General principles of drug action.

Question 1

One-compartment model

Answer 1

Oversimplified model that a human consists of single well-stirred compartment.
Ka -> Vd -> Ke
Drug is absorbed, immediately distributed and subsequently eliminated.

Question 2

Kinetic orders

Answer 2

Relate the plasma concentration of a drug and its rate of elimination from the body.

Question 3

First-order kinetics

Answer 3

Decrease in drug is dependent on the [plasma].
Concentration of the drug is the rate limiting factor.
Exponential decrease
Most drugs.

Question 4

Two-compartment model

Answer 4

Drugs will only enter the body tissues (peripheral compartment) via the plasma (central compartments).
Predicts a fast and slow phase of distribution between the compartment.

Question 5

Zero-order (saturation) kinetics

Answer 5

Decrease in drug is independent of the plasma conc.
Rate is constant due to limiting factor.
Straight line.
Alcohol.

Question 6

Why is the volume of distribution important?

Answer 6

It is used to calculate drug dose.
Plasma concentration of a drug to reach its target organ in an effective concentration, therefore defines dose.
Plasma concentration is affected by the Vd of a drug.

Question 7

Low Vd

Answer 7

Confined to the plasma - high plasma conc.

Question 8

High Vd

Answer 8

Accumulated in peripheral tissue - low plasma conc.