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pharm1 S.Horvath > lecture 1 - pharmacokinectics > Flashcards

lecture 1 - pharmacokinectics Flashcards

1
Q

First pass metabolism. what is it?

A

a phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation. when a drug is absorbed across the GI membrane, it enters the hepatic portal system, which carries the drug molecules directly to the liver.

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2
Q

absorption of sublingual/buccal - goes where?

A

drains to vena cava. (bypasses GI tract)

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3
Q

absorption of sublingual/buccal - speed?

A

rapid

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4
Q

sublingual/buccal drugs must be

A

highly lipid soluble and potent

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5
Q

if you have poor blood flow to a cut and put a topical on it you will have poor

A

absorption

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6
Q

p-glycoproteins- where are they?

A

membranes. they are found all over the kidney, color, BBB, jejunum, liver, pancreas, etc.

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7
Q

p-glycoproteins- what are they?

A

family of transfer proteins. important for med interactions and drug resistance.

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8
Q

what do p-gloycoproteins require for transport

A

ATP

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9
Q

total body water

A

.65L/kg

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10
Q

average adult plasma volume is

A

Vd= 3 liters

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11
Q

what does volume of distribution assume?

A

that a sample of peripheral blood is homogenous throughout the body. sometimes called “apparent” volume of distribution

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12
Q

volume of distribution definition

A

size of compartment necessary to account for the total amount of drug in the body if it were present throughout the body at the same concentration found in the plasma.

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13
Q

are SQ and IM lipophilic or hydrophilic ?

A

lipo

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14
Q

injectable meds are absorbed by what process

A

simple diffusion

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15
Q

bioavailability of subcutaneous meds is

A

100

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16
Q

inhaled meds absorption

A

rapid due to large surface area, avoid first pass, local site of action, difficult to control

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17
Q

how does temp affect absorption

A

increases

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18
Q

topical meds need to be

A

highly lipophilic

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19
Q

first pass metabolism

A

the concentration of a drug is greatly reduced before it reaches the systemic circulation

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20
Q

how to figure out new dose if you have the current dose, its bioavailability, and the new dose’s bioeval

A

new dose = f old (current dose) / f (new)

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21
Q

concept of bioavailability as a percentage

A

so (f) is a percentage of the oral dose that is becoming into the general circulation. and because you’re giving IV meds right into the circulation pt gets the whole dose

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22
Q

100 mcg PO, 75% bioavailable. whats the IV dose?

A

75mcg

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23
Q

salts at the end of the drug like tartrate

A

can change bioavailability and duration of action

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24
Q

100 mcg IV, 50% bioavailable IV–>PO dose?

A

200mcg

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25
Q

factors that affect bioavailability

A

dissolution and absorption characteristics, route, stability in GI tract, metabolism prior to blood stream

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26
Q

absorption definition

A

the movement of drug molecules a cross membrane and into the bloodstream

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27
Q

bioavailability (F) definition

A

% of med that reaches systemic circulation

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28
Q

pharmacodynamics

A

the effects of a drug on the body

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29
Q

pharmacokinetics

A

the effect of the body on a drug

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30
Q

ADME

A

absorption, distribution, metabolism, excretion

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31
Q

oral admin- considerations in GI tract

A

gastric ph and contents. surface area. blood flow. GI mobility. complete GI tract. flora

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32
Q

gastric ph and contents affects what?

A

absorption of certain meds like ca supplements

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33
Q

what limits transport into placental transfer

A

p-glycoproteins

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34
Q

placental transfer -describe fetal plasma

A

acidic, ion trapping of basic drugs

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35
Q

blood brain barrier is made up of

A

very tight junctions

36
Q

to cross BBB, meds need to be highly

A

lipophilic

37
Q

CNS inflammation (meningitis) does what to BBB

A

increases the space between the junctions (look this up more)

38
Q

hydrophillic

A

water loving water is an ionized. meds need a transport molecule or carrier protein

39
Q

membrane permeability

A

in order to enter an organ, a drug must permeate all membranes that separate the organ from the site of drug administration

