In recent years scientific and technological advancements have been made in the research and development of oral drug delivery system. The reasons that the oral route achieved such popularity may be in part attributed to its ease of administration. Oral sustained drug delivery system is complicated by limited gastric residence times (GRTs). To overcome these limitations, various approaches have been proposed to increase gastric residence of drug delivery systems in the upper part of the gastrointestinal tract which includes floating drug dosage systems (FDDS), effervescent and non effervescent system, swelling or expanding systems, mucoadhesive systems magnetic systems, modified-shape systems, high density system and other delayed gastric emptying devices. Among these systems, FDDS have been most commonly used.