principles of local anesthesia

Question 1

definition and historical background of cocaine and halsted

Answer 1

coca leaf–>cocaine–>dentistry

peru–>europe—>USA

william halsted was the first person to inject cocaine for anesthesia in dental procedure in 1884

in 1905, Alfred Einhorn and his associates reported their discovery of procaine, an ester based synthetic Local anesthesia

Question 2

ester vs amide mechanism

Answer 2

all local anesthetics consist of three principle components

local anesthetics are organic, basic substances and carry the suffix-caine

Question 3

the three principle components of local anesthesia

Answer 3

aromatic ring, intermediate linkage (ester, amide), terminal amine

Question 4

amide group

Answer 4

all amide local anesthetics have 2 “i” in their names

lidocaine 
mepivicaine
bupivicaine
etidocaine
prilocaine

Question 5

ester group

Answer 5

cocaine
procaine
chloroprocaine
tetracaine

Question 6

Antieplileptic drugs with local anesthetic activity

Answer 6

phenytoin, carbamazepine, valproic acid

Question 7

pharmacological profile of each local anesthetic affects its action

Answer 7

ionization constant (pKa) determines onset

lipid solubility determines drug potency

protein binding and vasodilation determine duration of activity.

Question 8

at ph 7.4

Answer 8

all local anesthetic drugs exist in two forms: drug and Drug+

the free base bc lipopophilic can cross the membrane

the cation (ionic form is the active form) is unable to cross the membrane.

Question 9

henderson hasselbach

Answer 9

the lower the pka, results in more free base (drug)

Question 10

lipid solubility

Answer 10

the higher the lipid solubility the higher the potency.

compound with high lipid solubility has a high protein binding

Question 11

protein binding

Answer 11

the greater the protein binding, the longer the duration.

Question 12

vasodilation

Answer 12

vasodilation can cause faster absorption

with the exception of cocaine, all local anesthetics are vasodilators

vasodilation causes faster absorption and shorter duration of action.

the faster the absorption, the higher risk for systemic toxicity

VASODILATION IS NOT A FAVORED CHARACTERISTIC

Question 13

Vasoconstrictors

Answer 13

to counteract vasodilation

Either epinephrine or levonordefrin added to LA

 Decrease absorption
 Increase duration
 Reduce systemic toxicity
 Reduce bleeding
 Could have adverse effects

Question 14

what is used to reverse LA with vasoconstrictor?

Answer 14

phentolamine

Question 15

metabolism of local anesthesia (ester group)

Answer 15

Hydrolyzed in plasma by pseudocholinesterases
 Allergic reactions related to PABA (metabolite)
 1/3000 patients – atypical pseudocholinesterase

Question 16

metabolism of local anesthesia (amide group)

Answer 16

Primary site of metabolism is liver
 Prilocaine : metabolized in both liver and kidney
 Articaine : metabolized in both liver and plasma

Question 17

acquired methemoglobinemia

Answer 17

our rbc have fe 2+ but in this condtion its replaced to
Fe 3+. can bind to oxygen, but love it so much that wont release it to the tissue. so now hypoxia. will have condition known as cyanosis. acquired bc some are born with this.

mostly due to benzocaine, and prilocaine. the couneteract for this would be methyl blue?

Question 18

VC on CVS

Answer 18

In patients with significant CVD, the epinephrine usages may
need to be limited and even completely avoided
Levonordefrin is α-selective and more friendly on the heart

Question 19

allergy

Answer 19

Allergy to ester group is more common;
No injection, only topical application
 Allergy to amide is extremely unlikely
 Allergy to bisulfite which is used to
prolong the shelf life of vasoconstrictors
 Allergy to methylparaben which is used
to as an antimicrobial preservative

Question 20

half life

Answer 20

the shorter the half life: minimize systemic impact

longer half life: manage post-operative pain

Question 21

what does vasoconstrictors do?

Answer 21

they decrease absorption.

Question 22

pka and onset

Answer 22

the lower the pka, the faster the onset

Question 23

whats the point of vasoconstriction?

Answer 23

to minimize systemic toxicity

Question 24

calculating maximum dosages

Answer 24

always pick the smaller of the two, for the safety of your patients.

Question 25

calculating the dose of local anesthesia per cartridge

Answer 25

the concentration of drug in each cartridge is labeled as %. Need to convert it to mg/ml first

remember 1g=1,000 ml

basically multiply your perentage by 10.

so lets 0.5% then mulitply by 10 so the concentration is
5 mg/ml then multiply by 1.8. thats how much local anesthesia you have in each cartridge. YOU MUST KNOW HOW MANY CARTRIDGES ARE ALLOWED PER PATIENT

Question 26

the volume in each cartridge is?

Answer 26

1.8 ml.

The dose of drug/cart=concentration (mg/ml) *1.8 ml

Question 27

what is the maximum recommended dose of epinephrine?

Answer 27

0.2 mg for health patients. but for those with significant cardiovascular diseases, is reduced to 0.04mg instead of 0.2mg.

Question 28

calculating the dose of VC (vasoconstrictor) per cartridge

Answer 28

the concentration of VC is labeled as fold of dilution. Need to convert it to mg/ml first.

Question 29

lidocaine

Answer 29

gold standard-> 50 percent us market share

Question 30

articaine

Answer 30

relatively new 40% US market share

Question 31

mepivicaine

Answer 31

for patient can not take epinephrine

Question 32

prilocaine

Answer 32

without and with low (epi), DISCONTINUED

Question 33

Bupivicaine

Answer 33

very potent, long acting. used for epidural. not allowed for less than 12 year olds.

Question 34

formulation of lidocaine

Answer 34

Water: vehicle
 HCl: improve solubility
 NaOH: adjust pH
 Editate disodium: adjust pH
 NaCl: adjust tonicity
 Epinephrine: vasoconstrictor
 Metabisulfite: antioxidant
 Methylparaben: antimicrobial

Question 35

in lidocaine what is the substance that acts as an antioxidant?

Answer 35

metabisulfite

Question 36

in lidocaine what is the substance that acts as an antimicrobial?

Answer 36

methylparaben

Question 37

local anesthetic administration INFILTRATION

Answer 37

deposited near small terminal nerve endings

Question 38

local anesthetic administration FIELD BLOCK

Answer 38

deposited near larger terminal nerves branches

Question 39

local anesthetic administration NERVE BLOCK

Answer 39

deposited close to a main nerve trunk.

Question 40

drug interactions

Answer 40

Avoid using LA with Epinephrine in conjunction with
 Monoamine oxidase inhibitors (MAOI): potentiation
 Tricyclic antidepressants (TCAs): high blood pressure
 Antipsychotics: serious heart problem
 Digitalis glycosides: to much cardiac excitation
 Non-selective β-Blockers: acute hypertensive episode
 Cocaine: hypertensive crisis or cardiac dysrhythmia

All above interact with epinephrine

the sedatives dont
 Sedatives and opioids: respiratory depression

Question 41

alternative drugs to local anesthesia (Diphenhydramine):

Answer 41

antihistamines

Mechanism of action unknown

Question 42

alternative drugs to local anesthesia (Saxitoxin)

Answer 42

paralytic shellfish toxins
Block voltage-gated sodium channel

cant get rid of them by cooking, thats a problem

Question 43

Alternative Drugs to Local Anesthetics ( Tetrodotoxin)

Answer 43

an extremely potent toxin
found mainly in the liver and sex organs
of some fish, such as puffer fish
Block voltage-gated sodium channel