Submit Manuscript | http://medcraveonline.com Abbreviations: BDDCS, biopharmaceutics drug disposition classifcation system; IR, immediate release; BCS, biopharmaceuti- cal classifcation system; BA, bioavailability; BE, bioequivalence; QBCS, quantitative biopharmaceutical classifcation system Introduction The Biopharmaceutical Classifcation System (BCS) has increases the applicability and validity of drug solubility and permeability in terms of research. 1,2 It is now well clear that drug absorption dependent on bioavailability and bioequivalence during the drug development process provided by U. S. Food & Drug Administration. 3 The Biopharmaceutical classifcation system (BCS) is cogent tool for decision making during the phases of early drug development. 4 The BCS was frst devised in 1995 and became a standard in the regulation of bioequivalence of oral dosage forms. 5,6 The BCS is a scientifc framework that classifes a drug substance based on two parameters a. Aqueous solubility b. Intestinal permeability. 6 If the absorption of the drug substance is permeation rate limited, the solubility of the drug substance will not be a governing parameter and so the in vitro dissolution study can be used to demonstrate the bioavailability (BA) or bioequivalence (BE) of the drug product through in vitro – in vivo correlation (IV–IVC). 1,7 In BCS, each class has particularly designated rate–limiting step with possibilities for its modifcation so that the formulator can select and optimize a specifc dosage form for the drug substance belonging to a particular class of BCS. 8,9 Here we are mainly focusing on some of the new concepts of BCS. Extension to BCS Six class biopharmaceutical classifcation system Bergstrom and co–workers have dividing the drugs into six classes considering solubility, permeability and calculated surface area which is the modifed version of the BCS. The solubility was allotted as “high” or “low” and the permeability was classifed as “low”, “intermediate,” or “high”. The non–polar portion of surface area of the molecule terminated in good permeability predictions. It is well suited for early development especially for optimization of the pharmacokinetic parameters. 10 Quantitative biopharmaceutical classifcation system (QBCS) Apart from solubility of drug in the dissolution fuid dissolution can be dependent on the amount of drug present at the site of absorption (dose) considering this fact the quantitative BCS (QBCS) was designed by Rinaki and Co–workers. The classifcation was based on the solubility: dose ratio as main parameter. According to FDA guidance for the industry, August 2000, the highest dose strength of an immediate release product should be considered for study. 11 The QBCS relies on a permeability and dose/solubility ratio. Permeability estimates, (P app that is the apparent permeability) were derived from Caco–2 cell studies and a constant intestinal volume content of 250ml was used to express the dose solubility ratio as a dimensionless quantity (q) (Table 1). Papp is the apparent permeability coeffcient, which is the ratio of fux to concentration of drug in the donor compartment. Hence from it in–vitro tissue model can be used to predict in–vivo data. Apart from this the chiral conversion of the drug in the body is also considered by Gohel MC and Co–workers and gives Chirality based classifcation as given in Table 2. Biopharmaceutics drug disposition classifcation sys- tem (BDDCS) 12,13 Chi Yuan Wu 13 and co–workers in the 2005 proposed BDDCS considering factors like effux transporters, food, absorptive transporters and renal or biliary routes of elimination on drug absorption and bioavailability. In the BDDCS, permeability is replaced by extent of metabolism and drugs are classifed on the base of solubility and extent of metabolism. According to classifcation, if the drug is mainly eliminated by metabolism, then the drugs show high permeability. If the drug is mainly eliminated as unchanged drug by biliary or renal route, then the drugs show low permeability. Formerly, “Extensive metabolism” was defned as ≥50% metabolism of an oral dose in humans in vivo but now “extensive metabolism” MOJ Bioequiv Availab. 2017;3(4):108‒109 108 © 2017 Chavda et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Biological classifcation system (BCS); with a new perspective Volume 3 Issue 4 - 2017 Vivek P Chavda, Moinuddin Soniwala Department of Pharmaceutics, BK Mody Government Pharmacy College, India Correspondence: Vivek P Chavda, Department of Pharmaceutics, BK Mody Government Pharmacy College, Near Ajidem, Rajkot–Bhavnagar highway, Gujarat Technological University, Rajkot–360003, Gujarat, India, Fax 0281 2384 279, Email vivek7chavda@gmail.com Received: June 03, 2017 | Published: July 25, 2017 Abstract Biopharmaceutical classification system (BCS) is a drug development tool that is based on correlation of solubility with their bioavailability in human body and allows estimation of the contributions of three major factors, dissolution, solubility, and intestinal permeability, which affect oral drug absorption from immediate release (IR) solid oral products. This mini review gives an overview of BCS with special emphasis on concept, classification, extension and Biopharmaceutics drug disposition classification system (BDDCS) with brief idea on its applications. Keywords: biopharmaceutical classification system, solubility, bioavailability, intestinal permeability, bioequivalence, product development, BDDCS MOJ Bioequivalence & Bioavailability Mini Review Open Access