圈ft一Gastric emptying-nthe absencoffoo 国生一 Gastric emptying The gastric residence time of a solid dosage form will An increased gastric-emptying rate will vary from perhaps 5 to 15 minutes if ingested at the probably increase the rate of absorption for beginning of the housekeeper to about 2 hours or longer if drugs absorbed by passive diffusion. ingested at the end of the housekeeper. An increased gastric-emptying rate will The foregoing considerations will not apply to liquid probably decrease the extent of absorption for dosage forms which are generally able to empty during all phases of the migrating motor complex. drugs absorbed by active transport. Gastric emptying-in the presence of food 国生 Physiological factors Components and properties of GI fluids. In the presence of food,gastric emptying is ©Gastric emptying controlled by a complex variety of mechanical, Intestinal transit hormonal,and neural mechanisms ©Blood flow 圈生一 Physiological factors-Gastric emptying ④生Physiological factors-nestne transit The longer the residence time in the small intestine,the The factors affecting stomach emptying greater the potential for complete absorption. 国Food Once emptied from the stomach,material will move along 国Drug the small intestine and reach the ileocecal valve in about 3 ©Sickness hours. ©Others The short time in small intestine is critical to the ·Body position performance of poorly water-soluble drugs,slowly ·Viscosity dissolving,coated dosage forms(enteric or polymer coated), .Emotional state..... and sustained-release forms. 88 Shanghai Jiao Tong University Gastric emptying-in the absence of food The gastric residence time of a solid dosage form will vary from perhaps 5 to 15 minutes if ingested at the beginning of the housekeeper to about 2 hours or longer if ingested at the end of the housekeeper. The foregoing considerations will not apply to liquid dosage forms which are generally able to empty during all phases of the migrating motor complex. Shanghai Jiao Tong University Gastric emptying-in the presence of food In the presence of food, gastric emptying is controlled by a complex variety of mechanical, hormonal, and neural mechanisms. Shanghai Jiao Tong University Physiological factors-Gastric emptying The factors affecting stomach emptying Food Drug Sickness Others • Body position • Viscosity • Emotional state…… Shanghai Jiao Tong University Gastric emptying An increased gastric-emptying rate will probably increase the rate of absorption for drugs absorbed by passive diffusion. An increased gastric-emptying rate will probably decrease the extent of absorption for drugs absorbed by active transport. Shanghai Jiao Tong University Physiological factors Components and properties of GI fluids. Gastric emptying Intestinal transit Blood flow Shanghai Jiao Tong University Physiological factors-Intestine transit The longer the residence time in the small intestine, the greater the potential for complete absorption. Once emptied from the stomach, material will move along the small intestine and reach the ileocecal valve in about 3 hours. The short time in small intestine is critical to the performance of poorly water-soluble drugs, slowly dissolving, coated dosage forms (enteric or polymer coated), and sustained-release forms