Pharmacokinetics Flashcards
What is the therapeutic index?
a measure of drug safety, ratio between the drug/ concentration of the drug producing toxicity and the dose/ concentration that produces a therapeutic effect
What does a large therapeutic index mean?
more favourable margin of safety in the drug
What does the area under the curve mean?
overall exposure of the body to the drug, reflects the amount absorbed into the bloodstream and how long the drug stays in the system
‘bioavailability’
What is volume of distribution defined as?
the theoretical volume needed to dilute the total amount of drug in the body at a given time to acheive the measured plasma concentration
What is drug clearance defined as?
the volume of plasma that is completely cleared ofa drug per unit time
What is steady-state concentration?
concentration of the drug in the plasma reached when the rate of drug absorption is equal to the rate of drug elimination following repeated or continuous dosing
What do zero and first order kinetics refer to?
changes to the amount of a drug as a function of time
What is zero order elimination?
a constat amount of drug eliminated per unit of time
What is first order elimination?
a constant fraction of a drug is eliminated per unit time- as the concentration drops, the elimination rate drops as well
What is the drug elimination half life?
the time taken for the drug plasma concentration to decrease by 50%, calculated during the elimination phase
What is drug bioavailability?
Drug Bioavailability is the fraction of administered dose
of the parent drug that reaches the systemic circulation.
What kind of administration will have the highest bioavailability?
iv (100%)
What is volume of distribution?
is defined as the theoretical volume needed to dilute the total amount of drug in the body at a given time to achieve the measured plasma concentration
What is the volume of distribution calculation?
Administered dose over the plasma concentration
What is the definition of drug clearance?
efficiacy of drug elimination
What is overall drug clearance the sum of?
the sum of hepatic clearance + renal
clearance + clearance by other routes
What is steady-state concentration?
is the concentration of drug
in the plasma reached when the rate of drug absorption is equal to the
rate of drug elimination following repeated or continuous dosing
What is the function of a loading dose?
- Loading dose administered at the start of therapy
- Steady-State is then reached quicker
What is the one-compartment model?
drug is absorbed from its site of administration into a single central
compartment
What is the two compartment model?
All drugs are distributed, to some extent, into tissues
* Two-compartment models describe the pharmacokinetics of
most drugs
