Schematic of the ACAT model

The CAT model presupposes that dissolution is instantaneous and therefore the kinetics of the permeation step control the gastrointestinal absorption of drug. This is reflected in the previous equation, which indicates that the effective permeability is the sole parameter controlling the intestinal absorption of highly soluble drugs. 

Due to its compartmental nature, the CAT model can be easily coupled with the disposition of drug in the body using classical pharmacokinetic modeling. In this respect the CAT model has been used to interpret the saturable small-intestinal absorption of cefatrizine in humans [175]. 

The use of convection-dispersion models in oral drug absorption was first proposed in the early 1980s [177, 178]. The small intestine is considered a 1- 

By replacing the spatial coordinate z with the length of the tube L in the previous equation, the fraction of dose exiting the small intestine as a function of time is obtained  

---

Figure 6.4 Schematic of the ACAT model. Reprinted from [176] with permission from Elsevier.

---