Pen-type injector having an electronic control unit

An injection device for injection of a dose of a medicament from a medicament cartridge is disclosed. The injection device of the present invention comprises a main housing 4 having an electronic control unit, a cover detection switch 28, and a display panel 10 operative selectively to indicate to the user information relevant to the user. The display panel 10 has an active state in which information is provided to the user and an inactive state in which no information is provided. A cap or cover 6 adapted to cover one end of the main housing 4 of the injection device is provided. When the presence of the cap 6 is detected, the electronic control unit switches the display panel 10 to an active state for a predetermined period of time.

The present invention relates to improvements in an injection device, and in particular to improvements in a portable injection device for dispensing controlled quantities of a medicament.

Typically such injection devices are used by those suffering from diabetes to administer a dose of insulin or insulin-type medicine to themselves. It will be understood that such injection devices are suitable for the injection of other medicines.

At one time, such doses were administered by use of a disposable syringe; the syringe first being filled from a separate phial or other container and then used to inject the dose. However, there were a number of difficulties in such an arrangement. In particular, such an arrangement was not suitable for the infirm. For others, the social stigma associated with such syringes made their public use problematic.

To overcome these difficulties a number of so-called pen-type injectors have been developed. These devices are small, being capable of being carried in a jacket pocket or the like and allow a number of doses to be obtained from a cartridge or ampoule contained within the injector. The present invention has particular application to such pen-type injectors.

While such pen-type injectors are a considerable improvement upon disposable hypodermic syringes, problems nevertheless remain. It is an advantage of the present invention that it eliminates, or at least substantially reduces such problems. The present invention also provides for improved ease of use and improved interaction with a user.

Referring first toFIGS. 1 to 3, there can be seen a pen-type injector2in accordance with the present invention. The injector2comprises a main housing4to which is releasably secured an end cap or cover6.

At a first end of the main housing4there is provided a control panel region8. This region includes a display panel10, typically a LCD display, and a first dose button12and a second dose button14, the first and second dose buttons being operated to increase or decrease a dose of medicament to be delivered. The control panel region10in the illustrated embodiment also includes an arm button16.

At the first end of the main housing there is also provided a dispense button18. Preferably, when not depressed, the dispense button18is flush with the main housing4.

Along a longitudinal axis of the injector2, to each side of the control panel region10are provided a number of grooves or recesses20. These aid in the gripping of the injector2by a user.

At a second end of the main housing4a needle unit22is releasably secured to the main housing. The second end of the main housing4is also provided with a shaped portion24.

In use a cartridge40or ampoule of medicament is stored in the housing4behind the shaped portion24. For preference, the shaped portion is transparent to permit the cartridge40to be seen by a user.

A primer button26is also provided on the second end of the housing4. It will be understood that when the end cap6is in place over the second end of the housing, it will not be possible inadvertently to depress the primer button26or to be pricked by the needle unit22. A cover detection switch28may also be included at the second end of the main housing4to detect whether the end cap or cover6is in place or not.

InFIG. 3, there can be seen a priming contact30, an arm contact32, a first dose contact34and a second dose contact36corresponding to the respective buttons. A dispense contact19corresponding to the dispense button18is also shown.

With reference toFIG. 3it may be seen that there is provided a suitable location for a power source38such as a battery or batteries. There is also a suitable region in which a cartridge40or ampoule of medicament is to be located. This region may be accessed by way of the removable shaped portion24of the main housing4to allow for replacement of the cartridge40or ampoule as required by the user.

In a third region of the main housing4there is provided a drive mechanism42which operates from the power source38and acts upon the cartridge40or ampoule of medicament.

The cartridge40or ampoule comprises a container44or sleeve closed at one end by a cover46at a head end thereof, and sealed at the other by a movable bung48or stopper. When in position, the needle unit22pierces the cover46and movement of the bung48towards the cover46will cause the medicament contained within the cartridge40or ampoule to be expelled. The cartridge may be a 3 ml cartridge in accordance with ISO/FDIS 11608 Part 3, or any other suitable cartridge to suit the injector.

Movement of the bung48or stopper is caused by movement of a piston or plunger50forming a part of the drive mechanism42. The piston or plunger50is movable between a first fully withdrawn position (not shown) which allows for the replacement of the cartridge40or ampoule and a second fully extended portion in which as much medicament as possible has been expelled from the cartridge40or ampoule. An end stop switch52may be provided in the main housing4to detect when the piston50is in the fully withdrawn position. Tripping of the switch end stop52may release a catch or other fastening device to allow access to the main housing4for replacement of the cartridge40.

