Patent Description:
Safety syringes typically include some form of safety mechanism to protect healthcare workers from a hypodermic needle of the syringe after it has been injected into a patient. Exemplary safety syringes may include a shroud or sheath for covering the needle after use of the syringe. Other exemplary syringes may cause the needle to retract within the barrel of the syringe.

Safety syringes may be broadly split into 'active' and 'passive' safety syringes. Active safety syringes typically require some action by a user of the syringe to engage the safety mechanism. Such action may be taken after removal of the needle from the patient, or may be taken during removal of the needle from the patient. Passive safety syringes typically engage the safety mechanism without any specific action by the user, that is, without any action other than that usually taken to use the syringe.

An auto-injector is a device for receiving a syringe and for driving a syringe plunger of the syringe into a barrel of the syringe, typically without any driving force being applied by the user, although some force may be required for activation. Typically, an auto-injector includes a plunger driver, such as a spring, that is arranged to provide a force to drive the syringe plunger into the barrel. The plunger driver is typically activated by operation of a button or other release mechanism on the auto-injector. A safety auto-injector may be one which includes a shroud that may be deployed to a position covering a needle of a syringe received within the auto-injector after use of the auto-injector. The shroud of the auto-injector may be deployed under a force applied by a shroud driver.

<CIT> describes an autoinjector with sensor means for detecting parameters of an injection, including a position of a plunger. Further relevant prior art can be found in <CIT>, <CIT>, and <CIT>.

According to the invention in an aspect, there is provided an auto-injector for use with a safety syringe, which may be a primed safety syringe, the auto-injector comprising: a first detector configured, after activation of the auto-injector, to detect movement of a plunger of the safety syringe to a point on a delivery stroke thereof that is indicative of full dose delivery of a substance from the safety syringe.

The auto-injector further comprises a second detector for detecting that the device is in an assembled state, which comprises engagement between a barrel portion and a plunger portion.

Optionally, the first detector is configured to be operable in dependence on the second detector having detected such engagement.

The auto-injector further comprises a third detector configured to detect the presence of the safety syringe.

Optionally, the first detector is configured to be operable in dependence on the third detector having detected the presence of the safety syringe.

According to the invention in a first aspect, there is provided an auto-injector for use with a safety syringe, the auto-injector comprising a main body that is openable for receiving the safety syringe and closable before operation of the auto-injector, the main body comprising a barrel portion configured to receive a barrel of the safety syringe and a plunger portion configured to receive a plunger of the safety syringe, wherein the barrel portion and the plunger portion are configured for detachable engagement, and wherein the main body is in the open position when the plunger portion and the barrel portion are detached.

A first detector is configured, after activation of the auto-injector, to detect movement of a plunger of the safety syringe to a point on a delivery stroke thereof that is indicative of full dose delivery of a substance from the safety syringe, whilst a second detector is configured to detect that the housing is assembled by detecting engagement of the barrel portion and the plunger portion. A third detector is configured to detect a presence of the safety syringe, whilst a processor is configured to receive an electrical signal from the first detector indicative of operation of the first detector.

The first detector is configured to be only operable to transmit a signal to said processor in dependence of at least one of the second detector having detected engagement between the barrel portion and the plunger portion and the third detector having detected the presence of the safety syringe.

Optionally, the main body comprises a hinged door openable for receiving the safety syringe and closable before operation of the auto-injector.

Optionally, the first detector comprises a switch, and optionally a micro-switch, operable by a part of the safety syringe during the delivery stroke of the plunger of the safety syringe.

Optionally, the switch is operable by the syringe plunger at a point on the delivery stroke indicative of a full-dose delivery.

Optionally, the point on the delivery stroke is reached before completion of the delivery stroke.

Optionally, a distance between the point on the delivery stroke and the point of completion of the delivery stroke is sufficient to account for manufacturing tolerances in the safety syringe.

Optionally, the auto-injector further comprises one or more indicators configured based on data received from the first detector to indicate whether the full dose was delivered. Optionally, the processor is configured to control a transmitter to transmit dose data to a user device, the transmitted data indicating whether the full dose was delivered.

Optionally, the processor is further configured to timestamp the dose data, the auto-injector further comprising a memory for storing the dose data, optionally until a connection to the user device is established by the transmitter.

Optionally, the second detector comprises a switch and optionally a micro-switch.

Optionally, the switch is operable by a feature of the barrel portion during engagement with the plunger portion, or wherein the switch is operable by a feature of the plunger portion during engagement with the barrel portion.

Optionally, the second detector is positioned in the plunger portion.

Optionally, the auto-injector further comprises a receiver configured to receive a signal emitted from a device of the safety syringe and comprising syringe data identifying one or more parameters related to the safety syringe.

Optionally, the receiver forms part of a Radio Frequency Identification, RFID, device configured to transmit a Radio Frequency, RF, signal to cause the device of the safety syringe to emit the received signal.

Optionally, the processor is configured to include the syringe data in the dose data for transmission by the transmitter.

The auto-injector may comprise a receiver configured to receive a signal emitted from a device of the safety syringe and comprising data identifying one or more parameters related to the safety syringe.

Optionally, the receiver forms part of a Radio Frequency Identification, RFID, device configured to cause the device of the safety syringe to emit the received signal.

Optionally, the one or more parameters related to the safety syringe comprise one or more of: the batch of a substance within the barrel of the syringe; the date that the barrel was filled with the substance; and an identification of the substance.

Optionally, the auto-injector further comprises a plunger driver for coupling to a plunger head of the syringe when the syringe is fitted within the auto-injector, and configured to drive a plunger into a barrel of the syringe, wherein the plunger driver is positioned on the auto-injector such that it is below the plunger head when the syringe is and fitted within the auto-injector.

Optionally, the plunger driver is positioned such that it is below the plunger head after use of the syringe.

Optionally, the plunger driver is configured to couple to at least one arm coupled to the plunger head and extending towards a needle end of the auto-injector when the syringe is fitted thereto.

Optionally, the plunger driver comprises at least one compression spring. Optionally, the spring forms a channel within the barrel portion configured to receive the syringe therein.

Optionally, the auto-injector further comprises a safety syringe.

Optionally, the syringe comprises: a plunger having a head; and at least one arm extending longitudinally from the head of the plunger towards a needle end of the safety syringe and configured to engage with the plunger driver, such that extension of the plunger driver drives the plunger into a barrel of the syringe.

The syringe for use within an auto-injector may comprise a device configured to emit a signal comprising data identifying one or more parameters related to the syringe.

Optionally, the device comprises an RFID tag.

