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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
Drawbacks of rectal administration
-absorption can be incomplete -many drugs cause irritation of mucosal lining
26
Sublingual (SL) administration
Drug placed under the tongue, where it dissolves into mucosa under tongue
27
Advantages of sublingual administration (SL)
-rapid absorption -no fast pass effect (usually why it is SL) -suitable for acid sensitive drugs -fast, easy, cheap
28
Disadvantages for sublingual administration
Many drugs taste bad
29
Pharmacokinetic profile is more in common with
SC, IM, IV administration
30
Capsules
Powder in a gelatin coating -allows for faster absorption
31
Buccal film
Tablet that just sits in the gum area
32
Subcutaneous injection (SC)
Drug is injected under the skin into subcutaneous tissue
33
Advantages of Subcutaneous injection (SC)
-rapid as it enters general circulation -local drug delivery -easy self administration
34
Disadvantages Subcutaneous injection (SC)
-requires sterile drug -personal preference -absorption relies on blood flow and injection volume
35
Intramuscular injection (IM)
Drug injected into skeletal muscle
36
Advantages for Intramuscular injection (IM)
-can be in large muscle mass -self administration -systemic circulation absorption can be controlled (oil based formulation)
37
Disadvantages for Intramuscular injection (IM)
Can be painful
38
Intravenous (IV)
Drug injected directly into vein
39
Two types of Intravenous (IV)
-rapid bolus (IV push) -continuous infusion (IV drip)
40
Advantages of Intravenous (IV)
-all drug enters bloodstream (100% bioavilibity) -rapid distribution and onset of action -can have large drug volumes
41
Disadvantages for Intravenous (IV)
-requires skilled administration and close monitoring -drug must be sterile -greater cost
42
Inhalation
Drug inhaled into airways
43
Advantages of inhalation
-Useful for local action but can be absorbed into pulmonary circulation -no first pass effect -useful for gasses
44
Disadvantages of inhalation
-limited absorption of large proteins -possible irritation of lung lining
45
Formulations for inhalations
Can be gasses or gas mixtures
46
Inhalers for pulmonary use are made up of
-particulate powders -nebulized (mist)
47
Pressurized aerosol and other containers allow for
Unused product to remain uncontaminted for later use
48
Topical routes
-skin -eyes -nose -vagina
49
Transdermal
Aborsption thorugh skin -for local and systemic effects
50
Benefits of transdermal
Cheap and easy -simple local administration -no first pass effect
51
Drawbacks of transdermal
Not suitable for many drugs (fat insoluable) -absorption affected by skin hydration
52
Transdermal formulations
Creams, gels, ointments (help to enhance absorption via oily vehicle), controlled release patches, topical aerosol spray
53
Intra articular injection
Joints -parenteral
54
Intra cardiac injection
Heart -parenteral
55
Spinal injection
Into spinal fluid -parenteral
56
Buccal
Absorption between gum and cheek -enteral
57
What does it mean by absorption
Entry of drug into circulatory system
58
Orally administered drugs example
-must pass through the epithelial cells of GI tract -then into blood flowing through capillaries of gut wall
59
What are some chemical factors affecting drug absorption?
Drug size, lipid solubility, drug charge
60
Bioavailability
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
Bioavailability and po
Often much less than 100%
62
Bioavalibity is high with
SC, IM, IV
63
Bioavailability is affected by
-first pass effect -drug absorption (solubility, stability, formulation)
64
What takes place after absorption
Drug is distributed throughout the body -mixes throughout the blood very quickly (~1min)
65
Initial rapid distribution of a drug depends on
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
Areas in the body with rapid drug distribution
Heart, liver, kidneys, brain
67
Areas of slow drug distribution
Muscle, skin and fat
68
Second slower phase of distribution depends on
Where a drug ‘likes’ to be -can take minutes to hours
69
The second phase of distribution is affected by several factors
-lean mass (watery environment eg muscle) -fat solubility of the drug (drug accumulation) -plasma protein binding
70
Plasma protein binding
Majority of drug molecules do not float around, entirely free within blood
71
Drugs are often bound to
Plasma protein -% of drug bound to protein can be quite high 90% or more
72
What is the most common plasma protein
Albumin -major carrier of drugs
73
Only what type of drugs can have effects
Only free drugs can have effects
74
Metabolism
Modification of a drug molecule by cell enzymes
75
Drug metabolism most occurs in the
Liver -but can also be in the gut, kidney, lungs, plasma, placenta
76
Drugs are largely metabolized by
Cytochrome P450 family of enzymes
77
Therapeutic consequences of drug metabolism
-accelerated renal drug excretion -drug inactivation -increased therapeutic action -activation of prodrugs -inc/Dec toxins
78
Inhibition of CYP
Can be very dangerous -grapefruit juice -other drugs that compete
79
CYP enzyme induction
Cells stimulated to make more enzymes
80
CYP
Cytochrome P450 superfamily
81
What are the kidneys unable to excrete
Drugs that are highly lipid soluble
82
Three of the cytochrome p450 do what? What are these?
