Patent Description:
A medication pen for delivering self-administered medications generally comprises a pen body, which houses a medication compartment, and a separate pen needle which may be attached to and detached from the pen body. The pen needle includes a needle-bearing hub having a recess on the proximal side for receiving the pen body and a proximal (non-patient end) needle accessing the medication compartment, typically piercing the septum of a medication cartridge in the pen body. The distal (patient-end) of the pen needle assembly includes the beveled distal end of the needle that is inserted into the injection site.

Injections may be performed in the intradermal (ID) region, the subcutaneous (SC) region and the intramuscular (IM) region. For many types of injectable medications, including insulin, the SC region is preferred for administering an injection. See, for example, <NPL>).

Different length needles, and with increasing frequency, shorter needles such as <NUM> and <NUM> needles, are adapted to achieve injection to a specified target depth in a subcutaneous region. The present invention addresses the need to ensure that a needle is inserted to its target depth, regardless of the angle at which the user may approach the injection site with the medication pen.

In certain prior art pen needles the cannula is supported in an axially positioned post on the hub. The post forms a narrow portion extending distally from the relatively wider portion in which the pen body is received. In other pen needles known in the art, a distal face of the hub placed against the injection site may be relatively large, and may be provided with a slight taper at the edge. However, the edge of the hub engages the skin when the cannula is inserted at an angle, interfering with the injection. The slight taper is not functional during an injection, or is only at the edge of the distal face of the hub, generally having a radius of curvature greater than about <NUM>.

While the prior devices are generally suitable for the intended use, there is a continuing need for improved devices for controlling the penetration of a cannula for delivering a drug or medicament. <CIT> discloses a pen needle assembly for delivering drug solutions.

<CIT> discloses a pen needle hub having an increased contact area.

The present invention is directed to an injection device and particularly to a needle hub for coupling to an injection pen where the needle hub has skin contact surface configured for controlling the depth of penetration by a cannula extending from the needle hub. The invention is particularly directed to a needle hub device where the contact surface has a height and width that complement each other to control the depth of penetration of the cannula.

These and other objects of the invention are achieved in one aspect of the invention with a pen needle comprising, a needle-bearing hub having a recess on a proximal side for receiving a medication pen body; a cannula having a beveled distal end for injection into a subject's skin, and a proximal end for positioning in a medication compartment of the pen body, wherein the hub has a distal face having a diameter in a range of <NUM> to <NUM>; and at least a portion of the distal face has a radius of curvature in a range of <NUM> to <NUM>. In embodiments a central portion of the hub surrounding the cannula has a diameter in a range of <NUM> to <NUM>.

In another aspect, the invention is a medication pen comprising a pen body having a medication compartment with a removable pen needle having a needle hub. The needle hub has in various embodiments of the invention can have a convex distal axial surface for contacting the skin during needle insertion and drug delivery. The needle hub can have a contact surface area of about <NUM>-<NUM><NUM>. The contact surface in one embodiment can have a height of about of <NUM> to <NUM> and an inner ring with a surface area of <NUM>-<NUM><NUM>.

One feature of the invention is to provide an injection device with a skin contact surface having a convex surface with a height of about <NUM> to <NUM> and cannula for penetrating the skin projecting from the contact surface. The cannula can be located in the center of the contact surface so that the contact surface surrounds the cannula. In one embodiment the invention, the convex contact surface has a height of about <NUM> to <NUM> and width of about <NUM> to <NUM> to provide sufficient surface area and a suitable shape and angle with respect to the axis of the cannula to contact the skin and provide the controlled depth of penetration by the cannula into the skin.

Another feature of the invention is to provide an injection device having a cannula for penetrating the skin and where the device has a skin contact surface having a substantially convex surface with a width and height to control the depth of penetration. The convex surface has a height and a width to control the deformation of the skin during the insertion of the cannula to inhibit the cannula from penetrating the skin to a depth deeper than intended while ensuring the penetration to the desired depth.

In another aspect, a non-claimed method is provided to reduce an incidence of shallow injections in a program of injections, comprising administering a series of injections using the medication pen and pen needle described above.

A convex curved hub design, as described herein, provides a greater surface area contacting an injection site on a patient while minimizing injection performance issues compared to the prior devices. Specifically, greater patient comfort and stability are achieved as a result of a larger surface area contacting the skin during injection, but if an injection is performed at an angle, the edge of the hub according to present design will enable and promote full insertion of the pen needle cannula. These considerations are particularly important with pen needles having shorter cannula in a range of <NUM> or <NUM>. With shorter needles, if the needle does not penetrate the skin properly, the injection may be performed in the ID layer of the skin. Insulin and other diabetes related drugs are often preferably delivered to the SC space. If full insertion of the needle does not occur, insulin may not be delivered to the proper location. Another concern is that if the injection is too shallow, a depot of liquid may be created just below the skin surface. This depot can result in the appearance of a bulge in the skin, which may be painful or distracting to the patient or even result in leakage from the injection site. The problem of depot formation is exacerbated by a shallow injection and/or a larger volume of drug to be delivered which occur more frequently with the smaller needle lengths and larger volumes that are now used more frequently. Thus, a further object of the invention is to provide a pen needle hub that will position the cannula to deliver medication to the desired injection depth regardless of the angle of injection.

