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Sustained release drug formulations contain the pharmaceutical itself and a three component release rate controlling matrix composition. The three components of the matrix composition are (1) water insoluble polymer, such as ethyl cellulose,(2) pH dependent gelling polymer, such as sodium alginate, and (3) a pH independent gelling polymer, such as hydroxypropyl methylcellulose. The drug release rate can be adjusted by changing the amount of one or more of these components of the composition.