Pharmacology of Local Anesthetics

Question 1

What class of local anesthetic is longer-acting?

Answer 1

Amide LAs - Ester LAs are shorter-acting but potentially less toxic

Question 2

What types of nerve bundles (Mantle/Core) are more susceptible to LAs?

Answer 2

Mantle Bundles - they are placed more proximally

Question 3

What is the effect of inflammation on tissue pH?

Answer 3

Inflammation lowers tissue pH - thus reducing the effectiveness of most LAs

Question 4

Injection administration of an LA is used to target what nerves?

Answer 4

Peripheral nerve endings, nerve trunks, or nerve roots

Question 5

What is the purpose of the inactive form of LAs?

Answer 5

Weak bases that can readily cross the cell membrane in order to bind Na+ channels once active

Question 6

How should an LA be administered to target only superficial nerves?

Answer 6

Topically

Question 7

What are the Amide LAs?

Answer 7

Lidocaine, Prilocaine, Articaine, Bupivacaine

Question 8

True/False. pKa predicts the rate of onset of a LA.

Answer 8

True - Lower pKa indicated faster onset while Higher pKa indicated longer onset

Question 9

True/False. LAs have antihistaminic, anticholinergic, and antiarrhythmic effects

Answer 9

True - particularly lidocaine

Question 10

Methemoglobinemia is most associated with what LA?

Answer 10

Prilocaine

Question 11

What is the effect of lipid solubility on LA potency?

Answer 11

The greater the lipid solubility, the more potent the LA

Question 12

What Ester LA is considered the longest lasting and used for spinal anesthesia and ophthalmic procedures?

Answer 12

Tetracaine

Question 13

These types of nerve fibers are most susceptible to LAs.

Answer 13

Pain > Temperature > Light Touch > Deep Pressure > Proprioception

Question 14

True/False. Myelination has a greater effect on LA effectiveness than fiber diameter.

Answer 14

False. Fiber diameter is more influential than myelination

Question 15

How do intrinsic neuronal properties influence the effectiveness of LAs?

Answer 15

Small-diameter fibers, myelinated axons, and neurons with hire firing rates are most susceptible to LAs

Question 16

What are the commonly used topical LAs?

Answer 16

Lidocaine, Benzocaine (only used topically)

Question 17

A metabolite of this class of local anesthetics may cause serious allergic reactions in some patients.

Answer 17

Ester LAs

Question 18

What is neuraxial anesthesia?

Answer 18

Administration of an LA directly into the fatty tissue surrounding nerve roots as they exit the spine

Question 19

What is the active form of an LA?

Answer 19

Charged cationic form

Question 20

What may be used to reverse cardiac ADRs of LAs?

Answer 20

IV lipid infusion

Question 21

This vasoconstrictor has fewer cardiac effects than epinephrine, but potentially interacts with tricyclic antidepressants.

Answer 21

Levonordefrin

Question 22

What are the commonly injected LAs?

Answer 22

Lidocaine, Bupivocaine, Mepivacine, Procaine

Question 23

What effect does vasodilation have on LA effect?

Answer 23

Most LAs as vasodilators. This reduces the time LAs are within tissues and decreases their duration of action

Question 24

What is the effect of low pH on the effectiveness of LAs?

Answer 24

Low pH favors the active form of LAs. This means there is less of the LA in inactive form to cross the cell membrane. The result is longer induction and lower effectiveness

Question 25

What vasoconstrictors are commonly administered with LAs?

Answer 25

Epinephrine, Levenordefrin

Question 26

What is the only LA that is a vasoconstrictor, rather than vasodilator?

Answer 26

Cocaine

Question 27

True/False. Greater protein binding increases the effectiveness of LAs.

Answer 27

False. The higher the degree of protein binding, the less effective the LA

Question 28

What is the MOA of LAs?

Answer 28

Bind inside voltage-gated Na+ channels to block initiation and propagation of action potentials

Question 29

What are the most common cardiac ADRs associated with LA use?

Answer 29

Bradycardia, hypotension, shock

Question 30

What are the common Ester LAs?

Answer 30

Procaine, Chloroprocaine, Tetracaine, Benzocaine, Proparacaine