Gastro Retentive Drug Delivery System
Session Objectives
By the end of this session, students will be able to:
• Explain various gastro-retentive strategies for drug absorption
• Elaborate various factors to be considered in the design of GRDDS
• Explain the significance of various processes involved in preformulation of GRDDS
• Formulate a suitable gastro-retentive dosage form based on the need and drug characteristics
GASTRIC RETENTIVE TECHNOLOGIES
- Floating Drug Delivery Systems
(a) Non-Effervescent Systems
(i) Colloidal Gel Barrier System (hydro dynamically balanced system)
(i) Micro porous Compartment System
(ii) Alginate Beads(
iii) Hollow Microspheres / Microballons
(b) Gas-Generating (Effervescent) Systems
2. Expandable systems
3. Bio/Muco-Adhesive Systems
4. High-Density Systems
Classification of Gastro Retentive Drug Delivery Systems
Hydro dynamically Balanced System
Factors controlling gastric retention time of dosage
– Density of dosage form
• A density of <1.0 g. /cm3 is required to exhibit the floating property
• Dosage forms having density lower than that of the gastric fluids
– Size of the dosage form
• The larger the size of the dosage form, the greater will be the gastric retention time, because the larger size would not allow the dosage form to quickly pass through the pyloric antrum into the intestine
– Food intake, nature of the food
• Usually the presence of food increases the GRT (Gastric retention time) of the dosage form and increases drug absorption by allowing it to stay at the absorption site for a longer time
– Effect of gender, posture, age
• In the upright position, the floating systems floated to the top of the gastric contents and remained for longer time, showing prolonged GRT
• Because of the changes in physiology with increasing age and the hormonal responses responsible for gastric emptying, the GRT of the dosage forms may vary with the age of the individual
Advantages
• Pharmacokinetic aspects
Ø Enhanced bioavailability
Ø Enhanced first pass biotransformation
Ø Improved bioavailability due to reduced P-glycoprotein activity in the duodenum
Ø Reduces frequency of dosing
Ø Targeted therapy for local ailments in the upper GI tract
• Pharmacodynamic aspects
v Drug concentration fluctuations are reduced
v Receptor activation selectivity is improved
v Reduces counter-activity of the body
v Extend time over critical (effective) concentration
v Minimum adverse activity occurs at colon
Summary
• Gastro retentive drug delivery system is an approach to prolong gastric residence time, thereby targeting site-specific drug release in upper gastro intestinal tract
• FDDS is considerably easy and logical approaches in development of Gastro-retentive dosage forms
• HBS or Colloidal barrier systems These are single-unit dosage forms, containing one or more gel-forming hydrophilic polymers
• Formulation excipients used for the GRDDS should have density < 1.0 g. /cm3
For PDF Notes Click on Download Button
