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Flashcards in Local Anesthetics Deck (27):
1

Administration methods of local anesthetics

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

2

Which has a longer half life, mepivacaine or lidocaine?

Mepivacaine (> 1 hr)

3

Define frequency-dependent block

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

4

What is the duration of a local anesthetic dependent on?

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

5

Lidocaine

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

6

Define local anesthetic

Drug that produces "reversible loss of sensation in an area of an animal's body without loss of consciousness or alteration of CNS activity"

7

Mepivacaine

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

8

What are the two types of local anesthetics?

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

9

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

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

10

Why is Bupivacaine not advised to be administered IV?

Due to cardiotoxicity

11

What is the general structure of most anesthetics?

Lipophilic end and hydrophilic end

12

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

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

13

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

Lidocaine

14

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

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

15

What is the mechanism of action of anesthetics?

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

16

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

Because these are the axons that generate/carry pain signals

17

Bupivacaine

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

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

True

19

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

Proparacaine

20

What is the onset of action?

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

21

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

True

22

Describe methemoglobinemia

-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

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

More

24

What is the potency of a local anesthetic related to?

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

25

What two systems do local anesthetics have effects on?

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

26

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

The amount/concentration of the dose of local anesthetic given

27

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

Two