Abstract:
The present invention relates to a medical device comprising a base member ( 2 ), a container ( 20 ) comprising a container interior ( 28 ) adapted to accommodate a substance, and a container closure ( 23 ) for fluidly sealing the container interior, and fluid connection means ( 50 ) for establishing fluid connection to the container interior. A cover ( 4 ) removably mountable on a cover receiving portion ( 36 ) is operatively coupled with the fluid connection means ( 50 ) to cause a relative motion between the fluid connection means ( 50 ) and the container closure ( 23 ) in response to a relative motion between the cover ( 4 ) and the base member ( 2 ). The medical device further comprises a cover engagement mechanism ( 9, 37, 46, 49 ) configured to prevent movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the base member are in a first relative position in which the fluid connection means ( 50 ) and the container interior ( 28 ) are fluidly separated and to allow movement of the cover ( 4 ) in a dismounting direction relative to the cover receiving portion ( 36 ) when the cover and the base member are in a second relative position in which the fluid connection means and the container interior are fluidly connected.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to fluid transfer devices, particularly to medical mixing devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    Within drug delivery it may be of vital importance to maintain sterility of a product to be administered from its production to its administration. Many drug substances are therefore supplied in sealed containers having penetrable access means, such as rubber septa, which are adapted to be pierced by a suitable tool, e.g. a hollow needle. 
         [0003]    For example, people with IDDM frequently attach an injection needle to their insulin pen to thereby penetrate a self-sealing rubber septum of an insulin containing cartridge and establish a delivery line for subcutaneous administration. The needle and the insulin are stored in respective sterile environments until the point of connection. 
         [0004]    Some pharmaceutical drugs adapted for parenteral administration are only stable in the administrable form a relatively short period of time. For convenience reasons, and in order to extend the shelf life of such a drug, it is sometimes preferred to store individual constituents of the drug separately and to mix them only just before a dose is needed. 
         [0005]    Traditionally, a mixing of two substances stored in separate vials is performed using a syringe with a needle to withdraw the substance from the one vial and inject it into the other vial. The syringe with the attached needle is then used to withdraw from this vial the desired amount of drug to be injected into the patient. This kind of manual operation may be difficult and may bring about some uncertainty as to the exact concentration of the resulting drug, because it can be difficult to completely empty a vial by such an approach. Moreover, since the first substance is withdrawn from one vial and transported to another vial via a syringe with a needle, typically including a penetration of two rubber septa in order to establish fluid connection to the respective vial interiors, both sterility and safety may be compromised. To reduce the risk of contamination of the administrable substance it is customary to clean the respective rubber septa with an alcohol swab before needle penetration. This, however, is often considered a hassle by the user, especially if she/he needs to mix the substances and administer the resulting drug quickly to avert a serious situation. 
         [0006]    U.S. Pat. No. 5,466,220 (Bioject, Inc.) discloses different examples of drug vial mixing and transfer devices comprising one or two vials and a syringe pre-aligned and packaged in sealed sterile packages to eliminate the need for swabbing the vials before piercing and to avoid sharp needle exposures. While overcoming some of the drawbacks of the traditional way of mixing substances, the solutions comprising two vials appear bulky and operationally cumbersome, and the solutions including a single vial introduce a risk of carrying out the individual operational steps in a wrong order, because the syringe plunger is operable before connection of the vial and the syringe, thereby enabling a delivery of some of the syringe contents to the exterior of the vial. 
         [0007]    WO 97/46203 (Applied Research Systems ARS Holding N.V.) discloses a pre-assembled pack for a drug reconstituting device, which pack comprises a vial co-axially aligned with a cartridge and separated therefrom by a double-ended needle element. In the pre-use state of the device the needle element is shielded at each end by a slidable bung, providing for closed, sterile needle chambers. Like the above mentioned prior art solutions including a single vial, this pack also lacks a mechanism which prevents it from being manipulated erroneously to e.g. expel the contents of the cartridge before fluid connection to the vial has been established. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the invention to provide a solution which eliminates, or at least reduces, drawbacks of the prior art. 
         [0009]    In particular, it is an object of the invention to provide a medical device which is simple to operate and which offers an automatic sequence control guaranteeing a correct sequence of at least some key operations of the device. 
         [0010]    It is a further object of the invention to provide a fluid transfer device offering safe and sterile establishment of fluid connection to a substance container. 
         [0011]    It is an even further object of the invention to provide a medical mixing device comprising a user operable actuation mechanism which cannot be operated until fluid communication is properly established between respective substance containing reservoirs. 
         [0012]    In the disclosure of the present invention, aspects and embodiments will be described which will address one or more of the above objects and/or which will address objects apparent from the below disclosure as well as from the description of exemplary embodiments. 
