Balloon catheter

Abstract

The present invention provides a balloon catheter in which a drug is held on the surface of the balloon, and which can efficiently deliver the drug to the inner wall of a body cavity, such as the wall of a blood vessel. [Solution] A balloon catheter equipped with a balloon 10, wherein a fluid-absorbing swelling layer 31 is provided on the outer surface of the balloon 10, and a drug layer 32 is provided on the outer surface of the fluid-absorbing swelling layer 31.

Description

Technical Field

[0005] ,

[0001] The present invention relates to a balloon catheter provided with a balloon having a drug held on its surface.

Background Art

[0002] It is known that various diseases occur when a stenosis occurs in a blood vessel, which is a flow path for blood circulation in the body, and the blood circulation is obstructed. In particular, when a stenosis occurs in the coronary artery that supplies blood to the heart, there is a risk of serious diseases such as angina pectoris and myocardial infarction. As one method for treating such a stenosis of a blood vessel, there is angioplasty (PTA, PTCA, etc.) in which a stenosis is expanded using a balloon catheter.

[0003] In angioplasty, restenosis may occur in the expanded stenosis. In order to reduce the frequency (restenosis rate) of such restenosis, a balloon catheter having a drug held on the surface of the balloon is known (for example, Patent Documents 1 to 4). By using such a balloon catheter having a drug held thereon, the drug can be transferred to the inner wall of a body cavity such as a blood vessel wall by expanding the balloon at a stenosis or a lesion of a body cavity such as a blood vessel, and suppression of the occurrence of restenosis and the like can be expected.

Prior Art Documents

Patent Documents

[0004] [[ID=​​​​​​​​​​​​​​​​​​​​​​​ In balloon catheters in which a drug is held on the surface of the balloon, it is desirable that the drug can be efficiently transferred to the internal wall of a body cavity, such as the blood vessel wall, when the balloon is expanded in a stenotic or lesional area. The present invention has been made in view of the above circumstances, and its object is to provide a balloon catheter in which a drug is held on the surface of the balloon, and which can efficiently transfer the drug to the internal wall of a body cavity, such as the blood vessel wall. [Means for solving the problem]

[0006] The balloon catheter of the present invention, which has been able to solve the aforementioned problems, is as follows. [1] A balloon catheter equipped with a balloon, A balloon catheter having a liquid-absorbing swelling layer on the outer surface of the balloon, and a drug layer on the outer surface of the liquid-absorbing swelling layer. [2] The balloon catheter according to [1], wherein a portion of the drug layer is in contact with the outer surface of the balloon. [3] The balloon catheter according to [1] or [2], wherein a crack is formed in the drug layer and the fluid-absorbing swelling layer enters the crack. [4] A balloon catheter according to any one of [1] to [3] wherein a portion of the outer surface of the fluid-absorbing swelling layer is not covered with the drug layer. [5] A balloon catheter according to any one of [1] to [4], wherein a protective layer is provided on the outer surface of the drug layer. [6] When the balloon is expanded, at least a portion of the fluid-absorbing swelling layer detaches from the balloon integrally with the drug contained in the drug layer, as described in any of [1] to [5]. [7] A balloon catheter according to any one of [1] to [6], wherein at least a portion of the fluid-absorbing swelling layer remains on the outer surface of the balloon when the balloon is expanded. [8] The balloon catheter according to any one of [1] to [7], wherein the drug layer comprises a drug in the form of elongated crystals. [9] The balloon catheter according to [8], wherein in the drug layer, a plurality of the elongated crystals are arranged radially to form a radial crystal group.

[10] The balloon catheter according to [9], wherein in a plan view from the radially outer side of the balloon, the major axis of the radial crystal group is 10 μm or more and 80 μm or less.

[11] The balloon catheter according to any one of [1] to

[10] , wherein the drug contained in the drug layer is paclitaxel. [Effects of the Invention]

[0007] The balloon catheter of the present invention has a fluid-absorbing and swelling layer on the outer surface of the balloon, and a drug layer on the outer surface of the fluid-absorbing and swelling layer. When the balloon is expanded, the fluid-absorbing and swelling layer comes into contact with body fluid, causing the fluid-absorbing and swelling layer to swell and the drug layer to easily detach from the balloon surface. This makes it easier to efficiently transfer the drug contained in the drug layer to the inner wall of a body cavity, such as the blood vessel wall. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows an example of the configuration of a balloon catheter according to an embodiment of the present invention, and represents a side view of the balloon catheter with the fluid-absorbing swelling layer and drug layer on the balloon surface removed. [Figure 2] Figure 1 shows a cross-sectional view of the balloon catheter at line II-II. [Figure 3] This shows a cross-sectional view (III-III) of the balloon catheter shown in Figure 1. [Figure 4] This figure shows a perspective view of the balloon attached to the balloon catheter shown in Figure 1. [Figure 5] Figure 4 shows a vertical cross-sectional view in the longitudinal direction of a balloon, which has a liquid-absorbing swelling layer and a drug layer on its surface. [Figure 6] Figure 5 shows an example of a partially enlarged cross-sectional view of the balloon. [Figure 7] This shows another example of a partially enlarged cross-sectional view of the balloon shown in Figure 5. [Figure 8]It represents another example of a partial enlarged cross-sectional view of the balloon shown in FIG. 5. [Figure 9] It represents another example of a partial enlarged cross-sectional view of the balloon shown in FIG. 5. [Figure 10] It represents another example of a partial enlarged cross-sectional view of the balloon shown in FIG. 5. [Figure 11] It represents another example of a partial enlarged cross-sectional view of the balloon shown in FIG. 5. [Figure 12] It represents an example of the folded state of the balloon and shows a vertical cross-sectional view of the folded balloon in the longitudinal axis direction. [Figure 13] It represents another example of the folded state of the balloon and shows a vertical cross-sectional view of the folded balloon in the longitudinal axis direction.

Embodiments for Carrying out the Invention

[0009] Hereinafter, the present invention will be specifically described based on the following embodiments. However, the present invention is not limited by the following embodiments, and it is of course possible to appropriately modify and implement it within the range that conforms to the gist of the foregoing and following descriptions, and all of them are included in the technical scope of the present invention. In each drawing, for the sake of convenience, hatching, member numbers, etc. may be omitted, but in such cases, reference shall be made to the specification and other drawings. Also, the dimensions of various members in the drawings may differ from the actual dimensions because priority is given to facilitating the understanding of the features of the present invention.

