Physiological Factors Affecting Drug Release and Absorption in the

INTRODUCTION In vivo drug release from oral drug formulations may be affected by a number of physiological factors including volume and composition of gastrointestinal (GI) fluids, the pH and buffer capacity of these fluids, digestive enzymes, contraction patterns, and bacterial flora in the gut. In addition, the extent of drug absorption and bioavailability may be further affected by GI transit, the presence of cellular transporters, and metabolic enzymes.