Local Anesthetic

Question 1

What distinguishes the acid form from the basic form?

Answer 1

Acid form has a proton that is lacking in basic form

Question 2

T/F: The acidic form will always have a positive charge.

Answer 2

False

Charge will be more positive than basic form but one can be neutral

Question 3

What is the acid/base distribution of dibucaine in the body? What is significance?

Answer 3

50% of each

Need both.

Acid - blocks axonal conduction
Base - allows it to cross neuronal membrane

Question 4

What are the three parts of local anesthetic?

Answer 4

Aromatic group and amine group linked by an ester or amide linkages

Question 5

T/F: Ester linkages break apart more easily than amide linkages.

Answer 5

True

Ester - oxygen
Amide - Nitrogen

Question 6

T/F: Local anesthetic will cross membranes in the brain.

Answer 6

True

Question 7

T/F: Ester linked anesthetics are more susceptible to allergies.

Answer 7

True

Question 8

What type of anesthetic (ester or amide) is used in dentistry?

Answer 8

Amides

Not worried about getting into bloodstream and amides are less likely to develop me allergies

Question 9

LA with an amide linkage are metabolized by _______ in the liver and have a ___________ half life in the plasma.

Answer 9

P450; longer

Question 10

How can you recognize an amide LA versus an ester based on nomenclature?

Answer 10

Amides will have an “i” before the “caine”

Ex. Lidocaine

Question 11

What form of LA crosses the cell membrane?

Answer 11

Uncharged basic form

Question 12

What form of the LA will block axonal conductance?

Answer 12

Charged acidic form bonds to Na channel

Question 13

When can LA not interact with the Na channel?

Answer 13

When it is in the resting state

Can interact with open and inactivated

Question 14

T/F: Anesthetic will act on a nerve that is not firing.

Answer 14

False

Cannot act on resting state of channel

Question 15

T/F: Pain receptors are easier to inactivate with LA than motor neurons.

Answer 15

True

Thinner nerves are easier to inactivate

Question 16

What are the two classes of pain neurons?

Answer 16

A delta - myelinated, fast pain, cold

C fibers - not myelinated, slow pain, hot

Question 17

T/F: Rapidly firing nerves are more susceptible to LA.

Answer 17

True

Question 18

In what order will nerve functions be lost?

Answer 18

1. Pain
2. Cold
3. Warmth
4. Touch
5. Deep pressure

Come back in reverse order

Question 19

T/F: Inflamed tissue is more difficult to anesthetize.

Answer 19

True

Inflammatory products lower the pH -> make it harder for LA to get in the axon (less basic form of LA)

Question 20

T/F: If a LA is more lipid-soluble it will be shorter acting.

Answer 20

False

Hydrophilic will help it diffuse to site, but the more lipid soluble = the less quickly it gets cleared

Lipid soluble = longer acting

Question 21

What effects can LA have on the heart?

Answer 21

Block Na channels and Ca channels (Ca at very high concentrations)

Question 22

Which LA is especially cardiotoxic?

Answer 22

Bupivacaine

Question 23

For use in pregnancy, what are the classes of most LAs?

Answer 23

B and C

Question 24

T/F: Fatalities during dental LA are very low.

Answer 24

True