Patient-contact activated needle stick safety device

A device that is used in conjunction with a needle-based medication injection device (e.g. a prefilled syringe) that prevents needle stick injuries. The used needle is shielded by a needle guard that surrounds and extends beyond the needle tip. In a preferred embodiment, before the needle is inserted into the patient, the needle guard projects forward to substantially hide visibility of the needle for safety and to reduce patient anxiety.

FIELD

The following describes a device that is used in conjunction with a needle-based medication injection device (e.g. a prefilled syringe) that prevents needle stick injuries. The used needle is shielded by a cylindrical needle guard that surrounds and extends beyond the needle tip. In a preferred embodiment, before the needle is inserted into the patient, the needle guard projects forward to protect and substantially hide visibility of the needle to reduce patient anxiety.

BACKGROUND

The glass syringe and rubber stopper have for years provided an ideal drug storage closure having unique properties of impermeability to oxygen, low extractables, biocompatability, durability, etc. However, they are both formed by processes that do not lend themselves to tight geometrical tolerances. For instance, the syringe flange is formed when a glass tube is heated to a soft state and the edges pressed over to form an edge. Typical tolerances for the inside length of a syringe or the length of a stopper are both +/−0.5 mm. The finger flange thickness has a similar tolerance. Furthermore, tight tolerances were not originally needed by these devices because they were not used mechanically with other devices. Existing passive anti-needle stick safety devices for prefilled syringes must mount to the syringe but not interfere excessively with the force required to move the plunger rod during injection nor prevent the full travel of the plunger rod, which terminates when the stopper reaches the distal end of the inside of the syringe. The safety mechanism necessarily must be triggered toward the end of administration of the drug (near the end of the plunger rod travel). However, since virtually all safety devices locate the syringe against the safety device at a point under the syringe finger flange, a stack up of worst-case tolerances can put the required plunger rod travel variance at +/−1.5 mm, when considering the tolerances of the inside length of the syringe, syringe flange thickness, and stopper length (syringe manufacturers reference the syringe inside length from the proximal end of the syringe, not the distal underside of the finger flange). Accommodating the 3 mm plunger rod position variance is very difficult for safety devices and it is desirable to reduce and or eliminate any dependence of the safety device on the syringe and stopper tolerances.

SUMMARY

The present safety device described herein is directed to a needle guard for a syringe having the safety device triggering mechanism independent of the syringe and stopper tolerances. The present device is triggered when the needle guard body is displaced proximally relative to the device as the needle is inserted into the patient. The triggering point is broadly placed between point C and an angled step-down feature proximal to point C (FIG. 4A). As long as the needle guard body is displaced proximally a certain distance, the device will lockout, in a manner which is almost completely independent of the syringe or stopper geometry.

The present safety device also makes locking the needle shield completely contemporaneous with needle removal from the patient, reducing the possibility of needle stick injuries when, for instance, a patient suddenly jerks or flinches causing the needle to come out of the patient unexpectedly. Most commercially available needle safety devices require the plunger rod to be fully depressed in order to activate the safety mechanism.

Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description.

DETAILED DESCRIPTION

The present safety device described herein is directed to a needle guard for a syringe having the safety device triggering mechanism independent of the syringe and stopper tolerances. The fully assembled safety device10is shown inFIG. 1. The assembly of the device10comprises a main body60with a plunger22emanating proximally from the proximal end68and a rigid needle shield (RNS)40and RNS removal tool50emanating distally from the main body60. Inside the device10, as shown inFIG. 2, is a prefilled syringe20with an attached needle24with the RNS40covering over the needle24to protect the needle and maintain a sterile barrier for the medication injection pathways. At the distal end of the assembly is the RNS removal tool50, which is a removable covering over the RNS40that facilitates its removal just before injecting medication into the patient. The plunger22is attached to a syringe stopper26. At the distal end of the assembly inside the main body60is the needle guard body80, which is a tube that is concentric and interior to the main body60(seeFIGS. 2, 3, 5, and 6).

