Chapter 12 ~ Extravascular Bolus Dose Flashcards
why is there a whole separate chapter for extravascular bolus dose kinetics when we just did IV
because all extravascular routes need to be absorbed — intravascular does not
what is absorption rate constant
Ka
true or false
intramuscular injections do not undergo absorption
FALSE - they do
what is absorption
passage of drug from the site of administration and INTO THE PLASMA by absorbing through a membrane
TRUE OR FALSE
the absorption of drugs generally follows 1st order drug input
true
true or false
the plasma profile of EV vs IV bolus dose will be the same
FALSE - will not
true or false
for extravascular routes, the entire dose is NOT absorbed all at once
true
the 2 more important differences in the plasma profiles of IV vs EV:
-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)
TRUE OR FALSE
the amount of drug in the plasma immediately after IV administration IS EQUAL TO the amount of dose administered
true
what is the amount of drug in the plasma immediately after an EXTRAVASCULAR administration of dose? why?
ZERO
bc the drug has to be absorbed before it appears in the plasm
true or false
the absorption of the entire dose of a drug is NOT an instantaneous process
true
true or false
absorption most likely is an active process
false - passive. fick’s first law
true or false
even though it takes more time, IV and EV have the same extent of absorption
false - do not
absorption of EV drug takes time –decreased rate. this results in drug loss and decreased extent of absorption
for IV, why does the concentration immediately start declining
due to elimination and/or distribution
for EV, the delay between administration and actual appearance in the plasma may range form __ to ___
few seconds (buccal)
to more than an hour (EC)
most conventional EV dosage forms are designed to release their active ingredient when?
almost immediately after administration. there shouldn’t be a significant delay in plasma appearance
the plasma profile for EV is a function of what 2 rate constants
absorption and elimination
EV –
the first order plot of concentraiton vs time after EV bolus dose yields a _______ plot
why
biphasic
due to a mixture of 1st order processes — first order process of absorption and first order process of elimination (from plasma)
what are the 3 phases on an EV biphasic plot
absorptive
post-absorptive
elimination
during the predominantly absorptive phase, ______ also begins. however…..
elimination
but the elimination is much less predominant than the absorption
as absorption continues, elimination gets more and more predominant
for EV plasma profile, when does the rate of drug absorption=the rate of elimination
when the plasma profile is at PEAK concentration
the biphasic curve is resolved into 2 straight lines.
what do each of these 2 lines represent
BIPHASIC INDICATES EV
1 line is absorption and the other is elimination
true or false
for EV, 2 straight lines indicates 1 compartment model
TRUE— bc have to account for absorption!!!!!!
FOR IV – JUST 1 STRAIGHT LINE MEANS 1 COMPARTMENT
beta, the rate constant of elimination, is determined from the slope of what
THE TERMINAL LINEAR portion of the plasma profile
the rate constant of absorption — Ka/alpha – is determined from the slope of what
the linear segment that you get AFTER feathering
what is an important factor included in the EV Vd formula that is NOT in the IV Vd formula
bioavailability!
what does it mean if the alpha value is VERY HIGH for an EV drug
absorption rate is VERY FAST
will be very similar to IV. almost all will immediately be absorbed – similar to IV
after 1 feathering for EV, what is the residual line (2 compartment model)
pure absorption
removed the effect of elimination by substracting the B line
if the half life of absorption is 1 hours, how many half lives until over 99% of the drug has been absorbed
7
true or false
for 1 compartment model, Vc=Vd
true
true or false
it is never possible to determine the tmax just from the plasma profile
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
why is the plasma profile sometimes not available
because the time course of the plasma concentrations is provided via a biphasic equation
a lag time of ______ or less is NOT considered lag time
10-15 mins or less
true or false
conventional dosage forms exhibit little to no lag time
true
they’re designed to release their drug soon after administration
how can you tell from looking at a graph if there is lag time
if A=B NOT AT ZERO TIME
define lag time
time that elapses between when the drug is given and when the drug appears in systemic circulation (plasma)
true or false
lag time does NOT impact slope
true!!! ka and ke are still the same bc it’s the same drug
true or false
lag time does NOT impact the A and B values
false - it does
give an example of when conventional dosage forms can exhibit lag time
in some patients with specific disease states
once the disease/pathological condition goes away, the drug should then be released without lag time
true or false
both delayed release and enteric coated dosage forms are intentionally designed to have lag time
true
true or false
interactions with foods or other drugs can cause unintentional lag time
true
true or false
lag time is the amount of time that absorption is delayed after the dose has been administered
true
true or false
at lag time, A and B will be equal
true
important note when finding the AUC of a drug with lag time
have to use the corrected values of A and B!!!!!!!!!!!!
true or false
the rate constants remain the same regardless of lag time or not
true
in EV 2 compartment model, what do the 1st and 2nd featherings remove
1st feathering removes the effect of elimination to give the P line
2nd feathering removes the effect of distribution to give absorption only
rank the following according to EV
beta
alpha
pi
alpha>pi>beta
