Abstract: A sustained release diltiazem formulation for oral administration comprising a pellet having a central sugar sphere a plurality of alternating first and second layers surrounding the sphere to form a core, the first layer comprising a water soluble pharmaceutically acceptable polymeric material and the second layer comprising diltiazem or a pharmaceutically acceptable salt thereof and an outer membrane surrounding the plurality of layers. The outer membrane comprises first inner membrane layers of ethylcellulose. The outer membrane also comprises an outer membrane coating of a water insoluble pharmaceutically acceptable polymeric material, a plasticizer and a lubricant, in from one to five or more layers.