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Pharmacology > Pharmacokinetics (main slideshow up until slide 29) > Flashcards

Pharmacokinetics (main slideshow up until slide 29) Flashcards

I split the slideshow in half to make it easier to study (78 cards)

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1
Q

what is the most common mechanism used by drugs to cross membranes

A

passive diffusion

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2
Q

when will a weak base be better absorbed

A

in basic conditions

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3
Q

what is the formula for the therapeutic index

A

Index=TD50/ED50

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4
Q

what is the pH in the mouth

A

7

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5
Q

name some drugs highly bound to plasma proteins

A

warfarin
phenytoin
diazepam

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6
Q

how does the GI surface area affect bioavailability

A

if intestinal SA is low, less drugs can be absorbed, therefore F is reduced

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7
Q

drugs that are weak bases can either exist as:

A

B or BH+

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8
Q

pH of the intestine

A

5-8

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9
Q

why MUST drugs pass through cells in the brain to get in or out

A

tight junctions in the brain capillaries do not permit drugs to filter through gaps in cells

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10
Q

if binding to plasma proteins is high, then Vd=

A

low

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11
Q

what is the ideal bioavailability

A

100%

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12
Q

what organs have a medium blood flow relative to size

A

skeletal muscles

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13
Q

when will a weak base drug be found mostly in the B form

A

when surrounded by basic conditions

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14
Q

what is the second most common mechanism used by drugs to cross membranes

A

protein-assisted transport

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15
Q

if a drug is highly bound to tissues, how does this affect the Vd

A

it’s typically higher

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16
Q

what symbol do we use for bioavailability

A

F

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17
Q

why is a weak base poorly absorbed in acidic conditions

A

it will exist in the HB+ form, which is charged and cannot diffuse passively

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18
Q

what are the only substances absorbed through the BBB

A

lipid-soluble drugs
charged drugs transported by specialized proteins

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19
Q

what is protein-assisted transport usually associated with

A

drugs being eliminated

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20
Q

what does secondary active transport use for energy to get drugs across the cell membrane

A

ion gradient from ATP dependent transport

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21
Q

name 3 things that causes the AUC to decrease

A

lower drug does
lower bioavailability
higher drug clearance

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22
Q

what does having low affinity mean

A

weaker bonds between molecules

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23
Q

what kind of meal would slow gastric emptying

A

high calorie
high fat
acidic meals

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24
Q

total body water is estimated to be what percent of a patient’s mass

A

60

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25
what does primary active transport use for energy to get drugs across the cell membrane
ATP
26
interactions of plasma proteis with drugs are ____ affinity and ____ capacity (high or low for either blank)
low affinity high capacity
27
name some reasons an oral drug would have F<100%
intestine doesnt absorb all the drug drug modified by intestinal/hepatic enzymes drug secreted back into the intestine
28
what is filtration
diffusion through pores
29
what organs have a low blood flow relative to size
fat skin bones
30
when will a weak acid drug be found mostly in the HA form
when it is surrounded by acidic conditions
31
what organs have a high blood flow relative to size
kidney heart lungs brain liver
32
If intestinal motility is high, how does that affect bioavailability
F is reduced due to increased speed of transit
33
drugs that are weak acids can either exist as:
A- or HA
34
what kind of drugs can cross cell membranes through passive diffusion
gases hydrophobic molecules small polar, uncharged molecules
35
in practice, how do you calculate the oral bioavailability of a drug
comparing the auc from the oral route to the auc from the iv route
36
intracellular water is estimated to be what percent of a patient's mass
40
37
what is the therapeutic index
ratio comparing the toxic does in 50% of the population to the effective dose in the same population
38
name 2 reasons to have enteric coated drugs
to protect the stomach against the pill or to protect the pill against the stomach
39
how is the Vd affected if a drug is highly bound to plasma proteins
Vd tends to be small
40
ED50
effective dose in 50% of the population
41
proteins and peptides are usually confined where? why?
to the extracellular space since they cannot readily cross cell membranes
42
name 2 GI motility factors that affect bioavailability
rate of gastric emptying rate of intestinal emptying
43
what type of charge must a drug have to passively diffuse through a membrane
neutral charge
44
what is volume of distribution
apparent volume into which a drug disperces in order to produce the observed plasma drug conc
45
what are the 4 main types of movement across cell membranes
passive diffusion facilitated diffusion active transport endocytosis
46
drugs with which characteristics cannot cross cell membranes through passive diffusion
large polar molecules charged molecules
47
what is more likely to affect the speed of a drugs dissolution/absorption than it's bioavailability
the form of the drug
48
if tissue-binding is high, then Vd=
high
49
what is the margin of safety
the ratio between ED99 and TD1 (effective dose in 99% of the pop and toxic dose in 1%)
50
when will a weak acid drug absorb best
when in acidic condition
51
how does drinking a lot of liquid affect bioavailability
tend to accelerate gastric emptying (increases F)
52
when does F=100%
when the drug is administered directly into a patients blood vessels
53
how can food affect bioavailability of weak acids and bases
it can change the pH of the liquid in which the drug is found, and therefore affect its charge
54
why can an increase in free drugs due to drug-drug interactions affecting plasma protein binding be dangerous
you'll have calculated the dose for the expected percentage of drugs to be bound, and if less become bound, and more are free, there could be an overload of the drugs in the system
55
if intestinal motility is low, how does that affect bioavailability
F could be increased (if not already at max)
56
if you have two drugs with different affinities for plasma proteins, which one will bind
the one with a higher affinity
57
what does the AUC represent
the total amount of drug that enters the body over time
58
pH of the stomach
1.5-2
59
what is one downside to protein-assisted transport
it has limited capacity and saturable mechanisms
60
name 3 reasons drug-drug interactions affecting binding of plasma proteins can be clinically relevant
initial drug is highly bound to plasma proteins therapeutic index of the initially bound drug is narrow effectiveness of elimination systems are reduced
61
what 3 things affect the range and timing of drug distribution
lipid solubility if the drug is highly bound to plasma proteins/if it accumulates within certain tissues blood flow relative to organ size
62
what is passive diffusion driven by
drug concentration gradient on either side of the cell membrane
63
extracellular water is estimated to be what percent of a patient's mass
20
64
what kind of drugs would be transported via endocytosis or pinocytosis
very high molecular weight drugs
65
when will a weak base be poorly absorbed
in acidic conditions
66
what is bioavailability
the fraction of unchanged drug that reaches the systemic circulation
67
what does AUC stand for
area under the curve
68
how do you calculate the dose needed to acheive a desired therapeutic con
dose = therapeutic conc*Vd
69
when will a weak acid drug be found mostly in the A- form
in basic pH conditions
70
only ____ drugs can leave BVs, cross membranes, bind to receptors and be excreted by the kidney
free (unbound)
71
when will a weak base drug be found mostly in the HB+ form
when surrounded by acidic conditions
72
what can lead to poor absorption of a weak acid drug
basic pH conditions - allows it to exist in the A- form which is charged and therefore cannot diffuse passively
73
facilitated diffusion has membrane proteins using energy provided by what to move drugs across the membrane?
the concentration gradient
74
name 3 things that causes the AUC to increase
higher drug dose higher bioavailability lower drug clearance
75
if gastric emptying is slow, how does that affect bioavailability
F is reduced (due to prolonged exposure to low pH and gastric enzymes)
76
TD50
toxic dose in 50% of the population
77
passive diffusion requires drugs to be _____soluble
lipid
78
what doe Vd stand for
volume of distribution

Pharmacology (22 decks)

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