ABSTRACT
Biopharmaceutics classification system is a classification theory based on the solubility and permeability of drugs. Besides its application in in vitro-in vivo correlation studies, it also plays an important role in understanding the properties of drugs, especially in the drug development and evaluation. Nowadays, the definition and classification criteria of BCSs are not unified, therefore the classifications of drugs vary in different data sources, which resulting in confusion in understanding of the properties of drugs and use of BCS data. In this review, we compared the BCSs adopted by three authoritative official agencies ie, FDA, WHO and EMA, and two unofficial organization/enterprise ie, FIP and TSRL company. The problems in the use of BCS were also discussed, which will be helpful to use BCS data more correction and effectively.