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Foundations 1 > Week 4 Pharmacokinetics > Flashcards

Week 4 Pharmacokinetics Flashcards

1
Q

what are the fundamental questions regarding medication? 3

A

how to deliver, what concentration, how long should the medication be taken for

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2
Q

what are the benefits (2) and drawbacks (1) of topical medication admin

A

Topical: + immediately effective, long lasting, - most most drug action sites are internal

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3
Q

define pharmacokinetics

A

what the body does to the drug

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4
Q

what are the four factors affecitng pharmacokinetics

A

ADME. Absorption, Distribution, Metabolism, excretion

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5
Q

what are seven common routes of drug admin?

A
  1. oral 2. IV 3. Topical 4. rectal 5. injection 6. inhaled 7. sublingual
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6
Q

what is the first-pass effect

A

drugs that are absorbed through the GI tract must first pass through liver before going to systemic circulation. the liver detoxifies some of the drug and concentration decreases

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7
Q

what are four ways in which oral drugs are lost?

A
  1. stool 2. detoxed by liver 3. binds plasma proteins/ends up in adipose (free drug=active drug) 4. excreted
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8
Q

what does MEC stand for? what are the two types associated with drugs?

A

minimum effective concentration. MEC for desired response. MEC for adverse response.

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9
Q

what is the therapeutic window of a drug?

A

between MEC for desired response and MEC for adverse response

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10
Q

most drugs are absorbed actively/passively due to their _____/____ nature. this type of absorption is/ is not saturable and therefore displays ___ order kinetics

A

passively hydrophobic/uncharged (easily pass through membrane) not saturable first order kinetics

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11
Q

the pKa for a weak acid is…

A
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12
Q

the pKa for a weak base is

A

>7

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13
Q

most drugs are what type of acid or base?

A

weak acid or base

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14
Q

what form of WA/WB are readily absorbed

A

uncharged form

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15
Q

when decreasing pH what form does WA/WB take

A

WA: HA (uncharged) WB: HB+ (charged)

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16
Q

when increasing pH what form does WA/WB take

A

WA: A- (charged) WB: B (uncharged)

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17
Q

Aspirin is a weak acid drug, will increasing intestine pH increase aspirin absorption?

A

decrease absorption HA+H20==>A- + H3O+ (more of the deportonated charged form)

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18
Q

what is bioavailability?

A

the amount of an oral drug that actually reaches systemic circulation and can be used by the body

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19
Q

if given a graph of [plasma drug] vs time of an injected drug and orall drug, how can you calculate the bioavailability

A

BA: Area under curve oral/AUC injected X100

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20
Q

what factors limit the bioavailability of a drug? 5

A

some drugs are degraded in acid of stomach, some drugs are not efficiently absorbed in GI tract, micororganisms in GIT metabolize drugs, first pass effect

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21
Q

what factors impact the distribution of drugs in the body? 4

A

blood flow, capillary permabeability, binding of drugs to plasma proteins/tissues, hyrdrophobic/hydrophilic drugs

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22
Q

how does blood flow impact drug distribution?

A

some organs receive more blood flow (brain, liver, kidney>muscle, skin, fat) and therefore more exposure to drugs in circulation

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23
Q

how does capillary permeability impact drug distribution?

A

some capillaries are less permeable. brain capilllaries less permeable than liver capillaries

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24
Q

what is a drug resevoir?

A

drugs bind plasma proteins and in tissues, these drugs are not active. when the free drug concentration decreases, these drugs will be released.

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25
Q

what are the two “compartments” of the body/

A

central compartment (circulation), peripheral compartment (body tissues)

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26
Q

what is the alpha phase?

A

an initial rapid decline in [plasma drug] that is a result of body tissues binding/sequestering drug. eventually an equilibrium is obtained

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27
Q

what is the beta phase?

A

decrease in drug concentration due to removal from the body (metabolism/excretion)

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28
Q

what is the volume of distribution?

A

how much drug needs to be put in the body to get a certain [plasma drug].

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29
Q

what is the eqn for Vd

A

Vd=amount of drug in the body (amount given, mg)/drug concentration in plasma (mg/L)

30
Q

a 70 kg man has how many liters of plasma? liters of blood?

A

3 L of plasma, 5.5 L of blood

31
Q

drug metabolism GENERALLY activates/inactivates a drug

A

generally inactivates

32
Q

the enzymatic modifications of drugs typically make the drug more…

A

hydrophilic/polar so they can be excreted

33
Q

what is a prodrug?

A

a drug that is inactive but activated by metabolism

34
Q

where does drug metabolism mainly occur?

A

liver

35
Q

what are the two phases associated with drug metabolism?

A

Phase I, phase II

36
Q

what is a phase I reaction? main enzyme?

A

oxidation, hydrolysis, hydroxylation, dealklylation, deamination. CYTOCHROME P450s (odxidation, reduction, hydrolysis)

37
Q

what is a phase II reaction?