Optionally, the one or more parameters related to the syringe comprise one or more of: the batch of a substance within the barrel of the syringe; the date that the barrel was filled with the substance; and an identification of the substance.

Exemplary embodiments of the invention are disclosed herein with reference to the accompanying drawings, in which:.

Generally, disclosed herein are auto-injectors for use with a syringe and/or a safety syringe. Exemplary auto-injectors comprise a first detector, which is be a delivery detector, configured to detect whether a plunger of a syringe within the auto-injector has reached a point on the delivery stroke that is indicative of full delivery of a substance, such as a drug, from within a barrel of the syringe. Other exemplary auto-injectors may comprise a receiver, which may be a Radio Frequency Identification (RFID) reader that forms part of an RFID system. The syringe may include an RFID tag that may emit a signal comprising data about the syringe and/or a substance contained in the barrel of the syringe.

In exemplary auto-injectors, a plunger driver (e.g. a compression spring) may be configured to apply a force to a plunger to drive it into a barrel of the syringe. The plunger driver may be located below a head of the plunger of a pre-filled syringe, which may be termed a primed syringe, received within the auto-injector. A syringe is considered to be primed when it contains a drug (or other substance) and has not been used, that is, when the plunger is drawn out of the barrel and there is a substance in the barrel for injection into a subject. Further, the term "below" the head of the plunger may encompass arrangements where the plunger driver is entirely below the head of the plunger. The plunger driver may be adjacent to or surrounding the barrel of the syringe. Because the plunger driver is not located above the plunger head, exemplary arrangements allow for the inclusion of other features in the space created, such as detectors, a processor, a transmitter and/or a receiver or RFID reader, which are discussed herein.

Exemplary plunger drivers may be fixed to the auto-injector at one end and configured to connect at an opposed end to one or more arms extending longitudinally from the head of the plunger towards a needle end of the syringe. Extension of the plunger driver towards the needle end applies a force to the one or more arms, thereby driving the plunger down into the barrel of the syringe. The syringe is be a safety syringe comprising a sheath connected to a head of a safety plunger by the arms, as described below. In such arrangements, a needle end of the plunger driver (e.g. a spring) may connect either to the arms or the sheath. In an exemplary arrangement, the plunger driver is located beneath an opening of the barrel of the syringe when fitted within the auto-injector. In a specific exemplary arrangement, the plunger driver is located beneath a flange at an opening of the barrel of the syringe when fitted within the auto-injector.

<FIG> shows an exemplary auto-injector <NUM>. The auto-injector <NUM> comprises a main body <NUM>. The main body <NUM> is configured to be openable for receipt of a syringe therein and closeable for operation of the auto-injector.

As will be appreciated by the skilled person, there are a number of ways in which an openable main body may be formed. In the specific embodiment shown in <FIG>, the main body <NUM> comprises a barrel portion <NUM> and a plunger portion <NUM>. The barrel portion <NUM> is configured to receive a barrel of a syringe. That is, the barrel of the syringe is at least partly contained within the barrel portion <NUM> when the syringe is fitted within the auto-injector <NUM>. The plunger portion <NUM> is configured to receive a plunger of the syringe when it is fitted within the auto-injector. That is, the plunger of the syringe is at least partly contained within the plunger portion <NUM> when the syringe is fitted within the auto-injector <NUM>. The barrel portion <NUM> and the plunger portion <NUM> may be configured for detachable engagement. The auto-injector may be opened by disengaging the plunger portion <NUM> from the barrel portion <NUM> and closed by re-engaging the plunger portion <NUM> and the barrel portion <NUM>.

In other arrangements, the main body <NUM> may comprise a hinged door. The hinged door may be moveable between an open position and a closed position. The hinged door may be positioned on a front face of the main body <NUM>. The hinged connection of the hinged door to the remainder of the main body <NUM> may be positioned at a rearward or plunger end of the main body.

When the hinged door is in the open position, the syringe may be received within the main body <NUM>. Specifically, when the hinged door is in the open position, a recess within the main body <NUM> may be exposed. The recess may be configured to receive and optionally retain the safety syringe ready for operation by the auto-injector.

The hinged door is moveable into a closed position for operation of the auto-injector. That is, when the hinged door is closed and a safety syringe is received within the main body <NUM>, the auto-injector may be in a state ready for operation.

In other arrangements, a door may be slidable or removable so as to expose the recess in the main body <NUM> and allow the safety syringe to be received therein. This and other arrangements will be readily understood by the skilled person.

The specific description below is provided in respect of the exemplary auto-injector <NUM> shown in the drawings. However, as will be readily understood, the relevant features of that auto-injector may be included in other exemplary auto-injectors, such as those mentioned above.

Generally, exemplary auto-injectors (and syringes) disclosed herein can be defined as having a needle end 100a and a plunger end 100b. These features will be used herein to aid description of the auto-injectors disclosed.

The auto-injector <NUM> further comprises a rigid needle shield (RNS) remover <NUM>. The RNS remover <NUM> is configured for slidable extension away from the barrel portion <NUM> from a first position, in which the RNS is fitted to the syringe, to a second position, in which the RNS is pulled away from a needle of the syringe. In other arrangements, the RNS remover <NUM> may be rotated to move it from a first position to a second position. The rotation may result in extension of the RNS remover <NUM> away from the barrel portion <NUM>. The RNS remover <NUM> may couple to an RNS of a syringe fitted within the auto-injector <NUM> such that extension of the RNS remover <NUM> removes the RNS. An aperture (not shown in <FIG>) in the RNS remover <NUM> allows the RNS of the syringe to fall from the auto-injector <NUM> after removal.

The barrel portion <NUM> comprises a housing configured to surround a syringe barrel received therein. The barrel portion <NUM> has a main body that is broadly elliptical in cross section. The main body extends away from the needle end 100a towards an opening at the plunger end 100b that is configured to receive the barrel of the syringe. The opening may be large enough to accommodate a finger flange at an opening of the barrel of the syringe or a handle portion that is fitted to the barrel. The handle portion may be configured to receive index and middle fingers of a user when the syringe is used outside of the auto-injector <NUM>. The opening of the barrel portion <NUM> is configured for removable connection to the plunger portion <NUM>.

The plunger portion <NUM> comprises a housing configured to surround the plunger of the syringe when fitted within the auto-injector <NUM>. The plunger portion <NUM> comprises a main body that is broadly elliptical in cross section. The main body of the plunger portion <NUM> extends away from a plunger end 100a towards an opening at the needle end 100a that accommodates the finger flange or a handle portion that is fitted to the barrel. The opening of the plunger portion <NUM> is configured for removable connection to the barrel portion <NUM>. The plunger portion <NUM> may further comprise a button <NUM> or other activation device for activating the auto-injector <NUM> when a syringe is fitted therein.

