Diagram XIX-2 Scheme for Oral Two-Compartment Pharmacokinetic Model
The model is shown in Diagram XIX-2:
Differential equation
Cp = A.e-alpha.t + B.e-beta.t + C.e-ka.t
where A + B + C = 0
Integrated Equation
Figure XIX-13 Semi-Log Plot Showing Pronounced Distribution
Bioavailability calculations
are the same as for the one compartment model, i.e., by comparison of AUC or
U
. These apply for any linear system. Also if
, 
, and ka are sufficiently separated the method of residuals
can be applied to determine the three values.
Figure XIX-14 Semi-Log Plot Without Distribution Phase Evident
The
equation can also be used to calculate appropriate dosing regimens. For example
if an average plasma concentration of 20 mg/L is required and V1 = 15 L, kel =
0.15 hr-1,
F = 0.9 and a dosing interval of 12 hours is to be used then the required dose
is:-
= 600 mg every 12 hours
Copyright 2001 David W.A. Bourne