Pharmacokinetics 4 Flashcards
What is drug clearance?
The sum of all the drug-eliminating processes, principally determined by hepatic metabolism and renal excretion.
It can also be defined as the theoretical volume of fluid from which a drug is completely removed in a given period of time.
What is the main organ which excretes drugs?
The kidneys
List some other excretory mechanisms
Bile (faeces); sweat; exhaled air; saliva; breast milk
List some causes of low drug clearance
Normal variation Renal impairment Liver impairment Enzyme inhibition Genetic poor metaboliser Neonate Old age
List some causes of high drug clearance
Normal variation
Increased renal blood flow
Genetic hypermetabolism
Enzyme induction
Define half life
Time for the concentration of drug in plasma to halve
What does half life provide information on?
Provides information on:
Time course of drug elimination
Time course of drug accumulation
Choice of dose interval
How many half lifes does it take to eliminate a drug generally?
At least 5 half lives
What is the steady state?
Measures the time course of drug accumulation
What is the loading dose?
In order to saturate compartment so clinical effect occurs as the drug accumulates in the plasma
What is loading dose determined by?
Volume of distribution
What is maintenance dose determined by?
Clearance
What is the dose interval determined by?
Half life
Give the formula for half life
Half life = Volume of distribution / Clearance
