Approaches to gastro retentive drug delivery

1. School of pharmaceutical sciences, CSJMU KANPUR 1
Presented by
AYUSH DUBEY
M. Pharm 1 yr.
(Pharmaceutics)

2. School of pharmaceutical sciences, CSJMU KANPUR 2
INTRODUCTION :
 The oral delivery of drugs is the most favored route of administration because of ease of
administration.
 Oral route has patient compliance, ease of ingestion, pain avoidance & versatility to
accommodate various type of drug.
 Problems associated with Conventional drug delivery –
o Short gastric retention time.
o Incomplete drug release from dosage form.
o Degradation of drug in gastric fluid.

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GASTRO-RETENTIVE DRUG DELIVERY SYSYEM
 Dosage forms that can be retained in the stomach are called GRDDs.
 These dosage forms can persist in the stomach for prolonged period of time and thus
increases the GRT of drugs.
 Gastro-retention helps to improve bioavailability of drugs.
 Prolonging the gastric retention of the drugs helps to achieve-
o Slow release of the drug from dosage form.
o to maintain an effective drug conc. for longer time period.
o Reduces drug waste.
o Improves the drug solubility that are less soluble

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Mechanisms for achieving controlled gastric retention time are: Muco-adhesion, floatation,
sedimentation, expansion, etc.
Approaches to increase GRT :
High-density system
Low-density system (floating system)
Bio-adhesive system
Gas generating system
Raft forming system
Magnetic system

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HIGH-DENSITY SYSTEM :
 The drug is retained at the bottom of the stomach.
 Retention mechanism is sedimentation, this help in
withstanding the peristaltic movement of GIT.
 Dosage forms have density approx. 3gm/cm3 (more than normal
stomach content).
 Such formulations are prepared by coating or mixing the drug
with inert material (excipients).
 Commonly used excipients are barium sulphate, zinc oxide,
titanium dioxide, and iron powder.

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LOW-DENSITY SYSTEM (FLOATING SYSTEM) :
 These are the low density systems.
 Their density is lesser than the gastric fluid (1.004 gm/cm3),
resulting into floating of the dosage form.
 GRT increases thereby decreasing fluctuation in plasma drug
concentration.
 A lag phase exist (rate of swelling).

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TYPES OF FLOATING SYSTEM :
i. Effervescent system
 Gas generating agents (sodium bicarbonate, citric acid
and tartaric acid) are used to produce CO2.
 This CO2 release decreases the density of the dosage
form allowing it to flow.
ii. Non-effervescent system
 This system works on mechanism of swelling of
polymer.
 It utilizes gel-forming or highly swellable cellulose

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BIO-ADHESIVE SYSTEM :
 A muco-adhesive polymer is used that adheres to the gastric
mucosal surface.
 used as a delivery device within the lumen to enhance
drug absorption in a site specific manner.
 This adhering to mucus layer enhances GRT.
 Muco-adhesive polymer are of
a- Natural origin (sodium alginate, gelatin, guar gum, etc.)
b- Semi-synthetic (HPMC, Carbopol, sodium carboxymethyl cellulose)

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RAFT FORMING SYSTEM :
 The mechanism of raft formation includes the formation of
viscous cohesive gel in contact with gastric fluids.
 Each portion of the liquid swells forming a continuous layer
called a raft.
 Raft floats on gastric fluids because of low bulk density
created by the formation of CO2.

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MAGNETIC SYSTEM :
 Magnetic field is used to retain drug in the stomach.
 Dosage form contains Polymer + Drug +Excipients
+Internal magnet (ferric ions).
 External magnetic field is applied to get to specific site.
 Position of formulation and intensity of magnetic field
affect GRT.
 Lack of patient compliance, experts supervision is required.

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