Chapter 2: Pharmacology of Local Anesthetics

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1

One prime factor involved in the termination of action of local anesthetics used for pain control is their redistribution from the nerve fiber into the (...).

cardiovascular system (CVS)

2

All local anesthetics possess a degree of vasoactivity, most producing (...) of the vascular bed into which they are deposited.

dilation

3

(...) is the most potent vasodilator among local anesthetics.

procaine

4

(...) is the only local anesthetic that consistently produces vasoconstriction.

cocaine

5

Cocaine induces vasodilation by inhibiting (...) into tissue binding sites.

uptake of catecholamines

6

Local anesthetics are absorbed poorly, if at all, after (...) administration.

oral

*with the exception of cocaine.

7

In 1984 Astra Pharmaceuticals and Merck Sharp & Dohme introduced an analogue of lidocaine, (...), that is effective orally.

card image

tocainide hydrochloride

8

Topically applied local anesthetics can produce an anesthetic effect wherever there is no (...) present.

intact skin

9

(...) is a mixute of lidocaine and prilocaine capable of providing surface anesthesia of intact skin.

eutectic mixture of local anesthetics (EMLA)

10

What type of local anesthetics are the following?

  1. butacaine
  2. cocaine
  3. benzocaine
  4. piperocaine
  5. tetracaine

esters

11

What type of local anesthetics are the following?

  1. articaine
  2. bupivacaine
  3. lidocaine
  4. mepivacaine
  5. prilocaine

amides

12

(...) administration of local anesthetics provides the most rapid elevation of blood levels

intravenous

13

IV administration of local anesthetics is used clinically in the primary management of (...).

ventricular dysrhythmias

14

Once absorbed into the blood, local anesthetics are distributed throughout the body to all tissues; (...) organs initially have the highest anesthetic blood levels.

card image

highly perfused (e.g. brain, liver, kidneys)

15

(...) contains the greatest percentage of local anesthetic of any tissue or organ in the body.

skeletal muscle

*although it is not highly perfused, it constitutes the largest mass.

16

What three factors influence the blood level of the local anesthetic?

  1. rate of absorption
  2. rate of distribution
  3. rate of elimination
17

The rate at which a local anesthetic is removed from the blood is described as its (...).

elimination half-life

18

The elimination half-life is the time necessary for a 50% reduction in the blood level:

  1. one half-life represents a (...)% reduction
  2. two half-lives represents a (...)% reduction
  3. three half-lives represents a (...)% reduction
  4. four half-lives represents a (...)% reduction
  5. five half-lives represents a (...)% reduction
  6. six half-lives represents a (...)% reduction
  1. 50%
  2. 75%
  3. 87.5%
  4. 94%
  5. 97%
  6. 98.5%
19

Can local anesthetics cross the blood-brain barrier?

All local anesthetics readily cross the blood-brain barrier.

20

Can local anesthetics cross the placenta?

All local anesthetics readily cross the placenta and enter fetal circulation.

21

The significant difference between the two major groups of local anesthetics, the esters and the amides, is mean by which they are (...).

metabolized (biotransformation)

22

Ester local anesthetics are hydrolyzed in the plasma by the enzyme (...).

card image

pseudocholinesterase

23

The rate of hydrolysis of ester local anesthetic has an impact on the (...) of a local anesthetic.

potential toxicity

24

(...), the most rapidly hydrolyzed ester local anesthetic, is the least toxic.

chloroprocaine

25

(...), a slowly hydrolyzed ester local anesthetic, has the greatest potential toxicity.

tetracaine

26

Allergic reactions that occur (rarely) in response to ester local anesthetic are usually related to (...), which is a major metabolic product of many ester local anesthetics.

p-aminobenzoic acid (PABA)

27

(...) is a short-acting muscle relaxant commonly used during the induction phase of general anesthesia.

succinylcholine

28

Persons with (...) are unable to hydrolyze succinylcholine at a normal rate, resulting in the duration of apnea being prolonged.

herditary atypical pseudocholinesterase

29

An (...) implies that under no circumstance should the drug in question be administered to the patient.

absolute contraindication

30

A (...) means that the drug in question may be administered to the patient after careful weighing of the risk versus the potential benefit.

relative contraindication

31

The primary site of biotransformation of amide local anesthetics is the (...).

liver

32

(...) contains both ester and amide components, and undergoes metabolism in both the blood (primarily) and the liver.

articaine

33

Which two conditions represent relative contraindications to the administration of amide local anesthetic drugs?

