gastro retentive drug delivery system

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GASTRO RETENTIVE DRUG DELIVERY SYSTEM
ADVANTAGES AND APPROACHES
M.SRINIVAS
M.PHARMACY, II SEMISTER
(PHARMACEUTICS)
VAAGESWARI COLLEGE OF
PHARMACY

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CONTENTS
• INTRODUCTION
• APPROPRIATE CANDIDATE DRUGS FOR
GRDDS
• ADVANTAGES
• LIMITATIONS
• APPROACHES
• CONCLUSION
• REFERENCES

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INTRODUCTION
• Oral drug delivery is widely used in
pharmaceutical field to treat the diseases.
• Some drugs are absorbed at specific site only
,these require release at that specific site.
• Gastro retentive drug delivery(GRDDS) is one of
the site specific drug delivery for the delivery of
the drugs at stomach.
• It is obtained by retaining dosage form into
stomach and drug is being released at controlled
manner at specific site

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APPROPRIATE CANDIDATE DRUGS FOR
GRDDS
• Drugs acting locally in the stomach.
E.g. Antacids and drugs for H. Pylori viz.,
Misoprostol.
• Drugs that are primarily absorbed in the stomach.
E.g. Amoxicillin
• Drugs that is poorly soluble at alkaline pH.
E.g. Furosamide, Diazepam, Verapamil, etc.
• Drugs with a narrow absorption window.
E.g. Cyclosporine, , Levodopa, Methotrexate etc.

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• Drugs which are absorbed rapidly from the GI
tract.
E.g. Metronidazole, tetracycline.
• Drugs that degrade in the colon.
E.g. Ranitidine, Metformin.
• Drugs that disturb normal colonic microbes
E.g. antibiotics against Helicobacter pylori.

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ADVANTAGES
• Enhanced bioavailability
• Sustained drug delivery/reduced frequency of
Dosing
• Targeted therapy for local ailments in the upper
GIT
• Reduced fluctuations of drug concentration
• Improved selectivity in receptor activation
• Reduced counter-activity of the body

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ADVANTAGES
• Extended effective concentration.
• Minimized adverse activity at the colon.

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LIMITATIONS
• The drug substances that are unstable in the
acidic environment of the stomach are not
suitable candidates to be incorporated in the
systems.
• These systems require a high level of fluid in the
stomach for drug delivery to float and work
efficiently.

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• Not suitable for drugs that have solubility or
stability problem in GIT.
• Drugs which are irritant to gastric mucosa are
also not suitable.
• These systems do not offer significant
advantages over the conventional dosage forms
for drugs, which are absorbed throughout GIT.

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APPROACHES FOR PROLONGING THE
GASTRIC RESIDENCE TIME
HD
S
F
• High-density systems. S
(HDS) S
A
S
S
• Floating systems. (FS)
• Swelling and expanding
systems. (SS)
• Mucoadhesive &
Bioadhesive systems.
(AS)

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CLASSIFICATION

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HIGH DENSITY SYSTEM
• Gastric contents have a density close to water
( 1.004 g cm−3). When the patient take high-density
pellets , they sink to the bottom of the stomach
where they become entrapped in the folds of the
antrum and withstand the peristaltic waves of the
stomach wall.
• A density close to 2.5 g cm−3 seems necessary for
significant prolongation of gastric residence time.
• Barium sulphate , zinc oxide, iron powder, and
titanium dioxide are examples for excipients used.

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FLOATING DRUG DELIVERY
These have a bulk density lower than the gastric
content. They remain buoyant in the stomach for a
prolonged period of time, with the potential for
continuous release of drug. They Include:
Hydrodynamically balanced systems (HBS)
Gas-generating systems
Volatile liquid/ vacuum containing systems
Raft-forming systems
Low-density systems

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GAS GENERATING SYSTEMS
• Carbonates or bicarbonates, which react with
gastric acid or any other acid (e.g., citric or
tartaric) present in the formulation to produce
CO2 , are usually incorporated in the dosage
form, thus reducing the density of the system
and making it float on the media.

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MATRIX TABLETS
• Single layer matrix tablet is prepared by incorporating
bicarbonates in matrix forming hydrocolloid gelling
agent like HPMC, chitosin, alginate or other polymers
and drug.
• Bilayer tablet can also be prepared by gas generating
matrix in one layer and second layer with drug for its SR
effect.
• Triple layer tablet also prepared having first swellable
floating layer with bicarbonates, second sustained
release layer of drug and third rapid dissolving layer of
bismuth salt.

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INFLATABLE GASTROINTESTINAL
DELIVERY
• System is incorporated with an inflatable chamber
which contains liquid ether -gasifies at body
temperature to cause the chamber to inflate in
stomach.
• Inflatable chamber is loaded with a drug reservoir
which can be a drug, impregnated polymeric then
encapsulated
in a gelatin capsule.