[0010] A configuration example of a balloon catheter according to an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 to 4 show a configuration example of a balloon catheter excluding the liquid-absorbing swelling layer and the drug layer of the balloon. FIG. 1 represents a side view of the balloon catheter, FIG. 2 represents a cross-sectional view taken along line II-II of the balloon catheter shown in FIG. 1, FIG. 3 represents a cross-sectional view taken along line III-III of the balloon catheter shown in FIG. 1, and FIG. 4 represents a perspective view of the balloon provided in the balloon catheter shown in FIG. 1. FIG. 1 shows a configuration example of a rapid exchange type balloon catheter.

[0011] The balloon catheter 1 has a balloon 10. Specifically, the balloon catheter 1 has a shaft 2 and a balloon 10 provided on the outside of the shaft 2. The balloon catheter 1 has a proximal end and a distal end, with the balloon 10 provided at the distal end of the shaft 2. The proximal end of the balloon catheter 1 refers to the direction toward the user (operator) relative to the extending direction of the balloon catheter 1, and the distal end refers to the opposite direction from the proximal end, i.e., the direction toward the target of treatment. The direction from the proximal end to the distal end of the balloon catheter 1 is also called the longitudinal axis direction.

[0012] The balloon catheter 1 is configured to supply fluid to the inside of the balloon 10 through the shaft 2, and the expansion and contraction of the balloon 10 can be controlled using an indefleror (balloon pressure / depressurization device). The fluid may be pressurized fluid pressurized by a pump or the like. Hereinafter, the fluid supplied to the inside of the balloon 10 will be referred to as the "balloon expansion fluid".

[0013] Shaft 2 is composed of, for example, an inner shaft 3 and an outer shaft 4. The inner shaft 3 is positioned within the lumen of the outer shaft 4. The inner shaft 3 can function as a passage for a guidewire that guides the advancement of shaft 2, and when using balloon catheter 1, the guidewire is inserted through the lumen of the inner shaft 3. The space between the inner shaft 3 and the outer shaft 4 can function as a passage for balloon inflation fluid.

[0014] In the rapid exchange type balloon catheter 1, a guidewire port 7 is provided midway from the distal to the proximal end of the shaft 2. The proximal end of the inner shaft 3 is connected to the guidewire port 7, and the distal end of the inner shaft 3 extends to the distal part of the shaft 2, thereby forming a guidewire insertion passage that extends from the guidewire port 7 to the distal part of the shaft 2.

[0015] The outer shaft 4 may have a proximal outer shaft 4A and a distal outer shaft 4B, in which case it is preferable that the inner shaft 3 is positioned in the lumen of the distal outer shaft 4B. The proximal outer shaft 4A and the distal outer shaft 4B may be made of the same material or of different materials. For example, it is preferable that the proximal outer shaft 4A is made of resin or metal and the distal outer shaft 4B is made of resin. The outer shaft 4 may not be divided into a proximal outer shaft 4A and a distal outer shaft 4B, but may be made of a single member, or the proximal outer shaft 4A and the distal outer shaft 4B may be further made up of multiple tube members.

[0016] It is preferable that a hub 5 is provided on the proximal side of the shaft 2. The hub 5 preferably has a fluid injection section 6 that communicates with the flow path of the balloon expansion fluid in the shaft 2. The balloon 10, shaft 2 (inner shaft 3, outer shaft 4), and hub 5 can be joined using conventionally known joining methods such as adhesives or heat welding.

[0017] Although not shown in the drawings, the balloon catheter may be an over-the-wire type balloon catheter in which the inner shaft extends from the distal to the proximal end of the shaft, and a guidewire insertion passage is formed from the distal to the proximal end of the shaft. In this case, it is preferable that the flow path for the balloon inflation fluid and the guidewire insertion passage provided in the shaft extend to the hub, and that the hub is configured to have a fluid injection section communicating with the flow path for the balloon inflation fluid and a treatment section communicating with the guidewire insertion passage. It is preferable that the hub has a bifurcated structure, with the fluid injection section provided on one of the bifurcated ends and the treatment section on the other.

[0018] It is preferable that the outer surface of shaft 2 is coated. In rapid exchange type balloon catheter 1, it is preferable that the outer surface of one or both of the proximal outer shaft 4A and distal outer shaft 4B is coated, and it is more preferable that the outer surfaces of both the proximal outer shaft 4A and distal outer shaft 4B are coated. In over-the-wire type balloon catheter, it is preferable that the outer surface of the outer shaft is appropriately coated.

[0019] The coating can be hydrophilic or hydrophobic, depending on the purpose. The outer surface of the shaft 2 can be coated by immersing the shaft 2 in a hydrophilic or hydrophobic coating agent, applying a hydrophilic or hydrophobic coating agent to the outer surface of the shaft 2, or covering the outer surface of the shaft 2 with a hydrophilic or hydrophobic coating agent. The coating agent may contain chemicals or additives.

[0020] Examples of hydrophilic coating agents include hydrophilic polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, and methyl vinyl ether maleic anhydride copolymer, as well as hydrophilic coating agents made from any combination of these polymers.

[0021] Examples of hydrophobic coating agents include polytetrafluoroethylene (PTFE), ethylene fluoride propylene (FEP), perfluoroalkoxyalkanes (PFA), silicone oil, hydrophobic urethane resins, carbon coatings, diamond coatings, diamond-like carbon (DLC) coatings, ceramic coatings, and substances with low surface free energy terminated with alkyl groups or perfluoroalkyl groups.

[0022] It is preferable that a tip 8 is provided at the distal end of the balloon catheter 1. The tip 8 may be provided as a separate component from the inner shaft 3 distal to the distal end of the inner shaft 3, or the distal end of the inner shaft 3 may function as the tip 8 by extending the inner shaft 3 distal to the distal end of the balloon 10.

[0023] The shaft 2 may have radiopaque markers 9 positioned in the portion where the balloon 10 is located relative to the longitudinal axis, in order to allow confirmation of the balloon 10's position under X-ray fluoroscopy. The radiopaque markers 9 can be positioned, for example, on the inner shaft 3 located inside the balloon 10, preferably at positions corresponding to both ends of the straight section of the balloon 10, or at a position corresponding to the center of the straight section of the balloon 10.

