local anesthetics

Question 1

when were procaine and lidocaine first synthesized?

Answer 1

1905 (Einhorn) and 1943 (Lofgren)

Question 2

at a pH of 7.4, how much dibucaine is in the acidic form?

Answer 2

30%

Question 3

what are the 3 structural components of a local anesthetic?

Answer 3

aromatic group, ester or amide linkage, amine group

Question 4

the aromatic group renders the local anesthetic _______.

Answer 4

lipophilic

Question 5

are ester groups or amide groups favored in dentistry?

Answer 5

amide

Question 6

why are ester groups NOT favored in dentistry?

Answer 6

• esters are hydrolyzed by pseudocholinesterase and have very short 1/2 life in plasma
• more allergenic

Question 7

how are amide groups metabolized?

Answer 7

P450 enzymes in the liver, therefore longer 1/2 in plasma than esters

Question 8

the acidic (unionized) amine form allows anesthetic to ___________ while the basic (ionized) form allows for better ___________ once inside the cell.

Answer 8

cross cell membrane, binding to open form of Na+ channel to inhibit nerve impulse

Question 9

t/f: slow firing nerves are inactivated slower by local anesthetics. the opposite is true regarding rapid firing nerves.

Answer 9

true

Question 10

B and C fiber fxns are more or less disrupted by local anesthetics than larger diameter A fibers

Answer 10

more

Question 11

t/f: sensory nerves are homogeneous in size and sensitivity

Answer 11

false. heterogeneous

Question 12

pain is the ____sensitive sensation while ______ is the least.

Answer 12

most, deep pressure

Question 13

the faster a fiber is blocked, the _________it takes to recover.

Answer 13

longer

Question 14

___________produces sensory anesthesia at 1/3 the concentration for motor blockade, but ________ shows no selectivity. which is favored during childbirth epidural?

Answer 14

bupivacaine, etidocaine, bupivacaine

Question 15

inflamed tissue is _____difficult to anesthetize due to lower pH.

Answer 15

more

Question 16

anesthetic must be _________ enough to diffuse into site of action and _________ to bind to proteins and increase duration or action.

Answer 16

hydrophilic, lipophilic

Question 17

the most lipophilic anesthetics

Answer 17

bupivocaine, etidocaine, ropivacaine

Question 18

middle range lipophilic anesthetics

Answer 18

lidocaine, mepivacaine, prilocaine

Question 19

least lipophilic anesthetics

Answer 19

chloroprocaine

Question 20

most local anesthetics are prepared as a water-soluble _______ salt at a pH of _______.

Answer 20

HCl, 6 or 7

Question 21

if epi is included in local anesthetic, pH is lowered to _______ in order to __________. _________ at ejection site usually neutralizes this. ______ might be added prior to injection to increase circulation of free base.

Answer 21

4 or 5, stabilize epinephrine, buffering capacity, NaHCO3

Question 22

CNS affects of local anesthetics

Answer 22

• very sensitive to LAs

- too much can affect CNS activity (dizziness, slurred speech, unconsciousness, death)

Question 23

cardiovascular affects of LAs

Answer 23

• block Na+ and Ca2+ channels

- therefore depress pacemaker activity, excitability, conduction

Question 24

autonomic nervous sys affects of LAs

Answer 24

• depress contractility
• produce hypotension
• inhibition of sympathetic responses

Question 25

bupivacaine is especially __________ because it binds tighter to ______ channels and leaves __________.

Answer 25

cardiotoxic, Na+, slower

Question 26

what is maximum epi per session for uncompromised pt. vs. compromised pt.

Answer 26

200ug, 40ug

Question 27

lidocaine and procaine are potent ________, therefore epinephrine is administered to provide________.

Answer 27

vasodialators, vasocontriction

Question 28

local anesthetics bind to plasma _________ (_________ and _______), while unbound drug is free to diffuse to CNS, various tissues and placenta. liver absorption and metabolism important to keep amide LAs low.

Answer 28

proteins (alpha1- glycoprotein, albumin)

Question 29

esters metabolized very quickly. t1/2 for procaine is ______.

Question 30

esters with __________ are hydrolyzed very rapidly by ______________.

Answer 30

p-aminobenzoic acid, pseudocholinesterase

Question 31

amide t1/2 is __________, which is limited by hepatic blood flow

Answer 31

1.5-3.5 hours

Question 32

first step in amide metabolism is __________.

Answer 32

dealkylation

Question 33

the 2 exeptions to amide metabolism

Answer 33

1. prilocaine- secondary amine, no dealkylation required, extrahepatic metabolism 2. articaine- inactivated in the blood by esterase

Question 34

the most serious adverse affects of LAs result from___________ by

Answer 34

operator error, excessive dosage, intravascular injection (just 10mg of lidocaine injected into a vertebral a. can induce convulsions)

Question 35

excessive admin or intravascular injection may result in _______, _______ or ________.

Answer 35

convulsions, respiratory arrest, cardio collapse

Question 36

convulsion tx (the rest are common sense tx)

Answer 36

benzodiazepine, thiopental, succinylcholine (symptoms only)

Question 37

pregnancy anesthetics

Answer 37

lidocaine, prilocaine category B, articaine, mepivacaine, bupivacaine catercory C