WO2024099535A1

WO2024099535A1 - Auto-injector with safety functionality

Info

Publication number: WO2024099535A1
Application number: PCT/EP2022/081013
Authority: WO
Inventors: Toby Cowe; Robert William BRUNS
Original assignee: Owen Mumford Ltd
Priority date: 2022-11-07
Filing date: 2022-11-07
Publication date: 2024-05-16

Abstract

The present invention provides an auto-injector including a housing for receiving a syringe having a plunger, a needle, and a barrel containing a dose of medicament. The auto-injector also includes a drive mechanism for driving the plunger from a first position to a second position to expel the dose from the barrel of the syringe through the needle at a front end of the auto-injector and a detector arrangement for detecting arrival of the plunger at the second position and for detecting removal of the needle from an injection site and for providing signals indicative of an occurrence time of each of the detected events.

Description

Auto-Injector with Safety Functionality

Technical Field

The present disclosure relates to an auto-injector for delivering a medicament from a syringe. In particular, the disclosure relates to an auto-injector which increases the likelihood of optimal and complete full-dose drug delivery.

Background

Injection devices, in particular auto-injectors, are commonly used to self-administer injections of medicament. Such auto-injectors are configured to receive a syringe containing the medicament in a barrel, and then drive a plunger of the syringe into the barrel in order to deliver the medicament. Typically, the driving of the plunger occurs without the need for any driving force to be applied by the user, other than perhaps a small amount of force to trigger the auto-injector.

During the delivery of a medicament from an auto-injector, the user is required to hold a front end of the auto-injector against the injection site in order to keep the needle penetrated in the injection site, while the medicament is delivered. Specifically, the user may be required to hold the needle in place while the plunger moves completely through the barrel, leading to a so-called ‘full-dose delivery’ of the medicament. In order to aid the user in this process, an auto-injector may be provided with an indication device that generates an indication corresponding to the stage of use of the device.

However, various factors can lead to a sub-optimal, or incomplete, delivery of medicament, despite the user holding the auto-injector against the injection site until the plunger has moved completely through the barrel.

An improved auto-injector is required to ensure optimal and complete delivery of the medicament.

Summary In accordance with a first aspect of the disclosure, there is provided an auto-injector as defined in claim 1 .

The arrival of the plunger at the second position may act as an indication of the completion of the delivery stroke. Advantageously, the occurrence times of the arrival of the plunger and of the removal of the needle provide a proxy for whether a full-dose delivery has optimally and completely occurred. For example, the auto-injector may determine, whether a bung of the syringe has relaxed between the occurrence times. Alternatively or additionally, the auto-injector may determine whether the delivered medicament has dissipated under the injection site (e.g. has been absorbed by the soft tissue) between the occurrence times. The detected events refers to the detection of the arrival of the plunger at the second position and to the detection of the removal of the needle from the injection site.

The housing may comprise a hinged door openable to receive the syringe into the autoinjector. The syringe may comprise a safety syringe. The safety syringe may comprise a safety mechanism to protect a user from the needle. The safety syringe may comprise a needle sheath. The needle sheath may be configured to cover the needle after use of the syringe. Alternatively or additionally, the safety syringe may be configured to cause the needle to retract within the barrel of the syringe.

The drive mechanism may comprise a drive spring configured to provide a force to drive the plunger from the first position to the second position. The drive spring may comprise a compression spring and/or a tension spring. The drive mechanism may comprise a plunger driver configured to abut the plunger and provide a force in order to drive the plunger.

The auto-injector may comprise a priming mechanism configured to prime the drive mechanism prior to operation of the release mechanism. The priming mechanism may be operated by movement of the door of the auto-injector.

The detector arrangement may be configured to measure an elapsed time from the arrival of the plunger at the second position, and to provide a signal indicative of the elapsed time being equal to or greater than a threshold time. Optionally, the detector arrangement may be configured to stop measuring the elapsed time at the occurrence time of the removal of the needle from the injection site. Advantageously, the measurement of the elapsed time between the occurrence time of the arrival of the plunger and the occurrence time of the removal of the needle may provide a proxy for whether a full-dose delivery has optimally and completely occurred. For example, the auto-injector may determine, based on the elapsed time, whether a bung of the syringe has relaxed. Alternatively or additionally, the auto-injector may determine, based on the elapsed time, whether the delivered medicament has dissipated under the injection site (e.g. has been absorbed by the soft tissue).

