Equation 9.2.1 Cp versus Time after Oral Administration
return to the Course index
previous | next
Equation 9.2.1 Cp versus Time after Oral Administration
this can be written as
Equation 9.2.2 Simplified Equation for Cp versus Time
Equation 9.2.3 The Intercept, A
Figure 9.2.1 Semi-log plot of Cp versus Time after Oral Administration
Click on the figure to view the interactive graph
The equation for this straight line portion can be obtained from the equation for Cp by setting the faster term (usually e-ka • t) to zero:
Figure 9.2.2 Semi-log Plot of Cp versus Time Showing Cplate, Slope, and Intercept
then
Equation 9.2.4 Cplate versus Time
and plotting Cplate versus time gives a straight line on semi-log graph paper, with a slope (ln) = -kel and intercept = A.
Now looking at the equation for Cp versus time again.
Equation 9.2.5 Cp versus Time including Cplate
therefore
Equation 9.2.6 Difference or Residual versus Time
Plotting the ln (Residual) versus time should give another straight line graph with a slope (ln) equal to - ka and the same intercept as before, i.e. A
Equation 9.2.7 ln(Residual) versus Time
Figure 9.2.3 Semi-log of Plot of Residual versus Time
This is the method of residuals or "feathering".
It can give quite accurate values of kel, ka, and V/F if :
i) one rate constant is at least five times larger than the other
and
ii) both absorption and elimination are first order processes.
| Time (hr) | Plasma Concentration (mg/L) | Cp(late) (mg/L) | Residual [Col3 - Col2] (mg/L) |
| 0.25 | 1.91 | 5.23 | 3.32 |
| 0.5 | 2.98 | 4.98 | 2.00 |
| 0.75 | 3.54 | 4.73 | 1.19 |
| 1.0 | 3.80 | 4.50 | 0.70 |
| 1.5 | 3.84 | 4.07 | 0.23 |
| 2.0 | 3.62 | 3.69 | 0.07 |
| 3.0 | 3.04 | ||
| 4.0 | 2.49 | ||
| 5.0 | 2.04 | Residual = 5.5 * e -2.05 * t | |
| 6.0 | 1.67 | Cplate = 5.5 * e -0.2 * t | |
| 7.0 | 1.37 |
Figure 9.2.4 Figure Illustrating the Method of Residuals
Figure 9.2.5. Concentration versus time after oral administration. Method of residuals
Click on the figure to view the interactive graph
return to the Course index
previous | next
Material on this website should be used for Educational or Self-Study Purposes Only
Copyright © 2001 - 2025 David W. A. Bourne (david@boomer.org)
 | An iPhone app that facilitates the geotagging of Bird Count stops and the return to the same stops during the next and subsequent Bird Count sessions |
 |