Topical Anesthetic

Question 1

What is the MOA for Topical Anesthetics?

Answer 1

-*Decreases Na+ ion permeability = decrease depolarization = blocks nerve impulse
-blocks nerve conduction at mucous membrane surface

Question 2

What is the range of effective concentrations

Answer 2

0.2% to 20%

Question 3

List the 3 common topical anesthetics in dentistry

Answer 3

1. Benzocaine
2. Lidocaine
3. Combination –> Benzocaine + Butamben + Tetracaine

Question 4

Describe the features of Benzocaine

Answer 4

–> Hurricaine
-ESTER
-very low toxicity
-rapid onset (30sec-2min)
-duration = 5-15min
-concentration = 20%
-metabolized in the plasma and some liver
-MRD = n/a
-pregnancy category C
-unknown lactation safety
-*methemoglobinemia –> associated with sprays

Question 5

Describe the features of Lidocaine

Answer 5

-AMIDE
-very low toxicity
-onset = 2-10min
-duration = 15-45min
-concentration = 2-5%
-metabolized in the liver
-MRD = 200mg
-pregnancy category B
-lactation –> small amount enters breast milk

Question 6

Describe the features of Cetacaine

Answer 6

-combination product (Benzocaine + Butamben + Tetracaine)
-ESTER
-very low toxicity
-rapid onset (30 sec)
-duration = 30-60min
-concentrations = 14% Benzocaine + 2% Butamben + 2% Tetracaine
-metabolized in the plasma and some liver
-MRD = 200mg
-pregnancy category C
-lactation –> use caution

Question 7

increased _______ needed for diffusion through mucous membranes

Answer 7

concentration

Question 8

Toxicity and adverse reactions of topic anesthetics include….

Answer 8

1) Irritation at site of application
2) Sloughing
3) Taste alteration
4) CNS effects (excitation –> depression)
5) CV effects (dec. HR, dec. BP; cardiac arrest)

Question 9

How do you avoid toxic rxns from topicals?

Answer 9

1) Know the relative toxicity
2) Know the concentration
3) Use the smallest volume
4) Use the lowest concentration
5) Use the least toxic drug to satisfy clinical requirements
6) Limit the area of application
7) Avoid sprays