Injection device

Abstract

An injection device comprising a housing in which can be mounted a syringe comprising a barrel for holding a volume of medicament, a needle at one end of, the barrel and a plunger axially-moveable in the barrel to a forwardmost position, the injection device further comprising a syringe support means for supporting the barrel at an axial location at or forward of the forwardmost position of the plunger and having a reaction surface for the syringe, whereby in use said reaction surface provides an axial compressive force on said barrel when a forward axial force is applied to the plunger.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority under 35 U.S.C. §119 to United Kingdom Patent Application Nos. GB0601309.8 filed Jan. 23, 2006, GB0602411.1 filed Feb. 7, 2006, and GB ______ filed Mar. 21, 2006. The entire disclosures of the above-referenced patent applications are incorporated herein by reference in their entirety. FIELD [0002] This invention relates to the field of injection devices for the administration of liquid medication, for example, interferon. BACKGROUND [0003] One typical known device is described in WO00 / 09186 (Medi-Ject Corporation) for “Needle assisted jet injector” and this document gives a useful summary of other prior art devices. [0004] The device of WO 00 / 09186 includes a needle which is, in one embodiment, retractably located within an injector nozzle assembly. Upon activation of a force-generating source, a portion of the needle extends past the nozzle assembly and penetrates the outer layer of skin to deliv...

AI Technical Summary

Benefits of technology

[0013] It is also desirable to minimise the duration of the injection, i.e. to maximise the speed at which the medicament is delivered from the syringe. Particularly when the needle diameter is small, minimising the duration of the injection also means an increase in the force used to eject the medicament from the syringe.

[0014] An increase in the forces on the syringe consequently increases the likelihood of the syringe breaking during the injection. The risk of the syringe breaking during injection is significant, and is not only inconvenient and costly but is also potentially dangerous. If breakage occurs, it is possible :that glass fragments and/or the needle may become detached and exit the front of the device causing injury. Furthermore, there is the risk that the remaining medicament will leak or be ejected from the device in an uncontrolled manner, potentially delivering the wrong dose into the patient, or causing injury e.g. if the medic

Problems solved by technology

Any modification to the standard syringe may require further trials and approval, adding delay and expense.

However, glass is notoriously fragile and there is a risk of damage or breakage of the syringe during injection if the forces to which the syringe is subjected by the injection device are not properly controlled.

This tension is undesirable in a glass barrel, which may become damaged or broken, especially if the medicament comprises a particularly viscous liquid which requires greater force to expel it from the syringe via the needle.

However, for a given length of needle, the smaller the needle diameter, the greater the force required to eject the medicament from the syringe.

An increase in the forces on the syringe consequently increases the likelihood of the syringe breaking during the injection.

The risk of the syringe breaking during injection is significant, and is not only inconvenient and costly but is also potentially dangerous.

If breakage occurs, it is possible :that glass fragments and / or the needle may become detached and exit the front of the device causing injury.

Furthermore, there is the risk that the remaining medicament will leak or be ejected from the device in an uncontrolled manner, potentially delivering the wrong dose into the patient, or causing injury e.g. if the medicament contacts the patient's skin or eyes.

These problems are amplified when the medicament is viscous as a more powerful energy source is needed in such applications so that the forces involved are greater.

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