WO2000053244A1

WO2000053244A1 - Two compartment syringe

Info

Publication number: WO2000053244A1
Application number: PCT/GB2000/000169
Authority: WO
Inventors: Christopher John Clarke; John Targell; Alastair Douglas Wright
Original assignee: Nmt Group Plc
Priority date: 1999-03-09
Filing date: 2000-01-14
Publication date: 2000-09-14
Also published as: GB9905258D0; AU3066000A

Abstract

A syringe comprises a barrel having a forward end adapted to be fitted with a needle assembly, a plunger slidable within the barrel and having a plunger seal at its forward end, and an annular chamber defined between the plunger and a wall surrounding the plunger. The interior of the barrel and the annular chamber may be pre-filled with two components which are to be admixed before administration. Retraction of the plunger is effective to establish communication between the interior of the barrel and the annular chamber to allow the pre-filled components to admix within the barrel interior. In a modification, only the annular chamber is pre-filled with a drug to be administered, the drug being transferred to a location forwardly of the plunger seal in response to plunger reaction in readiness for administration by depression of the plunger.

Description

TWO COMPARTMENT SYRINGE

This invention concerns a syringe for use with a hypodermic needle and, more particularly, one of the kind which may be pre-filled with at least one component, e.g. two components in separate compartments for admixture before administration.

Certain drugs, once in solution, have a limited shelf life requiring them to be prepared at or close to the point of use from their solid and liquid components. This is most conveniently accomplished by the provision of a pre-filled syringe which eliminates need for dispensing and measuring precise quantities from bulk supplies.

According to the present invention there is provided a syringe comprising a barrel having a forward end adapted to be fitted with a needle assembly, a plunger slidable within the barrel and having a plunger seal at its forward end, an annular chamber defined between the plunger and a wall surrounding the plunger, and means for establishing communication between the interior of the barrel and the annular chamber around the outer periphery of the plunger seal when the plunger is retracted.

A rearmost portion of the barrel may extend into the forward end of the chamber

Apertures in the rearmost portion of the barrel may be formed by circumferentially spaced axially extending slots.

The slots may extend through the barrel end giving the portion a castellated form. There may be a top seal between the rear end of the chamber and the plunger.

In one embodiment of the invention retraction of the plunger is effective to create a reduced pressure zone in the forward section of the barrel to assist transfer of one of the components to be admixed from the annular chamber to the barrel section forwardly of the plunger seal.

In a second embodiment of the invention, the means for providing communication comprises a one-way valve which may be pressure responsive.

The pressure responsive one-way valve may for instance comprise a generally U-shaped seal arranged with the mouth of the seal open towards the forward direction of plunger travel and with the radially outer limb of the U-shaped seal bearing slidably against the inner wall surface of the barrel.

The invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figures 1-3 show one embodiment of the invention by way of diagrammatic axial cross-sectional views through the syringe at consecutive stages in its preparation for use; and

Figure 4 is a diagrammatic fragmentary view of a second embodiment of the invention.

Referring now to Figures 1 to 3, the syringe comprises a barrel 10 having a forward end 11 adapted to be fitted with a needle assembly (not shown) and preferably one such as that described in our European Patent No. 0 776 225 (the disclosure of which is incorporated herein by this reference) providing for automatic retraction of the needle into the body of the syringe at completion of administration of the injection. The syringe further comprises a hollow plunger 12 which has a seal 13 at its forward end and is slidable axially within the barrel 10 between a forward position as shown in Figure 1 and a retracted position as shown in Figures 2 and 3. The fully retracted position may be defined by a stop (not shown). The forward position of the plunger as shown in Figure 1 is such as to allow a drug or like component (e.g. in the form a dry slug or powder 20) to be accommodated forwardly of the plunger. During operation of the syringe, it will be understood that the plunger 12 moves further forwardly of the position illustrated in Figure 1.