The RNS remover <NUM> is broadly elliptical or circular in cross section. The RNS remover <NUM> may comprise a lip <NUM> around a needle end thereof to provide greater grip for a user wishing to extend the RNS remover <NUM>.

<FIG> shows a section through an exemplary auto-injector <NUM> and <FIG> shows an exploded view of an exemplary auto-injector <NUM>. The auto-injector <NUM> comprises a barrel portion <NUM>, a plunger portion <NUM> and a RNS remover <NUM>. The barrel portion <NUM> houses a depth adjustor <NUM>, a contact actuator <NUM>, a carrier <NUM> and a body <NUM>. A safety syringe <NUM> is also shown in Figure 1a and this may be fitted within the auto-injector <NUM>.

The barrel portion <NUM> is configured for removable connection with the plunger portion <NUM>.

The plunger portion <NUM> may be configured for connection to the barrel portion <NUM> under a linear force applied by a user, and disconnected from the barrel portion <NUM> under a rotational force. The exemplary auto-injector <NUM> comprises discrete threaded sections on both the barrel portion <NUM> and the plunger portion <NUM>. The body <NUM> comprises a barrel thread <NUM>. The body <NUM> is configured to be fitted within an opening at a plunger end of the barrel portion <NUM> and comprises at least one guide configured to enter the plunger portion <NUM> when fitted to the barrel portion <NUM>. The barrel thread is formed on the guide. The plunger portion <NUM> comprises a corresponding plunger thread <NUM> positioned at an opening at a needle end thereof.

In the exemplary auto-injector <NUM>, the barrel thread <NUM> and the plunger thread <NUM> do not extend <NUM> degrees around the barrel portion <NUM> and the plunger portion <NUM>. Rather, the barrel portion <NUM> and the plunger portion <NUM> comprise a plurality of discrete threaded sections that are angularly separated from each other about an opening of the barrel portion <NUM> and the plunger portion <NUM>. In the auto-injector <NUM>, the barrel portion <NUM> and the plunger portion <NUM> comprise two threads formed at opposed sides of the openings of the barrel portion <NUM> and the plunger portion <NUM>, respectively.

In the exemplary auto-injector <NUM>, the linear force applied by the user to connect the barrel portion <NUM> and the plunger portion <NUM> may bring the barrel thread <NUM> and the plunger thread <NUM> into engagement. This may be by a snap fit or clip fit arrangement which causes the threaded sections to ride over one another under the applied force. Once the barrel thread <NUM> and the plunger thread <NUM> are engaged, the plunger portion <NUM> may be disconnected from the barrel portion <NUM> by the relative rotation of the barrel portion <NUM> and the plunger portion <NUM>, which moves the discrete barrel thread <NUM> out of alignment with the discrete plunger thread <NUM>.

The barrel portion <NUM> and the plunger portion <NUM> may be disconnected to allow the insertion of a syringe <NUM> into the auto-injector <NUM> and reconnected once the syringe <NUM> has been inserted. Further, when a syringe <NUM> is fitted within the auto-injector <NUM>, rotation of the plunger portion <NUM> with respect to the barrel portion <NUM> rotates the syringe <NUM> such that a part of the syringe <NUM> rides over a cam surface to translate the rotational movement of the syringe to linear movement, which acts to decouple the syringe from the barrel portion <NUM>. Alternatively, rotation of the syringe <NUM> by rotation of the plunger portion <NUM> deforms the coupling members retaining the syringe <NUM> within the barrel portion <NUM> such that the syringe is decoupled from the barrel portion <NUM>.

In exemplary arrangements, the barrel portion <NUM> (or the body <NUM> within the barrel portion <NUM>) may be shaped to interact with a handle portion <NUM> of a safety syringe <NUM> such that a cam surface <NUM> is formed. The cam surface <NUM> is configured to translate rotational movement of the safety syringe <NUM> into linear movement of the safety syringe <NUM>. In the example shown, the substantially oval opening in the body <NUM> interacts with the underside of the handle portion <NUM> of the syringe <NUM>, which forms a ramped surface, to produce the linear movement. This linear movement may release the syringe <NUM> from captive coupling with the barrel portion <NUM>, which may extract the syringe <NUM> from the barrel portion <NUM>.

The RNS remover <NUM> is configured for removable connection with the barrel portion <NUM>. The RNS remover <NUM> may be fully removed (i.e. separable) from the barrel portion <NUM>. The RNS remover <NUM> may be configured for reattachment to the barrel portion <NUM> after use of the auto-injector <NUM> by application of force by a user to insert features of the RNS remover <NUM> into the barrel portion <NUM>, as explained below.

The RNS remover <NUM> further comprises prongs 118a, 118b. The prongs 118a-b are configured to be received within the barrel portion <NUM> when the RNS remover <NUM> is connected to the barrel portion <NUM>. The prongs 118a, 118b comprise a spring compression surface that is configured to couple to the compression spring <NUM> when the RNS remover <NUM> is reconnected to the auto-injector <NUM> for priming the compression spring <NUM>.

The RNS remover <NUM> may connect to an RNS of a syringe <NUM> fitted within the auto-injector <NUM> such that removal of the RNS remover <NUM> from the barrel portion <NUM> removes the RNS. An aperture <NUM> in the RNS remover <NUM> allows the RNS of the syringe <NUM> to fall from the auto-injector <NUM> after removal of the RNS remover <NUM>. The RNS remover <NUM> may also comprise a dial component <NUM> configured to rotate the depth adjustor <NUM> and operation of which is explained below.

The depth adjustor <NUM> is configured to partially protrude from the barrel portion <NUM> of the auto-injector <NUM> before use thereof. The depth adjustor <NUM> may be brought into contact with the skin of a user once the RNS remover <NUM> has been removed. The depth adjustor <NUM> is configured to be slidably and/or rotatably received within the barrel portion <NUM> of the auto-injector <NUM>. Slidable movement of the depth adjustor <NUM> into the barrel portion <NUM> exposes the needle of the syringe <NUM> from a needle end of the depth adjustor <NUM> and therefore allows insertion of the needle into the skin of a patient. In the exemplary auto-injector <NUM>, the depth adjustor is slidably and rotatably received within the contact actuator <NUM>.

