Abstract:
A medication delivery system, comprising: a movable part ( 230, 232 ) adapted to move relative to a stationary part; at least two conductors ( 234, 236 ) which are arranged such that an electrical characteristic is defined by the mutual position of the movable and the stationary part and/or by movement of one of said parts relative to the other; and a detector for detecting a change of said electrical characteristic, wherein the parts are stationary relative to each other during dose setting and in that the parts are moved relative to each other during dose ejection, such that that detector provides a signal indicative of the actual amount of the ejected dose.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a medication delivery system comprising a detector for detecting relative rotational movement and/or position of a movable part and a stationary part. 
       BACKGROUND OF THE INVENTION 
       [0002]    In medication management, compliance i.e. the degree to which a patient follows medical instructions and protocols, is often of extreme importance. In relation to injection of medicaments, one key aspect of determining the compliance is determination of the actual dose of the medication injected. Accordingly, it is desirable to provide medication delivery systems with dose quantity identification systems. 
         [0003]    One such system is known from WO 02/092153, which discloses a medication injector apparatus, which encompasses a doseable quantity identifier for an injector pen vvhich uses a sensor to read a matrix to determine how a dose setting mechanism has been rotationally arranged by a user in setting the pen for dose administration. The apparatus further comprises an assembly for selectively rotating a drive sleeve, which assembly has a dial that rotates out during dose setting and which translates without rotation during dose injecting. 
         [0004]    Further dose quantity identification systems may be seen in WO 03/103753, WO 2004/030717, WO 90/09202, WO 03/009461 and WO 02/064196. 
         [0005]    It is an object of a preferred embodiment of the present invention to provide a medication delivery system, which rather than outputting the dose which is assumed to be ejected, outputs the dose which in fact was ejected. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a medication delivery system, comprising:
       a movable part adapted to move relative to a stationary part;   at least two conductors which are arranged such that an electrical characteristic is defined by the mutual position of the movable and the stationary part and/or by movement of one of said parts relative to the other; and   a detector for detecting a change of said electrical characteristic,
 
wherein
 
the parts are stationary relative to each other during dose setting and in that the parts are moved relative to each other during dose ejection, such that that detector provides a signal indicative of the actual amount of the ejected dose.
       
 
         [0010]    One advantage of the present invention is that the system identifies the actual amount of the ejected dose, as it does not assume that the ejected dose is identical to the set dose. Thus, any difference between the set dose and the ejected dose will not influence the determination of compliance. Such difference between the set dose and the ejected dose could e.g. occur if the ejection process be halted during dose ejection. 
         [0011]    The medication delivery system may be a syringe device comprising an integrated reservoir for accommodation of a medicament. In other embodiments the reservoir is removable and thus a new reservoir may be inserted into the device when a used reservoir is empty. The system may form a pen e.g. for insulin. 
         [0012]    The movable part may be movable by translation or by rotation. The stationary part may co-axially encapsulate the movable part e.g. such that both co-extend in an axial direction of the device and such that the movable part is provided inside the stationary part. A housing of the syringe device may define the stationary part. In other embodiments the stationary part is attached to the housing of the device. 
         [0013]    The movable part may be connected to a piston rod of the device, the piston rod being employed for advancing a piston for forcing drug out of a drug-containing compartment of the system. Translational movement of the piston rod may cause a part of the medicament of be ejected from the syringe device. The piston rod may have a threaded outer surface and a part of the device may be adapted to receive the piston rod as it has a corresponding threaded inner surface. In the latter embodiment rotational movement of the piston rod may also result in a translational movement of the piston rod. 
         [0014]    In one embodiment the movable part and the stationary part is able to rotate more then one revolution i.e. more than 360 degrees, during setting of the dose or during ejection. In such embodiments the medical device may comprise a counter which is able to count the number of revolutions performed. 
         [0015]    In the device there is provided at least two conductors between which the detector may be provided. Alternatively, the detector may be connected to the electrical conductors of the device. As an example a resistance between the conductors changes depending on the relative position of the movable part and the stationary part and thus the detector may be a device adapted to detect resistance between two elements. 