The threshold time may be a typical period of time taken for a resilient syringe bung to relax and expand. A typical syringe which may be used with the auto-injector may comprise a resilient syringe bung that has well-known properties. For example, the resilient syringe bung may have a typical amount by which it is compressed during medicament delivery. The compression may be caused by the force and pressure applied by the drive mechanism. The resilient syringe bung may subsequently expand from its ‘compressed’ state into a ‘relaxed’ state. The expansion may take a typical period of time that is well-known. This period of time may be referred to herein as a ‘relaxation time’. It will be appreciated that it is not necessary for the exact relaxation time to be known. Instead, it is sufficient to know the relaxation time approximately. The threshold time may then be chosen to be equal to or slightly longer than the relaxation time. For example, the relaxation time may be 1 , 2, 3, 4, 5, 6, or more seconds from after the end of the delivery stroke.

Advantageously, by comparing the elapsed time with a threshold time comprising the relaxation time, it can be determined whether or not the bung has expanded before or after the auto-injector is removed from the injection site. Since the expansion of the bung may result in more medicament being delivered from the syringe, this can be used to determine whether the full dose has been delivered or not.

The threshold time is optionally a typical period of time taken for a medicament to disperse into soft tissue.

After the delivery of medicament, the medicament may exist in the soft tissue that is immediately proximate to the needle. At this stage, the medicament may exist at a pressure high enough such that, if the needle were removed, the medicament would leak from the injection site. After a period of time, the medicament may disperse into, or be absorbed by, the surrounding soft tissue. This may result in a reduced pressure of the medicament such that leakage from the injection site would not occur. This period of time, referred to herein as ‘dispersion time’, may be well known. It will be appreciated that it is not necessary for the exact dispersion time to be known. Instead, it is sufficient to know the dispersion time approximately. The threshold time may then be chosen to be equal to or slightly longer than the dispersion time. For example, the dispersion time may be 1 , 2, 3, 4, 5, 6, or more seconds from after the medicament has been delivered.

Advantageously, by comparing the elapsed time with a threshold time comprising the dispersion time, it can be determined whether or not the medicament has dispersed before or after the auto-injector is removed from the injection site. Since the medicament may leak if it has not sufficiently dispersed before the auto-injector is removed, this can be used to determine whether the medicament has or will have leaked from the injection site.

The threshold time may be defined by the greater of the relaxation time and the dispersion time, in order to ensure that both times have elapsed. For example, if the relaxation time is known to be 4 seconds, and the dispersion time is known to be 3 seconds, the threshold time may be chosen to be 4 or 5 seconds, such that it is equal to or greater than the relaxation time. The threshold time may also be chosen to account for any uncertainty in either of these times. For example, if the relaxation time is approximately 4 seconds, the threshold time may be chosen to be 5 or 6 seconds, so that the relaxation time is likely to have passed by the expiry of the threshold time.

The detector arrangement may be configured to transmit the signals to an indicator arrangement, wherein the indicator arrangement is configured to provide an indication to a user based on a received signal. Advantageously, this allows a user to be notified of the status of delivery, with respect to how long the auto-injector was held against the injection site. The indication may notify the user that the plunger has arrived at the second position. The indication may notify the user that the needle has been removed from the injection site. The indication may notify the user of the duration of the elapsed time. Alternatively or in addition, the indication may notify the user of the relationship between the elapsed time and the threshold time, e.g. that the elapsed time is longer, shorter, or equal to the threshold time. The signals may be an alert signal configured to cause the indicator arrangement to provide an alert indication that the needle has been removed from the injection site before the expiry of the threshold time. Advantageously, this alerts the user to the fact that the delivery of the medicament was sub-optimal and/or incomplete. The user then may take any necessary action to combat negative effects. For example, with reference to the relaxation time of the bung, the indication may notify the user that slightly less than the full dose was delivered. As a further example, with reference to the dispersion time of the medicament, the indication may notify the user that the medicament may leak from the injection site.

