Dual chamber internal by-pass syringe assembly

Abstract: A syringe assembly comprising an elongated hollow tubular barrel having a discharge opening at one end and a radially inwardly directed circumferentially extending rib in the inner peripheral surface of said barrel divides the barrel into a first medicament chamber on one side of said rib and a second diluent chamber on the opposite side of said rib. A by-pass stopper engages interiorly of the barrel and has a circumferentially extending exterior sealing surface of a predetermined diameter greater then the diameter of the rib to provide a seal between the chambers when engaged therewith. The by-pass stopper has at least one axially extending flow path on at least one side of the sealing surface providing fluid communication between the chambers when the by-pass stopper is displaced axially relative to the rib and the rib is aligned with the flow passage way.

Description: FIELD OF THE INVENTION The present invention relates to improvements in syringe assemblies. More particularly the invention relates to improvements in so called single barrel, two compartment syringes wherein two components of a medicament, such as two liquids or a solid and a liquid can be packaged in the syringe each in its own sealed environment and wherein the components can be mixed when desired so that they can be dispensed. BACKGROUND OF THE INVENTION The use of syringes to administer medicaments to patients has long been recognized as an effective method of treatment. In some instances, where the medicaments are in powder form and need to be reconstituted by the addition of distilled water or other liquids, administration of the medicament involves a number of steps and the use of multiple syringes. For example, when the components of a medicament are to be mixed prior to administration, in some instances the procedure involves (1) insertion of a syringe into a first container having the first component, (2) withdrawing the first component into the syringe, (3) withdrawing the syringe from the first container, (4) insertion of the syringe into a second container having a second component, (5) discharge of the first medicament into the second container, (6) mixing the two components within the second container, (7) withdrawing the mixed medicament, and (8) administering the medicament to the patient. It is noted that it would be a great advantage to the art if many of these steps can be combined or avoided all together. Methods have been proposed to avoid the above described difficulties through use of dual chamber syringes which employ an external by-pass. Several of these are manufactured for use in packaged drugs. The drugs typically are liquids contained in each chamber of the dual chamber syringe, whereby the two liquids are mixed prior to administration. These dual chamber syringes have been used for packaging lyophilized drugs that are sublimated in the syringe. The dual chamber syringe's use of an external by-pass, however, can cause mixing and surging problems. Some drugs remain in the external by-pass and can contaminate exposed areas of the syringe. Also, if the medicament is toxic or corrosive, the preparer and user of the syringe is put at an undesirable risk. Another known design vents to permit passive mixing of a liquid and a solid in one chamber of the syringe. This design employs a central plunger having a burstable diaphragm which is designed to create turbulence upon breaking loose of the diaphragm and activation of the stopper to enhance mixing of the materials in the tube chambers. A problem with this system is the problem of particulates created when the diaphragm bursts which may be a hazard to the patient if injected with the medicament. Another internal stopper design includes dual compartment vials held in place by a constriction in the body of the vial. In this instance, the stopper serves as a barrier and is dislodged after activation to permit the two materials in the dual compartments to co-mingle and combine. Another known syringe device is a combination syringe and vial. The stopper closing the vial is held in place by a constriction and is vented to permit introduction of a liquid into the vial. The stopper serves as a plunger when the contents of the syringe are expelled. Other attempts to achieve an adequate design have used modifications of the plunger rod in conjunction with a syringe. The syringe is activated by threading the plunger rod toward the proximal end which breaks the by-pass stopper loose and moves it slowly past the external by-pass. The plunger rod only moves freely as in a traditional syringe after the last male thread on the plunger rod passes the last female thread in the finger grip. Document DE-A-1566644 upon which the preamble of claim 1 is based, describes a two compartment syringe comprising an elongated hollow tubular barrel having a discharge opening at one end, a radially inwardly directed circumferentially extending rib in the inner peripheral surface of said barrel and an inner cylinder comprising a valve extending axially through the center of the inner cylinder. The valve allows fluid communication between the chambers when by actuating a plunger the pressure in one of the chambers exceeds the pressure in the other chamber. A circumferentially extending groove of the inner cylinder in correspondence with said rib serves to prevent the inner cylinder from being displaced axially to the rib while fluid flows through the valve. Document EP-A-0415867 describes a syringe for unique use. The syringe comprises an elongated hollow tubular barrel having a discharge opening at one end, a radially inwardly directed circumferentially extending rib in the inner peripheral surface of said barrel and a moving body movable in the barrel. The