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Pharmacology Exam 5 > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

What are local anesthetics used for?

A

To reversibly block nerve conduction in a particular region of the body

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2
Q

Whats are LAs synthetic analogs for?

A

Cocaine

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3
Q

At high doses what are the negative side effects of LAs?

A

They can readily enter systemic circulation and cause convulsions or respiratory failure

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4
Q

What are the ways in which a LA can be administered?

A 
Infiltration
Nerve Block
Epidural
Spinal
Intravenous
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5
Q

Describe Infiltration administration of a LA

A

Most common means of injecting, subdermally. Nerve endings are totally paralyzed

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6
Q

Describe nerve block administration of a LA

A

less predictable and requires precise knowledge of anatomical position.

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7
Q

Describe epidural administration of a LA

A

Injected near the dorsal root of spinal cord and is capable of blocking all sensation below the segment exposed to the LA. NO NEEDLE PENETRATION OF THE DURA. Intensity and duration are less predictable than spinal

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8
Q

Describe spinal administration of a LA

A

Injected intrathecally, diffuses through the CSF to motor as well as sensory neurons. VERY PREDICTABLE.

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9
Q

Describe intravenous administration of a LA

A

Injected into a limb whose venous return has been limited with a tourniquet.

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10
Q

What is the most common usage of a intravenous LA?

A

Resetting Fractures

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11
Q

What are the three molecular properties of LAs?

A
  1. Ionizable head group
  2. Ester/Amide connecting chain
  3. Non-polar tail, usually containing a phenyl ring
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12
Q

What can clinically used LAs also be considered? What do they contain?

A

Weak bases containing a tertiary amino group as hydrophilic cation group

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13
Q

What are the two main sub groups of LAs?

A

Esters and Amides

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14
Q

What are the Ester type LAs?

A 
Cocaine
Procaine
Chloroprocaine
Tetracaine
Benzocaine
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15
Q

What are the amide type LAs?

A

Lidocaine
Mepivicaine
Bepivicaine

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16
Q

What is the mechanism of LAs?

A

They preferentially block voltage dependent sodium channels in nerve and muscle membranes.

17
Q

What is an odd thing about the receptor site for LAs? What importance does this play?

A

The receptor site occurs within the sodium channel nearest the cytoplasmic side of the membrane. LAs ARE TOO LARGE TO PASS THROUGH THE CHANNEL FROM THE OUTSIDE. The unionized form has to cross the membrane and then dissociate to the cationic form to bind to the receptor.

18
Q

Why are LAs more effective on active cells?

A

The intensity of the LA increases with spike frequency, because the opened and inactivated states of the sodium channel (which bind LAs most readily) are increasingly available for occupation

19
Q

Which form of LAs most rapidly penetrates the cell thus taking effect quciker?

A

Unionized form

20
Q

Which for of LAs are more active at blocking the NA channel but take longer to come into effect?

A

Cationized form

21
Q

What is a detrimental side effect of Bupivicaine?

A

Can be cardio toxic because it has a slow rate of dissociation from the myocardial sodium channel. It can modify the normal frequency range of the myocardium

22
Q

What does Lidocaine selectively block?

A

tachycardias

23
Q

Factors controlling the time, course and intensity of local anesthesia:

A

Method of administrative dose
Lipid solubility (more lipophilic = more potent and longer duration
Membrane permiability barriers
Vascular Absorbtion

24
Q

What is the major factor determining the duration of LAs?

A

Vascular absorbtion

25
Q

What are LAs usually used in combo with to prolong duration and potency?

A

epinephrine

26
Q

What LA is unique in that it has a vasoconstrictory response thus not needing epinephrine?

A

Cocaine

27
Q

What can happen if LAs are incorrectly injected or absorbed too rapidly?

A

Can cause CNS convulsions and depression (leading to respiratory depression)

28
Q

What is a significance of what can happen if LAs are incorrectly injected or absorbed too rapidly?

A

There are no antagonists to these effects, treat with artificial respiration and anticonvulsant

29
Q

What is extremely sensitive to LA block?

A

Synaptic transmission

30
Q

Allergic reactions are most frequently seen with what type of LAs?

A

Para amino benzoic acid ester LAs; rare with amide types

31
Q

How is benzocaine given to a patient?

A

Applied topically

32
Q

How and where are ester type LAs metabolized?

A

They are hydrolyzed by PLASMA (nonspecific) cholinesterase

33
Q

How and where are amide type LAs metabolized?

A

They are dealkylinated and hydrolyzed in the liver

34
Q

What is the metabolism of LAs important in controlling?

A

the anti arrythmic duration of procainamide and lidocaine

fetal CNS depression due to absorption of LA from maternal circulation

Pharmacology Exam 5 (8 decks)

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