As shown inFIGS. 2 and 3, the needle guard body80is axially slide-able with respect to the rest of the main body60and is biased in a distal direction by a compression spring61positioned between a syringe flange34and the needle guard body80, and acting on a proximal end82of the needle guard body80. Initially, the needle guard body80is held in a proximal position by the RNS removal tool50. The RNS removal tool50is held in this position against the force of the spring61by retention barbs54that project outwardly at the proximal end55of the RNS removal tool50and that mate with corresponding retention windows62in the wall63of the main body60of the device10(seeFIGS. 3, 5, 11, 13-16).

Immediately before injecting medication into a patient, the RNS40, as depicted inFIG. 5, is removed by squeezing the RNS removal tool50, which collapses along two slits52that run along the side of the tool50starting at its proximal end55. The collapsed configuration of the tool50allows the retention barbs54at the proximal end55to disengage from the corresponding retention windows62in the main body60of the device10. An inwardly projecting capture lip75, at the proximal inside surface of the RNS removal tool50, grasps the proximal edge42of the RNS40, which in combination with the compressive force transmitted by the collapsed RNS removal tool50walls allows it to pull the RNS40from the distal end of the syringe20when the user pulls it in a distal direction (seeFIGS. 5, 16 and 17).

As the RNS removal tool50is withdrawn from the end of the device10, the needle guard body80slides forward, as shown inFIG. 6, to an intermediate stop point B as shown inFIGS. 4A and 4C, governed by the interference between one or more inwardly projecting protrusions64from the main body60and corresponding grooves90in the outer surface of the needle guard body80. The outer side of one protrusion64on the main body60is shown inFIGS. 3, 4B-4E, 5 and 6. They are positioned at the end of cut-out sections that provide flexibility to the protrusions arms65. The protrusions64interfere with the needle guard body grooves90by projecting into the groove space and controlling the movement of the needle guard body80against the distally directed force of the spring61and the proximally directed reaction force from the patient's skin.

Prior to removal of the RNS40, the protrusion64is in position A of the needle guard body grooves90as shown inFIGS. 4A and 4B. After the RNS40is removed, the needle guard body80moves distally in response to the force of the spring61, so that the protrusion64travels along a first groove section91to position B as shown inFIG. 4C. This includes some rotational movement of the needle guard body80as the protrusion64pushes against the angled wall of the first groove section91just before position B. This transition to position B includes a step92prior to groove deepening of the guard body groove90just prior to entering position B in a second groove section93to prevent the protrusion64from retracing its path back along the first groove section91toward position A.

As the needle24is inserted into the patient, the patient's skin pushes the needle guard body80proximally against the force of the spring61, such that the groove-protrusion90-64interface moves from position B along the second groove section93to position C as shown inFIG. 4A. Toward the distal end of the second groove section93, the groove depth steps down to a fourth, deeper groove section94along an edge96that is angled to the axis of the needle guard body80. At this point, the user must hold the device10against the skin working against the force of the spring61and perform the injection.

After the injection is complete and the device10is pulled away from the patient, the needle guard body80moves distally, as shown inFIG. 4D, under the force of the spring61from position C to position D with the protrusions64in the deeper groove section94such that the protrusions64encounter the stepped surface96causing the needle guard body80to rotate with respect to the main body60and enter a final groove section98in route to position D. As shown inFIGS. 4A, 4E and 4F, upon further distal movement of the needle guard body80, the protrusion64drops into a further deepening of the groove90at a groove recess99such that the protrusion64is substantially captured in the groove recess99in a locked out state. This engagement prevents relative motion of the needle guard body80with respect to the main body60.

As the needle guard body80moves from position C to position D as the needle24is pulled from the patient, it is projected distally around the needle24to the extent that it protects the caregiver and others from inadvertently being stuck by the needle tip25. As shown inFIGS. 4E and 4F, the needle guard body80is held in this needle-shielding position by interference of the protrusions64in the groove recess99at position D so that the needle guard body80cannot be pushed proximally with respect to the main body60, or pulled distally with respect to the main body60.

