Drug delivery systems developed to prolong the gastric residence time

Abstract

Introduction. The drug that are only absorbed from a certain portion of gastrointestinal tract or have absorption differences in a certain portion of GIT have regional variability in intestinal absorption. Absorption window can limit the bioavailability of the drug after oral administration and the development of controlled release formulations is in some cases difficult [1, 2]. Aim. There are various methods of increasing the maintenance of formulations of the drug at/or above the absorption window in order to improve the bioavailability, suitable for active principles which exhibit gastric absorption, that are intended for local action in the stomach, that have a narrow GIT absorption window, a low solubility at high pH, that are unstable in the intestinal environment, or they are instantly absorbed from GIT [2, 3]. Materials and Methods. The dosage forms with gastric retention are drug delivery systems that remain in the stomach for an extended period of time. There are two different types of GRDDS, floating and non-floating systems. The floating systems may be effervescent: gas-generating or with volatile liquid; the non-effervescent may be hydrodynamically balanced systems, microballoons and alginate beads. The non-floating GRDDS include raft-forming, bioadhesive, expandable, high density or magnetic systems [1-4]. Results. The gastric retention is influenced by the gastric motility, pH and by the presence of food in stomach. The bioavailability is unpredictable due to the risk of elimination of system from the stomach too rapidly, or even the possibility of permanent retention of the dosage form. Conclusion. Since these drug delivery systems present advantages and limitations, in order to design a successful GRDDS it is necessary to consider the physico-chemical properties of the drug, the physiological particularities of the GIT, the formulation strategies and the association of the active principle with different excipients.