The depth adjustor <NUM> comprises lips 120a-b and a protrusion <NUM>. The lips 120a-b are configured to engage with a surface of the contact actuator <NUM> to limit extension of the depth adjustor <NUM> and therefore its protrusion from the barrel portion <NUM>. The depth adjustor may be biased towards a needle end 100a of the auto-injector <NUM> by a compression spring <NUM>. The protrusions <NUM> are configured to engage with a mechanical end stop to limit insertion of the depth adjustor into the barrel portion and therefore limit insertion of the needle into the patient.

The contact actuator <NUM> comprises an aperture within which the depth adjustor <NUM> is received. The depth adjustor <NUM> may be of a smaller diameter than the diameter of the aperture such that the depth adjustor <NUM> may be telescopically received by the contact actuator <NUM>. This arrangement allows axial and rotational movement of the depth adjustor <NUM> with respect to the contact actuator <NUM>.

It is noted that exemplary auto-injectors are configured for use with the safety syringe <NUM>. The exemplary syringe <NUM> shown in <FIG> and <FIG> is fitted within the auto-injector <NUM> and is a safety syringe. A plunger <NUM> is a safety plunger coupled to a sheath <NUM> and comprises a plunger head <NUM> and two arms 212a, 212b extending from opposed sides of the plunger head <NUM>. The arms 212a, 212b connect the plunger head <NUM> to the sheath <NUM>. The arms 212a, 212b are slidable along the outside of the barrel <NUM> such that the sheath <NUM> moves along the outside of the barrel <NUM> on application of a force to the plunger head <NUM>.

A handle portion <NUM> comprises a main body and flanges extending laterally from the main body. The main body comprises a portion that surrounds the barrel and is fixed thereto. The flanges form a finger grip and, when the safety syringe is used outside of the auto-injector <NUM>, are configured to receive the index finger and middle finger of a user while the thumb applies a force to the plunger head <NUM> of the safety plunger. The sheath <NUM> may be partially received within the main body of the handle portion <NUM> when the safety plunger <NUM> is at the outermost part of its stroke. At least a portion of the sheath <NUM> protrudes from the main body of the handle portion <NUM>.

The arms 212a, 212b of the safety plunger <NUM> pass through the handle portion <NUM> such that the safety plunger <NUM> may move along its stroke relative to the handle portion <NUM> and, therefore, the barrel <NUM>. The sheath <NUM> is configured to travel along the outside of the barrel <NUM> with the inward stroke of the safety plunger <NUM> until the sheath <NUM> at least partially covers a needle of the safety syringe <NUM>. At the innermost point of the stroke of the safety plunger <NUM>, the end of the sheath <NUM> is beyond the end of the needle, such that the sharp point of the needle is not exposed.

The safety plunger <NUM> is coupled to a syringe plunger <NUM> during a first part of its inward stroke and so the syringe plunger <NUM> is driven into the barrel <NUM> on movement of the safety plunger <NUM> along its inward stroke. The safety plunger <NUM> decouples from the syringe plunger <NUM> at a point on the inward stroke, which may be when the syringe plunger <NUM> has expelled all of a medicament or drug from the barrel <NUM>. After decoupling, the safety plunger <NUM> may move longitudinally relative to the syringe plunger <NUM> and continued movement of the safety plunger <NUM> moves the sheath <NUM> into a position covering the needle. In this sense, decoupling may refer to longitudinal decoupling. There may exist a rotational coupling of the safety plunger <NUM> and the syringe plunger <NUM> after longitudinal decoupling.

Decoupling of the safety plunger <NUM> and the syringe plunger <NUM> may be by means of relative rotation between the safety plunger <NUM> and the syringe plunger <NUM> to disengage one from the other. For example, a decoupling mechanism may comprise a lug on the syringe plunger <NUM> configured to move between engagement and disengagement with a coupling recess in the safety plunger <NUM>. The movement between engagement and disengagement may be by rotation of the syringe plunger <NUM> relative to the safety plunger <NUM>.

In some arrangements, the safety syringe <NUM> may comprise a rate controlling means for controlling a rate of travel of the safety plunger <NUM> after decoupling. The rate controlling means may comprise a rate limiting member coupled to the safety plunger <NUM> and configured to engage with the syringe plunger <NUM>. The rate limiting member may comprise a first screw thread <NUM> and the syringe plunger <NUM> may comprise a second screw thread that is configured to engage with the first screw thread <NUM> to rotate the syringe plunger <NUM> on linear movement of the safety plunger <NUM> after decoupling.

In such arrangements, the decoupling mechanism may comprise a rotation prevention member configured to prevent rotation of the syringe plunger <NUM> before decoupling. The rotation prevention member may comprise an aperture through which the syringe plunger <NUM> passes, wherein the aperture comprises first keying features configured to correspond to second keying features on the syringe plunger <NUM> such that the syringe plunger <NUM> is prevented from rotating. The syringe plunger <NUM> may be configured such that the second keying features disengage from the first keying features to decouple the syringe plunger <NUM> from the safety plunger <NUM>. For example, the syringe plunger <NUM> may be configured to pass through the aperture completely to linearly decouple the syringe plunger <NUM> from the safety plunger <NUM>.

The contact actuator <NUM> comprises castellation channels 124a-c. Three castellation channels 124a-c are visible in <FIG>, however exemplary auto-injectors may comprise any number of castellation channels 124a-c. The castellation channels 124a-c extend longitudinally (with respect to the auto-injector) from the needle end of the contact actuator <NUM>. The castellation channels 124a-c are different lengths. Each castellation channel 124a-c comprises a mechanical end stop surface at a plunger end of the castellation channel 124a-c. Because the castellation channels 124a-c are of different lengths, each mechanical end stop surface is located at a different distance longitudinally from the needle end of the contact actuator <NUM>.

The castellation channels 124a-c are configured to receive the protrusion <NUM> of the depth adjustor <NUM>. The depth adjustor <NUM> is rotatable within the contact actuator <NUM> to allow the protrusion <NUM> to align with the desired castellation channel 124a-c. The castellation channels 124a-c may be configured to allow the protrusion <NUM> to travel within one of the castellation channels 124a-c. The castellation channels 124a-c may be of substantially the same width as the protrusion <NUM> such that when the protrusion <NUM> enters one of the castellation channels 124a-c, rotation of the depth adjustor <NUM> is prevented and only longitudinal movement of the depth adjustor <NUM> is possible.

The mechanical end stop surfaces are configured to engage with the protrusion <NUM> of the depth adjustor <NUM> to set a mechanical limit on the extent of longitudinal movement of the depth adjustor <NUM> within the contact actuator <NUM>. The contact actuator <NUM> further comprises arms 130a-b comprising lugs 132a-b configured to engage with the carrier <NUM> to actuate a plunger driver <NUM> (e.g. a compression spring).

