Principles Of Pharmacology (4,5) Flashcards

1
Q

Pharmacokinetics

A

What the body does to the drug

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2
Q

Pharmacodynamics

A

What the drug does to the body

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3
Q

Does the statement “how drug concentration in the plasma changes over time” refer to pharmacokinetics or pharmacodynamics?

A

Pharmacokinetics
-change in concentration = what the body is doing

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4
Q

Does the statement “relationship between drug concentration and effect” refer to pharmacokinetics or pharmacodynamics?

A

Pharmacodynamics
-what the drug is doing and how that is related to concentration

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5
Q

ADME stands for

A

Absorption, distribution, metabolism, elimination

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6
Q

Pharmacokinetics can be broken down into

A

ADME

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7
Q

Pharmacokinetics (how drug concentration i the plasma changes over time) provides information relevant to

A

-how long it takes to work
-route administered
-dose and dosing interval

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8
Q

Absorption

A

Movement of administration site into the molecules/bloodstream

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9
Q

What is the importance of drug administration

A

-affects how quickly and how much of drug is entering circulation
-not all routes are suitable for all drugs

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10
Q

Drugs are administered as a formulation depending on

A
  1. Route
  2. Time for course of action
  3. Active drug concentration
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11
Q

Enteral administration

A

Entry of drug through the GI tract
-absorption takes place somewhere between mouth and anus

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12
Q

Parenteral administration

A

Done not by the GI tract
-any other administration
-usually injection

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13
Q

PO stands for

A

Swallowing

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14
Q

Oral administration (PO)

A

Usually drug absorbed via stomach/small intestine
-absorption is <100%

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15
Q

Oral absorption depends on

A

-solubility/disintegration
-acidity of GI tract
-stability of drug
-gastric emptying and motility
-GI blood flow

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16
Q

Benefits of oral administration

A

Easiest, safest and cheapest
-drug doesn’t need to be sterile or pure (acid/protective measures)

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17
Q

Drawbacks of oral administration

A

-acid sensitive, protein drugs are unstable
-pt needs to be conscious and cooperative
-variable absorption
-possible GI irritability

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18
Q

First pass metabolism effect

A

Most drugs given orally first pass through the liver before entering the systemic circulation

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19
Q

What is the problem with first pass metabolism effect?

A

There is a chance that the drug molecules in the blood enters the hepatic portal vein and is absorbed into liver cells, being metabolized which creates a risk for a portion of the drug being changed

-drug concentration can drop dramatically

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20
Q

Extent of drug metabolism is

A

Drug to drug dependant
-depends on what drug is being used

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21
Q

If there is extensive first pass metabolism what will need to be prescribed?

A

There will need to be additional doses prescribed

-for example, if only 15% of the drug is not metabolized by the liver, then there will need to be additional doses as only 15% is surviving

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22
Q

Rectal administration (pr)

A

Absorption through rectal mucosa

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23
Q

Benefits of rectal administration

A

-rapid
-cheap and easy
-good if you can’t swallow
-less first pass effect

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24
Q

(pr) stands for

A

Per rectum

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25
Q

Drawbacks of rectal administration

A

-absorption can be incomplete
-many drugs cause irritation of mucosal lining

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26
Q

Sublingual (SL) administration

A

Drug placed under the tongue, where it dissolves into mucosa under tongue

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27
Q

Advantages of sublingual administration (SL)

A

-rapid absorption
-no fast pass effect (usually why it is SL)
-suitable for acid sensitive drugs
-fast, easy, cheap

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28
Q

Disadvantages for sublingual administration

A

Many drugs taste bad

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29
Q

Pharmacokinetic profile is more in common with

A

SC, IM, IV administration

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30
Q

Capsules

A

Powder in a gelatin coating
-allows for faster absorption

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31
Q

Buccal film

A

Tablet that just sits in the gum area

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32
Q

Subcutaneous injection (SC)

A

Drug is injected under the skin into subcutaneous tissue

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33
Q

Advantages of Subcutaneous injection (SC)

A

-rapid as it enters general circulation
-local drug delivery
-easy self administration

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34
Q

Disadvantages Subcutaneous injection (SC)

A

-requires sterile drug
-personal preference
-absorption relies on blood flow and injection volume

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35
Q

Intramuscular injection (IM)

A

Drug injected into skeletal muscle

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36
Q

Advantages for Intramuscular injection (IM)

A

-can be in large muscle mass
-self administration
-systemic circulation absorption can be controlled (oil based formulation)

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37
Q

Disadvantages for Intramuscular injection (IM)

A

Can be painful

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38
Q

Intravenous (IV)

A

Drug injected directly into vein

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39
Q

Two types of Intravenous (IV)

A

-rapid bolus (IV push)
-continuous infusion (IV drip)

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40
Q

Advantages of Intravenous (IV)

