F3. Pharmacokinetics following IV bolus administration

Question 1

What are the two categories of i.v administration?

Answer 1

-Bolus (single dose)
-Infusion (constant rate)

Question 2

Describe the most simple situation: One-Compartment Model for IV Bolus

Answer 2

-The simplest model describing drug distribution and elimination

Let’s assume that:
-the body acts like a single and uniform compartment
-the entire dose of a drug is injected at one moment (bolus dose)
-drug distributes through the entire body (compartment) instantaneously
-the volume of the compartment remains constant
-drug elimination from the body starts immediately

Question 3

Describe blood (or plasma) concentration-time profile following IV bolus (one compartment model)

Answer 3

-Drug concentration decays exponentially
-Most drugs exhibit first-order elimination kinetics: Concentration-time data approximate a straight line on semi-log plot
EQUATION AND GRAPHS ON ONE NOTE

Question 4

How to calculate Ct, plasma concentration at time (t)?

Answer 4

ONE NOTE

Question 5

What is half life and how to calculate it?

Answer 5

Half-life (t½) is the time taken for the plasma concentration to fall by one half
ONE NOTE

Question 6

How do you find clearance?

Answer 6

-We take frequent blood samples after a single (bolus) i.v. dose
-Measure drug concentration in the plasma  plot against time
-Calculate the area under the drug concentration versus time curve (AUC)
EQUATION ON ONE NOTE

Question 7

How do you calculate Area Under the Concentration-time profile (AUC)

Answer 7

ONE NOTE

Question 8

How do you calculate th volume of distribution (Vd) from know AUC?

Answer 8

ONE NOTE

Question 9

IV bolus administration calculations sequence?

Answer 9

1. Half-life
2. Elimination rate constant
3. AUC
4. Clearance
5. Apparent volume of distribution