Test 2 Flashcards
Cmax correlates with:
both rate and extent of absorption
bioavailability depends on
both rate and extent
cpmax is decreased by
a decrease in rate of absorption
If the absorption rate for formulation A was SLOWER than formulation B and relative rate of absorption for A was the same as B then:
cman for A would be less than B
if the extent of absorption was LESS for product A than B and relative rate of absorption for A was the same as B then:
cmax for B would be higher than A
Drug A and B bind to the same albumin molecule: A is already being given to pt. what is correct concerning giving drug B
at the same concentrations the drug with the higher Ka will have the lowest Fu
two drugs compete for the same binding site on a protein. what condition would yield higher binding for A than B?
higher [A]
when a drug undergoes hepatic metabolism, the kinetics appear first order when
[drug] are lower than the value of the Km
the effect of Vmax on the rate of drug metabolism when a single bolus dose is given would show:
the observed half life for metabolism would be smaller for larger Vmax values
What is the characteristic of simple competitive inhibition
having the same Vmax, but a larger Km when the inhibitor is present
What 2 things are expected if plotting Cmax(axis) vs % dissolved at 30 minutes
1) as the % dissolved decreased, the max value would decrease
2) as the % dissolved increased, the max value would increase
smoking is considered an environmental enzyme inducer for some drugs. if pt stops smoking after being stabilized on a drug, you expect
drug levels of drug to increase
the classic full crossover bioavailability testing corrects for
the differences between people
a repeated, full crossover design corrects for
BOTH the variability within the same subject and between different subjects
if the full crossover design is not repeated, it does not correct for
variability within the same subject
absolute bioavailability is obtained by comparing results from a particular drug product or dosage for and comparing it to
data from an IV bolus dose
bioavailability of a drug deals with
rate and extent of absorption
relative bioavailability compares
a new product or formulation to an existing formulation
absolute availability could
be qual to zero
can absolute bioavailability be equal to zero?
yes
absolute bioavailability cannot
be greater than 1
absolute availability (F)=1 when
ALL of drug is absorbed
Tmax is
the time of peak plasma concentration
AUC measures
the extent of drug bioavailability
AUC is the area under the drug plasma levels time curve
and is equal to the amount of unchanged drug reaching the general circulation divided by the drug clearance
Units for AUC are
concentration time
AUC is not proportional if one of the pathways for elimination becomes saturated, which causes
prolonged half life
Tmax is the best indicator of
the relative rate of drug absorption
if the absorption rate for A was faster than B, but the extent of absorption was the same for A and B then tmax
for A would be less than B
if bioavailability is less than 1, and the AUC obtained by a direct intraportal inject is the same as when you gave the same dose of drug orally:
the drug was subject to first pass metabolism
An IV bolus dose and a capsule are given. Rate of urinary excretion is measured and plotted. this data:
can be used to estimate bioavailability of the capsule formulation
in correlating cpm values in vivo with the % dissolved in vitro at time=20 minutes, we expect, if a correlation exists that
cpmax will be smaller if the dissolution rate is slower
The boys whitney eqn predicts
if the particle size is smaller the dissolution rate will potentially be faster
the absorption of a very lipid soluble, unionized drug molecule, will most like be eliminated by rate of
dissolution
to pass the dissolution test in stage 1 (first 6 units)
no result is less than Q + 5%
the absorption of a very lipid soluble, unionized but somewhat water soluble drug will be limited by rate of
perfusion
dissolution rate of a weak acid
may be slower at a lower pH
a drug that would be limited by diffusion rate rather than perfusion rate is most likely
a polar water soluble drug of a large size
usually disintegration is
not rate limiting, but may be if intended
clearance of a drug:
is constant for a physiologically stable person who eliminates the drug as a first order process
clearance can be calculated by
extraction ration * blood flow
compare drug elimination and clearance
elimination rate changes over time while clearance is constant
renal cleraance eqn
GFR + active secretion - reabsorption
oxidation, reduction and hydrolysis rxns are
phase I reactions
the most frequently found conjugation reaction involves
glucuronic acid
for a drug known to exhibit non linear pharmacokinetics, as dose increases:
the steady state concentration increases more than predicted amount of dose increase
passive tubular reabsorption would be lowest for
a weak base at pH 2
passive tubular reabsorption would be highest for
a weak acid at pH 3
passive reabsorption of a drug:
reduces renal clearance
ionization of a weak base
decreases its lipid solubility
active secretion of a drug by the renal system:
increases renal clearance
facilitated diffusion occurs
only in the presence of a carrier
a carrier mediated process for a drug absorption
will saturated carrier at drug concentrations approximately twice the value of Km
passive diffusion
rate increases in direct proportion to drug concentration
all drugs are subject to some biliary clearance,
is subject to enhancement by active secretion into the bile
A scatchard plot is used to determine
Ka and n
the r in the protein binding equation what does it stand
equals ratio of moles of drug bound per total mole of protein
the n in protein binding eqn refers to
the number of sites for a particular drug per protein molecule
the apparent Vd will be very large when
the drug is more bound to tissues than plasma proteins
IV administration is assumed
to be 100% bioavailable
IM injections can be used
for oil based or insoluble components
rectal admin provides:
good absorption from solutions retained long enough
buccal route is preferred to oral when
drug is subject to high first pass metabolism
a suspension drug form may be necessary for
aqueously insoluble or unstable drugs