moving body comprises a flexible circular edge which allows the body to pass the rib in the direction of the discharge opening when a plunger is actuated. After having passed the rib, the flexible edge prevents the body to pass the rib in the opposite direction. If the plunger is then moved to aspire liquid the body and the rib form a sealing to prevent the reuse of the syringe. Although various syringes are known, it would be a great advance in the art if a simple, effective dual chamber syringe could be provided which would overcome the deficiencies of those designs presently known in the industry. SUMMARY OF THE INVENTION With the above in mind, it is an object of the present invention to provide an improved single barrel, two compartment syringe for storing and dispensing plural component medicaments. This is achieved by a syringe assembly including the features of claim 1. The syringe assembly includes an elongated hollow syringe barrel. The forward end of the syringe barrel mounts a conventional double ended needle and hub assembly and is normally in an unarmed position so that the discharge opening is sealed. The opposite end of the syringe is open to receive a plunger and plunger rod moveable axially in the syringe barrel to displace the contents of the syringe when it is desired in the manner described hereafter. The syringe barrel is divided into a medicament chamber and diluent chamber by a by-pass stopper which has a circumferentially extending sealing surface which normally engages an internal rib in the syringe barrel to hermetically seal the chambers from one another an a plurality of axially extending, radially outwardly projecting ribs on the proximal side or both sides of the sealing surface which are circumferentially spaced to define flow channels. Accordingly, in the normal centered position of the by-pass stopper, the chambers are sealed from on another and this is the position of the parts prior to use. It has been found that this arrangement provides an effective seal guaranteeing a long shelf life for the syringe and insuring stability of the components stored therein. When it is desired to reconstitute the medicament, displacement of the discharge plunger toward the discharge end of the syringe increases the force of the diluent on the back face of the by-pass stopper, thereby displacing the by-pass stopper a predetermined small distance to a point where the internal rib separating the chambers engages the outer portion of the projections, thereby defining diluent channels or passageways between the projections permitting flow of diluent from the diluent chamber to the powder chamber. The by-pass stopper remains in this position because the frictional resistance between the syringe barrel rib and the projections is greater than the diluent fluid pressure on the by-pass stopper. This permits expelling all of the diluent from the diluent compartment until the discharge plunger abuts the rear face of the by-pass stopper. In this position all of the diluent has been transferred. The user then shakes the syringe to thoroughly mix the components of the medicament, aspirates the syringe to remove any air and now the reconstituted medicament is ready for delivery to the patient. The syringe assembly of the present invention is of simplified construction which is easy and economical to manufacture since it is comprised of relatively few components. The single barrel, two compartment syringe system of the present invention insures hermetic sealing of the components thereby providing a long and stable shelf life. The specific details and arrangement of the assembly insure complete mixing of all of the components which is important in maintaining the efficacy of a given medicament. Still another object of the present invention is to provide a single barrel two compartment syringe characterized by novel features of construction and arrangement wherein the barrel has virtually no surface protrusions and is therefore more adaptable for labeling as contrasted with the prior art external by-pass devices which make labeling much more difficult. Still another object of the present invention is to provide a relatively simple design which is easy and economical to manufacture and assemble and is extremely effective in not only providing a seal between the chambers and guarantee a relatively long shelf life for two component medicaments, but also a design wherein the diluent can be completely evacuated from behind the by-pass stopper and fully mixed with the powder medicament before injection. It is a further object of the present invention to provide a method for dispersing two components to be combined prior to discharge using a syringe. This object is achieved by the features according to claim 4. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, wherein; Fig. 1 is a plan view of a two compartment syringe assembling in accordance with the present invention; Fig. 2 is an enlarged, fragmentary transverse sectional elevational view taken on lines 2-2 of Fig. 1, showing material details of the two compartment syringe assembly prior to use; Fig. 3 is an enlarged, isometric view of one embodiment of by-pass stopper of this invention; Fig. 4 is an enlarged, side elevational view of the by-pass stopper. Fig. 5 is a right hand side elevational view of the by-pass stopper shown in Fig. 4. Fig. 6 is an enlarged, stepped sectional view taken on step line 6-6 of Fig. 2, showing details of the internal by-pass stopper engaging the sealing ring of the syringe barrel; Figs. 7a-7e illustrate the sequential functions of the syringe assembly and associated components during a medicament reconstituting cycle; Fig. 8 is a side, elevational view of a modified embodiment of the by-pass stopper of this invention; Fig. 9 is a right