Biopharmaceutics

Question 1

What are the two main pharmacokinetic models?

Answer 1

1. One compartment model
   - Intravenous
   - Oral
2. Two compartment model

Question 2

What are the three types of dosing regimens?

Answer 2

1. Continous IV injection
2. Intermittent IV injection
3. Multiple oral doses

Question 3

How are estimates of the pharmacokinetic parameters generated?

Answer 3

From analysis of Cp vs. time curve

Question 4

What are pharmacokinetic models?

Answer 4

Simplified mathematical description of physiological processes

Focus of PHAR 226

Question 5

What is a physiological model?

Answer 5

Relate change in concentration to realistic body compartments, organs (Liver, kidney, intestines, etc), and blood flows

Question 6

What is a compartmental model?

Answer 6

The body is envisioned as a collection of compartments with drug being transferred between compartments. A compartment is a mathematical unit and not a physiological one

Question 7

What assumptions are made for a one compartment model?

Answer 7

• Drug distributes throughout the body instantaneously (due to distribution via perfusion)
• Drug leaves the body by a first-order process (fraction of drug is eliminated per unit time)

Question 8

How quickly does the blood circulate through the body

Answer 8

Total blood volume: 5L

5L blood circulates through the heart within a minute
(very rapid distribution)

Question 9

Do lipophillic drugs acheive tissue:blood equilibirum quickly?

Answer 9

No, because they will distribute into the adipose tissue and it has limited perfusion (causing equilibrium to be acheived with a longer period of time)

Question 10

Does the one compartment model apply to all drugs?

Answer 10

No, for some drugs they are better explained by multi-compartment models

Question 11

What is the difference between zero and first order kinetics?

Answer 11

Zero order: Same amount of drug released per unit time

First order: Fractional amount of drug released per unit time (elimination rate proportional to plasma concentration)

Question 12

What does the variable Ab represent?

Answer 12

Amount of drug in body

Question 13

What does the variable Kd represent?

Answer 13

Can also be known as Ke or Kel

Disposition rate constant or elimination rate constant (they are the same)

Question 14

Review handout for differential equation first-order kinetics