         [0016]    In embodiments wherein the movable part is adapted to rotate relative to the stationary part during ejection of a set dose of a medicament, the detector may be used to determine the ejected dose such that the user may keep a log of the ejection history and the ejection times. 
         [0017]    In embodiments wherein the movable part is adapted to rotate relative to the stationary part during setting of a dose, there may be provided a sensor which is able to determine when an ejection starts and/or when it is finished. Thus, the ejected dose may be calculated using information about the set dose at the time of starting the ejection and the remaining dose when finishing the ejection. In the latter embodiment detector may be a detector capable of determining translational movement e.g. of the piston rod, but not necessarily the length of the traveled distance. 
         [0018]    In case the movable part is movable by translation, such as linear translation, the movable part may e.g. constitute a portion of the piston rod, or it may constitute a part which is integral with the piston rod. 
         [0019]    The electrical characteristic may be one of an electrical inductance, a capacitance, an electric resistance, a voltage and an electrical current. The electrical inductance may e.g. be impedance or capacitance. In the latter case the electrical conductors may be connected to surfaces of conductive material which are spaced apart from each other. The relative position of the two surfaces determines the capacitance. In one embodiment the surfaces are provided as two half circles which may be rotated between two positions a first position wherein they overlap each other entirely and a second position wherein the do not overlap at all. In an alternative to the latter embodiment one of the surfaces rnoves translationally while rotating, whereby the distance between the surfaces changes. Thus, when the movable part has rotated one revolution the capacity between the plates has changed as the distance between the plates has changes. Thus, it is possible to determine both the relative angular position of the surfaces and the number of revolutions which have been performed. 
         [0020]    In yet another embodiment a coil may be provided between the tvvo conductors. The coil may be provided on stationary part. At the same time a magnetic material may be provided on the movable part and thus movement of the movable part induces a current between the two conductors. In the latter embodiment the relative movement of the stationary part and the movable part may be determined. 
         [0021]    From the above it may be appreciated that the electrical characteristic between the two conductors may depend on relative position and or on relative movement of the movable part and the stationary part. 
         [0022]    The movable part may comprise a first electrically conducting surface, and the stationary part may comprise a second electrically conducting surface, the electrical characteristic of the at least two electrical conductors being determined by relative movement and/or relative position of said first and second surfaces. In one embodiment there is provided two conductors a first which is electrically connected to the first electrically conducting surface and a second conductor which is electrically connected to the second electrically conducting surface. 
         [0023]    A primary set of contact surfaces may be arranged to engage and disengage upon relative movement of the stationary part and the movable part, the primary set of contact surfaces may comprise a first and a second contact surface which comprises the first and the second electrical surfaces, respectively. 
         [0024]    In a preferred embodiment the first conductor is connected to the first conducting surface which is provided on the first contact surface and the second conductor is connected to the second conducting surface which is provided on the second contact surface. 
         [0025]    In one embodiment a secondary set of contact surfaces may be arranged to engage and disengage upon relative movement of the stationary part and the rnovable part, the secondary set of contact surfaces may comprise a third and a fourth contact surface which may comprise a third and a fourth electrical surface, respectively. Furthermore, the electrical characteristic between the primary set of contact surfaces may be unchanged when the electrical characteristic between the secondary set of contact surfaces is changed and vice versa. Thus, at no time two or more electrical characteristic are changed at the same time. 
         [0026]    In one embodiment the rotatable part comprises both the first and the third electrically conducting surfaces which are provided on the same contact surfaces. 
         [0027]    Biasing arms may be provided which are biased towards the periphery of the movable part, said arms comprising at least one of the second and the fourth conducting surfaces. In one embodiment there is provided two biasing arms one defining the second conducting surface and one defining the fourth conducting surface. 
         [0028]    The outer periphery of the movable part may define a plurality of conductive and non-conductive surfaces which may define the first and the third contact surfaces. 
