Floating drug delivery systems (FDDS) have a bulk density less than gastric fluids and so remain buoyant in stomach without affecting the gastric emptying rate for a prolonged period of time. While the system is floating on the gastric contents, drug is released slowly at a desired rate from the system. After release of drug, the residual system is emptied from the stomach. This results in an increased Gastric Residence Time (GRT) and a better control of fluctuations in plasma drug concentration. The system must have sufficient structure to form a cohesive gel barrier to maintain an overall specific gravity lower than that of gastric contents and to dissolve slowly enough to serve as a drug reservoir. Based on the mechanism of buoyancy, two distinctly different technologies, i.e. noneffervescent and effervescent systems, have been utilized in the development of FDDS.