Both BCS and BDDCS use solubility as one of the two classification criteria. The purpose of BDDCS is to predict drug disposition and potential drug-drug interactions in the intestine and the liver, and potentially the kidney and brain. The purpose of BCS is to characterize drugs for which products of those drugs may be eligible for a biowaiver of in vivo bioequivalence studies. The major differences between BCS and BDDCS relate to their purpose and the measurement for classification as depicted in Table 1. They proposed that a biopharmaceutics drug disposition classification system (BDDCS) could serve as a basis for predicting the importance of transporters in determining drug disposition, as well as in predicting drug-drug interactions. In 2005, Wu and Benet 3 recognized that for drugs exhibiting high intestinal permeability rates the major route of elimination in humans was via metabolism, while drugs exhibiting poor intestinal permeability rates were primarily eliminated in humans as unchanged drug in the urine and bile. The objective of the BCS is to predict in vivo performance of drug products from in vitro measurements of permeability and solubility. The FDA’s Biopharmaceutics Classification System(BCS) 1 is based on the work of Amidon and coworkers 2 with the core idea being that in vitro methodology, centrally embracing permeability and solubility, with qualifications related to pH and dissolution, may qualify drug products for a waiver of in vivo bioequivalence studies.