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Pharm > Local Anesthetics > Flashcards

Local Anesthetics Flashcards

1
Q

LA consists of a ______ & ______ portion separated by a connecting hydrocarbon chain.

A

Lipophilic; hydrophilic

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2
Q

LA are poorly soluble in water and are marketed as water soluble _____________

A

Hydrochloride salts

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3
Q

These hydrochloride salt solutions contribute to the ________ of the LA

A

Stability

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4
Q

Substituting a butyl group for the amine group on the benzene ring of procaine results in?

A

Tetracaine

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5
Q

Compared to procaine, tetracaine is more ____________. _____ times more potent, and has a _______________ duration corresponding to a _______ fold decrease rate of metabolism

A

Lipid soluble;
10 x;
Longer duration;
4 -5

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6
Q

The ________ of bupivacaine and Mepivacaine appear to be less toxic than the commercially available racemic mixtures of the LA.

A

S enantiomers

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7
Q

The S enantiomers are considered to produce less ________ & _______ than racemic mixtures or the R enantiomers of LA

A

Neurotoxicity; cardiotoxicity

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8
Q

What 2 LA are available for clinical use as racemic mixtures (50:50) of the enantiomers?

A

Mepivacaine & Bupivacaine

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9
Q

What 4 LA are chiral drugs that may have S or R configurations?

A

Mepivacaine, Bupivacaine, Ropivacaine, & Levobupivacaine

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10
Q

Halogenation of procaine to chloroprocaine results in ___________ increase in hydrolysis rate of chloroprocaine by ______________

A

3-4 fold; plasma cholinesterase

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11
Q

Etidocaine resembles lidocaine but has a _____ increase in lipid solubility and 2-3 fold increase in ________.

A

50 fold; duration of action

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12
Q

________ is 35 times more lipid soluble and has a potency and duration of action ____ times that of Mepivacaine

A

Bupivacaine; 3-4

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13
Q

Drugs such as _______, _______, & _______ have been incorporated into liposomes to prolong the duration of action and decrease toxicity

A

Lidocaine, tetracaine, bupivacaine

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14
Q

Bupivacaine extended release liposome injection has been approved by the FDA for local infiltration of anesthesia and for _______

A

Hemorrhoidectomy and bunionectomy

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15
Q

LA binds to specific sites in ____________ channels

A

Voltage gated Na

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16
Q

LA blocks ______ current reducing excitability of _____, ______, or ______ tissue

A

Na ion; neuronal, cardiac, CNS

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17
Q

LA prevents transmission of nerve impulses (conduction blockade) by inhibition passage of __________________ in nerve membranes

A

Na ions through ion-selective Na channels

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18
Q

A specific receptor for LA molecules

A

Na channel

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19
Q

Describe how action potential is not propagated d/t Na ion channel

A

Failure of Na ion channel permeability to increase slows rate of depolarization such that the threshold potential is not reached, and the AP is not propagated (LA do NOT alter the resting membrane potential or threshold potential)

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20
Q

Increased sensitivity _________________ may be present during pregnancy

A

(More rapid onset of conduction blockade)

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21
Q

Name 3 esters from table 10-1

A

Procaine, Chloroprocaine, & tetracaine

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22
Q

Name 2 rapid onset LA from table 10-1

A

Chloroprocaine, Lidocaine

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23
Q

Which LA has the greatest protein binding

A

Levobupivacaine

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24
Q

LA are weak ______

A

Bases

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25
Q

At physiologic pH _____ of LA exists in a lipid soluble non ionized form

A

<50%

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26
Q

Describe why LA have poor quality when injected into an acidic infected area

A

Acidosis in the environment further increases ionized fraction of the drug and cannot cross the lipid membrane into the cell

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27
Q

What 4 characteristics of LA effect the absorption of the LA from its site of injection into the systemic circulation?

A

1) site of injection;
2) dosage;
3) use of Epinephrine;
4) pharmacologic characteristics of the drug

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28
Q

Name 3 LA the lungs are able to extract from the circulation

A

Lidocaine, Bupivacaine, & Prilocaine

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29
Q

Bupivacaine’s first-pass pulmonary extraction is _________

A

Dose dependent

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30
Q

Impairs bupivacaine extraction by the lungs

A

Propranolol

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31
Q

Propranolol decreases plasma clearance of?

A

Lidocaine & bupivacaine

32
Q

_____ LA are not available to cross the placenta in significant amounts d/t their rapid hydrolysis

A

Ester

33
Q

______ in the fetus can result in accumulation of LA molecules in the fetus call ___________

A

Acidosis; ion trapping

34
Q

Describe the LA limited renal excretion

A

It has poor water solubility and limits excretion to <5% (exception is cocaine)

35
Q

Which LA has a 10-12% unchanged drug recovery in the urine?

A

Cocaine

36
Q

Metabolism of Amide LA is primarily located where?

A

In the liver by microsomal enzymes

37
Q

List the Amides that undergoes the most, intermediate, and slowest metabolism.

A

Most: Prilocaine;
Intermediate: Lidocaine & Mepivacaine;
Slowest: Etidocaine, bupivacaine, & ropivacaine

38
Q

Which has the slower metabolism Ester or Amide?

