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Pharmacology > principles of local anesthesia > Flashcards

principles of local anesthesia Flashcards

1
Q

definition and historical background of cocaine and halsted

A

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

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2
Q

ester vs amide mechanism

A

all local anesthetics consist of three principle components

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

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3
Q

the three principle components of local anesthesia

A

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

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4
Q

amide group

A

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

lidocaine 
mepivicaine
bupivicaine
etidocaine
prilocaine
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5
Q

ester group

A

cocaine
procaine
chloroprocaine
tetracaine

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6
Q

Antieplileptic drugs with local anesthetic activity

A

phenytoin, carbamazepine, valproic acid

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7
Q

pharmacological profile of each local anesthetic affects its action

A

ionization constant (pKa) determines onset

lipid solubility determines drug potency

protein binding and vasodilation determine duration of activity.

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8
Q

at ph 7.4

A

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.

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9
Q

henderson hasselbach

A

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

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10
Q

lipid solubility

A

the higher the lipid solubility the higher the potency.

compound with high lipid solubility has a high protein binding

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11
Q

protein binding

A

the greater the protein binding, the longer the duration.

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12
Q

vasodilation

A

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

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13
Q

Vasoconstrictors

A

to counteract vasodilation

Either epinephrine or levonordefrin added to LA

 Decrease absorption
 Increase duration
 Reduce systemic toxicity
 Reduce bleeding
 Could have adverse effects
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14
Q

what is used to reverse LA with vasoconstrictor?

A

phentolamine

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15
Q

metabolism of local anesthesia (ester group)

A

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

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16
Q

metabolism of local anesthesia (amide group)

A

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

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17
Q

acquired methemoglobinemia

A

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?

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18
Q

VC on CVS

A

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

19
Q

allergy

A 
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
20
Q

half life

A

the shorter the half life: minimize systemic impact

longer half life: manage post-operative pain

21
Q

what does vasoconstrictors do?

A

they decrease absorption.

22
Q

pka and onset

A

the lower the pka, the faster the onset

23
Q

whats the point of vasoconstriction?

A

to minimize systemic toxicity

24
Q

calculating maximum dosages

A

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

25
Q

calculating the dose of local anesthesia per cartridge

A

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

26
Q

the volume in each cartridge is?

A

1.8 ml.

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

27
Q

what is the maximum recommended dose of epinephrine?

A

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

28
Q

calculating the dose of VC (vasoconstrictor) per cartridge

A

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

29
Q

lidocaine

A

gold standard-> 50 percent us market share

30
Q

articaine

A

relatively new 40% US market share

31
Q

mepivicaine

A

for patient can not take epinephrine

32
Q

prilocaine

A

without and with low (epi), DISCONTINUED

33
Q

Bupivicaine

A

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

34
Q

formulation of lidocaine

A 
Water: vehicle
 HCl: improve solubility
 NaOH: adjust pH
 Editate disodium: adjust pH
 NaCl: adjust tonicity
 Epinephrine: vasoconstrictor
 Metabisulfite: antioxidant
 Methylparaben: antimicrobial
35
Q

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

A

metabisulfite

36
Q

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

A

methylparaben

37
Q

local anesthetic administration INFILTRATION

A

deposited near small terminal nerve endings

38
Q

local anesthetic administration FIELD BLOCK

A

deposited near larger terminal nerves branches

39
Q

local anesthetic administration NERVE BLOCK

A

deposited close to a main nerve trunk.

40
Q

drug interactions

A

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

41
Q

alternative drugs to local anesthesia (Diphenhydramine):

A

antihistamines

Mechanism of action unknown

42
Q

alternative drugs to local anesthesia (Saxitoxin)

A

paralytic shellfish toxins
Block voltage-gated sodium channel

cant get rid of them by cooking, thats a problem

43
Q

Alternative Drugs to Local Anesthetics ( Tetrodotoxin)

A

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

Pharmacology (11 decks)

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