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Three factors that affect systemic drug absorption from extravascular sites

properties of the drug, dosage form used and anatomy and physiology of absorption site

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what affects the rate and extent of drug absorption

surface area,stomach emptying rate, GI mobility and blood flow.

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peak concentration is where rate of absorption is (greater, less, or equal to) reate of elimation

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post abosorption phase is where rate of absorption (<,>,=) rate of elimination

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absorption phase is where rate of absorption (<,>,=) rate of elimination

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Elimination phase is where rate of absorption is

0 and the formula is dDb/dt = -kDb

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Ka and K make it possible to determine peak and trough plasma concentration during multiple dosing

true but says they are not reliable??? (they are direct measures)

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indirect measure of plasma concentration during multiple dosing are___ because Ka and K directly afftect them

Cmax, tmax, and AUC

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if you increase Ka while leaving K the same what happens to Cmax tmax and AUC

Cmax will increase, tmax decrease, while AUC says the same

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if K increase and Ka says the same what happens to Cmax Tmax and AUC

Cmax, Tmax and AUC decrease

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saturable and controlled release system are what kind of processes

zero order

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where is the change of drug in the body = to zero

at tmax or Cmax

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tmax is dependent on

Ka and K

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wagner-nelson method assuces a ___compartment model

one compartment model

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amount of drug absorbed is equal to what

drug in body and plus what was excreted

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by the wagner-nelson method you can determin absorption rate constant ka by the plot of ___versus time

1-Ab/Ab* *infinity faction of unabsorbed drug is = 1-Ab/Ab *

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drug in the GI tract Dgi is equal to

Do*e^(-ka*t)

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Loo-Riegelman method assumes a __comparment model

two-compartment

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when using the feathering technique is Ka (<,> ) k

ka is > than K and Ka represents the steeeper slope

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when K> Ka this is usually because what (when do they flip flop

when you have very fast elimination or extended release products

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when drugs have (high or low) value for k (short t) the ther are probably not suitable for oral administration

High value of k not sutiable

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what factors can/will creat a delay in absorption (LAG TIME)

stomach emptying and intestinal motility

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what represent the time needed to for drug levels to attain the minimun effective concentration

onset time

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absorption begins at the end of lag time and is represented by To; ____

onset time

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at steady state the plasma drug levels fluctuate betwen what and what

Cmin to Cmax

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what is the principle of superposition assume

that early does of drug DO NOT affect the pharmacokinetics of subsequent doses

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what does the superposition allow one to do

project the plasma drug concentration-time curve of a drug after multiple consecutive doses

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(statement) if a constant does is given at constant time periods, the plasma concentraiton of each dose will consist of the same datat obtained after the single dose. what about after unequal dosage intervals

THE PREDICTION STILL HOLDS TRUE FOR UNEQUAL BUT DON'T UNDERSTAND HOW YET

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cmax is important in determining

drug stafety

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cmax should always remina below the

minimum toxi concentration

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what is good indication of drug accumulation

cmax

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if cmax of infinity is equal to cmax of dose one what does this mean

that no accumulation is taking place

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if cmax is much larger than the cmax of dose 1, what does this mean

significant accumulation druing the multiple-dose regimen

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drug accumulation is affected by what and not affected by what

is affected by the elimination half-life (elmination constant) and the dosing interval. it is independent of the dose

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the TIME to reach steady state after multiple oral doses is dependent on__ and independent of __

dependent on elimination half and independent of the size of dose, the length of teh dosing interval, and number of doses

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if you changed +or - the dose or dosage interval of the drug, the TIME required to reach steady state is (same or altered)

same they are indenpended of the TIME but remember the plasma leave changes proportionately

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if the drug is given at the same dosing rate but as an infusion, the average plasma drug concentration will be _____

the same (cmax and cmin will flucuate)

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you can find average steady state plasma drug concentration by dividing the area under the cruve for a dosing period by

dividing AUC by dosing interval tau

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the time to reach one half steady state plasma levels or the accumulation half-life

= to t1/2(1+ 3.3log (ka/ka-k)

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when a drug is administered intravenously the accumulation t1/2 =

the elimination t1/2

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the time to reach 1/2 steady state concentration is dependent on the

elimination t 1/2 life and independent of dose or doseage interval

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accumulation t1/2 is directly proportional to

the elimination t1/2

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if you give the same dose to patients but change the dosage interval to shorter , then you do what to cmax infinity and # of does to reach steady state

cmax concentration is higher, average steady state is the same and # of does to reach ready steady state increase. see page 190 8.3

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in what situations would superposition not be valid

when drugs do not follow linear kinetics, saturation of carrier system, enzyme induction, enzyme inhibition, patients disease condition changes b/w doses

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why would one want to use multiple dosing to get drug accumulation?

to keep plasma drug levels within the therapeutic window

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how would one keep the plasma drug levels within the therapeutic window? What do you have to adjust

you adjust the time between doses, tau, and you can adjust the dose

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when will accumulation not occur

if a second dose is given at an interval longer than that required for the elimination of the previous dose OR if at steady state Cmax infinity is the same as cmax of dose 1

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when steady state is achieved through accumulation what happens to cmin and cmax or infinity

they remain the same

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for drug safety cmax should always be less than what

minimum toxic dose

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the number of doses needed to reach steady stae is dependent on

t1/2 and tau

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the drug accumulation index is represented by

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the relationship between loading dose and accumulation index is what

the loading does is the product of the maintenance dose and the accumulation index.DL= DM*R. where maintenance dose is equal to loading dose (DL)- amount of drug remaining at the end of dosing interval{which is=(e^-k(tau)}

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the fraction of the dose remainin in the body is

F=Db/Do=e^(-k*tau)

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the fraction of drug remaining in the body depends on

k and tau

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if the f (fraction of drug) is large then what does this mean about tau

tau is small. because if alot of dose remains this mean elimination hasn't had time to occur Much so the next does is given soon (so interval is small)

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