The signals may be a completion signal configured to cause the indicator arrangement to provide a completion indication that the elapsed time is equal to or greater than the threshold time. Advantageously, this notifies the user to the fact that the delivery of the medicament was optimal and/or complete. More specifically, this notifies the user that the needle of the auto-injector may be removed with little to no risk of leakage of the medicament (either from the injection site, due to the medicament pressure, or from the needle, due to the bung expansion). The user may then remove the auto-injector from the injection site with the knowledge that the delivery is complete.

The indicator arrangement may be further configured to provide a progress indication to the user while the plunger is being driven to deliver medicament. More specifically, the indicator may provide the progress indication between the departure of the plunger from the first position and the arrival of the plunger at the second position. Additionally, the indicator may continue to provide the progress indication between the arrival of the plunger at the second position and either the removal of the needle from the injection site, or the elapsed time exceeding the threshold time. Alternatively, the indicator may provide a different indication once the plunger has arrived at the second position. For example, the different indication may indicate that the plunger movement is complete but that the auto-injector should continue to be held in place until the threshold time has elapsed.

The indicator arrangement may be configured to provide a visual, audible, and/or tactile indication. For example, the indicator arrangement may comprise an illumination device. For example, the indicator arrangement may comprise one or more light emitting diodes (LEDs) and/or a display screen. In such cases, and when the indicator arrangement is located on the auto-injector itself, the housing may comprise a viewing window through which the illumination device can be viewed. The indicator arrangement may comprise a sound emitter. The indicator arrangement may comprise a haptic feedback device.

The indicator arrangement may be located on the auto-injector, and wherein the detector arrangement is configured to transmit the signal to the indicator arrangement as an electrical signal.

Optionally, the indicator arrangement is a user device separate from the auto-injector, wherein the auto-injector further comprises a transmitter, and wherein detector arrangement is configured to transmit, via the transmitter, the signal to the indicator arrangement using a short-range transmission protocol.

The user device may comprise a handheld device. The user device may comprise a dedicated indication device for use with the auto-injector. Alternatively, the user device may comprise a mobile phone. In this case, the mobile phone may use a dedicated application for monitoring and/or interfacing with the auto-injector. The short-range transmission protocol may comprise Bluetooth (RTM).

The detector arrangement may detect departure of the plunger from the first position. One or more switches of the detector arrangement may be configured (as described below) to be actuated upon departure of the plunger from the first position. The detector arrangement may be configured to detect arrival or departure of the plunger from various positions during the delivery. For example, the detector arrangement may be configured to detect arrival or departure of the plunger from the first position, the second position, and/or one or more intermediate positions. References to detecting the position of the plunger may instead refer to detecting the position of the plunger driver, which naturally acts as a proxy to the plunger position.

The auto-injector may have a needle shroud at the front end of the auto-injector, wherein the needle shroud is configured to move forwardly into an extended position upon removal of the front end from the injection site.

The needle shroud may be forwardly biased by a shroud spring. The needle shroud may be configured to lock in the extended position to prevent access to the needle after removal of the front end from the injection site. The needle shroud may be biased forwardly into the extended position prior to operation of the drive mechanism, priming mechanism, and/or the release mechanism. The needle shroud may be configured to move rearwardly when the front end is pressed against the injection site. The needle shroud may be configured to move rearwardly prior to injection and may be configured to lock after injection. Rearward movement of the needle shroud may expose the needle and cause the needle to puncture the injection site. Rearward movement of the needle shroud may operate the release mechanism, thereby causing the drive mechanism to drive the plunger.

The detector arrangement may include a shroud sensor configured to sense a position of the needle shroud, wherein the detector arrangement detects the removal of the needle from the injection site responsive to the shroud sensor sensing that the needle shroud has moved forwardly into the extended position.

The detector arrangement may use the position of the needle shroud as a proxy for the position of the needle relative to the injection site. More specifically, the detector arrangement may use the position of the needle shroud as a proxy for whether the needle is embedded within, or removed from, the injection site. Advantageously, this allows a determination of whether or not an injection is ongoing or has been terminated. Advantageously, this reduces the need for other components on the auto-injector in order to sense whether the auto-injector is being held against the injection site. In addition, this may reduce the manufacturing complexity and cost of the auto-injector.

