turning to the figures , fig1 depicts an exemplary embodiment of the present needle safety guard device 5 and related components in an unassembled arrangement . as will be discussed in greater detail herein , fig1 shows a drug vial 200 , needle guard 40 housing a syringe 10 , clip 90 , and plunger 30 . in fig1 , the clip 90 is shown separated from the rest of the safety device to better illustrate the features of the clip 90 , however , in a preferred embodiment the clip 90 is connected to the main part of the safety device 5 as shown in fig2 . in accordance with one aspect of the present disclosure , a medicine cartridge , such as a syringe 10 is provided ( fig1 ). preferably , the syringe 10 has a substantially smooth - walled cylindrical barrel 12 , a hub or distal end 14 that is the administration end , and a proximal end 16 having a flange 18 . the cylindrical barrel 12 typically is manufactured from substantially clear glass . alternatively , the barrel 12 may be manufactured from plastic , e . g ., polypropylene , k - resin , or polycarbonate , and the like . the barrel 12 of the syringe 10 may be pre - filled with a diluent , or may be filled with the diluent at a later step . preferably the syringe 10 , if pre - filled , also comprises a label or markings that indicates the quantity and type of diluent . for example , a sticker or label may be attached to the barrel 12 of the syringe 10 which provides the name of the diluent and the volume of the diluent . the diluent may be of any type known in the art including , but not limited to , sterile water , saline , 5 % aqueous dextrose or the like . alternatively , the user may aspirate the diluent into the syringe from a vial or container . the proximal end 16 of the barrel 12 is configured to receive a stopper 20 and a plunger 30 ( fig1 and 7 ). the stopper 20 is configured to be slidably coupled into the cylindrical barrel 12 and movable from a proximal position to a distal position . the stopper 20 is preferably made of pliable rubber , thermoplastic rubber , plastic or similar material . the plunger 30 comprises a stem 32 , a distal end 34 , and a radial portion or thumb pad 36 ( fig1 ). the plunger 30 is generally made of plastic , e . g . polypropylene , k - resin , or polycarbonate , or the like . the distal end 14 of the cylindrical barrel 12 preferably comprises a needle port or luer fitting ( fig1 ). the luer fitting may be configured to couple with several different sizes of needles with different diameters and lengths or with other components that include a luer fitting or other type of holder . the needles and components may be connected by a luer connector , luer slip , luer , or other holder as is known in the art . the luer fitting can be either of the slip version ( no threads ) or include threads . the luer fitting is configured to allow interchanging of the needle and / or components so a user may use the most appropriate needle or component during filling the syringe , reconstitution , and administration of the medication to a patient . a first needle or reconstitution needle 8 can be attached to the luer fitting ( fig5 ). the reconstitution needle 8 is preferably used during reconstitution and then replaced by a second , administration needle 15 ( fig6 and 8 ) prior to administration of the medication . the syringe 10 is housed inside the needle guard 40 wherein the needle guard 40 is preferably a passive needle guard ( fig1 ). safety shield devices generally function , by covering the needle with a rigid cylindrical shield that surrounds the needle and projects far enough beyond the distal tip of the needle so as to prevent a user &# 39 ; s finger from coming in contact with the needle tip ( fig8 ). to prevent a user from forgetting to deploy the safety shield , preferred safety devices operate passively or automatically by providing a mechanism that initiates and physically executes the shielding of the needle after the injection has been completed . the passive needle guard 40 generally comprises a body 50 for receiving and holding the syringe 10 , a shield 60 slidably attached to the body 50 , and a spring mechanism 55 ( fig8 ). both the body 50 and the shield 60 are generally molded from plastic , such as , polypropylene , k - resin , or polycarbonate , or the like . in a preferred embodiment , the body 50 and the shield 60 are substantially clear to facilitate observation of the syringe 10 therein . alternatively , the body 50 and the shield 60 may be translucent or opaque , and may be colored , such as a latex color , a flesh tone , or a primary color . the body 50 may comprise opposing side rails defining two elongate openings or windows 51 extending at least partially between a proximal end 52 and a distal end 53 of the body 50 ( fig8 ). the shield 60 is a tubular member adapted to slidably fit on the body 50 and has a proximal end 62 and a distal end 64 ( fig1 and 8 ). in a preferred embodiment , one or more trigger fingers 66 extend proximally from the proximal end 62 of the shield 60 ( fig7 ). the trigger fingers 66 may include a first catch 68 that is configured to engage a second catch 58 on the proximal end 52 of the body 50 of the needle guard 40 . engagement between the first catch 68 and the second catch 58 retains the shield 60 in a