Methods, coatings and coated medical devices are provided, wherein a plasma-deposited aliphatic polymerized hydrocyclosiloxane membrane is deposited as a diffusion control barrier for a drug deliver component consisting of one or more therapeutic agents coated on a surface or contained within a matrix, preferably a polymeric matrix, coated on a surface. The plasma-polymerized hydrocyclosiloxane membrane coats all or substantially all of the drug delivery component in contact or communication with the exterior surface, such that all or substantially all of any drug or therapeutic agent must diffuse across the membrane in order to be released.
