a coating and method for a coating an implantable device or prostheses are disclosed . the coating includes an undercoat of polymeric material containing an amount of biologically active material , particularly heparin , dispersed therein . the coating further includes a topcoat which covers less than the entire surface of the undercoat and wherein the topcoat comprises a polymeric material substantially free of pores and porosigens . the polymeric material of the topcoat can be a biostable , biocompatible material which provides long term non - thrombogenicity to the device portion during and after release of the biologically active material .