Local Anesthetic Therapeutics

Question 1

Desirable properties of local anesthetics

Answer 1

Non-irritating
Non-allergenic
Minimal systemic toxicity
Rapid onset
Adequate duration
Completely reversible effects
Selective to nocioception (pain sensation)
Effective as a topical agent

Question 2

What effects does cocaine have on the body?

Answer 2

CNS stim- feeling of euphoria, well-being
Convulsions at high dosages
Cardiovascular stim- ^ BP, ^ HR, arrhythmias
Hyperexia- elevated temps

Used as local in upper respiratory procedures and as a topical for laceration repair

Question 3

Characteristics of Procain “Novocain”

Answer 3

Ester anesthetic
Highly allergenic
Poor efficacy, profundity (depth), and duration

Question 4

Which local anesthetic is used most for dental surgery?

Answer 4

Lidocaine

Question 5

Characteristics of lidocain “Xylocain” “Lignospan”. What are the types available?

Answer 5

GOLD STANDARD
Excellent onset and profundity with vasoconstrictor
On its own considered a vasodilator which is why a vasoconstrictor is required

2% lidocaine HCl, 1:100,000
2% lidocaine HCl, 1:50,000

Question 6

Characteristics of Prilocaine “Citanest”. Types available

Answer 6

Similar to lidocaine with epi
Metabolic product, toludine, may be responsible for the side effect of methemoglobinemia

4% prilocaine HCl, plain
4% prilocaine HCl, 1:200,000 epi

Question 7

What is methemoglobinemia, what causes it, treatment?

Answer 7

Increase amts of hemoglobin with oxidized iron
Blood turns from red tochocolate brown
Induced by: prilocaine, benzocaine, nitrates and sulfonamides
Treated with infusion of methylene blue dye

Question 8

What is the common name for the topical combination of prilocaine and lidocaine?

Answer 8

Oraqix

Question 9

Characteristics if mepivicain “Carbocaine” “Polocaine”. Two formulations?

Answer 9

Shorter duration of pulpal anesthesia than lidocaine with epi
Minimal vasodilating properties

3% mepivicaine, plain
2% mepivicaine, 1:20,000

Question 10

Characteristics of articaine “Septocaine” “Ultracaine”. Types available?

Answer 10

Similar anesthetic characteristics to lidocaine w/ epi
More effective than lidocaine for mandibular INFILTRATION

4% articaine, 1:100,000 epi
4% articaine, 1:200,000 epi

Question 11

What allows us to administer repeated injections of articaine during lobg appointments?

Answer 11

Rapid elimination from systemic circulation from metabolism in plasma

Question 12

Which injection do we NOT use articaine for? Why?

Answer 12

Mandibular blocks

Increased risk of paresthesia

Question 13

Characteristics of bupivicaine “Marcaine” “Vivicaine”. Types available?

Answer 13

Long onset time due to elevated pKa
Prolonged soft tissue anesthesia- used for pot-op pain
Duration is due to protein bonding

0.5% bupivacaine, 1:200,000 epi

Question 14

What will cause faster onset of anesthesia?

Answer 14

pKa that is closer to physiologic pH

Question 15

What can determine, in large part, the toxic potential of the agent?

Answer 15

Pharmacokinetic consideration

Balance btw uptake of LA into the systemic circulation and its removal through redistribution, metabolism and excretion

A-absorption, D-distribution, M-metabolism, E-excretion

Question 16

What is the driving force for distribution of the anesthetic agent? WHat is the greatest barrier to this?

Answer 16

Diffusion

The perineurium (nerve sheath) is the greatest barrier, free nerve endings affected within seconds

Question 17

What does systemic absorption depend on?

Answer 17

Dose
Pharmacologic profile of agent
Presence of vasoconstrictor
Site of administration

Question 18

Which anesthetics have potent vasodilating properties and require vasoconstrictors?

Answer 18

Lidocaine and procaine

Fast uptake requires vasoconstrictor to slow it down

Question 19

Which anesthetics have minimal vasodilating properties?

Answer 19

Mepivicaine and Prilocaine

Require less vasoconstrictor to retard uptake

Question 20

Which anesthetic is highly lipid soluble and therefore takes longer to take effect?

Answer 20

Bupivicaine- binds with injected tissues

Question 21

Where does metabolism of esters occur?

Answer 21

In the blood stream by plasma cholinesterases

Question 22

Where does metabolism of amide anesthetics occur?

Answer 22

In the liver

Question 23

Which anesthetic has characteristics of both amides and esters and is mostly metabolized in the bloodstream?

Answer 23

Articaine

Question 24

What are the most common systemic affects by local anesthetics?

Answer 24

Cardiovascular and CNS

But any organ dependent on nervous or muscular activity may be affected

Question 25

CNS effects from local anesthetics

Answer 25

Moves through circulation into the brain
Excitatory symptoms followed by depression
Tremors or seizures

Question 26

Cardiovascular systemic effects from LA at high doses

Answer 26

Hypotension due to vasodilation
Decreased force of heart contraction
Inhibition of arrhythmias
Tachycardia, hypertension, increased cardiac output from sympathetic arousal

Question 27

Effects of epinephrine on CVS stimulation

Answer 27

Increased heart rate and BP

Question 28

Effects of lidocaine on CNS stimulation and depression

Answer 28

Stimulation: restlessness and convulsions
Depression: depression, coma, respiratory arrest