Drug clearance Flashcards
drug clearance
Indicates the theoretical volume of biological fluid from which a drug is cleared
What 2 processes are involved in the removal of drugs from the body?
- Excretion (discharged from the body)
- biotransformation (metabolism)
How are fat soluble drugs excreted from the body
they must first be biotransformed into water soluble/polar drug and then they can be excreted
tWhere does this biotransformation usually take place?
Liver in two phases
1. oxidation, reduction, hydrolysis
2. conjugation
First order Elimination
measured rate of elimination is related to a constant fraction of drug concentration
zero order elimination
Constant amount of drug is eliminated per time
it is independent of drug concentration
Clearance
Volume of plasma which all drug is eliminated
total body clearance formula
Cltb= (k) x (Vd)
What does clearance by an organ depend on
It depends on the blood flow coming to the organ and the extent to which the organ extracts the drug
what type of drugs are seen being excreted from the liver
hepatic clearance is a major route for non-polar lipophilic drugs
What factors does E include when discussing Clh
blood flow
plasma protein binding
intrinsic ability of liver
What E value and each factor will give a high extraction
E=0.7-1
blood flow will produce changes but plasma protein and intrinsic ability will not affect extraction
What E value and factor will affect low extraction
E=0-0.3
Blood flow will not impact It but intrinsic ability and plasma protein binding will
What is Clh sensitive to for high extraction
hemodynamic (blood) changes
What is Clh sensitive to for low extraction drugs
Changes in enzyme function
