Chapter 12 ~ Extravascular Bolus Dose

Question 1

why is there a whole separate chapter for extravascular bolus dose kinetics when we just did IV

Answer 1

because all extravascular routes need to be absorbed — intravascular does not

Question 2

what is absorption rate constant

Answer 2

Ka

Question 3

true or false

intramuscular injections do not undergo absorption

Answer 3

FALSE - they do

Question 4

what is absorption

Answer 4

passage of drug from the site of administration and INTO THE PLASMA by absorbing through a membrane

Question 5

TRUE OR FALSE

the absorption of drugs generally follows 1st order drug input

Answer 5

true

Question 6

true or false

the plasma profile of EV vs IV bolus dose will be the same

Answer 6

FALSE - will not

Question 7

true or false

for extravascular routes, the entire dose is NOT absorbed all at once

Answer 7

true

Question 8

the 2 more important differences in the plasma profiles of IV vs EV:

Answer 8

-amount of drug in the plasma (Co is cmax for IV. Co is zero for EV)

-concentration of drug in plasma (conc starts declining for IV and starts increasing for EV)

Question 9

TRUE OR FALSE

the amount of drug in the plasma immediately after IV administration IS EQUAL TO the amount of dose administered

Answer 9

true

Question 10

what is the amount of drug in the plasma immediately after an EXTRAVASCULAR administration of dose? why?

Answer 10

ZERO

bc the drug has to be absorbed before it appears in the plasm

Question 11

true or false

the absorption of the entire dose of a drug is NOT an instantaneous process

Answer 11

true

Question 12

true or false

absorption most likely is an active process

Answer 12

false - passive. fick’s first law

Question 13

true or false

even though it takes more time, IV and EV have the same extent of absorption

Answer 13

false - do not

absorption of EV drug takes time –decreased rate. this results in drug loss and decreased extent of absorption

Question 14

for IV, why does the concentration immediately start declining

Answer 14

due to elimination and/or distribution

Question 15

for EV, the delay between administration and actual appearance in the plasma may range form __ to ___

Answer 15

few seconds (buccal)

to more than an hour (EC)

Question 16

most conventional EV dosage forms are designed to release their active ingredient when?

Answer 16

almost immediately after administration. there shouldn’t be a significant delay in plasma appearance

Question 17

the plasma profile for EV is a function of what 2 rate constants

Answer 17

absorption and elimination

Question 18

EV –

the first order plot of concentraiton vs time after EV bolus dose yields a _______ plot

why

Answer 18

biphasic

due to a mixture of 1st order processes — first order process of absorption and first order process of elimination (from plasma)

Question 19

what are the 3 phases on an EV biphasic plot

Answer 19

absorptive
post-absorptive
elimination

Question 20

during the predominantly absorptive phase, ______ also begins. however…..

Answer 20

elimination

but the elimination is much less predominant than the absorption

as absorption continues, elimination gets more and more predominant

Question 21

for EV plasma profile, when does the rate of drug absorption=the rate of elimination

Answer 21

when the plasma profile is at PEAK concentration

Question 22

the biphasic curve is resolved into 2 straight lines.

what do each of these 2 lines represent

Answer 22

BIPHASIC INDICATES EV

1 line is absorption and the other is elimination

Question 23

true or false

for EV, 2 straight lines indicates 1 compartment model

Answer 23

TRUE— bc have to account for absorption!!!!!!

FOR IV – JUST 1 STRAIGHT LINE MEANS 1 COMPARTMENT

Question 24

beta, the rate constant of elimination, is determined from the slope of what

Answer 24

THE TERMINAL LINEAR portion of the plasma profile

Question 25

the rate constant of absorption --- Ka/alpha -- is determined from the slope of what

Answer 25

the linear segment that you get AFTER feathering

Question 26

what is an important factor included in the EV Vd formula that is NOT in the IV Vd formula

Answer 26

bioavailability!

Question 27

what does it mean if the alpha value is VERY HIGH for an EV drug

Answer 27

absorption rate is VERY FAST will be very similar to IV. almost all will immediately be absorbed -- similar to IV

Question 28

after 1 feathering for EV, what is the residual line (2 compartment model)

Answer 28

pure absorption removed the effect of elimination by substracting the B line

Question 29

if the half life of absorption is 1 hours, how many half lives until over 99% of the drug has been absorbed

Answer 29

7

Question 30

true or false for 1 compartment model, Vc=Vd

Answer 30

true

Question 31

true or false it is never possible to determine the tmax just from the plasma profile

Answer 31

false - sometimes you can -- if there's a sharp peak but other plasma profiles just have a plateau because the data points around peal concentration were not obtained in the study -- in this case we need a formula

Question 32

why is the plasma profile sometimes not available

Answer 32

because the time course of the plasma concentrations is provided via a biphasic equation

Question 33

a lag time of ______ or less is NOT considered lag time

Answer 33

10-15 mins or less

Question 34

true or false conventional dosage forms exhibit little to no lag time

Answer 34

true they're designed to release their drug soon after administration

Question 35

how can you tell from looking at a graph if there is lag time

Answer 35

if A=B NOT AT ZERO TIME

Question 36

define lag time

Answer 36

time that elapses between when the drug is given and when the drug appears in systemic circulation (plasma)

Question 37

true or false lag time does NOT impact slope

Answer 37

true!!! ka and ke are still the same bc it's the same drug

Question 38

true or false lag time does NOT impact the A and B values

Answer 38

false - it does

Question 39

give an example of when conventional dosage forms can exhibit lag time

Answer 39

in some patients with specific disease states once the disease/pathological condition goes away, the drug should then be released without lag time

Question 40

true or false both delayed release and enteric coated dosage forms are intentionally designed to have lag time

Answer 40

true

Question 41

true or false interactions with foods or other drugs can cause unintentional lag time

Answer 41

true

Question 42

true or false lag time is the amount of time that absorption is delayed after the dose has been administered

Answer 42

true

Question 43

true or false at lag time, A and B will be equal

Answer 43

true

Question 44

important note when finding the AUC of a drug with lag time

Answer 44

have to use the corrected values of A and B!!!!!!!!!!!!

Question 45

true or false the rate constants remain the same regardless of lag time or not

Answer 45

true

Question 46

in EV 2 compartment model, what do the 1st and 2nd featherings remove

Answer 46

1st feathering removes the effect of elimination to give the P line 2nd feathering removes the effect of distribution to give absorption only

Question 47

rank the following according to EV beta alpha pi

Answer 47

alpha>pi>beta