Chapter 21: Local Anesthetics

Question 1

local anesthetics work by blocking ___channels to prevent transmission of painful stimulus

Answer 1

Na

Question 2

voltage gated Na channels open when the membrane ___

Answer 2

depolarizes

Question 3

t/f when the inactivation gate of the Na channel is close, the channel cannot be reopened

Answer 3

t

Question 4

when the membrane re-polarizes, the inactivation gate ___ in preparation for next depolarization

Answer 4

relaxes

Question 5

inactivation gates of na channels prevent prolonged ___

Answer 5

depolarization

Question 6

why would it be dangerous to block all the Na channels?

Answer 6

not just found in neurons, also in skeletal muscle and cardiac muscle, so the heart and diaphragm wouldn’t contract and we would die

Question 7

what is Tetrodotoxin? what does it do?

Answer 7

natural toxin found in puffer fish; blocks many na channels and can be fatal at low doses

Question 8

what dose of tetrodotoxin is fatal in an adult human?

Answer 8

10-25mg

Question 9

how can tetrodotoxin be used in research of cellular processes?

Answer 9

blocking Na channels makes it easier to observe other processes

Question 10

t/f there is no therapeutic use for tetrodotoxin

Answer 10

t

Question 11

local anesthetics block the Na channels of ___(small/large) diameter nerve fibers more effectively

Answer 11

small

Question 12

the neurons that carry pain signals are ____ in diameter

Answer 12

small

Question 13

small neurons like ____ can be the target of off-target effects of local anesthetics, but large neurons like ___ cannot

Answer 13

autonomic neurons; motor neurons

Question 14

t/f if the concentration of local anesthetic is high enough, large diameter neurons can be blocked

Answer 14

t

Question 15

the primary principle of local anesthetics is that they are administered to the local area where ____ is wanted

Answer 15

nerve block

Question 16

local anesthetics allow for high ____ while having reduced risk of ___

Answer 16

drug concentration; systemic effects

Question 17

the effect of local anesthetic is ___ as the effect is reduced as the drug diffuses away from the local site

Answer 17

transient

Question 18

what is unique about epidurals and spinal blocks in terms of being local anesthetics

Answer 18

the anesthetic is not injected at the site that will feel pain, but rather to the area of the spinal cord that houses the nerves for that area

Question 19

local anesthetics are relatively simple molecules that have what 3 parts?

Answer 19

lipophilic, hydrophilic, linker

Question 20

local anesthetics are divided into 2 groups based on their linking groups: ___ and ___ type agents

Answer 20

ester and amide

Question 21

cocaine is a ___ type local anesthetic

Answer 21

ester

Question 22

procaine is___ local anesthetic that was developed based on discovery of cocaine as an anesthetic

Answer 22

prototypic ester

Question 23

why are other agents used more frequently than procaine?

Answer 23

it has a short duration of action

Question 24

Benzocaine is a ___type anesthetic that is administered by the ___ route

Answer 24

ester; topical

Question 25

t/f benzocaine is used in many creams to treat sunburn pain

Answer 25

t

Question 26

the ester bonds of benzocaine are cleaved by ___

Answer 26

esterases

Question 27

esterases can ___ the duration of action of ester local anesthetics

Answer 27

shorten

Question 28

lidocaine and bupivacaine are ___ type anesthetics

Answer 28

amide

Question 29

amide anesthetics are used more often bc

Answer 29

they cant be craved by esterase’s, so have longer duration of action

Question 30

___ is one of the common agents used in epidurals for childbirth

Answer 30

bupivacaine

Question 31

compare the duration of action for lidocaine vs bupivacaine and what they are useful for

Answer 31

lidocaine has a moderate duration and useful in dental procedures; bupivacaine has longer duration and used in surgery and child birth

Question 32

local anesthetic bind to what part of the Na channel?

Answer 32

inside of the pore

Question 33

do local anesthetics pass through the Na channels?

Answer 33

NO

Question 34

how do local anesthetics gain access to the inside of the Na channel w/o passing through the pore?

Answer 34

cross the cell membrane and access binding site from the inside

Question 35

the ionized form of local anesthetics has a ___ affinity for the binding site

Answer 35

greater

Question 36

t/f local anesthetics having lipophilic and hydrophilic parts help them cross the cell membranes to act on the channels

Answer 36

t

Question 37

the hydrophilic parts of the local anesthetics have a ___ group that can be protonated depending on pH

Answer 37

tertiary nitrogen

Question 38

when the pH and PKa are the same, there is a ____ split between charged and uncharged local anesthetics

Answer 38

50-50

Question 39

the pka of lidocaine is 7.8, so at physiologic pH, there is a near ___ spilt of charged and uncharged drug

Answer 39

50/50

Question 40

the ___ (charged / uncharged) form of local anesthetic is able to cross the membrane

Answer 40

uncharged

Question 41

t/f bc the uncharged form of local anesthetic crosses through to the membrane so the equilibrium is thrown off

Answer 41

t

Question 42

the effects of local anesthetics are stopped when the drug diffuses away from the Na channel which can then

Answer 42

return to resting closed state to await depolarization

Question 43

t/f blood flow easily carries local anesthetic away from site of admisntration

Answer 43

t

Question 44

the ADRs of local anesthetics are ___ dependent

Answer 44

dose

Question 45

if local anesthetics get too much into systemic circulation, they can cause

Answer 45

respiration and cardiac arrest and death q

Question 46

t/f repeated dosing of anesthetic is only given when necessary

Answer 46

t

Question 47

how can the duration of action of a local anesthetic at its local site be prolonged w/o adding more anesthetic?

Answer 47

add a vasoconstrictor like epi prevents drug from flowing through local BV away from admin site