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 of therapy. A novel floating system based on ion exchange resins has been investigated and evaluated in vivo. The method relies on ion exchange resins loaded with bicarbonate, which, on contact with media containing hydrochloric acid, release carbon dioxide causing the resin to float. Extension of the floating time is achieved by coating the bicarbonate loaded resin particles with a semipermeable membrane. Two resins were investigated and both exhibited in vitro floating times of over 24 h using a standardised procedure. Studies in human volunteers were carried out using gamma scintigraphy. The coated resins were compared to an uncoated control in subjects receiving a light breakfast. The coated resin based on Dowex 2 x 10 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.