         [0013]    In a first aspect of the invention a medical device is provided comprising a base member, a first container comprising a first container interior adapted to accommodate a first substance, and a first container closure for fluidly sealing the first container interior, and a second container comprising a second container interior adapted to accommodate a second substance, and a second container closure for fluidly sealing the second container interior. The medical device further comprises fluid connection means for establishing fluid communication between the first container interior and the second container interior, and fluid transfer means for causing transfer of the first substance to the second container interior. A cover is removably mounted on a cover receiving portion to shield at least a portion of the fluid transfer means and is operatively coupled with the fluid connection means to cause a relative motion between the fluid connection means and at least one of the first container closure and the second container closure in response to a relative motion between the cover and the base member. An incorporated cover engagement mechanism is configured to prevent movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the base member are in a first relative position, in which the first container interior and the second container interior are fluidly unconnected, and to allow movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the base member are in a second relative position in which fluid communication is established between the first container interior and the second container interior. 
         [0014]    Such a construction enables the provision of a medical device capable of transferring a substance from one container to another, which device may be operated by a user to execute the transfer only after removal of a protective cover and proper establishment of fluid communication between the respective container interiors. Thereby, it is ensured that a premature fluid transfer cannot take place and, consequently, that no substance wastage can occur. This is particularly relevant when a specific volumetric ratio of the first substance and the second substance is needed to produce a predictable medical treatment outcome. It is further relevant in order to avoid leakage within the device potentially causing damage to the internal components as well as giving rise to a perception of the product being unreliable. The construction further provides a medical mixing device which offers separate storage of the individual substances to be mixed and simple, easy and safe establishment of a fluid pathway between the substances, requiring a minimum number of manual operational steps. 
         [0015]    In the present context, “movement of the cover in a dismounting direction relative to the cover receiving portion” means a movement of the cover in a direction that will eventually lead to a dismounting from the cover receiving portion. Such movement may include a translation, e.g. along an axis defined by the cover receiving portion, a rotation, e.g. about an axis defined by the cover receiving portion, or a spiraling movement of the cover relative to the cover receiving portion. 
         [0016]    The first container may be a fixed volume reservoir or a variable volume reservoir capable of selective decrease and/or increase of an internal volume. A suitable variable volume reservoir may e.g. comprise a user operable actuator operatively coupled with a movable wall, one example of such a reservoir being a syringe which comprises a movable piston adapted for actuation by a user operable piston rod. In that case the cover may be adapted to shield the actuator when mounted on the cover receiving portion. Similarly, the second container may have a fixed or variable internal volume. 
         [0017]    In particular embodiments the first container and the second container are co-axially arranged along a general axis, and the fluid connection means is arranged at least partially between the first container and the second container. Thereby, an attractive slender configuration of the medical device may be provided which makes it suitable for being carried about in e.g. a pocket or a handbag. 
         [0018]    The fluid connection means may comprise a central portion carrying one or more pointed hollow shaft members, such as one or more needles or spikes. In particular, the central portion may carry either a single needle/spike or two oppositely pointing, fluidly connected, needles/spikes. The central portion may be encircled by a cylindrical sleeve extending substantially parallel to the one or more hollow shaft members. 
         [0019]    The fluid transfer means may comprise an initial pressure difference between the first container interior and the second container interior or, alternatively, an actuation mechanism for selectively establishing a pressure difference between the two container interiors. The actuation mechanism may e.g. be adapted to selectively create an excess pressure in the first container or a negative pressure in the second container for transferring the first substance from the first container to the second container. The actuation mechanism may further be adapted to selectively create an excess pressure in the second container or a negative pressure in the first container for transferring a mixture of the first substance and the second substance from the second container to the first container. 
         [0020]    The actuation mechanism may be arranged in connection with either the first container or the second container, such as e.g. in the form of a piston rod in a syringe, or it may be arranged separately from the two containers. 
         [0021]    The base member may e.g. comprise a holder, protector and/or a support for one of the containers. For example, in case the container is of the fixed volume reservoir type, such as e.g. a vial, the base member may be a protective cover for the reservoir. In case the container is of the variable volume reservoir type, such as e.g. a cartridge, the base member may be a reservoir holder. Alternatively, or additionally, the base member may be a housing or a part of a housing for internal components of the medical device, or it may simply be a component with respect to which the container is translationally or rotationally fixed. 
         [0022]    The operative coupling between the cover and the fluid connection means may comprise a mechanical coupling between the cover and one of the first container and the second container and a mechanical coupling between the container in question and the fluid connection means. Specifically, the cover may mechanically interface, e.g. by engagement or abutment, a portion of the first container which is immovable relative to a first container outlet. Thereby, it is ensured that the pressure in the first container interior remains fixed when the first container is moved, regardless of which type of container is employed. 
