1.
Presented By : Akash Aher
(M.pharm -2nd semester)
Guided by : Dr.G.S Asane
(Dept. of pharmaceutics)

2.
Contents
 Introduction
 Need of Gastric retention
 Advantages
 Limitation
 Physiology of Stomach
 Approaches of Gastric retention
 Evaluation of GRDDS
 Conclusion

3.
Introduction
 Oral drug administration has been the predominant
route for drug delivery.
 Gastric residence time is time which a drug resides in
stomach.
 Depends upon fluid and food intake.
 GRDDS are designed to delay gastric emptying.

4.
Gastro retention is done for:
 Drugs that absorb from stomach (
Levodopa, Furosemide).
 Acting locally in stomach (Antacids, Antiulcer and
Enzymes).
 Antibiotic therapy.
 Poorly soluble at alkaline pH.( Diazepam, Salbutamol)
 Degrade in colon. (Captopril, Ranitidine, Metronidazole)
 Narrow window of absorption

5.
Fig.no-1

6.
Gastric retention is unsuitable for:
 Drugs having limited acid solubility. (Phenytoin)
 Instable in gastric conditions. ( Erythromycin)
 Extensive first pass metabolism.
Factors affecting gastric retention of dosage forms
 Density
 Size
 Shape

7.
Advantages
 Improved drug absorption, because of increased GRT and
more time spent by the dosage form at its absorption site.
 Controlled delivery of drugs.
 Minimizing mucosal irritation by releasing drugs slowly at
a controlled rate.
 Treatment of gastrointestinal disorders such as gastro-
esophageal reflux, providing local action.
 Ease of administration and better patient compliance.

8.
Limitations-
 Retention in the stomach is not desirable for drugs that cause
gastric lesions (e.g. Non- steroidal anti-inflammatory drugs
NSAIDs).
 Drugs that are degraded in acidic environment of stomach
(e.g. Insulin).
 Drugs that undergo a significant first-pass metabolism (e.g.
Nifedipine).
 Drugs that have very limited acid solubility (e.g. Phenytoin).

9.
Review of Stomach & GIT
A tube about nine meters long that runs through the middle of
the body from the mouth to the anus and includes ;
 throat (pharynx),
 esophagus,
 stomach,
 small intestine
- duodenum
- jejunum
- ileum
 large intestine .
Fig.no-2

10.
Gastrointestinal dynamics
 These are the four
motility phases within
the stomach during
fasting stage.
 The dosage form should
be capable of withstanding the housekeeping action of
phase III.

11.
Approaches for gastric retention
 Floating drug delivery systems
 Mucoadhesive systems
 Swellable Systems
 High density systems.
Fig.no-3

12.
Fig.no-4

13.
Floating drug delivery systems
 These are low density systems.
 Have ability to float over gastric contents.
 The drug is must have sufficient structure to form a cohesive
gel barrier.
 It must maintain an overall specific gravity lower than that of
gastric contents (1.004 – 1.010).
 eased from the system at desired rate.

14.
Floating Techniques
 Effervescent
 Volatile liquid containing systems
 Gas generating systems
 Non-Effervescent
 Colloidal gel barrier systems
 Alginate beads
 Hollow Microspheres
 Microporous Compartment System

15.
Effervescent systems
1.Gas generating systems
 Effervescence is there.
 Utilizes effervescent reactions between
carbonate/bicarbonate salts and citric/tartaric acid.
 CO2 is released in presence of H2O.
 When tablet is put in beaker it will sink
 2NaHCO3+C4H6O6 C4H4Na2O6+2CO2+2H2O
 With production of gas it rises up and floats.

16.
2. Volatile liquid containing systems
 Incorporates an inflatable chamber, which contains a liquid
e.g. ether, cyclopentane, that gasifies at body temperature to
cause the inflatation of the chamber in the stomach.
 The device may also consist of a bioerodible plug made up
of PVA, Polyethylene, etc. that gradually dissolves causing
the inflatable chamber to release gas and collapse after a
predetermined time to permit the spontaneous ejection of
the inflatable systems from the stomach.
 There systems are very less used as the gas generating
systems are more safe.

