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Pharmacology > Lecture 2 & 3 - Pharmacokinetics (PK) and Drug Disposition > Flashcards

Lecture 2 & 3 - Pharmacokinetics (PK) and Drug Disposition Flashcards

1
Q

Pharmacokinetics

A

what the body does to a drug

*study of how the body absorbs, distributes, metabolizes, and eliminates (ADME) a drug over time

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2
Q

ADME ?

A

Absorption
Distribution
Metabolism
Elimination/Excretion

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3
Q

Where does 1st pass effect occur?

A

stomach

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4
Q

Primary site for absorption?

A

small intestine

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5
Q

____ ______ is key for distribution

A

blood stream

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6
Q

Primary site for metabolism?

A

liver

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7
Q

Primary site of excretion

A

kidney

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8
Q

What is the clinical goal from using and understanding pharmacokinetics?

A
  • enhance efficacy

- decrease toxicity

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9
Q

Drug effect related to concentration at ??

A

site of action

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10
Q

For more drugs, the concentration at the site of the _____ determines the intensity of a drug’s effect

A

receptor

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11
Q

In order for drugs to move through the body they must cross cell membranes. What are the 3 ways they can do that?

A

1-pass through channels or pores

2-passing through the membrane with the aid of a transport system

3-penetrating directly

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12
Q

Where are transporters found?

A

liver
kidneys
intestines
brain capillaries

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13
Q

Out of the 3 types of drug movement, which is the most common?

A

direct penetration

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14
Q

Why does the movement through the body for most drugs depend on ability for direct penetration? (2 reasons)

A
  • most drugs are too large to pass through channels

- most drugs lack transport system to help them cross cell membranes

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15
Q

In order to penetrate cell membranes directly, a drug must be _____

A

lipophilic

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16
Q

Difference between one and two compartment model?

A

One-compartment model:
-drug is administered, immediately distributed, and then can be metabolized and excreted

Two-compartment model:

  • some drugs do not distribute instantaneously to all parts of the body
  • it goes to individual organs first, and then gets distributed to the peripheral part of the body afterwards
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17
Q

Drugs that don’t extensively distribute into extravascular tissues (drugs that aren’t stored) are well described as ?

A

one-compartment models

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18
Q

Drugs that do extensively distribute into tissue (drugs that are stored in tissues) are well described as ?

A

two-compartment models

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19
Q

bioavailability (absorption)

A

fraction of unchanged (unmetabolized) drug reaching the systemic circulation following administration by any route

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20
Q

drug accumulation

A

inversely proportional to dose lost

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21
Q

Vd (volume of distribution)

A

measure of apparent space in the body available to contain the drug - how the drug is distributed in the body relative to plasma

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22
Q

clearance refers to ???

A

metabolism and excretion

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23
Q

Clearance (metabolism and excretion)

A

measure of ability of the body to eliminate the drug

volume of drug per unit of time that gets excreted

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24
Q

drug half life (T1/2)

A

time required to change the concentration of the drug present in the body by one half during elimination