It will be understood that each of the preferred or optional features of the various embodiments may be combined with other features and features described in combination with one or more particular features may also be combined with one or more other features of the other embodiments.

These and other features of the invention will become apparent from the following detailed description of the invention, which in conjunction with the drawings disclose various embodiments of the invention.

The following is a brief description of the drawing in which:.

A "medication pen" is used herein to refer to a device having a medication compartment, typically containing multiple doses of medication, and a separate pen needle. The phrase "pen needle" refers to a needle-bearing assembly which can be attached to the medication pen body so that a proximal end of the pen needle assembly accesses a medication compartment and a distal end is adapted for insertion into an injection site to perform one or more injections. The terms "needle" and "cannula" are used herein interchangeably to refer to a thin tubular member having a beveled end for insertion into an injection site on a subject. As used herein, the "distal" direction is in the direction toward the injection site, and the "proximal" direction is the opposite direction. "Axial" means along or parallel to the longitudinal axis of the needle and the "radial" direction is a direction perpendicular to the axial direction.

The position of the subcutaneous layer in a subject's tissue and the desired injection depth vary depending on the age of the patient, the part of the body where the injection is administered, etc. Therefore, an injection depth in absolute terms cannot be considered a critical aspect of the invention. However, as general guidance, the intradermal (ID) layer in adults has a thickness of around <NUM> to <NUM>, so that ID injection depth is in a range of about <NUM> to <NUM>, depth being measured from the outer surface of the skin. The subcutaneous (SC) region thickness can vary widely depending on the location of the injection site on the subject's body and the subject's body mass index (BMI). The average thickness of the SC space is in the range of about <NUM> to about <NUM>, so that SC injection depth is in a range of about <NUM> to <NUM>. The SC region may be further subdivided into the shallow subcutaneous (SSC) layer, having a thickness of about <NUM>, and an injection depth of about <NUM> to about <NUM>, the SC layer having a thickness of about <NUM>, at a depth of about <NUM> to <NUM>, and the deep subcutaneous (DSC) layer, having a thickness of about <NUM>, and a depth of about <NUM> to about <NUM>. If injections from a device occur in the upper region of the subcutaneous space (SSC), it is more likely that an ID injection will occur with that device. If injections from a device occur in the deeper regions of the subcutaneous space (DSC), it is more likely that an IM injection will occur with that device. Insulin is preferably delivered to the SC space. Injections to either the ID or intramuscular (IM) space may result in different uptake of insulin from what is prescribed.

The position of different regions and layers in the tissue of different subjects may be ascertained using ultrasound imaging. These techniques also may be used to determine the location of a medication depot after injection for an empirical determination whether a particular injection was "shallow," (i.e., the depot is found at less than a predetermined optimal depth). These observations in turn may be used to verify that the number of shallow injections is reduced. If an injection is intended to be deposited in the SC region, a "shallow injection" is defined as an injection in which the depot is in the SSC or ID region.

The invention is directed to an injection device having a cannula with a predetermined length for penetrating the skin to a predetermined penetrating depth. The injection device has a skin contact surface for contacting and deforming the skin when the cannula penetrates the skin to assist in controlling the depth of penetration at various angles of injection with respect to the surface of the skin. The contact surface has a predetermined shape, width and height to control the depth of penetration into the skin to the desired layer of the skin. It has been found that the penetration force with a device having a small narrow skin contact surface of about <NUM> or less forms a deep indentation in the skin around the cannula when the device is pressed against the skin during use. The indentation formed in the outer surface of the skin often results in the cannula penetrating deeper into the skin to skin layers deeper than intended by the user. By way of example, a <NUM> cannula mounted in a post having a width of about <NUM> can result in the contact surface forming a concave depression in the surface of the skin so that the cannula can penetrate the deeper than <NUM> and penetrate the deeper layers of the skin that can cause pain or discomfort to the user. The deeper penetration can also cause the cannula to deliver the drug to layers of the skin that are less effective in delivering the drug to the patients.

The skin contact surface of the pen needle device surrounding the cannula has a width and height configured for providing greater control of the depth of penetration by the cannula. In one embodiment of the invention, the pen needle device is configured to obtain a cannula penetration of about <NUM>. The skin contact surface is further configured to control the shape, width and depth of deformation of the skin surface when the device is pressed against the skin during the penetration of the cannula. The width is determined as being the surface area that contacts the skin during the insertion of the cannula and during the injection or delivery of the drug using a normal insertion force. The height refers to the linear distance between the outer peripheral edge of the contact surface and the proximal end of the contact surface.

The skin contact surface of the device in one embodiment has a surface area for contacting the skin of about <NUM><NUM> to about <NUM><NUM> surrounding the cannula. In various embodiments, the skin contact has a surface area of about <NUM><NUM> to <NUM><NUM>. In one embodiment, the contact surface can have a surface area of about <NUM>-<NUM><NUM>. The skin contact surface in the embodiments shown has a substantially circular or substantially circular shape with the cannula located along the center axis of the circular skin contact surface. The cannula in this embodiment has a length of about <NUM> to about <NUM> to penetrate the skin to a depth and skin layer for delivering the drug, and particularly insulin, to the most efficient depth of the skin.

