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ARCHIVED: Pharmacology for Nurse Anesthesia > Exam 1: Pharmacokinetics/Pharmacodynamics > Flashcards

Exam 1: Pharmacokinetics/Pharmacodynamics Flashcards

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1
Q

Pharmacokinetics vs. pharmacodynamics:

A

Pharmacokinetics = “what the body does to a drug”

Pharmacodynamics = “what a drug does to the body”

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2
Q

Four components of pharmacokinetics:

A

Absorption
Distribution

Metabolism

Excretion

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3
Q

Three components of pharmacodynamics:

A

Mechanism of effect
Sensitivity

Responsiveness

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4
Q

Four commonly measured pharmacokinetic parameters of IV drugs:

A
  1. Elimination half-time
  2. Bioavailability
  3. Clearance
  4. Volume of distribution
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5
Q

Define bioavailability

A

How much of the drug administered is available at the site of action

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6
Q

Define volume of distribution

A

The volume that the drug is able to distribute into

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7
Q

Compartments in the two compartment model:

A

Central

Peripheral

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8
Q

Define central compartment:

A

Highly perfused tissues: kidney, liver, lungs, heart, brain, vessels

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9
Q

What pathway does a drug take between the two compartments?

A

Introduced into central
Distributes into peripheral

Returns to central for clearance

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10
Q

What % of CO does the central compartment receive? What % of body mass does it represent?

A

75% of CO

10% of mass

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11
Q

What is the peripheral compartment?

A

The not highly perfused organs/tissues

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12
Q

What are the characteristics of the peripheral compartment?

A

Large volume

Extensive uptake of drug

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13
Q

What type of drugs will transfer easily between plasma and tissues?

A

Highly lipid soluble

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14
Q

How does aging affect the rate of transfer between compartments?

A

Decreases it, leading to greater plasma concentration

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15
Q

What causes a drug to leave the peripheral compartment?

A

Drop in plasma concentration below peripheral compartment concentration due to clearance

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16
Q

How are the duration of effect and elimination half-time related in lipophilic drugs?

A

Duration of effect much shorter than elimination half-time

Plasma concentration drops rapidly but drug is slow to leave tissues and get cleared

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17
Q

Why do large/repeat doses of a drug prolong duration of action?

A

Tissues become saturated so clearance depends on metabolism, not redistribution

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18
Q

What are the 3 and 4 compartment models?

A

3: vessel rich, muscle, fat & vessel-poor
4: vessel rich, muscle, fat, vessel-poor

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19
Q

Body mass and flood flow % for each compartment (vessel rich to vessel poor):

A

Body mass: 10%, 50%, 20%, 20%

Blood flow: 75%, 19%, 6%, <1%

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20
Q

Special function of lungs r/t drugs:

A

Serve as a reservoir for basic lipophilic drugs

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21
Q

Why does Fentanyl have two peaks?

A

Lungs sequester initially and then release

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22
Q

What type of drugs does the blood-brain barrier block?

A

Ionized, water-soluble drugs

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23
Q

Under what conditions can the blood-brain barrier be overcome?

A

Large doses of drug in patients with head injury or hypoxemia

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24
Q

What populations have weaker blood brain barriers?

A

Neonates

Elderly

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25
Q

Define biophase:

A

Site of action of drug, aka “effect site”

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26
Q

What is the rate constant of drug elimination from effect site?

A

ke0

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27
Q

How do we calculate Vd?

A

Vd = dose of IV drug / plasma concentration of drug

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28
Q

How does lipid solubility affect Vd? Why?

A

More lipid soluble = higher Vd

Lipid soluble drugs easily cross membranes to enter the peripheral compartment

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29
Q

How does protein binding affect Vd? Why?

A

More protein bound = lower Vd

If drug is bound to proteins, it cannot cross membranes and enter tissues

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30
Q

Why does coumadin have such a small therapeutic index?

A

High protein binding affinity; small changes in [plasma protein] lead to large changes in plasma levels

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31
Q

How does molecular size relate to Vd? Why?

A

Greater molecular size = smaller Vd

Larger molecules have a harder time crossing the membrane and stay in the plasma more

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32
Q

Elimination half-time

A

The time for the plasma concentration of the drug to decrease to 50% during the elimination phase (NOT the total amount of drug in the body)

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33
Q

How are elimination half-time and Vd related?

