In a method for producing a medical device capable of inhibiting the aggregation of platelets from blood flowing in a living being resulting from exposure of the blood to a medical device by coating the surface of the foreign body prior to contact therewith, with a physiologically acceptable polymer coating which contains dissolved or dispersed therein a therapeutic drug, the improvement wherein the polymer coating is insoluble in the blood and has a porosity sufficiently small to inhibit diffusion of blood-borne reductants from entering the coating and sufficiently large to allow passive diffusion of nitric oxide from within the polymer coating into the blood stream of the living being and contains dissolved or dispersed therein as the therapeutic drug and the source of the nitric oxide an amount of a nitrosyl-containing organometallic compound, which slowly decomposes at body temperature within the polymer coating when the device is exposed to the blood stream of the living being and in so doing releases from the coating into the blood stream an amount of nitric oxide effective to inhibit platelet aggregation which would otherwise be promoted by contact of the blood with the foreign body.