A

addition of a large substituent group (glucuronyl, sulfate, acetyl) that makes the compound more POLAR

38
Q

Cytochrome P450s: location, role, typical structural feature of substrates

A

most important enzyme for drug metabolism, over 57 P450s in human genome. located in membrane of ER (mainly in liver), high lipid solubility is a common structural feature

39
Q

general rxn that CYP (cyt P450 catalyze)

A

NADPH+ H+ +R +O2==>NADP+ + H2O + RO

40
Q

microsomal (ER) enzymes can be activated by… (3 examples)

A

repeated exposure to some drugs: ethanol, phenobarbital, carcinogenic cmpds

41
Q

microsomal enzymes can be inhibited by….(3)

A

decrease activity of CYP. Imdazole containing drugs, some antibiotics, grape fruit juice

42
Q

how many Cytochrome P450s account for 95% of drug metabolism? which is the biggest contributor

A

6 Cyt P450 enzymes. CYP3A4

43
Q

what is the M-M eqn?

A

v=(Vmax[C])/(Km+[C]), [C] is drug concentration

44
Q

when [C]>>>>Km, what does the M-M eqn look like? what order kinetics?

A

v=(Vmax[C]^0); zero order reaction. V is independent of [drug]; saturated (drugs that need a transport protein)

45
Q

when [C]

A

v=(Vmax[C])/(Km); first order reaction. V is dependent on drug concentration; non-saturated (passive diffusion of drugs)

46
Q

most drug elimination resembles which order kinetics?

A

first order, the rate (-dC/dt) of disappearance is dependent on the concentration of the drug

47
Q

what is the integrated rate law for 0 order reactions?

A

[C(subt)]=-kt+ [C(sub0)]

48
Q

what is the integrated rate law for a 1 order reaction?

A

ln[C(subt)]=ln[C(sub0)]-kt

49
Q

the rate of disappearance for a drug having zero order kinetics is…

A

-dC/dt=k; elimination has become saturated

50
Q

the rate of disappearance for a drug having first order kinetics is….

A

-dC/dt=K[C]; elimination is not saturated

51
Q

what is half-life of eliminaiton?

A

the amount of time required for the concentration of drug in the blood to decrease by 1/2

52
Q

what is t(1/2) for a first order reaction

A

=.693/k

53
Q

what is t(1/2) for a zero order reaction?

A

=[C(sub)]/(k*2)

54
Q

what is clearance?

A

CL; the volume of plasma cleared of the drug per unit time (L/hr)

55
Q

does clearance for most drugs depend on concentration of the drug?

A

YES! most drugs depict a first order elimination. -dC/dt=kC

56
Q

what equation related CL and Vd?

A

k=CL/Vd

57
Q

what equation relates half life (first order), Vd, and CL?

A

t(1/2)=(.693(Vd))/CL

58
Q

a pt took 10 mg IV injection of a drug and the plasma drug concentration was 1 mg/mL. 10 hrs later the drug concentration was .25 mg/L. what is CL

A

1.4 L/hr

59
Q

what is the (Css) steady state concentration of a drug?

A

seen during drug accumulation (repeated dose of a drug, contstant rate IV), this is when the rate of infusion=rate of elimination (first order reaction, the concentration of the drug gets high enough where its eliminanation matches its accumulation)

60
Q

If rate of infusion (IV infusion) increases then what happens to Css

A

Css increases (directly proportional, double rate=double Css)

61
Q

if the clearance of a drug increases (is doubled) what happens to Css?

A

Css halves (inversely proportional)

62
Q

when do we see CL decrease?

A

liver or kidney disease

63
Q

what is clearance?

A

how fast the drug is eliminated from the body

64
Q

what determines the time to reach the steady state? exception?

A

changed only by factors that change t(1/2). only factors that alter elimination (increase metabolism of a drug or increase clearance will both decrease the amount of time to reach Css). Exception is a loading does that will attain Css faster due to a higher initial dose

65
Q

a pt takes a drug with regular repeated oral doses. which may result in shorterr time required to reach Css? 1. shorten the dose interval by 50% 2. increase drug dose by 2x 3. take a drug that induces the P450 enzyme 4.take a drug that inhibits P450

A
  1. inducing P450 will increase the CL and the Css will be reached faster
66
Q

changing the rate of infusion of a drug changes the final Css/time to Css, but does not alter the final Css/ time to Css

A

changes the final Css does not change time to Css

67
Q

relate Css value and frequency of dose (oral) and interval of dose

A

Css=frequency/interval of dose as frequency increases, Css increases as interval increases, Css decreases

68
Q

relate Css value and dose of a drug

A

Css is directly proportional to dose. increase dose, increase Css (the time to Css does not change!!)

69
Q

if a drug is not metbaolized by the liver very well, what is a possible side effect?

A

the drug accumulates in the body

70
Q

rate of elimination=

A

CL x [C]

71
Q

Label:

onset of effect, topical admin, oral admin, duration of action, peak effect, intensity, MEC for advers, MEC for desired, therapeutic window

A

Foundations 1 (65 decks)

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