Patent Description:
Injection devices, such as syringes, are medical delivery devices configured to administer a medicinal fluid (e.g., pharmaceutical, medicament) to a patient. Syringes may be provided in a prefilled form, wherein medicinal fluid is disposed within the syringe at, for example, the time of manufacture of the syringe, or in an empty - or prefillable - form, wherein medicinal fluid is filled from a vial or other source by an end user close in time to injecting the medicinal fluid with the syringe.

Syringes commonly comprise a stopper displaceable by a plunger within a syringe barrel in order to administer the medicinal fluid to a patient. With respect to prefilled syringes, the storage time of the syringe, or the time between filling the syringe with medicinal fluid and administering the medicinal fluid to the patient, can vary widely. As the storage time increases, the interaction between the medicinal fluid and the stopper may affect the potency of the stored medicinal fluid. Maintaining proper drug potency for the duration of storage is important to user safety and efficacy of treatment with the medicinal fluid. Examples of syringes including stoppers and stopper assemblies are given in <CIT>, <CIT>, <CIT>, and <CIT>.

One solution to prevent contact between the medicinal fluid and the stopper is provided in <CIT>. The sealing stopper of the syringe of <CIT> is provided with a resin film laminated along an exterior surface of the sealing stopper such that the resin film is in contact with the medicinal fluid and in contact with an inner surface of the barrel along which the sealing stopper slides. This solution requires the material of the resin film to be tested for compatibility with the material of the sealing stopper in order to assure proper lamination and for compatibility with the medicinal fluid. As a result, additional regulatory approval may be required. Further, an actuation force that must be applied by the user to the plunger in order to displace the sealing stopper within the barrel may vary compared to uncoated sealing stoppers. As a result, the injection rate may be unexpectedly modified for the user. Therefore, there is a need for an injection device that overcomes the foregoing setbacks.

An objective of the present disclosure is to provide a stopper assembly that fluidly isolates a stopper from a medicinal fluid such that the medicinal fluid may be stored in the injection device without a change in the potency of the medicinal fluid.

Another objective of the present disclosure is to provide the aforementioned stopper assembly that does not affect the actuating force applied to a plunger rod of an injection device including the stopper assembly such that the actuating force may be the same as the actuating force applied for an injection device comprising a stopper without a sealing element as described herein.

To this end, the present disclosure describes a stopper assembly configured to be disposed in a barrel of an injection device containing a medicinal fluid. The stopper assembly comprises a stopper and a sealing element. The stopper has a laterally outermost surface configured to be directly engaged with an inner surface of the barrel. The sealing element is coupled to and axially distal relative to the stopper in the barrel. The sealing element has a laterally outermost surface configured to be directly engaged with the inner surface of the barrel and to sealingly isolate the stopper from the medicinal fluid in the barrel.

Certain preferred but non-limiting features of the stopper assembly described above are the following, taken individually or in combination:.

According to the invention, there is provided an injection device as defined in claim <NUM> and in the corresponding dependent claims. The invention proposes an injection device comprises a barrel, a plunger rod, and the stopper assembly described above disposed in the barrel. The barrel extends axially between a distal end and a proximal end. The barrel is configured to contain a medicinal fluid. The plunger rod has a distal end and a proximal end. The distal end of the plunger rod is disposed in the barrel.

Certain preferred but non-limiting features of the injection device described above are the following, taken individually or in combination:.

The illustrations presented herein are not meant to be actual views of any particular component, device, or system, but are merely idealized representations which are employed to describe embodiments of the present invention. Other features, goals, and advantages of the present invention will appear more clearly upon reading of the detailed description that follows and with references to drawings provided by way of non-limiting examples wherein:.

As used herein, the term "proximal" refers to a location, such as a proximal end, that is nearer to a point of reference such as a point of contact of a user applying a force to a plunger rod of an injection device as described herein. As used herein, the term "distal" refers to a location, such as a distal end, that is farther from a point of reference such as a point of contact of the user applying a force to the plunger of the injection device as described herein. Thus, the terms "proximal" and "distal" refer to, for example, directions nearer to and farther from, respectively a user administering a medicinal fluid to a patient.