For patients that have limited hand strength, holding the device against the skin while the needle24is in the injection site, requires maintaining a force against the spring61that pushes against the needle guard body80(position C inFIG. 4A). An alternative embodiment of the device to lessen this axial force could be accomplished by increasing the angle of the stepped surface96in the deeper groove section94that starts proximally to point C as shown inFIGS. 4A and 4Dand deflects the main body protrusion64over to the straight groove section98that ends at position D. InFIGS. 4A and 4D, this angle is shown at about 45 degrees. An angle of perhaps 60 degrees would place a greater axial component of force against the spring force at some reduction of the lateral force. Of course, an angle of 90 degrees would hold the needle guard body80completely against the force of the spring61if the main body protrusion64could stay down in the deeper groove section94, but there would be no lateral deflection to get the main body protrusion64over to position D where the device10locks out into the desired safety configuration. Depending on the coefficient of friction between the main body protrusion64and the needle guard body80, the angle can be optimized to reduce the holding force for the patient, but still allow the main body protrusion64to lockout at position D shown inFIGS. 4A, 4E and 4F.

The sequence of steps to operate the device is described inFIGS. 5 through 10. First, as shown inFIG. 5, the RNS removal tool50is squeezed and pulled distally to remove the RNS40from the device. Squeezing the RNS removal tool50disengages the retention barbs54from the barb retention windows62and the capture lips75grip the proximal end of the RNS40, thus removing the RNS40as the RNS removal tool50is pulled distally outward from the device. As a result of the removal of the RNS40and the RNS removal tool50, the needle guard body80moves distally to the position shown inFIG. 6, under the force of the spring61.

A composite of 3 steps to inject medication is shown inFIGS. 7 and 8. In Step 1, the needle guard body80is placed against the patient's injection site100. In Step 2, the device10is pushed against the injection site100, causing the needle guard body80to move proximally with respect to the main body60allowing the needle24to enter into the injection site100. In Step 3, the plunger rod22is pushed forward to dispel the medication into the injection site100.FIG. 8also shows a cross-section of the device10with the needle guard80fully retracted and after the plunger22has been fully depressed.

InFIG. 9, the device10is being withdrawn from the injection site while the spring61pushes the needle guard body80distally. As the device10is fully withdrawn from the injection site100, the needle guard body80fully extends forward as shown inFIG. 10. At this point the main body protrusions64have entered position D in the groove98of the needle guard body80as shown inFIGS. 4E and 4Fand locked the needle guard body80from further motion with respect to the main body60to prevent any needle sticks.

To facilitate movement of the main body60and its protrusions64with respect to the grooves90of the needle guard body80, one or both components can be made using a plastic resin with ample lubrication (e.g. high content of mold release). Alternatively, dissimilar plastic resins exhibiting a low mutual coefficient of friction can be used for the components.

It is to be understood that there exist alternative arrangements of components that would still fall within the scope of what is described and claimed within this application. For instance, the needle guard body80could be positioned on the outside of the main body with interior-facing grooves and outwardly facing protrusions on the main body80.

An alternative embodiment for the safety device is presented for use with light-sensitive drugs that require only minimal exposure to light. In this embodiment, the components of the device are made of opaque materials (e.g. plastic resins with pigments, tinted glass, etc.) that effectively block light from reaching the drug in the medication delivery device. However, drug injection instructions normally require the caregiver to inspect the drug to check that it is not cloudy, etc. prior to giving the injection. To achieve this, as shown inFIGS. 11 and 12the main body60and needle guard body80of the device10have diametrically opposed windows that are positioned with respect to each other such that they are not aligned until the RNS removal tool50and RNS40have been removed. After removal, when the diametrically opposed windows on the two components align, as shown inFIG. 12, they form a line of sight through the device10, which enables the caregiver to inspect the drug volume. Referring toFIG. 11, prior to the removal of the RNS40and RNS removal tool50, the main body window69is blocked internally by the outer surface of the opaque needle guard body80. InFIG. 12, after the RNS40has been removed and the needle guard body80has moved forward, the window69of the main body60is aligned with the window85of the opaque needle guard body80allowing visibility into the syringe20. A similar window is provided on the diametrically opposite side of the device10.

