Physiologically Based Finite Time Pharmacokinetic (PBFTPK) Models: Inception and Development

Oral drug absorption has always been modeled as a first-order process that lasts indefinitely. Since common knowledge takes for granted that this is not so, the concept of Finite Absorption Time (FAT) was introduced recently and relevant models were generated for one- and two-compartment disposition in conjunction with zero-order absorption kinetics. This chapter justifies these choices by considering all possible classes of drugs based on the BCS classification system. It also presents simulations to show accessible variability as well as successful fits to the pharmacokinetic data of several orally administered drugs.