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
• Pharmaco-dynamic
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 Gastroretentive
dosage forms
• HBS or Colloidal barrier systemsThese 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