The RNS40, RNS removal tool50, and plunger rod22components would also be made of opaque materials to prevent light exposure at the ends of the device10. A covering (not shown) over the proximal end of the syringe with a hole for the plunger rod could also be created to provide additional light protection. Similarly, a second cover (158; seeFIG. 18A) could be placed over the distal end of the RNS removal tool to block light from entering the distal end.

The RNS40not only protects the needle24from being bent or its tip25from being damaged but it also forms one of the sterile barriers for the drug closure system. It must perform these functions before, during, and after sterilization and is therefore a complicated component that receives a tremendous amount of testing during the drug development and approval process. Since it has potential contact with the drug inside the syringe20, it becomes part of the specific drug closure system that receives regulatory approval and is therefore difficult to change after approval. They have become industry standard devices produced by specialized third party manufacturers. Nevertheless, they have limitations and deficiencies, namely that they can become difficult to remove from the syringe20after sterilization and storage, often requiring greater than 20N of force to remove. On a small part (approximately 0.25 inches in diameter, 1 inch long) such as this, it makes it difficult for healthcare workers to remove due to the small grasping area. Patients that perform self-administration, especially those with limited manual dexterity or strength (e.g. arthritic or multiple sclerosis patients) will find it extremely difficult to remove. Therefore, an added improvement of the present device10is to facilitate the RNS40removal. This is accomplished by the RNS removal tool50, which, as shown inFIGS. 13, 14, 15, 23 and 24, in addition to presenting a bigger surface area with which the user can grab, it also features some cam mechanisms to provide mechanical leverage in removing the RNS40. As depicted, the RNS removal tool retention barbs54reside inside the main body barb retention window62before the RNS40is removed. The lateral sides110of the barb54and the corresponding edges of the main body barb retention window62are angled, as shown inFIG. 13, such that as the RNS removal tool50is rotated, the barbs54push against the edge of the window62and are deflected radially inward as shown inFIGS. 14 and 17. The axial cam follower56on the RNS removal tool50, as shown inFIG. 14, has not yet acted against the main body axial cam profile66.

The mechanical advantage of the barbs54engaging the edges of the retention windows62provides a strong radial squeeze so that the inwardly projecting capture lips75on the RNS removal tool50further engages the proximal edge42of the RNS40as shown inFIGS. 17 and 22. This engagement cannot pre-exist sufficiently since the syringe20and RNS40must assemble into the device10, from the proximal to distal end of device10, with minimal resistance or disturbance to the RNS40seal as shown inFIG. 16. After the proximal end42of the RNS40is engaged by the RNS removal tool50, the axial cam follower56engages a sloped surface67of the main body axial cam profile66as shown inFIG. 15which places a mechanically advantaged axial force on the RNS removal tool50in a distal direction, creating a distal axial displacement and forming a gap between the main body60and the RNA removal tool50. Because of the radial and axial cam surface between the RNS removal tool50and the main body60, the RNS removal tool50pushes the RNS40off of the syringe20and needle24with much less effort on the part of the user than would normally be required.

Although this description has used a RNS40as an example, soft needle shields, which do not have a hard plastic outer shell, could equally be used in this application with minor changes to account for different geometry.

A further improvement to the device could be a distal end cap158(FIG. 18A) on the RNS removal tool50and a proximal inwardly projecting lip (not shown) that together would help contain the RNS40after it had been removed from the syringe20, preventing it from falling to the floor, etc.

The RNS removal tool50can also have large cut-through arrows51indicating the direction of rotation to the end user. It could also have large wings53extending radially outward to provide greater rotational mechanical advantage for the end user (seeFIG. 13).

