Introduction: A sustained-release dosage form is defined as "any drug or dosage form modification that prolongs the therapeutic activity of the drug" [1]. The goal of sustained release dosage form is to maintain therapeutic blood or tissue level of drug for extended period of time. This is generally accomplished by attempting to obtain zero-order release from dosage form, but actually sustained release usually try to mimic zero-order release by providing drug in slow first order. Sustained release dosage form is most applicable for drugs having low therapeutic indices and short