         [0023]    The mechanical interaction between the cover and the first container may be realised via coupling means, such as protrusions, on the inner surface of the cover structured to interface with a radially outwardly extending flange portion on or associated with the first container to enable joint motion of the cover and the first container in a first direction. 
         [0024]    In some embodiments, the cover and the first container are coupled to enable joint translational motion of the two in a first direction along the general axis. 
         [0025]    The relative motion between the cover and the base member that induces a relative motion between the fluid connection means and at least one of the first container closure and the second container closure may be purely translational, purely rotational or helical. In some embodiments the relative motion between the cover and the base member comprises a converging translational relative motion. 
         [0026]    The cover engagement mechanism may comprise a releasable interlocking of the cover and the cover receiving portion, e.g. realised via a position dependable interaction between respective portions of the cover, the cover receiving portion, and a wall extending along the general axis. 
         [0027]    The cover receiving portion may form part of a first container support member, e.g. a first container holder, and the wall may form part of a second container support member, e.g. a second container holder. Such a construction may minimise the number of different components required for the cover engagement mechanism and may thereby reduce the manufacturing costs and the complexity of the medical device. The wall may alternatively, or additionally, form part of a sleeve member which is structured to accommodate at least a portion of the fluid connection means and to allow axial movement of the fluid connection means in its interior. Such a construction may enable a non-bulky design of the medical device. 
         [0028]    The cover engagement mechanism may specifically comprise a radially deflectable portion of the cover receiving portion arranged in releasable engagement with the cover. This radially deflectable portion of the cover receiving portion may be biased radially outwardly relative to the general axis but configured to deflect inwardly when subjected to a radially inwards directed force. The radially deflectable portion may comprise an inclined surface for interaction with an inclined surface, e.g. an inclined inner surface or opening, of the cover to generate a radial force component for action on the radially deflectable portion when an axial pull force is applied to the cover. 
         [0029]    The cover engagement mechanism may be structured such that radial inwards deflection of the radially deflectable portion is prevented when the cover and the base member are in the first relative position or between the first relative position and the second relative position and allowed when the cover and the base member are in the second relative position. This may e.g. be accomplished by initially arranging the cover, the cover receiving portion and the wall such that the radially deflectable portion is wedged between the cover and the wall until the cover and the base member are brought to the second relative position. The wall may be provided with an axially extending opening arranged to allow projection therethrough of the radially deflectable portion when the cover and the base member are in the second relative position. 
         [0030]    To establish proper fluid communication between the first container interior and the second container interior a relative translational motion of magnitude x 1  between the first container closure and the fluid connection means and a relative translational motion of magnitude x 2  between the second container closure and the fluid connection means are required. The cover engagement mechanism is designed to enable a release of the cover only when the cover and the base member have undergone relative motion to effectively cause a relative translational motion of magnitude x 1  between the first container closure and the fluid connection means and a relative translational motion of magnitude x 2  between the second container closure and the fluid connection. Thereby, it is ensured that the cover cannot be dismounted from the cover receiving portion when e.g. fluid connection has been established to only one of the containers. In particular embodiments, the cover engagement mechanism is designed to enable a release of the cover only when the cover and the base member have undergone a relative converging translational motion of at least a magnitude x r =x 1 +x 2 . 
         [0031]    A portion, e.g. a tip portion, of the radially deflectable portion may be adapted for sliding abutment with the wall during movement of the cover and the base member from the first relative position to the second relative position. 
         [0032]    In some embodiments the first container is a variable volume reservoir, e.g. a syringe, releasably fixed to a reservoir holder such that upon transfer of the first substance from the first container to the second container and subsequent transfer of a mixture of the first substance and the second substance from the second container to the first container, the first container may be removed from the reservoir holder and used with suitable delivery means, such as a cannula or an infusion set, for application of the mixed product to a desired site of administration. 
         [0033]    The medical device may further comprise a blocking element movable with respect to the base member from a first position in which relative motion between the cover and the base member from the first relative position to the second relative position is prevented to a second position in which relative motion between the cover and the base member from the first relative position to the second relative position is allowed. The first position may be a first translational or rotational position of the blocking element relative to the base member and the second position may be a second translational or rotational position of the blocking element relative to the base member. For example, in the second position the blocking element may be completely removed from the medical device. 
         [0034]    The blocking element may, when positioned in the first position, prevent axially converging relative motion between the cover and the base member, in which case the blocking element may act as a spacer element separating the cover from the base member. 