[0024] The balloon 10 is formed in a cylindrical shape with a longitudinal axis direction and a radial direction, and openings on the proximal and distal ends. The longitudinal axis direction of the balloon 10 corresponds to the direction extending from the proximal to the distal end of the balloon catheter 1, and the radial direction of the balloon 10 is the direction perpendicular to the longitudinal axis direction, meaning the direction extending radially from the center of the balloon 10. The balloon 10 also has a circumferential direction perpendicular to the longitudinal axis direction. The circumferential direction of the balloon 10 is defined as the direction along the outer circumference of the expanded balloon 10 in a cross section perpendicular to the longitudinal axis direction of the balloon 10. The tubular membrane portion of the balloon 10 is referred to as the balloon body portion 16, and the balloon 10 has a tubular balloon body portion 16.

[0025] As shown in Figure 4, it is preferable that the balloon 10 has a straight tube section 13, a proximal tapered section 12 located proximal to the straight tube section 13, and a distal tapered section 14 located distal to the straight tube section 13, with respect to the longitudinal axis. The straight tube section 13 is formed in a substantially cylindrical shape extending in the longitudinal axis and has the largest radial length (outer diameter) in the balloon 10. The proximal tapered section 12 is located proximal to the straight tube section 13 and connects to the proximal end of the straight tube section 13. The proximal tapered section 12 is formed such that its outer diameter decreases as it moves away from the straight tube section 13. The distal tapered section 14 is located distal to the straight tube section 13 and connects to the distal end of the straight tube section 13. The distal tapered section 14 is formed such that its outer diameter decreases as it moves away from the straight tube section 13. Preferably, the balloon 10 further includes a proximal sleeve portion 11 located proximal to the proximal tapered portion 12 and a distal sleeve portion 15 located distal to the distal tapered portion 14. The proximal sleeve portion 11 is located proximal to the proximal tapered portion 12 and connects to the proximal end of the proximal tapered portion 12. The proximal sleeve portion 11 is formed in a substantially cylindrical shape. The distal sleeve portion 15 is located distal to the distal tapered portion 14 and connects to the distal end of the distal tapered portion 14. The distal sleeve portion 15 is formed in a substantially cylindrical shape.

[0026] As described above, the balloon 10 is configured such that when the balloon 10 is expanded in the narrowed area, the straight section 13 makes sufficient contact with the narrowed area, making it easier to perform treatments such as dilation of the narrowed area. Furthermore, because the balloon 10 has a proximal tapered section 12 and a distal tapered section 14, when the balloon 10 is deflated, the outer diameters of the proximal and distal ends of the balloon 10 can be reduced, thereby reducing the step difference between the shaft 2 and the balloon 10, making it easier to insert the balloon 10 into a body cavity, into the forceps channel of an endoscope, or into a delivery catheter such as a guiding catheter.

[0027] In the distal portion of shaft 2, the inner shaft 3 preferably extends distally from the distal end of the outer shaft 4, and the inner shaft 3 preferably extends through the internal space of the balloon 10 from the proximal sleeve portion 11 to the distal sleeve portion 15. Furthermore, it is preferable that the outer surface of the inner shaft 3 is joined to the inner surface of the distal sleeve portion 15 of the balloon 10, and the outer surface of the outer shaft 4 is joined to the inner surface of the proximal sleeve portion 11 of the balloon 10. With the distal portion of shaft 2 configured in this way, the balloon expansion fluid can be supplied to the internal space of the balloon 10 through the space between the inner shaft 3 and the outer shaft 4.

[0028] The size of the balloon 10 is not particularly limited. For example, the size of the balloon 10 can be appropriately set within the range of 4 mm to 400 mm in the longitudinal axis direction of the straight tube section 13 and 1 mm to 30 mm in the outer diameter of the straight tube section 13.

[0029] The balloon 10 (especially the balloon body 16) is preferably made of a resin, and more preferably of a thermoplastic resin. This makes it easier to manufacture the balloon 10 by molding. Examples of resins that make up the balloon 10 include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; polyester resins such as polyethylene terephthalate and polyester elastomer; polyurethane resins such as polyurethane and polyurethane elastomer; polyamide resins such as polyphenylene sulfide resin, polyamide, and polyamide elastomer; fluororesin, silicone resin, and natural rubber such as latex rubber. These may be used alone or in combination of two or more. Among these, polyamide resins, polyester resins, and polyurethane resins are preferably used. In particular, it is preferable to use elastomer resins from the viewpoint of thinning the balloon 10 and its flexibility. For example, among polyamide resins, nylon 12 and nylon 11 are suitable materials for the balloon 10, and nylon 12 is preferably used because it can be molded relatively easily when blow molding. Furthermore, from the viewpoint of thinning the balloon 10 and improving its flexibility, polyamide elastomers such as polyether ester amide elastomers and polyamide ether elastomers are preferably used. Among these, polyether ester amide elastomers are preferably used because they have high yield strength and good dimensional stability of the balloon 10.

[0030] As shown in Figure 5, the balloon 10 has a liquid-absorbing swelling layer 31 on its outer surface, and a drug layer 32 is further provided on the outer surface of the liquid-absorbing swelling layer 31. Figure 5 shows a vertical cross-sectional view in the longitudinal direction of the balloon 10 shown in Figure 4, in which the liquid-absorbing swelling layer 31 and the drug layer 32 are provided on the outer surface of the balloon 10. Figures 6 to 11 show various examples of partially enlarged cross-sectional views of the balloon 10 shown in Figure 5.

[0031] By providing a drug layer 32 on the balloon 10, when the balloon 10 is expanded in a stenotic or lesional area, the drug can be transferred to the inner wall of the body cavity, such as the blood vessel wall. In this case, a fluid-absorbing and swelling layer 31 is provided between the drug layer 32 and the outer surface of the balloon 10. When the balloon 10 is expanded, the fluid-absorbing and swelling layer 31 comes into contact with body fluid, causing it to absorb fluid and swell, making it easier for the drug layer 32 to detach from the surface of the balloon 10. Therefore, it becomes easier to efficiently transfer the drug contained in the drug layer 32 to the inner wall of the body cavity, such as the blood vessel wall.

[0032] The fluid-absorbing swelling layer 31 is a layer that can swell by absorbing body fluids and contains a component that swells when it comes into contact with body fluids. The fluid-absorbing swelling layer 31 is provided on the outer surface of the balloon 10, and more specifically, it is preferably provided on the outer surface of the balloon body 16. At least a portion of the fluid-absorbing swelling layer 31 is provided between the balloon body 16 and the drug layer 31.