A

Directly proportional

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34
Q

How are elimination half-time and clearance related?

A

Inversely proportional

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35
Q

How are elimination half-time and drug dose related?

A

They are independent of each other

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36
Q

Define elimination half-life:

A

How long it takes for drug to leave the body by 50%

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37
Q

What occurs if dosing intervals are less than elimination half-time?

A

Drug accumulation

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38
Q

% of initial drug eliminated at each of the first 6 half-times:

A

50%
75%

  1. 5%
  2. 8%
  3. 9%
  4. 4%
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39
Q

Advantages of oral administration:

A

Convenient and economic

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40
Q

Disadvantages of oral administration:

A

Emesis
Destruction by gastric enzymes/acid

Irregular absorption with food/other drugs

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41
Q

What is the first-pass effect?

A

Drugs absorbed via GI system have to pass through the portal system/liver before systemic circulation and get metabolized

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42
Q

What is the advantage of sublingual/transmucosal administration?

A

Bypasses the liver and the first-pass effect

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43
Q

What are the advantages of transdermal administration?

A

Sustained therapeutic plasma concentration of drug

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44
Q

How does absorption occur for transdermal drugs?

A

Along sweat ducts and hair follicles

45
Q

What is the rate-limiting step for transdermal absorption?

A

Diffusion across stratum corneum

46
Q

Differences in proximal vs. distal rectal administration:

A

Proximal: portal system
Distal: caval system

47
Q

What is the advantage of IV administration?

A

Achieve therapeutic plasma levels precisely and rapidly

48
Q

How acidic/basic are most drugs?

A

Weak acids and bases

49
Q

Non-ionized drugs are usually (lipid soluble/non lipid soluble):

A

Lipid soluble

50
Q

Is the ionized or non-ionized fraction of a drug the active part?

A

Non-ionized

51
Q

How is the ionized fraction of a drug cleared?

A

By the kidneys, u nchanged

52
Q

Why are drugs with a high ionized fraction a bad idea for renal patients?

A

Ionized fraction of drugs passes out unchanged via kidneys

53
Q

What two factors determine the degree of ionization?

A
  • Dissociation constant (pK)

* pH of surrounding fluid

54
Q

Acidic drugs are highly ionized at an _______ pH.

A

Alkaline

55
Q

Describe ion trapping and an example:

A

Drug ends up in an acid/basic environment where it becomes ionized and unable to cross back over to equilibrate

Ex. LA accumulating in placenta

56
Q

Main three plasma proteins:

A
  • Albumin-acids
  • α 1 acid glycoprotein bases
  • Lipoproteins
57
Q

Which fraction of the drug (r/t protein binding) can cross membranes?

A

The free/unbound fraction

58
Q

How does protein binding affect Vd and effect?

A

Lower Vd

Lesser effect

59
Q

Name four drugs that are highly protein bound:

A

Warfarin
Propranolol

Phenytoin

Diazepam

60
Q

Define clearance:

A

Volume of plasma cleared of drug by metabolism and excretion

61
Q

Define first-order kinetics:

A

Rate of elimination increases with more of the drug

A constant fraction per unit of time is eliminated

62
Q

Most drugs display ______-order kinetics:

A

First-order

63
Q

Define zero order kinetics:

A

A constant amount of drug is eliminated per unit time

64
Q

What are three common drugs that exhibit zero order kinetics?

A

ETOH
ASA

Dilantin

65
Q

Define hepatic clearance:

A

Ratio of hepatic blood flow to hepatic extraction of drug

66
Q

What is perfusion-dependent elimination?

A

Hepatic extraction ratio > 0.7

Clearance of drug depends on hepatic blood flow

67
Q

Relationship between blood pressure and hepatic extraction ratio:

A

If ratio is > 0.7, drug is perfusion dependent; low BP means slower clearance

68
Q

Define capacity-dependent elimination:

A

Hepatic extraction ratio is will not change clearance

Decrease in protein binding -or- increase in enzyme activity will increase hepatic clearance

69
Q

Most important organ for elimination of unchanged drugs or metabolites:

A

Kidneys

70
Q

Which type of drugs are most efficiently excreted by kidneys?

