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Biopharm Exam 2 > Chapter 6 - Drug Elimination > Flashcards

Chapter 6 - Drug Elimination Flashcards

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1
Q

Differentiate between elimination and excretion

A

the terms are pretty much interchangeable

the removal of waste products of metabolism from the blood, through the action of the kidneys

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2
Q

is it possible for things to be excreted unchanged

A

yes - can either be unchanged or as metabolites

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3
Q

around what % of drug is excreted renally? are there any things that can’t be excreted renally?

A

over 90% of drug is excreted renally

however, only small substances that can undergo passive diffusion are able to be filtered through the kidney

(less than 300 MW, POLAR AND HIGHLY IONIZED WATER SOLUBLE COMPOUNDS)

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4
Q

Name 6 routes of drug excretion that are NOT renal

A

lungs
perspiration (sweat)
biliary (enterohepatic circulation)
salivary
fecal
milk

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5
Q

what kind of substances are excreted through the lungs?
give a specific example

A

volatile substances, such as alcohol

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6
Q

is alcohol eliminated through the lungs via 1st or zero order elimination?

as a recap, briefly differentiate between 1st and zero order

A

zero order

the rate of elimination is CONSTANT and is independent of concentration

first order elimination IS concentration dependent

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7
Q

what kind of drug substances are excreted through perspiration (sweat)

A

low MW

water soluble electrolytes like NaCl

non-electrolytes like garlic

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8
Q

which is a more GENERAL term - elimination or excretion

A

excretion

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9
Q

true or false

high molecular weight drug molecules are excreted through perspiration

A

FALSE - low MW

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10
Q

*biliary excretion is for ____ molecules

A

LARGE - over 500 MW

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11
Q

*biliary excretion is also known as….

A

enterohepatic circulation

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12
Q

drugs with a molecular weight exceeding _____ are too large to be eliminated through the kidney

A

MW of 500

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13
Q

enterohepatic circulation is also known as what kind of excretion

A

biliary excretion

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14
Q

the pH of the saliva ranges between….

A

5.5-7.8

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15
Q

the ____/____ ratio is used
to determine if a drug can undergo TDM (therapeutic drug monitoring) through the saliva instead of the plasma (less invasive)

A

salivary/plasma ratio

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16
Q

“un-recycled biliary secretion”

A

fecal excretion

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17
Q

fecal excretion is the excretion of drugs through ____

A

the intestines

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18
Q

the presence of drug in the feces can be due to what 2 things

A

either the drug was incompletely absorbed OR due to biliary excretion - difficult to tell

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19
Q

pH of breast milk

A

6.6

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20
Q

do acidic or basic drugs tend to be excreted through the milk? why?

A

basic drugs

bc they will be ionized in the acidic (6.6pH) environment of the breast milk

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21
Q

again - explain what kind of drugs are eliminated renally and why is this

A

small MW (less than 300), polar, highly ionized, water soluble compounds

these drugs tend to stay in the plasma, and our kidney is related to the plasma

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22
Q

2 tests that are most commonly used to evaluate kidney function

A

excretion ratio (ER)
effective renal plasma flow (ERPF)

