Dual-chamber type injection cartridge with bypass connection

Details Dual-chamber type injection cartridge with bypass connection Dual-chamber type injection cartridge with bypass connection

1995-06-07

1998-02-10

McDermott, Corrine M.

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

604221, 604232, 604191, A61M 3700

Patent

active

057163383

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention refers to an injection cartridge of the dual-chamber type. In more detail, the invention relates to an injection cartridge of the dual-chamber type which has an improved arrangement of bypass means for the liquid component.


BACKGROUND ART

Injection cartridges of the dual-chamber type are well-known and have found a wide use. Such cartridges are primarily intended to be used when the liquid pharmaceutical composition to be injected is not stable for any extended period of time. In such cases, the composition to be injected is provided as two separate components, one solid component comprising the active pharmaceutical component in a dry state, and one liquid component comprising a solvent or dispersing agent for the solid component. These two components are enclosed in an injection cartridge of the dual-chamber type, such that the solid component is usually enclosed in a front chamber, while the liquid component is enclosed in a rear chamber. (In the following specification and claims, the expressions "front" and "rear" are to be regarded in relation to the direction in which the injectable composition is transported when an injection is administered.)
The two components are separated by a movable wall which seals against the interior wall of the cartridge. The rear chamber, which contains the liquid component, is also closed at its rear end by a piston which seals against the interior wall of the cartridge.
At its front end, the cartridge is usually closed by a rubber septum which is held into place by a metal capsule. This metal capsule has a central opening which exposes the rubber septum. Through this opening, a hollow needle may be inserted through this the septum to give a connection with the interior of the cartridge.
For conducting the liquid component over to the solid component for dissolution or dispersion, conventional dual-chamber injection cartridges are provided with at least one bypass channel in the wall of the cartridge. When the movable wall which separates the two chambers is at a suitable position, the bypass channel is exposed, so that the liquid component may flow around the movable wall and be mixed with the solid component.
When the cartridge is to be readied for the administering of one or more injections, pressure is applied to the rear piston to urge it forward. This pressure will be transmitted through the liquid phase, which is largely incompressible, so that also the movable wall, which separates the two chambers, is urged forward. When the front movable wall has been moved forward a determined length, it will be situated at the bypass channel, such that a flow of liquid from the rear chamber to the front chamber becomes possible. Further forward movement of the rear piston will now push the liquid from the rear chamber into the front chamber, while the movable wall remains essentially stationary.
When all the liquid has been expelled from the rear chamber, the rear piston will abut the movable wall, and further pressure forward will move the two walls together, to act like a single piston. The rubber septum closing the front end of the cartridge should now have been pierced by a hollow needle, which makes it possible to expel the ready-mixed preparation from the front chamber to be administered to a patient.
The dual-chamber injection cartridges described above have a number of important advantages and have found a wide use. One important use is in injection devices which are intended to be used by the patient to administer injections to himself. It is easy for the patient to prepare the injectable preparation from the two components immediately before the administering, and the risk of contamination is greatly reduced.
However, the conventional injection cartridges of the dual-chamber type also have certain shortcomings The cartridges are often used in injection devices which, more or less have the appearance of a fountain pen, and it is desirable that such a device should not be unduly thick or long. Thus, any measure which may make

REFERENCES:
patent: 2591046 (1952-04-01), Brown
patent: 3477431 (1969-11-01), Walecka
patent: 4874381 (1989-10-01), Vetter
patent: 5080649 (1992-01-01), Vetter
patent: 5435076 (1995-07-01), Hjertman et al.

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