The carrier <NUM> is configured to retain the plunger driver <NUM> in a primed state. The term "primed state" encompasses a plunger driver <NUM> that is positioned such that it is capable of applying a biasing force. The plunger driver in the exemplary auto-injector <NUM> is a compression spring <NUM>. In the exemplary auto-injector <NUM>, the compression spring <NUM> is received within the carrier <NUM>. The compression spring <NUM> may be fixed to a biasing surface <NUM> of the carrier <NUM>. In alternative arrangements, the compression spring <NUM> may abut the biasing surface <NUM> without being fixed. The other end of the compression spring <NUM> may be fixed to or abut a surface of the body <NUM>.

The carrier <NUM> further comprises clips 138a, 138b located on opposed sides of the carrier <NUM>. Each clip comprises a sheath (or syringe) coupling member 140a, 140b and a locking member 141a, 141b joined by a base 142a, 142b. The sheath coupling members 140a, 140b and the locking members 141a, 141b are resiliently deformable. The sheath coupling members 140a, 140b are angled outwardly (with respect to the longitudinal) towards the body of the barrel portion <NUM>. The locking members 141a, 141b are angled inwardly (with respect to the longitudinal of the auto-injector) towards the centre of the barrel portion <NUM>. As such, each clip 138a, 138b is substantially v-shaped.

The compression spring <NUM> is received within the clips 138a, 138b such that one end of the compression spring <NUM> abuts the base 142a, 142b of the clips 138a, 138b and the resiliently deformable members 140a, 140b extend either side of the compression spring <NUM>.

The sheath coupling members 140a, 140b comprise a sheath coupling barb 146a, 146b. The locking members 141a, 141b, comprise a locking barb 147a, 147b. The sheath coupling barbs 146a, 146b are configured to engage with a corresponding recess on the sheath of the syringe <NUM> when the syringe <NUM> is inserted within the auto-injector <NUM>. The sheath coupling barbs 146a, 146b couple the sheath to the carrier <NUM> when the sheath coupling barbs 146a, 146b are engaged in the sheath recesses. The locking barbs 147a, 147b are configured to engage with a corresponding recess on the body <NUM>.

<FIG> shows an exploded view of a plunger portion <NUM> for use with auto-injectors disclosed herein and a plurality of components for fitting within the plunger portion <NUM>. The components comprise: an electrical circuit <NUM>, which in this case is printed on a printed circuit board (PCB) or equivalent; an insert <NUM> and a circuit cover <NUM>. The electrical circuit includes one or more processors and other electronic components configured to carry out any part of the methods described herein. In particular, the electrical circuit comprises the first, second and third detectors; a transmitter; a receiver; and a processor. The insert <NUM> is configured to be retained within the plunger portion <NUM> and comprises a channel <NUM> having an aperture at a needle end for accommodating a safety plunger <NUM>. The safety plunger <NUM> may travel along the channel <NUM> towards the plunger end when the syringe is fitted within the auto-injector.

When assembled, the PCB <NUM> is placed on the insert <NUM> by positioning locating lugs <NUM> within corresponding recesses in the PCB <NUM>. The circuit cover <NUM> is then secured to the insert <NUM>, for example by a snap-fit arrangement, by engaging pins within holes on the locating lugs <NUM>. The assembled features may then be secured in the plunger portion <NUM>.

<FIG> shows a section through a plunger portion <NUM> included the assembled circuit <NUM>, insert <NUM> and circuit cover <NUM>. The PCB <NUM> comprises a first detector <NUM>, a second detector <NUM> and a third detector <NUM>. In exemplary arrangements, the first second and third detectors <NUM>, <NUM>, <NUM> may be micro-switches forming part of the circuit printed on the PCB <NUM>. However, other means for detecting may be used. The PCB <NUM> may also comprise a plurality of differently coloured light emitting diodes (LEDs), or other visual indicators, and an audio output capable of outputting different audio tones.

In arrangements in which the main body <NUM> comprises a hinged door, at least part of the PCB may be positioned within the main body <NUM>. Alternatively or in addition, at least part of the PCB may be positioned on the hinged door. In such arrangements, at least part of the PCB may be positioned on an internal surface of the hinged door, such that the PCB is brought into contact with the primed safety syringe when the hinged door is closed. The PCB may be placed on an insert which may be fitted within the main body or on the hinged door.

The first micro-switch <NUM> may be delivery detector configured to determine whether a full dose delivery has occurred. The term "full dose delivery" encompasses delivery of substantially all of a substance, such as a drug or medicament, from a barrel of a syringe. In particular, the first micro-switch <NUM> protrudes into the channel <NUM> such that a part of the safety plunger <NUM> operates the micro-switch <NUM>, which in turn sends a signal to a processor <NUM> on the PCB <NUM>. In exemplary arrangements, the micro-switch of the first detector <NUM> may be configured to be operated in two opposed directions (e.g. towards the needle end and towards the plunger end) and is therefore be configured to detect insertion of the syringe into the plunger portion <NUM> and to detect full dose delivery. The first micro-switch <NUM> may be positioned at a point before a point of completion of the delivery stroke. That is, the first switch <NUM> is positioned to be operable by the safety plunger <NUM> before completion of the delivery stroke of the syringe plunger <NUM>. Therefore, the first micro-switch <NUM> is be positioned such that it is operated before full dose delivery. The distance between the position of the first micro-switch <NUM> and the point of completion of the delivery stroke is to accommodate manufacturing tolerances when manufacturing the syringe.

The second micro-switch <NUM> is an assembly detector that is configured to detect when the auto-injector is assembled, that is, when the barrel portion is engaged with the plunger portion <NUM>. The micro-switch of the second detector <NUM> is positioned in a recess <NUM> that is configured to receive a protrusion of the body <NUM> housed within the barrel portion <NUM>. As the barrel portion <NUM> and the plunger portion <NUM> are engaged, the protrusion enters the recess <NUM> and then operates the micro-switch <NUM>. This results in a signal being transmitted to the processor <NUM>. In arrangements in which the main body <NUM> comprises a hinged door, the second micro-switch may be suitably positioned within the main body or on the hinged door such that the second micro-switch is operated when the hinged door is in a closed position.

The third micro-switch <NUM> is a syringe detector that is configured to detect whether a syringe is fitted within the auto-injector. When a syringe is fitted within the auto-injector, the head <NUM> of the safety plunger <NUM> travels along the channel <NUM>, optionally actuating the first micro-switch <NUM> as it passes, and operates the third micro-switch <NUM> upon engagement of the barrel potion <NUM> with the plunger portion <NUM>. This results in a signal being transmitted to the processor <NUM>. In arrangements in which the main body <NUM> comprises a hinged door, the third micro-switch may be suitably positioned within the main body or on the hinged door such that the third micro-switch is operated when the syringe is inserted within the main body.