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23
Q

formula for excretion ratio

A

ER = Carterial - Crenal / C arterial

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24
Q

the ER (excretion ratio) ranges from ___ to ___

explain what a low vs high value means

A

0-1

0 means not removed and 1 means 100% removed by the kidney

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25
if a drug is highly protein bound, will it have a low or high excretion ratio
if the drug is highly protein bound -- it will be a low ER. the kidney is unable to separate the drug from the plasma protein - can only eliminate free drug
26
what does an ER of zero mean in terms of arterial/venous drug concentration
when ER is 0, it means that the renal concentration of the drug is equal to the ARTERIAL concentration of the drug -- meaning that no drug was excreted through the kidneys
27
what does an ER of 1 mean
the renal concentration of the drug is zero and all is in the arteries - 100% excreted through the kidneys the numerator equals the denominator - can only happen when the renal concentration of drug is zero
28
do arteries or veins carry drug to organs
arteries
29
true or false if ER is high, that means a lot of drug is in the veins
true - removed by the kidney
30
the ER value is 0.35 explain what this means
the renal concentration is 65% of the arterial concentration most drug is still in the arteries!
31
what is used as the "measure" of renal plasma flow in the ERPF equation
PAH (p-aminohippuric acid) 650mL/min
32
what is a normal range of renal plasma flow
590-695mL/min
33
as mentioned, a normal range of renal plasma flow is 590-695mL/min of this, what % undergoes FILTRATION by the glomerulus?
around 20% --- so like 118-140 or 130mL/min is passive glomerular filtration/minute
34
average MOVEMENT OF BLOOD/min
1L per minute -- but like 40-45% of that is cells -- we only care about the plasma flow - 590-695mL/min
35
inulin GFR
130mL/min
36
if a drug only undergoes passive filtration, drug clearance = _________
renal clearance (130mL/min)
37
true or false glomerular filtration does not follow Fick's first law
false - it does
38
3 factors that influence glomerular filtration
the surface area available for filtration the permeability of the filtration membrane the net filtration pressure
39
what is the net filtration pressure in the kidney? what is this pressure created by?
10mmHg created by membrane/glomerular tissue
40
true or false the glomerular capillaries have a huge surface area available for filtration
TRUE
41
name 2 things that can be used to determine glomerular filtration rate and why
manitol and inulin they are only removed by filtration and do not undergo metabolism and do not affect the filtration rate
42
true or false drug clearance usually only depends on GFR
true
43
2 mechanisms in which a drug goes from the blood to the glomerular filtrate
glomerular filtration (passive) tubular secretion (active)
44
is the kidney ever able to dissociate the drug-protein complex
yes - in the case of tubular secretion
45
tubular secretion is sometimes done to eliminate undesirable substances that have been reabsorbed by passive diffusion name 2 of these substances
urea and uric acid
46
true or false tubular secretion does not control blood pH
false - it does
47
how is tubular secretion related to potassium ions
tubular secretion is done to remove excess potassium ions from the body bc potassium ions in the filtrate are automatically reabsorbed in the PCT -- the active tubular secretion mechanism removes these potassium ions out from the body
48
true or false tubular secretion mechanism can be used to dispose substances that are NOT already in the filtrate
true
49
the active tubular secretion process follows....
michaelis-menten concept competitive - binding site with carrier
50
true or false in tubular secretion, the drug is being carried with its concentration gradient
FALSE - against the concentration gradient
51
true or false the active tubular secretion of drugs does not have an upper rate limit of transport
false - it does. the system can be saturated! follows michaelis-menten kinetics. there will be a maximum rate once all of the carriers are saturated
52
true or false the active tubular secretion process can be blocked by metabolic inhibitors
true
53
true or false the tubular secretion process is a noncompetitive secretory transport mechanism
false - competitive
54
give 2 general examples of things that undergo active tubular secretion
acids (anions) and bases (cations)
55
tubular REABSORPTION may be considered a _____ process that begins when?
RECLAMATION process begins as soon as the filtrate enters the proximal tubules
56
the reabsorption of ACIDIC DRUGS is enhanced under acidic or basic conditions and why?
acidic conditions - will be unionized and readily reabsorbed across the renal tubule membrane
57
the reabsorption of BASIC DRUGS is enhanced under acidic or basic conditions and why
basic conditions bc the drug will be unionized and readily reabsorbed across the renal tubule membrane
58
true or false weakly basic drugs are more ionized in an acidic environment
true
59
for acidic drugs, if the ph-pka is ______, the drug will be more than 99% ionized and thus not be reabsorbed
2 or more
60
true or false for ACIDIC DRUGS, the higher the difference between pH-pka, the more ionized is the drug
true
61
explain the rationale of reabsorption for a drug that treats a UTI
we dont want a UTI drug to be reabsorbed back into the body - we want it to stay in the urinary tract to treat the infection thus, we want it to be ionized so it's not reabsorbed
62

Biopharm Exam 2 (6 decks)

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