Abstract:
Syringe assemblies having a passive disabling system to prevent reuse are provided. According to one or more embodiments, the syringe assembly comprises a barrel, plunger rod and stopper wherein the plunger rod further comprises a flexible protrusion that locks the plunger rod within the barrel. Certain embodiments further include a frangible portion on the plunger rod that breaks when reuse is attempted. One or more embodiments include a plunger rod and stopper attachment that prevents disassembly of the syringe assembly prior to use. Syringe assemblies of one or more embodiments also include visual indicators or markers indicating whether a syringe assembly is used or the plunger rod is locked within the barrel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/137,732, filed Jun. 12, 2008, which claims the benefit of priority from U.S. Provisional Application No. 60/943,397, filed Jun. 12, 2007, the disclosures of which are hereby incorporated in its entirety by reference thereto. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present invention relate to syringe assemblies having a passive locking mechanism which restricts distal movement of the plunger rod after injection to prevent reuse, syringe assemblies wherein the stopper and plunger rod operate using relative motion to passively disable the syringe, syringe assemblies including a removeably connected stopper and plunger rod to prevent disassembly of the syringe prior to use and syringe assemblies including visual indication or markings to indicate use of the syringe or a disabled syringe. 
     BACKGROUND 
     Reuse of hypodermic syringe products without sterilization or sufficient sterilization is believed to perpetuate drug abuse and facilitate the transfer of contagious diseases. The reuse of syringes by intravenous drug users further exacerbates the transfer of contagious diseases because they comprise a high-risk group with respect to certain viruses such as the AIDS virus and hepatitis. A high risk of contamination also exists in countries with shortages of medical personnel and supplies. 
     A syringe which can be rendered inoperable after use presents a viable solution to these issues. Various syringes have been proposed and are commercially available that can be disabled by the user by taking active steps to disable the syringe. Single-use syringes that do not require the user to actively disable the syringe are also thought to offer a solution. It would be desirable to provide syringes that are automatically or passively disabled from reuse and can be manufactured in a cost-effective manner by, for example, utilizing fewer parts. Further, markings or other indicators which visually indicate whether a syringe has been used or is disabled would also be desirable. 
     SUMMARY 
     A passive disabling system for a syringe assembly that activates after completion of an injection cycle is provided. A syringe assembly incorporates a stopper and plunger rod attached in a manner to prevent users from disassembling the syringe prior to completion of the injection cycle. In one or more embodiments of the invention, a user can fill, inject and/or reconstitute medication. 
     In this disclosure, a convention is followed wherein the distal end of the device is the end closest to a patient and the proximal end of the device is the end away from the patient and closest to a practitioner. 
     A syringe assembly is provided which includes a barrel, an elongate plunger rod and stopper having respective structures and assembly which allow the user to passively lock the plunger rod within the barrel to prevent reuse of the syringe assembly. The barrel includes a distal end, an open proximal end, a cylindrical sidewall with an interior surface, which defines a chamber in which fluid may be held, and a distal wall. An opening in the distal wall permits fluid to flow from the chamber through the opening. In one embodiment, the barrel includes a marker or indicator which indicates whether the syringe has been disabled or the plunger has been locked within the barrel. 
     In one or more embodiments, the interior surface of the sidewall of the barrel has a continuous diameter or first inner diameter. As used throughout this application, the term “diameter” is a measurement of the longest distance between the walls of the barrel having any cross-sectional shape. However, it will be appreciated that conventional syringes are typically cylindrical with a circular cross-sectional shape. In accordance with some embodiments of the present invention, the barrel includes a rib, locking rib or other such impediment suitable for restricting the proximal movement of the plunger rod, adjacent to its proximal end. In one embodiment, the rib has a second inner diameter, wherein the second diameter is less than the first diameter. One or more embodiments of the present invention include an increased diameter region located proximally from the rib having a third inner diameter, wherein the third diameter is greater than the first diameter and second diameter. A diameter transition region or a ramp having an axial length located between the rib and the increased diameter region may be included. The diameter transition region or ramp can have a varying inner diameter, which increases in the proximal direction. 
     Embodiments of the present invention also include an extended plunger rod which has a proximal end, a distal end, and a main body between the proximal and distal end. A thumb press may also be disposed at the proximal end of the plunger rod. In some embodiments, the plunger rod slides or otherwise moves proximally and distally within the chamber of the barrel. 
     The distal end of the plunger can include a stopper-engaging portion having a distal and proximal end. Alternative embodiments further include an optional disc disposed at the distal end of the plunger rod between the main body and the stopper engaging portion of the plunger rod and/or between the main body and the flexible protrusion (described below). The stopper-engaging portion provides a means for the stopper and plunger rod to move proximally and distally within the barrel. In one or more embodiments, the stopper-engaging portion allows the stopper and plunger rod to move proximally and distally relative to each other. In a specific embodiment, the distal end of the stopper-engaging portion may include a rim, retainer, retaining ring or alternate means suitable for restraining the stopper. The stopper-engaging portion according to one or more embodiments may also include a visual indicator or a visual display that indicates use of the syringe or whether the syringe is disabled. 
     The plunger rod can further include means for locking the plunger rod in the barrel to prevent reuse of the syringe assembly when the syringe is fully injected or “bottomed.” As used herein, the term “bottomed” shall refer to the position of the syringe assembly wherein the stopper, while attached to the plunger rod, is in contact with the distal wall of the barrel and the plunger rod can no longer move in the distal direction. As used herein, the term “activation force” shall mean the force required to bottom the syringe or the force required to move the plunger rod in the distal direction such that the stopper is in contact with the distal wall of the barrel and can no longer move in the distal direction. For example, application of the activation force to the thumb press in the distal direction “activates” or causes the means for locking the plunger rod to move distally past the rib of the barrel. The means for locking the plunger rod can have an outer diameter greater than the inner diameter of the barrel at the rib or the second inner diameter. One or more embodiments of the present invention utilize a protrusion, or annular protrusion that extends radially from the plunger rod as a means for locking the plunger rod. In some embodiments, the protrusion is located between the thumb press and the main body and is an example of a means for locking the plunger rod in the barrel. According to an embodiment of the invention, the protrusion is integrally molded to the plunger rod. The protrusion according to one or more embodiments may be rigid or flexible. Embodiments utilizing a flexible protrusion may further include a support adjacent to the flexible protrusion. 
