Systemic Versus Local Bioavailability Enabled by Recycling

Bioavailability describes the rate and the extent of administrated drug that reaches the systemic circulation. It also determines the in vivo exposure of a drug, which is associated with drug efficacy. There are many factors influencing bioavailability, including physiological processes. One of them is enterohepatic recycling (EHR). It enables the recycling in the digestive system (intestine–liver). In this chapter, we will discuss systemic and local gut bioavailability followed by the introduction of two different types of EHR that change the bioavailability and their potential clinical significance.