Selection of excipients based on the biopharmaceutics classification system of drugs

Active agents have been considered the main ingredients of any therapeutic product since the early ages of formulation technology. However, the importance of the inactive ingredients has been realized during the last three decades. With the development and manufacturing of more intelligent and multifunction excipients, new ways became available for formulation technologists to increase the beneficial effects of drugs on human body. Many modern active agents have internal characteristics that significantly decrease their potential and theoretical bioavailability; however, today we have the widest variety of inactive ingredients that we can utilize in order to change these properties. The careful and educated selection of excipients might significantly influence the effect of the drugs, including hastening or delaying their onset of action, increasing their bioavailability by changing their physicochemical characteristics, and increasing their stability. In this chapter, we focus primarily on the factors determining and influencing bioavailability as well as the selection of excipients for formulating new dosage forms wiThenhanced therapeutic efficacy, based on the physicochemical properties of drugs. We will provide some examples from the scientific literature to demonstrate the achievements in this multidisciplinary area.