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Pharmacology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

4 actions of the body on a drug

A
  1. absorption
  2. distribution
  3. metabolism
  4. excretion / elimination
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2
Q

two ways drugs can be absorbed into body?

A
  1. transported across membrane through carrier protein / endocytosis
  2. diffuse across lipid bilayer
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3
Q

partition coefficient

A

amount in oil vs amount in H2O

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4
Q

drugs that have highest oil / water coefficient… (high or low lipid solubility?)

A

are the most lipid soluble

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5
Q

high partition coefficient = (high or low absorption rate?)

A

high absorption rate

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6
Q

ionization

A

many drugs are week acids or bases… ionization makes a polar molecule (not good, will not cross membrane)

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7
Q

weak acid

A

unionized form has proton on it and then can lose H+ to become ionized

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8
Q

when pH = pKa…

A

50% ionized

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9
Q

weak acids have (high or low) pKa

A

high

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10
Q

if 3 pH units above above pKa…

A

almost 100% ionized

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11
Q

if 3 pH units below the pKa…

A

alost 100% in nonionized state

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12
Q

pH trapping

A

ideal for the drug to be in the nonionized form in stomach and then be able to be in ionized form in the plasma

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13
Q

once drug gets into blood plasma… it becomes _____

A

ionized (it is INHIBITED from crossing over through the lipid bilayer)

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14
Q

local anesthetics block ______ that carry APs down the axon

A

voltage gated Na+ channels

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15
Q

drug must bind ______ portion fo the voltage gated Na+ channel

A

intracellular

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16
Q

three important properties of anesthetics

A
  1. solubility
  2. ability to cross membrane
  3. charge
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17
Q

if anesthetic is poorly hydrophobic (hydrophilic)…

A

can’t cross so the anesthetic block can’t occur

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18
Q

if anesthetic is moderately hydrophobic…

A

crosses, so block can occur (we want this!)

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19
Q

if anesthetic is extremely hydrophobic…

A

tries to cross and then gets stuck in membrane… block cannot occur

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20
Q

are weak bases (low pH) ionized or nonionized?

A

ionized

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21
Q

are weak acids (high pH) ionized or nonionized?

A

nonionized

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22
Q

the lower the pH of weak base…

A

more likely to become ionized

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23
Q

inflamed tissues are more (basic or acidic)?

A

acidic (lower pH)

might need larger dose of anesthetic to inflamed tissue

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24
Q

Solutes must be ______ to cross BBB and enter the brain

A

lipid soluble

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25
Q

the more vascular the tissue is…

A

the more distribution of drug
(also easier to wash out of those areas)

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26
Q

Which tissue is least vascular?

A

adipose

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27
Q

metabolism

A

inactivation of drug by enzymes

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28
Q

primary organ for metabolism

A

liver

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29
Q

cytochrome P450 enzymes

A

make it easier to excrete in urine

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30
Q

each enzyme can metabolize _____. Each drug can be metabolized by ______.

A

different drugs
different enzymes

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31
Q

CYP3A4

A

most common metabolic enzyme involved in drug interactions

32
Q

phase I reaction

A

oxidation, reduction, hydrolysis

small changes to the functional group

33
Q

phase II reactions

A

conjugation (larger, bulkier molcules)

34
Q

do molecules have to undergo both phase reactions sequentially?

A

no! can go through one or the other (or both)

35
Q

general purpose of metabolism reactions

A

makes molecules more water soluble to allow excretion in urine

36
Q

1st order kinetics

A

drug concentration affects rate (higher concentration = higher rate) (exponential decrease)

37
Q

zero order kinetics

A

drug concentration does not affect metabolic rate (linear decrease in concentration)

38
Q

zero order reactions are due to

A

saturation

39
Q

enzyme induction

A

more of the enzyme = more of a drop in drug concentration because metabolized faster

40
Q

alcohol will cause induction of ___ mediated pathways which is one way to get enhanced ____

A

P450
NADPQI

41
Q

if you take too much _____ and overwhelm the ______ and _____ pathways, get more NADPQI

A

acetaminophen
glucuronidation
sulfation

42
Q

at what point does NAPQI become toxic?

A

have a limited pool of glutathione

when you run out of GSH, NAPQI becomes toxic

43
Q

GSH

A

glutathione is detoxified and allowed to be released from the body

44
Q

inhibition

A

decreased enzyme capacity

45
Q

less metabolism (impact on drugs)

A

drug accumulation

46
Q

notorious inhibiting agents

A

grapefruit juice
medications

47
Q

warfarin (coumadin)

A

oral anticoagulate

48
Q

warfarin requires

A

active vitamin K for synthesis of clotting factors

49
Q

warfarin prevents vitamin K from

A

reactivating by inhibiting vitamin K epoxide reductase complex (VKORC)

50
Q

CYP2C9 impact on warfarin (steps)

A
  1. reduces warfarin metabolism
  2. allows more prevention of Vit K re-activation
  3. decrease synthesis of clotting factors
  4. increased bleeding
51
Q

prodrugs

A

administered in inactive form (to promote absorption)

52
Q

prodrugs require

A

metabolic activation by the body

53
Q

codeine

A

prodrug of morpheine

54
Q

what is the only enzyme that can cause codeine to become active?

A

CYP2D6

55
Q

excretion

A

removal of metabolites or unchanged active drug from body

56
Q

two main organs for excretion

A

kidney and liver

57
Q

biliary excretion

A

occurs through bile duct

58
Q

enterohepatic cycling helps to…

A

maintain a higher drug level than what would be maintained if excretion was a one way path

59
Q

sequence for enterohepatic cycling

A
  1. drug in the liver secreted into bile
  2. stored in the gallbladder
  3. released into small intestine
  4. drug reabsorbed back into circulation and subsequently returned to liver
60
Q

excretion = filtration ____ secretion ____ reabsorption

A
61
Q

lipid soluble drugs are reabsorbed in the ____ by _____

A

renal tubules
passive diffusion

62
Q

can ionized / hydrophilic drugs be reabsorbed?

A

no - excreted in urine

63
Q

what does alkalization of urine lead to?

A

excretion of weak acids

64
Q

maintaining ideal drug concentration can be affected by

A

-administration route
-dose amount
-dose interval
-drug half life
-tissue distribution

65
Q

intrinsic drug toxicity

A

reproducible (all patients at risk)

66
Q

is intrinsic drug toxicity dose dependent?

A

yes

67
Q

the results of actions of intrinsic drug toxicity happen at …

A

the target receptor (or affects other receptors)

68
Q

idiosyncratic drug toxicity

A

not widely reproducible (in small subset of patients)

69
Q

idiosyncratic drug toxicity example

A

hypersensitivity / allergic reactions

70
Q

clearance is a way to…

A

collectively quantify all of the processes that make active drugs disappear from the body

71
Q

clearance is calculated by

A

rate of elimination relative to drug concentration

amount of plasma that would have been cleared in order to account for disappearance of drug

72
Q

volume of distribution

A

how much drug is dissolved in body

73
Q

half life

A

time it takes for drug concentration to decrease by half

74
Q

how many half lives does it take to remove drug completely from system?

A

5

75
Q

bioavailability

A

fraction of original dose that reaches systemic circulation

76
Q

bioavailability for IV

A

100%

77
Q

main obstacle with oral administration of drug

A

concentration is greatly reduced before it reaches systemic circulation

Pharmacology (6 decks)

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