As used herein, the terms "axial," "axially," "longitudinal," and "longitudinally" generally mean and refer to a direction along or parallel to a longitudinal axis of an element(s) of the injection device described herein.

As used herein, the terms "radial," "radially," "lateral," and "laterally" generally mean and refer to a direction perpendicular to the central, longitudinal axis of the element(s) of the injection device described herein.

As used herein, the term "configured" refers to a size, shape, material composition, material distribution, orientation, and arrangement of one or more of at least one structure and at least one apparatus facilitating operation of one or more of the structure and the apparatus in a pre-determined way.

<FIG> illustrates a cross-sectional view of an injection device <NUM>, which may also be referred to herein as a syringe. The injection device <NUM> may comprise a barrel <NUM> extending axially along a longitudinal axis <NUM> between a distal end <NUM> and a proximal end <NUM>. The barrel <NUM> is configured to contain a medicinal fluid therein. A cannula (e.g., needle) may be coupled to the distal end <NUM> for injecting the medicinal fluid to a patient. The needle may be stacked on the distal end <NUM> or may be coupled, such as by threading, to the distal end <NUM> via an adaptor, which may be snap-fitted or glued to the distal end <NUM>.

The barrel <NUM> comprises an inner surface <NUM> defining a hollow space in which a stopper assembly according to embodiments of the present disclosure may be disposed. The inner surface <NUM> defines a maximum lateral dimension D<NUM> of the barrel <NUM>. When the barrel <NUM> is circular in cross-sectional shape, the maximum lateral dimension D<NUM> may be a maximum diameter of the inner surface <NUM> of the barrel <NUM>.

The barrel <NUM> may comprise a retaining ring <NUM> proximate to the proximal end <NUM> thereof. The retaining ring <NUM> defines a portion of the inner surface <NUM> of the barrel <NUM>. The retaining ring <NUM> further defines a minimum lateral dimension D<NUM> of the barrel <NUM>. When the barrel <NUM> is circular in cross-sectional shape, the minimum lateral dimension D<NUM> may be a minimum diameter of the inner surface <NUM> of the barrel <NUM>. As explained in further detail below, the retaining ring <NUM> may be sized and configured to inhibit passage of a stopper assembly <NUM> distally therebeyond unless a force greater than or equal to a predetermined actuating force is applied to a plunger rod <NUM>.

The barrel <NUM> may be formed of a polymeric material (e.g., plastic) or glass.

A stopper assembly <NUM> may be disposed in the barrel <NUM>. <FIG> provides an enlarged cross-sectional view of the stopper assembly <NUM> within the barrel <NUM>. The stopper assembly <NUM> may comprise a stopper <NUM> and a sealing element <NUM>.

The stopper <NUM> is shown in isolation from the injection device <NUM> in <FIG>. The stopper <NUM> has a laterally outer surface <NUM>. The laterally outer surface <NUM> defines a lateral dimension D<NUM> of the stopper <NUM>. The stopper <NUM> also has a distal surface <NUM> and a proximal surface <NUM>. When the stopper <NUM> is circular in cross-sectional shape, the lateral dimension D<NUM> of the stopper <NUM> is the diameter of the stopper <NUM>.

The laterally outer surface <NUM> may comprise a plurality (e.g., two, three, or more) of rings <NUM>. As illustrated in <FIG>, in some embodiments, the laterally outer surface <NUM> comprises a first ring <NUM> proximate to the distal surface <NUM> and a second ring <NUM> proximate to the proximal end <NUM>. The rings <NUM> define laterally outermost surfaces of the stopper <NUM> such that a remainder of the laterally outer surface <NUM> of the stopper <NUM> may be laterally recessed relative to rings <NUM>. Alternatively, the stopper <NUM> may have a constant lateral dimension D<NUM>.

