Gastro-Retentive Drug Delivery Systems (GRDDS) aim to prolong and control drug release in the stomach, improving therapeutic efficacy and bioavailability for drugs with a narrow absorption window in the upper gastrointestinal (GI) tract.
Floating Systems
Mechanism:
Dosage forms with lower density than gastric fluids float on the stomach contents, remaining buoyant until the drug is released.
Key Components:
Polymers: Hydroxypropyl methylcellulose (HPMC), ethylcellulose.
Gas-Generating Agents: Sodium bicarbonate, citric acid (produce CO₂ for buoyancy).
Types:
Effervescent Systems: Generate CO₂ to float (e.g., tablets with bicarbonate and acid).
Non-Effervescent Systems: Rely on polymer swelling for buoyancy.
Applications:
Drugs acting in the stomach (e.g., antacids).
Drugs absorbed from the stomach (e.g., levodopa).
Drugs with narrow absorption windows in the upper intestine (e.g., furosemide).
High-Density Systems
Mechanism:
Dosage forms sink to the bottom of the stomach due to higher density (>1.5 g/cm³) and remain there.
Key Components:
High-density materials like barium sulfate, zinc oxide.
Applications:
Drugs causing gastric irritation (keep away from sensitive areas).
Drugs acting locally in the stomach.
Drugs absorbed in the upper intestine.
Inflatable Systems
Mechanism:
Expand in the stomach to prevent passing through the pyloric sphincter, ensuring prolonged retention.
Key Components:
Drug core with an inflatable shell containing gas-generating agents (e.g., sodium bicarbonate).
Types:
Balloon Systems: Inflate in the stomach for buoyancy.
Collapsible Capsules: Inflated chamber seals the drug reservoir.
Applications:
Drugs absorbed in the stomach or upper intestine.
Controlled drug release with extended therapeutic effects.
Gastroadhesive (Bioadhesive) Systems
Mechanism:
Adhere to the gastric mucosa using bioadhesive polymers, prolonging gastric residence time.
Key Components:
Bioadhesive polymers: HPMC, chitosan, poly(acrylic acid), carbopol.
Types:
Bioadhesive Tablets: Traditional tablets with adhesive properties.
Films or Patches: Thin adhesive layers applied to the gastric mucosa.
Micro/Nanoparticles: Small particles with bioadhesive capabilities.
Applications:
Localized action (e.g., for ulcers).
Drugs with narrow absorption.