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Foundations 5 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Acronym for kinetics

A

Absorption - any process by which drug first enters blood
Distribution - how it moves between compartments
Elimination - any process by which drug leaves the body

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2
Q

Passive transport

A

Drug diffuses across membrane with gradients

Often lipophilic or gas

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3
Q

Active transport

A

Protein transports against gradient using ATP

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4
Q

Facilitated fissuion

A

Protein transports across but only in favor of gradient

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5
Q

Receptor-mediated endocytosis

A

Drug and receptor enter cell by endocytosis of a clathrin coated protein

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6
Q

All capillary beds are

A

Highly permeable to lipid souble drugs

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7
Q

Most capillary beds

A

Water soluble move through fenestrations and lipid solbule diffuse through membrane

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8
Q

Capillary beds in CNS and other tissues

A

Few fenestrations and lipid soluble drugs and gasses move through

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9
Q

Paracellular movement

A

Movement between fenestrations

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10
Q

High drug permeability

A

Liver and kidney

Major drug elimination organs

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11
Q

Average drug permeability

A

Placenta - assume all drugs taken will get to fetus

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12
Q

Low drug permeabiloty

A

CNS - complicates development of these drugs…prostate is also

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13
Q

Blood brain barrier

A

tight junctions between endothelial cells AND P-glycoprotein actively transport drugs out of the CNS

Gases and lipid soluble can get in, but few water soluble

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14
Q

pH effects

A

Weak base more effective at BBB at a higher pH because it will be neutral

Opposite for bases

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15
Q

MDR - where, what does it move

A 
MDR1 (P-glycoprotein) 
Most important transporter 
Found in intestine, liver, kidney, and CNS 
Active transporter 
Moves organic cations and neutral drugs
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16
Q

Tubules of nephron transport

A

Contain OATs (- organic trasnporters) that transport out of blood and into the cell…then move by transporting across brush border and into the lumen

Can move drugs out of or into the lumen

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17
Q

Enteral

A

GI tract (duodenum or stomach)

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18
Q

Parenteral

A

All other sites

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19
Q

Inhalation

A

Used for local admin or systemic

Smaller aerosolized particles penetrate depper into the lungs

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20
Q

Transdermal

A

Only limited number

Must be potent, lipid solbule, and low molecular weight

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21
Q

IV

A

Fastest and most accurate
Immedaite peak
Preferred for hard to absorb or easy to degrade

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22
Q

IM

A

Better tolerated, but slower absorption than IV
Good for long-lasting depot for lipophilic drugs
Must diffuse across cap bed

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23
Q

Subq

A

Easier to administer, more variable and slower absorption

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24
Q

Oral

A

Most convenient but most variable

Subject to 1st pass effect

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25
Q

Sublingual or buccal

A

Rapid absorption

Avoid first pass

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26
Q

Rectal

A

Useful when can’t cooperate

Reduced first pass effect

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27
Q

First pass effect

A

Seen when rapidly metabolized drugs are absorbed by stomach or duodenum…drug goes straight to portal circulation to liver
Decrease in bioavailability

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28
Q

How to measure bioavailability

A

Meausre plasma drug conc
Inject IV of same drug in separate exp
Integrate plasma drug concentration from steps 1 and 2

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29
Q

Controlled release

A

Slower absorption phase means smaller peak and allows less frequent dosing

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30
Q

Albumin

A

Binds weak acids and is most abundant and important

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31
Q

alpha 1 acid glycoprotein

A

Binds basic (+ charged) drugs

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32
Q

Lipoproteins

A

Bind lipophilic drugs

33
Q

If concentration of albumin decreases

A

Then there will be more unbound weak acids to have effect

34
Q

Most clinical tests measure

A

Total concentration

35
Q

Pharmaco effect determined by

A

Free drug concentation

36
Q

When drug is protein bound,

A

It cannot be eliminated by kidney or liver…also cannot have its effect…basically acts as a buffer

37
Q

Volume of distribution equation

A

Co=X/Vd
Co = plasma drug concent at T0
X = amount of drug in body
Vd = volume of distribution

38
Q

Larger Vd means

A

Need higher dose to achieve the same effect

39
Q

Vd of Lipophilic vs hydrophilic

A

Hydrophilic will have smaller Vd because it will stay in the plasma while lipophilic prefers fat

40
Q

Instantaneous absorp

A

IV bolus

41
Q

Zero order absorption

A

Constant rate

IV drip or controlled release

42
Q

First order of absorption

A

Rate varies in proportion to drug concentration at absorption site
Most other routes of admin

