Abstract:
An injection device is provided with dual medicament chambers and a mixing pen needle assembly, whereby predetermined dosages of two medicaments can be provided to a mixing reservoir in the pen needle assembly and delivered simultaneously with the injection device.

Description:
RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 13/869,545, filed on Apr. 24, 2013, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention is in the field of injection devices. Specifically, the disclosure pertains to a medication pen adapted to deliver a mixture of separately dosed medications with a single injection. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    Medication pens are widely used for self-administered injectable drugs such as insulin. And patients are often required to take medications in combination with each other. For example, insulin is co-administered with glucagon like peptide (“GLP”). Therefore, it would be desirable if medications could be mixed at the time of use and co-administered with the convenience of a medication pen. The conventional thinking in the art is that a compact medication delivery device capable of mixing and delivering two medications with a pen needle would require a complicated valved manifold to keep the two medications from mixing. 
         [0004]    U.S. Pat. No. 5,542,760, to Chanoch et al, incorporated by reference in its entirety, describes a syringe filler for mixing different types of insulin in a syringe. A syringe is inserted into a syringe holder assembly which is rotatably mounted on a housing for containing two medication cartridges. Using the syringe holder, the syringe may be aligned with either of the two medication cartridges. A separate dose is loaded into the syringe from each cartridge, thus avoiding the complications associated with free-mixing different types of insulin for diabetic patients who require different types of insulin. 
         [0005]    The disadvantage of the device is that the syringe must be separately handled to conduct the filling process and the injection. Therefore, it would be desirable to have a pen-type device that can deliver mixtures of individually dosed medications. 
         [0006]    U.S. Pat. No. 7,645,264, to Marsh et al., also incorporated by reference, discloses a medication pen having a collapsible secondary reservoir in addition to a primary reservoir (such as a cartridge). The secondary reservoir is used to provide a mechanical advantage when delivering medication to tissue layers encountering relatively high backpressure such as an intradermal space. Medication flows from the cartridge of a pen device to the axially aligned secondary reservoir in the pen needle with little or no backpressure. An injection is administered by collapsing the collapsible secondary reservoir and the delivery force of the injection is controlled by the relative sizes of the primary and secondary reservoirs. However, the pen-type device disclosed does not house more than one cartridge nor is the secondary reservoir used to mix different medications. 
         [0007]    The present invention improves over the aforementioned prior art by providing an injection device having a pen needle assembly that can be installed on a housing containing a plurality of medication compartments, such that medications individually dosed from the plurality of medication compartments can be mixed in the pen needle assembly and delivered simultaneously. 
       SUMMARY OF THE INVENTION 
       [0008]    Thus, in one aspect, the invention is a medication pen comprising: a pen body having a distal end and a proximal end, and having a first medication compartment and a second medication compartment. First and second dosing mechanisms located proximally of the medication compartment are engaged with first and second dosage plungers engaged in the respective first and second medication compartments. A movable housing received on the distal end of the pen body is adapted to be received in first and second positions on the pen body and a pen needle assembly is received on the distal end of the movable housing. The pen needle assembly comprises a patient end needle, a filler needle, and a collapsible mixing reservoir intermediate and accessed by the patient end needle and the filler needle. The movable housing is movable between a first position in which the filler needle is in fluid communication with the first medication compartment and a second position in which the filler needle is in fluid communication with the second medication compartment. 
         [0009]    The user attaches the pen needle assembly to the movable housing and uses the dosing mechanism to partially fill the mixing reservoir with medication from the first medication compartment. The movable housing is then moved to the second position and the filling step is repeated to fill the mixing reservoir with medication from the second medication compartment. Inserting the patient end needle into the patient&#39;s tissue and pressing distally toward the injection site collapses the mixing reservoir and forces medication in the mixing reservoir through the patient end needle during an injection. 
         [0010]    Although described herein in connection with the co-administration of insulin and GLP, the device may be used with other medications and combinations suitable for use with a medication pen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an exploded perspective view of a medication pen according to an embodiment of the invention. 
           [0012]      FIG. 2  is a perspective view of the medication pen of  FIG. 1  with the pen needle assembly installed. 
           [0013]      FIG. 3  is a cross-sectional view of the mixing medication pen according to an embodiment of the present invention. 
           [0014]      FIG. 4  is an enlarged cross sectional view of a pen needle assembly according to an embodiment of the invention. 
