Biopharmaceutics Classification System

The Biopharmaceutics Classification System is a guide for predicting the intestinal drug absorption provided by the U.S. Food and Drug Administration . 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.

This system restricts 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 intravenous injection. All those factors are highly important, since 85% of the most sold drugs in the USA and Europe are orally administered.

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

• Class I - high permeability, high solubility
• Example: metoprolol
• Those compounds are well absorbed and their absorption rate is usually higher than excretion.
• Class II - high 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 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......
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