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pharmacology i > L2-3: Pharmacokinetics > Flashcards

L2-3: Pharmacokinetics Flashcards

1
Q

water soluble + lipid soluble drugs penetrate cellular membranes through ____ diffusion

A

passive (simple)

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2
Q

3 types of carrier-mediated trasnport

A
  • structure specific
  • competition
  • Tmax
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3
Q

a ______ drug in an acidic medium (like stomach) is ______ ionized and more lipid soluble = rapidly absorbed

A

weak acidic drug
less ionized

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4
Q

if a drug is less ionized, how does this affect its ability to be absorbed

A

less ionized = absorbed quickly

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5
Q

what happens if a weak basic drug diffuses into an acidic medium

A

drug becomes ionized and will accumulate

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6
Q

why aren’t strong acids and bases lipid souble (cannot penetrate lipid membranes by passive diffusion)

A

they are always ionized in the body
ionized = not lipid soluble

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7
Q

what is ion trapping

A

acids accumulate in basic env
bases accumulate in acidic env

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8
Q

what causes an increase in the elimination of bases in urine

A

making the urine more acidic w/ ammonium chloride

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9
Q

what causes an increase in the elimination of acids in urine

A

making the urine more basic by sodium bicarbonate

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10
Q

the amount of active drug available at the site of action

A

bioavailability

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11
Q

what is the bioavailability of IV administered drugs

A

100%

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12
Q

disadvantages of oral administration

A
  • emesis (irritation of intestinal mucosa)
  • irregularities in abs
  • metabolism by intestinal flora
  • abs drug is exposed to liver
  • gastric emptying time
  • binidng to food
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13
Q

sites in body where drugs accumulate

A

Fat, Tissues, Bone

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14
Q

what is the main goal of biotransformation

A

promotion of elimination from the body

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15
Q

what does permeability glycoprotein (Pgp) aka multidrug resistance protein 1 (MDRI) do?

A

uses ATP to pump out substrates across cellular membranes
it is extensively distributed

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16
Q

factors affecting absorption

A
  • solubility
  • dissolution
  • concentration
  • blood flow
  • absrobing surface
  • pH
  • contact time
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17
Q

bioavailability is a result of ….

A
  • decomposition/inactivation of drug in intestine
  • degree of absorption
  • metabolism in gut wall or liver
  • transport of drug by P glycoproteins back to the lumen of the gut
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18
Q

term for the initial metabolism of drug as it passes through gut and liver

A

first pass effect

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19
Q

what are the sites of drug exclusion

A
  • CSF
  • ocular fluid
  • endolymph fluid
  • fetal fluid
  • pleural fluid
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20
Q

what is the apparent volume of distribution (Vd)?

A

total amount of drug in body / concentration of drug in plasma

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21
Q

what does a very low Vd indicate about the presence of a drug

A

drug is mostly present in the plasma (blood)

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22
Q

what does a high Vd indicate about the presence of a drug

A

drug is extensively distributed and binds extensively with peripheral tissues

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23
Q

drugs with very high plasma protein binding have ______ Vd

A

low

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24
Q

common characteristics of most pharmacologically active drugs

A
  • lipid soluble
  • unionized or partially ionized
  • storngly bound to plasma proteins and other tissues
  • not readily excreted by kidney
  • remain in body for a long time
25
Q

Phase I reactions convert ______ soluble parent compounts into more _________ metabolites (meaning they are ______ soluble)

A

lipid solible compounds into more polar metabolites = less lipid solible

26
Q

phase I metabolites are usually _______ and readily ________

A

inactive, excreted

27
Q

phase I reactions usually introduce or unmask certain ___________

A

functional groups
ex: OH, SH, NH2

28
Q

what are the 2 types of Phase I reactions?