An annular chamber 14 of enlarged cross-sectional area is defined between the plunger 12 and a cylindrical wall 15 surrounding the plunger 12. A top seal 16 is provided between the rear end of the wall 15 and the plunger 12. The wall 15 also surrounds a rearmost annular portion 17 of the barrel 10 with which the plunger seal 13 remains engaged when the plunger is fully retracted. The annular portion 17 is of castellated form having circumferentially spaced axially extending slots 18.

The interior of the barrel 10 and annular chamber 14 define separate compartments which are pre-filled with the dry drug pellet 20 and liquid solvent or other diluent 21 respectively. In use, the pre-filled syringe is supplied with the plunger 12 substantially depressed into the barrel 10 as shown in Figure 1. The plunger 12 is withdrawn as shown in Figure 2 to evacuate the interior of the barrel forwardly of the plunger and bring the seal 13 into register with the portion 17 thus providing communication via the slots 18 around the outer periphery of the seal 12 between the annular chamber 14 and that section of the barrel disposed forwardly of the plunger. In this way, the solvent 21 is drawn into the barrel 10 through the slots 18 aided by the vacuum within the barrel. Evacuation is possible since the interior of the barrel is sealed usually by having the sharp end of the needle when present embedded into a sealing material in a protective sheath covering the needle. The syringe may be agitated as necessary to cause the pellet 20 to be dissolved as shown in progress in Figure 3 before administering the injection in known manner.

As mentioned above, the syringe of Figures 1 to 3 may be provided with a needle retraction mechanism for projecting the needle after use into the interior of the plunger. Thus, the forward end of the plunger may be appropriately adapted, inboard of the seal 13, so as to be broken away in response to operation of the needle retraction mechanism to allow the needle to be projected into the interior of the plunger in the manner described for example in European Patent No. 0 776 225.

Referring now to the embodiment of Figure 4, this comprises a cylindrical barrel 40 in which a hollow plunger 42 is slidable, the plunger being provided with an annular seal 44 which separates the barrel interior into a sections 46 and 48 disposed forwardly and rearwardly of the seal respectively. It will be understood that the axial dimensions of the forward and rearward sections will vary in use as the plunger seal travels forwardly or rearwardly. Where two components are to be admixed in preparation for administration, the forward section 46 may accommodate one (not shown) of the components while the rearward section 48 accommodates the second component 49 which may be a liquid diluent for the first component. In Figure 4, the plunger is shown in its initially depressed condition from which it must be retracted in order to transfer liquid from the section 48 to the section 46. A second seal 47, fixed with respect to the barrel, is provided between the plunger and the barrel at the rear end of the barrel.

The seal 44 comprises a flexibly deformable cup-type washer and is of generally U-shaped configuration in cross-section with the mouth of the U opening in the forward direction of plunger travel. The seal has two limbs 50, 52, one being attached to the plunger 42 and the other being arranged to bear against the inner periphery of the barrel 40. During forward travel, it will be understood that the sealing afforded by seal 44 is fully effective and serves to isolate the forward section of the barrel from the rearward section. However, during plunger retraction (i.e. movement to the right as viewed in Figure 4), the pressure in the rearward section 48 increases while the pressure in the forward section 46 decreases. When the pressure differential reaches a certain level which will usually be predetermined by design, the seal will deform and allow the liquid in the rearward section to be drawn into the forward section ahead of the plunger seal without assistance from gravity. The plunger may be retracted until substantially all of the liquid has been transferred to forwardly of the plunger seal. In this way, the forward section is charged with the liquid from the rearward section and the liquid (if necessary after mixing/dissolution of any drug component initially located forwardly of the plunger before retraction of the latter) can then be dispensed by advancing the plunger forwardly from its retracted position.

As described in connection with the embodiment of Figures 1 to 3, the syringe of Figure 4 may also be adapted for use with a needle retraction mechanism as described for example in European Patent No. 0 776 225, the forward end of the plunger being provided with a rupturable portion for co-operation with the needle retraction mechanism in producing an access opening through which the used needle can be projected into the hollow plunger.

