B- The direct linear plot

This is a graphical method for the determination of the pharmacokinetic parameters. This method requires knowing two different s.s. conc during the administration of two different dosing regimens.

100
200
300
Dosing rate
mg/day
The left side of the x-axis is used to draw the s.s. drug conc
The y-axis is used to draw the dosing rate
100
200
300
Dosing rate
mg/day
Km

Vmax

F
Note that, if the two lines do not
intersect, this means that steady state
cannot be achieved such as
when the dose exceeds Vmax.

1- Draw the line that goes through the first dose and the corresponding s.s. conc.

2- Draw the line that goes through the second dose and the corresponding s.s. conc.

3- The x-coordinate of the point where the two lines meet is equal to Km.

4- The y-coordinate of the point where the two lines meet is equal to Vmax/F.