     In one configuration, the protrusion has an outer diameter greater than the second inner diameter or the diameter of the barrel located at the rib. Once the protrusion distally moves through the diameter transition region, past the rib and into the barrel, it becomes locked by the rib and the plunger rod is prevented from moving in the proximal direction. The protrusion of one embodiment is tapered or otherwise shaped in such a manner such that it may move in the distal direction past the rib more easily. In embodiments utilizing a flexible protrusion, the protrusion may facilitate distal movement of the plunger rod by flexing in the proximal direction as a force is applied to the plunger rod in the distal direction. In one embodiment, the flexible protrusion also flexes as the plunger rod is moved in the distal direction past the rib. The diameter transition region or ramp of the barrel may further facilitate distal movement of the plunger rod. In such embodiments, the ability for the flexible protrusion to flex and the plunger rod to move in the proximal direction may be limited after the flexible protrusion has moved distally past the rib. 
     The plunger rod can further comprise at least one frangible portion or other means for separating a portion of the plunger rod from the body. In this configuration, when a user attempts to reuse the syringe assembly or otherwise pull the plunger in the proximal direction out of the barrel, after the plunger rod has been locked, the plunger rod breaks at the frangible portion, leaving a portion of the plunger rod locked within the barrel. In a specific embodiment, the frangible portion is located between the protrusion and the thumb press. It will be appreciated that the frangible portion can be located in various locations near the proximal end of the plunger rod. In one embodiment, the frangible portion comprises a narrowed frangible connection or a frangible bridge having a dimension that is at least about 50% less than the overall dimension of the plunger rod. More particularly, the dimension can be either the diameter or the width of the plunge rod. In a more specific embodiment, the frangible portion includes a plurality of frangible connections or bridges, which may further include two or more point connections. The plurality of frangible connections or bridges are adapted to withstand application of a force on the plunger rod in the distal direction and to break upon application of a force in the proximal direction after the flexible protrusion has advanced distally past the rib or the syringe has been bottomed. 
     In a specific embodiment, the term “deactivation force” includes the force required to separate a portion of the plunger rod from the body and the term “withdrawal force” includes the force needed to move the plunger rod in the proximal direction after the syringe has been bottomed or the plunger rod has been locked in the barrel by the rib. In a more specific embodiment, the withdrawal force is greater than the deactivation force and the activation force. 
     The stopper has a proximal end and a distal end and the stopper is attached the stopper-engaging portion of the plunger rod. In some embodiments, the stopper moves distally and proximally within the barrel. In one or more embodiments, the stopper also moves distally and proximally along a pre-selected axial distance relative to the stopper-engaging portion of the plunger rod, thereby allowing the protrusion to move distally past the rib into the locked position when the syringe assembly is bottomed. 
     The stopper may further comprise a stopper body or stopper boss at the proximal end of the stopper. A peripheral lip may be included at the proximal end of the stopper body. A frangible link may be provided to connect the stopper to the plunger rod, which may connect the stopper and the peripheral lip. Alternative means for separating the stopper from the plunger rod or to destroy the stopper may also be provided. 
     In one embodiment, when a user aspirates or fills the syringe assembly, the stopper begins to move in the proximal direction in tandem with the plunger rod, while maintaining the pre-selected axial distance. An optional visual indicator or display disposed on the stopper-engaging portion of the plunger rod is visible when the user fills the syringe assembly. In one or more embodiments of the present invention, when a user injects the contents of the syringe assembly, the attachment of the stopper and the stopper-engaging portion allow the plunger rod to move distally for a length of the pre-selected axial distance, while the stopper remains stationary. After the plunger rod travels distally for the length of the pre-selected axial distance, the stopper begins to move distally with the plunger rod. During such distal movement, where a visual indicator or display is utilized, the visual indicator or display disposed on the stopper-engaging portion of the plunger rod is no longer visible. Where a visual marker is utilized, the visual marker disposed on the barrel continues to be visible, even after the plunger rod is locked. As will be more fully described herein, the marker provides an alternative means of indicating the syringe has been disabled. 
     According to one embodiment of the present invention, the total length of the plunger rod is decreased by pre-selected axial distance when the stopper and plunger rod move together in the distal direction during injection of the contents of the syringe assembly. As such, the stopper and stopper-engaging portion of the syringe assembly are attached in a manner such that when a user has fully completed the injection cycle, the protrusion of the plunger rod advances past the rib of the barrel. In some embodiments, once the protrusion advances past the rib of the barrel, it locks the plunger rod within the barrel and prevents the user from reusing the syringe assembly or otherwise pulling the plunger rod out of the barrel. Once the plunger rod is locked within the barrel, the optional visual indicator or display on the stopper-engaging portion of the plunger rod is no longer visible, indicating the syringe has been disabled. 
     According to an alternative embodiment, the stopper and the plunger rod are connected in a fixed relationship such that when the distal end of the stopper is contact with the distal wall of the barrel, the flexible protrusion is permitted to advance distally past the rib in the barrel. In embodiments utilizing a stopper and plunger rod having a fixed relationship, the pre-selected axial distance is zero and application of a continuous force in the proximal direction during aspiration or filling causes the stopper and plunger rod move together. In the initial position as supplied or packaged, the stopper is not in contact with the distal wall of the barrel and, instead, there is a gap between the distal end of the barrel and the distal wall of the barrel. In such embodiments, the user may fill the barrel of the syringe to accommodate the initial gap between the stopper and the distal wall of the barrel. The user may thereafter expel the air present in the barrel from the presence of the gap before injecting the contents of the syringe. During injection and application of a force in the distal direction to the plunger rod, the fixed stopper and plunger rod move together until the stopper reaches the distal end of the barrel and the protrusion is permitted to advance distally within past the rib of the barrel. 
     The syringe assembly may include one or more frangible portions of the plunger rod, which break when a user attempts to move the plunger rod in a proximal direction after the protrusion has advanced past the rib of the barrel. Other suitable means may be utilized for separating a portion of the plunger rod from the main body when the user applies sufficient proximal force to the plunger rod or otherwise attempts to reuse the syringe assembly after it is bottomed. 