           [0015]      FIG. 5  is an exploded view of the medication pen showing the construction of the dosing mechanism according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    In the following description, the “distal” direction is the direction toward the patient end needle and the injection site. The “proximal” direction is the opposite direction, typically but not necessarily toward the end of the injection device with the dosage knob. The drawings are not to scale. 
         [0017]    A medication pen  100  according to the invention has a pen body  30 , with at least two medication compartments  32 ,  34 . A fillable pen needle assembly  20  is attached to a movable housing  40  on the distal end of the pen body. The movable housing  40  permits the pen needle assembly  20  to access the medication in each medication compartment  32 ,  34  as described below. 
         [0018]    As seen in  FIG. 1 , the medication compartments  32 ,  34  can be arranged side by side in the pen body. Typically, disposable cartridge assemblies  300 ,  302  containing multiple doses of medication to be mixed and co-administered are inserted into the respective medication compartments  32 ,  34  of the medication pen. For example, a first cartridge containing insulin is provided in a first compartment and another cartridge containing GLP is provided in the second compartment. Access to the medication compartments may be provided by way of a door on the side of the pen body, or the cartridges can be slid axially into an opening on the distal end of the pen body, as shown in  FIG. 1 . 
         [0019]    The medication compartments  32 ,  34  are associated with respective dosing mechanisms  200 ,  202 . The medication compartments and dosing mechanisms are substantially identical, such that a description of one compartment and dosing mechanism will serve to describe both of them. Moreover, dosing mechanisms known in the art may be adapted for use with the present invention. Incorporated herein by reference for this purpose are U.S. Pat. No. 7,018,364 (Bendek et al.); U.S. Pat. No. 6,936,032 (Burbank et al.); U.S. Pat. No. 5,961,495 (Lee et al.); U.S. Pat. No. 6,585,698 (Packman et al.); U.S. Pat. No. 6,932,794 (Bendek et al.); U.S. Pat. No. 6,248,095 (Giambattista); U.S. Pat. No. 6,096,010 (Lee et al.); U.S. Pat. No. 6,277,099 (Strowe et al.); and U.S. Pat. No. 6,221,053 (Walters et al.). 
         [0020]      FIG. 5  shows the lower part of pen body  30  with the top removed to depict the position of the dosing mechanism chamber  57  and the medication compartment  32  in the pen body  30 . Each medication compartment  32 ,  34  receives a medication cartridge assembly  300 ,  302  securely retained in an internal space of pen body  30 . As shown in the cross sectional view of  FIG. 3 , medication cartridge assembly  300  includes an open proximal end and a distal end having an elastomeric seal  311  securely mounted thereto. A plunger  18  is disposed in sliding fluid tight engagement in the medication cartridge assembly  300 . Plunger  18  initially is disposed substantially adjacent the proximal end of medication cartridge assembly  300 . Moving the plunger in a distal direction forces medication from the medication cartridge assembly  300  into mixing reservoir  26  in the pen needle assembly. The plunger  18  of the cartridge assembly engages distal end of lead screw  88  of the dosage mechanism, as described below. 
         [0021]    The dosing mechanism  200  for dosing and dispensing medication from the respective medication cartridges  300 ,  302  into the mixing reservoir  26  may be adapted from the abovementioned U.S. Pat. No. 5,542,760, which is incorporated by reference. As described in the aforesaid patent, and as shown in the exploded view of  FIG. 5 , a suitable dispensing mechanism is disposed distally of the medication compartment  34  and includes a nut  54  having opposed proximal and distal ends  56  and  58  respectively. Exterior surface regions of nut  54  define a plurality of longitudinally extending splines  59 . Proximal end  56  of nut  54  is characterized by a plurality of longitudinally extending resilient fingers with enlarged ends that enable snap engagement of nut  54  into driver  50 . Distal end  58  of nut  54  is radially enlarged to fit in a collar  53  in the pen body and limit axial movement of nut  54  in chamber  57 . 
         [0022]    Dosing mechanism  200  further includes a clutch assembly  52  mounted therein. Clutch assembly  52  includes a proximal clutch  44 , a distal clutch  46  and an annular spring  48  biasingly engaged between the proximal and distal clutches. Proximal and distal clutches  44 ,  46  each are configured for non-rotatable engagement over splines  59  of nut  54 . Distal clutch  46  includes an array of distally facing saw teeth dimensioned, disposed and configured for engagement with teeth on the interior of the pen body  30 , such that distal clutch  46  can rotate only in one direction relative to the pen body  30 . 
