Liver Function and Physiology Flashcards
In terms of liver blood supply - what percentage comes from the portal vein?
75% comes from the portal vein.
What is the relationship between drug metabolism and plasma concentration?
Drug Metabolism reduces plasma concentration.
How does drug metabolism reduce plasma concentration?
Changes the drug to a metabolite.
Makes the drug MORE water soluble so it can be eliminated.
What are the 3 enzyme kinetics?
First - Order
Zero - Order
Non - Linear
What are first order enzyme kinetics?
Doubling the concentration of the drug DOUBLES the reaction rate.
What are zero order enzyme kinetics?
Reaction rate is ALWAYS the same irrespective of drug concentration.
What are non - linear enzyme kinetics?
Reaction rate INCREASES with the drug concentration until enzymes saturated and the rate reaches constant.
What is the effect of enzyme induction?
- Increased enzyme activity.
- Increased metabolism of substrate drugs.
- Lower plasma concentrations / Less efficacy and toxicity*
What is the effect of enzyme inhibition?
- Decreased enzyme activity.
- Reduced metabolism of substrate drugs
- Higher plasma concentrations / More efficacy and toxicity*
What is the mechanism of enzyme induction?
Increased gene and protein expression.
What is the mechanism of enzyme inhibition?
Same principles as for other enzymes.
Quicker than onset / offset for induction
What are the factors which affect drug metabolising enzymes?
Age Smoking Alcohol Food Drugs Liver Disease Genetics Pregnancy
What is the therapeutic range?
Small change in plasma concentration CAUSES significant effect.