The stopper <NUM> may comprise a cavity <NUM> extending into the stopper <NUM> from the distal surface <NUM>. The cavity <NUM> may comprise at least one laterally-extending groove <NUM>. The laterally-extending groove(s) <NUM> extends at least partially or entirely about a periphery of a surface of the stopper <NUM> defining the cavity <NUM>.

The stopper <NUM> may comprise another cavity <NUM> extending into the stopper <NUM> from the proximal surface <NUM>. The another cavity <NUM> may comprise a threaded surface <NUM> on a surface of the stopper <NUM> defining the another cavity <NUM>.

The stopper <NUM> may be formed of a polymeric material. By way of non-limiting example, the stopper <NUM> may be formed of an elastomeric material. The elastomeric material may be selected from the group consisting of natural rubber, synthetic rubber, thermoplastic elastomers, or combinations thereof.

The sealing element <NUM> is shown in isolation from the injection device <NUM> in <FIG>. The sealing element <NUM> may comprise a distal portion <NUM> and a proximal portion <NUM>. The sealing element <NUM> has a laterally outermost surface <NUM>. The laterally outermost surface <NUM> that may be configured to be directly engaged (e.g., in contact with) with the inner surface <NUM> of the barrel <NUM>.

The distal portion <NUM> has a maximum lateral dimension D<NUM> greater than a maximum lateral dimension D<NUM> of the proximal portion <NUM>. The distal portion <NUM> may have a hemispherical-shape as shown in the figures. However, the shape of the distal portion <NUM> is not so limited and may have another shape, such as a disc shape or a conical shape.

The distal portion <NUM> may comprise the laterally outermost surface <NUM> of the sealing element <NUM>. Accordingly, the maximum lateral dimension D<NUM> of the distal portion <NUM> may be a maximum lateral dimension of the sealing element <NUM>.

When the distal portion <NUM> and/or proximal portion <NUM> of the sealing element <NUM> are circular in cross-sectional shape, the maximum lateral dimension D<NUM> and maximum lateral dimension D<NUM> may be the maximum diameter of the distal portion <NUM> and proximal portion <NUM> respectively.

The proximal portion <NUM> may comprise at least one laterally-extending projection <NUM>. The laterally-extending projection(s) <NUM> may extend at least partially or entirely about a periphery of the proximal portion <NUM>.

The sealing element <NUM> may be formed of a polymeric material. More particularly, the polymeric material of the sealing element <NUM> is selected to be chemically inert to the medicinal fluid to be disposed within the barrel <NUM>. The polymeric material may be a rigid or semi-rigid polymer material such that axial deformation of the sealing element <NUM> is sufficiently minimal as to avoid blood reflux as described in further detail below.

When the barrel <NUM> comprises a polymeric material, the barrel <NUM> and the sealing element <NUM> may be formed from the same polymeric material. The polymeric material may be selected from the group consisting of polyolefin, polyamide, polyester, polypropylene, polystyrene, polyurethane, polycarbonate, acrylonitrile butadiene styrene, fluoropolymer, ionomer, polyacrylate, or any combination thereof.

The laterally outermost surface <NUM> of the sealing element <NUM> may be formed to have a pre-determined surface roughness. The surface roughness may be modified or otherwise selected based on the desired actuating force.

The sealing element <NUM> may be formed in an injection molding process. A surface of a mold, which is used to form the laterally outermost surface <NUM>, may be configured to impart the desired surface roughness.

In some embodiments, the laterally outermost surface <NUM> may have a surface roughness in a range extending from <NUM> to about <NUM>, inclusive, and, more preferably, in a range extending from <NUM> to about <NUM>, inclusive. Accordingly, the laterally outermost surface <NUM> may have one of a super high glossy finish (i.e., grade A-<NUM> according to the Society of Plastics Industry (SPI) standard, a high glossy finish (i.e., a grade A-<NUM> according to the SPI standard), a normal glossy finish (i.e., a grade A-<NUM> according to the SPI standard), or a fine semi-glossy finish (i.e., a grade B-<NUM> according to the SPI standard).

