ABSTRACT:
The popularity and patient compliance of the oral drug delivery route encourages the modern forms of oral dosage forms which are more beneficiary. These include oro-dispersible tablets, controlled release tablets, effervescent and non effervescent gastro retentive floating tablets. Among these, gastro retentive tablets have prominent role in delivery of drugs with constraints such as drugs having absorption window, those absorbed locally from the upper GI tract region, and those with relatively short half-lives. But conventional dosage forms like tablets are losing their integrity due to multiple dosage regimens. Gastro retentive systems overcome these constraints and enable a delivery strategy that will function irrespective of the digestive state, clinical condition, or GI motility of the patient. In addition, longer residence time in the stomach could be advantageous in ensuring local action in the upper part of the small intestine, for example in the treatment of peptic ulcer disease and localized stomach cancers. Furthermore, improved bioavailability is expected for drugs that are absorbed readily upon release in the GI tract, primarily those absorbed from the proximal small bowel. These drugs can be delivered ideally by slow release from the stomach. Various scientific and technological attempts have been made in the development of gastroretentive dosage forms to overcome several physiological adversities, such as short gastric retention time and unpredictable gastric emptying time. Floating microspheres are the gastroretentive dosage forms are able to uniform drug release at a site for an extended period of time. The porosity has an important effect on drug release characteristics and pores may greatly increase the rate of drug expulsion and also floating property. This review highlights the classification, factors, mechanism of floating of microspheres, characterization, preparation method, development, polymers, applications, in-vitro, in vivo drug release studies and the effect of porosity on the drug release.