GASTRO-RETENTIVE DRUG DELIVERY SYSTEM

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GASTRO-RETENTIVE DRUG DELIVERY SYSTEM:

GASTRO-RETENTIVE DRUG DELIVERY SYSTEM BY: H.JOHN PAUL M.Pharmacy (2 nd semester) Pharmaceutics UNDER THE GUIDANCE OF: M.ARAVIND PROFESSOR

CONTENTS:

CONTENTS INTRODUCTION DEFINITION GASTROINTESTINAL DYNAMICS NEED FOR GASTRORETENTION FACTORS AFFECTNG GASTRORETENTION TYPES OF GASTRORETENTIVE SYSTEMS EVALUATION OF GASTRORETENTIVE SYSTEMS CONCLUSION

INTRODUCTION:

INTRODUCTION Oral route is most acceptable route for drug administration. Apart from conventional dosage forms several other forms were developed in order to enhance the drug delivery for prolonged time period and for delivering drug to a particular target site. Some drugs with narrow absorption index and drugs which undergo carrier mediated transport in the region of stomach and upper part of small intestine have poor bioavailability when administered as conventional dosage forms. In order to overcome such issues, gastro retentive drug delivery systems were developed.

DEFINITION :

DEFINITION These are the drug delivery systems which possess the ability of retaining the drug in the GIT particularly in the stomach for prolonged period of time. After the drug release for required time period the dosage form should get degraded without causing any gastric disturbances.

NEED FOR GASTRO RETENTION:

NEED FOR GASTRO RETENTION A controlled drug delivery system with prolonged residence time in the stomach is of particular interest: These systems are helpful in treatment of Peptic ulcers For drugs those are absorbed at the proximal part of the GIT tract. Ex: Gabapentin Ciprofloxacin etc

ADVANTAGES:

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

LIMITATIONS:

LIMITATIONS They require a sufficiently high level of fluids in the stomach for the drug delivery buoyancy, to float therein and to work efficiently. Floating systems are not feasible for those drugs that have solubility or stability problems in gastric fluid. Drugs which are well absorbed along the entire GI tract and which undergoes significant first- pass metabolism, may not be desirable candidates for GRDDS since the slow gastric emptying may lead to reduced systemic bioavailability. Drugs that are irritant to gastric mucosa are not suitable for GRDDS.

GASTROINTESTINAL DYNAMICS:

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.

FACTORS AFFECTING GASTRO RETENTION:

FACTORS AFFECTING GASTRO RETENTION Shape : Better GRT is possessed by tetrahedron and ring shaped devices. Single or multi-unit dosage forms : Multi dosage forms show more effect comparing to the single unit dosage forms. Caloric content : High meal is responsible for the increased GRT. Age : Elder people have significant longer GIT Posture : GRT can be varied between upright and supine positions of the patients.

TYPES OF GASTRORETENTIVE SYSTEMS:

TYPES OF GASTRORETENTIVE SYSTEMS Floating drug delivery systems Bioadhesive drug delivery systems Expandable drug delivery systems High density systems Super porous hydrogels Magnetic systems

FLOATING SYTEMS:

FLOATING SYTEMS The systems which are having a bulk density lower than the gastric content is known as Floating drug delivery systems They have the potential for continuous release of drugs and remain buoyant in the stomach for a prolonged period of time. The residual system must get emptied from stomach eventually. Types: 1. Hydrodynamically Balanced System. 2. Gas Generating System. 3. Raft forming System.

HYDRODYNAMICALLY BALANCED SYSTEMS:

HYDRODYNAMICALLY BALANCED SYSTEMS These systems are single unit dosage forms containing one or more gel forming hydrophilic polymers such as HPMC, HEC etc Usually drug is mixed with a polymer and usually administered in gelatin capsules. These capsules readily dissolve in gastric fluid. The hydration and swelling of surface polymers produces a floating mass

GAS GENERATING SYSTEMS:

GAS GENERATING SYSTEMS These formulations contain carbonates or bicarbonates which generates CO 2 due to their reaction with acids either as natural gastric acid or coformulated as citric acid, tartaric acid In case of single unit systems, effervescent substances are introduced in the hydrophilic polymers and CO 2 bubbles are trapped in the swollen matrix.

