Floating Systems

A dosage unit with lower relative density than gastric contents is less disposed to be propelled towards the pyloric sphincter but to reside in the fundus or body of the stomach [27-29]. Units can be either monoliths or multiparticulate. Such buoyancy might be effected by a number of techniques, viz.

G astro retentive Platform

Pyloric Sphincter

G astro retentive Platform

Pyloric Sphincter

Floating

Swelling/Expansion Sinking

Mucoadhesiort

Gastric Medium

Floating

Swelling/Expansion Sinking

Mucoadhesiort

Gastric Medium

Fig. 6.6 Gastro-retentive systems

• Gel formation: Hydrocolloids (xanthan gum), polysaccharides (HPMC), synthetic polymers (poly(ethylene oxide), carbopol), and natural gums (alginates, guar gum) have been used to prepare flotation platforms [30-34].

• Effervescent systems: Inclusion of an effervescent couple, e.g., sodium bicarbonate, citric acid in the unit leads to interaction and evolution of carbon dioxide in the gastric medium. Gas entrapment by the hydrophilic polymers reduces density, enhances buoyancy, flotation, and gastroretention [31].

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