The skin contact surface has a convex shape forming a continuous and uniform curvature extending from the outer edge of the hub to the distal end or outermost portion of the contact surface of the hub and the cannula so that the skin contact surface has a substantially semispherical or dome shape that contacts the skin during penetration of the cannula and delivery of the drug. The convex surface of the skin contact area can have a width or diameter of greater than <NUM> and typically about <NUM> to <NUM> and a height of about <NUM> to about <NUM> measured from the outer peripheral edge of the contact surface to the outermost center portion of the contact surface surrounding the cannula and spaced axially from the peripheral edge. In one embodiment the convex skin contact surface has a height of about <NUM> and a diameter of about <NUM>. The convex surface can have a radius of curvature of <NUM> to <NUM>. In various embodiments of the invention, the convex surface has radius of curvature of <NUM> to <NUM>. In other embodiments, the convex surface can have a radius of curvature of <NUM> to <NUM>. In one embodiment, the convex contact surface has a radius of curvature equal to or greater than the diameter of the contact surface. The radius curvature can be about <NUM> to <NUM><NUM>/<NUM> times the diameter of the contact surface.

The ratio of the diameter (D) to the height (H) of the contact surface influences the depth of penetration of the cannula on insertion into the skin. Generally, the larger the ratio provides more surface area that will contact the skin and greater control of the depth of penetration. A smaller ratio D:H provides a smaller surface area that can compress the skin on insertion and result in a deeper penetration of the cannula. In certain embodiments, the ratio of the diameter to the height of the surface area can range from about <NUM>:<NUM> to <NUM>:<NUM>. In other embodiments the ratio can range form about <NUM>:<NUM> to <NUM>:<NUM>.

In one embodiment of the invention, the skin contact surface of the injection device has a hemispherical shape with an annular recess in the contact surface surrounding the cannula. The recess in one embodiment has a depth that enables the skin to contact the bottom of the recess when the device is pressed against the skin during the insertion of the cannula into the skin. The depth and width or diameter of the recess can be configured to form part of the contact surface to control the deformation of the skin surface during penetration of the cannula to control the depth of penetration. The recess can have a depth of about <NUM> to <NUM> and typically about <NUM>. The recess can be defined by an outer ring at the outer peripheral edge of the hub and the cannula or by an outer ring at the peripheral edge and a post or inner ring around the cannula at the center of the contact surface. In other embodiments, the recess formed in the skin contact surface can have a volume of about <NUM> to <NUM>µl.

<FIG> shows a comparison of the exemplary needle hub devices where 1A and 1B have a substantially flat distal surface. As shown in the exemplary embodiment of 1C in <FIG>, pen needle hub <NUM> has a needle bearing hub with a proximal portion <NUM> enclosing a recess on a proximal side of the hub for receiving a medication pen body. Cannula <NUM>, having a beveled distal end for injection into a subject's skin, extends from a distal face <NUM> on a distal portion of the hub <NUM>. Within the distal portion, cannula <NUM> may be supported axially in a post (not shown), using adhesive or other means known in the art for immobilizing the needle. The proximal end of the needle is positioned in the hub for accessing the medication compartment of the pen body. The medication compartment is typically a container having a septum that can be pierced by the proximal end of the needle when the pen needle is installed on the pen.

The distal face of the hub <NUM> generally has a diameter between <NUM> and <NUM>. Preferably the diameter is greater than <NUM>, more preferably greater than <NUM>, and still more preferably, <NUM> or greater. It has been found that a relatively large surface area contacting the skin affords a more stable and comfortable injection with less compression of the skin, as compared to the prior device shown in 1D of <FIG>, in which the patient-end cannula extends directly from a supporting narrow post on the hub. In the device shown in 1D, when a patient performs an injection, the supporting post can press into the skin causing pain and discomfort, and may lead to a deeper than desired injection. Increasing the surface area of the hub that contacts the skin during an injection should lead to the subject experiencing less pain and discomfort and a more consistent injection depth. Thus, the lower limit of the diameter of the distal face is larger than the diameter of a supporting post (typically <NUM>). The upper end of the range for the diameter "d" of the distal face is selected so that the edge of the distal face does not interfere with injection performance. A diameter "d" greater than <NUM> may not provide an added benefit.

In addition to increased surface area, at least a portion of the distal face of the hub according to the invention is curved outwardly to form a convex surface. The curved portion has a radius of curvature in a range of <NUM> to <NUM>, and preferably <NUM> to <NUM>. In one embodiment, the curved portion has a radius of curvature of about <NUM>.

The entire distal face need not be curved. For example, an area adjacent the cannula having a diameter of <NUM> to <NUM> may be flat, i.e., perpendicular to the axis of the needle, and an area adjacent the flat area and including the peripheral edge of the distal face may have a convex curvature. The curvature at the edge of the distal face allows a needle approaching an injection site at an angle to be reoriented with respect to the injection site to penetrate more deeply, whereas the edge of a distal hub having insufficient curvature on an edge (such as shown in 1A and 1B) may prevent the needle from penetrating into the injection site when the edge of the distal face of the hub engages the skin proximate the injection site. This can cause a lateral force against the cannula that can cause the cannula to bend by the insertion force.