         [0029]    A visible and/or audible and/or tactile indication may detectable when the second or the fourth contact surface changes from a conductive to a non-conductive surface. Accordingly, the system changes status electronically, the user may be able to identify a change e.g. as he hears or feels a ‘click’. 
         [0030]    The periphery of the movable part, may comprise abrupt changes in the radial dimension. Such abrupt changes may be used to ensure that the movable part is only able of rotating in one direction. The changes may also be used to provide a tactile or audible indication which may be generated by rotating the movable part such that an biased arm changes position from a point with a large radial dimension to a point with a small radial dimension, where by a ‘click’ may be generated. 
         [0031]    The contact surfaces may arranged to lock for relative rotational movement in one direction. The lock may be provided by the abrupt change in the radial dimension. 
         [0032]    A processor may be provided to collect the information detected from the detector. Such a processor may be an electronic processor comprising a memory. In one embodiment the arrangement comprises a power supply and an ASIC connected to the at least two conductors. The ASIC may be adapted to collect the information from the detector and to transform the information into a format known to the user. As an example the collected information is in one embodiment degrees of rotation of the movable part relative to the stationary part. In the embodiment rotation of a piston rod results in rotation of the movable part and as the outer surface of the piston rod is threaded, rotation of the piston rod results in a translational movement of the piston rod such that volume of the medicament is ejected. Accordingly, the ASIC of said embodiment may transform the degrees of rotation into a distance in the axial direction which again may be transformed into the volume of the medicament which is ejected. 
     
    
     
       DETAILED DESCRIPTION OF THE INVENTION 
         [0033]    The invention will now be described in further detail with reference to the drawings, in which: 
           [0034]      FIG. 1  is a schematic cross-sectional illustration of a medication delivery pen and a cover therefor; 
           [0035]      FIG. 2  is a schematic illustration of electronic components of an embodiment of a medication delivery pen; 
           [0036]      FIG. 3  is a schematic illustration of electronic components of an embodiment of a cover for a medication delivery pen; 
           [0037]      FIGS. 4-15  illustrate various parts of a sensor arrangement for detecting a quantity of a dose of drug ejected from an embodiment of medication delivery pen, the movable part of which is rotational; 
           [0038]      FIGS. 16-18  illustrate embodiments, the movable part of which is movable by translation; 
           [0039]      FIG. 19  illustrates a control system of the various embodiments of medication delivery pens. 
       
    
    
       [0040]    The pen  100  in  FIG. 1  includes a drug cartridge or container  150 , in which a piston  152  is arranged, so that it may slide in a distal direction (to the right in  FIG. 1 ) under the action of a piston rod  154 . The cartridge is secured in relation to the remaining parts of the pen by a cartridge holder  151 . The piston rod  154  has a threaded outer surface which is guided in a ratchet  156 . When drug ejection is activated by an operator, the ratchet and/or piston rod is influenced to cause the piston rod to move the piston  152  in the distal direction to force the drug out of the cartridge  150  through a needle (not shown) which extends through septum  158 . Evidently, the cover  108  is removed prior to ejection of the dose. The pen further includes a nut  160  with an integrated sensor arrangement for detecting the size of an ejected dose, the sensor arrangement being further described below in connection with  FIGS. 3-12 . Electrical switches  162  provide an interface to external devices, such as to a cradle for transmitting information to an external device, such as a personal computer, or to a pen cover  108  which includes corresponding switches  164 . The cover  108  may include a battery (not shown) for powering its display portion  110 . The battery may conveniently be comprised in the distal end portion of the cover. A rotational dose setting member  104  may be used to set a dose, the set dose being e.g. indicated in a window  105 . In general, the rotational movement of the piston rod  154  during ejection of the drug may be achieved as described in U.S. Pat. No. 6,235,004 which is hereby incorporated by reference. 
