
Q

T/F allergic rxns to LA are rare

A

True

82
Q

What happens when someone is having an allergic rxn to LA?

A

Rash to anaphylactic shock

83
Q

T/F there is no confirmed allergic rxns in the amide group of LAs

A

True

84
Q

T/F there most common allergic rxns are in the ester group of LAs due to production of PABA

A

True

85
Q

What is LA toxicity directly related to?

A

Rate of LA absorption and elimination

86
Q

What can cause LA toxicity?

A

Administration of too much LA
Administration to sensitive individuals
Administration in a blood vessel
Drug interactions

87
Q

What are the 2 main systems affected by LA?

A

CNS
CVS (cardiovascular system)

88
Q

What is the most common form of LA toxicity?

A

CNS toxicity

89
Q

What are the symptoms of CNS toxicity?

A

Sedation
Lightheaded
Slurred speech
Drowsiness
Euphoria/dysphoria
Diplopia
Sensory disturbances
Muscle twitching/seizures

90
Q

What are the symptoms of CVS toxicity?

A

Tachycardia
Hypertension

91
Q

T/F the typical dental dose is enough to cause myocardial depression and cardiac arrest

A

FALSE, the typical dose is NOT enough to cause this

92
Q

What are the symptoms of Methemoglobinemia?

A

Shortness of breath
Cyanosis (blue skin)
Mental status changes
Headache
Fatigue
Dizziness
Seizures
Coma, death

93
Q

How is Methemoglobinemia reversed?

A

Reversed by IV methylene blue

94
Q

How can you prevent LA toxicity?

A
  1. Give lowest possible dose
  2. Use proper injection techniques (always aspirate)
  3. Use a vasoconstrictor if not contraindicated
95
Q

What reverses LA?

A

Phentolamine

96
Q

Phentolamine ________ duration of action of LA containing a vasoconstrictor

A

shortens

97
Q

What is the mechanism of action of Phentolamine?

A

Blocks alpha-adrenergic receptors of vascular smooth muscle

Causes vasodilation

98
Q

What can cause LA failure?

A

Inflamed tissue
Incorrect needle
Starting procedure prior to max. LA effect

99
Q

What are the characteristics of inflamed tissue?

A

Lower pH
Increased blood flow
Alteration in Na+ channel #

D1 Spring (47 decks)

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