<FIG> depicts the results of in vivo tests performed to determine whether the incidence of shallow (ID and SSC) injections was reduced using a hub having an enlarged distal face with curvature. <FIG> shows the number of shallow (ID and SSC) injections obtained with each of the hubs, demonstrating that providing a relatively large curvature to the hub face results in fewer shallow injections. Twenty injections were performed at an angle of <NUM> degrees with respect to a line perpendicular to the injection site. An ideal injection is performed at <NUM> degrees, i.e., perpendicular to the injection site. Ultrasound imaging was used to identify the depth of the medication deposition. The prior device where the cannula extends from a post (1D) did not result in shallow injections and resulted in the cannula penetrating deeper than desired. All twenty of the injections were in the SC region. Of the hubs having an enlarged distal face, 1A through 1C, the curved face resulted in fewer shallow injections.

<FIG> shows the hub designs used to perform injections in the in vivo test. Designs 1A and 1B included a distal face having an enlarged surface area (<NUM> and <NUM> diameter, respectively) but no curvature. An embodiment according to the invention, FIG. 1C is provided with a <NUM> curvature on the distal face except for a small area around the needle. A commercial embodiment according to the prior art was also included: in which the needle is provided on a post.

Referring to <FIG> the injection device includes drug delivery pen <NUM> having an outer sleeve <NUM>, a medicament cartridge <NUM> sealed by a septum <NUM> and a cap <NUM>. A hub <NUM> having a cannula <NUM> is coupled to the delivery pen. A plunger is provided on the end of the cartridge to dispense the drug. The delivery pen has a structure and operation similar to those known in the art.

In the embodiment of <FIG> and <FIG>, the hub <NUM> for coupling to the delivery pen has a cylindrical shape and includes body <NUM> having a side wall <NUM> to form an open end <NUM>. The open end <NUM> forms an internal cavity with internal threads as shown in the embodiment of <FIG> for coupling to the pen needle delivery device <NUM> of <FIG>. In another embodiment, the hub may be provided with flattened sides <NUM>, as shown in <FIG>. The flattened sides do not impact the functionality of the curved hub face. The diameter of the hub in this instance refers the widest part of the distal-facing surface of the hub from which the cannula extends.

The hub <NUM> of <FIG> illustrate the skin contact surface and the skin deformation by the insertion force during the insertion and penetration of the cannula by an insertion force normally applied by the patient. In the embodiment shown, the hub <NUM> has an inner ring <NUM> extending from the hub. The hub has a circular outer peripheral edge <NUM> defining a width or diameter of the skin contact surface <NUM>. The inner ring <NUM> supporting the cannula <NUM> projects from the axial face <NUM> of the hub <NUM> and the peripheral edge. In this embodiment, the axial face <NUM> is substantially flat. The inner ring <NUM> has a substantially frustoconical shape or a semispherical shape with side surfaces <NUM> that slope from the axial distal end of the inner ring <NUM> to the axial face <NUM>. In the embodiment shown, the axial face has diameter of about <NUM>-<NUM> and typically about <NUM> to about <NUM>. The inner ring <NUM> has a height extending from the axial face of about <NUM> to about <NUM> and a width of about <NUM>-<NUM>.

The inner ring <NUM> typically has a central bore that extends through the hub for receiving and mounting the cannula. The open end of the bore has a width slightly greater than the width of the bore for receiving an adhesive to fix the cannula to the hub. The open end forms an adhesive well with a diameter of about <NUM> to <NUM> and typically about <NUM>. The adhesive is placed in the open end without projecting from the contact surface of the axial face.

As shown in <FIG> the initial penetration of the cannula <NUM> by the contact of the hub projecting from the contact surface with the skin of the patient forms depression <NUM> in the skin <NUM> and an initial cannula penetration depth. The surface of the skin then relaxes as shown in <FIG> so that the surface of the skin conforms substantially to the shape of the contact surface and limits the depth of penetration of the cannula <NUM>. In <FIG> the delta (Δ) refers to the distance between the axial end of the inner ring <NUM> and the subcutaneous layer of the skin. The invention is directed to the shape, surface area and height of the contact surface to provide control of the depth of penetration of the cannula during the insertion and penetration force being applied to the injection device.

The cannula <NUM> in the embodiments shown has length of about <NUM> to <NUM>, typically about <NUM> to penetrate the skin to the desired depth for the efficient delivery of the drug and particularly insulin. The contact surface of the hub has a width and height to control the deformation and dimension of the indentation in the skin thereby controlling the depth of penetration of the cannula. The shape and dimension of the contact surface distribute the applied pressure upon full engagement to the skin surface. The contour in combination with the pressure distribution provides improve comfort to the patient. The height and surface area of the hub and the perimeter surface area influence the degree of compression and relaxation of the tissue for a given application force.