To this end, references herein to removal of the needle from the injection site, or similar, may interchangeably refer to movement of the needle shroud into the extended position, and vice versa. The extended position may correspond to full extension of the needle shroud from the front end of the auto-injector. Alternatively, the extended position may correspond to an extension of the needle shroud corresponding to the length of the needle.

The shroud sensor may be a switch. The shroud sensor may be a mechanical switch, a micro-switch, an electrical switch, a magnetic switch, and/or any other suitable switch known to the skilled person. The detector arrangement may comprise one or more switches. The one or more switches may comprise mechanical switches, micro-switches, electrical switches, magnetic switches, and/or any other suitable switches known to the skilled person. The one or more switches may be configured to be actuated upon arrival of the plunger at the second position.

The detector arrangement may comprise a trigger point coupled to the movement of the plunger. For example, the trigger point may be located on the plunger. Alternatively, the trigger point may be located on the plunger driver. The detector arrangement may comprise a switch coupled to the housing. The trigger point may be configured to actuate the switch upon relative movement between the trigger point and the switch. For example, the trigger point may comprise a first magnet and the switch may comprise a second magnet, the first magnet being configured to interact with the second magnet as the first magnet moves past the second magnet. Alternatively, the trigger point may comprise a rib and the switch may comprise a mechanical switch, the rib being configured to operate the switch as the rib moves past the switch.

The detector arrangement may comprise a proximity sensor for sensing the proximity of the front end to the injection site. The proximity sensor may be a mechanical sensor and/or an optical sensor. The proximity sensor may detect whether the needle is inserted into the injection site.

The auto-injector may include a release mechanism that, upon actuation, causes the drive mechanism to drive the plunger, wherein the release mechanism is configured to only allow actuation if the detector arrangement detects that the front end is in contact with the injection site.

For example, the release mechanism may be a trigger button. In this case, the trigger button may be in a locked state until the detector arrangement detects that the needle is embedded in the injection site (e.g. until it detects that the needle shroud is moved rearwardly by being pressed against the injection site). Alternatively, the release mechanism may be the needle shroud. In this case, the needle shroud is moved rearwardly by pressing the front end against the injection site, thereby causing the drive mechanism to drive the plunger. The auto-injector may also include a syringe having a plunger, a needle, and a barrel. The syringe may include a resilient bung. The auto-injector may further comprise a power supply to provide power to the detector arrangement, the indicator arrangement, and/or the drive mechanism.

In accordance with a second aspect of the disclosure, there is a system as defined in claim 19.

Brief Description of the

Exemplary embodiments will now be described with reference to the Figures, in which:

Figure 1 is a front view of an auto-injector containing a syringe, with a plunger in a first position;

Figure 2A is a magnified interior perspective view of the auto-injector of Figure 1 , with the plunger in the first position;

Figure 2B is a magnified interior perspective view of the auto-injector of Figure 1 , with the plunger in a second position; and

Figure 3 is a front view of the auto-injector of Figure 1 , with the plunger in the second position.

Detailed Description

Generally disclosed herein are exemplary apparatus for auto-injectors. The term “autoinjector” is used herein to refer to a device configured to receive a syringe and provide mechanical assistance to the user during delivery of medicament from the syringe. The auto-injectors may be configured to receive and operate a standard syringe (i.e. not a safety syringe) and/or a safety syringe.

In the following examples, the terms “forward” and “front” refer to the end of the autoinjector, or component thereof, that faces the injection site. The injection site will typically be a patient’s skin. In other words, the front end of the auto-injector is the end proximal to the injection site during use. Likewise, the term “rear” refers to the non-injection-site end of the auto-injector, or component thereof. In other words, the term “rear” means distal from the injection site during use. Further, the term longitudinal is used to encompass a direction along or parallel to a longitudinal axis, running from the rear to the front, of the injection device.

Features of the exemplary arrangements disclosed herein are described as being “coupled” to other features. This term encompasses any coupling that results in coupled features moving together in any direction. The term “coupled” also encompasses any one of a connection between features, an abutment of one feature against another, and an engagement of one feature with another, and such coupling may be direct or may be indirect, i.e. with a third feature therebetween.

