ABSTRACT
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 mg= 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 permea-
bility, are generally poor drug candidates (unless the dose is very low).
