ABSTRACT
INTRODUCTION The gastrointestinal (GI) tract is designed to make sure that the body gets the maximal benefit out of nutrients in the ingested food. Themain role of theGI tract is to digest foodstuffs and absorb nutrients, vitamins, and electrolytes, while at the same time to exclude andmetabolize ingested xenobiotics that could be potentially harmful. Intake of ameal induces awhole range of changes in theGI tractmediated by physical, nervous, and endocrine pathways. These changes include (i) increased volume due to GI secretions, (ii) increased gastric residence time, (iii) increased peristaltic movements, (iv) changes in gastric and intestinal pH, (v) further changes in luminal composition due to secretion of bile and pancreatic fluids, (vi) alterations in luminal metabolism, (vii) and increased perfusion of the GI mucosa and the liver. Many of these changes can impact the absorption and pharmacokinetics of drugs. The mechanisms behind this are manifold and depend on the physicochemical characteristics of the drug as well as the physiological changes.
