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NMSP 3 > Pharm: Local Anesthetics > Flashcards

Pharm: Local Anesthetics Flashcards

1
Q

Allergic reactions to what type of local anesthetics is most common due to metabolism to allergy-causing compounds?

How can you tell the type of local anesthetic based on its name?

A

Ester-type (i.e., benzocaine, cocaine, procaine, and tetracaine)

*Will only have one‘i’ in the name; while amides will have at least two ‘i’s

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2
Q

Which local anesthetics are more prone to hydrolysis and as a result generally have a shorter duration of action?

A

Ester-type

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3
Q

Use of which substances will reduce systemic absorption of local anesthetics and is useful for those drugs with intermediate or short durations of action (ie., prolongation of action)?

A

Vasconstrictors (i.e., epinephrine)

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4
Q

Which type of local anesthetic is widely distributed after IV bolus administration?

A

Amide-type

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5
Q

How does the metabolism of ester-type local anesthetics differ from the amide-type?

A
  • Ester-type are metabolized in plasma
  • Amide-type are metabolized in liver and then excreted in urine as charged substances (CYP450)
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6
Q

What is the MOA of local anesthetics?

Where is their receptor site located?

A

- Block voltage-gated Na+ channel currents and stop spread of AP’s across nerve axons

  • Receptor site is at inner vestibule of the sodium channel
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7
Q

What structural properties of some local anesthetics cause a faster rate of interaction with the sodium channel and more potent actions?

A

Smaller and more lipophilic

*Tetracaine, bupivacaine, and ropivacaine

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8
Q

How does fiber diameter and degree of myelination affect the action of local anesthetics?

List an example

A
  • Preferentially block small fibers
  • Myelinated nerves tend to become blocked before unmyelinated nerves of the same diameter

*Preganglionic B fibers are blocked before smaller unmyelinated C fibers

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9
Q

How does firing frequency affect the action of local anesthetics, which are preferntially blocked?

List an example

A
  • Those tha fire at higher frequenciesof depolarization are blockedfirst
  • i.e., type A delta and C fibers are blocked earlier than large A alpha fibers
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10
Q

Which is affected first by local anesthetics injected into a bundle of large mixed nerves (sensory or motor)?

A

Motor nerves

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11
Q

How does the position of sensory fibers within the extremites change from proximal to distal limbs?

A
  • Proximal sensory fibers are located in outer portion of nerve trunk (will be affected first by local anesthetic)
  • Distal sensory fibers are located in the core of the nerve (motor fibers will be affected first)
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12
Q

What is block anesthesia and its purpose?

A
  • Injection in major nerve trunks
  • Purpose is the anesthetize a region distal to the injection site
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13
Q

What is intravenous regional anesthesia (Bier block) used for?

How is it done?

A
  • Used for short surgeries (<60 min) involving UE and LE’s
  • IV injection of agent is placed in a distal vein while circulation of limb is isolated w/ a proximally placed tourniquet
  • Large doses of local anesthetic used; tourniquet remains in place to prevent high circulating drug levels causing systemic effects
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14
Q

Which local anesthetic potentiates the effect of NE on α-adrenergic receptors by blocking NET and results in localized vasoconstriction?

A

Cocaine

*Eliminates need for combining the drug w/ epinephrine

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15
Q

Epinephrine administration to prolong the action of local anesthetics should never be injected into what tissues?

What could this result in?

A
  • Those supplied by end arteries
  • Fingers, toes, nose, and penis
  • Vasocontriction could cause gangrene
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16
Q

What are the early signs of CNS toxicity caused by local anesthetics?

A

- Circumoral and tongue numbness

- Metallic taste

17
Q

High concentrations of local anesthetics in the CNS may have what adverse effects?

A
  • Nystagmus
  • Muscular twitching
  • Convulsions
  • Death by respiratory failure
18
Q

When large doses of local anesthetics are required premedication with parenteral _____________ can provide prophylaxis against CNS toxicity by raising the seizure threshold

A

Benzodiazepine (diazepam or midazolam)

19
Q

Undesired effects of local anesthetics on the CV system are the result of direct effects on ___________ and from indirect effects on the _____________

A

Undesired effects of local anesthetics on the CV system are the result of direct effects on cardiac and smooth muscle and from indirect effects on the ANS

20
Q

Local anesthetics block which ion channels in the heart and can have what adverse effects on the heart and blood pressure?

A
  • Block cardiac sodium channels
  • Decrease electrical excitability, conduction rate, force of contraction
  • Arteriolar dilation —> sytemic hypotension
21
Q

Cocaine is an exception to the local anesthetic effects on the heart, and instead can cause what?

A
  • Vasconstriction –> local ischemia
  • HTN
  • Cardiac arrhythmias
22
Q

Which local anesthetic is the most cardiotoxic due to its long duration of action?

A

Bupivacaine

23
Q

Which local anesthetic is a Class Ib antiarrhythmic?

A

Lidocaine

24
Q

What are the effects of Lidocaine on the heart?

A
  • Suppresses automaticity of condunction tissue by increasing electrical stimulation threshold of ventricle, His-Purkinje system, and spontaneous depolarization of the ventricles during diastole
  • Blocks both the initiation and conduction of nerve impulses by decreasing the neuronal membrane’s permeability to sodium ions, which results in inhibition of depolarization w/ resultant blockade of conduction
25
Q

What is Benzocaine used for?

A
  • Only as topical agent
  • Dermatologic conditions, hemorrhoids, premature ejaculation, and as anesthetic lubricant (i.e., NG an endoscopic tubes/catheters)
26
Q

Bupivacaine has a tendency to provide more of a (sensory or motor) block?

A

Sensory

27
Q

Cocaine, as a local anesthetic, is used primarily how?

A

Topical anesthtic of the upper respiratory tract

28
Q

What is Lidocaine used for clinically?

A
  • Alternative choice for pt’s with allergy to ester-type local anesthetics
  • Antiarrythmic agent

*Faster, more intense, longer acting, and more extensive anesthesia than an equal dose of Procaine

29
Q

What is Procaine used for clinically?

A

Only for infiltration anesthesia (local anesthesia produced by injection of the anesthetic solution directly into the area of terminal nerve endings)

30
Q

Which local anesthetic is metabolized to a para-aminobenzoic acid, which inhibits the action of sulfonamide antibiotics?

A

Procaine

31
Q

Low concentrations of local anesthetics may produce which adverse effects on the CNS?

A
  • Sleepiness (*CIS Q)
  • Light-headedness
  • Visual and auditory disturbances
  • Restlessness
32
Q

Which local anesthetic is for surface use only?

A

Benzocaine

*i.e., someone comes in with bad road rash or something

33
Q

Which 3 local anesthetics have long durations of action?

A
  1. Bupivacaine
  2. Ropivacaine
  3. Tetracaine
34
Q

Which local anesthetic has a short duration of action; used only for infiltration anesthesia?

A

Procaine

NMSP 3 (20 decks)

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