43
Q

Liver and kidney role in elimination

A

Only metabolites of lipophilic drugs are eliminated in urine or bile
Lipophilic drugs are not eliminated by the kidney but diuffuse across renal epithelium and back into blood

Liver must break down the lipophilic drug into something that is more hydrophilic

44
Q

Steps in the kidney

A

Passive drug diffusion into the nephron
active drug transport into the nephron
Either active transport or diffusion out of the nephron
Final elimination

Eliminates hydrophilic drugs

45
Q

Kidney becomes more important with

A

Smaller drugs

46
Q

Biliary excretion is main elimination for

A

Large hydrophilic drugs

47
Q

Biliary excretion process

A

If drug is hydrophilic, may enter bile as uncharged drug
Other drugs must be made hydrophilic via added polar side group like glucuronide

Liver has active transport proteins to pull drug into kidney

48
Q

Enterohepatic recirculation

A

Something glucuronated and sent into the bile…intestinal bacteria cleave the glucuronide…more lipophilic molecule reabsorbed into the blood

49
Q

Zero order elimination

A

Constant rate

50
Q

First order elimination

A

Variable rate proportional to plasma concentration

51
Q

Most drugs eliminated by

A

First order process

52
Q

Zero order elimination occurs when

A

Drug eliminated at its Vmax

53
Q

Drug clearance

A

Describes rate of first order elimination from body but can also be used to describe clearance from an organ

54
Q

How to measure drug clearance

A

Sample blood from portal and hepatic veins
Measure blood flow into liver
Calculate organ clearance

55
Q

Interprettion of clearance

A

2mL/min means liver is eliminating every minute that same amount you would find in 2mL of blood

56
Q

Single compartment model useful when

A

Additional compartments are small or unimportant

57
Q

2 compartment model

A

Central and peripheral compartments
Central compartment includes the plasma…absorption and elimination only occur with this compartment which carries to liver and kidneys

58
Q

How to recognize 2 compartment model

A

Injected and undergoes distribution so plasma concentration drops rapidly…then, equilibrium attained and curve will flatten out as elimination process dominates

59
Q

IV infusion order

A

Zero order

60
Q

Oral administation order

A

first order

61
Q

Intermittent administration order

A

Instantaneous if IV

First order if oral

62
Q

IV infusion

A

Exponential rise to Css
Time to Css determined by T1/2
After one T1/2, it will be at 50% of Css

63
Q

Css equation

A

Css=infusion rate/CI

Cs = plasma drug concentration
Infusion rate = units of amount/time
Cltotal = Total drug clearance

64
Q

If drug has long T1/2

A

use a loading does to get up to Css

Use C=X/Vd to get htis

65
Q

Single dose oral admin

A

Rising and falling phases
Aborption dominantes rising while elimination dominates falling phase

IM injection will follow same thing as will any 1st order

66
Q

Variables that increase drug conc

A

Dose, absorp rate, and elimin rate

67
Q

If you increase dose

A

Peak concentration higher but takes place at same time

AUC increases

68
Q

If absorption slows (use a different route)

A

Peak concentration is lower and delayed

No change in AUC

69
Q

If elimination slows (renal failure)

A

Peak concentration is higher and delayed

AUC increases

70
Q

intermittent IV injections

A

Sawtooth pattern iwht peaks and troughs

Peaks and troughs undergo exponential rise to maximumu values

71
Q

Intermittent Oral or IM injections

A

Css after about 4 halftimes
Time to plateau independent of dosage
Rounded sawteeth
T1/2 determines how long it takes to reach maximum

72
Q

Non-linear kinetics

A

Drug concentration and AUC can change drastically with dose…increasing dose can produce unexpectedly large and toxic increases in concentration

73
Q

Elimination saturation

A

Blood levels higher than expected with high doses

74
Q

Oral absorption saturation

A

Blood levels are lower than expected with high doses

75
Q

Example of non-linear pharmacokinetics

A

Zero-order elimination

76
Q

Therapeutic window

A

Less than toxic but greater than minimum

Sample right after the peak effect

77
Q

When is therapeutic monitoring helpful?

A

Narrow window, Effect can’t be observed, complex kinetics

Cmeasured/Cdesired=original dose/adjusted dose

78
Q

Why does T1/2 determine time course of IV infusion

A

Absorption constant during IV infusion…first order elimination is proportional to drug concentration and changes with it…more efficient elimination (smaller T1/2) means elimination rate will increase faster and catch up to absorption sooner

Foundations 5 (13 decks)

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