first , retracted position . this latched configuration is further secured by an angled orientation of the latch surfaces , which when combined with the force of the spring 55 urging these surfaces against each other , places a component of force on the trigger fingers 66 directed toward the centerline . preferably , the one or more trigger fingers 66 are elongate fingers having a proximal tip 67 that is engageable by the thumb pad 36 of the plunger 30 as it is depressed to axially compress and deflect the one or more trigger fingers 66 radially outwardly , as is discussed further below . in a preferred embodiment , the shield 60 further includes an anti - rotation tab 69 which extends proximally from the proximal end 62 ( fig2 and 6 ). the anti - rotation tab 69 interacts with the flange 18 of the syringe 10 and prevents rotation of the syringe 10 . once the needle guard 40 has been activated , the anti - rotation tab 69 is no longer in proximity to the flange 18 and the syringe can be rotated as desired . the passive needle guard 40 also includes a spring mechanism 55 coupled to the body 50 and the shield 60 for biasing the shield 60 towards an extended position when the trigger fingers 66 are deflected radially ( fig8 ). the clip 90 is removably coupled with the needle guard 40 . the clip 90 can include a tab 95 that creates a physical barrier to removal of the plunger from the needle guard safety device 5 ( fig3 and 4 ). when the plunger is moved proximally , the tab 95 on the clip 90 prevents a user from accidentally removing the plunger 30 ( fig3 ). to prevent the relative motion of the safety shield 60 during the steps of reconstitution , the clip 90 retains the shield in the retracted position through the interaction of one or more extensions 94 , 96 disposed on the distal and proximal portions of the clip 90 that interact with the shield 60 and body 50 of the needle guard 40 ( fig1 and 4 ). in a preferred embodiment , the proximal extensions 94 extend axially from the clip 90 and are removably coupled with a proximal portion of the body 50 . the distal region of the clip 90 preferably includes one or more distal extensions 96 that are removably coupled with the proximal end 62 of the shield 60 . the interaction of the extensions 94 , 96 with the shield and body prevent the movement of the shield distally with respect to the body . therefore , even if the trigger fingers 66 are triggered during reconstitution , the shield cannot transition to the second , extended position and instead remains in the retracted position . in a most preferred embodiment , the extensions 94 , 96 retain the body and shield in a slightly closer position than the trigger fingers 66 would on their own . this arrangement facilitates the relatching of the trigger fingers 66 following the reconstitution process as discussed below . in an alternative embodiment , the clip 90 can be configured to interact with the distal end of the needle guard 40 to retain the shield 60 and body 50 in the retracted position when the clip 90 is attached . in this embodiment , the extensions 94 , 96 of the clip 90 can be configured to engage ( 1 ) the distal end 64 of the shield 60 and ( 2 ) the body 50 slightly proximal of a catch 92 disposed near the distal end 53 of the body 50 . in a preferred embodiment , the clip 90 includes a pair of opposing ribs 98 that extend laterally from the sides of the clip 90 . the ribs 98 are designed to facilitate removal of the clip 90 following the reconstitution step as discussed further below . the syringe 10 can be used to administer a lyophilized or concentrated drug to a patient . the lyophilized drug or concentrated drug may be of any type known to those of skill in the art . preferably , the lyophilized or concentrated drug is stored in a vial 200 or container such as a glass vial ( fig1 ). the vial 200 may include a cover such as a rubber stopper , septum , or cap that can be penetrated by a needle . in a preferred embodiment , the vial 200 is made of a substantially clear glass so that the user can ensure that the diluent and lyophilized drug have been properly and fully mixed . assuming that the syringe is pre - filled with a diluent , the steps of reconstituting the drug and administering it into the patient would be to first insert the reconstitution or first needle 8 into the drug vial 200 . the plunger 30 is then advanced distally to expel the diluent from the syringe 10 into the drug vial 200 . if the syringe is not pre - filled with the diluent , the first step in the process would be to aspirate diluent into the syringe from a vial or other source of the desired diluent . all other steps in the process would proceed as described above . it is at this point that the problems with existing safety devices would arise , since advancing the plunger 30 to expel the diluent in the drug vial 200 would trigger the safety shield mechanism of existing safety devices . with the shield now covering the distal end of the device , the rest of the reconstitution steps would be impossible to perform and , additionally , the injection needle would not be accessible in order to inject the patient . the clip 90 prevents the shield from transitioning to the extended position . specifically , the extensions 94 , 96 disposed on the distal