[0033] The components that swell when they come into contact with body fluids in the fluid-absorbing swelling layer 31 include hydrophilic swelling components and hydrophobic swelling components. For example, when the balloon 10 is expanded and used in a body cavity containing body fluids with a high water content, such as blood vessels, it is preferable that the fluid-absorbing swelling layer 31 contains hydrophilic swelling components. On the other hand, when the balloon 10 is expanded and used in a body cavity containing body fluids with a high lipid content, such as bile ducts, it is preferable that the fluid-absorbing swelling layer 31 contains hydrophobic swelling components. Thus, it is preferable to appropriately set the swelling components constituting the fluid-absorbing swelling layer 31 according to the usage conditions of the balloon 10.

[0034] As hydrophilic swelling components, components that are insoluble or sparingly soluble in water of the water-absorbing material are preferred. Examples include hydrophilic polymers such as polyvinylpyrrolidone, sodium poly(meth)acrylate, polyvinyl alcohol, cellulose polymers, gelatin, and hyaluronic acid. As hydrophobic swelling components, components that are insoluble or sparingly soluble in the hydrophobic components of the material that absorbs the hydrophobic components are preferred. Examples include hydrophobic polymers such as octadecyl polyacrylate, low molecular weight gelling agents such as 12-hydroxystearic acid and N-lauroyl-L-glutamic acid α,γ-bis-n-butylamide. As low molecular weight gelling agents, cyclic dipeptides combining neutral amino acids such as L-leucine and acidic amino acid derivatives such as L-glutamic acid-γ-ester can also be used. Cyclic dipeptides are preferred because they are highly safe as they do not have toxicity when they remain in the body. Methods for making hydrophilic polymers insoluble in water and hydrophobic polymers insoluble in hydrophobic components include using polymers with high molecular weight and crosslinking polymers together.

[0035] The drugs included in the drug layer 32 are not particularly limited as long as they are pharmacologically active substances, and include, for example, gene therapy drugs, non-gene therapy drugs, small molecules, cells, and other drugs that are accepted as pharmaceuticals. In particular, when the balloon catheter 1 is used to suppress restenosis of blood vessels after treatment in angioplasty, anti-restenotic agents such as antiproliferative agents and immunosuppressants can be preferably used as drugs, and specifically, drugs such as paclitaxel, sirolimus (rapamycin), everolimus, and zotarolimus can be used. These drugs may be used individually or in combination of two or more.

[0036] The drug layer 32 may contain pharmacologically active substances along with auxiliary agents to improve the dispersibility, solubility, transfer to the blood vessel wall, and storage stability of the drug. Examples of auxiliary agents include stabilizers, binders, disintegrants, moisture-proofing agents, preservatives, and solubilizers. Specifically, examples include lactose, sucrose, maltose, dextrin, xylitol, erythritol, mannitol, ethylenediamine, potassium iodide, urea, polysorbate, dibutylhydroxytoluene, polyethylene glycol, lipids, sodium pyrosulfite, ascorbic acid, tocopherol, benzoic acid, parahydroxybenzoic acid esters, polyacrylic acid, polylactic acid, polyglycolic acid, hyaluronic acid, chitosan, and gelatin.

[0037] The drug constituting the drug layer 32 is preferably crystalline, and in particular, the pharmacologically active substance is preferably crystalline. Examples of crystalline pharmacologically active substances include paclitaxel, sirolimus (rapamycin), everolimus, and zotarolimus. It is also preferable that the auxiliary agents and protective agents included with the pharmacologically active substance are crystalline. Examples of crystalline auxiliary agents and protective agents include salts such as sugar, urea, and potassium iodide, ascorbic acid, polylactic acid, and polyglycolic acid. This increases the brittleness of the drug layer 32, making it more prone to cracking or breaking when the balloon 10 is expanded, and causing the liquid-absorbing swelling layer 31 to absorb liquid and swell at an early stage of balloon 10 expansion, making it easier for the drug layer 32 to detach from the balloon 10.

[0038] The drug layer 32 may be provided on only a portion of the outer surface of the liquid-absorbing swelling layer 31 or on the entire surface. The drug layer 32 may also be provided on surfaces other than the outer surface of the liquid-absorbing swelling layer 31, and a portion of the drug layer 32 may be in contact with the outer surface of the balloon 10. Preferably, the drug layer 32 is provided on at least a portion of the outer surface of the liquid-absorbing swelling layer 31 provided on the outer surface of the straight tube portion 13 of the balloon 10.

[0039] The thickness of the drug layer 32 may be uniform or non-uniform. For example, the drug layer 32 may be thinner in some areas. This makes it easier for the fluid-absorbing swelling layer 31 to be exposed to the outside from the thinner parts of the drug layer 32 when the drug is eluted from the drug layer 32. Alternatively, when the balloon 10 is expanded, the drug layer 32 may crack or rupture in the thinner parts. As a result, the fluid-absorbing swelling layer 31 comes into contact with body fluids in those areas, and as the fluid-absorbing swelling layer 31 absorbs and swells the body fluids, the drug layer 32 can be quickly detached from the surface of the balloon 10. Cracks may be formed in the drug layer 32 even before the balloon 10 is expanded.

[0040] As shown in Figures 7 and 8, cracks 33 may be formed in the drug layer 32, and the fluid-absorbing swelling layer 31 may enter into the cracks 33. This makes it easier for the fluid-absorbing swelling layer 31 that has entered into the cracks 33 to quickly come into contact with body fluids when the balloon 10 is expanded. As a result, the fluid-absorbing swelling layer 31 that has entered into the cracks 33 swells, making it easier for the cracks 33 to widen, and the drug layer 32 to quickly detach from the surface of the balloon 10.

[0041] As shown in Figure 7, the crack 33 may be formed to extend from the inner surface of the drug layer 32, i.e., the radially inner surface, to the interior of the drug layer 32, or as shown in Figure 8, the crack 33 may be formed to extend from the inner surface of the drug layer 32, i.e., the radially inner surface, to the outer surface of the drug layer 32, i.e., the radially outer surface. In the former case, when the balloon 10 is expanded, the crack 33 extends to the outer surface of the drug layer 32, making it easier for the fluid-absorbing swelling layer 31 that has entered the crack 33 to come into contact with body fluids more quickly. In the latter case, because the crack 33 originally extends to the outer surface of the drug layer 32, when the balloon 10 is expanded, it is easier for the fluid-absorbing swelling layer 31 to come into contact with body fluids more quickly.

