Biopharmaceutics Classification System

Biopharmaceutics Classification System (BCS) is a regulatory mechanism through which drug developers and generic companies can obtain a waiver of clinical bioequivalence studies, also called a biowaiver. According to the 2000 FDA BCS Guidance, compounds that are classified as Class I (highly soluble, highly permeable) are eligible for BCS biowaivers. For such compounds, the rate and extent of drug absorption is unlikely to be affected by drug dissolution and/or GI residence time, and in vivo bioequivalence studies (for new formulations, etc.) may be waived based on in vitro permeability and solubility data.

BCS Divides Compounds into Four Categories:

Class I – High Solubility, High Permeability
Class II – Low Solubility, High Permeability
Class III – High Solubility, Low Permeability
Class IV – Low Solubility, Low Permeability

Furthermore, for Class I compounds, it is unlikely that absorption will be limited by efflux transporters. Thus, it may be possible to waive clinical DDI studies as well.“If in vitro experiments demonstrate that an NME is a P-gp substrate, additional drug-specific factors may be considered before determining whether an in vivo drug interaction study is warranted. For example, the bioavailability of the BCS Class I or BDDCS Class I NMEs that are highly soluble, highly permeable, and highly metabolized may not be significantly affected by a co-administered drug that is a P-gp inhibitor, and thus, an in vivo interaction study may not be needed.”

— L. Zhang et al., “Predicting Drug-Drug Interactions: An FDA Perspective” (2009) The AAPS Journal

Absorption Systems, World Leader in Biopharmaceutics Classification System

Absorption Systems has performed dozens of BCS classification studies over the past ten years, many of which have resulted in successful BCS biowaiver submissions. Eight of the ten largest generic drug companies have conducted in vitro BCS biowaiver studies with Absorption Systems. It was our permeability data that supported some of the very first in vitro BCS biowaivers.

Our extensive experience continues to facilitate innovative solutions and enable in vitro classification for a broader range of drugs. This, combined with our 10-day turnaround for pre-qualification and our cost effective designs, saves you time and money. Just a few reasons why Absorption Systems averages more than 30 BCS studies each year.


Avoid expensive and time consuming clinical bioequivalence studies with in vitrosolubility, permeability, and dissolution data. It is a critical optimizer in time and money for drug developers.

Biowaiver Absorption SystemsOur validated 3-step study design allows for early identification of BCS biowaiver candidates and optimization of protocol elements. These steps include:

  1. Pre-qualification and determination of the eligibility of test compound for BCS biowaiver – your go/no-go decision point
  2. Protocol optimization and conduct of FDA-required experiments to establish protocol for pivotal studies
  3. GLP BCS classification of permeability and/or solubility

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