The hub <NUM> in the embodiment of <FIG> has a body portion <NUM> having a side wall <NUM> with internal threads <NUM> for coupling with the pen delivery device. The distal end of the side wall has a peripheral edge <NUM> and forms a shoulder <NUM> extending between the peripheral edge <NUM> and a base <NUM> of a post <NUM> forming the distal end of the hub. The post <NUM> projects outward in an axial direction of hub <NUM> to support cannula <NUM>. As shown in <FIG>, post <NUM> extends outward from shoulder <NUM> and has an axial face forming a contact surface <NUM>. In this embodiment, contact surface <NUM> has a continuous curved convex shape extending from peripheral edge <NUM> to the opening for receiving cannula <NUM>. Contact surface <NUM> has a dome shape with a substantially uniform curvature forming a semispherical shape having an axial height <NUM> of about <NUM> to about <NUM> from the peripheral edge <NUM> to the portion around the cannula <NUM> and the outermost distal portion of the contact surface <NUM>. In one embodiment, the contact surface can have a height of about <NUM> to <NUM>. The contact surface <NUM> can have a continuous curvature with a radius of curvature of about <NUM> to <NUM>. In one embodiment, the contact surface has a radius of curvature of about <NUM> to <NUM>. The curved contact surface can have surface area of about <NUM>-<NUM><NUM>. In one embodiment, the curved contact surface can have a surface area of about <NUM> to <NUM><NUM>. The contact surface can have a substantially flat annular portion surrounding the cannula <NUM> that is oriented in a plane substantially perpendicular to the axis of the cannula as shown. The flat annular portion can have a diameter of about <NUM> to about <NUM>.

The hub <NUM> has a centrally located passage <NUM> for supporting cannula <NUM> and a recessed open end <NUM> for receiving an adhesive <NUM> as shown in <FIG> to fix cannula <NUM> to hub <NUM>. The recessed open end <NUM> can have inclined surfaces <NUM> forming a funnel shaped recess to receive the adhesive. In the embodiments shown, adhesive <NUM> fills a portion of the recessed open end <NUM> so that the adhesive is below the contact surface or substantially flush with the contact surface to minimize contact of the adhesive the skin and prevent or minimize alteration of the contact surface with the skin of the patient. The open end <NUM> can have diameter of about <NUM> to <NUM>.

In another embodiment of the invention shown in <FIG>, a hub <NUM> has a side wall <NUM> extending from a base <NUM> with a distal contact surface <NUM>. Side wall <NUM> in the embodiment shown has opposing flat portions <NUM> so that the contact surface <NUM> has a non-circular shape.

Contact surface <NUM> in the embodiment of <FIG> is defined by an outer ring <NUM> forming a collar defining the peripheral edge of contact surface <NUM> and projecting axially outward from the distal end of the hub <NUM> and surrounding cannula <NUM>. Outer ring <NUM> has a substantially uniform height from the distal end of the side wall <NUM> with a distal outer face <NUM> forming a peripheral edge of contact surface <NUM>. An inner, substantially annular shaped ring <NUM> extends axially from contact surface <NUM> around the opening <NUM> for receiving the cannula <NUM> and adhesive. For clarity the adhesive is not shown in <FIG>. Inner ring <NUM> has a substantially cylindrical or annular shape projecting outward and forming an inner edge of contact surface <NUM>. Inner ring <NUM> has a distal outer face <NUM> forming part of the contact surface <NUM> surrounding cannula <NUM>. Inner ring <NUM> and outer ring <NUM> define a recess <NUM> of contact surface <NUM> extending between an inner surface <NUM> of outer ring <NUM> and an inner surface <NUM> of inner ring <NUM>. In one embodiment, recess <NUM> has a width and depth so that the bottom surface of recess <NUM> contacts the skin of the patient during penetration of cannula <NUM> to control the compression of the skin and depth of penetration shown in <FIG>.

Contact surface <NUM> in the embodiment shown has a substantially convex shape with a height and width to provide the desired control of the compression of the skin and the depth of penetration of cannula <NUM>. The distal outer face <NUM> of contact surface <NUM> as shown has an incline with respect to the axial dimension of hub <NUM> converging toward the outermost portion of contact surface <NUM> at the cannula <NUM> and having a substantially frustoconical shape. The distal face <NUM> of inner ring <NUM> has a similar shape inclined surface with a frustoconical shape aligned with distal outer face <NUM>. In one embodiment distal face <NUM> and distal outer face <NUM> at aligned to form a convex shape having a radius of curvature as shown in <FIG>.

Bottom surface of recess <NUM> as shown in <FIG> is also formed at an incline forming a frustoconical surface with a dome or semispherical shape and having a radius of curvature substantially the same as the radius of curvature of the contact surface of the inner ring and the outer ring. In the embodiment shown, the bottom surface is formed substantially concentric to the outer surface <NUM> of outer ring <NUM> and outer surface <NUM> of inner ring <NUM>. The depth of recess <NUM> is substantially uniform and is about <NUM> to <NUM> relative the axial length of inner ring <NUM> and outer ring <NUM>. In the embodiment shown outer ring <NUM> and inner ring <NUM> have substantially the same axial length. The depth of recess <NUM> relative to the width or diameter of the contact surface <NUM> enables the skin to deform by the insertion pressure while controlling the depth of penetration of cannula <NUM>. In other embodiments, the recess can have a depth of about <NUM> to about <NUM> and a distal contact surface can have a width or diameter of about <NUM> to about <NUM> and a height of about <NUM> to about <NUM>.