         [0035]    The blocking element may comprise a radially inwardly extending flange for supporting the fluid connection means in a pre-use state of the medical device. This will assist in defining and maintaining a correct pre-use positioning of the fluid connection means relative to the respective container closures, thereby ensuring that none of the container closures are prematurely penetrated. The blocking element may further comprise a dedicated interface for user operation to enable an easy switch from the first position to the second position. The dedicated interface may e.g. comprise a pull ring for tearing away the blocking element. 
         [0036]    In a second aspect of the invention a medical device is provided comprising a base member, a container comprising a container interior adapted to accommodate a substance, and a container closure for fluidly sealing the container interior, and fluid connection means for establishing fluid connection to the container interior. A cover removably mountable on a cover receiving portion is operatively coupled with the fluid connection means to cause a relative motion between the fluid connection means and the container closure in response to a relative motion between the cover and the base member. The medical device further comprises a cover engagement mechanism configured to prevent movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the base member are in a first relative position in which the fluid connection means and the container interior are fluidly separated and to allow movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the base member are in a second relative position in which the fluid connection means and the container interior are fluidly connected. 
         [0037]    The fluid connection means may e.g. comprise a hollow needle or spike element having either one or two pointed end portions. 
         [0038]    In some embodiments, the medical device is a fluid transfer device comprising a) a vial comprising a substance in a vial interior and a fluid tight vial seal, b) a vial holder to which the vial is firmly attached, c) fluid connection means capable of undergoing relative motion with respect to the vial seal from a first position in which the fluid connection means and the vial interior are fluidly unconnected to a second position in which the fluid connection means and the vial interior are fluidly connected, d) a cover for shielding at least a portion of the fluid connection means, the cover being operatively coupled with the fluid connection means to cause a relative motion between the fluid connection means and the vial seal in response to a relative motion between the cover and the vial holder, e) a cover receiving portion structured for engagement or abutment with the cover when the cover is mounted to shield the at least a portion of the fluid connection means, and f) a cover engagement mechanism structured to prevent movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the vial holder are in a first relative position and to allow movement of the cover in a dismounting direction relative to the cover receiving portion when the cover and the vial holder are in a second relative position. The fluid connection means comprises a hollow shaft capable of entering the vial interior and attachment means fluidly connected to the hollow shaft, the attachment means being structured to receive an outlet portion of a variable volume reservoir. 
         [0039]    In a third aspect of the invention a drug delivery device is provided comprising a) a variable volume drug reservoir, e.g. a cartridge, capable of holding a drug substance in a reservoir interior sealed by a penetrable septum, b) a support member configured to encircle at least a portion of the reservoir, c) an actuator mechanism for altering the volume of the reservoir interior, the actuator mechanism being arranged at least partially in a housing, d) a needle assembly comprising a needle hub carrying a double-pointed needle cannula and attachment means for attaching the needle hub to the reservoir or the support member, e) a removable cap adapted to cover at least a portion of the reservoir, the cap being operatively coupled with the needle assembly to cause a relative motion between the needle assembly and the penetrable septum in response to a relative motion between the cap and the reservoir, f) a cap receiving portion structured for engagement or abutment with the cap when the cap is mounted to cover the at least a portion of the reservoir, and g) a cap engagement mechanism configured to prevent movement of the cap in a dismounting direction relative to the cover receiving portion when the cap and the reservoir are in a first relative position, in which the needle cannula and the reservoir interior are fluidly separated, and to allow movement of the cap in a dismounting direction relative to the cap receiving portion when the cap and the reservoir are in a second relative position in which the needle cannula and the reservoir interior are fluidly connected. 
         [0040]    The drug delivery device may further comprise a blocking element, or spacer element, which must be removed to allow relative converging motion of the cover and the housing. The blocking element may thus serve both as a safety against unintended penetration of the reservoir septum by the needle cannula and as a tamper indicator. 
         [0041]    In the present specification, reference to a certain aspect or a certain embodiment (e.g. “an aspect”, “a first aspect”, “one embodiment”, “an exemplary embodiment”, or the like) signifies that a particular feature, structure, or characteristic described in connection with the respective aspect or embodiment is included in, or inherent of, at least that one aspect or embodiment of the invention, but not necessarily in/of all aspects or embodiments of the invention. It is emphasized, however, that any combination of features, structures and/or characteristics described in relation to the invention is encompassed by the invention unless expressly stated herein or clearly contradicted by context. 
