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36 Cards in this Set

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Local anesthetics do what to the following:

- Rate of depolarization
- Height of AP
- Rate of AP rise
- Axonal conductance
- Propagation of AP
- Resting Membrane Potential
- Threshold Potential
Decrease
Decrease
Decrease
Slowed
Prevention

DOES NOT ALTER

Increase
Generalized mechanism for local anesthetics.
Blocks the sodium channel on the inside of the membrane
T/F - Local anesthetics alter potassium channels.
False - only act on sodium channels.
What is membrane expansion theory?
Local anesthetics absorb in the membrane and physically squeeze the channel together, preventing sodium from going through.
T/F - In order for drugs to pass through the membrane, they should be ionized.
False - non-ionized for passability.
What extracellular pH environment would be more favorable for local anesthetics and why?

What happens once inside?
Basic pH b/c higher ratio of non-ionized form will get into membrane.

Once in membrane, will become ionized so that it will block sodium channels.
Local anesthetics bind most tightly to what sort of sodium channels?
Inactivated state
Which is more sensitive to local anesthetic, resting nerve or stimulated nerve?
Stimulated nerve
What are the main factors involved in action of local anesthetics? x2
Diffusion through the nerve sheath

Binding at receptor site
What are the factors affecting the action of local anesthetics?
pKa
pH
Lipophilicity
Protein
Vasodilator activity
How does pKa effect local anesthetics?
Lower the pKa, the faster the onset
How does extracellular pH affect local anesthetics?
Higher the extracellular pH, the more unionized forms will cross membrane.
How does lipophlicity affect local anesthetics?
Higher the oil:water coefficient (lipophilicity), the stronger the potency
How does protein binding affect local anesthetics?
Higher the protein binding, the longer the duration of action.
Greater vasodilator activity means what for:

- Blood flow
- Removal of anesthetic
- Anesthetic potency
- Anesthetic duration
Increase

Rapid

Decrease

Decrease
Describe the anesthetic factors each has an effect on:

- pKa
- pH
- Lipophilicity
- Protein binding
- Vasodilator activity
Onset
Onset
Potency
Duration
Potency and Duration
Describe the types of sensory blockade by local anesthetics in order of first to last.
1. Pain
2. Cold
3. Warm
4. Touch
5. Deep Pressure
What is the effect of local anesthetics to:

- Cardiovascular system? x2
- CNS
- Neuromuscular junction
- Smooth muscle
Direct depression of cardiac effect
Vasodilation of peripheral vascular system.

CNS stimulation followed by depression

Blocks transmission

Relaxation of bronchial, uterine, and GI
What does a vasoconstrictor do to the absorption of local anesthetics?
Reduces absorption.
T/F - Local anesthethics can cross BBB.
True
What does cocaine do to the cardiovascular system?
Vasoconstriction
What are the two classes of local anesthetics and where/how are they metabolized?
Esters -

to PABA via plasma pseudocholinesterase

Amides

in liver, N-dealkylation and hydrolysis
List the ester local anesthetics. x4
Cocaine

Procaine

Chlorocaine

Tetracaine
What is the safest ester local anesthetic? and why?
Chloroprocaine

b/c lowest toxicity
Which ester local anesthetic is useful in the eye?
Tetracaine
What is the most widely used local anesthetic?
Lidocaine (Amide class)
What is the most potent local anesthetic?
Tetracaine
1
4
16

1
1
4
4
1
Standard of 1 for Procaine and Lidocaine
Slow
Rapid
Slow

Rapid
Slow
Slow
Slow
Slow
Onset
Standard (45 - 60)
Shorter (30 - 45)
Longer (60 - 180)

Standard (60 - 120)
Slightly Longer (90 - 180)
Much Longer (240 - 480)
Much Longer (240 - 280)
Same as standard
Standard is Procaine (45 - 60 min)

Standard is Lidocaine (60 - 120 min)
Slow
Rapid
Slow

Rapid
Slow
Slow
Slow
Slow
Onset
500
600
100

300
300
175
300
400
dosage
What surface local anesthetic is widely used? What problem is associated with it?
Benzocaine

Risk of methemoglobinemia
Which surface local anesthetic is useful in eye?
Proparacaine
The use of topical anesthetics always carries what risk?
System toxic reactions
The toxicity of local anesthetics depends on what?
Balance between rate of absorption and rate of elimination.