It will be appreciated that it is not intended to limit the invention to the above examples only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof. Thus, for instance with reference to the embodiment of Figures 1 to 3 a dry drug need not be pre-loaded into the syringe, just a liquid drug into the chamber 14, the liquid being contained and protected from exposure to atmosphere by seals 13 and 16. Similarly in the embodiment of Figure 4, a liquid drug may be pre-loaded into the rearward section 48 for protection from exposure to atmosphere until the drug is to be administered.

Claims

1. A syringe comprising a barrel having a forward end adapted to be fitted with a needle assembly, a plunger slidable within the barrel and having a plunger seal at its forward end, an annular chamber defined between the plunger and a wall surrounding the plunger, and means for establishing communication between the interior of the barrel and the annular chamber around the outer periphery of the plunger seal when the plunger is retracted.

2. A syringe as claimed in Claim 1 in which said means comprises an aperture located so as to provide communication between the interior of the barrel and the annular chamber once the plunger has been retracted sufficiently to expose the aperture.

3. A syringe as claimed in Claim 1 in which said means comprises a one way valve.

4. A syringe as claimed in Claim 3 in which the one-way valve is pressure responsive.

5. A syringe as claimed in Claim 1 in which said means comprises a generally U-shaped seal, the mouth of the seal opening in the forward direction of plunger travel.

6. A syringe as claimed in Claim 1 in which the plunger seal constitutes said means.

7. A syringe as claimed in Claim 1, wherein a rearmost portion of the barrel extends into the forward end of the chamber

8. A syringe as claimed in Claim 7, wherein apertures in the rearmost portion of the barrel are formed by circumferentially spaced axially extending slots.

9. A syringe as claimed in Claim 8, wherein the slots extend through the barrel end giving the portion a castellated form.

10. A syringe as claimed in any one of the preceding claims, including a top seal between the rear end of the chamber and the plunger.

11. A syringe comprising a barrel, a plunger slidable in the barrel for movement between a forward position and a retracted position, an annular seal carried by the plunger for isolating a forward section of the barrel from a rearward section thereof at least during forward travel of the plunger, the forward and rearward sections of the barrel respectively forming first and second chambers, and means for establishing communication between said chambers around the outer periphery of the plunger seal during plunger retraction so as to allow transfer, in use, of a stored liquid from the second chamber to the first chamber.

12. A syringe as claimed in Claim 11 in which retraction of the plunger is effective to create a reduced pressure zone in the forward section of the barrel.

13. A syringe as claimed in Claim 11 or 12 in which the rearward section of the barrel is of increased cross-sectional area relative the forward section.

14. A syringe as claimed in Claim 13 in which the plunger seal remains in contact with a wall of the barrel throughout its travel between the forward and retracted positions, the barrel wall including at the retracted position of the plunger an apertured or slotted portion which is engaged by the plunger seal and, in part, defines the second chamber.

15. A syringe as claimed in Claim 11 in which said means comprises a generally U-shaped seal arranged with the mouth of the seal open towards the forward direction of plunger travel and with the radially outer limb of the U-shaped seal bearing slidably against the inner wall surface of the barrel.

16. A syringe as claimed in any one of Claims 11 to 15 in which the plunger is in its forward position and the second chamber contains a liquid component which is to be transferred to the first chamber on retraction of the plunger.

17. A syringe as claimed in Claim 16 in which the first chamber contains a component which is to be admixed with the liquid contained in the second chamber.

18. A syringe as claimed in any one of Claims 1 to 17 in which the plunger is hollow so as to accommodate the needle after use.

19. A syringe as claimed in Claim 18 in which the forward end of the plunger is provided with a rupturable portion located radially inboard of the plunger seal and which, when ruptured, provides access to the interior of the plunger, the syringe being provided with a needle retraction mechanism operable after use of the needle to effect rupture of said portion and projection of the needle into the plunger via the aperture created.