Preparation of floating alginate gel beads for drug delivery to the gastric mucosa.

Alginate gel beads containing ethylcellulose (ALECs) were prepared and investigated with regard to buoyancy, in vitro and in vivo drug release profiles, and drug targeting specificity in the gastric mucosa. When the ethylcellulose (EC) content of ALECs containing metronidazole (MZ) was higher than 3%, the beads floated in all test solutions with a specific gravity of approx. 1.01. ALECs containing 5% EC released MZ gradually and floated throughout the experimental period in simulated gastric juice (pH 1.2), and all of the drug had been released after 90 min. When we orally administered ALECs to guinea pigs, about 85% of the incorporated MZ was released at 1 h. The MZ concentration of the gastric mucosa after administration of ALECs was greater than that observed with administration of MZ solution, despite lower serum concentrations. Furthermore, the similar data were obtained for ALECs with 7% EC. These results suggest that ALECs may become a practical vehicle for delivering drugs to the gastric mucosa.