When the stopper <NUM> and the sealing element <NUM> are assembled together to form the stopper assembly <NUM>, a portion of the sealing element <NUM> is disposed within the cavity <NUM> of the stopper <NUM>. In particular, the proximal portion <NUM> of the sealing element <NUM> may be disposed in the cavity <NUM> of the stopper <NUM>.

When the proximal portion <NUM> of the sealing element <NUM> is disposed in the cavity <NUM> of the stopper <NUM>, the laterally-extending projection(s) <NUM> are disposed in the laterally-extending groove(s) <NUM>. Disposing the laterally-extending projection(s) <NUM> of the sealing element <NUM> in the laterally-extending groove(s) <NUM> of the stopper <NUM> provides a coupling mechanism between the sealing element <NUM> and the stopper <NUM>. Thus, when the stopper assembly <NUM> is displaced within the barrel <NUM> in operation, the sealing element <NUM> and the stopper <NUM> remain coupled together.

When the stopper assembly <NUM> is disposed in the barrel <NUM>, the laterally outer surface <NUM> of the stopper <NUM> is directly engaged with the inner surface <NUM> of the barrel <NUM>.

The lateral dimension D<NUM> of the stopper <NUM> is greater than the maximum lateral dimension D<NUM> and the minimum lateral dimension D<NUM>. Due to the dimensions of the stopper <NUM> relative to the dimensions of the barrel <NUM>, the stopper <NUM> is laterally compressed within the barrel <NUM> when the stopper assembly <NUM> is disposed therein. The lateral compression of the stopper <NUM> exerts a compressive force on the proximal portion <NUM> of the sealing element <NUM> disposed in the cavity <NUM> of the stopper <NUM>. In addition to or as an alternative to providing the laterally-extending grooves <NUM> and projections <NUM>, the laterally compressive force of the stopper <NUM> on the sealing element <NUM> provides a coupling mechanism between the sealing element <NUM> and the stopper <NUM>. Thus, when the stopper assembly <NUM> is displaced within the barrel <NUM> in operation, the sealing element <NUM> and the stopper <NUM> remain coupled together.

When the stopper assembly <NUM> is disposed in the barrel <NUM>, the sealing element <NUM> is located axially distal relative to the stopper <NUM>. By disposing the sealing element <NUM> axially distal relative to the stopper <NUM>, the sealing element <NUM> is in contact with the medicinal fluid also disposed within the barrel <NUM>. Thus, the sealing element <NUM> sealingly isolates the stopper <NUM> from the medicinal fluid. As a result of the isolation of the stopper <NUM> from the medicinal fluid, the potency of the medicinal fluid remains unchanged when the medicinal fluid is stored within the barrel <NUM> over time.

When the stopper assembly <NUM> is disposed in the barrel <NUM>, the laterally outermost surface <NUM> of the sealing element <NUM> may be directly engaged with the inner surface <NUM> of the barrel <NUM>. Further, during storage/transport of a prefilled syringe, the proximal portion <NUM> sealing element <NUM> may initially abut against a distal part of the retaining ring <NUM>.

The maximum lateral dimension D<NUM> of the inner surface <NUM> of the barrel <NUM> may be less than the maximum lateral dimension D<NUM> of the distal portion <NUM> of the sealing element <NUM>. Accordingly, when the stopper assembly <NUM> is disposed in the barrel <NUM>, the distal portion <NUM> of the sealing element <NUM> is laterally compressed. Lateral compression of the sealing element <NUM> forms a fluid tight interface between the sealing element <NUM> and the inner surface <NUM> of the barrel <NUM>. Thus, in addition to the axial location of the sealing element <NUM> relative to the stopper <NUM>, the dimension of the sealing element <NUM> sealingly isolates the stopper <NUM> from the medicinal fluid. In other words, the medicinal fluid disposed in the barrel <NUM> is in contact with the sealing element <NUM> and cannot contact the stopper <NUM> due to the fluid tight interface between the sealing element <NUM> and the inner surface <NUM> of the barrel <NUM>. As a result of the isolation of the stopper <NUM> from the medicinal fluid, the potency of the medicinal fluid remains unchanged when the medicinal fluid is stored within the barrel <NUM> over time.