A

-all drug enters bloodstream (100% bioavilibity)
-rapid distribution and onset of action
-can have large drug volumes

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41
Q

Disadvantages for Intravenous (IV)

A

-requires skilled administration and close monitoring
-drug must be sterile
-greater cost

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42
Q

Inhalation

A

Drug inhaled into airways

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43
Q

Advantages of inhalation

A

-Useful for local action but can be absorbed into pulmonary circulation
-no first pass effect
-useful for gasses

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44
Q

Disadvantages of inhalation

A

-limited absorption of large proteins
-possible irritation of lung lining

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45
Q

Formulations for inhalations

A

Can be gasses or gas mixtures

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46
Q

Inhalers for pulmonary use are made up of

A

-particulate powders
-nebulized (mist)

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47
Q

Pressurized aerosol and other containers allow for

A

Unused product to remain uncontaminted for later use

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48
Q

Topical routes

A

-skin
-eyes
-nose
-vagina

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49
Q

Transdermal

A

Aborsption thorugh skin
-for local and systemic effects

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50
Q

Benefits of transdermal

A

Cheap and easy
-simple local administration
-no first pass effect

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51
Q

Drawbacks of transdermal

A

Not suitable for many drugs (fat insoluable)
-absorption affected by skin hydration

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52
Q

Transdermal formulations

A

Creams, gels, ointments (help to enhance absorption via oily vehicle), controlled release patches, topical aerosol spray

53
Q

Intra articular injection

A

Joints
-parenteral

54
Q

Intra cardiac injection

A

Heart
-parenteral

55
Q

Spinal injection

A

Into spinal fluid
-parenteral

56
Q

Buccal

A

Absorption between gum and cheek
-enteral

57
Q

What does it mean by absorption

A

Entry of drug into circulatory system

58
Q

Orally administered drugs example

A

-must pass through the epithelial cells of GI tract
-then into blood flowing through capillaries of gut wall

59
Q

What are some chemical factors affecting drug absorption?

A

Drug size, lipid solubility, drug charge

60
Q

Bioavailability

A

The proportion of drug that passes into circulation after administration taking account both absorption and local metabolic degradation

-the extent and rate of drug entering systemic circulation and accessing site of action
-depends upon dosage form/administration

61
Q

Bioavailability and po

A

Often much less than 100%

62
Q

Bioavalibity is high with

A

SC, IM, IV

63
Q

Bioavailability is affected by

A

-first pass effect
-drug absorption (solubility, stability, formulation)

64
Q

What takes place after absorption

A

Drug is distributed throughout the body
-mixes throughout the blood very quickly (~1min)

65
Q

Initial rapid distribution of a drug depends on

A

The rate of blood flow to a given tissue
-tissues with a high blood flow will be exposed to more drug, more quickly, than those with low blood flow

66
Q

Areas in the body with rapid drug distribution

A

Heart, liver, kidneys, brain

67
Q

Areas of slow drug distribution

A

Muscle, skin and fat

68
Q

Second slower phase of distribution depends on

A

Where a drug ‘likes’ to be
-can take minutes to hours

69
Q

The second phase of distribution is affected by several factors

A

-lean mass (watery environment eg muscle)
-fat solubility of the drug (drug accumulation)
-plasma protein binding

70
Q

Plasma protein binding

A

Majority of drug molecules do not float around, entirely free within blood

71
Q

Drugs are often bound to

A

Plasma protein
-% of drug bound to protein can be quite high 90% or more

72
Q

What is the most common plasma protein

A

Albumin
-major carrier of drugs

73
Q

Only what type of drugs can have effects

A

Only free drugs can have effects

74
Q

Metabolism

A

Modification of a drug molecule by cell enzymes

75
Q

Drug metabolism most occurs in the

A

Liver
-but can also be in the gut, kidney, lungs, plasma, placenta

76
Q

Drugs are largely metabolized by

A

Cytochrome P450 family of enzymes

77
Q

Therapeutic consequences of drug metabolism

A

-accelerated renal drug excretion
-drug inactivation
-increased therapeutic action
-activation of prodrugs
-inc/Dec toxins

78
Q

Inhibition of CYP

A

Can be very dangerous
-grapefruit juice
-other drugs that compete

79
Q

CYP enzyme induction

A

Cells stimulated to make more enzymes

80
Q

CYP

A

Cytochrome P450 superfamily

81
Q

What are the kidneys unable to excrete

A

Drugs that are highly lipid soluble

82
Q

Three of the cytochrome p450 do what? What are these?

A

Metabolize drugs
-CYP1 CYP2 CYP3

83
Q

The other nine cytochrome p450 metabolize what?

