For example, calculate drug concentration at 24 hours after the first dose of 200 mg. The second dose of 300 mg was given at 6 hours and the third dose of 100 mg at 18 hours.
Graphically, this will look like the results in the figure below:
Figure XV-4 Drug Concentration after Three IV Bolus Doses
A small Excel spreadsheet illustrating the superposition principle
Dosing three times a day may be interpreted as with meals, the plasma concentration may then look like the plot in Figure 60. The ratio between Cpmax and Cpmin is seven fold (8.2/1.1 = 7.45) in this example.
Figure XV-5 Cp versus Time during Dosing at 8 am, 1 pm, and 7 pm
However this regimen may be acceptable if
1) the drug has a wide therapeutic index
2) there is no therapeutic disadvantage to low overnight plasma concentrations, e.g., analgesic of patient stays asleep.
Copyright 2001 David W.A. Bourne