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Foundations 5 > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

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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
Sublingual or buccal
Rapid absorption | Avoid first pass
26
Rectal
Useful when can't cooperate | Reduced first pass effect
27
First pass effect
Seen when rapidly metabolized drugs are absorbed by stomach or duodenum...drug goes straight to portal circulation to liver Decrease in bioavailability
28
How to measure bioavailability
Meausre plasma drug conc Inject IV of same drug in separate exp Integrate plasma drug concentration from steps 1 and 2
29
Controlled release
Slower absorption phase means smaller peak and allows less frequent dosing
30
Albumin
Binds weak acids and is most abundant and important
31
alpha 1 acid glycoprotein
Binds basic (+ charged) drugs
32
Lipoproteins
Bind lipophilic drugs
33
If concentration of albumin decreases
Then there will be more unbound weak acids to have effect
34
Most clinical tests measure
Total concentration
35
Pharmaco effect determined by
Free drug concentation
36
When drug is protein bound,
It cannot be eliminated by kidney or liver...also cannot have its effect...basically acts as a buffer
37
Volume of distribution equation
Co=X/Vd Co = plasma drug concent at T0 X = amount of drug in body Vd = volume of distribution
38
Larger Vd means
Need higher dose to achieve the same effect
39
Vd of Lipophilic vs hydrophilic
Hydrophilic will have smaller Vd because it will stay in the plasma while lipophilic prefers fat
40
Instantaneous absorp
IV bolus
41
Zero order absorption
Constant rate | IV drip or controlled release
42
First order of absorption
Rate varies in proportion to drug concentration at absorption site Most other routes of admin
43
Liver and kidney role in elimination
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
Steps in the kidney
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
Kidney becomes more important with
Smaller drugs
46
Biliary excretion is main elimination for
Large hydrophilic drugs
47
Biliary excretion process
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
Enterohepatic recirculation
Something glucuronated and sent into the bile...intestinal bacteria cleave the glucuronide...more lipophilic molecule reabsorbed into the blood
49
Zero order elimination
Constant rate
50
First order elimination
Variable rate proportional to plasma concentration
51
Most drugs eliminated by
First order process
52
Zero order elimination occurs when
Drug eliminated at its Vmax
53
Drug clearance
Describes rate of first order elimination from body but can also be used to describe clearance from an organ
54
How to measure drug clearance
Sample blood from portal and hepatic veins Measure blood flow into liver Calculate organ clearance
55
Interprettion of clearance
2mL/min means liver is eliminating every minute that same amount you would find in 2mL of blood
56
Single compartment model useful when
Additional compartments are small or unimportant
57
2 compartment model
Central and peripheral compartments Central compartment includes the plasma...absorption and elimination only occur with this compartment which carries to liver and kidneys
58
How to recognize 2 compartment model
Injected and undergoes distribution so plasma concentration drops rapidly...then, equilibrium attained and curve will flatten out as elimination process dominates
59
IV infusion order
Zero order
60
Oral administation order
first order
61
Intermittent administration order
Instantaneous if IV | First order if oral
62
IV infusion
Exponential rise to Css Time to Css determined by T1/2 After one T1/2, it will be at 50% of Css
63
Css equation
Css=infusion rate/CI Cs = plasma drug concentration Infusion rate = units of amount/time Cltotal = Total drug clearance
64
If drug has long T1/2
use a loading does to get up to Css Use C=X/Vd to get htis
65
Single dose oral admin
Rising and falling phases Aborption dominantes rising while elimination dominates falling phase IM injection will follow same thing as will any 1st order
66
Variables that increase drug conc
Dose, absorp rate, and elimin rate
67
If you increase dose
Peak concentration higher but takes place at same time | AUC increases
68
If absorption slows (use a different route)
Peak concentration is lower and delayed | No change in AUC
69
If elimination slows (renal failure)
Peak concentration is higher and delayed | AUC increases
70
intermittent IV injections
Sawtooth pattern iwht peaks and troughs Peaks and troughs undergo exponential rise to maximumu values
71
Intermittent Oral or IM injections
Css after about 4 halftimes Time to plateau independent of dosage Rounded sawteeth T1/2 determines how long it takes to reach maximum
72
Non-linear kinetics
Drug concentration and AUC can change drastically with dose...increasing dose can produce unexpectedly large and toxic increases in concentration
73
Elimination saturation
Blood levels higher than expected with high doses
74
Oral absorption saturation
Blood levels are lower than expected with high doses
75
Example of non-linear pharmacokinetics
Zero-order elimination
76
Therapeutic window
Less than toxic but greater than minimum | Sample right after the peak effect
77
When is therapeutic monitoring helpful?
Narrow window, Effect can't be observed, complex kinetics | Cmeasured/Cdesired=original dose/adjusted dose
78
Why does T1/2 determine time course of IV infusion
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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