         [0023]    Dosing mechanism  200  further includes a generally cylindrical driver  50  having opposed proximal and distal ends. Driver  50  receives nut  54 , such that distal end of the driver  50  is snap fit over the enlarged ends of resilient fingers at proximal end of nut  54 . This snap fit engagement prevents axial movement between nut  54  and driver  50 , but permits free relative rotational movement within chamber  57 . The distal end of driver  50  is also characterized by an array of saw teeth  95  that engage with corresponding teeth on proximal clutch  44 . Outer surface regions of driver  50  are characterized by splines  55  extending radially outwardly thereon and along a substantial portion of the length of driver  50 . 
         [0024]    Dosing mechanism  200  further includes a dose knob  60  which is a hollow generally cylindrical structure. Inner surface  64  of the dosage knob  60  is characterized by axially extending grooves  68  which are disposed and dimensioned for engagement with splines  55  on driver  50 . Dose knob  60  is spline mounted over driver  50  so that axially extending grooves  68  in dose knob  60  engage splines  55  of driver  50  to prevent relative rotation between the dosage knob and the driver, but permitting relative axial movement in chamber  57 . Outer surface  66  of dose knob  60  is characterized by a groove  67  that includes an axial component and a tangential component at opposed ends of the axial component. Portions of outer surface  66  of the dosage knob are provided with dosage indicia (not shown) to define dose amounts corresponding to different positions along groove  67 . Proximal end of dose knob  60  is characterized by a gnarled exterior surface to facilitate manipulation for setting a selected dose, and may include indicia  79  to facilitate setting the dosage knob at a particular setting. An actuator button  76  is snapped in to engage with proximal end of dose knob  60  while permitting relative rotation of the dose knob  60  with respect to the actuator button  76 . 
         [0025]    Inner surface of chamber  57  includes a button  86  dimensioned and disposed to engage in groove  67  of dose knob  60 . Window  133  is disposed to enable indicia on dose knob  60  to be visible to the user as dose knob  60  is rotated and button  86  travels along groove  67 . 
         [0026]    Dosing mechanism  200  further includes a lead screw  88  with opposed proximal and distal ends, and an array of external threads  94 . Threads  94  are engaged in nut  54 , such that proximal end of lead screw  88  is within chamber  57  and a driver head  97  at the distal end of the lead screw projects distally beyond collar  53  into the medication compartment, where it engages the plunger  18  of the medication cartridge. 
         [0027]    Dosing mechanism  200  is assembled by sliding clutch assembly  52  over splines  59  on nut  54 . Driver  50  is then sufficiently urged onto nut  54  in a distal direction for snap fit engagement with nut  54 . In this snapped engagement, proximal clutch  44  will be engaged with distal end of driver  50 . Spring  48  will maintain constant selected pressure between the clutch and the driver. Dose knob  60  is then slid onto driver  50 , and actuator button  76  is snapped into engagement with proximal end of dose knob  60 . Lead screw  88  is threaded into nut  54 . 
         [0028]    Assembled dispensing mechanisms  200  and  202  are inserted into respective chambers in pen body  30  proximally of the respective medication compartments  32 ,  34 . 
         [0029]    The details of the dosing and dispensing mechanism described above are not critical and other mechanisms described in the prior art may be adapted for use with the mixing pen according to the present invention provided that the mechanisms permit the user to dispense a predetermined amount of medication into the mixing reservoir of the pen needle assembly as described below. For example, the invention is described above in connection with a user operated dose setting mechanism, but the dosing mechanism could also be adapted to dispense a predetermined amount of medication into the mixing reservoir from each medication compartment without the user setting a dose. 
         [0030]    Further, the term “medication pen” is used herein broadly to refer to any injection device other than a syringe. A medication pen differs from a syringe in that it is adapted for use with pre-packaged medication so that the user does not have to withdraw medication from a vial using the syringe. As understood in the art, a “pen needle” and a “pen needle assembly” refer to an assembly that is attached to the body of a medication pen. As distinguished from a syringe, a pen needle assembly is characterized by a filler needle on the proximal end of the assembly to access the medication compartment in the body of the medication pen. The use of the term “pen” does not imply any limitation regarding the shape or construction of the injection device, such as the placement of the actuator on the proximal end of the device. 