         [0042]    The use of any and all examples, or exemplary language (e.g., such as, etc.), in the text is intended to merely illuminate the invention and does not pose a limitation on the scope of the same, unless otherwise claimed. Further, no language or wording in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    In the following the invention will be further described with references to the drawings, wherein 
           [0044]      FIG. 1  shows an exploded view of a medical device according to an embodiment of the invention, 
           [0045]      FIG. 2  shows a longitudinal section view of the device of  FIG. 1 , in a pre-use state, 
           [0046]      FIG. 3  shows a close-up longitudinal section view of the device, in an initial use state, detailing the cover engagement mechanism and the fluid connection means, 
           [0047]      FIGS. 4   a  and  4   b  show close-up longitudinal section views of the device in different use states, 
           [0048]      FIG. 5  shows a close-up longitudinal section view of the device after fluid communication has been established between the container interiors, and 
           [0049]      FIG. 6  shows a close-up longitudinal section view of the device after removal of the outer cover. 
       
    
    
       [0050]    In the figures like structures are mainly identified by like reference numerals. 
       DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0051]    When in the following relative expressions, such as “upwards” and “downwards”, are used, these refer to the appended figures and not necessarily to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as their relative dimensions are intended to serve illustrative purposes only. 
         [0052]      FIG. 1  is an exploded perspective view of a mixing device  1  for reconstitution of a powdered drug in a vial  20  using a solvent from a syringe  10 . The vial  20  comprises a wall  21  having an opening which is sealed by a vial stopper  23  (see  FIG. 2 ) and a seal cap  22 . A tower  25  protrudes axially from the seal cap  22  in the direction away from the vial  20 . The tower  25  has an inner circumferential sealing rim  26  at its end portion, the purpose of which is explained below. 
         [0053]    The vial  20  is arranged in a vial protector  2  which serves to protect the vial  20 . In the disclosed embodiment the wall  21  is made of glass and the vial protector  2  is made of plastic. Other suitable materials may, however, be chosen, depending on the specific application of the mixing arrangement  1 . 
         [0054]    The proximal portion of the vial protector  2  has an enlarged diameter to accommodate a distal portion of a sleeve member  40 . The sleeve member  40  comprises an axially extending wall  46  and an opening  49  in the wall  46 , the opening  49  being arranged to allow release of a cap  4  from the mixing device  1  in a manner which is described in detail below. In this particular embodiment the sleeve member  40  is arranged non-translationally relative to the vial protector  2 . 
         [0055]    The sleeve member  40  is designed to accommodate a connector piece  50  and to interact with a distal portion of a syringe holder  30 . The syringe holder  30  comprises a proximal supporting frame  35  adapted to receive and hold a portion of the syringe  10  and a distal cap receiving portion  36  in the form of a tubular segment provided with a number of circumferentially spaced apart flexible arms  37  as well as a number of openings  39 . In the transition between the supporting frame  35  and the cap receiving portion  36  a number of lock snaps  38  are circumferentially distributed. The lock snaps  38  are adapted to fix a stopper fastener  70  to the syringe holder  30  by interaction with a pair of protrusions  72 . The stopper fastener  70  holds a syringe stopper  60  in place so as to sealingly close an outlet of the syringe  10 . The syringe  10  is of the Luer-Lok type having a threaded Luer collar  13  at the distal end of a barrel  11 . A filter  69  is optionally arranged in the syringe stopper  60  to filter out any impurities of a passing liquid. The proximal end portion of the barrel  11  is shaped to provide a circumferential collar  17  having a slightly greater outer diameter than the barrel  11  itself. A piston rod  14  extends from the interior of the barrel  11  and has a proximal push face  15  for operation by a user. The cap  4 , which is non-deformable in ordinary use conditions and which is adapted to fit over the syringe  10  and be received by the cap receiving portion  36 , is provided with a number of circumferentially spaced apart openings  9  at its distal end portion. 
         [0056]      FIG. 1  also shows a spacer element  90  adapted for initial pre-use arrangement between the cap  4  and the vial protector  2  to ensure that an axial spacing between the two is maintained. The spacer element  90  is a bendable, or segmented, band which can be removed by performing a peeling action. 
         [0057]      FIG. 2  is a longitudinal section view of the mixing device  1  in the assembled state, prior to a first use thereof, showing further details of the arrangement. This state corresponds to the one in which the mixing device  1  is intended to be delivered by the manufacturer. The piston rod  14  is in a retracted position in the barrel  11 , thereby defining a syringe interior  18  capable of holding a certain volume of a solvent (not shown). The piston rod  14  is coupled firmly to a piston  19  via a jagged coupling head  16 . The cap  4  is fitted snugly around the collar  17 , providing a user friendly slender configuration of the mixing device  1 . 