17.
Non-effervescent systems
1. Colloidal gel barrier systems
 Such systems contains drug with gel forming hydrocolloids
meant to remain buoyant on stomach contents.
 These systems incorporate a high level of one or more gel
forming highly Swellable cellulose type hydrocolloids.
e.g.HEC, HPMC, NaCMC.
 On coming in contact with gastric fluids forms a viscous core.
 Incorporates H2O and entraps air.
 Density of system falls below 1gm/cm3. Then it starts floating
Fig.no-5

18.
2. Microporous membrane systems
 Based on the encapsulation of drug reservoir inside a
Microporous compartment.
 The peripheral walls of the drug reservoir compartment are
completely sealed to prevent any direct contact of the gastric
mucosal surface with the undissolved drug.
 In stomach the floatation chamber containing entrapped air
causes the delivery system to float over the gastric contents.
 Gastric fluid enters through the apertures, dissolves the
drug, and carries the dissolve drug for absorption.

19.
3. Alginate beads
 Spherical beads of approximately 2.5 mm in diameter can be
prepared by dropping a sodium alginate solution in to
aqueous solutions of calcium chloride, causing precipitation
of calcium alginate.
 Sodium alginate+ Calcium chloride Calcium alginate+
NaCl
 The beads are then separated snap and frozen in liquid
nitrogen, and freeze dried at -40°C for 24 hours, leading to the
formation of porous system.
 Maintain a floating force of over 12 hours.

20.
4. Hollow microspheres
 Microballoons / hollow microspheres loaded with drugs
are prepared by simple solvent evaporation method.
 Commonly used polymers to develop these systems are
polycarbonate, cellulose acetate, calcium
alginate, Eudragit S, agar and pectin etc.
 These systems have capacity to float on acidic dissolution
media containing surfactant for about 12 hours invitro.

21.
Cont…
Fig.no-6

22.
Mucoadhesive systems
 Involves the use of bioadhesive polymers, which can adhere
to the epithelial surface in the stomach.
 Dosage form can stick to mucosal surface by following
mechanisms:
1. The wetting theory
2. The diffusion theory
3. The absorption theory
4. The electron theory

23.
Swellable systems
 A dosage form in the stomach will withstand gastric transit if
it bigger than pyloric sphincter, but should be small enough
to be swallowed.
 These systems swells many times its original size.
 Cross linking should be optimum highly cross linked don’t
swell.
 Chitosan, HPMC, sodium starch glycolate, carbopol are used.
 Diclofenac, Ciprofloxacin, Furosemide are reported with
these systems.

24.
Fig.no-7

25.
High density systems
 These have density greater than that of gastric fluids (1.4
g/cc).
 Above 1.6g/cc is preferable, tend to withstand peristaltic
movements of stomach.
 Zinc oxide, Iron oxide, Titanium dioxide, barium sulfate are
used as inert heavy core.
Fig.no-8

26.
Evaluation of GRDDS
Floating drug delivery systems
Floating time
• Determined by using the USP dissolution apparatus
containing 900 ml of 0.1 N HCL maintained at 37o C.
• The time for which the dosage form floats is termed
as the floating time.
Specific Gravity / Density
• Density can be determined by the displacement
method using Benzene as displacement medium

27.
Muco – Adhesion system
 Measurement of either tensile or shear strength is the most
commonly used invitro method to measure bioadhesion
strength.
 Measurement of tensile strength involves quantiting the force
required to break the adhesion bond between the test
polymer and model membrane.
 The method typically uses modified balance or tensile tester

28.
Bioadhesion strength measurement
Force measuring
device
Upper jaw
Polymer
Lower jaw
Membrane
Fig.no-9

29.
Swelling systems
Weight gain and water uptake
 Done by immersing the dosage in simulated gastric fluid
at 37oC and determining these factors at regular intervals.
 Dimensional changes can be measured in terms of
increase in the tablet diameter or thickness with time.
 Water uptake is measured in terms of %weight gain

30.
WU = (Wt-Wo) X 100
Wo
Where WU – Water uptake
Wt weight of dosage form at time t
Wo weight of dosage form initially

31.
Commercial Gastroretentive
Formulation

32.
Conclusion
Gastro retentive drug delivery systems are the most
preferable systems in order to deliver the drugs which
have a narrow absorption window near the gastric
region. Now a days a number of drug delivery devices
are being developed which aim at releasing the drug at
gastric region. Even though these drug delivery systems
have several advantages they also have disadvantages
like their invitro – invivo correlation is very less.

33.
References
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 Chien Yie W. “ Novel drug delivery systems”, Vol-50, 2nd
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34.
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35.
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