The plunger portion <NUM> also comprises a receiver <NUM> configured to receive a signal emitted from a device of the safety syringe. The signal may include data identifying one or more parameters related to the syringe or a substance contained therein. In exemplary arrangements, the receiver <NUM> may form part of an RFID reader that is configured to emit an electromagnetic signal that in turn causes an RFID tag on the syringe to emit the signal. The RFID reader <NUM> may then transmit the data to the processor <NUM>. The transmitter <NUM> may be configured to use a short range transmission protocol, such as Bluetooth (RTM).

The processor <NUM> may be configured to control a transmitter <NUM> to transmit dose data to a user device. The processor <NUM> may be further configured to time-stamp data.

Operation of the auto-injector is described below.

Prior to use of the auto-injector <NUM>, the barrel portion <NUM> is separated from the plunger portion <NUM>. As described above, the barrel portion <NUM> and plunger portion <NUM> are separated from each other by rotating the plunger portion <NUM> relative to the barrel portion <NUM>. This separation exposes an opening in the plunger portion <NUM> through which the syringe <NUM> may be inserted.

The syringe <NUM> is pushed into the barrel portion <NUM> until a click is heard which signifies that the sheath <NUM> is coupled to the carrier <NUM>. In the exemplary auto-injector <NUM>, insertion of the syringe <NUM> into the barrel portion <NUM> deforms the sheath coupling members 147a, 147b to allow the sheath <NUM> of the syringe <NUM> to pass through the carrier <NUM>. As the syringe <NUM> is pushed into the carrier <NUM>, the sheath coupling barbs 146a, 146b travel along the surface of the sheath <NUM> until they engage with a sheath recess. The engagement of the sheath coupling barbs 146a, 146b with the sheath recesses couples the carrier <NUM> to the sheath <NUM> and therefore to the syringe <NUM>.

The plunger portion <NUM> is then moved over the safety plunger <NUM> of the syringe <NUM> such that the safety plunger <NUM> is received inside the plunger portion <NUM>. The barrel portion <NUM> and the plunger portion <NUM> are connected together. The barrel portion <NUM> and the plunger portion <NUM> are connected by the user applying a linear force to snap or clip fit the barrel portion <NUM> and plunger portion <NUM> together. This may be done by the barrel thread riding over the plunger thread, as discussed above.

As the plunger portion <NUM> is engaged with the barrel portion <NUM>, the protrusion of the body <NUM> housed within the barrel portion <NUM> operates the second micro-switch <NUM>. This results in a signal being transmitted to the processor <NUM> indicating that the auto-injector is assembled. In addition, the head <NUM> of the safety plunger <NUM> operates the first micro-switch <NUM> in a direction towards the plunger end 100b of the auto-injector. This results in a signal being transmitted to the processor <NUM> indicating that a syringe is being fitted into the auto-injector. Upon complete assembly of the auto-injector, the third micro-switch is operated by the head <NUM> of the safety plunger <NUM>. This results in a signal being transmitted to the processor <NUM> indicating that a syringe <NUM> is fitted within the auto-injector.

In exemplary arrangements, the processor <NUM> determines that a syringe <NUM> has been correctly fitted within the auto-injector in dependence on the above sequence of events. In exemplary arrangements, all micro-switches must be operated in a specific order and optionally within specified time limits, for the processor <NUM> to determine that the syringe <NUM> has been correctly fitted.

In other exemplary arrangements, fewer micro-switches need to be operated for the processor <NUM> to determine that a syringe is correctly fitted within the auto-injector. In further arrangements not according to the invention, there is no requirement for the processor <NUM> to make such a determination at all. For example, in the broadest example, only the first micro-switch <NUM> is required and it is only required to be operated to determine that full dose has been delivered. In such arrangements, the processor <NUM> is not required to determine whether the syringe has been correctly fitted and only detects whether full dose delivery has occurred. In other arrangements, actuation of one or more of the micro-switches may be sufficient to determine that the syringe <NUM> is correctly fitted.

Returning to the exemplary arrangement described in detail herein, the processor <NUM> has determined that a syringe <NUM> is correctly fitted within the auto-injector. The RNS remover <NUM> is then disconnected from the barrel portion <NUM>. The RNS remover <NUM> is pulled outwards from the barrel portion <NUM> until an inwardly facing lip is disconnected from the corresponding recess on the barrel portion <NUM>. As the RNS remover <NUM> is coupled to the RNS <NUM> fitted to the syringe <NUM>, the RNS <NUM> is removed from the needle and falls through the RNS remover aperture <NUM>.

In some exemplary arrangements, disconnecting the RNS remover <NUM> from the barrel portion <NUM> exposes the depth adjustor <NUM>. Therefore, once the RNS remover <NUM> has been disconnected from the barrel portion <NUM>, the depth adjustor <NUM> is at maximum protrusion from the contact actuator <NUM> (and therefore the barrel portion <NUM>). At this point the lips 120a, 120b of the depth adjustor <NUM> are engaged with an upper surface of the contact actuator <NUM>. When the depth adjustor <NUM> is at a maximum protrusion from the contact actuator <NUM>, the depth adjustor <NUM> is rotatable with respect to the contact actuator <NUM>. The depth adjustor <NUM> may be rotated in order to align the protrusion <NUM> of the depth adjustor <NUM> with the desired castellation channel 124a-d.

In exemplary auto-injectors <NUM>, the depth adjustor <NUM> may be rotated before removal of the RNS remover <NUM> using a dial component <NUM> which may be received by the RNS remover <NUM>. The dial component <NUM> may be a separate component to the RNS remover <NUM> configured for insertion thereof or the dial component <NUM> may be part of the RNS remover <NUM>. In this arrangement, the depth adjustor may comprise teeth located on an internal surface thereof. The depth adjustor teeth may be configured to engage with corresponding teeth located on the dial component <NUM> when the RNS remover <NUM> is connected to the barrel. Rotation of the dial component <NUM> by the user causes a rotation of the depth adjustor <NUM> due to the engagement of the depth adjustor teeth with the corresponding teeth on the dial component <NUM>.

By allowing the depth adjustor <NUM> to be rotated, the depth of needle penetration within the injection site before actuation of the compression <NUM> is able to be set.

Once the protrusion <NUM> is aligned with the desired castellation channel 124a-d, longitudinal movement of the depth adjustor <NUM> within the contact actuator <NUM> causes the protrusion <NUM> to enter the castellation channel 124a-c with which it is aligned.

