This graphical method can be used to estimate the steady state plasma conc achieved after administration of a certain dose and also to estimate the dose required to achieve a specific plasma conc.

1- What is the s.s. conc achieved after administration of 200 mg/day ?

Draw the line between the 200 mg dose on the y-axis, and the point where the two (dose-conc) lines intersect. Back extrapolate to meet the x-axis. The point of intersection on the x-axis is the expected s.s. conc.

2- What is the dose required to achieve s.s. conc of 10 mg/L ?

Draw the line between the s.s. conc of 10 mg/L and the point where the two (dose-conc) lines intersect. The point of intersection on the y-axis is the dose that will achieve s.s. conc of 10 mg/L.