A patient is started on a drug at an oral dose of 75 mg at time zero, 50 mg at 6 hours and 75 mg at 12 hours (makes no sense but a nice random regimen :- all times are from time zero). Calculate the drug concentration at a few of time points during the first three dosing interval. Graph these data on semi-log graph paper (The graph is not required for this homework exercise). Specifically calculate the concentration three hours after the first dose, two hours after the second dose and one hour after the third dose.
Assume a one compartment linear model applies to this drug in this concentration range. For this dosage form and patient the bioavailability is 1 and the absorption rate constant is 1.58
The half-life and V for this drug in this patient are 2.2 hr and 33.5 L, respectively.

The equation:

Equation 26.5.1 Drug Concentration during a Multiple Dose Regimen (Non-Uniform Regimen)