Abstract
A comprehensive analytical solution that accounts for many factors and assumptions affecting drug concentration profile in the gastrointestinal tract was presented. A sensitivity analysis approach was utilized in order to investigate the importance of different parameters in the model. The partition coefficient is found to be the key parameter. Hence, for drugs stable in the intestinal wall, increasing partition coefficient only can lead to higher drug absorption. However, for drugs unstable in the intestinal wall, increasing partition coefficient and diffusivity is needed to counteract drug instability. On the other hand, the model is essentially insensitive to degradation in the intestinal lumen for degradation half lives greater than 0.7 min at a given intestinal length. However, a high model sensitivity to the rate of luminal degradation is obtained at higher intestinal length values. The proposed model can be used as a guide for oral drug delivery.