Referring to <FIG> the insertion pressure applied to hub <NUM> causes cannula <NUM> to penetrate the skin to a selected depth and the contact surface <NUM> to contact the skin. As shown in <FIG>, recess <NUM> has a depth relative to the width of contact surface <NUM> so that the skin contacts the bottom surface of recess <NUM> to provide a pressure against the skin to deform or depress the surface of the skin in a manner to control the depth of penetration of the cannula into the skin of the patient. The convex contact surface distributes the pressure across the contact area of the skin. The larger the surface area generally results in less deformation of the skin to prevent deep injections and less discomfort to the patient.

The annular recess <NUM> can have a radial width of about <NUM> to about <NUM>. The recess can have a volume of about <NUM> to <NUM>µl depending on the width and depth of the recess. In one embodiment the recess can have a volume of about <NUM> to <NUM>µl. The annular recess can have a radial width greater than the radial width of the inner ring and/or the outer ring. In the embodiment shown in <FIG>, the recess has a radial width that is greater than the combined width of the inner ring and the outer ring so that the bottom wall of the annular recess forms a major portion of the contact surface.

The distal contact face of the hub can have various configurations for providing the desired control for the depth of penetration of the cannula. In each embodiment, the distal contact face has a width or diameter to provide a sufficient surface area and height defined by the curvature of the contact face to minimize the depressing of the skin that can cause the cannula to penetrate the skin deeper than intended.

In the embodiment of <FIG> the hub <NUM> has a similar configuration to the embodiment of <FIG> except for the annular recess <NUM> having a substantially flat bottom surface <NUM> that extends substantially perpendicular to the axis of the cannula. The hub <NUM> has an outer ring <NUM> and an inner ring <NUM> extending axially that form the recess <NUM> and the bottom surface <NUM>. In this embodiment, the inner ring <NUM> has an axial height greater than the axial height of the outer ring <NUM>. The inner ring <NUM> has an axial distal face <NUM> having a curved surface that slopes toward to the outer peripheral edge of the hub <NUM>. The outer ring <NUM> has an axial distal face <NUM> having a curved surface that also slopes radially outward toward the peripheral edge.

The axial distal face <NUM> of the outer ring <NUM> and the outer distal face <NUM> of the inner ring <NUM> form the skin contact surface and define the width and height of the contact surface. The inner ring <NUM> extends in an axial direction a distance greater than the outer ring <NUM> to define the height of the contact surface. As in the previous embodiments, the contact surface can have a height of about. <NUM> to about <NUM> and a width of about <NUM> to <NUM>.

The axial distal face <NUM> of the outer ring <NUM> and the axial distal face <NUM> of the inner ring <NUM> in the embodiment shown have a round, curved surface to define a radius of curvature of the contact surface in a manner similar to the embodiment of <FIG>. The annular recess in this embodiment has a depth that can receive the skin as the skin deforms when the insertion pressure is applied although the skin typically does not contact the bottom surface of the recess.

In another embodiment shown in <FIG> the hub <NUM> is defined by a substantially cylindrical side wall <NUM> extending axially from the base <NUM>. The hub <NUM> has a distal face <NUM> forming a skin contact surface. The distal face can have a width of about <NUM> to about <NUM> and typically about <NUM>. As shown in <FIG>, the distal face <NUM> has an inner ring <NUM> extending axially from an inner portion of the distal face <NUM> and defining the center opening <NUM> for the cannula <NUM>. In the embodiment shown the inner ring <NUM> has an axial length of about <NUM> to about <NUM> and a diameter of about <NUM>-<NUM> and a surface area of about <NUM>-<NUM>.

The distal face <NUM> has an inclined distal surface <NUM> with a substantially dome or semispherical shape extending between the peripheral edge <NUM> and the base <NUM> of the inner ring <NUM>. The inclined distal surface <NUM> has a radius of curvature of about <NUM> to about <NUM> to form a continuous arc and radius of curvature. The inner ring <NUM> has an annular distal face <NUM> that is inclined to complement the incline and curvature of the distal surface <NUM>.

In one embodiment the distal face <NUM> of the ring <NUM> has a semispherical shape with a radius of curvature substantially the same as the radius of curvature of the distal surface <NUM> so that the surfaces are concentric. The height of the inner ring <NUM> is selected to complement the width of the distal face so that the skin contacts the inner ring <NUM> and at least a substantial portion of the surface of the inclined distal surface during penetration of the cannula to control the depth of depression of the skin and the depth of penetration of the cannula. The contact surface can have a surface area of <NUM> to <NUM><NUM>. The inclined surface <NUM> can have a surface area of about <NUM> to <NUM><NUM>. The distal face <NUM> of the inner ring <NUM> can have a surface area of about <NUM> to about <NUM><NUM> and a diameter of about <NUM> to about <NUM>.

In the embodiment of <FIG>, the hub <NUM> has a cylindrical side wall <NUM> extending axially from the base <NUM>. The hub <NUM> has a distal face <NUM> forming the skin contact surface. A continuous outer ring <NUM> extends axially from the side wall <NUM> to define a peripheral edge <NUM> of the distal face <NUM>. In the embodiment shown, the outer ring <NUM> extends in an axial direction with a height of about <NUM> to about <NUM>. The inner and outer surfaces of the outer ring are substantially concentric and extend in an axial direction with respect to an axial dimension of hub <NUM>. The flat portion can have a radial width of about <NUM> to about <NUM>.