         [0031]    To prepare for a mixing operation, the user screws the fillable pen needle assembly  20  onto the movable housing  40  on the distal end of the pen body  30 . Threads may be provided on the housing for this purpose. In the embodiment shown In  FIG. 1 , movable housing  40  is provided with an externally threaded opening  43  protruding from a distal end of the housing  40 . The opening allows threaded attachment of pen needle assembly  20  with the movable housing  40 . As shown in  FIG. 2 , when moved in the proximal direction, movable housing  40  slides over pen body  30  so that a filler needle can access one or the other of medication compartments  32  and  34 . Alternatively, pen needle assembly  20  is provided with external threads, and the movable housing  40  provided with an opening having internal threads. This allows selective engagement of the pen needle assembly with the medication compartment  32 ,  34  via the movable housing without adding length to the movable housing. Other configurations would be apparent to those of ordinary skill in the art, such as a recessed opening on the distal end of the movable housing adapted to receive the proximal end of the pen needle assembly and provide access to the medication compartment. For example, the pen needle may be adapted for a snap fit engagement with an appropriate opening in the movable housing  40 . It may be desirable in some embodiments to have the entire pen needle assembly formed integrally with the movable housing  40 . 
         [0032]    After the pen needle assembly  20  is installed on the movable housing  40  and the filler needle is inserted into the first medication compartment in the first position, the user sets and activates the dosing mechanism  200  to fill a predetermined quantity of a first medication into the mixing reservoir  26  of the pen needle assembly  20 . 
         [0033]    As seen  FIG. 3  and  FIG. 4 , the fillable pen needle assembly  20  has a patient end needle  22  for performing the injection, a filler needle  24  to access the medication compartments  32 ,  34  and a collapsible mixing reservoir  26  between the patient end needle  22  and the filler needle  24 . As commonly practiced in the art, the pen needle assembly  20  may be disposable, while the cartridge contains medication for several doses. The pen body and dosing mechanisms typically last the lifetime of the cartridge or longer. The pen needle assembly may comprise a first removable cover (not shown) on the patient end needle  22  which is removed prior to administering an injection and a second removable cover (not shown) over the filler needle  24  which is removed prior to installing the pen needle assembly on the movable housing  40 . In embodiments, a disposable needle stop  29  is separately installed on the pen needle assembly  20  such that the patient end needle with its integral support is adapted for one time use, while the mixing reservoir  26  of the pen needle assembly is used multiple times. 
         [0034]    As shown in  FIGS. 1 and 2 , the movable housing  40  is movable in a proximal direction so that filler needle  24  pierces septum  311  of the medication cartridge  300  of a first medication compartment  32  in a first position. In the embodiment of  FIG. 1  and  FIG. 2 , the movable housing  40  is attached to pen body  30  via shaft  62  which slides into pen body  30 . Shaft  62  permits the housing  40  to be moved distally from the first position on the pen body, withdrawing the filler needle  24  from the medication compartment  32  without completely separating the pen needle assembly  20  from the pen body. Shaft  62  and movable housing  40  may then be rotated 180 degrees so that the pen needle assembly  20  is aligned with the second medication compartment  34 . The movable housing  40 , with the pen needle assembly  20  attached, is then moved proximally to a second position where the filler needle pierces the septum of a cartridge in the second medication compartment. Travel stops (not shown) may be provided on the shaft  62 , engaging with stops (not shown) on the interior of the pen body  30 , limiting the distal and proximal movement and rotation of the housing about the shaft to assist the user to place the pen needle assembly  20  in alignment with the respective medication compartments  32 ,  34 . While the rotating housing is a presently preferred embodiment for the movable housing, other modes of moving the housing from a first position to a second position are within the skill of the ordinarily skilled artisan to adapt. Further, the pen body  30  may be constructed so as to permit medication compartments  32  and  34  to be moved with respect to the dosing mechanism. Thus, pen body  30  may be rotatable about a shaft so that a single dosing mechanism is used for multiple steps of filling mixing reservoir  26 . 
         [0035]    In the embodiment depicted in the cross-sectional view of  FIG. 3 , pen needle assembly  20  is shown attached to housing  40  on the distal end of pen body  30 . Pen needle assembly  20  includes patient end needle  22 , and filler needle  24 , which accesses cartridge assembly  300  in medication compartment  32  located within the pen body  30 . In the cross sectional view, only one medication compartment is shown, however, the details are the same for each medication compartment. Typically, the medication compartment  32  is adapted to receive a cartridge or other medication receptacle. However, in some applications, it may be desirable to maintain the medicament within the medication compartment without the use of a separate cartridge. As used herein, the “medication compartment” encompasses the compartment with a cartridge included, unless the context requires otherwise. 