Once the protrusion <NUM> is aligned with the desired castellation channel 124a-c, the depth adjustor <NUM> may be pressed against the injection site such that the depth adjustor <NUM> is pushed inside the contact actuator <NUM>. This causes the protrusion <NUM> to travel within the selected castellation channel 124a-c. Pushing the depth adjustor <NUM> inside the contact actuator <NUM>, and therefore inside of the barrel portion <NUM>, exposes and pushes the needle of the syringe <NUM> into the injection site. The depth adjustor <NUM> continues to move within the contact actuator <NUM> and the needle continues to be pushed into the injection site until the protrusion <NUM> engages with the mechanical end stop surface of the castellation channel 124a-c. At this point, the depth adjustor <NUM> is unable to move within the contact actuator <NUM> any further and as such, the needle is unable to penetrate into the injection site any further. Selection of a particular castellation channel 124a-c therefore allows the user to customise the depth to which the needle penetrates into an injection site.

After the protrusion <NUM> meets the mechanical end stop, the contact actuator <NUM> is linearly coupled to the depth adjustor <NUM>. Therefore, once the protrusion <NUM> engages with the mechanical end stop surface 126a-d of the castellation channel 124a-c, further longitudinal movement of the depth adjustor <NUM> within the barrel portion <NUM> causes longitudinal movement of the contact actuator <NUM> within the barrel portion <NUM>.

As the contact actuator <NUM> moves rearwards within the barrel portion <NUM>, the lugs 132a, 132b on the arms 130a, 130b of the contact actuator <NUM> move along the angled surface of the locking members 140a, 140b. This deforms the locking members 140a, <NUM> and the locking barbs 146a, 146b are disengaged from the recess on the body <NUM>.

The disengagement of the locking barbs 146a, 146b from the recesses on the body <NUM> releases the carrier <NUM> holding the compression spring <NUM> in the primed state. The compression spring <NUM> therefore extends. One end of the compression spring <NUM> is in contact with the biasing surface <NUM> of the carrier <NUM>. As such, when the compression spring <NUM> extends, the carrier <NUM> is pushed towards the bottom of the barrel portion <NUM>.

Because the carrier <NUM> is connected to the sheath <NUM> of the syringe <NUM>, the sheath <NUM> is also pushed towards the needle end 100a of the auto-injector <NUM>. As the sheath <NUM> is connected to the plunger head <NUM> by the arms 212a, 212b, the plunger head <NUM> is driven down. As the syringe plunger <NUM> is coupled to the safety plunger <NUM>, the syringe plunger <NUM> is driven into the barrel <NUM> to inject a substance in the barrel <NUM> into the injection site.

As the safety plunger <NUM> and the syringe plunger <NUM> begin the delivery stroke, the third micro-switch <NUM> is released. A signal is transmitted to the processor <NUM> to indicate that the drug delivery process has begun. The processor then enters a delivery sequence and may then control visual and audio indicators to indicate this to a user. For example, the processor <NUM> may control an LED to flash and may control an audio output to emit a delivery tone. In exemplary arrangements, the processor <NUM> may be configured to enter the delivery sequence in dependence on a previous determination that the syringe <NUM> is correctly fitted within the auto-injector.

As the safety plunger <NUM> and syringe plunger <NUM> continue on the delivery stroke, the safety plunger <NUM> operates the first micro-switch <NUM> towards the needle end at a point at or just before the point of full dose delivery, i.e. the point at which the syringe plunger <NUM> reaches the end of the barrel <NUM>. In this way, the first micro-switch is able to detect movement of the syringe plunger <NUM> to a point indicative of full dose delivery. This results in a signal being transmitted to the processor <NUM> to indicate that full dose delivery has occurred. The first micro-switch <NUM> is operable to transmit the signal to the processor <NUM> in dependence on one or more of the operations/releases of the micro-switches discussed above. For example, the first micro-switch might only be operable if the first, second and/or third micro-switches <NUM>, <NUM>, <NUM> have previously been operated, and in the order discussed above.

The processor may be configured to remain in the delivery sequence for a period of time after actuation of the first micro-switch <NUM> to ensure that full dose delivery has occurred. The processor is then configured to control the transmitter <NUM> to transmit, to a user device, dose data indicating that full dose delivery has occurred.

In some exemplary arrangements, the processor <NUM> may be configured to enter a fail sequence if a threshold time is exceeded without the first micro-switch <NUM> being operated. The threshold time may be approximately <NUM> seconds. In this case, the processor <NUM> is configured to control the (or a different) LED to emit a different colour and/or flash cycle and may further control the audio output to emit a fail tone, which is different to the delivery tone. In one example, a red LED may be illuminated and may remain illuminated until the auto-injector is disassembled. The processor <NUM> may be configured to control the transmitter <NUM> to transmit, to the user device, dose data indicating that the delivery has failed.

The auto-injector <NUM> may be configured such that the extension of the compression spring <NUM> to drive the syringe plunger <NUM> within the barrel <NUM> continues until the bottom surface <NUM> of the carrier <NUM> is in contact with the injection site. Once the carrier <NUM> is in contact with the injection site, the compression spring <NUM> is prevented from extending any further. The auto-injector <NUM> may be configured such that the carrier <NUM> makes contact with the injection site once the syringe plunger <NUM> reaches the bottom of the barrel <NUM> and all of the substance within the barrel <NUM> has been expelled.

The extension of the compression spring <NUM> to drive the syringe plunger <NUM> to the bottom of the barrel <NUM> takes a period of time, and the user must wait for this. In exemplary auto-injectors <NUM>, the user must wait for approximately <NUM> seconds.

The user may then move the auto-injector away from the injection site. This allows for continued extension of the compression spring <NUM>. The continued extension of the compression spring <NUM> moves the carrier <NUM> and therefore the sheath <NUM> (which is coupled to the carrier <NUM>) of the syringe <NUM> over the needle. The extension of the compression spring <NUM> continues until the sheath <NUM> fully covers the needle and the carrier <NUM> partially protrudes from a needle end opening of the barrel portion <NUM>.

After use, the plunger portion <NUM> of the auto-injector <NUM> may be removed from the barrel portion <NUM>. The barrel portion <NUM> is rotated relative to the plunger portion <NUM> to disengage the barrel thread <NUM> and the plunger thread <NUM>. The rotation of the plunger portion <NUM>, rotates the syringe <NUM> within the barrel portion <NUM>. This frees the syringe <NUM> from the carrier <NUM> by disengaging the sheath coupling barbs 146b, 146c from the recesses located on the sheath <NUM> of the syringe <NUM>. This may be done using the cam surface <NUM> or by deformation of the sheath coupling members 140a, 140b, as discussed above.