         [0058]    A Luer  12 , defining the outlet of the syringe  10 , protrudes into the hollow interior of the cap receiving portion  36  and is retained therein via a screw thread connection between the Luer collar  13  and a threaded inner portion  71  of the stopper fastener  70 . A portion of the syringe stopper  60  is wedged between the Luer  12  and the threaded inner portion  71  and thereby provides a fluid tight engagement with the exterior surface of the Luer  12 . The syringe stopper  60  has a penetrable section  61  (see  FIG. 3 ) allowing for easy rupturing of the syringe sealing by a suitable tool. 
         [0059]    The connector piece  50  is slidably received in the hollow interior of the sleeve member  40  and is axially supported by an interior flange  93  on the spacer element  90 , the flange  93  defining an exact initial position of the connector piece  50  relative to the penetrable section  61  and a penetrable section  24  (see  FIG. 3 ) of the vial stopper  23 . The sleeve member  40  has a number of circumferentially spaced apart catch arms  45  extending downwards from a transversal interior portion for securing firm attachment of the vial  20 . The wall  21  defines a vial interior  28  capable of holding an amount of powdered drug (not shown) to be reconstituted by the solvent from the syringe  10 . The wall  21  is flexibly supported by leaf springs  8  in the bottom of the vial protector  2  to account for manufacturing tolerances. 
         [0060]    In  FIG. 2  the cap  4  is mounted on the cap receiving portion  36  whereby the entire syringe  10  is shielded from the surroundings. A number of ribs  6  extend axially along an inner portion of the cap  4 , each of the ribs  6  having a distally oriented contact face  7  adapted for interaction with the collar  17 . The respective flexible arms  37  are biased such that they flex into the respective openings  9  in the cap  4 . Each flexible arm  37  is provided with an inclined surface which interacts with an inclined surface of the corresponding opening  9  such that an axial proximally directed force applied to the cap  4  will result in a radially inwards directed force on the flexible arms  37 . In this pre-use state of the mixing device  1  the flexible arms  37  abut the sleeve member  40  and are prevented from inwards deflection by the wall  46 . Thereby, the cap  4  is prevented from being dismounted from the cap receiving portion  36 . It is noted that in the shown embodiment the openings  9  are cut-outs in the cap  4 . This, however, need not be the case, as the cap  4  could alternatively be provided with e.g. grooves in inner wall portions. To start using the mixing device  1  the user must first remove the spacer element  90  by pulling a pull ring  92  tangentially. 
         [0061]      FIG. 3  is a close-up longitudinal section view of a central portion of the mixing device  1  in a pre-connection state where the spacer element  90  has just been removed. In this state the distal end face of the cap  4  and the proximal end face of the vial protector  2  are axially spaced apart a distance, L 1 . The figure details the connector piece  50  and its initial arrangement with respect to the syringe  10  and the vial  20 . The connector piece  50  comprises a cylindrical sleeve body  51  with radially outwardly projecting flanges  58  at each end, serving to stabilise the connector piece  50  in the interior of the sleeve member  40 . The sleeve body  51  supports a transverse spike base  54  which carries a distally pointing hollow spike member  52  as well as a proximally pointing hollow spike member  53 . In the depicted state of the mixing device  1  the hollow spike member  53  is arranged just distally of the penetrable section  61  of the syringe stopper  60  and the hollow spike member  52  is arranged just proximally of the penetrable section  24  of the vial stopper  23 . The syringe  10  and the vial  20  are therefore fluidly unconnected at this point. The syringe stopper  60  has at its distal end portion a circumferential sealing lip  62  which is adapted to sealingly engage with an interior portion of the sleeve body  51  to provide a fluid tight compartment  56  for the hollow spike member  53 . Similarly, the tower  25  with the sealing rim  26  provides a fluid tight compartment  57  for the hollow spike member  52 . This particular construction thus enables the incorporation of a sterilised sub-assembly comprising the syringe stopper  60 , the connector piece  50  and the vial stopper  23  during assembly of the mixing device  1 , and further ensures that sterility of the respective hollow spike members  52 ,  53  is maintained throughout storage, transportation and use of the mixing device  1  with no need for additional sterile barriers. 
         [0062]    In order to enable removal of the cap  4  from the cap receiving portion  36  the cap  4  initially needs to be pressed towards the vial protector  2 . The needed relative converging motion of the cap  4  and the vial protector  2  will cause relative converging motion between the syringe stopper  60  and the connector piece  50  as well as between the connector piece  50  and the vial stopper  23 , as will be clear from the below. The exact sequence of motion of the syringe stopper  60  relative to the connector piece  50  and of the connector piece  50  relative to the vial stopper  23  depends on the frictional characteristics of the internal components of the mixing device  1  and the specific arrangement of these components. The sequence may be known, as dimensioned by the manufacturer, or arbitrary.  FIGS. 4   a  and  4   b  illustrate the two extremes where complete converging relative motion between the syringe stopper  60  and the connector piece  50  takes place before any relative motion is induced between the connector piece  50  and the vial stopper  23  ( FIG. 4   a ) and where complete converging relative motion between the connector piece  50  and the vial stopper  23  takes place before any relative motion is induced between the syringe stopper  60  and the connector piece  50  ( FIG. 4   b ). 