[0042] A portion of the outer surface of the fluid-absorbing swelling layer 31 does not need to be covered by the drug layer 32. This makes it easier for the fluid-absorbing swelling layer 31 to come into contact with body fluids when the balloon 10 is expanded, and the swelling of the fluid-absorbing swelling layer 31 makes it easier for the drug layer 32 to quickly detach from the surface of the balloon 10. Examples of configurations in which a portion of the outer surface of the fluid-absorbing swelling layer 31 is not covered by the drug layer 32 include, as shown in Figure 8, a configuration in which a crack 33 extending from the inner surface to the outer surface of the drug layer 32 is formed in the drug layer 32, and the fluid-absorbing swelling layer 31 is not covered by the drug layer 32 in the crack 33, and, as shown in Figure 9, a configuration in which the drug layer 32 is provided only on a portion of the outer surface of the fluid-absorbing swelling layer 31, thereby preventing the fluid-absorbing swelling layer 31 from being covered by the drug layer 32.

[0043] The liquid-absorbing swelling layer 31 may be provided on only a part of the outer surface of the balloon 10 (specifically, the outer surface of the balloon body portion 16) or on the entire surface. Preferably, the liquid-absorbing swelling layer 31 is provided on at least a part of the outer surface of the straight tube portion 13 of the balloon 10. The liquid-absorbing swelling layer 31 may be provided on the entire outer surface of the straight tube portion 13 of the balloon 10. The thickness of the liquid-absorbing swelling layer 31 may be formed uniformly or unevenly.

[0044] In one embodiment, as shown in Figure 10, it is preferable that a portion of the drug layer 32 is in contact with the outer surface of the balloon 10, and more specifically, that it is in contact with the outer surface of the balloon body 16. That is, it is preferable that the fluid-absorbing swelling layer 31 is provided only on a portion of the outer surface of the balloon 10, and that a portion of the drug layer 32 is in contact with the outer surface of the balloon 10. This locks the drug layer 32 to the outer surface of the balloon 10, making it less likely for the drug layer 32 to detach from the balloon 10 when the balloon 10 is delivered to a stenosis or lesion. Furthermore, by including both a portion of the drug layer 32 in contact with the outer surface of the balloon 10 and a portion in contact with the outer surface of the fluid-absorbing swelling layer 31, when the fluid-absorbing swelling layer 31 absorbs body fluid and swells, a force spreading radially outward or circumferentially from the balloon 10 acts unevenly on the drug layer 32, making it easier for the drug layer 32 to peel off from the surface of the balloon 10.

[0045] It is preferable that the liquid-absorbing swelling layer 31 contacts the outer surface of the balloon 10 (preferably the outer surface of the balloon body portion 16) over a larger area or longer length than the drug layer 32. For example, in a vertical cross-section in the longitudinal direction of the balloon 10 (preferably a vertical cross-section in the longitudinal direction of the straight tube portion 13 of the balloon 10), it is preferable that the length over which the liquid-absorbing swelling layer 31 contacts the outer surface of the balloon 10 is longer than the length over which the drug layer 32 contacts the outer surface of the balloon 10. This makes it easier for the drug layer 32 to detach from the surface of the balloon 10 more reliably due to the swelling of the liquid-absorbing swelling layer 31 when the balloon 10 is expanded. Note that the length over which the liquid-absorbing swelling layer 31 or drug layer 32 contacts the outer surface of the balloon 10 as described here means the sum of the lengths over which the liquid-absorbing swelling layer 31 or drug layer 32 contacts the outer surface of the balloon 10 at multiple locations. In a vertical cross-section along the longitudinal axis of the balloon 10, the length of the liquid-absorbing swelling layer 31 in contact with the outer surface of the balloon 10 is preferably at least twice, more preferably at least three times, and even more preferably at least four times, the length of the drug layer 32 in contact with the outer surface of the balloon 10. There is no particular upper limit to the ratio of the length of the liquid-absorbing swelling layer 31 in contact with the outer surface of the balloon 10 to the length of the drug layer 32 in contact with the outer surface of the balloon 10, and the drug layer 32 does not have to be in contact with the outer surface of the balloon 10. If a part of the drug layer 32 is in contact with the outer surface of the balloon 10, the length of the liquid-absorbing swelling layer 31 in contact with the outer surface of the balloon 10 in a vertical cross-section along the longitudinal axis of the balloon 10 may be 100 times or less, 50 times or less, 30 times or less, or 20 times or less, the length of the drug layer 32 in contact with the outer surface of the balloon 10.

[0046] In a vertical cross-section of the balloon 10 in the longitudinal direction (preferably the vertical cross-section of the straight tube portion 13 of the balloon 10 in the longitudinal direction), the maximum length of contact between the liquid-absorbing swelling layer 31 and the outer surface of the balloon 10 is preferably 100 μm or more, more preferably 300 μm or more, and even more preferably 500 μm or more. This ensures that the drug layer 32 is secured to the outer surface of the balloon 10, making it less likely for the drug layer 32 to detach from the balloon 10 when the balloon 10 is delivered to a stenosis or lesion. The maximum length of contact between the liquid-absorbing swelling layer 31 and the outer surface of the balloon 10 may be 1.0 mm or more, 1.5 mm or more, or 2.0 mm or more.

[0047] In a vertical cross-section of the balloon 10 in the longitudinal direction (preferably the vertical cross-section of the straight tube portion 13 of the balloon 10 in the longitudinal direction), it is preferable that the average thickness of the drug layer 32 is greater than the average thickness of the liquid-absorbing swelling layer 31. This suppresses excessive swelling of the liquid-absorbing swelling layer 31 when it absorbs liquid, and even if the liquid-absorbing swelling layer 31 swells unintentionally during delivery of the balloon 10, the drug layer 32 is less likely to peel off from the surface of the balloon 10. It is preferable that the drug layer 32 peels off from the surface of the balloon 10 due to the combined action of balloon expansion and swelling of the liquid-absorbing swelling layer 31. For example, the average thickness of the drug layer 32 is preferably 1.5 times or more, more preferably 2 times or more, preferably 20 times or less, more preferably 15 times or less, and even more preferably 10 times or less than the average thickness of the liquid-absorbing swelling layer 31.

[0048] In the above, the average thickness of the drug layer 32 can be determined by dividing the area of ​​the drug layer 32 in a vertical cross-section in the longitudinal direction of the balloon 10 by the circumference of the outer surface of the balloon 10 (the circumference of the outer surface of the balloon body 16). The average thickness of the liquid-absorbing swelling layer 31 can be determined by dividing the area of ​​the liquid-absorbing swelling layer 31 in a vertical cross-section in the longitudinal direction of the balloon 10 by the circumference of the outer surface of the drug layer 32 based on the average thickness of the drug layer 32. The circumference of the outer surface of the drug layer 32 based on the average thickness of the drug layer 32 means the circumference of the outer surface of the drug layer 32 when the drug layer 32 is uniformly formed on the outer surface of the balloon 10 with an average thickness.

