PHAR 4634 - Chapter 8 Page 4

## Absorption rate constant, ka

Figure VIII-5, Linear Plot of Cp versus Time with ka = 3, 0.6, or 0.125 hr sup>-1

Before going on to calculate the parameters ka, kel, and F from data provided we can look at the effect different values of F and ka have on the plasma concentration versus time curve.

tpeak = 1, 2.75, 6.25 hour.

Notice that with higher values of ka the peak plasma concentrations are higher and earlier.

## Extent of absorption, F

Figure VIII-6, Linear Plot of Cp versus Time with F = 1, 0.66, or 0.33

Changing F values is equivalent to changing the dose. Thus the higher the F value the higher the concentration values at each time point. Since the values of kel and ka are unchanged the time of peak plasma concentration is unchanged.

Thus, tpeak = 1, 1, and 1 hour. The same in each case.

A HypercardTM Stack for exploring Oral Administration calculations is available.
Fourth Homework Set 1995
For practice try graphing linear or semi-log plots of drug concentration after a single oral dose.