hand, elevational view of the by-pass stopper shown in Fig. 8; Fig. 10 is an enlarged, isometric view of the by-pass stopper shown in Fig. 8; Fig. 11a is a plan view of the syringe of the present invention and the alternative embodiment of by-pass stopper; Figs. 11b-11c are the sequential views of the components of a syringe embodying the modified embodiment by-pass stopper during a medicament reconstituting cycle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and particularly to Figs. 1-7c, there is shown a syringe assembly in accordance with the present invention which is generally designated by the numeral 10 . The syringe assembly is a single barrel, two compartment syringe which as illustrated in Figs. 1 and 2 comprises an elongated hollow syringe band or body 12 usually made of glass open at its inner end as at 14 and having a reduced finish 16 at its forward end. The discharge opening 18 is normally sealed by a conventional circular disk-type seal 20 made of a flexible, puncturable material, such as rubber, supported in place over the discharge opening 18 by an aluminum seal 22 which is crimped over the finish to hold the seal 20 in place. The aluminum seal 22 has a central opening 22 in its end face to permit puncturing the disk seal 20 when it is desired to activate the syringe and dispense the contents. The assembly further includes a cup shaped needle hub 30 which mounts double ended needle 32 . The outer end 32 a of the needle 32 is covered by a needle sheath 38 and is normally seated on the discharge end of the syringe barrel 12 in the position shown in Fig. 2 with the inner sharp end 32 b of the needle 32 spaced from the disk seal 20 . The needle hub 30 has a pair of spaced circumferentially extending ribs 34 which engage in a groove 36 in the aluminum seal or cap 22 holding the needle hub 30 in an unarmed position, as shown in Fig. 2 or an armed position as shown in Fig. 7a. The syringe barrel 12 , in the present instance, is divided into a powder medicament compartment C p and a diluent compartment C d by a by-pass stopper 40 frictionally held by means of a circumferentially extending inwardly directed bead 26 formed in the syringe body 12 . The by-pass stopper seals the compartments C p and C d from one another as explained in more detail hereafter. The stopper is made of an elastomeric material, such as a rubber compound conventionally used for forming plunger tips and seals in syringes, and, as will be understood by one of ordinary skill in the art, made from a formulation which the pharmaceutical manufacturer knows is compatible with the medicament and diluent. The syringe assembly further includes a plunger rod 42 which threadedly mounts a discharge plunger 44 which engages in the inner end of the syringe barrel. A conventional finger grip 29 is mounted on the inner end of the syringe barrel and defines a stop or limit for the discharge plunger 44 . Considering now briefly readying the syringe for use, the needle cup 30 is pushed inwardly causing the inner sharp end 32 a of needle 32 to pierce stopper 20 , providing an air path between medicament chamber C p and ambient environment. The plunger rod 42 may then be pressed inwardly to displace the discharge plunger 44 forwardly to create a displacement force on the rear face of the by-pass stopper 40 to displace it slightly to the position shown in Fig. A and create flow channels permitting flow of diluent into the powder medicament chamber C p . After all of the diluent has been evacuated, the contents are mixed in the forward chamber C p and the medicament product is ready for injection. The contents can be dispensed by forward movement of the discharge plunger in the manner shown in Figs. 7d and 7e until the contents have been fully charged. When the medicament has been fully discharged the plunger rod 42 terminal end sets in the finger grip 30 the needle cup 30 may then be removed from the syringe body and inserted in the plunger rod 42 , providing a safe throw away package. Considering now more specifically the by-pass stopper 40 , the stopper as best shown in Figs. 3 and Figs. 4-6 inclusive comprises a series of axially extending, circumferentially spaced projections 50 which in the present instance are arranged in two axially spaced rows R 1 and R 2 to define a generally cylindrical sealing surface 46 between the rows R 1 and R 2 of projections. The sealing surface 46 is preferably of a diameter D 1 greater then the diameter D 2 of the radially inwardly circumferentially extending bead 26 defining the separation point between the powder and diluent chambers. The diameter D 1 of the sealing surface 46 is also preferably less then the diameters D 3 and D 4 of the powder and diluent chambers C p and C d which in the preferred form are of the same diameter. A circular trace through the apex of the ribs is of a diameter D 5 greater then the diameter of the D 2 of circumferential bead 26 so that when the by-pass stopper 40 is displaced to the position shown in Fig. 7a during the initial activation of the discharge plunger, flow passageways P form between the ribs 50 as shown in Fig. 7a to permit diluent to flow from the diluent compartment C p to the powder compartment C p . Further, the diametral relationships and materials of the by-pass stopper 40 and barrel 12 are such that the frictional force holding the by-pass stopper in the position in Fig. 7a is greater then the hydraulic force on the back face of the by-pass stopper 40 during the displacement stroke of the discharge plunger 44 . In this manner, all of the diluent is evacuated to the powder chamber C p with the by-pass stopper in a static position until the discharge plunger 44 abuts the rear face of the by-pass stopper 40 in the manner shown in Fig. 7c. The by-pass stopper 40 is then pushed