[0049] In a vertical cross-section of the balloon 10 in the longitudinal direction (preferably the vertical cross-section of the straight tube portion 13 of the balloon 10 in the longitudinal direction), it is also preferable that the maximum thickness of the drug layer 32 is greater than the maximum thickness of the liquid-absorbing swelling layer 31. For example, the maximum thickness of the drug layer 32 is preferably 1.5 times or more, more preferably 2 times or more, preferably 20 times or less, more preferably 15 times or less, and even more preferably 10 times or less than the maximum thickness of the liquid-absorbing swelling layer 31.

[0050] The lengths of the drug layer 32 and the liquid-absorbing swelling layer 31 in contact with the outer surface of the balloon 10, the average thickness of the drug layer 32 and the liquid-absorbing swelling layer 31, and the maximum thickness of the drug layer 32 and the liquid-absorbing swelling layer 31 described above may be determined in a cross-section along the longitudinal axis of the balloon 10 (preferably a cross-section along the longitudinal axis of the straight tube portion 13 of the balloon 10). In this case, the preferred range described above also applies.

[0051] When the balloon 10 is inflated, the drug layer 32 detaches from the balloon 10, but the fluid-absorbing swelling layer 31 may detach from the balloon 10 or remain on the outer surface of the balloon 10. For example, when the balloon 10 is inflated, at least a portion of the fluid-absorbing swelling layer 31 may detach from the balloon 10 together with the drug contained in the drug layer 32. In this case, the swelling component contained in the fluid-absorbing swelling layer 31 comes into contact with blood, inducing blood coagulation (thrombus formation), and the drug attached to the blood vessel wall becomes more easily covered by a thrombus. Therefore, the risk of the drug detaching from the blood vessel wall due to direct exposure of the drug to blood flow can be reduced, and the drug can be more easily fixed stably to the blood vessel wall. Gelatin is an example of a swelling component that induces blood coagulation. On the other hand, when the balloon 10 is inflated, at least a portion of the fluid-absorbing swelling layer 31 may remain on the outer surface of the balloon 10. By allowing the fluid-absorbing swelling layer 31 to remain on the outer surface of the balloon 10, it is possible to prevent foreign substances from remaining in the body, such as swelling components contained in the fluid-absorbing swelling layer 31 falling into the bloodstream and obstructing blood flow.

[0052] As shown in Figure 11, it is preferable that a protective layer 34 be provided on the outer surface of the drug layer 32. By providing a protective layer 34 on the outer surface of the drug layer 32, it is possible to suppress the leaching of the drug from the drug layer 32 and the detachment of the drug layer 32 from the balloon 10 during delivery of the balloon 10.

[0053] The protective layer 34 can be composed of, for example, a hydrophobic component. For example, when delivering the balloon 10 into a body cavity containing body fluids with a high water content, such as blood vessels, if a protective layer 34 composed of a hydrophobic component is provided on the outer surface of the drug layer 32, the dissolution of the protective layer 34 when it comes into contact with body fluids will be suppressed, and the protective layer 34 will be able to perform its protective function for the drug layer 32. Examples of hydrophobic components include lipid compounds such as lecithin, propylene glycol stearate, cholesterol, and terpenes; hydrocarbon compounds such as petrolatum; hydrophobic (meth)acrylic polymers such as ethyl polyacrylate and polymethyl methacrylate; hydrophobic polyester polymers such as polylactic acid and polyglycolic acid; and silicone oil.

[0054] The protective layer 34 may be composed of hydrophilic components. For example, when delivering the balloon 10 into a body cavity containing body fluids rich in lipid-soluble components, such as a bile duct containing bile, if a protective layer 34 composed of hydrophilic components is provided on the outer surface of the drug layer 32, the dissolution of the protective layer 34 upon contact with body fluids will be suppressed, and the protective layer 34 will be able to exert its protective function for the drug layer 32. Examples of hydrophilic components include hydrophilic polymers such as carboxymethylcellulose, hydroxypropylcellulose, methylcellulose, hydroxyethylcellulose, polyvinyl alcohol, alginic acid, pectin, gum arabic, gellan gum, guar gum, xanthan gum, carrageenan, gelatin, polyethylene glycol, hyaluronic acid, and sodium polyacrylate, salts such as potassium chloride and ammonium acetate, amino acids such as glycine and glutamic acid, sugars such as glucose and fructose, and urea.

[0055] Furthermore, even when delivering the balloon 10 to a body cavity containing body fluids with a high water content, such as blood vessels, it is also preferable that the protective layer 34 be composed of the aforementioned hydrophilic components, particularly a hydrophilic polymer with a high molecular weight. When a hydrophilic polymer with a high molecular weight is used as the protective layer 34, it is possible to prevent the dissolution of the protective layer 34 by the water in the body fluids and to maintain the protective function of the drug layer 32.

[0056] The protective layer 34 is preferably provided so as to cover at least a portion of the outer surface of the drug layer 32. The protective layer 34 may cover the entire outer surface of the drug layer 32, or it may cover only a portion of the outer surface of the drug layer 32. In the former case, when the balloon 10 is delivered, the entire drug layer 32 is protected by the protective layer 34, and the leaching of the drug from the drug layer 32 is effectively suppressed. In the latter case, when the balloon 10 is delivered, there is a risk that some of the drug may leach from the portion of the drug layer 32 that is not covered by the protective layer 34, but when the balloon 10 is expanded, the portion of the drug layer 32 that is not covered by the protective layer 34 is more likely to peel off from the surface of the balloon 10.

[0057] If a portion of the outer surface of the fluid-absorbing swelling layer 31 is not covered by the drug layer 32, it is preferable that a protective layer 34 be provided on the outer surface of the portion of the fluid-absorbing swelling layer 31 that is not covered by the drug layer 32. For example, as shown in Figure 8, if a crack 33 is formed on the outer surface of the drug layer 32, and the crack 33 extends from the inner surface of the drug layer 32 to the outer surface of the drug layer 32, it is preferable that the protective layer 34 be provided so as to cover the crack 33. The protective layer 34 may also penetrate into the interior of the crack 33. By covering the fluid-absorbing swelling layer 31 with the protective layer 34, when the balloon 10 is delivered, the body fluid comes into contact with the fluid-absorbing swelling layer 31, causing the fluid-absorbing swelling layer 31 to swell, and preventing the drug layer 33 from peeling off from the surface of the balloon 10. In this case, it is preferable that the entire outer surface of the portion of the fluid-absorbing swelling layer 31 that is not covered by the drug layer 32 is covered with the protective layer 34. The same applies when the drug layer 32 is provided only on a portion of the outer surface of the fluid-absorbing swelling layer 31, as shown in Figure 9.

