Drug delivery devices allowing for multiple dosing of a required dosage of a liquid medicinal product, such as liquid drugs, and further providing administration of the liquid to a patient, are as such well-known in the art. Generally, such devices have substantially the same purpose as that of an ordinary syringe.
Pen-type injectors of this kind have to meet a number of user specific requirements. For instance in case of those with diabetes, many users will be physically infirm and may also have impaired vision. Therefore, these devices need to be robust in construction, yet easy to use, both in terms of the manipulation of the parts and understanding by a user of its operation. Further, the dose setting must be easy and unambiguous and where the device is to be disposable rather than reusable, the device should be inexpensive to manufacture and easy to dispose. In order to meet these requirements, the number of parts and steps required to assemble the device and an overall number of material types the device is made from have to be kept to a minimum.
Since such drug delivery devices are to be used in a home environment and in particular by way of self-medication, the user or patient has to become accustomed to the handling of the device prior to self-administering a dose of the medicament.
Particularly for the purpose of training or testing a device and its properties, there exist various training cartridges or syringes to be operably coupled with a drive mechanism of a drug delivery device. When appropriately coupled with the drive mechanism, the training cartridge should provide a realistic feedback to the user on how the drug delivery device and its mechanical components behave during dose setting and dose dispensing procedures.
In a rather simple approach, training cartridges are filled with water or a placebo featuring comparable mechanical properties than the genuine medicinal product originally contained in the cartridge.
Even though such water- or placebo-filled cartridges may provide realistic mechanical feedback of the cartridge itself and for the drug device's drive mechanism and since these known cartridges also mimic the visible behaviour of the cartridge, such dummy cartridges might be accidentally confused with genuine cartridges filled with a medicinal product. Consequently, the patient may inject water or placebo instead of the prescribed drug and may thus be treated with an incorrect amount of the medicament.
Furthermore, when making use of water- or placebo-filled cartridges, any of such training or dummy cartridges must be sterile filled or terminally sterilized in case the contents are injected. This also means that the training or dummy cartridge can only be used by a single user in order to prevent any potential cross-contamination of the cartridge, which may happen if a cartridge would be used by several users. Moreover, such water- or placebo-filled cartridges have to be used up within a given shelf life or within their given in-use life.
Cartridges being filled with either a placebo or with a medicament, the effect can be observed, that the displaceable piston is to be pushed or pulled in axial direction with push- or dragging forces of different magnitude. For instance, pushing the piston in distal direction for expelling the liquid content of the cartridge requires a pressure being substantially greater than a force required for returning and pulling the piston back into its initial position. When designing a training cartridge without a liquid content, also this non-symmetric actuating force should be simulated in a realistic way.
It is therefore an object of the present invention to provide a training cartridge to be used with a drug delivery device requiring different actuating forces for different modes of operation. Hence, the training or test cartridge should be able to simulate the overall behaviour of a genuine cartridge to a large extend. Preferably, the training cartridge should not require filling with water or a placebo. Moreover, it is intended to provide a reset function for the training cartridge allowing to make use of said cartridge multiple times.