Metabolize drugs -CYP1 CYP2 CYP3
83
The other nine cytochrome p450 metabolize what?
Endogenous compounds -steroids, fatty acids
84
Drug excretion occurs mostly through the
Kidneys -but also includes GI tract, sweat, breast milk
85
Drug excretion depends on
-plasma protein binding -drug fat solubility/charge
86
How many nephrons in a kidney
About 1 million
87
GI tract drug excretion
Via bile into small intestine then colon -mainly fatty type drugs
88
Drug excretion enters the tubular fluid by
-filtration through gomerular capillaries -active transport through specialize carreirs
89
How does albumin binding affect excretion in the kidneys
High degree of binding causes difficulty in glomerular filtration
90
What type of drugs generally are excreted out by the kidney
Nonlipid solvable drugs
91
How are drugs binded to albumin excreted
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
How are drugs binded to albumin excreted
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
Before drugs are excreted they generally need to be
Metabolized first as it renders drug inactive and more water soluble/less fat soluble -some antibiotics can be excreted in an unaltered form
94
Dosage regime (2) is the
Dose size and frequency
95
Duration of effects of a drug is determined by
A combination of metabolism and excretion -m/e cause the drug levels to fall!!!
96
Drug steady state
When there is a consistent level of drug in the body
97
Half life (T1/2)
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
The time to reach a steady state is dependant on a drugs..
Half life (T1/2) -rate at which drugs removed from the body
99
The time to reach a steady state will take
4 to 5 half life’s (T1/2)
100
If a drug has a long T1/2
It takes a long time to reach a steady state -repeated dosing larger gaps between
101
If a drug has a short T1/2
It takes a short time to reach a steady state -with repeated dosing shorter gaps
102
Morphine T1/2
Takes around 18 hours needed to reach steady state -4,8,12,16*,20* hours
103
Digoxin T1/2
Roughly 7 days to steady state -36hour daily take
104
How can you shorten the steady state
-Increase first dose, then regular remaining doses -bi daily You would need to give it closer together
105
Most drugs are metabolized/excreted according to principles of
Percentage loss of drug over time -not fixed
106
A few drugs leave the body at a constant rate, they are…
-ethanol (alcohol) -phenytoin (drug for epilepsy)
107
To elicit an effect on the body drugs must
Interact directly with cells -usually
108
Drugs usually bind to specific…. Which are:
Targets -mostly proteins, some drugs act on DNA or cell membranes
109
Examples of drugs that act on DNA and cell membranes
DNA: anti tumour drugs CM: antimicrobial agents
110
Protein targets are referred to as
Receptors
111
Drugs should exhibit selectively for their receptor, this means that
-interact only with their target molecule, cell or tissue
112
At high concentrations, drugs may
Lose selectivity -could travel somewhere else (asthma example beta2/beta1)
113
Common consequence of metabolism
Changing the drugs shape, and making it so the drug cannot bind to the target
114
Two common possibilities of drug action
AGONIST = drug a + receptor —> drug A-receptor —> response ANTAGONIST = drug b + receptor —> drug b-receptor —> no response
115
Binding of drug depends on ___ of drug for it’s target
Affinity (stickiness)
116
Agonist
Elicits a response
117
Antagonist
Prevents a response to endogenous agonist
118
The more drug molecules the more
Effect
119
The relationship between the size of an administered dose and the intensity of the response produced determines the following
-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
Onset
Time it takes for the drug to elicit a therapeutic response
121
Peak
Time it takes for a drug to reach its maximum therapeutic response
122
Trough
Lowest blood level, if it is too low drug will be ineffective
123
MEC
Minimum effective concentration -the plasma drug level that must be reached for a therapeutic effect
124
Duration
Time for which a drug concentration is sufficient to elicit a therapeutic response
125
Therapeutic index
Measure of a drugs safety
126
Larger the therapeutic index
The safer the drug
127
The smaller the therapeutic index
The less safe the drug
128
Examples of receptorless drugs
Antacids, saline laxatives, chelating agents

Pharmacology (37 decks)

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