In general terms, the disclosure is directed to improving the delivery of a medicament from an auto-injector by ensuring an optimal and complete delivery. By ‘optimal and complete’ it is meant that substantially all of the medicament present in the syringe is delivered to and absorbed by the injection site. It is an appreciation of the present Applicant that leakage can occur both from the injection site and from the needle once the auto-injector has been removed from the injection site, thereby resulting in sub- optimal or incomplete medicament delivery. The Applicant has appreciated that this leakage may occur through two separate mechanisms.

Firstly, a plunger of the syringe typically comprises a bung that is made of a resilient material, for example rubber. The bung is typically somewhat compressed during medicament delivery, and will subsequently ‘relax’ and expand after the plunger has completed its motion through the barrel. During this period of expansion, a small amount of medicament may be expelled from the syringe. If the auto-injector, or specifically the syringe needle, is removed from the injection site prematurely, this relaxation and expansion may lead to medicament being expelled outside of the injection site, leading to an incomplete dosage of medicament being delivered.

Secondly, after delivery, the medicament can be momentarily at a high pressure under the skin of the user. Over a short period of time, the medicament will dissipate into the surrounding soft tissue, leading to a reduction of the pressure. If the auto-injector, or specifically the syringe needle, is removed from the injection site prematurely, the medicament will not have yet dissipated and the high pressure can lead to some of the medicament leaking back out of the injection site. Exemplary auto-injectors disclosed herein provide signals indicative of the completion of the delivery stroke, and of the removal of the needle from the injection site. By providing these signals, it can be ensured that sufficient time is allowed for the bung to relax and/or for the medicament to disperse under the injection site before the needle is removed from the injection site, thereby reducing or effectively preventing the aforementioned leakage. The exemplary auto-injectors disclosed herein may also measure the time after the plunger has completed its delivery stroke, and optionally provide an indication to the user. The time may be measured until the auto-injector detects that the needle has been removed from the injection site.

Figure 1 depicts an exemplary auto-injector 100 that has a syringe 200 fitted within a housing of the auto-injector 100. The auto-injector 100 is depicted prior to delivery of medicament from the syringe 200. The housing of the auto-injector 100 comprises a main body 101 and a door 102, which may be hinged relative to the main body 101 . The door 102 is operable between an open position, in which the syringe 200 can be inserted, and a closed position. Figure 1 depicts the door 102 in the open position.

The auto-injector 100 comprises a viewing window 118 and an indicator arrangement 120. In Figure 1 , the viewing window 1 18 and the indicator arrangement 120 are depicted as being located on the door 102, but it will be understood that these components could be located elsewhere on the auto-injector housing. The indicator arrangement 120 may instead not be located on the auto-injector 100 at all, but instead be provided by a separate device. For example, the indicator arrangement 120 may comprise a separate user device configured to communicate with the auto-injector 100. In the Figures, the indicator arrangement 120 is depicted as an arrangement of four LEDs arranged in a circle. It will understood that other configurations of LEDs are possible. Furthermore, other indicator arrangements are contemplated herein, for example, audio or haptic indicators, or visual indicators other than LEDs.

The viewing window 118 allows a user to view inside the housing of the auto-injector 100. The specific purpose of the viewing window 118 will be described in detail below with respect to the injection process. The syringe 200 fitted into the auto-injector may be a safety syringe, as shown in the Figures. The syringe 200 comprises a plunger 202 for driving medicament from a barrel 204 and out of a needle 206. The forward end of the plunger 202 comprises a bung 208. The bung 208 is typically made of a resilient material. The bung 208 refers specifically to the portion of the plunger 202 that makes direct contact with the medicament contained within the barrel 204.

The auto-injector 100 also comprises a needle shroud 108, or simply ‘shroud’ 108. The shroud 108 is not shown in Figure 1 . When the cap is removed from the auto-injector the shroud 108 extends from the front end of the auto-injector 100. The shroud 108 is forwardly biased by a spring (not shown). Therefore, in its present state (i.e. prior to medicament delivery), the shroud 108 protrudes from the front end of the auto-injector 100, but may be pressed rearwardly (i.e. against the bias of the spring) in order to expose the needle 206. For example, the shroud 108 may be pressed rearwardly when the front end of the auto-injector 100 is pressed against the injection site, in order to insert the needle 206 into the injection site. The auto-injector further comprises a shroud sensor 1 16 that detects the position of the shroud 108 relative to the housing of the auto-injector (e.g. whether the shroud 108 is in an extended position).

