This document discusses gastro-retentive drug delivery systems (GRDDS), which are designed to prolong the gastric retention of drugs and target drug releases in the upper gastrointestinal tract. It covers the merits and limitations of GRDDS, candidate drugs, approaches like floating, high density, swelling/expanding, and mucoadhesive systems. The document also discusses gastric emptying time, patented GRDDS technologies, and factors that influence gastrointestinal transit.

1. GASTRO-RETENTIVE DRUG DELIVERY
SYSTEM
Submitted to,
Dr. Ravi Shankar Pandey sir
Associate Professor,
Dept. of Pharmacy
GGV, Bilaspur, C.G.
Presented by,
Ms. Shikha Pandey
M. Pharm I sem.
Dept. of Pharmacy,
GGV, Bilaspur, C.G.

2. Content
• Introduction
• Merits & Demerits
• Drug candidate for GRDDS
• Approaches to GRDDS
• GI transit time
• Patented technologies for GRDDS

3. Introduction
• Oral route is a major drug administration site but some drugs are limited by
gastro retention time and there absorption.
• After absorption window, released drug has no or negligible absorption, but
majority of drug have absorption at upper GIT site.
• GRDDS is an approach to prolong gastric retention of drug in the stomach
by targeting site specific drug releases at upper GIT for local or systemic
effect.
• It is obtained by the retaining the dosage form at the stomach by using
various strategies in controlled manner

4. Merits
• Improved drug absorption – increased GRT
• Enhanced bioavailability
• Reduced dose frequency
• Controlled drug delivery of drug
• Local action
• Better patient compliance
• Delivery of drugs with narrow window in small intestine
• Minimize drug fluctuation in plasma.

5. Demerits
• Drugs that cause gastric lesions. Eg – NSAIDS
• Drugs that undergoes to first pass metabolism. Eg- nifedipine
• Drugs having limited acid solubility. Eg- phenytoin
• Drugs which degrade in the acidic environment. Eg.- insulin
• Drug which requires high levels of fluids in stomach for floating
• Drug requires of food to delay gastric emptying

6. Drug candidates for GRDDS
• Drug acting locally in the stomach. Eg- antacids, drugs for H. pylori.
• Drugs that are primarily absorbed in the stomach. Eg- amoxicillin.
• Poorly soluble at alkaline pH. Eg- furosemide, Diazepam
• Drugs with a narrow absorption window. Eg- levodopa, methotrexate
• Drugs which absorbed rapidly from GIT. Eg- metronidazole, tetracycline
• Drugs which degrade in the colon. Eg- ranitidine, metformin

7. Approaches to the GRDDS
• Floating DDS
• High density DDS
• Swelling and expanding DDS
• Muco/Bio adhesive DDS

8. Classification of GRDDS

9. Floating drug delivery system
• Bulk density of drug is less than gastric fluid content.
• Doesn’t affected by gastric emptying rate.
• Releases drug at desired rate.
• May be effervescent and non effervescent.
• Different methods are used for SR/CR.

10. Effervescent- Gas generating system

11. Non-effervescent – gel formation

12. Osmotically controlled DDS

13. High density DDS
• Gastric content density is close to water (1.004gm/𝑐𝑚3
).
• Dosage form’s density should be 3gm/𝑐𝑚3 for retention is necessary.
• Prepared by coating or mixing drug with heavy inert material- diluents.
• Diluents-
➢Barium sulphate
➢Zinc oxide
➢Titanium dioxide
➢Iron powder

14. Drawbacks of high density DDS
• Technically difficult to manufacture with large amount of drug.
• Difficult to maintain desired density.
• High amount of drug is required.

15. Bio/muco adhesive system
• Binds to the gastric epithelial cell or mucin.
• Enabling the device to adhere to the stomach wall- resisting gastric emptying.
• Adhesion mechanisms are
➢Wetting theory
➢Diffusion theory
➢Absorption theory
➢Electron theory

16. Adhesive polymers..
• Chitosan
• Polyacrylic acid
• Sodium alginate
• Hydroxypropyl cellulose
• Tragacanth
• Dextrin
• Polyethylene glycol
• Polylactic acid

17. Drawback
Constant renewal of mucus
Unpredictable adherence
Not widely used

18. Swellable system
• Dosage form swells more than pyloric sphincter size – withstand gastric
transit.
• Swells many times from its original size.
• Also knows as plug type system – tendency
to remain logged at the pyloric sphincter.
• Should be collapsed after lag time.
• SR/CR depends on selection of proper MW
polymer and swelling of polymer.
• Polymers- chitosan, sodium starch glycolate, Carbopol.

19. GI transit time and their modulation
• Gastrointestinal transit is the time it takes for food or drug to leave stomach
and travel through intestines.
GI TT
modulation
Anatomy
of GI
tract
Dynamics
of GI
tracts
GI transit
Ileocecal
junction
Colon
and gut
flora
GI mucus