The stopper assembly <NUM> is initially disposed in the storage position within the barrel <NUM>. In the storage position, the stopper assembly <NUM> is located axially distal relative to the retaining ring <NUM>. As previously described herein, the maximum lateral dimension D<NUM> of the sealing element <NUM> and the lateral dimension D<NUM> of the stopper <NUM> are greater than the minimum lateral dimension D<NUM> of the retaining ring <NUM>. The sealing element <NUM> and the stopper <NUM> may be compressed to allow passage of the stopper assembly <NUM> between and distally beyond the retaining ring <NUM>.

The injection device <NUM> may further comprise a plunger rod <NUM>. The plunger rod <NUM> has a distal end <NUM> and a proximal end <NUM>. The distal end <NUM> of the plunger rod <NUM> may be disposed in the barrel <NUM>.

The distal end <NUM> of the plunger rod <NUM> may be coupled to the stopper assembly <NUM>. The distal end <NUM> of the plunger rod <NUM> may comprise a threaded surface <NUM>. As previously described, the another cavity <NUM> of the stopper <NUM> may comprise the threaded surface <NUM>, which is configured to couple the plunger rod <NUM> to the stopper <NUM>.

The plunger rod <NUM> may comprise a flange <NUM>. When the plunger rod <NUM> is coupled to the stopper <NUM>, the stopper <NUM> may be disposed between the flange <NUM> of the plunger rod <NUM> and the sealing element <NUM>.

In operation, the stopper assembly <NUM> is axially displaced in a distal direction from a storage position to a use position. <FIG> illustrates the stopper assembly <NUM> in the use position. As previously described, the stopper assembly <NUM> is located axially distal relative to the retaining ring <NUM> in the storage position. To axially displace the stopper assembly <NUM> and to administer the medicinal fluid to a patient, a force is applied by a user on the proximal end <NUM> of the plunger rod <NUM>. The applied force must be greater than or equal to a predetermined actuating force. The maximum lateral dimension D<NUM> of the sealing element <NUM>, the maximum lateral dimension D<NUM> of the stopper <NUM>, the surface roughness of the laterally outermost surface <NUM> of the sealing element <NUM>, and/or the material composition of the sealing element <NUM> and/or stopper <NUM> may be selectively tailored to obtain a desired, predetermined actuating force. While the stopper assembly <NUM> is axially displaced in a distal direction within the barrel <NUM>, the stopper <NUM> remains sealingly isolated from the medicinal fluid by the sealing element <NUM>.

The plunger rod <NUM> may continue to be axially displaced (e.g., distally displaced) until the sealing element <NUM> abuts against a distal end of the inner surface <NUM> of the barrel <NUM>. For injection devices lacking the sealing element <NUM>, a syringe-induced blood reflux may occur. Syringe-induced blood reflux refers to the drawing back of blood into the injection device caused by the generation of a vacuum within the barrel from the compression and subsequent rebound of a rubber stopper against the distal end of the inner surface of the barrel. The sealing element <NUM>, which is made of a rigid or semi-rigid polymeric material as described herein, does not axially compress and otherwise prevents such compression and subsequent rebound of the stopper <NUM> because the stopper <NUM> does not abut against the distal end of the inner surface <NUM> of the barrel <NUM>. Thus, a further advantage of the stopper assembly <NUM> is the avoidance of blood reflux. It is to be understood that the stopper assembly <NUM> of the invention may also be used in reconstitution device.

<FIG> illustrates a cross-sectional view of an injection device <NUM>. The injection device <NUM> may comprise a barrel <NUM> extending axially along a longitudinal axis <NUM> between a distal end <NUM> and a proximal end <NUM>. The barrel <NUM> is configured to contain a medicinal fluid therein. A cannula (e.g., needle) may be coupled to the distal end <NUM> for administering the medicinal fluid to a patient.

