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Pharmacology > IV Agent Uptake And Distribution > Flashcards

IV Agent Uptake And Distribution Flashcards

1
Q

Pharmacokinetics constitutes of: 4

A

Absorption, distribution, metabolism, excretion

What body does to a drug

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2
Q

Pharmacodynamics: 3

A

Mechanism of effect, sensitivity, responsiveness

What a drug does to the body

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3
Q

Pharmacokinetics measured in: 4

A

Elimination half time, bioavailability, clearance, volume of distribution (vd)

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4
Q

Compartmental models do what

A

Divides body into compartments that represent theoretical spaces with calculated volumes

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5
Q

Central compartment traits and components

A

Best perfused, 75% CO, 10% of body, rapid uptake, drug introduced here, then 2nd compartment, then back to central for clearance. Kidney, liver, lungs, heart, brain.

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6
Q

Peripheral compartment

A

Large calculated volume (90%), 25% of cardiac output, extensive uptake of drug

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7
Q

Rate of transfer between compartments changes with what

A

Decreases with aging which leads to greater plasma conc in certain drugs (thiopental)

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8
Q

Distribution: what happens

A

Following systemic absorption of a drug the highly perfused tissues (heart, brain, kidneys, liver) receive a large amt of the drug

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9
Q

Distribution: what happens after central compartment

A

As plasma conc decreases, drug to less perfused sites (muscle and fat). W continued elim of drug the plasma level goes below that in tissues, drug leaves tissues to re-enter circulation

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10
Q

Tissues that accumulate drugs do what

A

Preferentially act as reservoir to maintain plasma concentration and prolong effect

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11
Q

What large or repeated doses do to distribution

A

They saturate inactive tissue negating distribution, prolong duration of action, reduction of effect depends on metabolism rather than redistribution

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12
Q

% of blood flow and % cardiac output in:
Vessel rich
Vessel poor

A

10%, 75%

20%, <1%

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13
Q

% blood flow and % cardiac output in muscle group and fat group

A

50%, 19%

20%, 6%

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14
Q

Lung uptake does what

A

Uptakes basic lipophilic drugs (lidocaine, fentanyl, demerol) and acts as reservoir for release of drug back into systemic circulation

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15
Q

Blood brain barrier prevents what

A

Ionized, water soluble drugs from crossing barrier into brain circulation

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16
Q

Blood brain barriers can be overcome w what

A

Large doses of drug or in head injury and hypoxemia

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17
Q

Effect site

A

Where drugs exert their biological effect, at its “biophase” (otherwise known as effect site)

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18
Q

Effect site includes what

What is ke0

A

Membranes, receptors, and enzymes where drug acts on body

Rate constant of drug elim from the effect site

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19
Q

What is vd

A

Volume of distribution, sum of all the volumes of compartments

Dose of IV drug/ plasma conc before elim

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20
Q

Vd is effected by what

A

Physiochemical characteristics of drug: lipid solubility (directly correlated), binding to plasma protein (inversely), molecular size (inversely)

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21
Q

Elimination half time

A

Time for plasma conc of drug to decline 50% during elim phase

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22
Q

E 1/2 t of a drug is related to what two things

It is independent of what

A

Directly to Vd, inversely to clearance

Dose of drug administered

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23
Q

Half life refers to 3, half time refers to 1

A

Plasma, fat, and muscle

Plasma

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24
Q

Elimination half life

A

Time necessary to elim 50% of drug from the body. Drug accum occurs if dosing intervals are less than this

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25
Q

Elim half time and half life aren’t equal when what

A

When the decrease in plasma concentration doesnt parallel its elimination from the body

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26
Q

Half time: 0
Fraction of initial amt left
% amt eliminated

A

1

0

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27
Q

Half time: 1
Fraction of initial amt left
% amt eliminated

A

1/2

50%

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28
Q

Half time: 2
Fraction of initial amt left
% amt eliminated

A

1/4

75%

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29
Q

Half time: 3
Fraction of initial amt left
% amt eliminated

A

1/8

87.5%

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30
Q

Half time: 4
Fraction of initial amt left
% amt eliminated

A

1/16

93.8%

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31
Q

Half time: 5
Fraction of initial amt left
% amt eliminated

A

1/32

96.9%

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32
Q

Half time: 6
Fraction of initial amt left
% amt eliminated

A

1/64

98.4%

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33
Q

Distribution phase

A

First half of curve, from central compartment to peripheral

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34
Q

Elimination phase

A

Second half of curve, from central compartment to liver and kidneys for elimination