     In accordance with one embodiment of the invention, the stopper and the stopper-engaging portion are attached in such a manner such that when a user attempts to disassemble the syringe assembly prior to aspiration, injection or bottoming, the stopper-engaging portion disengages from the stopper, leaving the stopper inside the barrel and allowing the separated plunger rod to be removed. In some embodiments, inner diameter of the barrel at the rib, or the second inner diameter, is less than the outer diameter of the stopper, and thereby prevents the stopper from moving proximally past the rib and causes the stopper-engaging portion to detach from the stopper, leaving the stopper inside the barrel. An optional frangible link of the stopper breaks when a user attempts to disassemble the syringe assembly by applying a continuous force in the proximal direction to the plunger rod prior to aspiration, injection or bottoming. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of a syringe assembly according to an embodiment of the invention shown; 
         FIG. 2  illustrates a disassembled perspective view of a syringe assembly according to an embodiment of the invention; 
         FIG. 3  shows a cross-sectional view of the barrel shown in  FIG. 2  taken along line  3 - 3 ; 
         FIG. 4  is an enlarged view of a portion of the barrel shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of the stopper shown in  FIG. 2  taken along line  5 - 5 ; 
         FIG. 6  is a cross-sectional view of the plunger rod shown in  FIG. 2  taken along line  6 - 6 ; 
         FIG. 7  is a cross-sectional view taken along line  7 - 7  of  FIG. 1 ; 
         FIG. 8  is an illustration of  FIG. 7  showing the plunger rod being moved in the proximal direction; 
         FIG. 9  is an illustration of  FIG. 8  showing the plunger rod being moved in the distal direction; 
         FIG. 10  is an illustration of  FIG. 9  showing the plunger rod in a locked position in the syringe barrel; 
         FIG. 11  is an enlarged view of a proximal portion of the assembly shown in  FIG. 10 ; 
         FIG. 12  illustrates a perspective view of an embodiment of a syringe assembly having a visual marker disposed on the barrel; 
         FIG. 13  illustrates a disassembled perspective view of an embodiment of a syringe assembly with visual indicators or markers disposed on the barrel and the stopper-engaging portion of the plunger rod; 
         FIG. 14  is a cross-sectional view taken along line  14 - 14  of  FIG. 12 ; 
         FIG. 15  is an illustration of  FIG. 14  showing the plunger rod in a locked position in the syringe barrel; 
         FIG. 16  is an enlarged view of a proximal portion of the assembly shown in  FIG. 15 ; 
         FIG. 17  is an illustration of  FIG. 10  showing a proximal portion of the plunger rod being broken from the syringe assembly after the plunger rod has been locked in the syringe barrel; 
         FIG. 18  is an illustration of  FIG. 7  showing the plunger rod being moved in the proximal direction and the stopper disengaging from the plunger rod; 
         FIG. 19  a disassembled perspective view of a syringe assembly according to another embodiment of the invention; 
         FIG. 20  is a perspective view of the plunger rod shown in  FIG. 19 ; 
         FIG. 21  is a side elevational view of the stopper shown in  FIG. 19 ; 
         FIG. 22  is a cross-sectional view taken along line  22 - 22  of the syringe assembly shown in  FIG. 19 ; 
         FIG. 23  is an illustration of  FIG. 22  showing the plunger rod being moved in the proximal direction; 
         FIG. 24  is an illustration of  FIG. 23  showing the plunger rod being moved in the distal direction; 
         FIG. 25  is an illustration of  FIG. 24  showing the plunger rod in a locked position in the syringe barrel; 
         FIG. 26  is an illustration of  FIG. 25  showing a proximal portion of the plunger rod being broken from the syringe assembly after the plunger rod has been locked in the barrel; 
         FIG. 27  is an illustration of  FIG. 22  showing the plunger rod being moved in the proximal direction and the stopper disengaging from the plunger rod; 
         FIG. 28  shows a disassembled perspective view of a syringe assembly according to another embodiment of the invention; 
         FIG. 29  shows a cross-sectional view of the barrel shown in  FIG. 28  taken along line  29 - 29 ; 
         FIG. 30  is an enlarged view of a portion of the barrel shown in  FIG. 29 ; 
         FIG. 31  is a cross-sectional view of the stopper shown in  FIG. 28  taken along line  31 - 31 ; 
         FIG. 32  illustrates a perspective view of the plunger rod shown in  FIG. 28 ; 
         FIG. 33  is a cross sectional view of the plunger rod shown in  FIG. 28  taken along lines  33 - 33 ; 
         FIG. 34  is a cross-sectional view taken along line  34 - 34  of the syringe assembly shown in  FIG. 28 ; 
         FIG. 35  is an illustration of  FIG. 34  showing the plunger rod being moved in the proximal direction; 
         FIG. 36  is an illustration of  FIG. 35  showing the plunger rod being moved in the distal direction; 
         FIG. 37  is an illustration of  FIG. 36  showing the plunger rod in a locked position in the syringe barrel; 
         FIG. 38  is an enlarged view of a proximal portion of the assembly shown in  FIG. 37 ; 
         FIG. 39  is an illustration of  FIG. 37  showing a proximal portion of the plunger rod being broken from the syringe assembly after the plunger rod has been locked in the barrel; and 
         FIG. 40  is an illustration of  FIG. 34  showing the plunger rod being moved in the proximal direction and the stopper disengaging from the plunger rod. 
     
    
    
     DETAILED DESCRIPTION 
     Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways. 
     One aspect of the present invention provides for a syringe assembly including a barrel, plunger rod and stopper having individual features and construction which allow the user to passively lock the plunger rod within the barrel to prevent reuse of the syringe assembly. 
       FIG. 1  shows a syringe assembly  100  according to one or more embodiments. As shown in  FIG. 2 , the syringe assembly includes a barrel  120 , a plunger rod  140  and a stopper  160 , arranged such that the proximal end  169  of stopper is attached to the distal end  141  of the plunger rod. The connected stopper  160  and plunger rod  140  are inserted into the proximal end  129  of the barrel  120 . 
     As best shown in the  FIG. 3 , the barrel  120  has a cylindrical sidewall  110  with an interior surface  126  that defines a chamber  128 . In one embodiment, the chamber  128  holds the contents of the syringe assembly which may include medication in powdered or fluid form. The barrel  120  is shown as having an open proximal end  129 , a distal end  121 , and a distal wall  122 . The distal wall  122  has an opening  111  in fluid communication with the chamber  128 . 
     The sidewall  110  of the barrel  120  defines a chamber having a continuous inner diameter along the longitudinal axis of the syringe. Alternatively, the barrel can include a sidewall has an inner diameter, which decreases linearly from the proximal end to the distal end. It is to be understood that the configuration shown is merely exemplary, and the components can be different in shape and size than shown. For example, the barrel can have an exterior prism shape, while retaining a cylindrical interior shape. Alternatively, both the exterior and interior surfaces of the barrel can have non-circular cross-sectional shapes. 