Like the barrel <NUM>, the barrel <NUM> may comprise at least one retaining ring. As best illustrated in <FIG>, the barrel <NUM> comprises a retaining ring <NUM> and another retaining ring <NUM> located proximate to the proximal end <NUM> thereof. The retaining ring <NUM> is located proximal relative to the retaining ring <NUM>. The retaining rings <NUM>, <NUM> are axially spaced apart by an axial distance D<NUM>.

The retaining rings <NUM>, <NUM> define a portion of the inner surface <NUM> of the barrel <NUM>. The retaining rings <NUM>, <NUM> further defines a minimum lateral dimension D<NUM>, D<NUM> of the barrel <NUM>. When the barrel <NUM> is circular in cross-sectional shape, the minimum lateral dimension D<NUM>, D<NUM> may be minimum diameters of the inner surface <NUM> of the barrel <NUM>.

As explained in further detail below, the retaining rings <NUM>, <NUM> may be sized and configured to inhibit passage of a stopper assembly <NUM> distally therebeyond unless a force greater than or equal to a predetermined actuating force is applied to a plunger rod <NUM>.

The barrel <NUM> may be formed from the same materials previously described with reference to barrel <NUM>.

A stopper assembly <NUM> may be disposed in the barrel <NUM>. <FIG> provides an enlarged cross-sectional view of the stopper assembly <NUM> within the barrel <NUM>. The stopper assembly <NUM> may comprise the stopper <NUM> previously described with reference to <FIG> and a sealing element <NUM>.

While the stopper assembly <NUM> is described primarily with reference to its disposal within the barrel <NUM>, the stopper assembly <NUM> may also be used in combination with barrel <NUM>.

The sealing element <NUM> is shown in isolation from the injection device <NUM> in <FIG>. The sealing element <NUM> may comprise a distal portion <NUM> and a proximal portion <NUM>. The sealing element <NUM> has a laterally outermost surface <NUM>.

The distal portion <NUM> has a maximum lateral dimension D<NUM> greater than a maximum lateral dimension D<NUM> of the proximal portion <NUM>. The distal portion <NUM> may be disc-shaped. Accordingly, a distal surface of the distal portion <NUM> may be planar. Alternatively, the distal surface of the distal portion <NUM> may be curved (e.g., hemispherical) or conical.

The sealing element <NUM> may be formed of a polymeric material such as the polymeric materials previously described with reference to sealing element <NUM>.

When the proximal portion <NUM> of the sealing element <NUM> is disposed in the cavity <NUM> of the stopper <NUM>, the laterally-extending projection(s) <NUM> are disposed in the laterally-extending groove(s) <NUM>. Disposing the laterally-extending projection(s) <NUM> of the sealing element <NUM> in the laterally-extending groove(s) <NUM> of the stopper <NUM> provides a coupling mechanism between the sealing element <NUM> and the stopper <NUM>. Thus, when the stopper assembly <NUM> is axially displaced within the barrel <NUM> in operation, the sealing element <NUM> and the stopper <NUM> remain coupled together.

The lateral dimension D130 of the stopper <NUM> may be greater than the maximum lateral dimension D208 and the minimum lateral dimension D203, <NUM>. Due to the dimensions of the stopper <NUM> relative to the dimensions of the barrel <NUM>, the stopper <NUM> is laterally compressed within the barrel <NUM> when the stopper assembly <NUM> is disposed therein. The lateral compression of the stopper <NUM> exerts a compressive force on the proximal portion <NUM> of the sealing element <NUM> disposed in the cavity <NUM> of the stopper <NUM>. In addition to or as an alternative to providing the laterally-extending grooves <NUM> and projections <NUM>, the laterally compressive force of the stopper <NUM> on the sealing element <NUM> provides a coupling mechanism between the sealing element <NUM> and the stopper <NUM>. Thus, when the stopper assembly <NUM> is displaced within the barrel <NUM>, the sealing element <NUM> and the stopper <NUM> remain coupled together.