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35
Q

Context sensitive half time

A

Time req for blood or plasma concentrations of a drug to decrease by 50% after discontinuation of drug admin. Usually refers to d/c an infusion

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36
Q

Absorption

Depends on what

A

Drugs solubility, regardless of route of administration

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37
Q

Oral admin

Pros and cons

A

Pro: Convenient and economic
Con: Emesis, destruction by enzymes or acidic gastric fluid, irregular absorption w food or other drugs

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38
Q

First pass effect

A

Drugs absorbed from GI sys enter portal venous blood and pass thru liver before entering the systemic circ for delivery to tissue receptors. Here they are extensively extracted and metabolized

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39
Q

Sublingual and transmucosal routes

A

Rapid onset, bypasses liver and prevents first pass effect

40
Q

Transdermal route

What it provides, where absorbed

A

Sustained plasma conc of drug. Absorp in sweat ducts and hair follicles that serve as diffusion shunts

41
Q

Transdermal route
Rate limiting step
Factors for permeability of drug
What can occur

A
  • diffusion across stratum corners of epidermis
  • thickness and blood flow of skin
  • contact dermatitis
42
Q

Rectal mode.
Proximal
Distal
Overall

A

P- trans to portal sys via superior hemorrhoidal veins, 1st pass effect
D- bypasses portal sys
Unpredictable responses that follow rectal admin of meds

43
Q

IV route

A

Achieves therapeutic plasma levels precisely and rapidly

44
Q

Ionization
Most drugs are what
Non ionized drugs are what

A
  • Weak acids or bases in ionized and non-ionized forms

- usually lipid soluble and can diffuse across lipid cell membranes ex BBB, renal, tubules, GI epithelium, hepatocytes

45
Q

Ionization

-the fraction of drug is pharmacologically ___ and undergoes what

A

Active- undergoes reabsorption across renal tubules, is abs from gi tract, and is metabolized by liver

46
Q

Ionized fraction of drug is what

A

Poorly lipid soluble, cant penetrate lipid cell membranes, and is repelled from portions of the cell w similar changes. They are excreted by kidneys unchanged

47
Q

Degree of ionization depends on what

A

Dissociation constant (pk) and ph of the surrounding fluid

48
Q

Changes in ph can result in what

A

Large degree of ionization. Acidic drugs are highly ionized at alkaline ph and vice a versa

49
Q

Alkalotic pt giving a weak acid=

A

Will have less drug effect because more ionization

50
Q

Acidotic pt giving weak acid drug

A

More nonionized drug, more effect

51
Q

Ion trapping

Ex

A

Concentration difference of total drug can develop on 2 sides of a membrane that separates fluids w diff pHs. Ex placenta

52
Q

Protein binding: ex., effect

A

Albumin acids, a1 acid glycoprotein bases, lipoproteins

Only free or unbound fraction of drug is readily able to cross cell membranes

53
Q

Vd inversely proportional to

Unbound drug in plasma is metabolized and excreted ___ ___

A

Protein binding

More readily

54
Q

Drugs that are highly protein bound (4 ex) are effected by what

A

Warfarin, propranolol, phenytoin, diazepam

Alterations in protein binding

55
Q

Clearance

A

Volume of plasma cleared of drug by metabolism and excretion

56
Q

First order kinetics

A

Almost all drugs administered in therapeutic dose range are cleared at a rate proportional to the amount of drug present in plasma

57
Q

Zero order kinetics, ex 3

A

Drugs that exceed metabolic or excretory capacity of the body to clear drugs by first order kinetics even at therapeutic doses
Constant amt of drug metabolized per unit of time
Ex) asa, dilantin, etoh

58
Q

Hepatic clearance, other term for it

A

Hepatic blood flow and hepatic extraction ratio. If extraction high (>0.7) the clearance of the drug depends on hepatic blood flow
Perfusion dependent elimination

59
Q

Extraction ratio dep on blood flow

Total range

A

0.7-1

0-1

60
Q

What = low extraction ratio

If extraction ratio low what will increase clearance

A

0.3 or less

A decrease in protein binding or increase in enzyme activity

61
Q

What will have minimal change in clearance if extraction ratio is low

A

Changes in hepatic blood flow

62
Q

What is capacity dependent elim

A

If extraction ratio low: protein binding or inc enzyme activity increases clearance. Changes in hepatic blood flow has min effect