The auto-injector 100 comprises a drive mechanism 104 for driving the plunger 202 from a first position 110a to a second position 110b. The first position 1 10a may be considered to be an initial position, and may refer to the position of the plunger 202 when it is fully removed from the barrel 204 such that no medicament has been delivered from the needle 206. The second position 110b may be considered to be a final position, and may refer to the position of the plunger 202 when it is fully inserted into the barrel 204 such that the full dosage of medicament has been delivered from the needle 206. In the Figures, the first position 110a and the second position 110b are labelled as respective positions of the plunger head (i.e. the distal end of the plunger). This is for illustrative purposes only and it is to be understood that the first and second positions refer generally to the positions of the plunger, and not necessarily to a particular portion of the plunger.

The drive mechanism 104 typically comprises a drive spring 105 and a plunger driver 106. The drive spring 105 provides a forward bias against the plunger driver 106, which is coupled to the plunger 202. Upon actuation of the auto-injector 100, the drive spring 105 drives the plunger driver 106 forwards, thereby driving the plunger 202, leading to medicament delivery. It will be understood by the skilled person that many different forms of drive mechanism are known for auto-injectors, and that the present disclosure may be applicable to auto-injectors with different forms of the drive mechanism 104.

The auto-injector 100 also comprises a release mechanism that, upon operation, causes the drive mechanism 104 to drive the plunger 202. As shown in the Figures, the release mechanism may be operated by the shroud 208. That is, upon depression of the shroud 208, the drive mechanism 104 is released in order to drive the plunger 202. In such cases, after fitting of the syringe 200 into the auto-injector 100, the user simply presses the front end of the auto-injector 100 against the injection site (thereby moving the shroud 208 rearwardly) and the injection process will commence. It will be understood that alternative forms of the release mechanism could be provided, for example, by way of a trigger button on the rear end of the auto-injector 100.

The injection process will now be described with reference to Figures 2A-3.

Figures 2A and 2B show the plunger driver 106 abutting the plunger 202. From these views, it can be seen that the auto-injector 100 further comprises a detector arrangement comprising a first switch 112a and a second switch 1 12b. In this example, the first switch 1 12a and the second switch 1 12b are magnetic switches, however, it will be understood that other forms of switches may be used.

Plunger driver 106 comprises a trigger point 1 14. The trigger point 1 14 is configured to interact with the first switch 1 12a and the second switch 1 12b as the trigger point 1 14 passes the respective switch. In this case, this means that trigger point 1 14 is a magnet that interacts with the switches. It will be understood that trigger point 114 could take a different form depending on the form of the switches. For example, trigger point 1 14 could be a protruding rib in the case of mechanical switches. Since the trigger point 114 is located on the plunger driver 106, the trigger point 1 14 is coupled to the plunger driver 106 and the plunger 202. In alternative arrangements, the trigger point 114 could be located directly on the plunger 202 itself.

Starting with Figure 2A, the plunger 202 is shown in a first position 1 10a. In this position, the plunger driver 106 is located such that the trigger point 114 is aligned with first switch 1 12a. In this position, the plunger 202 is fully extended from the barrel 204. In other words, this shows the position of the components prior to delivery of the medicament. Upon operation of the release mechanism, the plunger driver 106 begins to move forwardly, driving the plunger 202 into the barrel 204. The trigger point 114 will depart from the first switch 112a, thereby triggering the first switch 112a. This indicates the beginning of the delivery sequence, or delivery stroke. In response to the triggering of the first switch 1 12a, the detector arrangement may transmit a signal to the indicator arrangement 120, such that the indicator arrangement 120 provides an indication that the delivery sequence has started.

The plunger driver 106, and the plunger 202, continue to move forwardly along the autoinjector 100. During this time, the indicator arrangement 120 may provide an indication that the delivery sequence is ongoing.

