Lab 9: One Compartment Model Single Dose Flashcards
What does one compartment model represent?
The distribution of a drugs throughout a single compartment and its elimination
Why is a model situation used to study pharmacokinetics?
You can obtain experimental results in a short amount of time
What does the volume of water in a jug represent?
The volume of distribution
What does amaranth represent?
The drug
What does the magnetic stirrer represent?
The effect of the cardiovascular system in distributing the drug throughout the body
What does the output tube represent?
The eliminating organs such as the kidneys and liver. The output tube mimics drug clearance
What is the purpose of the input tube?
This replaces the water at the same rate so there is no net loss of fluid from the system
Which pharmacokinetic parameters can be directly measured in this single compartment model?
The volume of distribution and the clearance
What is used to measure the concentration of drug at various times?
Samples of fluid collected at defined times
What is the purpose of the spectrophotometer?
Measures the absorbance of the solution which is proportional to the concentration of the drug in the water.
How is the calibration curve conducted?
By measuring the absorption over a range of concentrations
Why were predictions of concentrations of the known standard solutions made in duplicate?
To quantify the precision and accuracy of the assay system
And then to define the minimum quantifiable concentration
How can the pharmacokinetic parameters of volume of distribution and clearance be ESTIMATED?
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.
How do you find the concentration at time 0 ?
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
How do you find the Vd having found C0?
Vd = dose / C0
How is the half life obtained?
By reading the time taken for the concentration to fall from C0 to C1/2
How is the elimination clearance estimated?
By using the half life equation to find Cl
What is the minimum quantifiable concentration?
The lowest concentration which can be measured with acceptable accuracy (+/-20%) and precision (</=20%).
What is precision?
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
What is accuracy ?
The measure of how close a measurement is to its true value
I.e, accuracy = (measured value - True value/true value) x 100
What volume of amaranth is to be administered if we want 60mg of a 50mg/mL stock solution in the jug?
Dose/stock
= 60/50
= 1.2mL
