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Pharmacology 1 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

pharmacokinetics

A

what the body does to the drug, dose-concentration relationship

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2
Q

pharmacodynamics

A

what the drug does to the body, concentration- effect relationship

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3
Q

4 pieces of pharmacokinetics

A

absorption, distribution, metabolism, excretion

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4
Q

why is understanding PK important

A

control therapeutic action of the drug, gives us information about dosage form, route of administration, dose, onset of action, efficacy, side effects, dosing interval

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5
Q

steps in PK

A

dose of drug administered –> drug conc in circulation –> distribution or elimination –> dose concentration at site of action –> pharmacodynamics

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6
Q

AUC

A

area under the curve, total drug absorption over time; increases as drug begins absorbing, decreases when excretion > absorption

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7
Q

Cmax

A

maximum concentration of drug in the blood, peak on the AUC curve, must be in therapeutic range between MTC (max toxicity conc) and MEC (min effective conc)

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8
Q

Vd

A

volume of distribution, Vd= total amount of drug (dose)/conc of drug in plasma; more in blood –> lower Vd

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9
Q

Cl

A

clearance

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10
Q

t1/2

A

elimination half life

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11
Q

Css

A

steady state concentration

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12
Q

factors that affect a drugs movement and availability at sites of action

A

molecular size and structure, degree of ionization, lipid solubility, protein binding

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13
Q

how polarity affects permeability

A

more polar drugs are hydrophilic, harder to get through the membrane

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14
Q

changes in ___ leads to changes of a drug from nonpolar polar

A

pH

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15
Q

absorption

A

transfer of a drug from its site of administration to the bloodstream

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16
Q

oral drugs must ___ to be absorbed

A

dissolve

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17
Q

most drugs dissolve in the ___ and are absorbed in the ___

A

stomach; Small intestines

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18
Q

enteric coated (EC) drugs

A

delayed release drugs, dissolve in small intestines

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19
Q

purpose of enteric coated (EC) drugs

A

to protect the stomach from the drug, to protect the drug from the stomach, to release the drug after the stomach

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20
Q

similarity between delayed release drugs and extended release drugs

A

cannot be chewed, crushed, or dissolved since it will destroy the mechanisms of action; could lead to potential overdose in ER drugs

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21
Q

differences between delayed release and extended release drugs

A

DR: released in small intestines all at once, ER: released immediately in small doses over the course of the day

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22
Q

most drugs are absorbed via ___ transport in the ___

A

passive; small intestines

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23
Q

passive transport of drugs from the instestines

A

go from high conc in the gut to low conc in the plasma (blood), microvilli provide large SA for absorption into bloodstream

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24
Q

factors related to the drug that affect rate and extent of absorption

A

molecular weight, lipid/water solubility, degree of ionization, dosage form, concentration, particle size in tablets

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25
Q

factors related to the body that affect rate and extent of absorption

A

gastric mobility, intestinal transit time (slow passage –> greater absorption), pH, blood flow to absorption site, SA, food

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26
Q

when to take drugs with food

A

required for absorption (ie high fat), protect stomach, prevent nausea/vomiting, for efficacy

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27
Q

when to take drugs without food

A

required for absorption –> cations (Ca, Fe, Mg, Zn) in food can bind drug and prevent absorption; take 1 hr before or 2-3 after meal

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28
Q

p-glycoprotein

A

efflux pump that pumps drug back into GI lumen, decreases absorption of drug into blood

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29
Q

CYP3A4

A

enzyme that breaks down drug in enterocytes of the SIs, decreased drug absorption

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30
Q

first pass effect

A

first pass metabolism, happens in gut wall enzymes and hepatic enzymes, typical with oral medications, reduces bioavailability; dose gets decreased as is passed through enzymes of the intestines and again in the liver

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31
Q

bioavailability (F)

A

fraction of drug absorbed into systemic circulation after administration

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32
Q

absorption of oral drugs

A

first pass effect may be significant

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33
Q

absorption of sublingual drugs

A

bypasses first pass effect, rapid absorption into oral capillaries

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34
Q

absorption of transdermal drugs

A

bypasses first pass effect, usually slow absorption

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35
Q

absorption of rectal drugs

A

less first pass effect than oral

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36
Q

intravenous drug absorption

A

F=100%, most rapid onset

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37
Q

intramuscular drug absorption

A

depends on injection site and blood flow

38
Q

subcutaneous drug absorption

A

constant, slow absorption

39
Q

brand name vs generic drugs

A

generic companies need to prove bioequvalence, inactive ingredients may be different; generic must have same active ingredients, strength, dosage form, route of administration

40
Q

bioequivalence

A

generic drug has same rate and extent of absorption of a drug

41
Q

distribution

A

reversible transfer of a drug between compartments, plasma interstitial fluid intracellular fluid

42
Q

compartments

A

defined volume of body fluids

43
Q

distribution depends on:

A

molecular size and polarity/lipophilicity of drug

44
Q

where large drug molecules distribute

A

confined to circulation

45
Q

where polar drugs distribute

A

excluded by cell membrane from entering intracellular or fatty tissues

46
Q

where lipophilic drugs distribute

A

in fatty tissues, little in bloodstream

47
Q

factors that affect drug distribution

A

protein binding, blood brain barrier, storage in tissues

48
Q

protein binding and drug distribution

A

protein bound portion is not available for action, too big to move out of the blood into the tissues, plasma proteins can act as a transporter of the drug through the blood stream