     The syringe barrel  120  is shown as having a peripheral flange  124  attached at the proximal end  129  of the barrel  120 . The barrel  120  further includes a needle cannula  150 , having a lumen  153  attached to the opening  111  in the distal wall  122  of the barrel  120 . As is known in the art, attachment means  152  is provided for attaching the needle cannula  150  to the distal wall  122 . The assembly  100  may also include a protective cap over the needle cannula (not shown). 
     As shown more clearly in  FIG. 4 , the barrel  120  further includes a rib  123  adjacent its proximal end  129 . The inner diameter of the barrel at the location of the rib  123  is smaller than the inner diameter of the barrel  120  at other locations along the length of the barrel. One or more optional tabs or detents can be used to create a region of the barrel having a diameter smaller than the inner diameter of the barrel  120 . In a specific embodiment, the rib can include a ring formed along entire circumference of the interior surface  126  or a portion of the interior surface  126  of the inner diameter of the barrel  120  (not shown). The barrel  120  also includes a diameter transition region  127  adjacent to the rib  123  at the proximal end  129  (as shown in  FIG. 3 ) of the barrel  120 . The inner diameter of the barrel at the diameter transition region  127  increases from the distal end  121  to the proximal end  129  (as shown in  FIG. 3 ) of the barrel  120 . In the embodiment shown, the barrel includes an increased diameter region  125  adjacent to the diameter transition region at the proximal end  129  (as shown in  FIG. 3 ) of the barrel. The inner diameter of the barrel  120  at the increased diameter region  125  is greater than the inner diameter of the barrel of the entire diameter transition region  127 . 
     The barrel may be made of plastic, glass or other suitable material. The barrel further includes optional dosage measurement indicia (not shown). 
     Referring now to  FIG. 5 , the stopper  160  has a distal end  161 , a proximal end  169 , a stopper body  164  and a peripheral edge  162  which forms a seal with the interior surface  126  of the barrel. In one or more embodiments, the peripheral edge  162  of the stopper  160  has a larger diameter than the diameter of the interior surface of the rib  123 . The stopper  160  shown in  FIG. 5  includes an optional elongate tip  166  on its distal end  161  to facilitate reduction of the residual fluid and expulsion of fluid from the syringe barrel. 
     The stopper  160  is shown as further having a tapered portion  165  adjacent to the stopper body  164  at its proximal end  169 . A neck  163  is adjacent to the tapered portion  165  at the proximal end  169  of the stopper  160 . The stopper body  164  is shown as also including an interior recess  168 , which allows the stopper-engaging portion  146  of the plunger rod  140  to connect to the stopper  160 . A peripheral rim  147  may be provided to help retain the stopper  160  on the plunger rod  140 . As with the rib of the barrel, detents or tabs can be used to retain the stopper  160  on the plunger rod  140 . 
     The stopper is typically made of plastic or other easily disposable and/or recyclable material. It may be desirable to incorporate natural or synthetic rubber in the stopper or use a natural or synthetic rubber seal with the stopper. It will be understood that the stopper may incorporate multiple seals. 
     Referring now to  FIG. 6 , the syringe assembly includes a plunger rod  140  having a proximal end  149 , a distal end  141 , and a main body  148  extending between the proximal end  149  and distal end  141 . The plunger rod  140  further includes a thumb press  142  at the proximal end  149  of the plunger rod  140 . In the embodiment shown, the thumb press  142  further includes a textured surface, writeable surface and/or label. 
     Still referring to  FIG. 6 , the plunger rod  140  further includes a protrusion  144  shown as an annular protrusion  144  between the thumb press  142  and the main body  148 . The outer diameter of the plunger rod at the protrusion  144  is greater than the inner diameter of the barrel  120  at the rib  123 . In some embodiments of the invention, the protrusion  144  includes a tapered portion  145  that facilitates distal movement of the protrusion past the rib  123  and into the barrel  120 , as will become apparent in the subsequent discussion of operation of the syringe. In at least one embodiment, the syringe assembly is configured to allow the protrusion  144  to advance distally past the rib  123 , to lock the plunger rod in the barrel when the user bottoms out the plunger rod in the barrel (as more clearly shown in  FIGS. 10-11 ). In certain embodiments, the plunger rod  140  further includes at least one frangible connection or point  143  for separating at least a portion of the plunger rod from the main body when a user applies sufficient proximal force to the plunger rod after it has been locked. In the embodiment shown, the frangible point  143  is located between the protrusion  144  and the thumb press  142 . It will be understood that the frangible connection or point  143  shown is exemplary, and other suitable means for permanently damaging the plunger rod or otherwise separating at least a portion of the plunger rod from the main body may be provided. 
     In the embodiment shown, the stopper  160  is permitted to move distally and proximally within the barrel when connected to the stopper-engaging portion  146  of the plunger rod  140 . As will be understood better with the description of operation of the syringe assembly and with reference to  FIG. 7 , the stopper is capable of moving distally and proximally a pre-selected axial distance  132  relative to the stopper-engaging portion. 
     In alternative embodiments, the stopper is fixed with respect to the plunger rod. In such embodiments, the axial distance may now be zero. It will be appreciated that in such embodiments, the syringe will be in an initial position, as supplied, where there is a gap between the stopper and the distal wall of the barrel. As the user fills the syringe, the stopper and the plunger rod move together in a proximal direction. As the user expels the contents of the syringe, the stopper and the plunger rod move together in the distal direction, the flexible protrusion is permitted to move past the locking rib. 
     The plunger rod may be made of plastic or other suitable material. The protrusion may also be comprised of plastic or a harder material suitable for locking the plunger rod within the barrel. 
     In  FIG. 7 , the barrel  120  holds the stopper  160  and plunger rod  140  in the chamber, wherein the stopper is bottomed, “parked” or is in contact with the distal wall  122  of the barrel  120 . The peripheral edge of the stopper  162  forms a seal with the interior surface  126  of the barrel  120 . In one embodiment, the stopper  160  is connected to the stopper-engaging portion  146  of the plunger rod  140 . The stopper-engaging portion  146  is removeably held in the recess  168  of the stopper body  164  by the neck  163 . 
     In  FIG. 7 , a gap between stopper  160  and the distal end of the main body  148  defines a pre-selected axial distance  132  prior to the injection cycle. In at least one embodiment, the protrusion  144  remains on the proximal side of the rib  123  because the length of the plunger rod  140  and stopper combined, along with the pre-selected axial distance  132 , is greater than the length of the barrel  120  from the distal wall  122  to the proximal end of the barrel  120 . The distance between the protrusion  144  and the peripheral edge  162  of the stopper body  164  defines a first distance, D 1 . 
