Lecture 4 - Pharmacokinetics (Kinetics and Definitions) Flashcards
What is the definition of first-order kinetics regarding drug clearance?
The rate of elimination of a drug where the amount of drug decreases at a rate proportional to the concentration of drug remaining in the body.
What is the definition of zero-order kinetics regarding drug clearance?
A constant amount of drug is removed per unit time independent of the remaining concentration of drug in the body.
What is first-order kinetics and what is the equation?
First-order kinetics is the rate of drug removal dependent on the remaining concentration of drug in the body. Applies to most drugs in clinical use. T1/2= Vd x 0.7/Cl T1/2 is half-life Vd is Volume of distribution Cl is Clearance
What is zero-order kinetics?
A constant amount of drug is removed per unit time. Alcohol is removed at a constant rate = zero-order kinetics.
What do graphs of zero and first order kinetics look like?
Zero-order = straight line sloping downwards First-order = curved line like an exponential curve on its side slowing downwards
What is the definition of first-pass metabolism?
Any metabolism that occurs before the drug enters the systemic circulation.
- Phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it enters systemic circulation
What is the definition of Bioavailability?
Proportion of the administered drug that is available within the body to exert its pharmacological effect.
What is the definition of Apparent Volume of Distribution?
The Volume in which a drug appears to be distributed.
What is the definition of Biological Half-Life?
Time taken for the concentration (in blood/plasma) of drug to fall to half its original value.
What is the definition of Clearance?
Blood/plasma clearance is the volume of blood/plasma from which drug is removed per unit time.