A

Microsomal: inducible reactions that occur in the ER
Non-microsomal: non inducible

29
Q

Phase I reactions are NOT _______ specific

A

compound

30
Q

type of Phase I reactions that come from ER, layers of enzyme+lipid layers that can metabolize lipid soluble drugs

A

Microsomal

31
Q

Phase II reactions make drugs…

A

more polar, of larger molecular weight, and more inactive

32
Q

what is the only Phase II reaction which is microsomal (therefore inducible)

A

Glucuronidation

33
Q

what are the 2 most common CYP450 enzymes

A

CYP 3A4 and CYP 2D6

34
Q

Phase II reactions are the _________ of drug via __________ enzymes

(Ex: glucuronidation, acetylation, sulfation, methylation, etc)

A

conjugation
transferase

35
Q

what type of biotransformtion (phase I or II) do glucuronidation, acetylation, sulfation, methylation fall under

A

phase II

36
Q

what are the types of enzymes that fall into non-microsomal phase I reactions

A
  • esterases + amidases
  • monoamine oxidases
  • alcohol and aldehyde dehydrogenases
37
Q

endogenous amines (Catecholamines, serotonin) are what type of nonmicrosomal enzymes

A

monoamine oxidases

38
Q

CYP 450 inducers ?
Riley
Barfs
Penis
Goo
She just wont (swallow)

A

rifampin
barbiturates
phenytoin
glucocorticoids
st. john’s worts

39
Q

what are the P450 inhibitors?
Candy Dildos Keep Every Vagina Functioning

A

cimetidine
diltiazem
ketoconazole
erythromycin
verapamil
fluoxetine

40
Q

3 methods of renal excretion of drugs and drug metabolites

A
  • glomerular filtration in the PT
  • active tubular secretion or reabsorption
  • passive diffusion across tubular epithelium
41
Q

measure of the capacity of the body to remove the drug

A

clearancce

42
Q

proportionality constant that relates the rate of drug elimintation to its plasma concentration

A

clearance

43
Q

Explain the Two Compartment Model (biexponential) of drug pharmacokinetics

A
  • distribution of drug is not instantaneous
  • Vd (distribution of volume) becomes larger until equilibrium is reached
  • intial decline in drug [ ] is fast due to elimination and distribution occurring
  • the later decline in the plasma drug [ ] is only due to elimination (slower)
44
Q

in the two compartment model, the intitial decline in drug [ ] is due to what?

A

fast elimination and distribution

45
Q

in the two compartment model, the secondary decline in drug [ ] is due to what?

A

elimination only (slower)

46
Q

the elimination of most drugs from the body follows ______ kinetics, meaning that a constant proportion of the drug is eliminated per unit of time

A

exponential

47
Q

what assumptions are made when describing a drug’s half life ?

A
  • body is a single compartment
  • body size is = to Vd
  • drug is distributed equally throughout body
  • drug in plasma is in equilibrium w/ total volume
48
Q

what type of elimination does this graph show

A

zero order elimination
elimination process gets saturated after a high dose

49
Q

what type of elimination does this graph show

A

first order

50
Q

to reach immediate therapeutic concentration, a ____________ dose is used

A

loading

51
Q

Loading Dose = _____ x _____

A

Vd x TC (target concentration)

52
Q

is a loading dose dependent on the half life or clearance of a drug?

A

no

53
Q

repeated administration (same dose at same dosing intervals) results in a _________ concentration of the drug in plasma

A

steady state

54
Q

it takes at least _______ half lives to obtain a steady state plasma level

A

5

55
Q

shortening the _______interval will result in a higher steady state concentration

A

dosing

56
Q

what is the effect on steady state concentration of the dosing interval length is increased

A

lower steady state

57
Q

is the time required to reach steady state levels related to the size of the dose?

A

no

58
Q

where is permeability glycoprotein (P-gp) expressed

A
  • intestinal mucosa
  • hepatocytes
  • renal proximal tubular cells
  • adrenal gland
  • capillary endothelial cells of the BBB
59
Q

Do Vd values represent their actual distribution in the body fluid

A

no
Vd is a conceptual figure

pharmacology i (21 decks)

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