Chapter 1 - Basic Concepts Part 2 Flashcards
explain what half life is
time needed for the drug concentration in the plasma to decrease by 50%
what is “F”
fraction of administered dose absorbed
measure of extent of administered dose that actually reaches systemic circulation
what is lag time?
give an example of a dosage form that may have lag time
time that elapses btwn extravascular administration and when the drug appears in systemic circulation
example is enteric coating - delayed release
what is MAT
mean absorption time
average time for all the drug molecules to be absorbed (only applies to extravascular)
what is MRT
mean residence time
average amt of time for all the drug molecules of a dose to reside in the body
what is Ka/Km/Ke
Ka - rate constant of absorption
measure of the rate at which the drug is absorbed after it has become available for absorption
Km = rate metabolism
Ke = rate elimination
term for the steady-state concentration of the drug in plasma
Css – plateau level for chronic drugs
what do K12 and K21 mean
rate constants of TRANSFER
ie - between plasma and the tissues
Vd
volume of distribution - volume of body fluid in which the drug is either dissolved or distributed
for any extravascular drug, what must happen before the drug gets into systemic circulation
ABSORPTION
another term for site of action
receptor site
another name for biophase
receptor site – drug that is causing therapeutic effect
drug in plasma is assumed to be in equilibrium with drug where?
drug in biophase
true or false
extravascular routes of administration do not go through 1st pass effect (except oral)
true
extravascular except oral bypasses 1st pass
true or false
a prodrug is not a drug
TRUE - it itself as no activity
true or false
a drug can either be activated or deactivated through the liver
true - case of prodrug
“central compartment”
plasma
drug only absorbs in plasma NOT BLOOD
*****average volume of plasma in a normal 70kg (154lb) adult
3 LITERS
AROUND __% of body weight is water
60%
for an IV injection, what is the typical minimum Vd
3 LITERS
BUT as the plasma distributes to other tissues, Vd will keep increasing
“central compartment”
plasma
how is some alcohol excreted
pulmonary - that’s why breathalyzers are a thing
marker to indicate therapeutic levels at receptor site
we use plasma levels
3 meds that we don’t need to measure plasma concentration of drug to evaluate therapeutic effect
blood pressure meds
diabetes meds
anticoagulants
true or false
drug in central compartment immediately distributes to tissue
false
takes time
initially, amount in tissue will be zero
relationship between concentration at plasma/central compartment vs tissue
INDIRECT relationship
when conc at central compartment high, conc at tissue site is low.
needs time to distribute there
name the 2 types of pharmacokinetics
linear pharmacokinetics
nonlinear pharmacokinetics
true or false
we measure drug concentration at the receptor site
FALSE
we measure plasma conc
true or false
most drugs exhibit nonlinear pharmacokinetics
FALSE - most are linear
in linear pharmacokinetics, what 2 things are proportional to the dose
what is NOT affected by the dose
cmax
cp (plasma conc)
as dose increases, plasma conc and cmax also increase
pharmacokinetic parameters are NOT AFFECTED by the dose, except for cmax and AUC
true or false
in linear pharmacokinetics, as the dose increases, t1/2 also increases
FALSE - does not change
a drug follows linear pharmacokinetics.
50mg dose produces a maximum Cp (plasma concentration) of 10mcg/L
what will be the Cp if the dose is doubled?
Cp will be 20mcg/L
is the Cmax of a particular drug identical in all patients?
NO - individual variations exist
however, if it follows linear kinetics, should still follow this
true or false
in non-linear pharmacokinetics, Cp is NOT proportional to the dose
TRUE
is “dose-dependent pharmacokinetics” considered linear or nonlinear kinetics?
nonlinear
because if you change the dose, EVERYTHING CHANGES (including t/12, AUC)
which is more difficult to dose correctly - linear or nonlinear pharmacokinetics
nonlinear is more difficult to dose
“capacity-limited” pharmacokinetics
non-linear pharmacokinetics
true or false
in non-linear pharmacokinetics, “the extent of absorption is not proportional to the dose”
true
true or false
in non-linear kinetics, elimination follows 1st order kinetics
FALSE - does not
true or false
in linear kinetics, we expect the Css and Cmax to double if the dose doubles
true
true or false
in non-linear kinetics, the amount of drug excreted in the urine is NOT proportional to the dose administered
true
true or false
for non-linear kinetics, the half life does not change if the dose changes
FALSE - it does
either increases or decreases – not predictable
(normally it would increase)
true or false
in non-linear kinetics, the AUC is NOT proportional to the amount of drug available for absorption
true
true or false
in non-linear kinetics, the cmax is not proportional to the dose
true
a drug follows non-linear kinetics.
the cmax has increased MORE THAN EXPECTED when the dose was increased
name a possible mechanism for this
what is the term for this phenomenon
the process of removing the drug from the body has become saturated, meaning that whatever amount of drug is administered will be in the body and not able to be eliminated
significant, unexpected increase in concentration
this is Michaelis Menten/saturable pharmacokinetics
a drug follows non-linear kinetics.
the cmax has increased LESS than what was expected with the amount of dose given.
name 2 possible mechanisms for this
- the drug is highly protein bound - as more dose is given, it just saturates the plasma proteins more (or faster elimination)
- Autoinduction of metabolism
define clinical pharmacokinetics
applying pharmacokinetic principles to therapeutic management of individual patients
goal of clinical pharmacokinetics
increased effectiveness and/or decreased toxicity
what is the difficulty with clinical pharmacokinetics
every individual has a variation in drug response, despite the drug and dosage form being exactly the same
4 general factors that result in each patient having different reactions to each drug, despite the drug, dose, route, dosage form, etc being exactly the same
-patient factors
-severity of disease
-other drugs given at same time
-environmental factors
true or false
the concentration of drug in plasma is DIRECTLY RELATED to the concentration at the site of action
true
true or false
patient’s genetics do not change their response to drugs
FALSE - usually does
true or false
the therapeutic Cp is the same for all patients
false
since each patient responds differently, drug manufacturers publish what 4 values based on studies of a large population of humans studies
maintenance dose
half life
Vd
Cp (therapeutic drug plasma conc)
pharmacodynamics is the relationship between ____ and ____
the drug conc at site of action and the magnitude of the effect produced (both the intensity and time of effect. effect can either be good or bad (toxic)
true or false
pharmacokinetics and pharmacodynamics are identical
FALSE - complementary
________- deals with the interaction between the drug and its receptors
pharmacodynamics
what is the 1 parameter that both pharmacodynamics and pharmacokinetics have in common
receptor site concentration
*drug solubility is the principle determinant of oral absorption because…
it is the principle determinant of drug dissolution rate
true or false
drug solubility is the principle determinant of intestinal membrane permeability
FALSE - principle determinant of drug dissolution rate
lot of other factors determine permeability – solubility still does too, but NOT the principle determinant
true or false
as the particle size decreases, the dissolution rate increases, surface area increases, and the radius increases
FALSE
all are true except for the radius one
as particle size decreases, radius decreases too
