Controlled Release in Gastroretentive Drug Delivery Systems

Gastroretentive drug delivery systems (GRDDS) are designed to prolong the residence time of a drug in the stomach, providing controlled release and better absorption in specific regions of the gastrointestinal (GI) tract, primarily the upper part. These systems offer advantages for drugs that are:

  • Poorly absorbed from the lower GI tract.
  • Have a narrow absorption window in the upper part of the intestine.
  • Are prone to degradation in the alkaline pH of the intestine.

Key Features of GRDDS:

  1. Enhanced Bioavailability: By retaining the drug in the stomach, GRDDS allows prolonged drug exposure to the absorptive areas, improving bioavailability.

  2. Sustained Release: Drugs can be released at a controlled rate over time, maintaining therapeutic levels for an extended period and reducing dosing frequency.

  3. Improved Therapeutic Efficacy: Prolonged gastric retention allows better management of chronic diseases, ensuring a more consistent drug concentration in the bloodstream.

Mechanisms for Gastroretention:

  1. Floating Systems: These formulations are buoyant and float on the gastric fluid, maintaining contact with the stomach lining.

  2. Swelling Systems: These systems expand upon contact with gastric fluid, preventing them from passing through the pylorus.

  3. Bioadhesive Systems: These systems adhere to the gastric mucosa, prolonging gastric retention.

  4. High-Density Systems: These systems remain in the stomach due to their weight, as they sink and settle in the gastric cavity.

Applications:

  • Drugs like metformin, levodopa, and ciprofloxacin benefit from gastroretentive systems as they have limited absorption in the small intestine and upper GI tract.
  • Drugs with a short half-life or those that are highly soluble in the acidic gastric environment can be released in a controlled manner, optimizing therapeutic outcomes.

Overall, GRDDS enhances the therapeutic benefits of drugs requiring specific absorption sites, improves patient compliance, and reduces side effects by maintaining steady plasma drug concentrations.