The drive mechanism42is operated by a motor54under the control of an electronic control unit (not shown). The motor54should be reversible in order to allow the piston50to be moved between the first and second positions. InFIG. 3, the motor54can be seen to drive the piston50by way of a gear train42, such that rotation of a third rotor58causes the piston50to be moved in relation to the third rotor58.

Preferably, the user can feel the vibration of the motor54and the associated drive mechanism42and/or hear them in operation. In this way an added degree of confidence in the fact of the operation of the injector2is provided to the user.

The functionality of a pen-type injector in accordance with the present invention will now be described, in particular with reference toFIGS. 1,2and3.

The injector2is provided with an electronic control unit. The electronic control unit is coupled both to the drive mechanism and a user interface. The user interface includes the display panel10as well as the user operable buttons (and associated contacts). The electronic control unit is microprocessor based. Either volatile or non-volatile memory may be used for storage of ‘dose history’ and patient specific information.

The electronic control unit is preferably powered from the injector power source38.

The injector2preferably also includes a port for communication between the electronic control unit and an external apparatus such as a personal computer.

The injector2also has a priming detection facility, (such as a tilt switch or accelerometer) to identify when the injector2is inverted. On detection of an inverted position (needle up) the injector2will automatically change state to be ready for priming. Priming may be initiated by depression of the primer button26to cause a fixed small dispense action. The electronic control unit may cause a speaker to sound when the primer button26is depressed.

The primer button26is inactive at all other times. When the primer button26is active, all other buttons in the control panel region are inactive, that is those buttons which are to be used to set or dispense a dose.

The electronic control unit may cause a speaker to sound when the arm button16is depressed for a sufficient period of time to provide audible feedback for the user.

The function of the arm button16is to make the dose button18active. The arm button is preferably held down for a predetermined period of time before the injector2becomes armed. The armed status may additionally be shown on the display panel10. The functionality of the arm button is preferably linked to the cover detection switch28such that the arm button16will only function to arm the injector2when the cover6is not present.

Additionally, in a preferred embodiment, a clock within the electronic control unit will detect whether the dose button18has been pressed within a specified time interval following arming of the injector2. If the dose button18has not been depressed within the specified time interval the electronic control unit will disarm the injector2. Alternatively, if the arm button is depressed a second time within a predetermined time period by the user, the injector will be disabled.

In an alternative embodiment, the dose button18may function as both a prime button and the dose button. When the priming detector is actuated, by the injector2being oriented needle up, the dose button18would change function to that of the prime button of the previous embodiment.

The buttons of the injector2are preferably tactile in nature to provide sensory feedback to the user.

The display panel10is typically an LCD display and will provide alphanumeric and graphical information relating to the operation of the device. The display panel10preferably indicates the selected dose quantity, the previous dose quantity and the time elapsed since the previous dose was administered. Typically, the time elapsed since the previous dose is limited to a time period within the preceding 48 hours, though other time periods are possible.

Additional information which may be displayed includes:that the injector is armed and ready to dispense (graphical)that the injector is dispensing (graphical)that the injector has dispensed the selected dose and that a user should wait before removing the needle from their bodythat this waiting period has elapsedthe dose history, typically for the last 48 hours, in terms of the dosage taken and the elapsed time between dosesthe quantity of medicament remaining in the cartridge, preferably in terms of dosage units of the medicament.that the device is in the priming position (either in addition to or instead of the acoustic indication noted above)the speaker volume setting, for example high, low or muted.that the injector is nearing the end of its life (for example a battery power level indication—graphical or countdown in terms of the number of days or complete operating cycles to a predetermined expiry of the product life—alphanumeric).that the needle is probably blockedthat replacement of the cartridge40is in progressthat the dose selected is the maximum available in the cartridge40that the maximum dose available is less than the dose expected.

The display panel10may offer a user a choice of language options as appropriate for the market and/or user. The text displayed may include that noted above and/or further information. The language option may be pre-programmed or selectable by a user. The user may preferably select the language option by means of a menu provided on the display panel10.

The currently selected dose value, the previously used dose value and the time (in hours) since the previous dose was dispensed, may all be shown clearly at the same time, in large, easy-to-read characters on the display. Preferably, the display is also provided with a backlight.

