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

Exam 1: Pharmacokinetics/Pharmacodynamics Flashcards

(108 cards)

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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
Define biophase:
Site of action of drug, aka "effect site"
26
What is the rate constant of drug elimination from effect site?
ke0
27
How do we calculate Vd?
Vd = dose of IV drug / plasma concentration of drug
28
How does lipid solubility affect Vd? Why?
More lipid soluble = higher Vd Lipid soluble drugs easily cross membranes to enter the peripheral compartment
29
How does protein binding affect Vd? Why?
More protein bound = lower Vd If drug is bound to proteins, it cannot cross membranes and enter tissues
30
Why does coumadin have such a small therapeutic index?
High protein binding affinity; small changes in [plasma protein] lead to large changes in plasma levels
31
How does molecular size relate to Vd? Why?
Greater molecular size = smaller Vd Larger molecules have a harder time crossing the membrane and stay in the plasma more
32
Elimination half-time
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)
33
How are elimination half-time and Vd related?
Directly proportional
34
How are elimination half-time and clearance related?
Inversely proportional
35
How are elimination half-time and drug dose related?
They are independent of each other
36
Define elimination half-life:
How long it takes for drug to leave the body by 50%
37
What occurs if dosing intervals are less than elimination half-time?
Drug accumulation
38
% of initial drug eliminated at each of the first 6 half-times:
50% 75% 87. 5% 93. 8% 96. 9% 98. 4%
39
Advantages of oral administration:
Convenient and economic
40
Disadvantages of oral administration:
Emesis Destruction by gastric enzymes/acid Irregular absorption with food/other drugs
41
What is the first-pass effect?
Drugs absorbed via GI system have to pass through the portal system/liver before systemic circulation and get metabolized
42
What is the advantage of sublingual/transmucosal administration?
Bypasses the liver and the first-pass effect
43
What are the advantages of transdermal administration?
Sustained therapeutic plasma concentration of drug
44
How does absorption occur for transdermal drugs?
Along sweat ducts and hair follicles
45
What is the rate-limiting step for transdermal absorption?
Diffusion across stratum corneum
46
Differences in proximal vs. distal rectal administration:
Proximal: portal system Distal: caval system
47
What is the advantage of IV administration?
Achieve therapeutic plasma levels precisely and rapidly
48
How acidic/basic are most drugs?
Weak acids and bases
49
Non-ionized drugs are usually (lipid soluble/non lipid soluble):
Lipid soluble
50
Is the ionized or non-ionized fraction of a drug the active part?
Non-ionized
51
How is the ionized fraction of a drug cleared?
By the kidneys, u nchanged
52
Why are drugs with a high ionized fraction a bad idea for renal patients?
Ionized fraction of drugs passes out unchanged via kidneys
53
What two factors determine the degree of ionization?
* Dissociation constant (pK) | * pH of surrounding fluid
54
Acidic drugs are highly ionized at an _______ pH.
Alkaline
55
Describe ion trapping and an example:
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
Main three plasma proteins:
* Albumin-acids * α 1 acid glycoprotein bases * Lipoproteins
57
Which fraction of the drug (r/t protein binding) can cross membranes?
The free/unbound fraction
58
How does protein binding affect Vd and effect?
Lower Vd | Lesser effect
59
Name four drugs that are highly protein bound:
Warfarin Propranolol Phenytoin Diazepam
60
Define clearance:
Volume of plasma cleared of drug by metabolism and excretion
61
Define first-order kinetics:
Rate of elimination increases with more of the drug A constant fraction per unit of time is eliminated
62
Most drugs display ______-order kinetics:
First-order
63
Define zero order kinetics:
A constant amount of drug is eliminated per unit time 
64
What are three common drugs that exhibit zero order kinetics?
ETOH ASA Dilantin
65
Define hepatic clearance:
Ratio of hepatic blood flow to hepatic extraction of drug
66
What is perfusion-dependent elimination?
Hepatic extraction ratio > 0.7 Clearance of drug depends on hepatic blood flow
67
Relationship between blood pressure and hepatic extraction ratio:
If ratio is > 0.7, drug is perfusion dependent; low BP means slower clearance
68
Define capacity-dependent elimination:
Hepatic extraction ratio is will not change clearance Decrease in protein binding -or- increase in enzyme activity will increase hepatic clearance
69
Most important organ for elimination of unchanged drugs or metabolites:
Kidneys
70
Which type of drugs are most efficiently excreted by kidneys?
Water soluble compounds
71
Highly lipid soluble drugs in the kidney:
Get reabsorbed so little to no unchanged drug is excreted
72
Define drug metabolism:
Biotransformation to convert pharmacologically active, lipid soluble drugs into water soluble and often inactive drugs
73
Increased water solubility _____ the Vd for a drug and _____ its renal excretion.
Decreases; increases
74
Four pathways of metabolism:
1. Oxidation 2. Reduction 3. Hydrolysis 4. Conjugation
75
What occurs during phase I of metabolism?
Oxidation, reduction, or hydrolysis
76
What occurs during phase II of metabolism?
Conjugation of drug or metabolite with endogenous substance to form water-soluble compound
77
Sites of drug metabolism in the body (5):
Plasma Kidneys Lungs GI Tract Liver
78
What is the primary site for drug metabolism? What substance is responsible for metabolism there?
Liver; hepatic microsomal enzymes
79
What is an example of a drug metabolized in the plasma?
Succinylcholine (by plasma esterases)
80
Where are hepatic microsomal enzymes located?
In the hepatic smooth ER
81
What are the protein enzymes that frequently metabolize drugs collectively called?
Cytochrome P-450
82
What are the six CYP isozymes in the Cytochrome P-450 system?
CYP1A2 CYP2C9 CYP2C19 CYP2D6 CYP2E1 CYP3A
83
Define enzyme induction:
Increased enzymatic activity or enzyme concentration, resulting in increased elimination of a drug
84
What class of drugs were mentioned as huge enzyme inducers?
Barbiturates
85
How do nonmicrosomal enzymes typically work?
By conjugation and hydrolysis | Lesser extent via redox
86
Where are nonmicrosomal enzymes located?
Liver (mostly) Plasma GI tract
87
Which enzymes hydrolize drugs with ester bonds? What are two examples of these drugs?
Nonmicrosomal enzymes Succinylcholine, esmolol
88
Which type of enzymes can be induced?
Hepatic microsomal enzymes
89
By what mechanism do most drugs exert their effect?
Interaction with cell membrane receptors
90
How do pts on beta-blockers adapt?
Upregulate (increase) the number of beta receptors 
91
Define the state of receptor activation theory:
Non-activated receptors are converted to active by the drug
92
What is the receptor occupancy theory?
The more receptors occupied by the drug, the greater the effect
93
Ex. of a nonreceptor drug action:
Antacids neutralize gastric acid by direct action Chelating drugs form bonds with metallic cations
94
Agonist drugs work by:
Mimicking cell signalling molecules and activating the same receptors
95
Antagonist drugs work by:
Binding to same receptors as cell signals WITHOUT activating the receptor, therefore blocking the signaling molecules
96
How much does the chemical structure of a drug affect its affinity for a receptor?
Small changes in structure can dramatically change effect
97
Define racemic:
1/2 R isomer, 1/2 L isomer
98
Enantomerism can be produced by:
sp3 hybridized carbon atoms
99
Define efficacy:
The ability of a drug to produce the desired therapeutic effect
100
Define potency:
The relationship between the effect of a drug and the dose necessary to achieve that effect
101
Quickness to effect and amount needed to effect: which is efficacy? Which is potency?
Efficacy: quickness Potency: amount
102
Define ED50 and LD50:
ED50 is the dose effective in 50% of people LD50 is the dose lethal in 50% of people
103
Define therapeutic index:
The ratio of LD50 to ED50
104
Define hyperreactivity:
An unusually low dose of drug produces the expected effect
105
Define hypersensitivity:
Allergy
106
Define additive effect:
A second drug acting with the first will produce effect equal to the sum of both 1+1=2
107
Define synergistic effect:
Two drugs interact to produce an effect greater than their sum 1+1=3
108
What type of combined effect do Fentanyl and Versed have?
Synergistic, esp. on respiratory rate

ARCHIVED: Pharmacology for Nurse Anesthesia (20 decks)

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