         [0063]      FIG. 4   a  is a close-up longitudinal section view of the same portion of the mixing device  1  as was depicted in  FIG. 3 . However, in  FIG. 4   a  the cap  4  has been pressed downwards towards the vial protector  2 , slaving the syringe  10  via the interaction between the contact faces  7  and the collar  17 . The syringe  10  has been accompanied by the syringe holder  30  due to the above described fixed relationship between the Luer collar  13 , the stopper fastener  70  and the syringe holder  30 . Since the sleeve member  40  is unable to move axially with respect to the vial protector  2  the downward movement of the syringe holder  30  has caused the flexible arms  37  to slide axially along the wall  46 . The axial distance between the distal end face of the cap  4  and the proximal end face of the vial protector  2  is now L 2 , i.e. the cap  4 , and thereby the flexible arms  37 , has travelled the distance x 1 =L 1 −L 2  towards the vial protector  2 . 
         [0064]    In the illustrated situation the converging relative motion between the cap  4  and the vial protector  2  has caused the syringe stopper  60  to travel the same axial distance towards the spike base  54 , whereby the spike member  53  has penetrated the penetrable section  61  and entered an interior space  68  between the penetrable section  61  and the Luer  12 . During the travel of the syringe stopper  60  the circumferential sealing lip  62  has slid along the inner wall of the sleeve body  51 . To avoid a resulting pressure build up in the compartment  56  one or more vents  59  are provided in the sleeve body  51 , allowing gas, e.g. air, entrapped therewithin to escape. As can be seen no fluid communication between the syringe interior  18  and the vial interior  28  has yet been established and the flexible arms  37  still abut the sleeve member  40 , which means that the cap  4  is still retained on the cap receiving portion  36 . 
         [0065]    Further movement of the cap  4  and the syringe  30  towards the vial protector  2  will cause relative motion between the connector piece  50  and the vial stopper  23 , whereby the penetrable section  24  will be penetrated by the spike member  52 . 
         [0066]      FIG. 4   b  is a close-up longitudinal section view of the same portion of the mixing device  1  as was depicted in  FIG. 3 . However, just as in  FIG. 4   a , the cap  4  has been pressed downwards towards the vial protector  2 , slaving the syringe  10  via the interaction between the contact faces  7  and the collar  17 . The syringe  10  has been accompanied by the syringe holder  30  due to the fixed relationship between the Luer collar  13 , the stopper fastener  70  and the syringe holder  30 . Again, since the sleeve member  40  is unable to move axially with respect to the vial protector  2  the downward movement of the syringe holder  30  has caused the flexible arms  37  to slide axially along the wall  46 . The axial distance between the distal end face of the cap  4  and the proximal end face of the vial protector  2  is in this situation L 3 , i.e. the cap  4 , and thereby the flexible arms  37 , has travelled the distance x 2 =L 1 −L 3  towards the vial protector  2 . 
         [0067]    In the illustrated situation the converging relative motion between the cap  4  and the vial protector  2  has caused the connector piece  50  to travel the same axial distance towards the vial stopper  23 , whereby the spike member  52  has penetrated the penetrable section  24  and entered the vial  20 . As can be seen no fluid communication between the syringe interior  18  and the vial interior  28  has yet been established and the flexible arms  37  still abut the sleeve member  40 , which means that the cap  4  is still retained on the cap receiving portion  36 . 
         [0068]    Further movement of the cap  4  and the syringe  30  towards the vial protector  2  will cause relative motion between the syringe stopper  60  and the connector piece  50 , whereby the penetrable section  61  will be penetrated by the spike member  53 . 
         [0069]      FIG. 5  is a close-up longitudinal section view of the same portion of the mixing device  1  as was depicted in  FIG. 3 . In  FIG. 5  the cap  4  has been pressed towards the vial protector  2  a distance corresponding to complete converging motion between the syringe stopper  60  and the connector piece  50  and between the connector piece  50  and the vial stopper  23 . Thereby, the spike member  52  has properly penetrated the penetrable section  24  of the vial stopper  23  and the spike member  53  has properly penetrated the penetrable section  61  of the syringe stopper  60 , establishing fluid communication between the syringe interior  18  and the vial interior  28  via a lumen  55  extending through the spike members  52 ,  53  and the spike base  54 . 
