Other methods of comparing bioavailabilities will be discussed in a later section.

A great deal can be learned about the absorption process by applying equations (40) and (41) to plasma concentration versus time data. Since there is no model assumption with regard to the absorption process, the calculated values of At/Vd can often be manipulated to determine the kinetic mechanism that controls absorption. This is best illustrated by an example.

Example. A tablet containing 100 mg of a drug was administered to a healthy volunteer and the plasma concentration (Cp) versus time data shown in Table 6 were obtained. Figure 9 shows a semilogarithmic plot of these Cp versus time data. The halflife for elimination of the drug can be estimated from the straight line "tail" of the plot to be 4.7 hours. The overall elimination rate constant is then kel

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