Once the sheath coupling barbs 146b, 146c are disengaged from the sheath <NUM>, the syringe <NUM> and the carrier <NUM> are decoupled and the syringe <NUM> may be moved independently of the carrier <NUM>.

The syringe <NUM> may then be removed from the barrel portion <NUM>. The sheath <NUM> of the syringe <NUM> is extended over the needle and this prevents stick injuries.

The compression spring <NUM> may then be primed again for future use of the auto-injector <NUM>. Once the auto-injector <NUM> has been moved away from the injection site following use of the auto-injector <NUM> at the injection site and the syringe <NUM> has been removed from the auto-injector <NUM>, the compression spring <NUM> is in an extended state, and the contact actuator <NUM> and carrier <NUM> protrude from the barrel portion <NUM>. To prime the compression spring <NUM>, the RNS remover <NUM> is pushed back into the barrel portion <NUM>.

The RNS remover <NUM> is pushed into the barrel portion <NUM>. This causes the prongs 118a, 118b of the RNS remover <NUM> to engage with the bottom surface <NUM> of the carrier <NUM> and push the carrier towards the top of the barrel portion <NUM>. The contact actuator <NUM> is prevented from being pushed back into the barrel portion <NUM> along with the carrier <NUM> by the engagement of lock-out protrusions with the opening of the barrel portion <NUM>.

The lock-out protrusions are configured to prevent the contact actuator <NUM> from being pushed back into the barrel portion <NUM> until the locking barbs 146a, 146b of the carrier <NUM> engage with the corresponding recesses on the body <NUM> of the auto-injector to lock the compression spring <NUM> into the primed position.

Once the compression spring <NUM> has been locked into the primed position, further movement of the RNS remover <NUM> within the barrel portion <NUM> pushes the lock-out protrusions inwards.

The lock-out protrusions may be pushed inwards by ramps located on an internal surface of the RNS remover <NUM>. The ramps may be located at a distance from the bottom of the RNS remover <NUM> such that they do not interact with the lock-out protrusions until the RNS remover <NUM> has been pushed within the barrel portion <NUM> a distance to engage the locking barbs 146a, 146b with the corresponding recesses on the body <NUM>.

Once the lock-out protrusions have been pushed inwards, further movement of the RNS remover <NUM> within the barrel portion <NUM> pushes the contact actuator <NUM> back into the barrel portion <NUM> until the RNS remover <NUM> is reconnected to the barrel portion <NUM>.

In some exemplary arrangements, the processor <NUM> may be configured to control the RFID reader <NUM> to interrogate an RFID tag or similar device located on the syringe <NUM>. For example, on determination that the syringe <NUM> has been correctly fitted within the auto-injector, the processor <NUM> may instruct the RFID reader <NUM> to interrogate the RFID tag. The RFID tag may then emit a signal comprising syringe data relating to one or more parameters of the syringe, such as a date that the syringe was filled with a drug, the batch of drug used, the type and identification of the drug etc. The RFID tag then receives the syringe data and transmits it to the processor <NUM>. The processor is configured to include the syringe data in the dose data to be transmitted to the user device.

In some exemplary arrangements, the processor <NUM> may be configured to transmit the syringe data to the user device without the dose data. For example, exemplary auto-injectors may include an RFID reader <NUM> without including the first, second and/or third micro-switches <NUM>, <NUM>, <NUM>. In such cases the syringe data may be transmitted to the user device in isolation.

In exemplary methods and apparatus, the processor <NUM> is configured to timestamp dose data. This may be done in circumstances when the transmitter <NUM> is not able to transmit the dose data to the user device. The processor <NUM> may store the dose data in a memory until such time as a connection to the user device may be established. For example, the processor <NUM> may wait until the transmitter <NUM> is able to pair to the user device. The user device is then able to determine the actual time that the dose data was recorded.

As shown in <FIG>, a syringe <NUM>, such as any syringe described herein, may comprise a device <NUM> configured to emit a signal to the receiver <NUM> of the auto-injector. The device <NUM> may in some examples be an RFID tag. The RFID tag may be fitted to the plunger head <NUM> such that it is positioned in close proximity to the RFID reader <NUM> when the syringe <NUM> is fitted within the auto-injector. In other arrangements, the RFID tag <NUM> may be fitted to another part of the syringe <NUM> such that it is aligned with and/or within transmission range of the RFID reader <NUM> when the syringe <NUM> is fitted within the auto-injector. The RFID tag <NUM> may be programmed with data relating to one or more parameters of the syringe <NUM> and/or the contents of the syringe <NUM>, as discussed above.

It is noted that although the above described methods and apparatus include use of a safety syringe, this need not be the case. Exemplary methods and apparatus can be used with a syringe, and in particular arrangements a syringe allowing the plunger driver to be placed below the head of the plunger of the syringe. For example, the methods and apparatus disclosed may comprise a plunger driver configured to couple to the head of the plunger of the syringe from below. This may comprise a direct coupling to the plunger head or an indirect coupling to the plunger head, such as by one or more arms extending from the plunger head towards a needle end of the apparatus.

Claim 1:
An auto-injector (<NUM>) for use with a safety syringe (<NUM>), the auto-injector comprising:
a main body (<NUM>) that is openable for receiving the safety syringe (<NUM>) and closable before operation of the auto-injector (<NUM>), the main body comprising a barrel portion (<NUM>) configured to receive a barrel of the safety syringe and a plunger portion (<NUM>) configured to receive a plunger of the safety syringe, wherein the barrel portion (<NUM>) and the plunger portion (<NUM>) are configured for detachable engagement, and wherein the main body (<NUM>) is in the open position when the plunger portion and the barrel portion are detached;
characterised by
a first detector (<NUM>) configured, after activation of the auto-injector (<NUM>), to detect a plunger of the safety syringe (<NUM>) at a point on a delivery stroke thereof that is indicative of full dose
delivery of a substance from the safety syringe (<NUM>)
a second detector (<NUM>) configured to detect that the auto-injector (<NUM>) is assembled by detecting engagement of the barrel portion and the plunger portion;
a third detector (<NUM>) configured to detect a presence of the safety syringe (<NUM>);
a processor configured to receive an electrical signal from the first detector indicative of operation of the first detector;
wherein, the first detector (<NUM>) is configured to be only operable to transmit a signal to said processor in dependence of at least one of the second detector (<NUM>) having detected that the auto-injector (<NUM>) is assembled and the third detector (<NUM>) having detected the presence of the safety syringe (<NUM>).