Lab 9: One Compartment Model Single Dose

Question 0

What does one compartment model represent?

Answer 0

The distribution of a drugs throughout a single compartment and its elimination

Question 1

Why is a model situation used to study pharmacokinetics?

Answer 1

You can obtain experimental results in a short amount of time

Question 2

What does the volume of water in a jug represent?

Answer 2

The volume of distribution

Question 3

What does amaranth represent?

Answer 3

The drug

Question 4

What does the magnetic stirrer represent?

Answer 4

The effect of the cardiovascular system in distributing the drug throughout the body

Question 5

What does the output tube represent?

Answer 5

The eliminating organs such as the kidneys and liver. The output tube mimics drug clearance

Question 6

What is the purpose of the input tube?

Answer 6

This replaces the water at the same rate so there is no net loss of fluid from the system

Question 7

Which pharmacokinetic parameters can be directly measured in this single compartment model?

Answer 7

The volume of distribution and the clearance

Question 8

What is used to measure the concentration of drug at various times?

Answer 8

Samples of fluid collected at defined times

Question 9

What is the purpose of the spectrophotometer?

Answer 9

Measures the absorbance of the solution which is proportional to the concentration of the drug in the water.

Question 10

How is the calibration curve conducted?

Answer 10

By measuring the absorption over a range of concentrations

Question 11

Why were predictions of concentrations of the known standard solutions made in duplicate?

Answer 11

To quantify the precision and accuracy of the assay system

And then to define the minimum quantifiable concentration

Question 12

How can the pharmacokinetic parameters of volume of distribution and clearance be ESTIMATED?

Answer 12

For simple models and experimental designs, these can be estimated using a simple graphical technique

For complex models, this requires the use of non linear regression.

Question 13

How do you find the concentration at time 0 ?

Answer 13

We use the equations on the graphs of the data to find the point at where the concentration vs time line intersects the concentration axis

Question 14

How do you find the Vd having found C0?

Answer 14

Vd = dose / C0

Question 15

How is the half life obtained?

Answer 15

By reading the time taken for the concentration to fall from C0 to C1/2

Question 16

How is the elimination clearance estimated?

Answer 16

By using the half life equation to find Cl

Question 17

What is the minimum quantifiable concentration?

Answer 17

The lowest concentration which can be measured with acceptable accuracy (+/-20%) and precision (</=20%).

Question 18

What is precision?

Answer 18

The measure of error reproducing a measurement.
This is calculated from the SD of the replicates divided by their mean.

I.e. The precision (CoV) = SD/mean x 100

Question 19

What is accuracy ?

Answer 19

The measure of how close a measurement is to its true value

I.e, accuracy = (measured value - True value/true value) x 100

Question 20

What volume of amaranth is to be administered if we want 60mg of a 50mg/mL stock solution in the jug?

Answer 20

Dose/stock
= 60/50
= 1.2mL