sk1.pptx

GASTRO RETENTIVE DRUG
DELIVERY SYSTEM
Presented By,
Sathish kumar .P
M.Pharmacy 1st Semester
Department of Pharmaceutics
Nandha college of Pharmacy, Erode-52.
Wednesday, June 21, 2023 1

CONTENTS
• Introduction
• Need of Gastric retention
• Advantages
• Limitation
• Physiology of Stomach
• Approaches of Gastric retention
• Evaluation of GRDDS
• Conclusion.

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.

GASTRO RETENTION IS DONE FOR:
• Drugs acting locally in the stomach.
E.g. Antacids and drugs for H. Pylori viz., Misoprolol.
• Drugs that are primarily absorbed in the stomach.
E.g. Amoxicillin
• Drugs that is poorly soluble at alkaline pH.
E.g. Furosemide, Diazepam, Verampil, etc.
• Drugs with a narrow absorption window.
E.g. Cyclosporine, Levodopa, Methotrexate etc.
• 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 H. Pylori.

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

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.

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).

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
– duodenun
– jejunum
– ileum
• large intestine.

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.

Approaches for gastric retention
• Floating drug delivery systems
• Mucoadhesive system
• Swellable Systems
• High density systems.

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)
• Released from the system at desired rate.

MECHANISM OF FDDS
• FDDS has a bulk density less than gastric fluids and soremain
buoyant in the stomach without affecting the gastric emptying rate
for a prolonged period of time.
• F= buoyancy- gravity = (Df-Ds)gv
Where,F= total vertical force, weling system
• Df= fluid density,
• Ds= object density,
• v = volume,
• g= acceleration due to gravity.

POLYMERS USED IN FLOATING TABLETS
• Hydrochlorides:HPMC 1000,HPMC 4000,, ẞ Cyclodextrin, Sodium alginate,
HPC-L, CP 934P, HPC, Eudragit S, HPMC, Metolose S.M. 100, PVP, HPC-H,
HPC-M, HPMC K15, Polyox, HPMC K4, Acrylic polymer, E4 M and
Carbopol.
• Inert fatty materials: Beeswax, fatty acids, long chain fatty alcohols.
• Effervescent agents :Sodium bicarbonate, citric acid, tartaric acid, Di-SGC (Di-
Sodium Glycine Carbonate, CG (Citroglycine).
• Release rate accelerants (5%-60%):eg. lactose, mannitol.
• Release rate retardants (5%-60%) :eg. Dicalcium phosphate, talc, magnesium
stearate.
• Buoyancy increasing agents (upto80%):eg. Ethyl cellulose.
• Low density material:Polypropylene foam powder (Accurel MP 1000).

Gas Generating SYSTEM / Hydrodynamically BALANCED
System (HBS)
• It is formulated by intimately mixing the CO2 generating agents and the drug
within the matrix.
• The drug is slowly released at a desired rate from the floating system and after
the complete release, the residual system is expelled from the stomach.
• This leads to an increase the GRT and a better control over fluctuations in
plasma drug concentration.

Volatile liquid/ vaccum containing system
• These systems contain an inflatable chamber, which
contains a liquid (ether, cyclopentane), that gasifies at
body temperature to cause inflatation of the chamber in
stomach.
• These devices are osmotically controlled floating
systems containing a hollow deformable unit that can
convert from a collapsed to an expanded position, and
returns to collapsed position after an extended period.

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.

Non Effervescent System
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,

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

• Swelleble Drug Delivery System

High Density Delivery System

• Mucoadhesion Delivery System

Theories Of Mucoadhesion

MAGNETIC SYSTEM
• This approach to enhance the GRT is based on the simple
principle that the dosage form contains a small internal
magnet, and a magnet placed on the abdomen over the position
of the stomach.
• Although magnetic system seems to work, the external magnet
must be positioned with a degree of precision that might
compromise patient compliance.

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 37°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.

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.

Bioadhesion strength measurement

Swelling systems
• Weight gain and water uptake
• Done by immersing the dosage in simulated gastric fluid at 37°C 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.
= WU (W-W) X 100
W0
• Where WU - Water uptake.
• W, weight of dosage form at time t.
• W weight of dosage form initially.

Commercial Gastroretentive Formulation

References
• Doshi S.M., Tank H.M., Gastro Retention - An Innovation over
Conventional poorly Soluble Drugs: A review, International
Journal of Pharmaceutical and chemcal Sciences, 2012;1(2):859-
866.
• S. P. Vyas, Roop K. Khar, CONTROLLED DRUG DELIVERY -
Concepts & Advances, Vallabh Prakashan, page no. 196-217.
• Shweta A, Javed A, Alka A, Roop K, and Sanjula B. Floating drug
delivery systems: a review. AAPS PharmSciTech. 2005;6 (3)
Article 47.

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