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41 Cards in this Set

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  • Back
Are local anesthetics weak acids or bases?
Bases
Is the aromatic ring in local anesthetics lipophilic or hydrophilic?
Lipophilic
What are the 2 types of intermediate groups on local anesthetics?
1. Ester

2. Amide
What is the easiest way to remember if a local anesthetic is an amide or ester?
Amides have TWO "I"s

Ex: Bupivicaine
What is the voltage when continued stimulation is no longer needed and local processes can lead to a complete AP?
Threshold potential
What are the 3 states of the Na channel?
Open, Closed, Inactive
What is the MOA of local anesthetics?
Binds to the internal membrane of the NaCh and blocks the permeability of Na
In what 2 NaCh states do local anesthetics bind?
Open and Inactive
Nerves that have what characteristic are more easily blocked?
Nerves that fire more frequently
Why does a local anesthetic not work in the case of a tooth abscess?
Because the abscess is acidic and therefore local anesthetic is not as effective
What are 5 effects that local anesthetics have on the AP?
1. Decrease AP amplitude

2. Slow rate of depolarization

3. Increase firing threshold

4. Slow impulse conduction

5. Prolong the refractory period
In the blood, what do local anesthetics bind to?
Alpha1-glycoprotein and albumin
In which organ is there considerable first pass uptake of local anesthetics?
Lung
What are the 2 mechanisms by which local anesthetics enter the blood stream?
1. Direct Injection

2. Absorption
What are the 3 phases of distribution of local anesthetics?
1. Alpha Phase

2. Beta phase

3. Gamma Phase
What occurs in the alpha phase?
Rapidly distributed to well-perfused tissue

Ex: Brain, heart, Liver
What occurs in the beta phase?
Less perfused or slow equilibrating tissue

Ex: Muscle, Fat
What occurs in the gamma phase?
Clearance representing metabolism and excretion
Which organs are at greatest risk of toxicity from overdose of a local anesthetic?
Brain, Heart, and Liver
What enzyme metabolizes ester local anesthetics?
Pseuodocholinesterase
What is the breakdown product of ester metabolism and what is its significance?
Para-aminobenzoic acid (PABA)

It's an ALLERGEN
Where are amides broken down?
ER of hepatocytes
A patient with end state liver disease is most susceptible to what type of local anesthetic?
Amides (because broken down in liver)
What characteristic of a local anesthetic corresponds to its potency?
Lipid Solubility

More Soluble = More potent
What characteristic of local anesthetics corresponds to duration?
Lipid Solubility

More soluble = greater duration
What property of local anesthetics dictates the speed of onset?
pKa

pKa closer to BODY'S pH (7.4) = faster onset

Because at that pKa anesthetics are unionized and can cross membrane
A newly discovered local anesthetic has a pKa of 7.4, what % of it is unionized in the plasma?
50% (H-H equation)
Why are esters usually put in OC drugs?
Because they are metabolized quickly so if misused, less likely to cause OD
What are the 2 types of local anesthetic toxicity?
1. CNS

2. Cardiovascular
Why are convulsions seen in LA toxicity?
Because inhibitory neurons are more susceptible that excitatory
Why is cardiovascular toxicity seen?
Because of interference with calcium signaling
In terms of toxicity, why is Bupivicaine an exception?
Cardiac dysrhythmias are seen at subconvulsant doses of bupivicaine
Which isomer of Bupivicaine is 40x more cardiotoxic?
D isomer
What is given as an antidote in the case of cardiac toxicity due to local anesthetics?
Intralipid
What are the effects of local anesthetics on vascular smooth muscles at

1. Low Concentrations
2. High Concentration
Low = vasoconstriction

High = Vasodilation
What is the exception to the rule that high concentrations give vasodilation?
Cocaine
Which anesthetics are prepared soley as the S isomer and are much less cardiotoxic than bupivicaine?
1. Ropivacaine

2. Levobupivicaine
What is the snesory nerve blocking mecanisms of levobupivicaine?
Same as bupivicaine
Which anesthetic is metabolized to alpha-orthotoludine and in doses greater than 600mg results in methemoglobinemia?
Prolocaine
What is the duration and onset of Lidocaine?
rapid onset, medium duration
What is lidocaines other use?
Anti-arrhythmic