W2: Compartmental analysis for pharmacokinetic parameters Flashcards
What is a serum concentration-time profile?
Basically we are analyzing the concentration of a substance in the serum at a long period of time.
Take blood at different hour to see the concentration.
This can tell us the ADME pattern of the drug.
IF you plot an arithmetic graph of the serum concentration-time profile, you can see that ________
the serum concentration of the drug reduces over time because the drug had been distributed across the body
If you convert the arithmetic graph to semi-log graph, you can analyze the ________ and ________.
compartmental model and route of administration.
A semi log graph with a descending linear pattern as time increases shows a________ compartment and __________ administration.
One compartment because the reduction of the drug is instantaneous (linear).
Intravenous administration because at time = 0, the concentration of drug decreases immediately. Drug already in systemic circulation.
you plot a semi-log graph, you get the gradient of y=20.006 ^ -0.3x . What can you do with this info?
The gradient of a semi-log graph has the elimination rate constant.
y = 20.006 ^ -0.3x , the elimination constant is -0.3.
Where can you get your Cmax from a serum concentration-time profile?
The highest value of drug concentration in the system. The peak of y-axis.
Where can you get your Tmax from a serum concentration-time profile?
The x-value of your Cmax is the Tmax.
Extravascular administration only has oral and dermal route. True or False?
FALSE. Extravascular also includes subcutaneous, intramuscular and intradermal as well. These are parenteral administration but the drug does not enter the blood immediately (intravenous).
What pattern will the semi-log graph be if its a two compartment model and intravenous administration route?
There will be two slopes instead of one. The initial descending small slope near Cmax, and another steady, long slope as time increases.
The descending small slope is initial phase and long slope is terminal phase. Two slope also means two gradient.
What equation is this and what value does each symbol represent:
Ct = A e^-αt + B e^-βt
This is an equation for two compartment model. The initial phase is the A e^-αt while the terminal phase is B e^-βt.
The y-intercept of the long slope is B and the gradient for the long slope is -β.
Similarly, the y-intercept of the descending small slope is A and the gradient for the long slope is -α.
Initial phase is the ________ phase
distribution, where the small slope is.
Terminal phase is the ____________ phase
elimination, the long slope till the end of time
What is the difference between half life at the initial phase and terminal phase?
Half life of the initial phase is the time required for the drug to be distributed .
Half life of the terminal phase is the time required for the drug to be eliminated.
Complete this half life formula:
T1/2 = ______ / α or β
T1/2 = 0.693 / α or β
Depending on what you divide, you will get the half life of distribution or elimination.
** 0.693 is also ln2
Distribution rate constant is used when transfer between central to peripheral. Central is 1 and peripheral is 2. Complete the equation for distribution rate contstant:
k12 = (\_\_\_\_+Bα)/(\_\_\_+B) K21 = A+B - \_\_\_\_ - (\_\_\_/k21)
k21 = (Aβ+Bα)/(A+B)
This is peripheral to central
K12 = A+B - k21 - (αβ/k21)
This is central to peripheral