When the stopper assembly <NUM> is disposed in the barrel <NUM>, the sealing element <NUM> is located axially distal relative to the stopper <NUM>. More particularly, the distal portion <NUM> of the sealing element <NUM> may abut against the distal surface <NUM> of the stopper <NUM>. By disposing the sealing element <NUM> axially distal relative to the stopper <NUM>, the sealing element <NUM> is in contact with the medicinal fluid also disposed within the barrel <NUM>. Thus, the stopper <NUM> is sealingly isolated from the medicinal fluid by the sealing element <NUM>.

In some embodiments, when the stopper assembly <NUM> is disposed in the barrel <NUM>, the laterally outermost surface <NUM> of the sealing element <NUM> may be disengaged from the inner surface <NUM> of the barrel <NUM>. The maximum lateral dimension D<NUM> of the inner surface <NUM> of the barrel <NUM> may be greater than the maximum lateral dimension D<NUM> of the proximal portion <NUM> of the sealing element <NUM>. By dimensioning the maximum lateral dimension D<NUM> of the proximal portion <NUM> of the sealing element <NUM> to be less than the lateral dimension D<NUM> of the inner surface <NUM> of the barrel <NUM>, the surface roughness of the laterally outermost surface <NUM> is irrelevant to the predetermined actuating force that must be applied to the plunger rod <NUM> to axially displace the stopper assembly <NUM>.

In other embodiments, when the stopper assembly <NUM> is disposed in the barrel <NUM>, the laterally outermost surface <NUM> of the sealing element <NUM> may be directly engaged from the inner surface <NUM> of the barrel <NUM>. Thus, the maximum lateral dimension D<NUM> of the proximal portion <NUM> may be selected as previously described with reference to the sealing element <NUM>.

In either embodiment, the sealing element <NUM> may abut against the retaining ring <NUM> in the storage position such that the sealing element <NUM> is located proximal relative to the retaining ring <NUM> and distal relative to the retaining ring <NUM>.

The injection device <NUM> may further comprise the plunger rod <NUM>, as previously described with reference to <FIG>. The distal end <NUM> of the plunger rod <NUM> may be disposed in the barrel <NUM>. The distal end <NUM> of the plunger rod <NUM> may be coupled to the stopper assembly <NUM>. Accordingly, the stopper <NUM> may be disposed between the flange <NUM> of the plunger rod <NUM> and the sealing element <NUM>.

When the stopper assembly <NUM> is disposed in the storage position in the barrel <NUM>, each of the sealing element <NUM>, the stopper <NUM>, and the flange <NUM> of the plunger <NUM> may be located axially between the retaining rings <NUM>, <NUM>. The sealing element <NUM> may abut against the another retaining ring <NUM>.

Further, the axial distance D<NUM> may be selected such that the flange <NUM> of the plunger rod <NUM> and the distal portion <NUM> of the sealing element <NUM> apply an axially compressive force on the stopper <NUM>. The stopper <NUM> may apply an opposing axial force on the flange <NUM> of the plunger rod <NUM> and the distal portion <NUM> of the sealing element <NUM>.

This opposing force applied by the stopper <NUM> forms a fluid tight interface between the sealing element <NUM> and the another retaining ring <NUM> of the barrel <NUM>. Thus, in addition to the axial location of the sealing element <NUM> relative to the stopper <NUM>, the dimension of the sealing element <NUM> relative to the dimension of the another retaining ring <NUM> and the force of the stopper <NUM> sealingly isolates the stopper <NUM> from the medicinal fluid. In other words, the medicinal fluid disposed in the barrel <NUM> is in contact with the sealing element <NUM> and cannot contact the stopper <NUM> due to the fluid tight interface between the sealing element <NUM> and the another retaining ring <NUM> when the stopper assembly <NUM> is in the storage position. As a result of the isolation of the stopper <NUM> from the medicinal fluid, the potency of the medicinal fluid remains unchanged when the medicinal fluid is stored within the barrel <NUM> over time.

As previously described herein, the maximum lateral dimension D<NUM> of the sealing element <NUM> and the lateral dimension D<NUM> of the stopper <NUM> are greater than the minimum lateral dimension D<NUM> of the retaining ring <NUM>. The sealing element <NUM> and the stopper <NUM> may be compressed to allow passage of the stopper assembly <NUM> between and distally beyond the retaining ring <NUM>.