A

Endogenous compounds
-steroids, fatty acids

84
Q

Drug excretion occurs mostly through the

A

Kidneys
-but also includes GI tract, sweat, breast milk

85
Q

Drug excretion depends on

A

-plasma protein binding
-drug fat solubility/charge

86
Q

How many nephrons in a kidney

A

About 1 million

87
Q

GI tract drug excretion

A

Via bile into small intestine then colon
-mainly fatty type drugs

88
Q

Drug excretion enters the tubular fluid by

A

-filtration through gomerular capillaries
-active transport through specialize carreirs

89
Q

How does albumin binding affect excretion in the kidneys

A

High degree of binding causes difficulty in glomerular filtration

90
Q

What type of drugs generally are excreted out by the kidney

A

Nonlipid solvable drugs

91
Q

How are drugs binded to albumin excreted

A

Through a much longer process, once the drugs not binded are excreted the equilibrium of drugs binded:not binded is off, and some are able to disconnect

92
Q

How are drugs binded to albumin excreted

A

Through a much longer process, once the drugs not binded are excreted the equilibrium of drugs binded:not binded is off, and some are able to disconnect

93
Q

Before drugs are excreted they generally need to be

A

Metabolized first as it renders drug inactive and more water soluble/less fat soluble
-some antibiotics can be excreted in an unaltered form

94
Q

Dosage regime (2) is the

A

Dose size and frequency

95
Q

Duration of effects of a drug is determined by

A

A combination of metabolism and excretion
-m/e cause the drug levels to fall!!!

96
Q

Drug steady state

A

When there is a consistent level of drug in the body

97
Q

Half life (T1/2)

A

The time required for the amount of drug in the body to decrease by 50%

-measure rate at which drugs are removed from body

98
Q

The time to reach a steady state is dependant on a drugs..

A

Half life (T1/2)
-rate at which drugs removed from the body

99
Q

The time to reach a steady state will take

A

4 to 5 half life’s (T1/2)

100
Q

If a drug has a long T1/2

A

It takes a long time to reach a steady state
-repeated dosing larger gaps between

101
Q

If a drug has a short T1/2

A

It takes a short time to reach a steady state
-with repeated dosing shorter gaps

102
Q

Morphine T1/2

A

Takes around 18 hours needed to reach steady state
-4,8,12,16,20 hours

103
Q

Digoxin T1/2

A

Roughly 7 days to steady state
-36hour daily take

104
Q

How can you shorten the steady state

A

-Increase first dose, then regular remaining doses
-bi daily

You would need to give it closer together

105
Q

Most drugs are metabolized/excreted according to principles of

A

Percentage loss of drug over time
-not fixed

106
Q

A few drugs leave the body at a constant rate, they are…

A

-ethanol (alcohol)
-phenytoin (drug for epilepsy)

107
Q

To elicit an effect on the body drugs must

A

Interact directly with cells
-usually

108
Q

Drugs usually bind to specific…. Which are:

A

Targets
-mostly proteins, some drugs act on DNA or cell membranes

109
Q

Examples of drugs that act on DNA and cell membranes

A

DNA: anti tumour drugs
CM: antimicrobial agents

110
Q

Protein targets are referred to as

A

Receptors

111
Q

Drugs should exhibit selectively for their receptor, this means that

A

-interact only with their target molecule, cell or tissue

112
Q

At high concentrations, drugs may

A

Lose selectivity
-could travel somewhere else (asthma example beta2/beta1)

113
Q

Common consequence of metabolism

A

Changing the drugs shape, and making it so the drug cannot bind to the target

114
Q

Two common possibilities of drug action

A

AGONIST = drug a + receptor —> drug A-receptor —> response

ANTAGONIST = drug b + receptor —> drug b-receptor —> no response

115
Q

Binding of drug depends on ___ of drug for it’s target

A

Affinity (stickiness)

116
Q

Agonist

A

Elicits a response

117
Q

Antagonist

A

Prevents a response to endogenous agonist

118
Q

The more drug molecules the more

A

Effect

119
Q

The relationship between the size of an administered dose and the intensity of the response produced determines the following

A

-minimum amount of drug to be used
-maximum response a drug can elicit
-how much to increase the dosage to produce the desired inc in response

120
Q

Onset

A

Time it takes for the drug to elicit a therapeutic response

121
Q

Peak

A

Time it takes for a drug to reach its maximum therapeutic response

122
Q

Trough

A

Lowest blood level, if it is too low drug will be ineffective

123
Q

MEC

A

Minimum effective concentration
-the plasma drug level that must be reached for a therapeutic effect

124
Q

Duration

A

Time for which a drug concentration is sufficient to elicit a therapeutic response

125
Q

Therapeutic index

A

Measure of a drugs safety

126
Q

Larger the therapeutic index

A

The safer the drug

127
Q

The smaller the therapeutic index

A

The less safe the drug

128
Q

Examples of receptorless drugs

A

Antacids, saline laxatives, chelating agents