Drug coating with topcoat

Abstract

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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a Continuation-In-Part of co-pending application Ser. No. 08 / 633,518, filed Jun. 13, 1996.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to providing biostable elastomeric coatings on the surfaces of implants which incorporate biologically active species having controlled release characteristics in the coating and relates particularly to providing a non-thrombogenic surface during and after timed release of the biologically active species. The invention is particularly described in terms of coatings on therapeutic expandable stent prostheses for implantation in body lumens, e.g., vascular implantation. [0004] 2. Related Art [0005] In surgical or other related invasive procedures, the insertion and expansion of stent devices in blood vessels, urinary tracts or other locations difficult to otherwise access for the purpose of preventing restenosis, prov...

AI Technical Summary

Benefits of technology

The present invention provides a thin layered coating for prostheses, such as stents, that contains a biologically active material dispersed in a polymer material. The coating is applied as a mixture of polymer material and the biologically active material in a solvent or solvents. The coating is designed to be applied to self-expanding stents and is preferably a non-thrombogenic surface. The coating is made up of layers that can be applied sequentially, with the topcoat being a non-connected porous membrane. The thickness ratio of the topcoat to the undercoat can vary, but it should cover less than the entire surface of the undercoat. The topcoat should cover only about 10% to about 95% of the surface of the undercoat. The coating can be applied using evaporative solvents and has good adhesion to the stent. The coating can be cured at room temperature or at elevated temperatures. The technical effect of this invention is to provide a thin coating that can contain a biologically active material and a non-thrombogenic surface for prostheses such as stents.

Problems solved by technology

Moreover, drug elution rates for a coating containing a hydrophilic or a lipophobic drug is usually very fast initially when the coated device contacts body fluid or blood.

Even though the method might be quite successful to control the drug release, it increases the coating thickness, reduces the effective drug loading and introduces undesirable additional foreign materials into the patient.

With regard to stents, polymeric stents, although effective, may have mechanical properties that are inferior to those of metal stents of like thickness and weave.

A polymer material of comparable strength requires a much thicker-walled structure or heavier, denser filament weave, which in turn, reduces the cross-sectional area available for flow through the stent and / or reduces the relative amount of open space in the weave.

Also, it is usually more difficult to load and deliver polymeric stents using catheter delivery systems.

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