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Pharmacology Exam 5 > Local Anesthetics > Flashcards

Flashcards in Local Anesthetics Deck (34)
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1

What are local anesthetics used for?

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

2

Whats are LAs synthetic analogs for?

Cocaine

3

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

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

4

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

Infiltration
Nerve Block
Epidural
Spinal
Intravenous

5

Describe Infiltration administration of a LA

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

6

Describe nerve block administration of a LA

less predictable and requires precise knowledge of anatomical position.

7

Describe epidural administration of a LA

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

8

Describe spinal administration of a LA

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

9

Describe intravenous administration of a LA

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

10

What is the most common usage of a intravenous LA?

Resetting Fractures

11

What are the three molecular properties of LAs?

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

12

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

Weak bases containing a tertiary amino group as hydrophilic cation group

13

What are the two main sub groups of LAs?

Esters and Amides

14

What are the Ester type LAs?

Cocaine
Procaine
Chloroprocaine
Tetracaine
Benzocaine

15

What are the amide type LAs?

Lidocaine
Mepivicaine
Bepivicaine

16

What is the mechanism of LAs?

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

17

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

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

Why are LAs more effective on active cells?

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

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

Unionized form

20

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

Cationized form

21

What is a detrimental side effect of Bupivicaine?

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

What does Lidocaine selectively block?

tachycardias

23

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

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

24

What is the major factor determining the duration of LAs?

Vascular absorbtion

25

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

epinephrine

26

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

Cocaine

27

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

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

28

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

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

29

What is extremely sensitive to LA block?

Synaptic transmission

30

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

Para amino benzoic acid ester LAs; rare with amide types