Chapter 10

Question 1

How do local anesthetics work? What channels do they block? How does blocking these channels prevent pain?

Answer 1

local anesthetics block-voltage-gated Na+ channels in peripheral nerves.

Question 2

Which nerves are the first ones affected by local anesthetics?

Answer 2

myelinated nerves

Question 3

What are the pharmacokinetics of local anesthetics? How and where are the different local anesthetics metabolized?

Answer 3

A- depends on pH of tissue at site of application
D- throughout the body, easily crosses membranes
M- Esters metabolized both plasma and liver, Amides metabolized by liver.
Excretion: Renal

Question 4

What are the components of a local anesthetic? What is the function of each one?

Answer 4

A vasoconstrictor: helps decrease systemic absorption, prolongs duration.

An antioxidant: Prolong shelf life, sulfite which cause allergic reaction and or precipitate asthma attacks in some patients

Sodium hydroxide: adjusts pH appropriately

Sodium Chloride: to make solution isotonic to tissues

Question 5

What are the two types of chemically different local anesthetics? Which local anesthetics fit into each group?

Answer 5

Esters: higher allergen potential.
Local with Esters: Procaine, Benzocaine, Tetracaine and cocaine

Amides: Lower allergen potential
Locals with Amides: Lidocaine, prilocaine, mepivacine, articaine, bupivacaine.

Question 6

Which local anesthetics are most likely to cause allergic reactions?

Answer 6

ESTERS

Procaine, Benzocaine, Tetracaine and cocaine

Question 7

What are the desirable characteristics of a local anesthetic?

Answer 7

• potent
• rapid onset
• good duration
• reversible
• good penetration of tissues
• esaily metabolized and excreted
• no locatized, systemic, allergic reaction
• low cost
• stable solution
• can be sterilized

Question 8

What are the amide local anesthetics? How are they similar? How are they different? In what situations might you use each different type?

Answer 8

1. Amides locals: Lidocaine, prilocaine, mepivacine, articaine, bupivacaine.
2. Similarities: Block voltage-gated Na⁺ channels.
   - Metabolized in the liver (longer duration than esters).
   - Rare allergies.
3. Differences:
   - Lidocaine: Fast onset, moderate duration, versatile.
   - Bupivacaine: Long duration, high potency, cardiotoxic (use for long procedures).
   - Mepivacaine: No vasodilation, good for patients avoiding epinephrine. Short duration
   - Prilocaine: Risk of methemoglobinemia, used in dentistry.
   - Ropivacaine: Long-lasting, less cardiotoxic than bupivacaine.
   - Articaine: Fast onset, ideal for dental work.
4. Short Procedures: Lidocaine, Mepivacaine, Prilocaine.
   Long Procedures or Pain Control: Bupivacaine, Ropivacaine.
   Dental Work: Articaine, Prilocaine, Lidocaine.
   Cardiac Risk Patients: Mepivacaine, Ropivacaine.

Question 9

How long does each type of local anesthetic last? What formulations are available for each?

Answer 9

Lidocane: plain 5-10 min, with epi 60-90 min.
- formulations: injection, topical ointment, topical gel, oral spray and patch.

Mepivacaine: plain: 30-1 hr
- formulations: injections

Prilocaine: Less potent than lidocaine with fewer cardiac risk.

Question 10

For which dental procedures would an extremely long-acting local anesthetic be best to use? What would the best choice be?

Answer 10

Full mouth reconstructions, implants, extensive periodontal treatments.

Best Amides anesthetics: Bupivacaine

Question 11

For which dental procedures would an extremely short-acting local anesthetic be best to use? What would the best choice be?

Answer 11

Fillings, topical numbing, minor restorative work

Lidocaine, Mepivacaine (Carbocaine) and Prilocaine

Question 12

What topical anesthetics are available for use? How are they the same? How are they different?

Answer 12

Amide Topical:
- EMLA (lidocaine and Prilocaine)
- Oraqix (Lidocaine and Prilocaine)

Ester Topicals:
- Benzocaine
- Tetraciane

Question 13

What is a vasoconstrictor and why is one often used in combination with a local anesthetic?

Answer 13

• Increased duration of action at application site
• Decreased systemic distribution of local anesthetics
• Reduces bleeding in quadrant being treated.

Question 14

What are the common vasoconstrictors? In which local anesthetics are they found? What are the concentrations of local anesthetics that are used?

Answer 14

• Epinephrine and levonordefrin
• Epinephrine: Lidocaine, Mepivacaine, Bupivacaine (1:50, 1:100, 1:200)
• Levonordefin: Mepivacaine (1:20)

Question 15

How are doses of local anesthetic calculated?

Answer 15

2% lidocaine in a 1.8 ml cartidge

2% of 1000= 20%
20 X 1.8= 36mg

Question 16

How are doses of vasoconstrictor calculated?

Answer 16

g/ml X mg/g

1:100,000= 0.01 X 1.7=0.017mg
1:200,000= 0.02 X 1.7= 0.034 mg
1:50,000= 0.5 X 1.7= 0.85mg

Question 17

What information needs to be recorded in a patient’s chart about local anesthetics and vasoconstrictors, and why?

Answer 17

the type and dosage of the anesthetic used, the concentration of any added vasoconstrictor, the injection site and technique, patient reaction, and any relevant medical history

Question 18

What are the common adverse reactions associated with the use of local anesthetics?

Answer 18

Allergy
CNS Effects
Cardiovascular effects
Local Effects
Pregnancy

Question 19

What is methemoglobinemia? Which local anesthetics are most likely to cause it? What are some of the warning signs that it may be occurring?

Answer 19

• Methylated hemoglobin: cannot carry o2 around the body.
• Prilocaine (Citanest, Citanest-Forte)
• Bluish skin tone, around lips, nail beds

Question 20

What is the maximum dose of vasoconstrictor that should be administered to a healthy patient? A cardiac patient? How do these doses relate to the amounts commonly found in each cartridge of local anesthetic?

Answer 20

Healthy Patients: 0.2mg limit vasoconstrictor

Cardiac patients: necessary procedures: 0.04mg
- elevective procedures: severe cardiovascular disease, uncontrolled high blood pressure and MI or stroke within 6 months

Question 21

What are the common drug interactions with epinephrine? What effect can these interactions cause in the patient?

Answer 21

Antidepressants can cause increased blood pressure ( Tricyclic antidepressants , MAOI antidepressants)

Nonselective b-blockers (Propranolol) causes increased Bp and tachycardia.

Antidiabetic medications: metformin causes increase blood glucose.