The display10preferably provides a graphical indication that the selected dose is being dispensed. This may be achieved, for example, as either an animated graphic or a countdown (or a combination of both).

The control buttons have a number of functions. The dose buttons12,14allow a user to select a desired dosage. The dose arm button16allows a user to confirm selection of a desired dosage. The first dose button can increment the dosage level and the second dose S button can decrement the dosage level. The dose dialling buttons12,14may be pressed down (and held for a short time, 1-2 seconds) to re-set a dose value to zero. The user can then dial up (or down) in single (or half) increments.

The dose dialling buttons12,14are intended to be pressed once for a single (or half) increment in the selected dose value. In an alternative embodiment, pressing and holding one of the buttons will cause the dose value to start to scroll (up or down) in order to change the dose size more rapidly.

The dispense button18allows a user to initiate dispensing of the dosage. The primer button26dispenses a unit of dosage from the cartridge40. Thus, if any air is trapped in the injector2this can be expelled by use of the primer button26. A door release catch is provided to allow access to the cartridge40.

The injector2may also be provided with an audible alarm, such as a piezo-electric sounder or an electronically-operated sounder. The device may have a switch or means of setting the volume level of the sounder and/or to turn it off. This may be used to provide an acoustic confirmation of depression of one or more of the buttons, as an alarm indicator to warn the user that there is a limited quantity of medicament in the cartridge40, as an alarm indicator to warn a user that the injector is nearing the end of its life (battery drainage indicator), to indicate that the desired dosage has been delivered and that a predetermined time has elapsed since completion of a dispense operation and a user is now free to withdraw the needle and/or other conditions as may be required. The acoustic signal may be provided in addition to a visual signal provided on the display panel10and in addition to any feedback provided by the tactile nature of the buttons.

Since the cartridge40is of a standard size, each cartridge40will be emptied by an identical travel of the plunger driven by the drive mechanism. Once the plunger50is in the fully extended position, the cartridge40is known to be empty and an indication of this will be provided to the user.

When the door release catch is operated for the emptied cartridge40to be removed the drive mechanism42is operated to reverse a lead screw60to withdraw the plunger50until the lead screw60strikes the end stop switch52which is provided at a known reference point.

When a new cartridge40is detected, for example by way of a contact switch (not shown), and the door release catch closed, the electronic control unit advances the lead screw60until the plunger50strikes the cartridge bung48. This may conveniently be done by fitting a micro-switch51, such as a dome contact switch to a free end of the plunger50.

Since the exact position of the bung48can be calculated with reference to the rear end stop52, a number of units of medicament stored within the cartridge40can be determined. Thus a half empty or incorrectly filled cartridge40may be used with the injector2of the present invention. The electronic control unit having determined the number of units stored within the cartridge preferably will not allow a dosage larger than that remaining to be dialled up for dispense.

The electronic control unit preferably stores a preferred dosage. The preferred dosage may correspond to the previous dosage administered, or may be a dosage preset by way of a data port as part of a regimen of the medicament to be taken as directed or prescribed by a doctor, general practitioner or nurse. This has as an advantage that a user can dial up or down as required from the preferred dosage. This is more convenient than dialling up from a zero value.

The electronic control unit is preferably provided with means to enable the display panel10to power down. With the cover6in place, detectable by the electronic control unit by way of a cover detection switch28, the electronic control unit may activate the display panel10, upon depression of one of the buttons, to show for a limited period, say 4 seconds, selected information regarding the use of the injector2. The selected information may include one or more of the quantity of the previous dose, the time elapsed since the previous dose and/or the amount of medicament remaining in the cartridge40.

Preferably the drive system will allow for part units of a medicament to be dispensed (for example a half unit). The electronic control unit can then function in either a full unit mode or part unit mode. A switch (or a combined depression of existing switches) may be actuated to move between modes.

The maximum size (quantity of medicament) of any particular dispense is not limited by the drive system. Two characters on the display will provide a limit of 99 units. However, if three characters are displayed it is quite feasible to select and dispense up to the capacity of a full cartridge—300 units.

The product life is preferably limited to a pre-determined time span or total number of units of medicament dispensed, whichever occurs first. The device will monitor the rate of use of the medicament and, by calculation and using the pre-determined number of units for product life, will be able to predict when the end of product life is due. In this way, the device can display and countdown to end of the product life.