ABSTRACT
INTRALUMENAL SOLUBILITY AND DRUG ABSORPTION For uptake via the intestinal epithelium to be possible, the drug must be in solution. In most cases, drug absorption takes place in the small intestine and, therefore, the drug concentration achieved in this region is of primary importance. However, the release and dissolution of drug may also be important in other regions of the gastrointestinal (GI) lumen. For example, dissolution in the stomach will affect drug concentrations in the small intestine and, if rapid, will facilitate a fast onset of the therapeutic action. For products that act locally in the colon, the dissolution in that region will dictate the rate and extent of the clinical outcome. Drug dissolution in vivo is difficult to assess, at least on a routine basis (1). Biorelevant dissolution is a useful alternative, but issues relating mainly to hydrodynamics (type and intensity of agitation and volumes) still remain (see chap. 12, this volume).
