IN-VIVO EVALUATION OF A NOVEL GASTRIC RETENTIVE FORMULATION BASED ON ION-EXCHANGE RESINS

Systems that exhibit gastric retention are of value in several areas o f therapy. A novel floating system based on ion exchange resins has be en investigated and evaluated in vivo. The method relies on ion exchan ge resins loaded with bicarbonate, which, on contact with media contai ning hydrochloric acid, release carbon dioxide causing the resin to fl oat. Extension of the floating time is achieved by coating the bicarbo nate loaded resin particles with a semipermeable membrane. Two resins were investigated and both exhibited in vitro floating times of over 2 4 h using a standardised procedure. Studies in human volunteers were c arried out using gamma scintigraphy. The coated resins were compared t o an uncoated control in subjects receiving a light breakfast. The coa ted resin based on Dowex 2X10 showed significantly prolonged residence times (P < 0.002) over the non-coated control when compared at 60 and 150 min using a modified gastric emptying index.