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Stent

a technology of stents and polymers, applied in the field of stents, can solve the problems of stents used alone not being able to effectively prevent restenosis, decomposition or degradation of therapeutic substances (biologically/physiologically active substances) incorporated in polymers, and achieve the effect of stable loading

Inactive Publication Date: 2003-09-25
TERUMO KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] It is an object of the present invention to provide a stent capable of stably loading a biologically / physiologically active substance, without causing its decomposition and deterioration, and permitting it to release itself slowly over a long period of time without being rapidly released in a short period, after implanted in a lesion.

Problems solved by technology

The disadvantage of this procedure is that there is a possibility of the catheter damaging the vascular wall.
However, it has turned out that any stent used alone cannot effectively prevent restenosis.
Regrettably, the stent proposed in JP 8-33718 A has the disadvantage that the therapeutical substance (biologically / physiological-ly active substance) incorporated in the polymer is decomposed or deteriorated by chemical reactions between them.
On the other hand, because of its tendency to liberate an acid upon decomposition, polylactic acid deteriorates the biologically / physiologically active substance which might have a weak acid resistance.
Moreover, when a readily biodegradable polymer is selected, it permits the biologically / physiologically active substance to release itself in a short period (several days after implanted), resulting in making the stent unable to prevent restenosis sufficiently.
In other words, the stent proposed in JP 8-33718 A, which is so designed as to prevent the biologically / physiologically active substance from decomposition and deterioration and to permit the biologically / physiologi-cally active substance to release itself over a long period of time (several weeks to several months after implanted), has the disadvantage that the range of selection of the biologically / physiologically active substance is limited by combination with the polymer.
Nevertheless, it still has a drawback resulting from the fact that the layer of the biologically / physiologicall-y active substance is covered with a porous polymer layer.
Moreover, it is liable to cause the phenomenon that biologically / physiologically active substance is released rapidly in a short period (several days after implanted) after it has been implanted at the lesion, namely the initial burst.
Thus, the above-mentioned stent presents difficulties in permitting the biologically / physiologically active substance to release itself slowly over a long period of time (several weeks to several months after implanted).

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0101] A polymer film having a thickness of 30 .mu.m was prepared by casting in a petri dish from a hexane solution of two-pack silicone elastomer (10 wt % in concentration) incorporated with PTFE fine particles (not larger than 1 .mu.m in particle diameter). The two-pack silicone elastomer is "Q7-4840 Silastic" (from Dow Corning Corporation) consisting of solution-A and solution-B in equal quantities. The amount of the PTFE is 30 wt % on the total amount of the polymer in the silicone elastomer and the PTFE fine particles.

[0102] The thus obtained polymer film was placed at the intermediate part 6 of two chambers 7 and 8 of the apparatus shown in FIG. 5. One chamber 7 of the apparatus was filled with an aqueous solution of simvastatin (SVS) which had been filtered off through a 0.45 .mu.m thick membrane filter made by Advantec. The aqueous solution contains 50 .mu.g / ml conc. of SVS and 2 wt % of surfactant ("Tween 20" from Nikko Chemical Co, . Ltd.). The other chamber 8 was filled w...

example 2

[0103] A polymer film having a thickness of 30 .mu.m was prepared by casting in a petri dish from a hexane solution of two-pack silicone elastomer (10 wt % in consentration) incorporated with sodium chloride fine particles (not larger than 1 .mu.m in particle diameter). The two-pack silicone elastomer is "Q7-4840 Silastic" (from Dow Corning Corporation) consisting of solution-A and solution-B in equal quantities. The amount of sodium chloride is 0.25 wt % on the total amount of the polymer in the silicone elastomer and the sodium chloride fine particles. The thus obtained polymer film was measured for the rate of permeation of SVS in the same way as in Example 1. The results of the test are shown in Table 1.

example 3

[0107] A stent sample was prepared in the following manner from a stent main body which is in a cylindrical shape (1.8 mm in outside diameter and 15 mm long, having approximately rhombic holes) and is composed of fibrous members (0.1 mm in diameter) of stainless steel (SUS 316L), as shown in FIG. 1. This stent main body was sprayed with a hexane solution of SVS (5 wt % in concentration) by using a hand spray (HP-C made by Iwata Corporation). It was confirmed that the surface of the fibrous members constituting the stent main body was coated with about 200 .mu.g of SVS. Upon complete solvent (hexane) removal by evaporation, there was formed a layer of SVS (biologically / physiologically active substance) on the surface of the fibrous members constituting the stent main body.

[0108] The coated stent main body was sprayed with a hexane solution of two-pack silicone elastomer incorporated (2 wt % in concentration) with PTFE fine particles (not larger than 1 .mu.m in particle diameter). The...

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Abstract

A stent capable of stably loading a biologically / physiologically active substance, without causing its decomposition or deterioration, and permitting it to release itself slowly over a long period of time without being rapidly released in a short period, after being implanted in a lesion. The stent (1) comprises a cylindrical stent main body (2) having an opening on each end and extending in axial direction between the two openings, and a sustained release coating formed on the surface of said stent main body from which a biologically / physiologically active substance is released, and wherein said sustained release coating is composed of a layer of a biologically / physiologically active substance (3) which covers the surface of said stent main body, and a polymer layer (4) which covers said layer of a biologically / physiologically active substance (3) on said layer of a biologically / physiologically active substance (3), and said layer of a biologically / physiologically active substance (3) contains at least one kind of fat-soluble biologically / physiologically active substance, and said polymer layer (4) contains a polymer miscible with said biologically / physiologically active substance and fine particles (5) equal to or smaller than 5 mum in particle diameter dispersed in the polymer.

Description

[0001] The present invention relates to a stent which is designed to be implanted in a stenotic or occluded lesion that has occurred in such ducts of a living body as blood vessel, bile duct, trachea, esophagus, and urethra, thereby keeping the lesion open. More particularly, the present invention relates to a stent which slowly releases from its surface over a long period of time a biologically / physiologically active substance effective in preventing restenosis, thereby keeping open the lesion over a long period of time.[0002] The following provides some background to the present invention with reference to angioplasty applied to ischemic heart disease.[0003] The diffusion of westernized diets in Japan has steeply increased patients suffering from ischemic heart diseases (angina pectoris, cardiac infarction). Among new remedies against such heart diseases is percutaneous transluminal coronary angioplasty (PTCA), which is gaining general acceptance rapidly. It has matured technicall...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): A61L31/10A61M29/00A61L31/16
CPCA61L31/10A61L2300/608A61L2300/602A61L31/16A61M29/00
Inventor ISHII, NAOKITOGAWA, HIDEYUKI
Owner TERUMO KK
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