This document discusses gastroretentive drug delivery systems (GRDDS), which are designed to increase the gastric retention time of drugs. There are four main approaches for GRDDS: floating systems, bioadhesive systems, high density systems, and swellable systems. Floating systems have a lower density than gastric fluids and float on the stomach contents, releasing the drug slowly. Bioadhesive systems bind to gastric cells and increase retention time. High density systems use coatings like barium sulfate or zinc oxide to increase the dosage form density above gastric fluids. Swellable systems swell upon ingestion to a size that prevents exiting the pylorus and prolongs retention time. GRDDS provide benefits like enhanced bioavailability,

1. GRDDS:- Gastroretentive
drug delivery system
Rahul Sharma

2. Defination
● Gastroretentive drug delivery
system is an approch to increase
the gastric residense time of the
drug.
● It is obtained by retaining dosage
form into stomach and release
them in controlled manner.

3. Approches for GRDDS
1. Floating system.
2. Bio/Mucoadhesive system.
3. High Density system.
4. Swellable System.

4. 1. Floating system (Low-density system)
● Floating drug delivery system have
a bulk density lower than gastric
fluids.
● So,the drug remain buoyant (float)
in the stomach for prolonged period
of time.
● While the system is floating on
gastric contents , the drug is
released slowly at desired rate.

5. Techniques of floating system
★ Effervescent
● Gas generating
system.
● Volatile liquid
containing system.
★ Non-effervescent
● Colloidal gel barrier.
● Hollow
microspheres.

6. 2.Bio/Mucoadhesive system
● In this , system binds to
gastric cell surface and
causes the increase in
GRT.
● Bio/Mucoadhesive
binds by different
mechanisms:-
MOA
Wetting Theroy
Diffusion Theory
Absoption Theory
Electron Theory
1.
2.
3.
4.

8. 3. High density system
● Gastric contents have density close to water (1.004) .
● A density close to 2.5 gm cm-³ is necessary to
increase GRT.
● This system uses the density of dosage form as the
retention mechanism.

9. ● In this system drug may
be coated with an
excipient such as:-
Barrium sulphate, zinc
oxide , iron powder etc.
● Due to these excipients
the drug may sink in
stomach and leads to
high GRT.

10. 4.Swellable System
● These are the dosage form which after
swallowing, swell to an extent that prevents its
exit from pylorus.
● As a result, the dosage form remain in stomach
for longer time.
● Materials such as HPMC, carbopol and chitosan
are used for coating of drug in this type of system.

12. Application of GRDDS
➔ Enhanced bioavailability.
➔ Sustained drug release.
➔ Enhanced absoption.
➔ Site specific drug delivery.