pharmacokinetics Flashcards
Describe the difference between pharmacokineitics and pharamcodynamics
kinetics - the fate of the drug in the body
dynamics - the effect the drug has on the body
What factors effect the blood concetration fo a drug?
size of abminstered dose, Rate of absorption, extent of absorption, extent of distribution, extent of elimination, rate of elimination
Rate - quickly
extent - how much of it
What is dependent on the rout?
rate of absorption
who takes drugs?
chronic condition or one offs
What is the manner that is used to take a drug?
component of this is depednent on what?
dosage regime
duration of therpay and dosage regime is depedent on therapeutic objectives
describe pharmacokinetics in more detail
ADME
describe pharmacodynamics in more detail
- relationship between drug concentration at the site of action and pharmacologic response
- effects include biochemcial or phsyciological effects
- interaction of drug molecule with recpetor whihc causes initiation of a sequence of molecular events resulting in pharamcologic or toxicological response
what is the optimal range for a drug called?
therapuetic window
what happens when we have to much or too less of a drug
much - toxic range
less - ineffective range
outline the time course of a drug
drug in - concentrtaion in plasma - conctration at site of action - intensity of effect - drug out (if nescessary)
in order for a drug to have an effect there must be a certain ___ level of in available in the body at the site of action
ACTive
describe one way a drug can become activated?
metabolism
Describe the single competment open model in pharmacokinetics
refer to diagram in notes slide 6
the rate of change in cocentration over time (dC/dt) in the body (reservoir) in one comprtaemnt is depednetn on several paraemter such as : (expand on these points)
the amount of drug in the reservoir
- size of reservois
- dose given (D)
how well the drug is eliminated
- rate of elimination
- capacity of eliminating organs to remove drug
what are the main elimination processes in the body?
zero order kinetics
- constant with no respect to time
first-order kinetics
- never constant with respect to time
what two processes are used to predict how long drugs stay in the body
zero and first order kinetics
distinuigh betwen zero order and firt order kinetics
if we have limited enzymes recptors what order kinetics is it?
zero
if we have more enzymes recptors then amount of drug what order kinetics is it?
first
rate of trasmfer of drug depends on how much drug drug is availaibe?
first
rate of transfer of drug does not depend on how much drug is availaibe?
zero
too high a cconcetration of drug in this type leads to saturation of the enzyme
zero
for which order kinetics do we use half life to predict the rate of decline?
firts - since delcine with respect to time is cosntant
what order of kinetics do most drugs posses?
first
what does half life tell us
helps us predict the length of time for a drug to leave the body
also helps us determine how long it takes to reach steady state drug levels in the body after multiple doses
what is half life related too?
volume of distribution(Vd) and clearance(Cl)
after _ half-lives more then 90% of a drug has left the body
4 ( only 6.25% left in body)
Example:
drug X : half life of 2 hrs
drug Y : half life of 8 hrs
- If miss leonard is given the same dose of these drugs whihc one will take longer to leaev the body
- whihc drug will have to be dosed more frequently assuming patient complinace
- Y
- X
what is half life depednt on for zero order kinetics
magnitude of drug concentration
how can we alter the halflife of a drug?
changing plasma affinity soo more unbound drug in blood whihc will lead to change in Vd and clearance
what is the half life of drug equation
t1/2 = (0.693 VD) / Cl
why can’t we use hald life for zero order kinetics?
because it’s always changing same can be said for K (elimination rate constant)