       FIG. 8  illustrates the syringe assembly in use and specifically shows an aspiration or filling step, according to one or more embodiments of the present invention. When the user applies a force to the plunger rod  140  in the proximal direction shown by the arrow in  FIG. 8 , the plunger rod  140  and the stopper  160  move together in the proximal direction, while the stopper-engaging portion  146  is connected to the stopper  160  by the rim  147 . In one or more embodiments, the gap defining the pre-selected axial distance  132  is maintained while the stopper  160  and plunger rod  140  move together in the proximal direction along the interior surface of the syringe barrel. The user terminates the application of proximal force on the plunger rod  140  once the desired amount of medicament is drawn into the syringe. During the aspiration step, the plunger rod and the stopper body move in the proximal direction together to draw medication into the syringe, while maintaining the first distance D 1 . 
       FIG. 9  also shows the syringe assembly in use and specifically demonstrates application of distal force to the plunger rod during injection. In one embodiment, when the user applies a force in the distal direction to the plunger rod  140  as indicated by the arrow, the plunger rod  140  moves in a distal direction for the length of the gap defining the pre-selected axial distance  132  in  FIG. 7 , while the stopper  160  remains stationary. The stopper  160  remains stationary because the frictional force created by the peripheral edge  162  of the stopper on the interior surface  126  of the barrel is greater than the frictional force created by the stopper-engaging portion  146  entering the recess  168  of the stopper  160 . Consistent with at least one embodiment, once the stopper-engaging portion has distally moved the length of the pre-selected axial distance  132  and is in contact with the proximal end of the recess  169 , the stopper  160  and the plunger rod  140  begin to move in tandem in the distal direction. Further, the force applied by the user is greater than the friction between the peripheral edge  162  of the stopper  160  and the interior surface  126  of the barrel, and therefore the stopper  160  is forced to move in the distal direction with the plunger rod  140 . In one embodiment, the user may inject a limited amount of the fluid aspirated or exert a limited force on the plunger rod in the distal direction to flush or expel some of the aspirated fluid, without locking the plunger rod, provided that the syringe assembly is not bottomed. However, as will be described further with respect to  FIG. 10 , a user may bottom the stopper against the distal wall of the syringe barrel, locking the plunger rod in the barrel. 
     When expelling the contents of the syringe, the plunger rod moves in a distal direction the length of the pre-selected axial distance  132  shown in  FIG. 7  while the stopper body remains stationary, consequently closing the gap defining the pre-selected axial distance  132 . After the contents of the syringe have been fully expelled, the distance between the protrusion  144  and the peripheral edge  162  defines a second distance, D 2 , wherein D 2  is the difference between the first distance, D 1 , and the gap defining a pre-selected axial distance  132 . 
       FIG. 10  illustrates an embodiment of the syringe assembly after the plunger rod has been locked inside the barrel. In one or more embodiments, the entry of the stopper-engaging portion into the recess  168  of the stopper  160  (as also shown in  FIG. 9 ) closes the gap defining the pre-selected axial distance  132 , allowing the protrusion  144  to advance past the locking rib  123  (as more clearly shown in  FIG. 11 ). The protrusion  144  has an outer diameter greater than the inner diameter of the barrel at the rib  123 . Accordingly, in one or more embodiments, the rib  123  locks the protrusion  144  inside the barrel  120 , and prevents proximal movement of the plunger rod  140 . 
       FIG. 12  shows a syringe assembly  100  in which the barrel  120  includes a visual marker  300 . The marker is aligned with the rib  123 , as more clearly shown in  FIG. 16 . The marker can be integrally formed on the sidewall of the barrel or can be added to the exterior surface of the sidewall. The marker can be printed in ink, adhesively applied, a textured surface or a separate piece that is fixed around the syringe barrel. The marker can form a ring around the circumference of the side wall or be in the form of tabs disposed at regular intervals around the circumference of the side wall. In a specific embodiment, the marker is a colored stripe. In a more specific embodiment, the marker can include text in the form of one or more letters and/or numbers, geometric shapes, symbols or combinations thereof to inform users the syringe is disabled. 
       FIG. 13  shows a plunger rod  140  having a visual indicator or display  310  disposed on the stopper-engaging portion  146 . As with the visual marker  300 , the visual indicator  310  can be integrally formed with the stopper-engaging portion of the plunger rod or be added to the exterior surface thereof. The indicator or display can be printed in ink, adhesively applied, a textured surface or a separate piece that is fixed to the stopper engaging portion. In one or more embodiments, the indicator or display can comprise a pattern, a solid portion and or can cover the entire surface of the stopper-engaging portion. In a specific embodiment, the indicator is a colored stripe disposed along the length of the stopper-engaging portion  146  between the distal end  141  and the main body  148  of the plunger rod. In a more specific embodiment, the indicator is a colored stripe disposed along the circumference of the stopper-engaging portion  146  of the plunger rod. In an even more specific embodiment, the marker can include text in the form of one or more letters and/or numbers, geometric shapes, symbols or combinations thereof. 
     As more clearly shown in  FIG. 14  a gap between stopper  160  and the distal end of the main body  148  defines a pre-selected axial distance  132  prior to the injection cycle. The visual indicator  310  is visible when the gap is present. The visual marker  300  is disposed on the exterior surface of the barrel  120  and aligned with the rib  123 . As described with reference to  FIG. 8 , when the user applies a force to the plunger rod  140  in the proximal direction shown by the arrow in  FIG. 8 , the plunger rod  140  and the stopper  160  move together in the proximal direction, while the stopper-engaging portion  146  is connected to the stopper  160  by the rim  147 . In one or more embodiments, the gap defining the pre-selected axial distance  132  is maintained while the stopper  160  and plunger rod  140  move together in the proximal direction along the interior surface of the syringe barrel. Accordingly, the visual indicator  310  continues to be visible. 
     As described with reference to  FIG. 9 , when expelling the contents of the syringe, the plunger rod moves in a distal direction the length of the pre-selected axial distance  132  shown in  FIGS. 7 and 14  while the stopper body remains stationary, consequently closing the gap defining the pre-selected axial distance  132 . The movement of the stopper-engaging portion, in the distal direction relative to the stopper allows the stopper-engaging portion  146  of the plunger rod to move into the recess  168  of the stopper (as shown in  FIG. 9 ). As can be more clearly seen in  FIG. 15 , this relative movement allows the stopper body  164  to cover the stopper-engaging portion and block visibility of the visual indicator  310 . 
