Principles of Pharmacology Flashcards
(112 cards)
1
Q
Pharmacodynamics
A
What the drug does to the body
-the connection between drug concentration and effect
2
Q
Pharmakinetics
A
What the drug does to the body
-How the drug concentration in plasma changes over time
3
Q
What does pharmakinetics provide information to
A
- extent and duration
- preferred dose and dosing interval
- Preferred route of administration
- how to optimize therapies
- how to avoid toxicities
- how to avoid drug interactions
4
Q
4 Stages of pharmakinetics
A
Administration
Distribution
Metabolism
Excretion
(ADME)
5
Q
Administration
(3)
A
- can affect how quick + how much drug enters systemic circulation
- Not all routes of administration are suitable for all drugs
- drug must be administered to reach site of administration
6
Q
Formulations for administration depend on:
A
- Route of admission
- Time course of action
- Active drug concentration
7
Q
How quick and how much drug enter systemic circulation are important factors for
A
- Determining peak plasma concentrations + duration of drug
8
Q
Chosen route of drug depends on
A
desired outcome
9
Q
Enteral administration
A
Entry through the GI tract
10
Q
Where is enteral administration absorbed
A
- between the mouth and anus
- Usually stomach or small intestine
11
Q
How much drug is absorbed through enteral absorption
A
Less then 100% due to first pass metabolism
12
Q
Enteral absorption depends on
A
- disintegration/solubility
- acidity of GI tract
- GI blood flow
- drug stability
- gastric emptying and motility
13
Q
Enteral administration benefits
A
- Easy, safe, cheap
- No need for sterility/purity
14
Q
Enteral administration Drawbacks
A
- Acid sensitive + protein drugs are unstable
- Ph must be conscious and cooperative
- variable absorption + bioavailability
- possible upper GI irritation
15
Q
First pass metabolism is also called
A
pre-systemic elimination
16
Q
First pass metabolism
A
drugs passing through liver before entering systemic circulation
17
Q
what does the liver do during first pass metabolism
A
- Site of drug metabolism
- drug concentration can dramatically decrease
- extent of drug metabolism varies for different drugs
18
Q
What does liver damage do to first pass metabolism
A
- decreased liver metabolism
- creates unpredictable drug metabolism and concentrations
19
Q
What does metabolism do to drugs
A
changes molecules
eg. Codeine becomes morphine
20
Q
When does first pass metabolism occur
A
with enteral administration
-especially PO
21
Q
Rectal (PR) Administration
A
Absorption through rectal mucosa
22
Q
Rectal (PR) Benefits
A
- Rapid absorption
- cheap, easy
- Useful if pt. can’t or won’t swallow
- Less first pass effect
23
Q
Rectal (PR) drawbacks
A
- often incomplete absorption
- irritation on mucosal lining
24
Q
Sublingual (SL) Administration
A
Drug is placed under tongue to dissolve and absorbe
25
Sublingual (SL) Benefits
1. Rapid
2. no first pass effect
26
What does no first pass effect mean
drug enters systemic blood immediately
27
Sublingual (SL) drawbacks
1. many drugs taste bad
28
Buccal Administration
drug placed between gums and lip to be absorbed
29
Types of enteral Administration
1. PO
2. PR
3. SL
4. Buccal
30
Enteral administration formulations
1. Tablets
2. Capsules
3. Liquids
4. Buccal film
31
Parenteral Administration
Not absorbed through GI tract
32
Subcutaneous Injection (SC)
Drug is injected under skin
33
Subcutaneous injection benefits
1. Rapid effect due to general circulation
2. useful for local injection/delivery
3. easy self administration
4. easy to control
34
Subcutaneous injection drawbacks
1. requires sterile drug
2. some pts don't like injections
3. absorption affected by blood flow and injection volume
35
Intramuscular Injection (IM)
Drugs injected into skeletal muscle
36
Intramuscular injection benefits
1. cane be into a large muscle mass
2. self administered
3. absorption into systemic circulation can be controlled
4. oil based formulation allow for slower absorption (depot bolus)
37
Intramuscular injection drawbacks
1. can be painful
2. must be sterile
38
Intravenous (IV)
Drugs injected directly into vein as a rapid bolus (Push) or continuous infusion (Drip)
39
Intravenous benefits
1. all drug enters the bloodstream
2. rapid distribution + onset of drug
3. large drug volumes
4. very predictable
40
Intravenous drawbacks
1. requires skilled administration + close monitoring
2. Drug must be sterile
3. greater cost
41
Inhalation
drug inhaled into airways
42
Inhalation benefits
1. useful for local action (bronchodilators) but also into pulmonary circulation
2. no first pass effect
3.useful for gasses
43
Inhalation drawbacks
1. limited absorption of large proteins
2. possible irritation of lung lining
44
Inhalation formulations
1. gasses or gas mixtures
2. inhalers for pulmonary use
3. pressurized aerosol and other containers allow unused product to remain uncontaminated for later use
45
Types on inhalers
1. particulate powders
2. nebulized (mists)
46
Other parenteral routes
1. intraarticular injection (joints)
2. intracardiac injection (cardiac)
3.epidural injection
4. spinal injection (spinal fluid)
47
Topical Administration
applied on surfaces
48
Topical administration locations
1. skin
2. eyes
3. ears
4. nose
5. vagina
49
Transdermal Administration
1. Absorbed through the skin
2. Local and systemic effects
50
Transdermal benefits
1. cheap and easy
2. simple local administration
3. no first pass effect
51
Transdermal drawbacks
1. not suitable for many drugs (fat insoluble)
2. absorption affected by skin hydration
52
Transdermal formulations
1. creams, gels, ointments
2. absorption can be enhanced by suspension in an oily vehicle
3. controlled by release patched (nicotine)
4. topical aerosol spray
53
Absorption
Entry of drug into circulating system
54
Example of absorption
