Mechanism:
Floating systems, also known as hydrodynamically balanced systems, are dosage forms that have a bulk density lower than the gastric fluids, allowing them to float on the surface.
The basic idea is that the floating system remains buoyant in the stomach until the drug is released at a desired rate.
Components:
1. Polymers:
Polymers play a key role in the formulation of floating systems.
Polymers such as hydroxypropyl methylcellulose (HPMC), ethylcellulose, and carbopol are often used to control the release rate of the drug from the system.
2. Gas-generating agents:
Sodium bicarbonate and citric acid can be incorporated.
In the presence of gastric fluids, these agents produce carbon dioxide, which gets entrapped in the swollen hydrocolloids, enabling the dosage form to float.
Types:
I. Effervescent Floating Tablets:
These contain bicarbonate ions and acid that produce carbon dioxide.
The CO2 produced gets entrapped, causing the tablet to float.
II. Non-effervescent Floating Systems:
These rely on the swelling capacity of polymers (e.g., gel-forming or swellable polymers like HPMC).
When the tablet comes into contact with gastric fluid, the polymer swells, decreasing the density and making the tablet float.
Applications:
I. For drugs acting in the stomach:
Drugs like antacids can be formulated into floating dosage forms to prolong their residence in the stomach.
II. For drugs absorbed from the stomach:
Drugs such as amoxicillin and levodopa, which are absorbed primarily from the stomach, can benefit from floating systems.
III. For drugs that have a narrow absorption window in the upper part of the intestine:
This includes drugs like furosemide and riboflavin.