     As more clearly shown in  FIGS. 15 and 16 , the visual marker  300  disposed on the barrel  120  and aligned with the rib  123  also shows advancement of the protrusion  144  past the rib  123 . In addition, the entry of the stopper-engaging portion into the recess  168  of the stopper  160  (as also shown in  FIG. 9 ) also closes the gap defining the pre-selected axial distance  132 , allowing the protrusion  144  to advance past the rib  123  (as more clearly shown in  FIGS. 11 and 16 ). The location of the protrusion relative to the visual marker indicates whether the plunger rod has been locked within the barrel and the syringe assembly has been disabled. Before the plunger rod is locked, the protrusion  144  is proximally adjacent to the visual marker  300 . Once the plunger rod is locked, the protrusion  144  is distally adjacent to the visual marker  300 . 
     It will be appreciated that each of the visual marker  300  and the visual indicator  310  can be used alone or in combination. 
       FIG. 17  shows the assembly after the plunger rod  140  has been locked in the barrel  120 . An attempt to reuse the syringe assembly by applying a force to the plunger rod  140  in the proximal direction causes a portion of the plunger rod  140  to separate at the frangible connection or point  143 . The frangible connection or point  143  is designed so that the force holding exerted on the protrusion by the locking rib  123  while proximal force is being applied to the plunger rod  140  is greater than the force needed to break the plunger rod at the frangible point  143  and, therefore, the frangible point breaks or separates before the user is able to overcome the force exerted on the protrusion by the rib. 
       FIG. 18  shows the syringe assembly in a configuration in which the stopper  160  has separated from the stopper-engaging portion  146 . According to one or more embodiments of the invention, the stopper  160  and stopper-engaging portion  146  disengage to prevent a user from disassembling the parts of the syringe assembly prior to use. As otherwise described in reference to  FIG. 5 , the peripheral edge  162  of the stopper  160  has a diameter greater than the diameter of the interior surface of the rib  123 . Consistent with at least one embodiment of the invention, when a user applies a force to the plunger rod  140  in the proximal direction, the rib  123  locks the peripheral edge  162  of the stopper  160 , and the rim  147  of the stopper-engaging portion  146  disconnects from the neck  163  of the stopper. The rib  123  exerts a greater force on the peripheral edge of the stopper than the force or friction exerted by the rim of the stopper-engaging portion of the plunger rod and neck portion of the stopper while proximal force is applied to the plunger rod. 
       FIG. 19  shows an example of a syringe assembly  200  according to another embodiment of the present invention. In the embodiment shown in  FIG. 19 , the assembly includes a barrel  220 , a plunger rod  240  and a stopper  260 , arranged so that the proximal end of stopper  269  is attached to the distal end of the plunger rod  241 . The stopper  260  then plunger rod  240  is inserted into the proximal end of the barrel  229 . A flange  224  is attached at the proximal end  229  of the barrel  220 . The barrel  220  further includes a needle cannula  250  having a lumen  253 , attached to the opening in the distal wall  222  at the distal end  221  of the barrel  220 . One or more embodiments also include an attachment hub  252  for attaching the needle cannula  250  to the distal wall  222 . The assembly may also include a protective cap over the needle cannula (not shown). 
     Similar to the barrel illustrated previously in  FIGS. 3 and 4 , and as shown in  FIG. 22 , the barrel further include a rib  223 , locking rib or other means for locking the plunger rod within the barrel, having an interior surface with a smaller diameter than the diameter of the interior surface of the barrel. 
     Referring now to  FIG. 20 , a perspective view of a plunger rod  240  is shown as having a main body  248 , a distal end  241  and a proximal end  249 . The plunger rod  240  further includes a thumb press  242  at its proximal end and a stopper-engaging portion  246  at its distal end. Plunger rod  240  also includes a protrusion in the form of an annular protrusion  244  between the thumb press  242  and the main body  248 . The protrusion  244  may include a tapered portion  245  to facilitate distal movement of the protrusion  244  past the rib  223  into the barrel  220 . In some embodiments, the protrusion  244  has an outer diameter greater than the inner diameter of the barrel at the rib  223 . In at least one embodiment, the configuration of the syringe assembly allows for the protrusion  244  to advance distally past the rib  223 , to lock the plunger rod  240  in the barrel  220 , when the user bottoms the syringe assembly (as more clearly shown in  FIGS. 25-26  and discussed further below). 
     The plunger rod  240  shown further includes at least one frangible point  243 . In the embodiment shown, the frangible point  243  of the plunger rod  240  is located between the protrusion  244  and the thumb press  242 , but the frangible point could be in another location. A stopper-engaging portion  246  is included on the distal end  241  of the plunger rod  240 . As shown, the stopper-engaging portion  246  also includes a plunger recess and a retainer  247 . At least one embodiment of the invention includes a press-fit attachment or other suitable means for retaining the end of the stopper. 
     Referring now to  FIG. 21 , which shows an embodiment of the stopper  260  having a distal end  261  and a proximal end  269 . According to at least one embodiment, the stopper  260  includes a peripheral edge  262  which forms a seal with the interior wall of the barrel  220  and has a diameter greater than the diameter of the interior surface of the barrel at the location of the rib  223  (as more clearly shown in  FIGS. 22-24 ). As shown, an elongate tip  266  is provided at the distal end  261  of the stopper  260  to help expel the entire contents of the syringe. The stopper  220  can further include a stopper body  264  having a peripheral lip  263  at its proximal end  269 , according to at least one embodiment of the invention. Further, the stopper  260  can include a stopper frangible connection  265  connecting the stopper body  264  to the stopper  260 . 
     In this configuration, the stopper  260  and plunger rod  240  occupy the chamber of the barrel  220  and the stopper is bottomed against the distal wall of the barrel. Further, the peripheral edge  262  of the stopper  260  forms a seal with the interior surface of the barrel  220 . The stopper  260  is connected to the stopper-engaging portion  246  of the plunger rod  240 . As shown, the retainer  247  of the stopper-engaging portion  246  retains the peripheral lip  263  of the stopper  260 . 
     Embodiments of the syringe assembly of  FIGS. 19-27  can also include a visual marker  300 , visual indicator  310  or both, as described with reference to  FIGS. 13-16 . In a specific embodiment, the barrel  220  of one or more embodiments can also include a visual marker aligned with the locking rib  223 . In a more specific embodiment, the syringe assembly can include a visual indicator disposed on the stopper body  264 . 
     According to one or more embodiments, there is a gap between the stopper  260  and the distal end of the main body  248  defining a pre-selected axial distance  232 . In one or more embodiments, the distance between the protrusion  244  and the peripheral edge  262  of the stopper  260  defines a first distance, D 1 . 