1. Drug must pass through the epithelial cells of the GI tract
2. Then into blood flowing through the capillaries of the gut wall
55
Chemical factors affecting drug absorption
1. Drug size
2. Lipid solubility
3. Drug charge
4. Bioavailability
56
Bioavailability
The proportion of drug that passes into systemic circulation post administration, taking into account both absorption and metabolic degradation
57
Bioavailability for enteral routes
Less then 100%
58
Bioavailability for parenteral routes
High
59
What affects bioavailability
1. first pass effect
2. drug absorption
60
What factors of drug absorption affect bioavailability
1. Solubility of drug
2. Stability of drug
3. Formulation of drug
61
Distribution
1. follows absorption
2. mixed into blood quick
62
3 Determining factors of distribution
1. Blood flow to tissues
2. Exiting the vascular system
3. Entering cells
63
Initial distribution
rapid in the first few minutes, depends entirely of rate of blood flow to given tissues
64
Tissues with high bloodflow
exposed to drug more quickly then those with less
65
Rapid distribution goes to
heart, liver, kidneys
66
slow distribution goes to
muscles, skin, fat
67
Second distribution
1. slower
2. depends on where drugs like to be
68
What affects distribution
1. lean mass (watery environment)
2. fat solubility of drug accumulation
3. Plasma protein binding
69
Plasma protein binding
1. most drug molecules don't float freely in blood
2. often bound to plasma proteins (up to 90%)
3. Albumin
4. only free drugs create effects
70
Albumin
- most common plasma protein
- major carrier drug
71
liver disease affect on distribution
decreases blood albumin- more free drug molecules to create effects
72
Metabolism
1. modification/change of drug molecule by enzymes
2. mostly occur in liver, gut, kidney, lungs, plasma, placenta
3. metabolized by cytochrome enzymes
4.varies between people
5. inhibiting cyps can be dangerous
6. cyp enzyme induction
73
What inhibits CYPs
-grape fruit juice
-other drugs
74
CYP enzyme induction
cells stimulated to make more enzymes
75
Therapeutic consequences of drug metabolism
1. accelerated renal drug excretion
2. drug inactivation
3. increased therapeutic action
4. activation of prodrugs
5. increased or decreased drug toxicity
76
Accelerated renal drug excretion
1. most common effect
2. acids water solubility
77
Drug excretion
1. removal from body
2. mostly through kidney
3. some may be excreted in an altered form
4. most drugs must be metabolized before they work
5. Drug enters tubular fluid
78
Excretion depends on
1. Plasma protein binding
2. Drug fat solubility
79
Excretion is through
1. Kidney
2. GI tract
3. Sweat
4. Breast milk
80
Drug enters tubular fluid
1. filtration through glomular capillaries
2. active transport through specialized carriers
81
What can be excreted in unaltered formes
some antibiotics
82
Why do most drugs need to be metabolized first
1. renders the drug active
2. makes the drug more water soluble/less fat soluble
83
Dosage Regimes
Effective treatment requires effective dosage regimes
-dose size
-dose frequency
84
Time course of drugs
duration of effects is determined by the combination of metabolism + excretion
85
Drug steady state
When there is a consistent level of drug in the body
86
What does drug steady state depend on
Half life of the drug
87
Half life
1. time required for the amount of drug in the body to decrease 50%
88
What does half life measure
the rate drugs are removed from the body
89
A long half life takes
a long time to reach steady state with multiple doses
90
A short half life takes
a short amount of time to reach steady state with multiple doses
91
How many half lives does it take to reach steady state
4-5
92
Most drugs get metabolized/excreted according to
principles of percentage loss of drug over time
93
Very few drugs leave the body at a consistent rate: what are 2 examples
1. Ethanol (alcohol)
2. Phenytoin
94
Pharmacodynamics is the
relationship between drug concentration at the site of action and its biological effect
95
Drug receptors
1. to elicit an effect on the body drugs must interact directly with cells
2. usually binding to specific targets
96
drug receptors are
protein targets
97
drugs exhibit selectively for their receptors: meaning
1. they interact with their target molecules, cell, or tissues
2. high concentrations they lose this selectively
98
2 common possibilities of drug action
1. response
2. no response
99
What does drug binding depend on
the affinity or stickiness of the drug for its target
100
Agonist
elicits a response
101
Antagonist
Prevents a response to an endogenous or neurotransmitter agent
102
Dose response relationship
1. relationship between size of administered dose and intensity of response produced
103
Dose response relationship is determined by
1. minimum amount of drug to be used
2. maximum response a drug can elicit
3. how much to increase the dose to increase the desired effect
104
Onset
Time it takes for the drug to elicit a therapeutic response
105
Peak
Time it takes for a drug to reach max therapeutic response
-Troughs and MEC
106
Trough
lowest blood level of the drug
- too low drug becomes ineffective
107
MEC
Minimum effective communication
108
Minimum effective communication (MEC)
plasma drug level that must be reached for therapeutic effect
109
Duration
time for which a drug concentration is sufficient to elicit a therapeutic response
110
Therapeutic Index
1. Measures drug safety
2. Ratio of the drug toxic: effective drug concentration
3. Smaller the therapeutic index the less safe the drug
111
Be extra careful with drugs with a _____ Therapeutic index, ____ dangerous
Narrow, more dangerous
112
Non-receptor Drugs
simple physical or chemical interactions with other molecules
-Antacid, saline laxatives, chelating agents