  1. liver dysfunction (ASA class 4 or 5)
  2. heart failure (ASA class 4 or 5)
34

The (...) of certain local anesthetics can possess significant clinical activity if they are permitted to accumulate in the blood.

card image

biotransformation products

35

Due to its biotransformation products high doses of prilocaine may cause (...).

methemoglobinemia

36

A primary metabolite of prilocaine, (...), induces the formation of methemoglobin, which is responsible for orthotoluidine.

card image

orthotoluidine

37

The (...) are the primary excretory organ for both the local anesthetic and its metabolites.

kidneys

38

Which conditions represents a relative contraindication to the administration of all local anesthetic drugs?

renal disease (ASA class 4 or 5)

39

Most of the systemic actions of local anesthetics are related to their (...) in a target organ.

concentration

40

The quinoline derivative (...) has proved to be more potent than lidocaine, but does not adversely affect the CNS or CVS.

centbucridine

41

The major pharmacologic action of local anesthetics on the CNS is one of (...).

depression

42

Individual reactions to local anesthetics lie on a (...)-shaped curve.

bell-shaped curve

43

The “classic” overdose reaction to a local anesthetic is a generalized (...).

tonic-clonic convulsion

44

Epileptic patients possess hyperexcitable cortical neurons at a site within the brain where the convulsive episode originates, called the (...).

epileptic focus

45

Local anesthetics, by virtue of their depressant actions on the CNS, raise the seizure threshold by decreasing the (...).

excitability of neurons

46

A blood level of (...) μg/mL lidocaine appears to be the “dividing line” before signs of minor toxicity (i.e. drowsiness) occur.

4.0 μg/mL

47

At a normal arterial partial pressure of CO2, a lidocaine blood level between (...) μg/mL usually results in a convulsive episode.

7.5 to 10 μg/mL

48

When CO2 levels are increased, the blood level of the local anesthetic necessary for seizures (...), while the duration of the seizure (...).

  1. decreases
  2. increases
49

If anesthetic blood levels continue to rise, beyond the cessation of seizure activity (...) depression also occurs, culminating in (...).

  1. respiratory
  2. respiratory arrest
50

Local anesthetics produce clinical signs and symptoms of CNS excitation through selective blockade of (...) in the cerebral cortex.

inhibitory pathways

51

The cerebral cortex has pathways of neurons that are essentially (...) and others that are (...) normally maintained in a state of balance.

card image
  1. inhibitory
  2. facilitatory (excitatory)
52

At preconvulsant local anesthetic blood levels, balance is tipped in favor of excessive (...) input, leading to symptoms including tremor and slight agitation.

card image

facilitatory (excitatory)

53

At higher (convulsive) blood levels, (...) neuron function is completely depressed, allowing unopposed function of (...) neurons.

card image
  1. inhibitory
  2. facilitatory
54

In the final stage of local anesthetic action, both the facilitatory pathway and the inhibitory pathway are depressed, producing (...).

card image

generalized CNS depression

55

In the 1940s and 1950s the local anesthetic (...) was administered intravenously for the management of chronic pain and arthritis.

procaine

56

The local anesthetic (...) has long been used for its euphoria-inducing and fatigue-lessening actions.

cocaine

57

The major pharmacologic action of local anesthetics on the CVS is one of (...).

depression

58

Local anesthetics (...) the electrical excitability of the myocardium, (...) conduction rate, and (...) the force of contraction.

  1. decrease
  2. decrease
  3. decrease
59

Therapeutic advantage is taken of the depressant action of local anesthetics on the myocardium in management of (...).

dysrhythmias

60

(...), a chemical analogue of lidocaine, was introduced in 1981 as an oral antidysrhythmic drug because lidocaine is ineffective after oral administration.

tocainide

61

(...) is the only local anesthetic drug that consistently produces vasoconstriction at commonly used dosages.

cocaine

62

All injectable local anesthetics produce a peripheral (...) through (...) in the walls of blood vessels.

  1. vasodilation
  2. smooth muscle relaxation
63

The primary effect of local anesthetics on blood pressure is (...).

hypotension