[0058] Preferred combinations of the fluid-absorbing swelling layer 31 and the protective layer 34 include a combination in which the fluid-absorbing swelling layer 31 contains a hydrophilic swelling component and the protective layer 34 contains a hydrophobic component, and a combination in which the fluid-absorbing swelling layer 31 contains a hydrophobic swelling component and the protective layer 34 contains a hydrophilic component. In the former case, the balloon catheter 1 can be suitably used to deliver a drug to the inner wall of a body cavity where body fluids with a high water content, such as blood vessels, are present. In the latter case, the balloon catheter 1 can be suitably used to deliver a drug to the inner wall of a body cavity where body fluids containing a large amount of lipid-soluble components, such as bile ducts, are present. In either case, the protective layer 34 suitably protects the drug layer 32 and the fluid-absorbing swelling layer 31 when the balloon 10 is expanded, and the fluid-absorbing swelling layer 31 can suitably absorb body fluids and swell, allowing the drug contained in the drug layer 32 to be efficiently transferred from the surface of the balloon 10 to the inner wall of the body cavity.

[0059] The components of the liquid-absorbing swelling layer 31, the drug layer 32 (including the cracks 33), and the protective layer 34 described above can be combined in any way.

[0060] A preferred embodiment of the drug contained in the drug layer 32 will now be described. It is preferable that the drug layer 32 contains the drug in the form of elongated crystals. When the drug layer 32 contains the drug in such a crystalline form, when the balloon 10 is expanded, the elongated crystalline drug comes into contact with the inner wall of the body cavity in a way that it penetrates it, making it easier to efficiently transfer the drug to the inner wall of the body cavity. Examples of elongated crystals include columnar crystals and needle-shaped crystals, and these crystals may be solid or hollow.

[0061] Examples of columnar crystals include cylindrical crystals and polygonal prisms such as triangular, square, pentagonal, and hexagonal prisms. The cross-sectional shape perpendicular to the longitudinal axis of a columnar crystal does not necessarily have to be a perfectly polygonal shape; the corners of the polygon may be flattened or the edges may be distorted. Furthermore, the edges along the longitudinal axis of a polygonal prism do not necessarily have to be straight lines.

[0062] The length of the elongated crystal in the longitudinal axis direction may be, for example, 3 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more, or 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. The outer diameter of the cross section perpendicular to the longitudinal axis direction of the elongated crystal may be, for example, 0.01 μm or more, 0.1 μm or more, or 0.5 μm or more, or 5 μm or less, 3 μm or less, or 1 μm or less. The outer diameter described here corresponds to the diameter of the circle circumscribing the shape of the cross section perpendicular to the longitudinal axis direction of the elongated crystal. Preferably, the length of the elongated crystal in the longitudinal axis direction is longer than the outer diameter of the cross section perpendicular to the longitudinal axis direction of the elongated crystal. For example, the length of the elongated crystal in the longitudinal axis direction may be 2 or more, 3 or more, 5 or more, or 10 or more times the outer diameter of the cross section perpendicular to the longitudinal axis direction of the elongated crystal, or it may be 200 or less, 150 or less, 100 or less, or 50 or less.

[0063] In the drug layer 32, it is preferable that multiple elongated crystals are arranged radially to form a radial crystal group. In the radial crystal group, it is preferable that the elongated crystals are arranged radially in three dimensions, and that the elongated crystals are arranged so as to extend from the radial center in the radial direction of the balloon 10 and in the circumferential direction of the balloon 10 (i.e., in the longitudinal axis direction and circumferential direction of the balloon 10). It is preferable that the drug layer 32 is formed by a large number of such radial crystal groups. When the drug layer 32 contains the drug in the form of a radial crystal group, when the balloon 10 is expanded, one of the elongated crystals included in the radial crystal group comes into contact with the inner wall of the body cavity so as to penetrate it, making it easier for the drug to be transferred to the inner wall of the body cavity in the form of a radial crystal group. Therefore, the drug can be transferred to the inner wall of the body cavity more efficiently.

[0064] In a plan view from the radial outside of the balloon 10, the major axis of the radial crystal group is preferably 10 μm or more and 80 μm or less. More preferably 15 μm or more, even more preferably 20 μm or more, preferably 70 μm or less, and even more preferably 60 μm or less. The inner walls of body cavities, such as blood vessel walls, have minute irregularities, and the size of these irregularities is often about the same as described above. Therefore, having the major axis of the radial crystal group within this range allows the radial crystal group to easily fit into the irregularities of the inner wall of the body cavity, and the radial crystal group that has migrated to the inner wall of the body cavity is less likely to detach from the inner wall of the body cavity. As a result, the drug can be effectively delivered to the inner wall of the body cavity.

[0065] The drug contained in the drug layer 32 is preferably paclitaxel. By using paclitaxel as the drug, it becomes easy to incorporate the drug into the drug layer 32 in the form of elongated crystals or radial crystal clusters as described above. For example, a crystal nucleating material is placed on the outer surface of the liquid-absorbing swelling layer 31, and then a paclitaxel solution is applied to the outer surface of the liquid-absorbing swelling layer 31. This allows paclitaxel crystals to form and grow around the nucleating material, thereby forming elongated crystals or radial crystal clusters of paclitaxel.

[0066] Although not shown in the drawings, in order to give the balloon catheter 1 a scoring function, the balloon 10 may have a convex protrusion projecting radially outward or a wire positioned on the outer side of the balloon 10. In this case, it is preferable that the balloon 10 has a balloon body portion 16, and that the outer surface of the balloon body portion 16 has a convex protrusion projecting radially outward, or that a wire is positioned on the radially outward side of the balloon body portion 16. In a vertical cross-section in the longitudinal axis direction of the balloon 10, it is preferable that the outer shape of the balloon body portion 16 is substantially circular. In the straight tube portion 13, it is preferable that the outer surface of the balloon body portion 16 is cylindrical. It is preferable that the liquid-absorbing swelling layer 31 is provided on the outer surface of the balloon body portion 16, and that the drug layer 32 is provided on the outer surface of the liquid-absorbing swelling layer 31. The liquid-absorbing swelling layer 31 may be provided on the surface of the convex protrusion or wire, and the drug layer 32 may be provided on the outer surface of the liquid-absorbing swelling layer 31 provided on the surface of the convex protrusion or wire.

