الفهرس 
English Cover
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Abstract
Sustained release (SR) dosage forms proposemany advantages such as; patient convenience, decreasing dose frequency and improved safety. Moreover, SR dosage forms are considered more economic as they allow reduction of the total amount of drug administered per day. Osmotic devices are the most promising strategy based systems for sustained drug delivery.The osmotic pump tablet is an advanced technology of drugdelivery systems that uses osmotic pressure as the driving force to deliver pharmacotherapy.The major formulation components of a typical osmotic delivery system include drug, osmotic agent, osmotic components, semipermeable membrane forming polymers, plasticizers. Example of osmotic pump tablets is the controlled porosity osmotic pump. A Freely soluble model drug, Metformin Hydrochloride,was selected for developing an osmotic pump system. It is a potent oral antidiabetic drug. According to the Biopharmaceutical Classification System (BCS), Metformin HCl belongs to Class III drugs (high solubility and low permeability). It has an absolute oral bioavailability between 50% and 60%. Metformin HCl is considered a good candidate for sustained releaseformulations due to its relatively shortand variable half-life (t {u00BD} =1.5- 4h) as well as the side effects encountered with its frequent high dose administration (500-1000mg)