         [0041]      FIG. 2  is a schematic illustration of electronic components of an embodiment of a medication delivery pen. There is provided an “On switch” for allowing the battery to deliver power to an ASIC processor and to a memory connected to the ASIC processor. The processor is further connected an I/O device for communicating data via the switches  162  (cf.  FIG. 1 ), and to one or more sensors, e.g. a sensor arrangement for detecting ejection information. In operation, the sensors may detect the quantity of an ejected dose which is communicated to the ASIC processor. The processor stores the quantity and the time of the ejection in the memory. Once the pen  100  is placed in the cradle  114  or once the cover  108  is placed over the needle portion of the pen, the ASIC processor initiates transfer of the information stored in the memory or a part of that information via the I/O device. The I/O device may also be used to clear the memory, such clearing being e.g. caused by an operator of the personal computer  112 . The electronic components incorporated in the pen cover or cap  108  are illustrated in  FIG. 3 . A chrystal (X-tal) serves as a clock generator for the microcontroller, which is powered by a battery, and which communicates with the electronic components of the pen via the external communication (data input) and with the display as illustrated. 
         [0042]    The nut  160  may for example constitute a part of the sensor arrangement of  FIG. 4 . The sensor arrangement comprises a first conductor in the form of a movable part  200  arranged to rotate in the direction of arrow  201  in relation to one or more second conductors in the form of stationary parts, e.g. arms  202  and  204 , which are biased toward a peripheral edge  206  of the movable part  200 . The hatched sections of the periphery  206  are non-conductive surface portions, whereas the non-hatched sections are conductive surface portions, i.e. first and third contact surfaces. Those end portions of the arms  202  and  204  which engage the periphery  206  define second and fourth contact surfaces. It will thus be appreciated that one of the arms via its engagement with the peripheral surface portion  206  defines a primary set of contact surfaces, while the other one of the arms via its engagement with the peripheral surface portion  206  defines a secondary set of contact surfaces. A conductive element  208  is provided for applying a voltage to the movable part  200 . As illustrated, the periphery  206  defines abrupt changes of its radial dimension. These abrupt changes are also abrupt changes between conductive and non-conductive surface portions. Accordingly, as the movable part  200  is rotated relative to the arms  202  and  204 , each of the arms will be charged in an alternating manner in accordance with its engagement with a conductive, i.e. charged, surface portion, or with a non-conductive, i.e. non-charged, surface portion. The changes in the two arms&#39; respective charges can be recorded or detected, so that each voltage change in either one of the arms indicates a rotational increment of the movable part. This increment may indicate an incremental increase or decrease of a set dose, and/or an incremental increase of an ejected dose. Thanks to the abrupt changes in radial dimension of the movable part  200  and corresponding abrupt changes in surface conductivity, there is provided a mechanical coupling between the changes of the electrical characteristic and the rotation of the movable part. Accordingly, it is ensured that no increment is erroneously recorded without the movable part having actually been rotated. 
         [0043]      FIG. 5  illustrates a different embodiment of a movable part  210  for determining an ejected and/or set dose. The peripheral surface of the part  210  comprises three sections  212 ,  214  and  216 , each of which defines a plurality of abrupt changes of radial dimension and conductivity according to the same general principle as described above in connection with  FIG. 4 . The abrupt changes of each of the three sections are arranged with mutual angular displacements in order to decrease the detectable increments of a set or ejected dose portion which. 
         [0044]    The sensor assembly  220  depicted in  FIG. 6  includes the movable part  200  of  FIG. 4  or the movable part  210  of  FIG. 5  integrated with a support member  222  for mounting the sensor assembly in a housing of a medication delivery pen. The support member  222  also supports a battery  224  and a processor  226 , such as an ASIC processor. 
