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Pharmacology > ! Local Anesthetics > Flashcards

! Local Anesthetics Flashcards

1
Q

Learning objectives
Describe the pharmacokinetic and pharmacodynamic properties of local anesthetics
Discuss clinical pharm of local anesthetics, including toxicity and effects on organ systems \
List the common routes of administration of local anesthetics
Describe chemical make up and how TI effects pharmacological properties

A

Ok

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2
Q

List local anesthetics

A 
Benzocaine
Bipivacaine
Cocaine
Dibucaine
Lidocaine
Procaine
Articaine
Chlorprocaine
Levobuoivacaine
Mepivacaine
Proparacaine
Ropivacaine
Tetracaine
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3
Q

Amides

A 
LIdocaine
MepIvacaine
BupIvacaine
RopIvacaine
ArtIcaine

Iiiiii

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4
Q

Esters local anesthetic

A

Benzocaine
Cocaine
Procaine
Tetracaine

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5
Q

Short lasting local anesthetics

A

Procaine with potency of 1

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6
Q

Medium lasting local anesthetic

A

Lidocaine (4)
Mepivacaine (2)
Articaine (?)
Cocaine (2)

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7
Q

Long acting local anesthetics

A

BupIvacaine (16)
Ropivacaine (16)
Tetracaine (16)

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8
Q

Typical local anesthetics contain both hydrophilic and hydrophobic components that are separated by an __ or __ link

A

Ester or amide

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9
Q

Agents with ester links are more prone to __ that amides, so have a shorter duration

A

Hydrolysis

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10
Q

How does use of a vasoconstrictor effect absorption of local anesthetics like epinephrine

A

Reduce intermediate and short duration absorption

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11
Q

Cocaine is unique that it has intrinsic symapthomimetic ___ properties

A

Vasoconstriction

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12
Q

Amide IV bolus

A

Widely distributed after intravenous bolus administration

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13
Q

Tissue distribution ester type agents

A

Extremely short plasma half life

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14
Q

Ester metabolism

A

In plasma by circulating butyrylcholinesterase/plasma cholinesterase enzymes

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15
Q

Amide type metabolism

A

In liver and then excreted int he urine as charges substances CYP450

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16
Q

MOA local anesthetics

A

Block voltage gates Na currents and stop the spread of AP across nerve axons (the receptor site for local anesthetics is at the inner vestibule of the Na channel); block nerve conduction by decreasing or preventing the large transient increase in the permeability of excitable membranes to sodium that normally is produced by a depolarization of the membrane

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17
Q

The smaller and more lipophilic the local anesthetic, the __ the rate of interaction with the sodium channel and the more __ the agents actions

A

Faster

Potent

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18
Q

What are some lipophilic local anesthetics

A

Tetracaine
Bupivacaine
Ropivacaine

More potent and longer durations

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19
Q

Local anesthetics preferentially block __ fibers because the distance over which such fibers can passively propagate an electrical impulse is shorter

A

Small

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20
Q

__ nerves tend to become blocked before unmyelinated nerves of the same diameter, so preganglionic B fibers are blocked before smaller unmyelinated C fibers

A

Myelinated

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21
Q

Fibers that fire at a __ frequency of depolarization are blocked before those that fire __

A

Higher

Slower

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22
Q

Type A delta and C fibers are blocked ___ than the large alpha A fibers

A

Earlier

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23
Q

In bundles of large mixed nerves in large nerve trunks, it is not uncommon for motor nerve block to occur before sensory block because motor nerves are usually located circumferential

A

Motor nerves are the first nerves to be exposed to the local anesthetic when it is administered into the tissue surrounding the nerve

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24
Q

In the extremities, proximal sensory fibers are located in the outer portion of the nerve trunk and distal sensory innervation is located in the __ of the nerve

A

Core

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25
Q

Type A fibers

A

Alpha(proprioception, motor)
Beta (touch, pressure)
Gamma(muscle spindles)
Delta (pain, temperature)

  • listed thickest to thin
  • all heavily myelinated and
  • listed increasing sensitivity to block
26
Q

Type B fiber

A

Preganglionic autonomic
Small diameter
Light myelination
Huge sensitivity to block

27
Q

Type C fiber

A 
Dorsal root (pain)
Sympathetic (postganglionic)

Both small diameter
Both non myelinated

HUGE sensitivity to block

28
Q

Routes of local anesthetic administration

A

Topical
IV
Injection

29
Q

Infiltration anesthesia injection

A

Directly into tissue in the vicinity of peripheral nerve endings without taking into consideration the course of cutaneous nerves; can be superficial enough to include only the skin and deep enough to include intraabdominla organs

30
Q

Block anesthesia injection

A

Injection in major nerve trunks; the purpose is to anesthetize a region distal to the site of injection; examples: femoral nerve block for surgery distal to the knee, brachial plexus block for procedures on the upper extremities or shoulders

31
Q

Spinal anesthesia injections

A

Injection into CSF in lumbar space ; produces anesthesia over a considerable fraction of the body with a dose of local anesthetic that produces negligible plasma levels