Turning to Figure 2A, the plunger 202 has progressed to a second position 110b, which may correspond to a full-dose delivery of medicament from the barrel 204. In other words, the second position 110b may correspond to the bung 208 being at the front end of the barrel 204. Upon arrival of the plunger 202 at the second position 1 10b, the trigger point 1 14 is aligned with the second switch 112b. The arrival of the trigger point 114 at the second switch 112b triggers the second switch 112b. This indicates the end of the delivery sequence, or delivery stroke. In response to the triggering of the second switch 1 12b, the detector arrangement may transmit a signal to the indicator arrangement 120, such that the indicator arrangement 120 provides an indication that the delivery sequence has completed. Alternatively, the indicator arrangement 120 may continue to provide an indication that the delivery sequence is ongoing (since the user should not yet remove the auto-injector 100 from the injection site).

Alternatively or in addition, the plunger driver 106 may act as a visual indicator to the user that the delivery sequence is complete. As seen in Figure 3, the plunger driver 106, upon arrival at the second switch 1 12b, is aligned with the viewing window 1 18. The visible presence of the plunger driver 106 in the viewing window 1 18 acts as an indication that the plunger 202 has progressed to the second position 1 10b. The plunger driver 106 may comprise a visual indicator (e.g. a marking) to aid its visibility through the viewing window 118. Upon arrival of the plunger 202 at the second position 1 10b (i.e. once the second switch 1 12b has been triggered), the detector arrangement may provide a signal (e.g. by transmitting a signal to the indicator arrangement) indicating the arrival of the plunger 202 at the second position 1 10b. The detector arrangement may also begin measuring an elapsed time. The elapsed time indicates how long has passed since the delivery stroke was completed.

The detector arrangement may continue to measure the elapsed time until the shroud sensor 116 detects that the shroud 108 has extended. Upon extension of the shroud 108, the detector arrangement may provide a signal (e.g. by transmitting a signal to the indicator arrangement) indicating the removal of the needle 206 from the injection site. While the auto-injector 100 is being held against the injection site, the shroud 108 will be depressed into the auto-injector 100, as seen in Figure 3. Since the extension of the shroud 108 corresponds to the removal of the needle 206 from the injection site, the elapsed time will correspond to the total time that the auto-injector 100 was held against the injection site after delivery is complete. The elapsed time may be indicated to the user, for example by the indicator arrangement 120, so that the user knows for how long they held the auto-injector 100 in place after delivery was complete.

The detector arrangement may compare the elapsed time against a threshold time. The indicator arrangement 120 may provide an indication to the user based on the comparison of the elapsed time against the threshold time. For example, the indicator arrangement 120 may provide an indication that the elapsed time is less than, equal to, or greater than the threshold time.

The threshold time may be chosen based on the period of time it takes for the bung 208 to relax and expand after the delivery stroke is complete. The period of time may be referred to as the ‘relaxation time’. The threshold time may be chosen based on the period of time it takes for the delivered medicament to disperse into the soft tissue. The period of time may be referred to as the ‘dispersion time’. The relaxation time and/or the dispersion time may be values that are well-known or that can be calculated prior to the manufacture of the auto-injector 100. The threshold time may be chosen to be the longer of the relaxation time and the dispersion time. The threshold time may be, for example, 5 seconds. Once the second switch 1 12b is triggered, the detector arrangement begins measuring the elapsed time and comparing it with the threshold time. The indicator arrangement 120 may continue to provide an indication that the delivery is ongoing while the elapsed time is less than the threshold time. If the shroud sensor 116 detects that the shroud 108 has moved into the extended position (i.e. the user has removed the auto-injector 100 from the injection site) while the elapsed time is less than the threshold time, the indicator arrangement 120 provides an alert indication to indicate to the user that the auto-injector 100 was removed too early. Providing the auto-injector 100 is not removed too early, the indicator arrangement 120 may provide a completion indication to the user when the elapsed time equals the threshold time. This indicates to the user that the threshold time has been reached and the auto-injector 100 can be removed from the injection site. Once the shroud sensor 1 16 detects that the shroud 108 has moved into the extended position, the detector arrangement may cease measuring the elapsed time.

