View source for Biopharmaceutics Classification System

{{for|other uses of the abbreviation '''BCS'''|BCS (disambiguation)}}
The '''Biopharmaceutics Classification System''' is a guidance for predicting the [[gastrointestinal tract|intestinal]] [[drug]] absorption provided by the [[U.S. Food and Drug Administration ]][http://www.fda.gov/]. The fundamental basis for the BCS was established by Dr. Gordon Amidon who was presented with a Distinguished Science Award at the August 2006 International Pharmaceutical Federation (FIP) congress in Salvador, Brazil.{{Fact|date=February 2007}}

This system allows to restrict the prediction using the parameters [[solubility]] and [[intestinal permeability]]. The [[solubility]] classification is based on a [[United States Pharmacopoeia]] (USP) aperture. The [[intestinal permeability]] classification is based on a comparison to the [[Route of administration|intravenous injection]]. All those factors are highly important, since 85% of the most sold drugs in the [[USA]] and [[Europe]] are [[route of administration|orally administered]].

According to the Biopharmaceutics Classification System, drug substances are classified as follows:

*'''Class I - High [[intestinal permeability|Permeability]], High [[Solubility]] '''
** Example: [[Metoprolol]]
** Those compounds are well absorbed and their absorption rate is usually higher than excretion. 
*'''Class II - High [[intestinal permeability|Permeability]], Low [[Solubility]] '''
** Example: [[Glibenclamide]]
** The [[bioavailability]] of those products is limited by their solvation rate. A correlation between the [[in vivo]] [[bioavailability]] and the [[in vitro]] solvation can be found.
*'''Class III - Low [[intestinal permeability|Permeability]], High [[Solubility]] '''
** Example: [[Cimetidine]]
** The absorption is limited by the permeation rate but the drug is solvated very fast. If the formulation does not change the permeability or gastro-intestinal duration time, then class I criteria can be applied.
*'''Class IV - Low [[intestinal permeability|Permeability]], Low [[Solubility]] '''
** Example: [[Hydrochlorothiazide]]
** Those compounds have a poor [[bioavailability]]. Usually they are not well absorbed over the intestinal mucosa and a high variability is expected.
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The drugs are classified in BCS on the basis of following parameters:
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1. Solubility
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2. Permeability
<br />
3. dissolution
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The class boundaries for these parameters are:
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'''1.	Solubility class boundaries'''- It is based on the highest dose strength of an immediate release product. A drug is considered highly soluble when the highest dose strength is soluble in 250ml or less of aqueous media over the ph range of 1 to 7.5. The volume estimate of 250ml is derived from typical bioequivalence study protocols that prescribe administration of a drug product to fasting human volunteers with a glass of water.
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'''2.	Permeability class boundaries-''' It is based indirectly on the extent of absorption of a drug substance in humans and directly on the measurement of rates of mass transfer across human intestinal membrane. Alternatively non-human systems capable of prediction the drug absorption systems capable of predicting the drug absorption in humans can be used (such as in-vitro culture methods). 
A drug substance is considered highly permeable when the extent of absorption in humans is determined to be 90 % or more of the administered dose based on a mass-balance determination or in comparison to and intravenous dose.
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'''3.  Dissolution class boundaries-''' An immediate release products is considered rapidly dissolving when no less than 85% of the labeled amount of the drug substance dissolve within 30 minutes using USP Dissolution Apparatus 1 at 100 RPM or Apparatus 2 at 50 RPM in a volume of 900ml or less in following media,) 0.1 N HCl or simulated gastric fluid or pH 4.5 buffer and pH 6.8 buffer or simulated intestinal fluid.
 


==See also==
*[[ADME]]
**[[Partition coefficient]]
**[[Bioavailability]]
**[[Drug metabolism]]
**[[First pass effect]]
*[[Polar surface area]]
*[[IVIVC]]

==References==
* H. Waterbeemd, H. Lennernäs, P. Artursson (editors), ''Drug bioavailability: estimation of solubility, permeability, absorption and bioavailability'', Wiley-VCH, Weinheim, Germany, '''2003'''. ISBN 3-527-30438-X
<br />
* Amidon, G. L.; Lennernas, H.; Shah, V. P.; Crison, J. R. (1995). A Theoretical Basis for a
Biopharmaceutic Drug Classification: The Correlation of In Vitro Drug Product Dissolution
and In Vivo Bioavailability. Pharm. Res. 12: 413–420.

==External links==
* [http://www.fda.gov/AboutFDA/CentersOffices/CDER/ucm128219.htm BCS guidance] of the [[U.S. Food and Drug Administration]]
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[[Category:Pharmacology]]
[[Category:Pharmacy]]

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[[pl:System klasyfikacji biofarmaceutycznej]]
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