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INTRAGASTRIC OSMOTICALLY CONTROLLED
DDS
 Comprised of both an osmotic pressure controlled drug
delivery device and an inflatable floating support in a
biodegradable capsule.
 In stomach, the capsule quickly disintegrates and release the
intragastric osmotically controlled drug delivery device .
 Inflatable support forms a deformable hollow polymeric bag
containing liquid that gasifies at body temperature to inflate
the bag.
Consists of 2 compartments:
• Drug reservoir
• Osmotically active compartment.

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INTRA-GASTRIC FLOATING GASTROINTESTINAL
DRUG DELIVERY SYSTEMS
• System can be float by flotation chamber, which
may be vacuum or filled with air or a harmless
gas
• Drug reservoir is
encapsulated inside
a microporous
compartment

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HYDRODYNAMICALLY BALANCED SYSYTEMS
 Prepared by incorporating a high level(20-75%w/w) gel-
forming hydrocolloids. E.g.:- Hydoxyethylcellulose,
hydroxypropylcellulose, HPMC & Sod. CMC into the
formulation and then compressing these granules into a
tablets or capsules.
 It maintains the bulk density less than 1.

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RAFT FORMING
• This system is used for delivery of antacids and
drug delivery for treatment of gastrointestinal
infections and disorders.
• The mechanism involved in this system includes
the formation of a viscous cohesive gel in contact
with gastric fluids, forming a continuous layer
called raft.

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HOLLOW MICROSPHERES
• Polymers used commonly: Polycarbonates,
Cellulose acetate, Calcium alginate, Eudragit S,
agar and methoxylated pectin etc.

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ALGINATE BEADS SUPERPOROUS HYDROGELS
• Prepared by dropping sodium • Swellable agents have pore
alginate solution into aqueous size ranging between 10nm to
solution of calcium chloride, 10µm.
causing the precipitation of • Superporous hydrogels will
calcium alginate swell more than the swelling
• Freeze dry in liquid nitrogen at ratio 100,This is achieved by
-40oc for 24h. co-formulation of a
hydrophilic particulate
• Beads-spherical and 2.5 mm in material, and Ac-Di-Sol
diameter. (crosscarmellose).

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EXPANDABLE SYSTEMS
1.UNFOLDED SYSTEMS 2.SWELLABLE SYSTEMS
 The swelling is usually results
from osmotic absorption of water.
 The device gradually decreases in
volume and rigidity as a result
depletion of drug and expanding
agent and/or bioerosion of
polymer layer, enabling its
elimination.

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MUCOADHESIVE SYSTEMS
• The basis of mucoadhesion is that a dosage form can stick to the
mucosal surface by different mechanisms.
• Examples for Materials commonly used for bioadhesion are
poly(acrylic acid) (Carbopol®, polycarbophil), chitosin, Gantrez®
(Polymethyl vinyl ether/maleic anhydride copolymers),
cholestyramine, tragacanth, sodium alginate

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MAGNETIC SYSTEM
•Based upon the principle that dosage form contains
a small internal magnet ,and a magnet placed on the
abdomen over the position of stomach can enhance
the GRT.

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Marketed Products of GRDDS
Brand name Delivery system Drug (dose) Company
name
Valrelease® Floating capsule Diazepam (15mg) Hoffmann-LaRoche,
USA
Madopar® HBS Floating, CR capsule Benserazide (25mg) and L- Roche Products,
(Prolopa® HBS) dopa (100mg) USA
Liquid Gaviscon® Effervescent Floating Al hydroxide (95 mg), Mg GlaxoSmithkline,
liquid alginate Carbonate (358 mg) India
preparations
Topalkan® Floating liquid alginate Al – Mg antacid Pierre Fabre Drug,
Preparation France
Conviron® Colloidal gel forming Ferrous sulphate Ranbaxy, India
FDDS
Cytotech® Bilayer floating capsule Misoprostol (100μg/200μg) Pharmacia, USA
Cifran OD® Gas-generating floating Ciprofloxacin (1gm) Ranbaxy, India
form

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CONCLUSION
• Gastro retentive drug delivery systems have
emerged as a current approache of controlled
delivery of drugs that exhibit an absorption window.
• All these drug delivery systems have their own
advantages and drawbacks.
• To design a successful GRDDS, it is necessary to
take into consideration the physicochemical
properties of the drug, physiological events in the
GIT, formulation strategies, and correct
combination of drug and excipients.

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REFERENCE
• N K Jain. Gastroretentive drug delivery systems:
Garima Chawla, Piyush Gupta and Aravind K.
Bansal, editors. Progress in controlled and novel drug
delivery systems.New delhi.
• S.P.vyas, roop K.khar controlled drug delivery
concepts and advances page no.196-217.

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