A

Water soluble compounds

71
Q

Highly lipid soluble drugs in the kidney:

A

Get reabsorbed so little to no unchanged drug is excreted

72
Q

Define drug metabolism:

A

Biotransformation to convert pharmacologically active, lipid soluble drugs into water soluble and often inactive drugs

73
Q

Increased water solubility _____ the Vd for a drug and _____ its renal excretion.

A

Decreases; increases

74
Q

Four pathways of metabolism:

A
  1. Oxidation
  2. Reduction
  3. Hydrolysis
  4. Conjugation
75
Q

What occurs during phase I of metabolism?

A

Oxidation, reduction, or hydrolysis

76
Q

What occurs during phase II of metabolism?

A

Conjugation of drug or metabolite with endogenous substance to form water-soluble compound

77
Q

Sites of drug metabolism in the body (5):

A

Plasma
Kidneys

Lungs

GI Tract

Liver

78
Q

What is the primary site for drug metabolism? What substance is responsible for metabolism there?

A

Liver; hepatic microsomal enzymes

79
Q

What is an example of a drug metabolized in the plasma?

A

Succinylcholine (by plasma esterases)

80
Q

Where are hepatic microsomal enzymes located?

A

In the hepatic smooth ER

81
Q

What are the protein enzymes that frequently metabolize drugs collectively called?

A

Cytochrome P-450

82
Q

What are the six CYP isozymes in the Cytochrome P-450 system?

A

CYP1A2
CYP2C9

CYP2C19

CYP2D6

CYP2E1

CYP3A

83
Q

Define enzyme induction:

A

Increased enzymatic activity or enzyme concentration, resulting in increased elimination of a drug

84
Q

What class of drugs were mentioned as huge enzyme inducers?

A

Barbiturates

85
Q

How do nonmicrosomal enzymes typically work?

A

By conjugation and hydrolysis

Lesser extent via redox

86
Q

Where are nonmicrosomal enzymes located?

A

Liver (mostly)
Plasma

GI tract

87
Q

Which enzymes hydrolize drugs with ester bonds? What are two examples of these drugs?

A

Nonmicrosomal enzymes

Succinylcholine, esmolol

88
Q

Which type of enzymes can be induced?

A

Hepatic microsomal enzymes

89
Q

By what mechanism do most drugs exert their effect?

A

Interaction with cell membrane receptors

90
Q

How do pts on beta-blockers adapt?

A

Upregulate (increase) the number of beta receptors

91
Q

Define the state of receptor activation theory:

A

Non-activated receptors are converted to active by the drug

92
Q

What is the receptor occupancy theory?

A

The more receptors occupied by the drug, the greater the effect

93
Q

Ex. of a nonreceptor drug action:

A

Antacids neutralize gastric acid by direct action

Chelating drugs form bonds with metallic cations

94
Q

Agonist drugs work by:

A

Mimicking cell signalling molecules and activating the same receptors

95
Q

Antagonist drugs work by:

A

Binding to same receptors as cell signals WITHOUT activating the receptor, therefore blocking the signaling molecules

96
Q

How much does the chemical structure of a drug affect its affinity for a receptor?

A

Small changes in structure can dramatically change effect

97
Q

Define racemic:

A

1/2 R isomer, 1/2 L isomer

98
Q

Enantomerism can be produced by:

A

sp3 hybridized carbon atoms

99
Q

Define efficacy:

A

The ability of a drug to produce the desired therapeutic effect

100
Q

Define potency:

A

The relationship between the effect of a drug and the dose necessary to achieve that effect

101
Q

Quickness to effect and amount needed to effect: which is efficacy? Which is potency?

A

Efficacy: quickness
Potency: amount

102
Q

Define ED50 and LD50:

A

ED50 is the dose effective in 50% of people

LD50 is the dose lethal in 50% of people

103
Q

Define therapeutic index:

A

The ratio of LD50 to ED50

104
Q

Define hyperreactivity:

A

An unusually low dose of drug produces the expected effect

105
Q

Define hypersensitivity:

A

Allergy

106
Q

Define additive effect:

A

A second drug acting with the first will produce effect equal to the sum of both

1+1=2

107
Q

Define synergistic effect:

A

Two drugs interact to produce an effect greater than their sum

1+1=3

108
Q

What type of combined effect do Fentanyl and Versed have?

A

Synergistic, esp. on respiratory rate

ARCHIVED: Pharmacology for Nurse Anesthesia (20 decks)

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