A

Amide

39
Q

The principle metabolic pathway of Lidocaine is:

A

Oxidative dealkylation in the liver to monoethylglycinexylidide followed by hydrolysis of this metabolite to xylidide

40
Q

What explains monoethylglycinexylidide’s ability to protect against cardiac dysrhythmias?

A

Long elimination half-time

41
Q

What metabolite is lidocaine finally hydrolyzed into and what is its cardiac protection percentage against dysrhythmias?

A

Xylidide; 10%

42
Q

How does liver dz or decreases in hepatic blood flow (during anesthesia) effect lidocaine elimination?

A

Decreases rate of metabolism of lidocaine

43
Q

Describe Prilocaine’s association w/ methemoglobinemia & the drug/dose of the reversal.

A

When doses of Prilocaine > 600 mg, there may be sig methemoglobinemia (3-5 g/dL) to cause the pt to appear cyanotic, and O2-carrying capacity is decreased.
Reversal: methylene blue 1-2 mg/kg IV over 5 min

44
Q

In contrast to lidocaine, _________ lacks vasodilator activity

A

Mepivacaine

45
Q

Is an alternate selection when addition of epi to the LA solution is not recommended

A

Mepivacaine

46
Q

Compare clearance and elim h/t of ropivacaine and bupivacaine

A

Clearance of ropivacaine is higher than that determined for bupivacaine and its elim h/t is shorter

47
Q

Which LA is slowest eliminated amide derivatives

A

Dibucaine

48
Q

Dibucaine is known for its ability to?

A

Inhibit pseudocholinesterase by more than 80%

49
Q

Atypical plasma cholinesterase s account for prolonged effects and toxicity of drugs such as?

A

Chloroprocaine and cocaine

50
Q

What are the ways ester LA can be metabolized?

A

Hydrolysis by cholinesterase enzyme

51
Q

What explains tetracaine’s persistent anesthetic effect in a spinal?

A

CNS contains little to no cholinesterase enzyme, therefore subarachnoid placement will cause anesthesia to persist until the drug has been completely absorbed into systemic circulation

52
Q

What is unique about benzocaine?

A

Weak acid so only exists in non ionized form at physiologic pH.
(Ideally used for topical anesthesia of mucous membranes)

53
Q

Cocaine is metabolized by?

A

Plasma and liver cholinesterase to water-soluble metabolites excreted in urine

54
Q

Cocaine may remain in urine up to?

A

24-36 hrs

55
Q

What is affect of alkalization of LA?

A

Shortens onset of neural blockade, enhances depth of sensory and motor blockade, and increases spread of epidural blockade.
Adding bicarb will speed onset of peripheral nerve block and epidural block by 3-5 min

56
Q

What is effect of addition of epi to lidocaine and Mepivacaine?

A

Produces vasoconstriction, which decreases systemic absorption by 20-30%, prolonging conduction blockade

57
Q

What is effect of addition of epi to bupivacaine?

A

Increases duration of conduction blockade but to lesser degree w/ reduction in systemic absorption by 10-20%

58
Q

Most LA possess intrinsic vasodilator properties except?

A

Ropivacaine

59
Q

Which would be more likely to cause allergic rxn ester or amides?

A

Esters d/t metabolites

60
Q

Is there a cross sensitivity b/w esters and amides?

A

No

61
Q

Plasma lidocaine concentrations that cause analgesia

A

1-5 mcg/mL

62
Q

Plasma lidocaine concentrations that cause myocardial depression

A

5-10 mcg/mL

63
Q

Plasma lidocaine concentrations that cause tinnitus

A

5-10 mcg/mL

64
Q

Plasma lidocaine concentrations that cause seizures

A

10-15 mcg/mL

65
Q

Plasma lidocaine concentrations that cause apnea

A

15-25 mcg/mL

66
Q

Plasma lidocaine concentrations that cause CV depression

A

> 25 mcg/mL

67
Q

Recommended adult dose of lidocaine w/ epi for regional anesthesia

A

7 mg/kg

68
Q

In tumescent liposuction the dose of lidocaine may range from?

A

35-55 mg/kg

69
Q

What drug can be used to treat cocaine induced myocardial ischemia?

A

NTG

70
Q

What is the caution with using beta blockers w/ cocaine overdose?

A

B-blockage accentuates coronary artery vasospasm in setting of acute cocaine OD. Associated w/ profound CV collapse & cardiac arrest unresponsive to CPR

71
Q

______ & _______ antagonize the blockade

A

Hypokalemia; hypercalcemia

72
Q

_____ fibers are least sensitive to the action of LA

A

C

73
Q

Blood flow ranking from highest to lowest

A

Intra-arterial/IV > tracheal > intercostal > caudal > paracervical > epidural > brachial plexus > sciatic/subarachnoid/femoral > subq
“In Time I Can Please Everyone But Susie & Sally”

74
Q

______ & ______ are metabolized to PABA associated w/ anaphylaxis

A

Procaine & benzocaine

75
Q

Rate of metabolism of amides (greatest to least)

A

Prilocaine > lidocaine > mepivacaine > ropivacaine > bupivacaine

Pharm (15 decks)

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