40
Q

tissue binding

A

where is the drug most likely to be used

41
Q

what meds live in the bones

A

tetracyclines

42
Q

the less albumin you have

A

the more unbound medication, and greater risk of toxicity

43
Q

what do basic drugs bind to

A

Alpha 1 acidic glycoprotein

44
Q

what do acidic drugs bind to

A

albumin

45
Q

why are free levels drawn

A

want to know how much of the med is actually active

46
Q

protein binding affects

A

the amount of free drug that can actually effect the body

47
Q

two compartment model

A
  • redistribution before elimination
  • slow rate of administration for secondary re-distribution
  • target organ may be in the initial or secondary “compartment”
48
Q

does passive diffusion require energy

A

no

49
Q

does passive diffusion require a carrier

A

no

50
Q

what molecules use passive diffusion

A

rapid for lipophilic, non-ionic, small molecules

51
Q

does facilitated diffusion require energy

A

no

52
Q

does facilitated diffusion require a carrier

A

yes

53
Q

what is facilitated diffusion

A

drugs bind to carrier by noncovalent mechanisms.

chemically similar drugs compete for carrier

54
Q

do aqueous channels require energy

A

no

55
Q

do aqueous channels require a carrier

A

no

56
Q

how do aqueous channels work

A

small hydrophilic drugs diffuse along concentration gradient by passing thru aqueous channels/pores. electrolytes love these

57
Q

does active transport require energy

A

yes

58
Q

does active transport require a carrier

A

yes

59
Q

how does active transport work

A

identical to facilitated diffusion except that ATP powers drug transport against concentration gradient

60
Q

metabolism

A

breakdown for ease of elimination

61
Q

prodrug

A

an inactive substance that is converted to a drug within the body by the action of enzymes or other chemicals.

62
Q

phase 1 metabolism

A
  • induce or expose a functional group on the parent compound.
  • generally lose activity, rare instances of preserved.
63
Q

phase 1 metabolism - how are they eliminated

A

often hydrolyzed or ester linked for rapid elimination thru kidneys

64
Q

phase 2 metabolism

A

conjugation reactions… links parent compound or phase 1 metabolite with a functional group via covalent linkage.

65
Q

most enzymes that break down medications come from

A

liver

66
Q

cyp450

A

terminal oxidase in a multicomponent electron transfer chain.
phase 1 type reactions.

“most common enzymes that break down meds into something more ionized, polar water loving, so that they get eliminated”

67
Q

CYP3A4

A

isoform. responsible for the metabolism of more than 50% of all medications. found in liver and small intestine

68
Q

med metabolized by a CYP is a

A

substrate

69
Q

inhibition of enzyme

A

-Will keep the enzyme from
working properly
-Ability to increase amount of parent compound

70
Q

induction of enzyme

A
  • will enhance the capability of the enzyme
  • Ability to quickly metabolize the parent compound
    so you need more!
71
Q

factors affecting metabolism

A

genetics, environment, diet, disease factors, age, sex

72
Q

hydrolysis

A

often provide a site for conjugation, or may inactivate P450 metabolites for excretion. “a chemical process of decomposition involving the splitting of a bond and the addition of the hydrogen cation and the hydroxide anion of water.”

73
Q

conjugation

A

Phase I metabolite joining to another compound.

74
Q

elimination is easier when a med is

A

polar, hydrophillic

75
Q

3 processes of renal elimination

A

glomerular filtration, active tubular secretion, passive tubular reabsorption

76
Q

glomerular filtration is for

A

unbound medications

77
Q

active tubular secretion is for

A

p-gp and other transport proteins

78
Q

passive tubular reabsorption is for

A

weak acids and bases via concentration gradients

79
Q

first order kinetics

A

A constant fraction of the drug in the body is eliminated per unit time. so length of half life is constant.

80
Q

zero order kinetics

A

half life decreases with decreasing concentration.

81
Q

elimination rate (k)

A

fraction or % of the total amount of drug in the body removed per unit of time.

82
Q

formula: k= Cl/V

A

elimination rate = clearance / volume

83
Q

formula: k = ln (C1-C2) / time

A

elimination rate = natural log times the change in concentration divided by time.

84
Q

how many half lives do you need to get to steady state

A

5

85
Q

what do half lifes and elimination rates do

A
  • estimate the time to steady state
  • estimate the time to eliminate the med from the body
  • predict non-steady state plasma levels
  • predict steady state from a non-steady state level
  • determine dosing intervals

pharm1 S.Horvath (18 decks)

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