         [0045]    The embodiment of  FIGS. 7-10  comprises two identical discs  230  and  232  arranged one above the other with a mutual angular displacement as illustrated in the far right drawing of  FIG. 7 . A core member  234  is arranged centrally within the discs, the core member carrying a ratchet arm  236  for engagement with one or the other disc. The discs are charged differently and arranged in electrical isolation from one another, so that the ratchet arm will produce a voltage output which varies as the ratchet arm  236  makes contact with one or the other disc  230 ,  232 , cf. the illustrative view in the lower drawing of  FIG. 8 . As shown in  FIGS. 9 and 10 , there may be provided two arms  236 . The core member may, cf.  FIG. 9 , extend out of the plane of the discs, so that rotation thereof may be effected by rotation of e.g. a dose setting member and/or a dose ejecting means (not shown in  FIG. 9 ) connected to or integrated with the core member  234 . 
         [0046]      FIG. 11  shows a yet further embodiment of a movable part  240  which comprises three rows of protrusions  242  along its periphery. For example, the peripheral surfaces of the protrusions may be conductive, whereas the remaining peripheral surface of the movable part  240  may be non-conductive. The part  240  forms part of a sensor arrangement which also comprises an electronic circuit board as illustrated in  FIG. 12 , which comprises three arms  244  for engaging and disengaging the protrusions  242  to detect rotation of the movable part  240 . 
         [0047]    The sensor arrangement of  FIG. 13  is similar to the arrangement of  FIGS. 7 and 8  and comprises two discs at different voltages which are electrically insulated from one another. A core member  254  with a ratchet arm  256  makes alternating contact with one or the other disc to result in an alternating voltage output indicative of an increment or decrease of a set or an ejected dose of drug. 
         [0048]    In the above embodiments, the electrical characteristic is described as a voltage. It should, however, be understood that the characteristic may also be any other detectable electrical property, such as a frequency of an alternating current. 
         [0049]      FIG. 14  illustrates an inductive sensor, in which a movable part is provided in the form of an anchor  260  to inductors  262 ,  264 . Induction can be measured or detected by an oscillating circuit, in which frequency changes are determined, or in which the rise time of the current in the inductor can be measured. 
         [0050]    The embodiment of  FIG. 15  also relies on an inductive principle, in which piston rod  154  is guided in a nut  161 , the piston rod being enclosed by a conductive member  157 , an end flange  159  of which is arranged in the vicinity of a coil. 
         [0051]      FIGS. 16-18  illustrate embodiments, the movable part of which is movable by translation. 
         [0052]    In  FIGS. 16-18 , the characteristic may, as previously discussed, also be any other detectable electrical property, such as a frequency of an alternating current. To the extent that alike parts are included in the embodiment of  FIGS. 16-18  as in the embodiment of  FIGS. 1-15 , the same reference numerals are used. Piston rod  270  has a barbed surface engaging a ratchet  272 , the ratchet serving to lock the piston rod against translational movement in the proximal direction and/or as a contact for detecting advancement of the piston rod  154  in the distal or proximal direction. In  FIG. 17 , the piston rod  274  comprises dark and light portions which reflect and absorb light to a different extent, so that an adequate light sensor  276  may provide a signal when the piston rod is advanced in one direction or the other. The ratchet  272  serves to lock the piston rod against translational movement in the proximal direction. In  FIG. 18 , the engagement of the piston rod  278  and the ratchet  272  causes the ratchet to touch a contact element when the tip of the ratchet  272  passes a peak on the barbed surface of the piston rod  278 . Thereby, an electrical pulse is generated each time the piston rod is advanced a distance corresponding to the distance between two successive barbs. 
         [0053]    In general, the translational movement of the piston rod  270 ,  274 ,  278  during ejection of the drug may be achieved as described in German document DE 68901190, which is hereby incorporated by reference. 
         [0054]    The control system of any of the sensor arrangements outlined above is diagrammatically illustrated in  FIG. 19 , in which the sensor itself outputs signals A and B and optionally further signals depending on the number of ratchet arms or other measurement members provided. The signals are passed to an electronic circuit comprising: sensor control and monitor, timer, counter, memory, display control and external communication means. The electronic circuit is arranged to communicate with a display of a medication delivery pen and/or with an external device.