In operation, typically during injection, the stopper assembly <NUM> is axially displaced from the storage position to the use position. <FIG> illustrates the stopper assembly <NUM> in the storage position. As previously described, the stopper assembly <NUM> is located axially proximal relative to the retaining ring <NUM> in the storage position. To axially displace the stopper assembly <NUM> and to administer the medicinal fluid to a patient, a force is applied by a user on the proximal end <NUM> of the plunger rod <NUM>. The applied force must be greater than or equal to a predetermined actuating force. One or more of the maximum lateral dimension D<NUM> of the sealing element <NUM>, the lateral dimension D<NUM> of the stopper <NUM>, and the minimum lateral dimension D<NUM> of the retaining ring may be selected to obtain a desired, predetermined actuating force.

While the stopper assembly <NUM> is axially displaced within the barrel <NUM> (e.g., in a use position), the stopper <NUM> may remain sealingly isolated from the medicinal fluid or may contact some medicinal fluid depending on the maximum lateral dimension D<NUM> of the sealing element <NUM> as previously described herein. Even if the medicinal fluid contacts the stopper <NUM> in the use position, there is insufficient time during the operation of the injection device <NUM> for the medicinal fluid and the stopper <NUM> to affect the potency of the drug.

The plunger rod <NUM> may continue to be axially displaced until the sealing element <NUM> abuts against a distal end of the inner surface <NUM> of the barrel <NUM>. For injection devices lacking the sealing element <NUM>, a syringe-induced blood reflux may occur. The presence of the sealing element <NUM> and the material composition of the sealing element <NUM> prevents such compression and subsequent rebound of the stopper <NUM> because the stopper <NUM> does not abut against the distal end of the inner surface <NUM> of the barrel <NUM>. Thus, a further advantage of the stopper assembly <NUM> is the avoidance of blood reflux.

Claim 1:
An injection device (<NUM>) comprising:
a barrel (<NUM>) extending axially between a distal end (<NUM>) and a proximal end (<NUM>), the barrel (<NUM>) configured to contain a medicinal fluid, the barrel (<NUM>) comprising a first retaining ring (<NUM>) proximate to the proximal end (<NUM>);
a plunger rod (<NUM>) having a distal end (<NUM>) and a proximal end (<NUM>), the distal end (<NUM>) of the plunger rod (<NUM>) disposed in the barrel (<NUM>); and
a stopper assembly (<NUM>) disposed in the barrel (<NUM>), the stopper assembly comprising:
a stopper (<NUM>) having a laterally outermost surface (<NUM>) configured to be directly engaged with an inner surface (<NUM>) of the barrel (<NUM>); and
a sealing element (<NUM>) coupled to and axially distal relative to the stopper (<NUM>) in the barrel (<NUM>), the sealing element (<NUM>) having a laterally outermost surface (<NUM>) configured to be directly engaged with the inner surface (<NUM>) of the barrel (<NUM>) and to sealingly isolate the stopper (<NUM>) from the medicinal fluid in the barrel (<NUM>)
the injection device characterized in that:
the barrel (<NUM>) comprises a second retaining ring (<NUM>) located proximate to the proximal end (<NUM>) of the barrel (<NUM>), the first retaining ring (<NUM>) axially spaced apart from and located proximal relative to the second retaining ring (<NUM>), the first and second retaining rings (<NUM>, <NUM>) defining a minimum lateral dimension (D<NUM>, D<NUM>) of the inner surface (<NUM>) of the barrel (<NUM>); and
wherein each of the sealing element (<NUM>), the stopper (<NUM>), and a flange (<NUM>) of the plunger rod (<NUM>) is located between the first and second retaining rings (<NUM>, <NUM>) in the storage position such that the stopper (<NUM>) is axially compressed between the sealing element (<NUM>) and the flange (<NUM>) of the plunger (<NUM>).