The RNS removal tool50, as described above, pulls the RNS40off the syringe/needle24by radially collapsing at the proximal end of the RNS40. When the RNS removal tool50has completely pulled the RNS40off the syringe/needle24and the user relaxes their grip, the collapsed capture of the proximal end of the RNS40may no longer be present allowing the RNS40to unexpectedly separate and fall from the RNS removal tool50. An improved version of the RNS removal tool150is shown inFIGS. 18A and 18B, wherein an elastomeric insert157is placed inside the RNS removal tool150such that it nominally has a slight press fit against the RNS40, the fit being moderate enough to allow for installation of the RNS40from the proximal direction during syringe20insertion yet sufficient enough to maintain a frictional grip on the RNS40to prevent it from separating from the RNS removal tool150in the absence of any collapsing grip from the RNS removal tool150. The size and durometer of the elastomeric insert157is such that when the RNS removal tool150is rotated as inFIG. 14, the radial squeezing of the RNS removal tool150transmits a sufficient squeezing force against the RNS40through the elastomeric insert157so as to pull the RNS40from the syringe/needle24. Internal circumferential ribs may assist for transmitting a gripping force onto the RNS40.

For those applications where full inspection of the syringe drug contents is required before injection, the main body window69shown inFIG. 11can be elongated the amount of the syringe body as shown inFIG. 19. This would also require that the needle guard body80be transparent or have a corresponding window since the drug inspection may need to occur before the device is readied for administration.

In an alternate embodiment shown inFIGS. 20-24, the capture lip75of the RNS removal tool50, may come up over the syringe barrel20slightly when the device10is fully assembled. Consequently, when the RNS removal tool50is rotated during rigid needle shield40removal, the cam surface110on the RNS retention barbs54, presses against the main body retention window62, forcing the RNS removal tool arms58to press radially inward, causing the RNS removal tool capture lip75to press against the barrel of the syringe20rather than the RNS40. This is advantageous during the rotational portion of RNS40removal to avoid rotation of the soft needle shield46with respect to the syringe needle, which can affect the quality or sharpness of the needle prior to insertion into a patient. In this embodiment, as the RNS removal tool capture lip75presses against the barrel of the syringe20as it is rotated, the friction created between the two components will impart a force on the barrel of the syringe20to encourage rotation of the entire syringe—RNS assembly200(FIG. 25). It is expected that either the syringe—RNS assembly200will rotate with the RNS removal tool50, or due to the friction between the syringe flange34, spring61, and main body60(FIG. 26), the syringe—RNS assembly200will remain fixed and the RNS removal tool50will rotate around it.

As the RNS removal tool50rotates the axial cam follower56will encounter the main body axial cam profile66forcing the RNS removal tool50to move axially away from the syringe20. Once the axial cam follower56on the RNS removal tool50reaches the end of the main body axial cam profile66the user will be required to continue to pull the RNS removal tool50from the device10, which will be aided by the needle guard body80, powered by the spring61.

As the RNS removal tool50is moving axially away from the syringe20, the RNS removal tool capture lip75will be pressed against the barrel of the syringe20(FIG. 21). It will continue to remain in contact with the syringe20, even as it reaches the syringe neck down area28. Consequently, the RNS removal tool capture lip75will capture the RNS40as the RNS removal tool50is removed from the device10(FIG. 22). By captured, it is meant that the surface of the RNS removal tool capture lips75will slide radially inward and over the proximal end surface42of the RNS40. As the RNS removal tool50is removed from the device10it will pull the RNS40axially from the syringe20, ultimately removing it from the syringe20.

In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. For example, the reader is to understand that the specific ordering and combination of process actions described herein is merely illustrative, unless otherwise stated, and the invention can be performed using different or additional process actions, or a different combination or ordering of process actions. As another example, each feature of one embodiment can be mixed and matched with other features shown in other embodiments. Features and processes known to those of ordinary skill may similarly be incorporated as desired. Additionally and obviously, features may be added or subtracted as desired. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.