Local Anesthetics

Question 1

What letter do all amides have?

Answer 1

Two I’s

Question 2

What determines the lipid solubility of the drug?

Answer 2

The aromatic ring and hydrocarbon chain length

Question 3

Do high or low lipid soluble drugs penetrate cells quicker?

Answer 3

High lipid solubility

Question 4

Are amides or esters more stable overall?

Answer 4

Amides

Question 5

What does the metabolism of esters result in? Amides?

Answer 5

Production of PABA for esters

Nothing really for amides, which is why they are more commonly used now

Question 6

Are all locals weak or strong bases?

Answer 6

Weak base-so they exist as ionized and unionized

Question 7

As pH increases (More basic), there is ____ ionized particles of LA

Answer 7

Less, meaning more LA will enter the cell

Question 8

As pH decreases (more acidic) there is ____ ionized particles of LA in the cell

Answer 8

more

Question 9

So if a patient is acidotic for some reason, how will that affect LAs?

Answer 9

They won’t be as effective

Question 10

What is LAs MOA?

Answer 10

Reversibly bind to voltage gated Na channels. This blocks Na influx and AP and nerve conduction

Question 11

What size of fibers are LAs more effective at blocking?

Answer 11

Small

Question 12

Do myelinated or non myelinated fibers get blocked first?

Answer 12

myelinated

Question 13

The loss of nerve function proceeds as ……

Put these in order: Loss of pain, temp, skeletal muscle, touch, and proprioception

Answer 13

Pain, temp, touch, proprioception, skeletal muscle tone

Question 14

What type of fiber transmits pain and temp?

Answer 14

A delta, which is myelinated

Question 15

What type of fiber transmits pain and postganglionic signals?

Answer 15

C, nonmyelinated

Question 16

Explain in depth of LA block Na channels.

Answer 16

The LA exists in equilibrium as ionized and unionized outside the cell membrane. The unionized part can diffuse into the cell, then get ionized with H+ (or maybe others as well). It then binds to the receptor, blocking it.

Question 17

What is each Na channel comprised of?

Answer 17

A single alpha subunit containing a central ion conducting pores associated with accessory beta subunits

Question 18

What are the factors that control absorption and distribution of LAs?

Answer 18

Vascularity, protein binding (slowly metabolized)

Question 19

What is the biggest factor for duration of action?

Answer 19

Protein binding

Procaine is 6% protein bound and has a short duration of action wheras bupivacaine is 95% bound and has a long duration of action

Question 20

How much can LA duration of action be increased with coadministration of epi?

Answer 20

2X using 1:200,000 epi

Question 21

What is the metabolism of esters? Besides cocaine

Answer 21

Plasma cholinesterase

Question 22

How is cocaine metabolised?

Answer 22

Hydrolyzed in the liver

Question 23

How are amides metabolized?

Answer 23

Amidases

Question 24

What are the ADEs of LAs?

Answer 24

CNS-Excitation followed by depression and death due to respiratory depression
CV- Bradycardia, heart block, vasoldilation (hypotension)
Allergic reactions-More common with esters r/t PABA

Question 25

What are the contraindications to LAs?

Answer 25

Heart block, concurrent use if quinidine, flecainide, disopyramide, and procainamide, and prior use of amiodarone

Question 26

What are the three causes of possible LA toxicity

Answer 26

IV injection Rapid absorption from vascular area Overdose

Question 27

What are the factors that reduce toxicity?

Answer 27

Use smallest dose possible Lower dosage on frail patients Inject slowly and aspirate to ensure not in vessel Add epi

Question 28

What is the max dose of epi to give with LA?

Answer 28

200mcg

Question 29

What area should we avoid using epi with the LA?

Answer 29

In areas with end arteries d/t possible development of necrosis due to prolonged hypoperfusion

Question 30

What is a unique characteristic of cocaine?

Answer 30

It produces localized vasoconstriction as well as anesthesia

Question 31

What two drugs are not good substitutes for cocaine?

Answer 31

Procaine and chloroprocaine

Question 32

Which LA has the potential to cause methemoglobinemia?

Answer 32

Benzocaine

Question 33

How long can bupivacaine blocks last?

Answer 33

Up to 24 hours

Question 34

What is the issue with prilocaine?

Answer 34

Can also cause methemoglobinemia

Question 35

What is unique about articaine?

Answer 35

It is technically an amide, but it contains an additional ester group that helps it to be metabolized quicker

Question 36

What is the most commonly used dental anesthetic?

Answer 36

Articaine

Question 37

What is the name for combination of LAs?

Answer 37

EMLA