[0067] When the balloon 10 is delivered to the treatment area, such as a narrowed blood vessel, it is preferable that it be inserted into the guiding catheter or sheath in a deflated state. In this case, it is preferable that the balloon 10 is appropriately folded so that its radial size is reduced.

[0068] Figures 12 and 13 show an example of the balloon 10 shown in Figure 5 when it is deflated and folded. As shown in Figures 12 and 13, in the deflated state of the balloon 10, the balloon 10 has a folded wing portion 21 formed by folding the inner surface of the balloon body portion 16 inward, and it is preferable that the folded wing portion 21 is arranged to overlap the outer surface of the balloon 10. The folded wing portion 21 is formed by folding the balloon body portion 16 along the fold line 22, and the balloon body portions 16 overlap each other. At the fold line 22, the balloon body portion 16 is folded with its inner surface inward. Therefore, when viewed from the outside of the balloon 10, the fold line 22 is formed as a mountain fold. It can also be said that the folded wing portion 21 is formed by the balloon 10 being folded with its inner surface inward.

[0069] At the fold line 22, the balloon body portion 16 may be folded back so that a clear crease is formed, or its tip may be folded back in a rounded shape. Since the balloon body portion 16 usually has a certain thickness and elasticity, the tip of the balloon body portion 16 is folded back in a rounded shape at the fold line 22. In this case, the folded tip of the balloon body portion 16 becomes the fold line 22.

[0070] It is preferable that the fold line 22 is formed at least on the straight tube portion 13. Therefore, it is preferable that the balloon 10 has a folded wing portion 21 formed in the straight tube portion 13 by folding back the balloon body portion 16, and that the folded wing portion 21 is arranged to overlap the outer surface of the straight tube portion 13.

[0071] The folding line 22 is preferably formed to extend parallel to the longitudinal axis or diagonally with respect to the longitudinal axis. Furthermore, it is preferable that multiple folding fin portions 21 are provided on the outer surface of the balloon 10. By forming the folding fin portions 21 in this way, it becomes easier to fold the balloon 10 compactly.

[0072] The balloon body portion 16 may have fold lines formed on one and / or the other side in the circumferential direction of the fold line 22, with the outer surface of the balloon body portion 16 folded inward (valley fold lines when viewed from the outside of the balloon 10). In this case, it is preferable that the fold lines that become valley fold lines form the base of the folded wing portion 21.

[0073] The multiple folding fin portions 21 may be arranged on the outer surface of the balloon 10 such that all of them collapse to one side in the circumferential direction, or some of the folding fin portions 21 may be arranged on the outer surface of the balloon 10 such that they collapse to one side in the circumferential direction and other folding fin portions 21 may be arranged on the outer surface of the balloon 10 such that they collapse to the other side in the circumferential direction. In Figure 12, the folding fin portions 21 are arranged on the outer surface of the balloon 10 in the former configuration, and in Figure 13, the folding fin portions 21 are arranged on the outer surface of the balloon 10 in the latter configuration.

[0074] In the folded balloon 10, it is also preferable that a crack 33 is formed at either the inner surface of the collapsed folded wing portion 21 or at the drug layer 32 located on the outer surface of the balloon 10 opposite to the inner surface. If a crack 33 is formed in this way, when the balloon 10 is delivered, it is suppressed that body fluid enters through the crack 33 in the drug layer 32 located on the inner surface of the collapsed folded wing portion 21 or at the outer surface of the balloon 10 opposite to the inner surface and comes into contact with the fluid-absorbing swelling layer 31, making it difficult for the drug layer 32 to peel off from the surface of the balloon 10. On the other hand, when the balloon 10 is expanded, body fluid enters through the crack 33 in the drug layer 32 and comes into contact with the fluid-absorbing swelling layer 31, and from there the drug layer 32 can easily peel off from the surface of the balloon 10. In this case, it is preferable that no crack 33 is formed in the drug layer 32 located on the radial outer surface of the collapsed folded wing portion 21. This makes it less likely for the drug layer 32 provided on the surface of the balloon 10 to detach from the surface of the balloon 10 during delivery. [Explanation of Symbols]

[0075] 1: Balloon catheter 2: Shaft 3: Inner shaft 4: Outer shaft, 4A: Proximal outer shaft, 4B: Distal outer shaft 5: Hub 6:Fluid injection part 7: Guide wire port 8: Tip 9: X-ray opaque markers 10: Balloon 11: Proximal sleeve section 12: Proximal tapered section 13: Straight pipe section 14: Distal tapered section 15: Distal sleeve portion 16: Balloon body 21: Folding wing section 22: Folding line 31: Liquid-absorbing swelling layer 32: Drug layer 33: Crack 34:Protective layer

Claims

1. A balloon catheter equipped with a balloon, A balloon catheter having a liquid-absorbing swelling layer on the outer surface of the balloon, and a drug layer on the outer surface of the liquid-absorbing swelling layer.

2. The balloon catheter according to claim 1, wherein a portion of the drug layer is in contact with the outer surface of the balloon.

3. The balloon catheter according to claim 1, wherein a crack is formed in the drug layer and the fluid-absorbing swelling layer enters the crack.

4. The balloon catheter according to claim 1, wherein a portion of the outer surface of the fluid-absorbing swelling layer is not covered by the drug layer.

5. The balloon catheter according to claim 1, wherein a protective layer is provided on the outer surface of the drug layer.

6. The balloon catheter according to claim 1, wherein when the balloon is expanded, at least a portion of the fluid-absorbing swelling layer detaches from the balloon integrally with the drug contained in the drug layer.

7. The balloon catheter according to claim 1, wherein at least a portion of the fluid-absorbing swelling layer remains on the outer surface of the balloon when the balloon is expanded.

8. The balloon catheter according to claim 1, wherein the drug layer comprises a drug in the form of elongated crystals.

9. The balloon catheter according to claim 8, wherein in the drug layer, a plurality of the elongated crystals are arranged radially to form a radial crystal group.

10. The balloon catheter according to claim 9, wherein, in a plan view from the radially outer side of the balloon, the major axis of the radial crystal group is 10 μm or more and 80 μm or less.

11. The balloon catheter according to claim 1, wherein the drug contained in the drug layer is paclitaxel.

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