Local Anesthetics Flashcards

1
Q

What letter do all amides have?

A

Two I’s

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2
Q

What determines the lipid solubility of the drug?

A

The aromatic ring and hydrocarbon chain length

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3
Q

Do high or low lipid soluble drugs penetrate cells quicker?

A

High lipid solubility

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4
Q

Are amides or esters more stable overall?

A

Amides

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5
Q

What does the metabolism of esters result in? Amides?

A

Production of PABA for esters

Nothing really for amides, which is why they are more commonly used now

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6
Q

Are all locals weak or strong bases?

A

Weak base-so they exist as ionized and unionized

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7
Q

As pH increases (More basic), there is ____ ionized particles of LA

A

Less, meaning more LA will enter the cell

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8
Q

As pH decreases (more acidic) there is ____ ionized particles of LA in the cell

A

more

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9
Q

So if a patient is acidotic for some reason, how will that affect LAs?

A

They won’t be as effective

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10
Q

What is LAs MOA?

A

Reversibly bind to voltage gated Na channels. This blocks Na influx and AP and nerve conduction

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11
Q

What size of fibers are LAs more effective at blocking?

A

Small

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12
Q

Do myelinated or non myelinated fibers get blocked first?

A

myelinated

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13
Q

The loss of nerve function proceeds as ……

Put these in order: Loss of pain, temp, skeletal muscle, touch, and proprioception

A

Pain, temp, touch, proprioception, skeletal muscle tone

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14
Q

What type of fiber transmits pain and temp?

A

A delta, which is myelinated

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15
Q

What type of fiber transmits pain and postganglionic signals?

A

C, nonmyelinated

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16
Q

Explain in depth of LA block Na channels.

A

The LA exists in equilibrium as ionized and unionized outside the cell membrane. The unionized part can diffuse into the cell, then get ionized with H+ (or maybe others as well). It then binds to the receptor, blocking it.

17
Q

What is each Na channel comprised of?

A

A single alpha subunit containing a central ion conducting pores associated with accessory beta subunits

18
Q

What are the factors that control absorption and distribution of LAs?

A

Vascularity, protein binding (slowly metabolized)

19
Q

What is the biggest factor for duration of action?

A

Protein binding

Procaine is 6% protein bound and has a short duration of action wheras bupivacaine is 95% bound and has a long duration of action

20
Q

How much can LA duration of action be increased with coadministration of epi?

A

2X using 1:200,000 epi

21
Q

What is the metabolism of esters? Besides cocaine

A

Plasma cholinesterase

22
Q

How is cocaine metabolised?

A

Hydrolyzed in the liver

23
Q

How are amides metabolized?

A

Amidases

24
Q

What are the ADEs of LAs?

A

CNS-Excitation followed by depression and death due to respiratory depression
CV- Bradycardia, heart block, vasoldilation (hypotension)
Allergic reactions-More common with esters r/t PABA

25
Q

What are the contraindications to LAs?

A

Heart block, concurrent use if quinidine, flecainide, disopyramide, and procainamide, and prior use of amiodarone

26
Q

What are the three causes of possible LA toxicity

A

IV injection
Rapid absorption from vascular area
Overdose

27
Q

What are the factors that reduce toxicity?

A

Use smallest dose possible
Lower dosage on frail patients
Inject slowly and aspirate to ensure not in vessel
Add epi

28
Q

What is the max dose of epi to give with LA?

A

200mcg

29
Q

What area should we avoid using epi with the LA?

A

In areas with end arteries d/t possible development of necrosis due to prolonged hypoperfusion

30
Q

What is a unique characteristic of cocaine?

A

It produces localized vasoconstriction as well as anesthesia

31
Q

What two drugs are not good substitutes for cocaine?

A

Procaine and chloroprocaine

32
Q

Which LA has the potential to cause methemoglobinemia?

A

Benzocaine

33
Q

How long can bupivacaine blocks last?

A

Up to 24 hours

34
Q

What is the issue with prilocaine?

A

Can also cause methemoglobinemia

35
Q

What is unique about articaine?

A

It is technically an amide, but it contains an additional ester group that helps it to be metabolized quicker

36
Q

What is the most commonly used dental anesthetic?

A

Articaine

37
Q

What is the name for combination of LAs?

A

EMLA