After the auto-injector 100 is removed from the injection site, as described above, by way of its forward bias, the shroud 108 moves into the extended position. In contrast to the extended position of the shroud 108 described with reference to Figure 1 , the shroud 108 may be locked in the extended position after delivery, such that the needle 206 can no longer be accessed. In other words, when in the extended position prior to delivery, the shroud 108 may be pressed against its bias (e.g. to begin the delivery sequence), but when in the extended position after delivery, the shroud 108 cannot be pressed against its bias.

The auto-injector 100 may be reset and reused by opening the door 102, removing the syringe 200, replacing with a new syringe, and repeating the above process.

Claims

CLAIMS:

1 . An auto-injector comprising: a housing for receiving a syringe having a plunger, a needle, and a barrel containing a dose of medicament; a drive mechanism for driving the plunger from a first position to a second position to expel the dose from the barrel of the syringe through the needle at a front end of the auto-injector; a detector arrangement for detecting arrival of the plunger at the second position and for detecting removal of the needle from an injection site and for providing signals indicative of an occurrence time of each of the detected events.

2. The auto-injector according to claim 1 , wherein the detector arrangement is configured to measure an elapsed time from the arrival of the plunger at the second position, and to provide a signal indicative of the elapsed time being equal to or greater than a threshold time.

3. The auto-injector according to claim 2, wherein the detector arrangement is configured to stop measuring the elapsed time at the occurrence time of the removal of the needle from the injection site.

4. The auto-injector according to claim 2 or 3, wherein the threshold time comprises a typical period of time taken for a resilient syringe bung to relax and expand.

5. The auto-injector according to any of claims 2-4, wherein the threshold time comprises a typical period of time taken for a medicament to disperse into soft tissue.

6. The auto-injector according to any of the preceding claims, wherein the detector arrangement is configured to transmit the signals to an indicator arrangement, wherein the indicator arrangement is configured to provide an indication to a user based on a received signal.

7. The auto-injector according to claim 6, wherein the signals comprise an alert signal configured to cause the indicator arrangement to provide an alert indication that the needle has been removed from the injection site before the expiry of the threshold time.

8. The auto-injector according to claim 6 or 7, wherein the signals comprise a completion signal configured to cause the indicator arrangement to provide a completion indication that the elapsed time is equal to or greater than the threshold time.

9. The auto-injector according to any of claims 6-8, wherein the indicator arrangement is configured to provide a visual, audible, and/or tactile indication.

10. The auto-injector according to any of claims 6-9, wherein the indicator arrangement is located on the auto-injector, and wherein the detector arrangement is configured to transmit the signal to the indicator arrangement as an electrical signal.

1 1. The auto-injector according to any of claims 6-10, wherein the indicator arrangement comprises a user device separate from the auto-injector, wherein the autoinjector further comprises a transmitter, and wherein detector arrangement is configured to transmit, via the transmitter, the signal to the indicator arrangement using a short- range transmission protocol.

12. The auto-injector according to any of the preceding claims, wherein the detector arrangement is further for detecting departure of the plunger from the first position.

13. The auto-injector according to any of the preceding claims, wherein the autoinjector comprises a needle shroud at the front end of the auto-injector, wherein the needle shroud is configured to move forwardly into an extended position upon removal of the front end from the injection site.

14. The auto-injector according to claim 13, wherein the detector arrangement comprises a shroud sensor configured to sense a position of the needle shroud, wherein the detector arrangement detects the removal of the needle from the injection site responsive to the shroud sensor sensing that the needle shroud has moved forwardly into the extended position.

15. The auto-injector according to any of the preceding claims, wherein the detector arrangement comprises a mechanical switch and/or a magnetic switch.

16. The auto-injector according to any of the preceding claims, further comprising a release mechanism that, upon actuation, causes the drive mechanism to drive the plunger, wherein the release mechanism is configured to only allow actuation if the detector arrangement detects that the front end is in contact with the injection site.

17. The auto-injector according to any of the preceding claims, further comprising a syringe having a plunger, a needle, and a barrel.

18. The auto-injector according to claim 17, wherein the syringe further comprises a resilient bung.

19. A system comprising: an auto-injector according to any of the preceding claims; and a user device configured to receive one or more indication signals using a short- range transmission protocol, and further configured to, responsive to receiving one or more indication signals, provide an indication corresponding to the received signal.