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Pharmacology > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

Administration methods of local anesthetics

A

-topical -local/field -intravenous block -peripheral nerve -plexus (brachial, lumbar) -central neuralgia (epidural, spinal)

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2
Q

Which has a longer half life, mepivacaine or lidocaine?

A

Mepivacaine (> 1 hr)

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3
Q

Define frequency-dependent block

A

Local anesthetics require the Na+ channel to be open in order to block it; thus, the greater the activity of he nerve, the greater the chance it will be blocked

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4
Q

What is the duration of a local anesthetic dependent on?

A

How well it penetrates the axoplasm and reaches the Na+ channel

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5
Q

Lidocaine

A

Classification: local anesthetic & antiarrhythmic

MOI: blocking of Na+ channels

Uses: local and topical anesthetic, occasionally used to treat ventricular arrhythmias

Contraindications: known sensitivity to drug class, Adams stokes syndrome, severe SA, AV, or intraventricular heart block

Adverse effects: dose-related, CNS depression

Administered: IV, SC

Cross BBB? Yes

Elimination: metabolized by liver

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6
Q

Define local anesthetic

A

Drug that produces “reversible loss of sensation in an area of an animal’s body without loss of consciousness or alteration of CNS activity”

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7
Q

Mepivacaine

A

Classification: local anesthetic MOI: blocking of Na+ channels Uses: preferred local anesthetic used in horses: spinal, laryngeal, lower leg & intrathecal use Contraindications: known sensitivity to class of drugs, heart block Adverse effects: dose-related, CNS depression, cardiotoxicity, tissue edema at site of injection Administered: SC Cross BBB? Yes Elimination: metabolized by liver

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8
Q

What are the two types of local anesthetics?

A

Amino amides (most common) Amino esters (degraded by enzymes- plasma esterases)

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9
Q

If there is an “i” before the caine, the drug is an amide or ester?

A

Amide (e.g. Lidocaine, Bupivacaine, Mepivacaine)

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10
Q

Why is Bupivacaine not advised to be administered IV?

A

Due to cardiotoxicity

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11
Q

What is the general structure of most anesthetics?

A

Lipophilic end and hydrophilic end

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12
Q

The amount of local anesthetic that reaches the blood depends on which 4 things?

A
  1. The site of injection
  2. presence/absence of vasoconstrictors, the physical property of the drug, and the amount injected
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13
Q

Methemglobinemia is a rare potential side-effect of what local anesthetic?

A

Lidocaine

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14
Q

What is the effect of protein plasma binding on the effects of a local anesthetic?

A

If absorbed from the injection site into circulation, the drug must be free and non ionized

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15
Q

What is the mechanism of action of anesthetics?

A

They target sodium channels in excitable cells (Nav1 and Nax) and block conduction of these nerves (block action potential/pain signal)

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16
Q

Why are unmyelinated and thinly myelinated axons the major targets of anesthetics?

A

Because these are the axons that generate/carry pain signals

17
Q

Bupivacaine

A

Classification: local anesthetic MOI: blocking of Na+ channels Uses: local anesthetic, spinal & intrathecal use Contraindications: known sensitivity to class of drugs, heart block Adverse effects: dose-related, CNS depression, cardiotoxicitiy (> than lidocaine) Administered: SC, intrathecal, spinal Cross BBB? Yes Elimination: metabolized by liver

18
Q

True or False? Cocaine was the first utilized topical anesthetic in human medicine

A

True

19
Q

What is the name of the local anesthetic restricted to ophthalmic use?

A

Proparacaine

20
Q

What is the onset of action?

A

Time the local anesthetic takes a to produce blockade; dependent upon placement of drug, molecule, size, and pKa

21
Q

True or false? In order for local anesthetics to work, the sodium channel must be open

A

True

22
Q

Describe methemoglobinemia

A

-iron in hemoglobin is stabilized in ferric (Fe3+) form > O2 is unable to bind, results in hypoxia and death - Lidocaine is an oxidizer -can treat w/ methylene blue

23
Q

Unmyelinated axons are affected more/less quickly than the larger myelinated fibers?

A

More

24
Q

What is the potency of a local anesthetic related to?

A

Lipid solubility & pKA > promote penetration of drug to site of action

25
Q

What two systems do local anesthetics have effects on?

A

CNS (depression) and cardiovascular (decrease in force of contraction)

26
Q

The adverse effects to local anesthetics observed in patients are correlated to what?

A

The amount/concentration of the dose of local anesthetic given

27
Q

For myelinated nerves, at least ____ nodes of Ranvier must be blocked to produce the effect?

A

Two

Pharmacology (33 decks)

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