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.