Method of producing a drug delivery system, comprising the steps of: (a) selecting a first drug substance； (b) depositing the first drug substance on at least one area of the surface of a medical device in order to form a first layer of deposited drug； (c) forming a first beam of gas cluster ions in a vacuum chamber； (d) positioning at least one area of the surface of the medical device in the vacuum chamber for irradiation by the first beam of gas cluster ions； (e) irradiating the first drug layer deposited with the first gas cluster ion beam in order to adhere a drug layer to at least one area of the surface of the medical device such that a section of the deposited drug substance can be released from the first layer of drug adhered to at a first expected rate； wherein the adhered drug layer comprises at least one carbonized matrix formed by a section of the first deposited drug layer and which includes a plurality of interstices within which an uncarbonized section of the first deposited drug layer is disposed, a plurality of the interstices being open on a surface of the carbonized matrix in order to allow the release of the uncarbonized section of the first drug layer deposited at the expected rate； and wherein at least one layer of adhered drug further comprises another non-carbonized section of the first deposited drug layer that is encapsulated between the carbonized matrix and at least one surface area of the medical device； (f) select an additional pharmacological substance； (g) depositing the additional drug substance as an additional drug layer in the more recently adhered drug layer； (h) irradiating the additional drug layer with an additional gas cluster ion beam in order to adhere the additional drug layer onto the more recently adhered drug layer such that a section of the drug substance is allowed Additional deposited is released from the additional drug layer adhered to an additional expected rate； and (i) optionally repeating steps (f) to (i) to f