beyond the circumferential bead 26 during the medicament discharged stroke and rides in front of the discharge plunger 44 in the manner shown in Fig. 7d and 7e. There is shown in Figs. 8-10 inclusive another embodiment of by-pass stopper 60 in accordance with the present invention. This by-pass stopper 60 functions in the same manner to the by-pass stopper previously described in that it provides a seal between the powder chamber and diluent chamber C p and C d and upon displacement creates flow channels for mixing the diluent and powder medicament in the forward chamber. In the present instance, the by-pass stopper has a generally cylindrical forward or nose portion 62 , the outer periphery of which defines a sealing surface 64 having a diameter D 8 slightly greater then the diameter D 2 of the circumferentially extending inwardly directed bead 26 . A single row R 4 of circumferentially spaced, axially extending ribs 66 are provided on the outer peripheral surface which are of generally arcuate shape in cross section as shown in Fig. 9 and define therebetween a series of axial flow passages P f . The sealing surface 64 is preferably of a diameter slightly less than the diameter of the powder medicament and the diluent chambers C p and C d to facilitate flow between the chambers when the by-pass stopper 60 is initially displaced and also to facilitate retention of the by-pass stopper 60 in the partially displaced position shown in Figs. 11a, 11b and 11c. In the present instance, the front face 68 of the by-pass stopper 60 is conically shaped and forms an angle of about 15° to the axis of the plunger. The by-pass stopper 60 is particularly suited for very fine powder medicament products which tend to produce a frosted look to the stopper when the double row by-pass stopper 40 is used with fine powder medicaments. The fine powder tends to infiltrate between the projections 50 in the spaces P formed between the by-pass stopper sealing surface 46 and the inner wall of the chamber C p creating an undesirable frosted look, which the user may attribute to diluent leakage. The modified by-pass stopper 60 tends to keep powder or lyophilization dust out of the region between the stopper and the barrel. Even though particular embodiments of the present invention have been illustrated and described herein, it is not intended to limit the invention and changes and modifications may be made therein with the scope of the following claims.

Claims: A syringe assembly comprising: An elongated hollow tubular barrel (12) having a discharge opening (18) at a distal end; and means defining a radially inwardly directed circumferentially extending rib (26) in the inner peripheral surface of said barrel (12) dividing said barrel (12) into a first medicament chamber (C p ) on one side of said rib (26) and a second diluent chamber (C d ) on the opposite side of said rib (26); a by-pass stopper (40; 60) engageable interiorly of said barrel (12) having a circumferentially extending exterior sealing surface (46; 64) of a predetermined diameter (D 1 ; D 8 ) greater than the diameter (D 2 ) of the rib (26) to provide a seal between said chambers (C p , C d ) when engaged with the rib (26); characterized in that the by-pass stopper (40; 60) comprises axially extending, circumferentially spaced projections (50; 66) defining at least one axially extending flow path on at least the proximal side of said sealing surface (46) providing fluid communication between said chambers (C p , C d ) when said stopper is displaced axially relative to the rib (26). The syringe assembly of Claim 1, wherein said by-pass stopper (40) includes projections (50) circumferentially spaced on both sides of a central portion, said central portion circumferentially engaging said sealing rib (26). The syringe assembly of Claim 1, wherein said by-pass stopper (60) includes a plurality of projections (66) circumferentially spaced thereon only on the proximal side of the by-pass stopper (60). A method for mixing two components to be combined prior to discharge using a syringe, comprising the steps of: providing a syringe (10) including a liquid in a proximal chamber (C d ) and a medicament mixable with said liquid in a distal chamber (C p ) and including a body having a radially inwardly directed internal sealing rib (26) to define said distal and proximal chambers (C p , C d ) and a by-pass stopper (40; 60) having a portion (46; 64) sealingly separating said chambers, and a plurality of axially extending, circumferentially spaced projections on at least one said of said sealing portion (46; 64) defining by-pass channels; actuating a plunger rod (42) for moving said by-pass stopper (40; 60) axially to displace the sealing portion (46; 64) from the rib (26) to permit flow of liquid through said by-pass channels from said proximal chamber (C d ) to said distal chamber (C p ) for mixing said medicament and said liquid. The method of Claim 4 wherein said by-pass (40) stopper includes projections (50) circumferentially spaced on both sides of a cencral portion, said central portion circumferentially engaging said sealing rib (26) to provide a sealing engagement therebetween. The method of Claim 4 wherein said by-pass stopper (60) includes a plurality of projections (66) circumferentially spaced thereon only on the proximal side of the by-pass stopper (40). The method of Claim 4 wherein said internal by-pass stopper (40) includes a cone shaped distal end (68) facing said distal chamber (C p ). The method of Claim 4 which further includes a needle hub assembly (30) for mounting a needle (32) on said device.

Inventors: MICHAELS THOMAS M, MICHAELS, THOMAS M.
Applicants: SCHOTT PARENTA SYSTEMS INC, SCHOTT PARENTA SYSTEMS, INC.
Application year: 1996
Main classification: A61M5
IPC codes: A61M5