国生 Other factors 国生 Other factors Drug-food and drug-drug interactions .Drug absorption is generally less efficient when food present in Disease states:Gastrointestinal disorders and disease the GIT,although there are several exceptions. states are likely to influence drug absorption. .1.delay in gastric emptying Age:pediatric and geriatric population 2.stimulation of bile flow, 3.a change in the pH of the Gl tract; .4.an increase in splanchnic blood flow, .5.a change in luminal metabolism of the drug substance; .6.physical or chemical interaction of the meal with the drug product or drug substance. 国丛生 Other factors 国生 Absorption-Learning objectives ®Metabolism Metabolism by enzymes Concept of absorption Acid-or base-mediated drug breakdown Mechanism of absorption Anatomical structure of GIT Variables which affect absorption Diffusion model/Nernst-Bruner equation Fluid mosaic model/Fick's first law Blood flow/First-pass effect ④Sink condition 圈上达线一 Other factors-Metabolism ©Metabolism ·First-pass effect首过效应：An absorbed drug will first go to the liver,which is the primary site of drug metabolism in the body, the drug may be metabolized extensively before systemie distribution. .First-pass effect refers to all processes of metabolism before the drug reaches the systemic circulation,which take place primarily in the gut and liver. 1010 Shanghai Jiao Tong University Other factors Drug-food and drug-drug interactions • Drug absorption is generally less efficient when food present in the GIT, although there are several exceptions. • 1. delay in gastric emptying; • 2. stimulation of bile flow; • 3. a change in the pH of the GI tract; • 4. an increase in splanchnic blood flow; • 5. a change in luminal metabolism of the drug substance; • 6. physical or chemical interaction of the meal with the drug product or drug substance. Shanghai Jiao Tong University Other factors Metabolism • Metabolism by enzymes • Acid- or base-mediated drug breakdown Shanghai Jiao Tong University Other factors-Metabolism Metabolism • First-pass effect首过效应: An absorbed drug will first go to the liver, which is the primary site of drug metabolism in the body; the drug may be metabolized extensively before systemic distribution. • First-pass effect refers to all processes of metabolism before the drug reaches the systemic circulation, which take place primarily in the gut and liver. Shanghai Jiao Tong University Other factors Disease states: Gastrointestinal disorders and disease states are likely to influence drug absorption. Age: pediatric and geriatric population Shanghai Jiao Tong University Absorption- Learning objectives Concept of absorption Mechanism of absorption Anatomical structure of GIT Variables which affect absorption Diffusion model/Nernst-Bruner equation Fluid mosaic model/Fick’s first law Blood flow/First-pass effect Sink condition