63
Q

Renal clearance

  • most imp organ for what
  • what is excreted better
  • what isn’t excreted
A
  • elim of unchanged drugs or their metabolites
  • water soluble compounds > lipid soluble drugs
  • highly lipid soluble drugs, little or no unchanged drug excreted in urine
64
Q

Metabolism

A

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

65
Q

Increased water solubility reduces what and enhances what

A

Reduces Vd

Enhances renal excretion

66
Q

Metabolism not always synonymous with what

A

Inactivation or detoxification. Some metabolites of certain drugs are active

67
Q

Which order kinetics most common

What it is basically

A

First order

Constant fraction of available drug is metabolized in a given time period

68
Q

Zero order kinetics basically and ex

A

Plasma conc of drug exceeds capacity of metabolizing enzymes. Metab of a constant amt of drug per unit time

Etoh, dilantin, asa

69
Q

4 pathways of metabolism

A

Oxidation
Reduction
Hydrolysis
Conjugation

70
Q

Phase I

A

Oxidation, reduction, hydrolysis

71
Q

Phase II

A

Parent or metabolite drug reacts w an endogenous substrate to form water soluble conjugates

72
Q

Sites of uptake

A

Plasma, kidneys, lungs, gi tract, liver (hepatic microsomes enzymes are responsible for metabolism of most drugs)

73
Q

Hepatic microsomes enzymes:

  • located where
  • cytochrome p450
A
  • hepatic smooth ER

- large number of diff protein enzymes involved in oxidation and reduction and conjugation of large # of drugs

74
Q

Enzyme induction

A

Drugs and chemicals stimulate activity of these enzymes

75
Q

Nonmicrosomal enzymes

  • metabolize by what
  • present where
A

Mainly by conjugation and hydrolysis. Some by oxidation-reduction

Liver mostly, plasma, gi tract

76
Q

Nonmicrosomal enzymes

  • responsible for hydrolysis of what
  • dont undergo what
  • determined by
A
  • drugs that contain ester bonds (succhs, esmolol)
  • enzyme induction
  • genetically
77
Q

Pharmacodynamics

A

How drugs exert fx. Most common mechanism= interaction w specific macromolecules in lipid bi-layer of cell membranes called receptors

78
Q

State of receptor activation theory

A

Non activated receptors are converted to active by the drug

79
Q

Receptor occupancy theory

A

The more receptors occupied by drug the more effect

80
Q

Nonreceptor drug action

Def and Ex

A

Mechanisms other than receptor drug interactions. Chelating drugs form bonds w metallic ions that are found in body. Ex antacids

81
Q

Agonist drugs

A

Mimic cell signaling molecules by activating the same receptor sites and causing similar effects

82
Q

Antagonist drugs

A

Bind to receptors and change configuration of agonist site or bind to it, preventing effect from cell signaling molecules

83
Q

Structure activity

A

Affinity of a drug for a specific macro molecular component of the cell and its intrinsic activity are r/t chemical structure

84
Q

Enantomerism produced by

A

Sp3 hybridized carbon atoms. Free rotation about chiral carbon not possible, 2 stable forms of molecule exist

85
Q

Isomer differences w drugs

A

Interaction w biological receptors can differ, even to pt of no binding. Some may cause entirely diff side effects. Some may have little to no effect

86
Q

Ephedrine isomers

A

2 chiral centers and 4 isomers

87
Q

Potencies of ephedrine

A

D ephedrine 36
L epedrine 11
D pseudophedrine 1
L pseudophedrine 7

88
Q

Efficacy

A

The ability of a drug to produce desired therapeutic effect

89
Q

Potency

A

The relationship b/w therapeutic effect of a drug and dose necessary to achieve that effect

90
Q

ED 50

A

Median effective dose. The wider the range, the more effective the drug

91
Q

LD 50

A

Median lethal dose. Halfway pt where rats stop breathing

92
Q

Ratio of LD50 to ED50

A

Indicates therapeutic index of a drug for that effect. Suggests how selective drug is in producing its desired effects. Estimates clinical therapeutic index

93
Q

Hyperreactive

A

Ppl in whom lose dose of drug produces expected pharmacological effect

94
Q

Hypersensitivity

A

Refers to allergies

95
Q

Additive effect

A

Second drug acting w first produces sum of both

96
Q

Synergistic effect

A

2 drugs interact to form greater effect than sum. Like fentanyl and versed

Pharmacology (19 decks)

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