الفهرس 
Formulation of some modified release oral dosage forms
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Abstract
Transit time through the gastrointestinal tract (GIT) is a major factor that impacts the effectiveness of modified release (MR) dosage forms as it directly influences the site of drug release. Thus, even though the slow release can be achieved, the drug released after passing the absorption site is not fully utilized because the gastric retention time (GRT) is less than 12 hours. Therefore it is not possible to deliver the drug for more than 12 hours through the oral route. Thus gastro-retentive drug delivery systems (GRDDS) offer numerous advantages especially for drugs exhibiting an absorption window in the proximal small intestine like riboflavin (RF). Different techniques have been explored to increase gastric retention including bio-adhesive systems, high density systems, expandable systems, magnetic systems and floating systems. Floating systems could remain buoyant in the stomach for a prolonged period of time with a potential continuous release of the drug. Hollow microspheres (microballoons) are considered one of the most promising floating systems because they possess the advantages of multiple - unit systems and better floating properties as a result of the central hollow space inside them