The distal face <NUM> is formed by a continuous inclined surface <NUM> forming a substantially continuous dome or semispherical shape with a radius of curvature of about <NUM> to about <NUM>. The inclined surface <NUM> forms a continuous surface surrounding the cannula <NUM>. In the embodiment of <FIG>, hub <NUM> has a central opening <NUM> for receiving the cannula <NUM>. The distal face <NUM> has a substantially flat annular shaped portion <NUM> surrounding the opening <NUM> and oriented in a plane substantially perpendicular to the axis of the cannula and the axis of the hub. The flat annular portion <NUM> can have a radial width extending between the inner edge of the inclined surface <NUM> and the opening <NUM> substantially equal to the width of the distal surface <NUM> of the outer ring <NUM>.

The distal surface <NUM> of outer ring <NUM> as shown in <FIG> is inclined radially outward with respect to the axis of the side wall <NUM>. The distal surface <NUM> has an outer peripheral edge <NUM> spaced axially from an inner edge <NUM>. In this embodiment the inner edge <NUM> is in a plane with the flat inner portion <NUM> that is substantially perpendicular to the axis of the cannula to define the distal face of the hub. The outer ring <NUM> defines a recess <NUM> in the distal face having a depth so that the inclined surface contacts the skin during the penetration of the cannula <NUM>. The recess <NUM> can have a volume of about <NUM> to <NUM>µl. As in the previous embodiments, the distal face for contacting the skin during penetration and insertion of the cannula has a width or diameter in its widest point of about <NUM> to about <NUM> and the recess formed by the outer ring <NUM> has a depth of about <NUM> to about <NUM>. In other embodiments, the recess can have a depth of about <NUM> to about <NUM>.

In a further embodiment shown in <FIG> the hub <NUM> has side wall <NUM> extending from a base <NUM> and a distal face <NUM> for contacting the skin of the patient during insertion of the cannula <NUM>. The distal face <NUM> includes an outer ring <NUM> extending axially from a peripheral edge <NUM> and an axially extending inner ring <NUM> forming an inner edge <NUM>. As shown in <FIG>, the outer ring as a distal face formed in the same plane as a distal face of the inner ring <NUM>.

The outer ring <NUM> is formed by a cylindrical outer surface extending from the side wall and a substantially parallel inner surface <NUM>. The distal face <NUM> in the embodiment shown is formed at an incline to slope radially outward from the center of the hub. The inner ring <NUM> has in substantially cylindrical inner surface <NUM> parallel with the inner surface of the outer ring <NUM>. An annular recess <NUM> is formed between the outer ring <NUM> and the inner ring <NUM>. In the embodiment shown, the recess <NUM> has depth of about <NUM> to about <NUM>, a volume of about <NUM>µl and a width or radius of about <NUM> to <NUM>. As in the previous embodiments, the recess has a width and a depth to enable the skin to contact the bottom face of the recess forming a central portion of the distal face forming the contact surface. The contact surface has a width of about <NUM> to <NUM>. Another embodiment shown in <FIG> and <FIG> is substantially the same as in <FIG> except for inner ring <NUM> and the outer ring <NUM> of the hub <NUM> forming a recess <NUM> having a depth of about <NUM> to <NUM> and a well volume of about <NUM>µl.

<FIG> show another embodiment of a needle hub <NUM> for attaching to a delivery pen as in the previous embodiments. The hub <NUM> has a base <NUM> with an outer wall <NUM> having an open bottom end and internal threads <NUM> for coupling to the delivery device. The wall <NUM> has a distal end <NUM> joined with an inwardly extending shoulder <NUM>. A substantially cylindrical shaped wall <NUM> extends axially from the shoulder <NUM>. The wall <NUM> has an axial distal face <NUM> defining a skin contact surface for contacting the skin of a patient during use.

The contact surface defined by the distal face <NUM> has substantially convex shaped forming a dome or semispherical shape depicted by line <NUM> in <FIG>. The distal face <NUM> can have a radius of curvature of about <NUM> to <NUM>. In one embodiment, the distal face <NUM> has a radius of curvature of about <NUM> to <NUM> and typically about <NUM>-<NUM>. The radius of curvature can be at least equal to the diameter of the contact surface.

The post <NUM> as shown in <FIG> has a substantially cylindrical shape formed by a side wall <NUM> extending from the shoulder <NUM>. The distal face <NUM> defining the skin contact surface also has a substantially circular shape when viewed from the top end shown in <FIG>. The distal face <NUM> is formed by an annular outer ring <NUM>, an annular inner ring <NUM> and an annular shaped recess <NUM> forming a well between the outer ring <NUM> and the inner ring <NUM>.

The outer ring <NUM> and the inner ring <NUM> in the embodiment shown have a height extending from the bottom wall <NUM> of the recess <NUM> to define the depth of the recess. The outer ring and inner ring have the same axial length so that the recess <NUM> has a substantially uniform and continuous depth extending between the outer radial edge and the inner edge of the recess. The outer ring <NUM> has an axial annular surface <NUM> that is inclined with respect to the axial dimension of the hub to form the convex distal face <NUM>. The incline of the axial face <NUM> conforms to the radius of curvature of the distal face <NUM>.