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25
Formula for: | bioavailability
AUC admin route / AUC(IV) x 100 OR AUC oral / AUC injected x 100
26
Formula for: | drug accumulation
accumulation factor = 1/dose lost
27
Formula for: | Vd
amount of drug in body (mg) / conc of drug in plasma (mg/L) answer expressed in L
28
Formula for: | clearance (Cl)
Cl = (0.693 / t1/2) x Vd
29
Formula for: | drug half life (T1/2)
t1/2 = (0.693 X Vd) / Cl
30
bioavailability (absorption) is the transfer of drug from ______ to ______
site of administration to bloodstream
31
When looking at a graph of time vs plasma concentration (Cp) - how do you determine bioavailability?
it is the area under the curve (extent)
32
When looking at a graph of time vs plasma concentration (Cp) - what does the time to reach peak concentration represent?
rate
33
When looking at a graph of time vs plasma concentration (Cp) - what does the peak concentration represent?
rate and extent
34
IV has what % Bioavailability
100%
35
IV has the ___ onset of any drug admin
fastest
36
What other route also has a very fast onset?
inhalation
37
List 3 limitations for drug absorption?
``` tissue perfusion (blood flow) diffusion-limited absorption first pass effect ```
38
What is first pass effect?
basically this is mainly a concern for drugs taken orally and what happens is the the liver metabolizes a portion of the drug before it can be effective
39
What is enterohepatic cycling?
It provides an opportunity for the body to recycle the drug that hasn't had a chance to be metabolized If it didn't get metabolized the 1st time it can get metabolized the 2nd or 3rd time around through enterohepatic cycling
40
Enterohepatic cycling reduces _____
elimination
41
Enterohepatic cycling prolongs
``` half life (drug stays in body longer) ```
42
List 8 factors influencing drug absorption
1) formulation 2) water solubility 3) lipid solubility 4) pKa 5) GI motility 6) posture (laying down or standing up) 7) other drugs/foods (possible interactions) 8) gastric pH
43
acidic drug is ____ in acid media
non-ionized
44
acidic drug is ____ in alkaline media
ionized
45
drug accumulates when ??
doses are repeated
46
How many half lives does it take to 100% accumulate?
at least 4
47
When is a steady state achieved? | give an example
When rate of drug elimination = rate of administration. | Example - IV
48
does frequent vs infrequent dosing affect steady state plasma concentration?
no - see diagram
49
_____ is protein most common for bound drug
albumin
50
only ____ drug can leave vessels
unbound (because bound drugs are too big)
51
high Vd = ?
drug is more distributed outside the plasma concentration
52
low Vd = ?
more blood in plasma concentration (less distributed)
53
What 2 things is Vd needed for determining?
clearance | loading dose
54
Formula for: | loading dose
loading dose = Vd x TC (target/desired concentration) / F | f = fraction absorbed bioavailability
55
What is a loading dose?
it immediately allows drug to get within the therapeutic range (whereas without a loading dose - it could take longer)
56
Formula for: | dosing rate
Cl x TC (target concentration) | vol/time) (amount/vol) = (amount/time
57
Formula for: | maintenance dose
(dosing rate / F) x dosing interval (amount/time) (time) = amount
58
First order rxns show a ____ graph
radical
59
Zero order rxns show a ____ graph
straight/constant
60
most drugs are ___ order rxn
first
61
When determining the order of a rxn, what are the x and y values on the graph?
``` x = conc of drug y = rate of drug metabolism ```
62
Give an example of a drug that under goes metabolism in a zero order rxn
phenytoin
63
acidic drugs are more likely to be concentrated in ____ compartment
blood
64
basic drugs are more likely to be concentrated in ____
tissue
65
describe phase 1 metabolism
drug is changed into modified drug by adding/exposing functional groups through: oxidation hydrolysis reduction
66
describe phase 2 metabolism
modified drug is changed into modified drug-conjugated through: glucuronidation sulfation (glutathione) acetylation
67
First order: rate of drug metabolism _____ to dose
proportional
68
Zero order: rate of drug metabolism remains ____ over time
constant
69
Clearance is needed for determining ?? (2)
dosing rate | maintenance rate
70
define clearance
the volume of plasma that would contain the amount of drug excreted per unit time (minutes)
71
for a drug to accumulate?
