Absorption biopharmaceutics classification system

Fig. 12 Illustration of the Biopharmaceutical Classification System (BCS), which classifies drug absorption potential on the basis of aqueous solubility or membrane permeability. (Copyright 2000 Saguaro Technical Press, Inc., used with permission.)...

AC ADME ANS AUC BA/BE BBB BBM BBLM BCS BLM BSA CE CHO CMC CPC CPZ CTAB CV DA DOPC DPPC DPPH aminocoumarin absorption, distribution, metabolism, excretion anilinonaphthalenesulfonic acid area under the curve bioavailability-bioequivalence blood-brain barrier brush-border membrane brush-border lipid membrane biopharmaceutics classification system black lipid membrane bovine serum albumin capillary electrophoresis caroboxaldehyde critical micelle concentration centrifugal partition chromatography chlorpromazine cetyltrimethylammonium bromide cyclic votammetry dodecylcarboxylic acid dioleylphosphatidylcholine dipalmitoylphosphatidylcholine diphenylpicrylhydrazyl... 

Fig. 7.5. The Biopharmaceutics Classification System (BCS) provides a scientific basis for predicting intestinal drug absorption and for identifying the rate-limiting step based on primary biopharmaceutical properties such as solubility and effective intestinal permeability (Pefr). BCS serves as a product control instrument. The BCS divides drugs into four different classes based on their solubility and...

The example of amprenavir, an HIV-1 protease inhibitor, shows that intestinal metabolism can also be used as a strategy to enhance the bioavailability of compounds. In the biopharmaceutics classification system (BCS), amprenavir can be categorized as a class II compound it is poorly soluble but highly permeable [51]. Fosamprenavir, the water-soluble phosphate salt of amprenavir, on the other hand, shows poor transepithelial transport. However, after oral administration of fosamprenavir, this compound is metabolized into amprenavir in the intestinal lumen and in the enterocytes mainly by alkaline phosphatases, resulting in an increased intestinal absorption [51, 174],... 

Volpe DA, Moller H, Yu LX (2002) Regulatory acceptance of in vitro permeability studies in the context of the biopharmaceutics classification system. In Lehr CM (ed.) Cell Culture Models of Biological Barriers In Vitro Test Systems for Drug Absorption and Delivery. Taylor Francis Publishing Group, London New York, pp. 130-139. 

Since solubility and permeability are the two most important factors influencing oral absorption of drugs, the following biopharmaceutical classification system (BCS) for drug substances, based on the work by Amidon et al.,67 has been recommended by the FDA 68... 

Following oral administration, dissolution of the drug molecule in the intestinal milieu is a prerequisite for the absorption process. According to the Biopharmaceutical Classification System (BCS) [2], poor water-soluble compounds (i.e., aqueous solubility less than 100 pg/ mL) are class 2 or class 4 compounds. For class 2 compounds, the absorption level is dictated by the dissolution properties of the molecule in the gastrointestinal (GI) fluids. BCS class 4 compounds, which are characterized by both low solubility and poor intestinal wall permeability, are generally poor drug candidates (unless the dose is very low). 

The last section of this chapter is devoted to the regulatory aspects of oral drug absorption and in particular to the biopharmaceutics classification system and the relevant FDA guideline. At the very end of the chapter, we mention the difference between randomness and chaotic behavior as sources of the variability encountered in bioavailability and bioequivalence studies. 

Next to permeability, aqueous solubility is the most important biopharmaceutical property associated with oral drug absorption. These two properties have established the basis for a biopharmaceutical classification system (BCS) and have become the subject of an FDA guidance entitled Waiver of In Vivo Bioavailability and Bioequivalence Studies for Immediate-Release Solid Oral Dosage Forms Based on a... 

Figure 3.1 The Biopharmaceutics Classification System as defined by Amidon et al. [6]. The BCS is a classification of drug substances according to their solubility and permeability properties, in orderto stand forthe most fundamental viewofthe drug intestinal absorption process following oral administration.

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