Lecture 4 - Pharmacokinetics (Kinetics and Definitions)

Question 1

What is the definition of first-order kinetics regarding drug clearance?

Answer 1

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.

Question 2

What is the definition of zero-order kinetics regarding drug clearance?

Answer 2

A constant amount of drug is removed per unit time independent of the remaining concentration of drug in the body.

Question 3

What is first-order kinetics and what is the equation?

Answer 3

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

Question 4

What is zero-order kinetics?

Answer 4

A constant amount of drug is removed per unit time. Alcohol is removed at a constant rate = zero-order kinetics.

Question 5

What do graphs of zero and first order kinetics look like?

Answer 5

Zero-order = straight line sloping downwards
First-order = curved line like an exponential curve on its side slowing downwards

Question 6

What is the definition of first-pass metabolism?

Answer 6

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

Question 7

What is the definition of Bioavailability?

Answer 7

Proportion of the administered drug that is available within the body to exert its pharmacological effect.

Question 8

What is the definition of Apparent Volume of Distribution?

Answer 8

The Volume in which a drug appears to be distributed.

Question 9

What is the definition of Biological Half-Life?

Answer 9

Time taken for the concentration (in blood/plasma) of drug to fall to half its original value.

Question 10

What is the definition of Clearance?

Answer 10

Blood/plasma clearance is the volume of blood/plasma from which drug is removed per unit time.