       FIG. 23  illustrates the syringe assembly in use and specifically shows movement of the plunger rod during an aspiration or filling step according to one or more embodiments of the present invention. When the user applies a force to the plunger rod in the proximal direction, the plunger rod  240  and the stopper  260  move together in the proximal direction as indicated by the arrow, while the stopper-engaging portion  246  is connected to the stopper  260  by the rim  263 . In this configuration, the gap defining the pre-selected axial distance  232  is maintained while the stopper  260  and plunger rod  240  move together in the proximal direction. The user applies proximal force to the plunger rod until a predetermined or desired amount of medicament is aspirated or drawn into the syringe. During the aspiration step, the plunger rod and the stopper body move in the proximal direction together to draw medication into the syringe, while maintaining the first distance D 1 . 
       FIG. 24  also shows the syringe assembly when distal force is applied to the plunger rod during an injection step according to at least one embodiment of the present invention. Application of a force in the distal direction closing the gap and moving the pre-selected axial distance  232  shown in  FIG. 22 , while the stopper  260  remains stationary. Consistent with at least one embodiment, once the stopper-engaging portion  246  has distally moved the pre-selected axial distance  232  and is in contact with stopper frangible connection  265 , the stopper  260  and the plunger rod  240  begin to move in tandem in the distal direction. 
     When expelling the contents of the syringe, the plunger rod moves in a distal direction the length of the pre-selected axial distance  232  while the stopper body remains stationary. During and after the contents of the syringe have begun to be or have been fully expelled, the distance between the protrusion  244  and the peripheral edge  262  defines a second distance, D 2 , wherein D 2  is the difference between the first distance, D 1 , and the gap defining a pre-selected axial distance  232 . 
     In one embodiment, the user may inject a limited amount of the fluid aspirated or exert a limited force on the plunger rod in the distal direction to flush or expel some of the aspirated fluid, without locking the plunger rod, provided that the syringe assembly is not bottomed. However, as will be described further below, a user will typically expel substantially all of the contents of the syringe by bottoming the stopper on the distal wall of the barrel. 
     Referring now to  FIG. 25 , which illustrates the syringe assembly after the plunger rod  240  has been locked inside the barrel  220 , the distal movement of the stopper-engaging portion  246  to the stopper frangible connection  265  of the stopper  260  (as also shown in  FIG. 24 ) closes the gap defining the pre-selected axial distance and allows the protrusion  244  to advance past the rib  223 , thereby locking the plunger rod  240  inside the barrel  220 , preventing re-use of the syringe assembly 
     Referring now to  FIG. 26 , the syringe assembly is shown in a configuration in which a user attempts to reuse the syringe assembly after the plunger rod  240  is locked inside the barrel  220  by applying a force to the plunger rod  240  in the proximal direction. Application of sufficient proximal force to the plunger rod causing a portion of the plunger rod  240  to separate at the frangible connection or point  243 , as the holding force of the protrusion  244  and the rib exceeds the breaking force of the frangible point or connection. 
       FIG. 27  shows the syringe assembly in a configuration after which proximal force has been applied to the plunger rod and the stopper has moved to the proximal end of the barrel. As shown in  FIG. 27 , the stopper  260  has separated from the stopper-engaging portion  246  of the plunger rod. The stopper frangible connection  265  breaks to prevent a user from disassembling the parts of the syringe assembly. As otherwise described herein, the peripheral edge of the stopper  262  has an outer diameter greater than the inner diameter of the interior surface of the barrel at the location of the rib  223 . Consistent with at least one embodiment of the invention, when a user applies a force to the plunger rod  240  in the proximal direction, the rib  223  of the barrel  220  locks the peripheral edge  262  of the stopper  260 , and the stopper frangible connection  265  breaks, separating the stopper body  264  from the stopper  260 . Without being limited by theory, it is believed that the force required to break the stopper frangible connection is less than the force exerted on the peripheral edge of the stopper. 
       FIG. 28  shows an example of a syringe assembly  400  according to another embodiment of the present invention. In the embodiment shown in  FIG. 28 , the assembly includes a barrel  420 , a plunger rod  440  and a stopper  460 , arranged so that the proximal end of stopper  469  is attached to the distal end of the plunger rod  441 . The stopper  460  then plunger rod  440  is inserted into the proximal end of the barrel  429 . The barrel includes a flange  424  attached at the proximal end  429  of the barrel  420  and a needle cannula  450  having a lumen  453  attached to the opening in the distal wall  422  at the distal end  421  of the barrel  420 . One or more embodiments also include an attachment hub  452  for attaching the needle cannula  450  to the distal wall  442 . 
     The barrel as shown more clearly in  FIG. 29  further includes a cylindrical sidewall  410  with an inside surface  426  defining a chamber  428 . As more clearly shown in  FIG. 30 , the barrel further includes a rib  423 , locking rib or other means for locking the plunger rod within the barrel, having an interior surface with a smaller diameter than the diameter of the interior surface of the barrel. The distal end of the rib  423  further includes a distal portion  412  facing the distal end of the barrel  421 . It will be understood that the rib  423  and the distal portion of the rib  412  can have different shapes and configurations. A ramp  427  is disposed proximally adjacent to the rib  423  having an increasing diameter from the rib to the open proximal end. An increased diameter region  425  is disposed proximally adjacent to the ramp  427 . The increased diameter region  425  may have the same or larger diameter than the inside surface of the barrel  426 . 
     Referring now to  FIG. 31 , which shows an embodiment of the stopper  460  having a distal end  461  and a proximal end  469 . According to at least one embodiment, the stopper  460  includes a sealing edge  462  which forms a seal with the inside surface of the barrel  426  and has a diameter greater than the diameter of the inside surface of the barrel at the location of the rib  423  (as more clearly shown in  FIGS. 29 and 30 ). The stopper  460  can further include a stopper body  464  defining an interior recess  468  and a neck  463  disposed at its proximal end  469 , according to at least one embodiment of the invention. According to one or more embodiments, the stopper may be formed from an elastomeric or plastic material. The stopper may also be formed from other known materials in the art. 