The inner ring <NUM> in the embodiment shown also has an axial face <NUM> with a curvature corresponding substantially to the curvature of the axial face <NUM> of the outer ring. The axial face <NUM> and axial face <NUM> are aligned along the curvature of the distal face <NUM> indicated by line <NUM>. In the embodiment shown, the axial face <NUM> and axial face <NUM> are substantially the same width with substantially the same radius of curvature. The bottom wall <NUM> of recess <NUM> has a radius of curvature that is substantially the same as the radius of curvature of the distal face <NUM> as indicated by line <NUM> so that the contour of the bottom wall <NUM> is substantially parallel or concentric to line <NUM>. The curvature of the distal face <NUM> defines a height of about <NUM> to <NUM> as measured from the outer edge of the outer ring to the axial face of the inner ring. In one embodiment the distal face <NUM> can have a height of about <NUM> to <NUM>.

The inner ring <NUM> defines a central opening <NUM> for receiving and mounting a cannula <NUM> as in the previous embodiments. The opening <NUM> can have a diameter of <NUM> to <NUM> for securing the cannula to the hub. In one embodiment, the distal face <NUM> forming the skin contact surface can have a diameter of about <NUM> to <NUM>. The radial dimension or width of the annular recess <NUM> can be equal to the combined radial width of the inner ring and the outer ring. In the embodiment shown, the annular recess has a radial width about twice the radial width of each of the inner and outer rings. The axial face <NUM> and axial face <NUM> each can have radial width of about <NUM> to <NUM> and the annular recess <NUM> can have a radial width of about <NUM> to <NUM>. The annular recess can have a depth of about <NUM> to about <NUM> and typically about <NUM>. The cannula can have an axial length of about <NUM> to <NUM>. The combination of the cannula length with the distal contact surface having a radial diameter and height as defined herein provide control of the depth of penetration of the cannula during insertion into the patient. The width and curvature of the distal face provide the controlled depression of the skin to reduce the incidence of that cannula penetrating the skin to a depth deeper than desired during the drug delivery.

In various embodiments, the inner ring can have a diameter of about <NUM>-<NUM> and generally about <NUM>-<NUM> with a surface area of about <NUM>-<NUM><NUM>. The inner ring can have a height of about <NUM>-<NUM> as measured from the outer periphery of the contact surface. The ratio of the diameter (D) of the inner ring to the height of the inner ring can range from about <NUM>:<NUM> to about <NUM>:<NUM> and generally about <NUM>:<NUM> to <NUM>:<NUM>. The larger larger ratio provides a greater surface area that provides increased comfort to the patient and greater control of the insertion depth.

The depth of the recess can vary depending on the desire depth of penetration by the cannula. The radial dimension of the annular recess is typically greater than the radial dimension of the inner and outer rings. In the embodiment shown the radial dimension of the annular recess is greater than the combined radial dimension of the inner and outer rings. Generally the greater the depth of the recess the small contact surface area of the distal face and more deformation of the skin surface enabling deeper penetration by the cannula. The curvature of the distal surface of the inner and outer rings forming the contact surface can also vary. In the embodiments illustrated, the distal surface of the inner and other rings are substantially the same. In other embodiments, the distal surface of the inner ring can have a radius of curvature that is greater or smaller than the radius of curvature of the outer ring. In further embodiments, the distal surfaces of the inner ring and/or the outer ring can be substantially flat and formed in a plane substantially perpendicular to the axis of the cannula.

The hub device is suitable for use in a method of reducing shallow injections and for injecting a drug to a patient. The method includes providing a pen body having a medication compartment and a distal end configured for receiving a pen needle. The pen needle includes a hub having base with a recess on a proximal side for receiving and coupling to the pen body. As distal face and an opening extends between the proximal side and the distal face. The distal face of the hub has a diameter greater than about <NUM>. At least a portion of the distal face has a convex surface with a radius of curvature of about <NUM> to <NUM>. It has been found that a hub having a width of about <NUM> to <NUM> and a radius of curvature of about <NUM> to <NUM>. In various embodiments the radius of curvature of the distal face forming the skin contact surface can be about one to one and a half times the diameter of the distal surface <NUM> to form a small curvature and a height of about <NUM>. A cannula is received in the opening in the hub and has a beveled end for injecting into the subject's skin, and a proximal end for positioning in the medication compartment of the pen body. The cannula is inserted into the subject's skin where the convex surface contacts the skin to limit the depressing and deforming the surface of the skin to control the depth of penetration of the cannula.

Claim 1:
A pen needle, comprising:
a hub having a recess on a proximal side for receiving a medication pen body and a distal face forming a skin contact surface; and
a cannula received in the hub and extending from the distal face, the cannula having a distal end for injection into a subject's skin and a proximal end for positioning in a medication compartment of the medication pen body,
wherein the distal face comprises:
an annular outer portion at a peripheral edge of the distal face;
an annular inner portion surrounding the cannula; and
an annular recess extending between the annular outer portion and the annular inner portion, wherein the annular recess forms a continuous convex surface.