         [0036]    The pen needle assembly  20  includes collapsible mixing reservoir  26  intermediate the medication compartment  32  and the patient end needle  22 . The filler needle  24  includes septum penetrating cannula penetrating the cartridge septum  311  and an opposite end accessing the collapsible mixing reservoir  26 . Preferably, check valve  23  allows fluid to flow from the medication compartment into the mixing reservoir  26 , but prevents fluid from entering either of medication compartment  32 ,  34  from the mixing reservoir  26 . The patient-end needle  22  is supported on needle stop  29  and has a first proximal end accessing the collapsible mixing reservoir and a distal patient end. 
         [0037]    Referring to the enlarged detail of  FIG. 4 , the pen needle assembly  20  comprises a proximal portion  130  attached to the movable housing  40  which is secured on pen body  30 . Proximal portion  130  slides within distal portion  230 . The proximal portion  130  comprises an opening for attachment to housing  40  via threads or other means, a medial wall  140  supporting the filler needle  24 , and mixing reservoir wall  110  extending distally from the medial wall  140 . The mixing reservoir wall  110  terminates in travel limits  5   a  which limit the travel of the distal portion  230  with respect to the proximal portion  130 . The distal portion comprises a front sleeve  120  and a sliding seal  180  affixed to the distal portion  230 , sliding within and sealing off mixing reservoir  26 . Travel limits  5   b  engage travel limits  5   a  on the reservoir wall to prevent distal movement of the distal portion  230  beyond a predetermined point. The volume of the mixing reservoir  26  expands to a fully filled state when the travel limits  5   a  and  5   b  of the proximal portion  130  and distal portion  230 , respectively, contact one another. The travel limits  5   a ,  5   b  are preferably 90 degree flanges on the exterior walls of the front sleeve  120  and reservoir wall  110 , respectively. A sliding seal  180  receives the proximal end of the patient needle  22  and extends into reservoir  26 . The proximal end of the sliding seal  180  slides within the mixing reservoir  26 , while the exterior wall  110  of mixing reservoir  26  fits between the interior wall of the front sleeve  120  and the sliding seal  180 . 
         [0038]    With the exception of the patient needle  22  and the septum penetrating cannula  24 , the moving parts of the needle assembly  20  are preferably made from plastic by injection molding or other suitable process. The patient needle  22  and septum penetrating filler needle  24  may be made of surgical-quality metals, such as stainless steel. The septum penetrating filler needle  24  and check valve  23  may be secured in place by snap-fitting, interference-fitting, adhesives, welding or other means known in the art. 
         [0039]    To perform the mixing operation, the user selects an amount of medication to be delivered from the first compartment by turning the dosage knob  60  on the first dosage mechanism, which limits the stroke of the lead screw  88  and plunger  18 . The user then advances the dose knob toward the pen body. The relative movement of the dose knob causes the lead screw and plunger to move toward the pen needle assembly  20 . During this “loading stroke,” the plunger, which abuts the lead screw, passes through the medication compartment (typically, within the cartridge) and drives medicament from the cartridge assembly  300  into the mixing reservoir  26 . As described above, the movable housing  40  with the pen needle attached is moved distally to disengage the filler needle  24  from the first medication compartment  32 , rotated to align the filler needle with the second medication compartment  34 , and moved proximally to engage the filler needle  24  with the second medication compartment. 
         [0040]    To perform an injection, the device is placed on the patient&#39;s skin such that the needle is seated into the tissue. The patient needle  22  is inserted into the skin as far as the needle stop, with mixing reservoir  26  partially closed. It will be appreciated that the needle length and gauge can be modified depending on whether the injection is being applied subdermally, intradermally, or intravenously, for example. Once the needle stop  29  is seated on the skin, a downward force is applied to the device by grasping the outer sleeve. The force exerted on the outer sleeve drives the housing toward the needle stop  29 . This movement causes axial movement of the seal  180  within the mixing reservoir towards the medial wall  140 , thus, collapsing the volume of the mixing reservoir  26  and causing the check valve to seal the pathway between the cartridge and the mixing reservoir  26 . In the process of collapsing the volume of the mixing reservoir  26 , the device  100  pressurizes the medicament in the mixing reservoir  26 , thereby driving it through the patient needle  22 . 
         [0041]    The above description of the preferred embodiments is not to be deemed limiting of the invention, which is defined by the following claims. The foregoing description should provide the artisan of ordinary skill with sufficient information to practice variants of the embodiments described. Features and improvements described in connection with one embodiment may be combined with other embodiments without departing from the scope of the invention.