RAFT FORMING SYSTEMS:

RAFT FORMING SYSTEMS These systems consists of some gel forming agents. Ex: sodium alginate solution containing carbonate or bicarbonate These systems produce a layer on the top of the gastric fluids Usually, used in the treatment of gastroesophageal reflux.

EXPANDABLE SYSTEMS:

EXPANDABLE SYSTEMS These dosage forms are usually small enough to be swallowed. In the stomach after coming into contact with the gastric fluids, they get expanded to a larger size so that gastric retention is achieved. After the drug release they should retain into a final small form for easy evacuation.

UNFOLDABLE SYSTEMS:

UNFOLDABLE SYSTEMS In these systems, the compressed systems are placed in carriers such as capsules and are administered. On their contact with gastric fluid these systems get unfolded into forms which can get unfolded into forms which can be retained in the stomach for definite time period SWELLABLE SYSTEMS Swellable systems are retain because of their mechanical properties. These systems absorb water and then swell. Initially the dosage form is very small for swallowing, after reaching the stomach the dosage form will swell in their size and cause retention.

SUPER POROUS HYDROGELS:

SUPER POROUS HYDROGELS These have a pore size ranging from 10nm to 10 micrometre These super porous hydrogels swells to an equilibrium size because of their nature of rapid water intake by capillary wetting through their pores. They swell to larger size and can withstand a pressure with gastric contraction. And due to this larger size their passage through the pyloric sphincter is prevented.

BIOADHESIVES:

BIOADHESIVES In these systems the dosage form will stick to the mucosal surface in the gastrointestinal tract as a result of which prolonged gastric retention can be achieved. MAGNETIC SYSTEMS In these systems the dosage forms contain a small internal magnet is placed externally over the abdomen. Because of this technique the dosage form with an internal magnet is retained in the stomach region until the external magnet remains.

EVALUATION OF GASTRORETENTIVE DRUG DELIVERY SYSTEMS:

EVALUATION OF GASTRORETENTIVE DRUG DELIVERY SYSTEMS General tests : Appearance, hardness, friability, Drug content, weight variation, Uniformity of content, Dissolution time and drug release. Buoyancy lag time and duration of buoyancy : the buoyancy lag time and duration of buoyancy were performed in the USP dissolution apparatus II in simulated gastric fluids (SGF) and 0.1N HCl maintained at 37 0 C environment. The time interval between the introduction of the tablet into the dissolution medium and till the tablet reaches the surface was taken as buoyancy lag time and the duration of buoyancy was observed visually.

EVALUATION OF GASTRORETENTIVE DRUG DELIVERY SYSTEMS:

EVALUATION OF GASTRORETENTIVE DRUG DELIVERY SYSTEMS Swelling studies : Tablets weighed individually (W1) and placed in Petri dishes containing 15ml of 0.1N HCl. At regular intervals they are removed from Petri dishes and excess surface water was removed using filter paper The swollen tablets were reweighed (W2). The swollen tablets are dried at 60° C at 24hrs in an oven and kept in desiccators for 24hrs and reweighed (W3). Degree of swelling = W2 - W1 W1 %Erosion = W1 - W3 X 100 W1

CONCLUSION:

CONCLUSION Gastroretentive 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.

REFERENCES:

REFERENCES Chien Yie W. “ Novel drug delivery systems”, Vol-50, 2 nd ed, Marcel Dekker . Inc, New York. Pg No.164-177. Anand S. Surana & Rakhee K. Kotecha, “An overview on various approaches to oral controlled drug delivery system via gastroretention” IJPSRR, Vol-2, May-June 2010. pp: 68-72 S.P. Vyas & Roop K. Khar, “Controlled Drug Delivery”, Vallabh Prakashan, Pg No. 196-215.

THANK YOU:

THANK YOU

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