Medical device polymer

A medical device at least a portion of which comprises:

• a body insertable into a patient, said body having an exposed surface which is adapted for exposure to tissue of a patient and constructed to release, at a predetermined rate, a therapeutic agent adapted to inhibit adverse physiological reaction of said tissue to the presence of the body of said medical device,
• said therapeutic agent selected from the group consisting of antithrombogenic agents, antiplatelet agents, prostaglandins, thrombolytic drugs, antiproliferative drugs, antirejection drugs, antimicrobial drugs, growth factors, and anticalcifying agents,
• at said exposed surface, said body including:
• an outer polymer metering layer, and
• an internal polymer layer underlying and supporting said outer polymer metering layer and in intimate contact therewith, said internal polymer layer defining a reservoir for said therapeutic agent,
• said reservoir formed by a polymer selected from the group consisting of polyurethanes and its copolymers, silicone and its copolymers, ethylene vinylacetate, thermoplastic elastomers, polyvinylchloride, polyolefins, cellulosics, polyamides, polytetrafluoroethylenes, polyesters, polycarbonates, polysulfones, acrylics, and acrylonitrile butadiene styrene copolymers,
• said outer polymer metering layer having a stable, substantially uniform, predetermined thickness covering the underlying reservoir so that no portion of the reservoir is directly exposed to body fluids and incorporating a distribution of an elutable component which, upon exposure to body fluid, elutes from said outer polymer metering layer to form a predetermined porous network capable of exposing said therapeutic agent in said reservoir in said internal polymer layer to said body fluid,
• said elutable component is selected from the group consisting of polyethylene oxide, polyethylene glycol, polyethylene oxide/polypropylene oxide copolymers, polyhydroxyethylmethacrylate, polyvinylpyrollidone, polyacrylamide and its copolymers, liposomes, albumin, dextran, proteins, peptides, polysaccharides, polylactides, polygalactides, polyanhydrides, polyorthoesters and their copolymers, and soluble cellulosics,
• said reservoir defined by said internal polymer layer incorporating said therapeutic agent in a manner that permits substantially free outward release of said therapeutic agent from said reservoir into said porous network of said outer polymer metering layer as said elutable component elutes from said polymer metering layer, said predetermined thickness and the concentration and particle size of said elutable component being selected to enable said outer polymer metering layer to meter the rate of outward migration of the therapeutic agent from said internal reservoir layer through said outer polymer metering layer.
• said outer polymer metering layer and said internal polymer layer, in combination, enabling prolonged controlled release, at said predetermined rate, of said therapeutic agent at an effective dosage level from said exposed surface of said body of said medical device to the tissue of said patient to inhibit adverse reaction of the patient to the prolonged presence of said body of said medical device in said patient.