• Conventional oral drug delivery system (DDS)
is complicated by limited gastric residence
• Rapid GI transit can prevent complete drug
release in absorption zone & reduce the
efficacy of the administered dose since the
majority of drugs are absorbed in stomach or
the upper part of small intestine.
• Among the GRDDS, floating drug delivery
system have been the most commonly used.
• Gastro-retentive delivery is one of the site
specific delivery of the drugs at stomach. It is
obtained by retaining dosage form into
stomach and drug is being released at
sustained manner to specific site either in
stomach or intestine.
• Longer residence time in stomach could be
advantages for local action in stomach.
• Bioavailability can be improved.
• Site specific delivery.
• Minimize the fluctuation of drug concentration.
Candidates of GRDDS
• Drugs acting locally in the stomach.
• Drugs with less half life.
• Drugs absorbed readily from the GI track.
LOW DENSITY APPROACH(FDDS)
• The gastric empting time in human which
normally averages 2-3 hours through the
major absorption zone (stomach and upper
part of intestine) can result in incomplete drug
release from the dug delivery system leading
to reduced efficacy of administered dose.
• Lower dosing and less side effects.
• Beneficial in the treatment of gastric diseases.
• The drug substances that are unstable at
acidic environment of the stomach
• These systems require high level of fluid in the
stomach for drug delivery to float and work
• Not suitable for drugs that have solubility or
stability problem in GIT
Problems of Muco-adhesive system
• Rapid removal of mucus
• We are not sure weather the DF will adhere to
the mucus or epithelial cell layer
• DF may adhere to esophagus resulting in drug
HIGH DENSITY APPROACH
• Density should be more than stomach content
i.e. 3 gm/cm3
• Prepared by coating or mixing drug with heavy
Problems with higher density
• Higher amount of drug require
• The dosage form must stand with peristaltic
movement of stomach
Limitations of GRDDS
• It is not recommended for drugs which are
unstable at gastric/acidic PH, insoluble or very
low soluble drugs and drugs which causes
• For floating, high level of fluid is required in
GIT. Also sleeping condition is favorable for
the better results of GRDDS.
• For swelling systems, it is necessary that the
formulation should not exist before the
• For High density system, High amount of drug