| abstract |
A multi solvent drug delivery matrix formation method is used to place layers into a reservoir in a stent in a stepwise manner to achieve extended delivery of water soluble, sensitive, or difficult to deliver drugs. The multi solvent matrix formation method allows the formation of a drug reservoir with a layered morphology in which the mixing between layers is limited to allow the different layers to perform different functions in controlling drug delivery. A stent having a drug delivery matrix includes a first beneficial agent layer affixed to the stent by depositing a first solution of a first polymer and a first solvent, and a second beneficial agent layer affixed to the first beneficial agent layer by depositing a second solution of a second polymer and a second solvent. The second solvent is selected so that the first polymer is substantially insoluble in the second solvent to prevent degradation of the first polymer during deposition of the second polymer. A therapeutic agent is provided in the first beneficial agent layer or the second beneficial agent layer to form a drug delivery matrix. |