     Referring now to  FIG. 32 , a perspective view of a plunger rod  440  is shown as having a main body  448 , a distal end  441  and a proximal end  449 . The plunger rod  440  further includes a thumb press  442  at its proximal end and a stopper-engaging portion  446  at its distal end. Plunger rod  440  also includes a flexible protrusion  444  between the thumb press  442  and the main body  448  and a support  445  proximally adjacent to the flexible protrusion, which provides additional stability to the plunger use and syringe  400  during use. In some embodiments, the flexible protrusion  444  has an outer diameter greater than the inner diameter of the barrel at the rib  423 . In at least one embodiment, the configuration of the syringe assembly allows for the flexible protrusion  444  to advance distally past the rib  423 , to lock the plunger rod  440  in the barrel  420 , when the user bottoms the syringe assembly (as more clearly shown in  FIGS. 37-38  and discussed further below). The plunger rod may further include an optional pair of discs  430 ,  431  disposed on the distal end and proximal end of the main body  448 . The discs  430 ,  431  provide additional stability and may have alternate shapes, depending on the shape of the barrel. 
     As shown in  FIG. 33 , the plunger rod  440  further includes a plurality of frangible connections or bridges  443  adjacent to the support  445 . In the embodiment shown, the plurality of frangible connections  443  of the plunger rod  440  is located between the support  445  and the thumb press  442 , but the frangible connections could be in another location. 
     The distal end of the plunger rod  441  further includes a stopper-engaging portion  446 . As shown, the stopper-engaging portion  446  also includes a retaining ring  447  for retaining the neck  463  of the stopper  460 . At least one embodiment of the invention includes a press-fit attachment or other suitable means for retaining the end of the stopper. 
     When assembled, the stopper  460  is connected to the stopper-engaging portion  446  of the plunger rod  440 . In the embodiment shown in  FIG. 34 , the stopper  460  and plunger rod  440  may occupy the chamber of the barrel  420  with the distal end  461  of the stopper face positioned against the distal wall of the barrel  422 . Further, the sealing edge  462  of the stopper  460  forms a seal with the interior surface of the barrel  420 . As shown, the retaining ring  447  of the stopper-engaging portion  446  retains the stopper  460 . As will be more fully described with reference to  FIG. 40 , the connection between the retaining ring  447  and stopper-engaging portion  446  may be frangible. 
     Embodiments of the syringe assembly  400  may also include visual markers as described with reference to  FIGS. 13-16 . In a specific embodiment, the barrel  420  of one or more embodiments can also include a visual marker aligned with the locking rib  423 . In a more specific embodiment, the syringe assembly can include a visual indicator disposed on the stopper body  464 . 
     Referring now to  FIGS. 34-35 , a defined space between the stopper  460  and the distal end of the main body  448  defining a pre-selected axial distance  432 . In one or more embodiments, the distance between the flexible protrusion  444  and the sealing edge  462  of the stopper  460  defines a first distance, D 1 . 
     The aspiration or filling step, the injection step and the locking step is shown in  FIGS. 35-38 . As with the embodiments of  FIGS. 7-11 ,  14 - 16  and  22 - 24 , when the user applies a force to the plunger rod in the proximal direction, the plunger rod  440  and the stopper  460 , joined by the neck  463  and retaining ring  447 , move together in the proximal direction as indicated by the arrow. As shown in  FIG. 35 , the space defining the pre-selected axial distance  432  and the first distance D 1  is maintained as the stopper  460  and plunger rod  440  move together in the proximal direction.  FIG. 36  shows the syringe assembly  400  when distal force is applied to the plunger rod  440  during an injection step. This force causes the plunger rod  440  to move the pre-selected axial distance  432  shown in  FIG. 34  while the stopper  460  remains stationary. This closes the space between the plunger rod  440  and stopper  460  as the plunger rod  440  moves into the interior recess  468 . Application of a continuous force in the distal direction to the plunger rod causes the stopper  460  and the plunger rod  440  to move in tandem in the distal direction. 
     During and after the contents of the syringe have begun to be or have been fully expelled, the distance between the flexible protrusion  444  and the sealing edge  462  defines a second distance, D 2 , wherein D 2  is the difference between the first distance, D 1 , and the space defining a pre-selected axial distance  432 . 
     As described otherwise herein, the user of the syringe assembly  400  may inject a limited amount of the fluid aspirated or exert a limited force on the plunger rod in the distal direction to flush or expel some of the aspirated fluid, without locking the plunger rod, provided that the syringe assembly is not bottomed. 
     Referring now to  FIGS. 37-38 , which illustrate the syringe assembly after the plunger rod  440  has been locked inside the barrel  420 , the distal movement of the stopper-engaging portion  446  relative to the stopper  460  closes the gap defining the pre-selected axial distance and allows the flexible protrusion  444  to advance past the rib  423 , thereby locking the plunger rod  440  inside the barrel  420 , preventing re-use of the syringe assembly. 
     According to one or more embodiments, the flexible protrusion  444  permits the plunger rod to bottom during normal use of the syringe assembly. Specifically, the flexible protrusion  444  flexes as it moves past the narrowed diameter of the rib  423  of the barrel. In one or more embodiments, as the protrusion  444  moves distally past the rib  423 , a slight increase in force may be applied to the plunger rod. According to the embodiment shown, this slight increase in force applied to the plunger rod is not perceptible to a user during normal use of the syringe. Further, the ramp  427  of the barrel facilitates movement of the flexible protrusion  444  past the rib  423 . After the flexible protrusion  444  has advanced distally past the rib  423 , the distal portion of the rib  412  restricts movement of the flexible protrusion  444  in the proximal direction. It is believed that the activation force, as defined herein, is less than the force required to withdraw the plunger rod. 
     Referring now to  FIG. 39 , the syringe assembly  400  is shown in a configuration in which a user attempts to reuse the syringe assembly after the plunger rod  440  is locked inside the barrel  420  by applying a withdrawal force, as defined herein, to the plunger rod  440  in the proximal direction. Application of sufficient proximal force to the plunger rod causing a portion of the plunger rod  440  to separate at the plurality of frangible connections  443 , as the withdrawal force exceeds the deactivation force needed to separate a portion of the plunger rod from the body or break the plurality of frangible connections or bridges. 
       FIG. 40  shows the syringe assembly  400  in a configuration after which proximal force has been applied to the plunger rod and the stopper has moved to the proximal end of the barrel. As otherwise described herein, the sealing edge of the stopper  462  has an outer diameter greater than the inner diameter of the interior surface of the barrel at the location of the rib  423  and therefore, application of a force in the force in the proximal direction causes the stopper  460  to separated from the stopper-engaging portion  446  of the plunger rod 
     According to one or more embodiments, the syringe barrel may include identifying information on the syringe assembly. Such information can include, but is not limited to one or more of identifying information regarding the contents of the syringe assembly or information regarding the intended recipient. 
     Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.