7 - Pharmacokinetics Flashcards
Key PK properties of a drug
Bioavailability
Vol. of dist.
Clearance
Elimination of Half life
Volume of distribution
An apparent volume that would be necessary in order to account for the initial plasma drug conc. Following a dose of the drug
Units of volume or volume per unit body weight
How to calculate volume of distribution in an animal
Concentration = Dose/plasma conc.
What does volume of distribution allow you to predict
Peak plasma concentration of a drug at a given dose in an animal
When rate of drug movement from blood into tissues is less than rate of drug movement from tissues into blood, is the vol of dist. Large or small.
Very small
3 things that can change Vol D
Body fat
Poor tissue perfusion
Reduction in plasma proteins
1st order kinetics vs. 0 order kinetics
0 order: animal eliminates fixed amount per unit time
1st order: drug eliminated at exponential rate
1st order kinetics properties
Fixed fraction of drug is eliminated per unit time
Can convert to 0 order if the elimination process is saturated
Elimination is proportional to concentration
Half life
A 3 part video game that has left everyone on a cliffhanger for the last 5+ years….damn you valve.
Half life
Time required to eliminate one half of drug present in plasma
-simple units of time
-constant for 1st order drugs
Inversely proportional to the elimination rate constant
What is the number of half lives for a drug to be generally considered eliminated
5 half lives
What are the two phases uses in all PK estimations
1: redistribution phase
2: Elimination phase
What phase do you use while calculating half life
Base it off of elimination phase
If a drug was administered IV what is the bioavailability
100%
How to find initial plasma concentration when not given
Follow the elimination phase line back to the initial time