and proximal portions of the clip 90 interact with shield 60 and body 50 such that the shield is retained in the first , retracted position . the plunger 30 can then travel the full stroke to empty the syringe contents during reconstitution . even though the safety shield mechanism will have been triggered ( i . e . the thumb pad 36 will contact the trigger fingers 66 ), the shield 60 will not advance to the shielded position because the interaction of the extensions 94 , 96 on the clip 90 maintain the shield in the first , retracted position . because the trigger fingers 66 have an elastic force urging them back into the latched position , the latch mechanism is reversible if the shield 60 has not moved forward . when the plunger 30 is pulled proximally to draw the drug mixture from the vial 200 into the syringe 10 , the trigger fingers 66 will relatch themselves against the second catch 58 on the body 50 so that the needle guard 40 is able to trigger the next time the plunger 30 is advanced sufficiently distally ( fig6 ). after the drug has been dissolved in the diluent , the plunger 30 is withdrawn proximally , pulling the drug mixture into the syringe 10 ( fig3 ). in a preferred embodiment , a circumferential rib 35 on the distal end 34 of the plunger 30 interferes with the tab 95 on the clip 90 preventing the full withdrawal of the plunger 30 , so that users will not inadvertently and surprisingly remove the stopper 20 from the syringe 10 and expose the drug to a non - sterile environment ( fig4 ). preferably , the needle 8 used for reconstitution is replaced with an injection needle 15 having a luer fitting ( fig6 ). the anti - rotation tab 69 on the proximal end of the shield prevents rotation of the syringe within the needle guard . preventing rotation of the syringe facilitates removal and coupling of needles or other components to the luer lock . the clip 90 is then removed in order to administer the medication . the medication is now ready for injection into the patient and the needle guard 40 should deploy in the normal manner after the medication has been injected into the patient . as discussed above , the thumb pad 36 of the plunger 30 is sized and shaped to displace the trigger fingers 66 laterally away from the latched position that connects them to the body 50 to an unlatched position that substantially disconnects them from the body 50 when the plunger is advanced sufficiently far forward distally , preferably far enough forward that the contents of the syringe 10 are expelled , but before the plunger 30 is arrested by the stopper 20 reaching the distal end of the syringe 10 ( fig7 and 8 ). as the medication is being injected into the patient , the plunger 30 will displace the trigger fingers 66 causing the force of the spring 55 to move the shield 60 forward preventing the trigger fingers 66 from relatching and initiating the deployment of the safety shield 60 . the dotted lines in fig7 depict the movement of the trigger fingers 66 from the latched position to the unlatched position . after the plunger 30 is fully advanced and the safety shield mechanism has been released , the shield 60 is either moved distally relative to the syringe 10 and needle 15 or the syringe 10 and needle 15 are moved proximally with respect to the shield 60 . passive or automatic deployment of the safety shield 60 is accomplished by way of the compression spring 55 pushing the shield 60 distally and / or the syringe 10 and needle 15 proximally . the spring force is released to the shield 60 and body 50 when the trigger fingers 66 are displaced from the latch configuration . the spring 55 is of sufficient size to move the shield 60 far enough to shield the needle 15 from the user ( fig8 ). in a preferred embodiment , a locking mechanism holds the shield in the extended position . the locking mechanism may comprise , for example , a set of cooperating detents or catches 92 , 93 on the shield 60 and body 50 that maintain the shield in the extended position ( fig6 ). regardless of the relative motion of the safety shield 60 , what is common to all devices is that the safety shield 60 is actuated after the plunger has been advanced to empty the syringe contents . although preventing the shield from deploying or moving distally over the syringe has been described , it is understood that the present invention would also apply to devices that move the syringe and needle proximally . while the invention is susceptible to various modifications , and alternative forms , specific examples thereof have been shown in the drawings and herein described in detail . it should be understood , however , that the invention is not to be limited to the particular forms or methods disclosed , but to the contrary , the intention is to cover all modifications , equivalents , and alternatives falling within the spirit and scope of the appended claims .
the present disclosure describes a needle guard device or system that can be used with drugs requiring reconstitution . the needle guard is preferably a passive needle guard that can be used during reconstitution without activating the safety mechanism . following administration of the medication , the needle guard shields a user from inadvertent needle sticks by extending a protective shield over the needle .