A medical device for placement in a body of a mammal is provided. The medical device comprises (1) a polymeric matrix forming the device and defining a lumen through the device, the matrix comprising polymer macromolecules and defining spaces between the polymer macromolecules; (2) a drug contained within at least some of the spaces of the matrix; and (3) a material contained within at least some of the spaces of the matrix to affect diffusion of the drug out of the polymeric matrix when the medical device is placed in the boy of the mammal.