Expandable Systems

  This review explains the recent advances in gastroretentive drug delivery systems with special focus on floating drug delivery systems. Oral controlled release (CR) dosage forms (DF) have been extensively used to improve therapy of many important medications. However, in the case of narrow absorption window drugs, this pharmaceutical approach cannot be utilized, as it requires sufficient colonic absorption of the drug (which contradicts the definition of narrow absorption window agents). On the other hand, incorporation of the drug into a CR delivery system, which releases its payload in the stomach over a prolonged time period, can lead to significant therapeutic advantages owing to various pharmacokinetic (PK) and pharmacodynamic aspects. Gastroretentive dosage forms (GRDFs) are a drug delivery formulation that are designed to be retained in the stomach for a prolonged time and release there their active materials and thereby enable sustained and prolonged input of the drug to the upper part of the gastrointestinal (GI) tract. This technology has generated enormous attention over the last few decades owing to its potential application to improve the oral delivery of some important drugs for which prolonged retention in the upper GI tract can greatly improve their oral bioavailability and/or their therapeutic outcome. This article reviews some of the latest developments in GRDF technology from a pharmaceutical point of view. It also highlights the PK and/or pharmacodynamic rationale for the development of GRDFs for certain drugs that are either absorbed in the upper GI tract or have local activity there.   Key words: Floating drug delivery systems, single unit, multiple units, gastric resident time, Expandable Systems