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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
the more vascular the tissue is...
the more distribution of drug (also easier to wash out of those areas)
26
Which tissue is least vascular?
adipose
27
metabolism
inactivation of drug by enzymes
28
primary organ for metabolism
liver
29
cytochrome P450 enzymes
make it easier to excrete in urine
30
each enzyme can metabolize _____. Each drug can be metabolized by ______.
different drugs different enzymes
31
CYP3A4
most common metabolic enzyme involved in drug interactions
32
phase I reaction
oxidation, reduction, hydrolysis small changes to the functional group
33
phase II reactions
conjugation (larger, bulkier molcules)
34
do molecules have to undergo both phase reactions sequentially?
no! can go through one or the other (or both)
35
general purpose of metabolism reactions
makes molecules more water soluble to allow excretion in urine
36
1st order kinetics
drug concentration affects rate (higher concentration = higher rate) (exponential decrease)
37
zero order kinetics
drug concentration does not affect metabolic rate (linear decrease in concentration)
38
zero order reactions are due to
saturation
39
enzyme induction
more of the enzyme = more of a drop in drug concentration because metabolized faster
40
alcohol will cause induction of ___ mediated pathways which is one way to get enhanced ____
P450 NADPQI
41
if you take too much _____ and overwhelm the ______ and _____ pathways, get more NADPQI
acetaminophen glucuronidation sulfation
42
at what point does NAPQI become toxic?
have a limited pool of glutathione when you run out of GSH, NAPQI becomes toxic
43
GSH
glutathione is detoxified and allowed to be released from the body
44
inhibition
decreased enzyme capacity
45
less metabolism (impact on drugs)
drug accumulation
46
notorious inhibiting agents
grapefruit juice medications
47
warfarin (coumadin)
oral anticoagulate
48
warfarin requires
active vitamin K for synthesis of clotting factors
49
warfarin prevents vitamin K from
reactivating by inhibiting vitamin K epoxide reductase complex (VKORC)
50
CYP2C9 impact on warfarin (steps)
1. reduces warfarin metabolism 2. allows more prevention of Vit K re-activation 3. decrease synthesis of clotting factors 4. increased bleeding
51
prodrugs
administered in inactive form (to promote absorption)
52
prodrugs require
metabolic activation by the body
53
codeine
prodrug of morpheine
54
what is the only enzyme that can cause codeine to become active?
CYP2D6
55
excretion
removal of metabolites or unchanged active drug from body
56
two main organs for excretion
kidney and liver
57
biliary excretion
occurs through bile duct
58
enterohepatic cycling helps to...
maintain a higher drug level than what would be maintained if excretion was a one way path
59
sequence for enterohepatic cycling
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
excretion = filtration ____ secretion ____ reabsorption
+ -
61
lipid soluble drugs are reabsorbed in the ____ by _____
renal tubules passive diffusion
62
can ionized / hydrophilic drugs be reabsorbed?
no - excreted in urine
63
what does alkalization of urine lead to?
excretion of weak acids
64
maintaining ideal drug concentration can be affected by
-administration route -dose amount -dose interval -drug half life -tissue distribution
65
intrinsic drug toxicity
reproducible (all patients at risk)
66
is intrinsic drug toxicity dose dependent?
yes
67
the results of actions of intrinsic drug toxicity happen at ...
the target receptor (or affects other receptors)
68
idiosyncratic drug toxicity
not widely reproducible (in small subset of patients)
69
idiosyncratic drug toxicity example
hypersensitivity / allergic reactions
70
clearance is a way to...
collectively quantify all of the processes that make active drugs disappear from the body
71
clearance is calculated by
rate of elimination relative to drug concentration amount of plasma that would have been cleared in order to account for disappearance of drug
72
volume of distribution
how much drug is dissolved in body
73
half life
time it takes for drug concentration to decrease by half
74
how many half lives does it take to remove drug completely from system?
5
75
bioavailability
fraction of original dose that reaches systemic circulation
76
bioavailability for IV
100%
77
main obstacle with oral administration of drug
concentration is greatly reduced before it reaches systemic circulation

Pharmacology (6 decks)

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