Polymeric coating for reducing the rate of release of a therapeutic substance from a stent

Abstract

A stent for delivery of a therapeutic agent is disclosed. The stent includes a polymer coating for reducing the rate of release of the therapeutic agent. The polymer has a crystalline structure wherein the polymer is capable of significantly maintaining the crystalline lattice structure while the therapeutic agent is released from the stent such that the aqueous environment to which the stent is exposed subsequent to the implantation of the stent does not significantly convert the crystalline lattice structure of the polymer to an amorphous structure.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This is a divisional application of U.S. application Ser. No. 09 / 948,513, filed on Sep. 7, 2001, the teachings of which are incorporated herein in their entirety by reference.BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] A medical device, such as a stent, for delivering a therapeutic substance is disclosed. The stent includes a polymeric coating for reducing the rate of release of the therapeutic substance.

[0004] 2. Description of the Background

[0005] Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of the passageway. Typically stents are capable of being compressed, so that they can be inserted through small lumens via catheters, and then expanded to a larger diameter once they are at the desired location. Examples in the patent...

Examples

example 1

[0042] A 2% (w / w) solution of EVAL in dimethylacetamide (DMAC) is applied to a 13 mm Tetra™ stent (available from Guidant Corporation) using an EFD 780S spray device (available from EFD Inc., East Providence, R.I.) until 50 micrograms of solids have been deposited onto the stent. The stent is baked at 140° C. for 60 minutes to form a primer layer on the stent. A solution of 1:9 (w / w) actinomycin D:EVAL and 2% (w / w) EVAL in DMAC is sprayed onto the primered stent until 100 micrograms of solids have been deposited. The stent is baked at 50° C. for 2 hours to form an actinomycin D-containing reservoir coating. A 2% (w / w) polyvinylidene fluoride solution in DMAC is sprayed until 300 micrograms of solids have been deposited onto the stent. The stent is baked at 50° C. for 2 hours to form a crystalline rate-reducing membrane of polyvinylidene fluoride.

example 2

[0043] A 2% (w / w) solution of EVAL in DMAC is applied to a 13 mm Tetra™ stent using an EFD 780S spray device until 50 micrograms of solids have been deposited onto the stent. The stent is baked at 140° C. for 60 minutes to form a primer layer on the stent. A solution of 1:3 (w / w) dexamethasone:poly(ethylene-co-vinyl-acetate) and 2% (w / w) polyethylene-co-vinyl-acetate) in cyclohexanone is sprayed onto the primered stent until 300 micrograms of solids have been deposited. The stent is baked at 60° C. for 2 hours to form a dexamethasone-containing reservoir coating. A 2% (w / w) KRATON G1650 (available from KRATON™ Polymers, Houston, Tex.) solution in xylene is sprayed until 300 micrograms of solids have been deposited onto the stent. The stent is baked at 60° C. for 2 hours to form a crystalline rate-reducing membrane of KRATON G1650.

example 3

[0044] A 2% (w / w) solution of EVAL in DMAC is applied to a 13 mm Tetra™ stent using an EFD 780S spray device until 50 micrograms of solids have been deposited onto the stent. The stent is baked at 140° C. for 60 minutes to form a primer layer on the stent. A solution of 1:2 (w / w) estradiol:EVAL and 2% (w / w) EVAL in DMAC is sprayed onto the primered stent until 350 micrograms of solids have been deposited. The stent is baked at 60° C. for 2 hours to form an estradiol-containing reservoir coating. A 2% (w / w) poly(vinylidene fluoride-co-hexafluoropropene) solution in 1:1 (w / w) acetone:DMAC is sprayed until 300 micrograms of solids have been deposited onto the stent. The stent is baked at 60° C. for 2 hours to form a crystalline rate-reducing membrane of poly(vinylidene fluoride-co-hexafluoropropene).

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This is a divisional application of U.S. application Ser. No. 09 / 948,513, filed on Sep. 7, 2001, the teachings of which are incorporated herein in their entirety by reference.BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] A medical device, such as a stent, for delivering a therapeutic substance is disclosed. The stent includes a polymeric coating for reducing the rate of release of the therapeutic substance.

[0004] 2. Description of the Background

[0005] Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of the passageway. Typically stents are capable of being compressed, so that they can be inserted through small lumens via catheters, and then expanded to a larger diameter once they are at the desired location. Examples in the patent...

Examples

example 1

[0042] A 2% (w / w) solution of EVAL in dimethylacetamide (DMAC) is applied to a 13 mm Tetra™ stent (available from Guidant Corporation) using an EFD 780S spray device (available from EFD Inc., East Providence, R.I.) until 50 micrograms of solids have been deposited onto the stent. The stent is baked at 140° C. for 60 minutes to form a primer layer on the stent. A solution of 1:9 (w / w) actinomycin D:EVAL and 2% (w / w) EVAL in DMAC is sprayed onto the primered stent until 100 micrograms of solids have been deposited. The stent is baked at 50° C. for 2 hours to form an actinomycin D-containing reservoir coating. A 2% (w / w) polyvinylidene fluoride solution in DMAC is sprayed until 300 micrograms of solids have been deposited onto the stent. The stent is baked at 50° C. for 2 hours to form a crystalline rate-reducing membrane of polyvinylidene fluoride.

example 2

[0043] A 2% (w / w) solution of EVAL in DMAC is applied to a 13 mm Tetra™ stent using an EFD 780S spray device until 50 micrograms of solids have been deposited onto the stent. The stent is baked at 140° C. for 60 minutes to form a primer layer on the stent. A solution of 1:3 (w / w) dexamethasone:poly(ethylene-co-vinyl-acetate) and 2% (w / w) polyethylene-co-vinyl-acetate) in cyclohexanone is sprayed onto the primered stent until 300 micrograms of solids have been deposited. The stent is baked at 60° C. for 2 hours to form a dexamethasone-containing reservoir coating. A 2% (w / w) KRATON G1650 (available from KRATON™ Polymers, Houston, Tex.) solution in xylene is sprayed until 300 micrograms of solids have been deposited onto the stent. The stent is baked at 60° C. for 2 hours to form a crystalline rate-reducing membrane of KRATON G1650.

example 3

[0044] A 2% (w / w) solution of EVAL in DMAC is applied to a 13 mm Tetra™ stent using an EFD 780S spray device until 50 micrograms of solids have been deposited onto the stent. The stent is baked at 140° C. for 60 minutes to form a primer layer on the stent. A solution of 1:2 (w / w) estradiol:EVAL and 2% (w / w) EVAL in DMAC is sprayed onto the primered stent until 350 micrograms of solids have been deposited. The stent is baked at 60° C. for 2 hours to form an estradiol-containing reservoir coating. A 2% (w / w) poly(vinylidene fluoride-co-hexafluoropropene) solution in 1:1 (w / w) acetone:DMAC is sprayed until 300 micrograms of solids have been deposited onto the stent. The stent is baked at 60° C. for 2 hours to form a crystalline rate-reducing membrane of poly(vinylidene fluoride-co-hexafluoropropene).