Intro to pharmacokinetics Part 2 Flashcards
What varies overtime in first order kinetic modelling ?
The rate of elimination
What can be said about the half life in first order kinetic modelling ?
It stays constant
Which pharmacokinetic model is less accurate and why?
1st compartment model
Assumption that the human being is one big puddle of water and is a less accurate model when it comes to time
What is the two-compartment model?
There is a tissue compartment and a central compartment and is a more accurate model
Why is half life important ?
It allows you to calculate the clearance as the clearance is inversely proportional to the drug
How do you calculate clearance ?
Volume of plasma cleared of drug / unit time
The bigger the clearance the ________ the half life
Smaller
After 5 half lives, how much of the drug have you eliminated ?
96.9% - essentially eliminated
What varies in zero order pharmacokinetics ?
Half life (opposite of first order)
What causes zero order pharmacokinetics (RARE)?
When the elimination action pathways are saturated e.g. alcohol can cause this
Why would a patient suffer from side effects longer due to a zero order pharmacokinetics drug?
As the half life is longer
What is steady state ?
the rate of infusion = the rate of elimination
What is the therapeutic window ?
The space between the minimum effective concentration and the minimum toxic concentration
If you wanted to get the drug into the therapeutic window quickly, what would you do?
Use an IV or a double dose
How do you calculate dose rate?
Drug concentration x clearance