49
Q

drug competition for plasma proteins

A

if drug 2 significantly displaced drug 1, drug 1’s free concentration increases possibly to a toxic level

50
Q

free drug

A

drug concentration that is free floating in the blood, not bound to proteins

51
Q

blood brain barrier effect on drugs

A

prevents distribution of drugs to the brain, tight junctions block many substances, must be small and lipophilic to get through the barrier

52
Q

places where drugs can get stored, how this affects distribution

A

lipophilic drugs can stay in adipose tissue and wont readily pass back into the blood –> makes treating obese patients difficult, developing teeth or bones can be a storage site for some antibiotics in children <8yo

53
Q

metabolism

A

biotransformation, chemical alteration of the drug in the body

54
Q

goal of metabolism

A

to make the drug easier to excrete

55
Q

where most drug metabolism occurs

A

liver

56
Q

typical pathway of lipophilic drug metabolism

A

acted on by an enzyme in the liver to become more hydrophilic, sent to the kidneys where it can more easily be excreted

57
Q

2 phases of metabolism

A

drug –> phase 1 –> active/inactive metabolites –> phase 2–> conjugation products (inactive), do not need both phases for every drug

58
Q

phase 1 of metabolism

A

oxidation, reduction, hydrolysis; involves CYPP450 enzymes

59
Q

prodrug

A

requires biotransformation to become active metabolite, usually CYP450 enzymes

60
Q

inhibitors of CYP450

A

block metabolic activity of CYP enzymes, occurs quickly

61
Q

inducers of CYP450

A

increase CYP activity by increasing enzyme synthesis, slow process

62
Q

substrate

A

drug that is metabolized

63
Q

why there is a potential for drug-drug interactions with inducers/inhibitors

A

one drug may inhibit/induce the metabolism of another which could lead to a potential dose adjustment

64
Q 
potential clinical impact for an inhibitor drug on CYP450
Drug X (Active)-->Cyp450--> metabolite X (inactive)
A

Drug X concentrations will increase, could lead to possible toxicity (supratherapeutic), would need to decrease the dose of X

65
Q 
possible clinical impact for an inducer drug on CYP450
Drug X (active) --> CYP450 --> metabolite X (inactive)
A

decreased efficacy, levels of X would be lower, increasing the dose wouldnt always be effective since inducer is signalling CYP450 to continue production of more enzymes

66
Q

importance of knowing OTC medications

A

OTC drugs and herbal products may cause drug drug interactions, can affect CYP450 effects

67
Q

phase 2 of metabolism

A

conjugation, addition of a polar molecule

68
Q

purpose of phase 2 of metabolism

A

add a polar molecule to large compounds that cannot easily move throughout the body so they become polar, easier to be excreted

69
Q

factors that affect rate and extent of metabolism

A

drug drug interactions, drug food interactions, disease, age, environment, genetics

70
Q

excretion

A

removal of the drug and its metabolites from the body, mainly in the kidneys

71
Q

processes of the kidneys that allow excretion

A

glomerular filtration, reabsorption, secretion, excretion

72
Q

glomerular filtration of a drug

A

depends on plasma protein binding and renal blood flow, capillaries have pores to allow passage into urine, if it is attached to blood proteins it will be too large to pass through the pores, more blood flow –> more filtration

73
Q

clearance

A

the volume of plasma that is cleared of a drug per unit time

74
Q

glomerular filtration rate

A

measure of clearance through the kidneys, used to make clinical decisions regarding drug dose and choice

75
Q

renal dosing

A

drug dose or interval adjustment for decreased kidney function, GFR declines with age and in kidney disease

76
Q

GFR is estimated using ___

A

creatinine clearance

77
Q

CrCl equation

A

((140-age) x kg)/ (serum creatinine x 72) x .85 for females

78
Q

normal adult GFR

A

120 mL/min

79
Q

tubular resorption of drugs

A

depends on drugs lipid solubility and pH, drug moves from urine tubule back into the blood, easier for lipophilic drugs, hydrophilic drugs continue to be excreted in urine

80
Q

weak acid drugs are excreted faster in ___ urine

A

alkaline, more RCOO- + H+ –> more ionized and hydrophilic –> readily excreted

81
Q

weak base drugs are excreted faster in ___ urine

A

acidic, more RNH3+ –> more ionized and hydrophilic –> readily excreted

82
Q

secretion

A

drug crosses back into urine and is excreted

83
Q

excretion = ___ - ___ + ___

A

filtration - reabsorption + secretion

84
Q

elimination half life

A

time required for the plasma concentration of drug to decrease by 50%

85
Q

when T1/2 is useful

A

when determining dosing interval

86
Q

how poor kidney function affects t1/2

A

poor kidney function –> takes long time to decrease drug levels –> increased half life

87
Q

steady state plasma concentration (Css)

A

reached when level being absorbed into the blood = level being excreted, take 4-5 half lives to reach

88
Q

loading dose

A

give high dose to reach Css faster, lower the dose after to maintain concentration

89
Q

therapeutic drug monitoring

A

aims to optimize drug treatment by maintaining plasma drug concentration within therapeutic range

90
Q

steps of therapeutic drug monitoring

A

draw blood –> send to lab –> find blood concentration –> find a dose that is in therapeutic range

91
Q

when therapeutic drug monitoring is used

A

for drugs with narrow therapeutic range

Pharmacology 1 (4 decks)

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