Overview of factors affecting oral drug absorption

This article provides an overview of variables that can affect drug absorption following oral administration in recent years, including both physicochemical properties of the drug and physiological factors of the body. The oral absorption of a drug is a complex process depending upon these factors and their interactions with each other. Solubility and permeability are considered as the major physicochemical factor that affect the rate and extent of oral drug absorption, moreover other physicochemical properties always show their effects to drug absorption via affecting solubility and permeability. In this regard, the Biopharmaceutics Classification System is proved to be a successful predictive tool for drug development. Oral drug bioavailability can also be markedly influenced by physiological factors, such as gastrointestinal pH, gastric emptying, small intestinal transit time, bile salt, absorption mechanism and so on. Thus by understanding the physicochemical properties of a compound and by recognizing the physiological processe affecting drug absorption, also with the awareness of a drug's BCS characteristics, pharmaceutical scientists can better predict drug absorption and develop formulations that can maximize drug bioavailability.