Exam 4 LA's part 1

Question 1

What class are LA’s?

Answer 1

Class 1 sodium channel blockers

Question 2

What is the lipophilic part & what is the hydrophilic part of LA’s?

Answer 2

Aromatic group & amino group

Question 3

How are amides & esters differentiated & what is the exception?

Answer 3

• Amides have 2 I’s & esters have 1.
• Except cocaine it’s an Amide

Question 4

What kind of intermediate chain do esters have?
What about amides?

Answer 4

• Esters have a hydrocarbon chain.
• Amides have a amine group

Question 5

What ester has the highest potency & why?

Answer 5

Tetracaine, it’s very lipid soluble

Question 6

What ester has the longest duration of action?

Answer 6

Tetracaine 60-180mins

Question 7

What amide has the fastest onset?

Answer 7

Lidocaine

Question 8

What promotes a longer duration of action for LA’s?

Answer 8

It’s protein binding capability (that is for intravascular, not local)

Question 9

The closet the pK is to the pH the ____ LA’s act?

Answer 9

Faster

Question 10

Lidocaine needs to be in what form to enter the cell?

Answer 10

Non-ionized & lipid soluble

Question 11

Besides Na+ channels, what are the other sites of action for LA’s?

Answer 11

K+ channels, Ca2+ ion channels, GPCR’s

Question 12

LA’s do not work in what kind of environment & why?

Answer 12

In acidic environment. It becomes ionized

Question 13

How many nodes of Ranvier need to be blocked to localize an area?

Answer 13

2-3 Nodes (~1cm)

Question 14

What would be affected if a LA epidural was injected into a vein instead of epidural space?

Answer 14

Preganglionic B fibers of the SNS

Question 15

The rate of clearance of LA’s is dependent on what?

Answer 15

Cardiac output & protein binding

Question 16

Which LA has the fastest metabolism?

Answer 16

Procaine. It has the least protein binding

Question 17

What amide has the fastest metabolism?

Answer 17

Prilocaine

Question 18

How are esters metabolized?

Answer 18

• Via hydrolysis by plasma cholinesterases.
• Except cocaine, which is via liver

Question 19

Which LA’s can cause allergies & what causes the allergy?

Answer 19

Esters d/t metabolite Para-aminobenzoic acid (PABA)

Question 20

What LA’s have a pulmonary first-pass extraction?

Answer 20

• (B)upivacaine
• (L)idocaine
• (P)rilocaine

Question 21

Which local anesthetic property is most important when it comes to the duration of action?

Answer 21

Lipid solubility > clearance > protein binding

Question 22

Which type of LA is preferred in pregnancy?

Answer 22

Ester. D/t amides protein binding & crossing placenta causesing Ion trapping in fetus

Question 23

What LA has the most protein binding?

Answer 23

Bupivacaine

Question 24

What is the infiltration dose for lidocaine?

Answer 24

300 mg plain & 500 mg w/ Epi

Question 25

What LA’s can cause Methemoglobinemia?

Answer 25

Prilocaine & benzocaine

Question 26

What is the dose of methylene blue?

Answer 26

• 1-2 mg/kg IV over 5mins
• Do not exceed 8 mg/kg

Question 27

What protein does bupivacaine bind to?

Answer 27

Alpha-1 glycoprotein

Question 28

Esters get hydrolized, list the 3 esters from fastest to slowest hydrolysis?

Answer 28

Chloroprocaine > procaine > tetracaine

Question 29

Which LA is not a weak base?

Answer 29

Benzocaine

Question 30

What is the onset & duration of benzocaine?

Answer 30

• Rapid onset.
• Duration 30-60mins

Question 31

A 65 yo Pt with methemoglobinemia, weighing 120lbs, need methylene blue, what is the max dose?

Answer 31

54.55kg x 8 mg/kg= 436.4 mg