32
Q

Epidural anesthesia injection

A

Injection into epidural space can be performed in the sacral hiatus or int he lumbar, thoracic, or cervical regions of the spine; current popularity has arisen from the development of catheters tat can be placed into the epidural space, allowing either continuous infusions or repeated bolus administration

33
Q

IV regional anesthesia

A

For short surgery
Distal vein given
While circulation of the limb is isolated with a proximally placed tourniquet; large doses of local anesthetics are used, so the tourniquet should remain long enough to ensure that high circulating drug levels do not cause systemic toxic events

34
Q

___ prolong actions of anesthetics

A

Vasoconstrictors

35
Q

Why do vasoconstrictors prolong duration(epi activates a adrenergic and causes vasoconstriction)

A

Decreases the rate of anesthetic absorption into circulation, reduces the rate at which the local anesthetic is metabolized, and reduces systemic toxicity

36
Q

Why should epinephrine containing solutions not be injected into tissues supplied by end arteries (ears, toes, nose, fingers, penis)

A

Resulting vasoconstriction may cause gangrene

37
Q

Why use caution when injecting vasoconstrictor into muscle

A

Epi can activate B 2 receptor in skeletal muscle vascular beds and cause dilation, increasing the potential for systemic toxicity

38
Q

Cocaine

A

Potentials effects of NE on a receptors by blocking the norepinephrine transporter and results in localized vasoconstriction, eliminating the need for combining the drug with epi

39
Q

What are the two types of local anesthetic toxicity

A

Toxicity following systemic absorption

Direct neurotoxicity from local effects when given in close proximity to the spinal cord and other major nerve trunks

40
Q

Low concentrations have the ability to produce what CNS issues

A

Sleepiness, light headedness, visual and auditory disturbances, and restlessness (early signs of toxicity include circumoral and tongue numbness and a metallic taste)

41
Q

High concentrations may cause what

A

Nystagmus , muscle triwthcing, convulsions

42
Q

What do you do when large doses of anesthetics are needed

A

Premedication with a parenteral benzodiazepine can provide prophylaxis against CNS toxicity by raising the seizure threshold (local anesthetics cause depression of cortical inhibitory pathways, thereby allowing unoppposed activity of excitatory neurons pathways)

43
Q

Central stimulation is followed by depression; death is usually caused by __ __

A

Respiratory failure

44
Q

Undesired CV system effects of local anesthetics

A

Direct effects on cardiac and smooth muscle and from indirect effects on the autonomic nervous system

45
Q

Local anesthetics block cardiac __ channels and decreases electrical excitability, conduction rate, force of contraction and cause arteriolar dilation, leading to systemic hypotension

A

Sodium

46
Q

Cocain

A

NOT THE CASE

Inhibits NE reuptake and results in vasoconstriction (ischemia), hypertension, and cardiac arrhythmias)

47
Q

BupIvacaine

A

Most cardiotoxic due to its long duration of action

48
Q

Lidocaine

A

Class Ib antiarrhythmic

49
Q

Lidocaine suppresses autonomicaity of conduction tissue by increasing electrical stimulation threshold of __ , ___ and ______

A

Ventricle, His-Purkinje system, and spontaneous depolarization of the ventricles during diastole by a direct action on the tissues

50
Q

Lidocaine blocks the initiation and conduction of nerve impulses by __, which results in inhibition of depolarization with resultant blockage of conduction

A

Decreasing the neuronal membranes permeability to sodium ions

51
Q

Most common adverse effect of IV lidocaine is what

A

CNS toxicity-usually mild, dose dependent and always resolves upon discontinuation

52
Q

Why are allergic reactions to ester type local anesthetics more common

A

Metabolism to allergy causing compounds (allergies to amide type local anesthetics are rare)

53
Q

Ester local anesthetics have _ i and amide have _ i

A

One

More than 2

54
Q

T/F patients allergic to one ester type agent will most likely be allergic to another

A

T

55
Q

Benzocaine

A

Poor solubility in water, used only as sa topical agent; used topically for dermatological conditions, hemorrhoids, premature ejaculation, and as an anesthetic lubricant

56
Q

BupIvacaine

A

Long duration of action capable of producing prolonged anesthesia;has a tendency to provide more sensory block than motor block

57
Q

Cocaine

A

Clinically desired properties of cocaine are the blockade of nerve impulses and local vasoconstriction get actions secondary to its ability to inhibit local NE reuptake; euphoric properties are primarily due to inhibition of catecholamine reuptake (mainly dopamine in the CNS) used primarily as a topical anesthetic of the URI

58
Q

Dibucaine

A

Due to toxicity associated with injections, now used only as a topical cream for use on the skin

59
Q

Lidocaine

A

Prototypical amide local anesthetic; alternative choice for individuals sensitive to ester type local anesthetics; produces faster, more intense, longer lasting, and more extensive anesthesia than an equal dose of procaine; used as an antiarrhythmic

60
Q

Procaine

A

Compared to newer agents , procaine generally has lower potency, slower onset, and shorter duration of action; only used for infiltration anesthesia (local anesthesia produced by injection of the anesthetic solution directly into the area of terminal nerve endings) metabolized to a para-aminobenzoic acid, which inhibits the action of sulfonamide antibiotics

Pharmacology (52 decks)

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