Topic 4: Residence Time

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Topic 4 Residence Time

• Role of Stomach
• Role of Intestine
• Amount of Drug Absorption
• Percent of Drug Absorption

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Role of Stomach in Drug Delivery

• Structure of Stomach
• Absorption Pathway
• Drug Delivery Devices

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Structure of Stomach
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Structure of Stomach
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Structure of Stomach
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Structure of Stomach
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Structure of Stomach
Surface Cells Neck Mucous Cells G Cells Peptic
(Chief) cells Parietal Cells
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Gastric Pit
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Functions of StomachOrgan Function

• Reservoir
• Emptying
• Mixing and Homogenizing
• Size Restriction

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Functions of Stomach Epithelial Cells

• Mucous Mucous HCO3-
• Parietal Intrinsic Factor, H
• Peptic (Chief) pepsinogen lt-gtpepsin
• G-Cells Gastric juices

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Functions of StomachFluid Secretion

• Thought of Food
• Ingestion of Food and Detention of Stomach

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Functions of StomachGastric Motility

• Gastric Muscle Longitudinal, Circular, and
  Oblique
• Gastric Contraction 3 Dimensional

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Motility Pattern Fasted
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Motility Pattern Fed
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Motility Cycle
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Gastric Emptying Rate

• Rate of Emptying
• (dm/dt)emptyingrate of emptying x gastric
  concentration of drugs
• Emptying vs. Absorption
• Emptying rategtAbsorption Rate
• Emptying rateltAbsorption Rate
• The Rate-Limiting Step Is
• The slower rate

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Factors Affecting Absorption Fasted

• a. osmolarity osmolarity emptying
• b. temperature best at body temperature, rate
  slower if much cooler or much warmer
• e. viscosity viscosity residence time
• d. age young lt elderly (residence time)
• e. dosage form (will be discussed later)

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Factors Affecting Absorption Fed

• a. fat fat emptying rate
• b. carbohydrate sugar emptying rate
• e. protein protein emptying rate
• d. size of food size emptying rate
• e. physical form solid emptying rate
• f. acid acid emptying.
• g. hormonal factor progesterone GI transit time
• esophageal sphinction tone vomiting
  potential
• h. posture Stomach contents are emptied faster
  when standing up than lying down. Poor appetites
  for...
• I. dosage form factor (will be discussed later)

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Solid vs. Liquid Emptying
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Dosage Form Effects

• Liquid Form
• Solid Dosage Form
• Food Effect
• Light vs. Heavy Diet
• Density of Particles
• Dosage Form Designed to Increase Residence Time

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Meal Effect
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Particle Density and Meal Size
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Dosage Form Effects

• Special Devices That Residence Time
• Floating Devices
• Wafer
• Balloon
• Swelling Devices
• Sandwich
• Hydrogel
• Bioadhesive Polymers
• Specially Shaped Device