at least 4 half lives (90%)
72
for a drug to eliminate?
4-5 half lives (97%)
73
Low MW drugs enter kidney via renal artery and ____ soluble drugs move back into the blood
lipid
74
non-lipid soluble, polar, and ionized drugs remain in ____
urine
75
What are the 3 steps to renal elimination?
glomerular filtration tubular secretion tubular reabsorption
76
What is used to assess renal impairment?
creatinine clearance
77
____ CrCl = kidney not working properly
high
78
aging has a ____ effect on T1/2
decreasing
79
obeying has an ____ effect on T1/2
increasing
80
pathologic fluid has an ____ effect on T1/2
increasing
81
induction of CYP450 has a ____ effect on T1/2
decreasing
82
inhibition of CYP450 has an ____ effect on T1/2
increasing
83
organ failure has an ____ effect on T1/2
increasing
84
OAT = ?
organic anion transport (proteins)
85
OCT = ?
organic cation transport (proteins)
86
OATs and OCTs belong to?
SLC (super family) | -soluble carrier transporters
87
3 types of drug transporters?
-OATs -OCTs -P-glycoprotein (P-gp or MDRs) (multi-drug resistance-associated proteins)
88
___ is a vehicle for drugs being metabolized
bile
89
major route for drug elimination?
renal excretion
90
bile excretion favours compounds with a higher __
MW
91
hepatic drug metabolizing enzymes are known as the ____ system
P450
92
P450 system consists of __ families
12
93
__ of these 12 enzyme families metabolize drugs (CYP 1,2,3)
3
94
__ of these 12 families metabolize steroids and fatty acids
9
95
CYP ____ has the same #
family (ex. CYP1)
96
CYP _____ has the same # and letter
subfamily (ex. CYP1A)
97
CYP _____ has the #, letter, #
gene/isoenzyme
98
ox = ?
losing electrons
99
red = ?
gaining electrons
100
inhibitors and inducers affect?
half life mainly (but also all those other parameters) *metabolizing enzyme is being influenced
101
enzyme inducers affect metabolism how?
speed up metabolism
102
enzyme inhibitors affect metabolism how?
slow down metabolism
103
pharmacokinetics of metabolism inducer?
affects concentration, increased clearance, decreased half life
104
pharmacodynamics of metabolism inducer?
measures the drug effect (response)
105
an inhibitor ____ drug metabolism
blocks (stops)
106
an inhibitor therefore causes an ____ response (PD)
increased (you are blocking metabolism/ breakdown of the drug so therefore drug stays in body and will have a higher response)
107
an inhibitor causes an ____ plasma t1/2 life (PK)
increased (you are blocking metabolism of the drug so it stays in body longer = therefore higher half life)
108
an inhibitor's effects are ____?
immediate
109
an inducer causes ____ drug metabolism
increased
110
therefore an inducer causes ___ drug response (PD)
decreased (you are speeding up metabolism so therefore drug will be broken down at a faster rate and there will be less left over to create a drug response)
111
an inducer causes ____ plasma t1/2
decreased (drug is leaving body faster = therefore decreased half life)
112
an inducer's effects are ____
delayed
113
PK affects ??
concentration of the drug
114
PD affects ???
the drug's affect/ response
115
aspirin + warfarin = ?
hemorrhage
116
erythromycin + seldane = ?
fatal arrhythmia
117
CNS depressant + CNS depressant (ex. alcohol) = ?
respiratory depression (could be even death)
118
viagra + nitroglycerin = ?
fatal hypotension (drop in BP)
119
ACE inhibitors + K-sparing diuretics = ?
hyperkalemia (higher than normal levels of potassium)
120
example of enzyme inhibitor
cimetidine
121
What is cimetidine-H2 receptor antagonist used to treat?
peptic ulcer
122
Possible drug interactions with cimetidine-H2 receptor agonist?
warfarin benzos phenytoin morphine
123
drugs are designed for what type of metabolizer?
extensive metabolizers
124
if you're a poor metabolizer what are you at risk of?
increased toxicity
125
if you're an ultra extensive metabolizer what are you at risk of?
reduced response
126
_____ have highest frequency of PM phenotype
caucasians
127
_____ have highest frequency of IM phenotype
asians
128
_____ have highest frequency of UM phenotype
africans
129
more copies of allele that is expressive to the enzyme means ?
more metabolism
130
List the 6 things that can cause variations in drug metabolism
``` induction diet inhibition genetics development disease ```
131
rate of drug disposition is impaired in what age groups
very young | very old

Pharmacology (21 decks)

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