         [0070]    In this state of the mixing device  1  the tips of the flexible arms  37  are aligned with the respective openings  49  in the sleeve member  40 . A subsequent upwards directed force applied to the cap  4  will therefore cause the flexible arms  37  to deflect out of engagement with the inclined surfaces of the openings  9  and into the openings  49 , allowing the cap  4  to be pulled off. Hence, a design is provided which ensures that the cap  4  is only dismountable from the cap receiving portion  36  once a proper fluid connection is established between the syringe  10  and the vial  20 . 
         [0071]      FIG. 6  shows the mixing device  1  after removal of the cap  4 . In this state of the mixing device  1  the piston rod  14  is exposed and is now operable by the user, e.g. via the push face  15 . 
         [0072]    Operation of the Mixing Device 
         [0073]    In the following a situation of use of the mixing device  1  will be described. To enable reconstitution of the powdered drug the user grips the mixing device  1  and peels off the spacer element  90  by pulling the pull ring  92 . This removes the axial support for the connector piece  50  as well as the barrier for axial movement of the cap  4 . After having removed the spacer element  90  the user holds the vial protector  2  in one hand and the cap  4  in the other and then moves the two hands towards each other to bring together the distal end face of the cap  4  and the proximal end face of the vial protector  2 . Alternatively, the user places the vial protector  2  on an even surface, such as e.g. a table, and, using only one hand, presses the cap  4  towards the vial protector  2 . 
         [0074]    As the cap  4  moves towards the vial protector  2  the respective contact faces  7  exert a driving force on the collar  17 , thereby causing the syringe  10  to move towards the vial  20 . The syringe  10  pushes the stopper fastener  70  in the same direction and the stopper fastener  70  slaves the syringe holder  30  which causes the flexible arms  37  to slide along the wall  46 , while the syringe stopper  60  and the vial stopper  23  converge. The initial position of the syringe holder  30  relative to the sleeve member  40  as well as the axial placement of the openings  49  in the wall  46  are such that when the current clearance, L C , between the distal end face of the cap  4  and the proximal end face of the vial protector  2  satisfies L C =L 1 −(x 1 +x 2 ) the tips of the flexible arms  37  are aligned with the openings  49 . At this relative position of the syringe holder  30  and the sleeve member  40  the cap  4  is dismountable from the cap receiving portion  36  because an axial retraction of the cap  4  from the vial protector  2  will cause the inclined surfaces of the openings  9  to force the flexible arms  37  radially inwards into the openings  49 . 
         [0075]    Also, at this relative position of the syringe holder  30  and the sleeve member  40  the spike members  52 ,  53  have properly penetrated the respective penetrable sections  24 ,  61  to establish fluid communication between the syringe interior  18  and the vial interior  28 . 
         [0076]    The cap  4  is now pulled away from the vial protector  2 , whereby the piston rod  14  becomes exposed for user operation. At this point the user holds the mixing device  1  such that the syringe  10  faces upwards. By depression of the piston rod  14  the piston  19  is advanced in the barrel  11  to force the solvent out through the Luer  12 , further through the lumen  55  and into the vial  20 , where it mixes with the powdered drug. The mixing device  1  is then turned up-side down and the piston rod  14  is gradually released to allow the built up pressure in the vial  20  to cause or assist a transfer of the mixed product out of the vial  20 , through the lumen  55  and into the syringe  10 . Alternatively, or additionally, the piston rod  14  is pulled backwards in the barrel  11  to cause or assist the transfer of the mixed product from the vial  20 . 
         [0077]    Once the mixed product is fully contained within the syringe  10 , the syringe  10  is removed from the remaining parts of the mixing device  1 . This is done by gripping the syringe holder  30  with one hand and the collar  17  with the other hand and then rotating the syringe  10  relative to the syringe holder  30 . Because of the locking engagement between the protrusions  72  and the indentations  33  when the syringe  10  is rotated relative to the syringe holder  30  the Luer collar  13  is screwed out of engagement with the threaded inner portion  71 . A circumferential groove  63  in the syringe stopper  60  is engaged by a mating ridge  73  on the stopper fastener  70  to lock the syringe stopper  60  against axial movement relative to the stopper fastener  70 . Thereby, when the Luer collar  13  is released from the threaded inner portion  71  the syringe  10  can be easily removed from the stopper fastener  70 , leaving the syringe stopper  60  in the remaining part of the mixing device  1 . Thus, the syringe  10  is ready for connection with e.g. a cannula or a catheter immediately upon removal from the arrangement, without the user having to manually detach the syringe stopper  60  from the Luer  12  first. This reduces the number of manual steps to be performed even further.