Hypodermic injection system

Details Hypodermic injection system Hypodermic injection system

1999-09-24

2001-07-10

Seidel, Richard K. (Department: 3763)

Surgery

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

Treating material introduced into or removed from body...

C604S121000, C604S132000, C604S142000, C604S185000, C604S187000, C604S212000, C604S069000, C222S092000, C222S095000, C222S633000

Reexamination Certificate

active

06258063

ABSTRACT:

This invention is in the field of the injection of liquid into tissue by generating a high pressure jet capable of passing through the skin.
Hypodermic injection system for fluids, comprising
a medication unit in which the liquid to be injected is stored and which has a first and a second region, said first region being squeezable or flexible and said second region having at least one orifice.
an explosion chamber in which the medication unit is located at least partially and a pressure generated within said explosion chamber is deforming said first region of the medication unit,
an activatable gas generator located inside the explosion chamber which generates a pressure within the explosion chamber when activated,
an activation unit for activating said gas generator
wherein said explosion chamber has a gas port connected to a free volume chamber having a variable volume.
A further aspect of the present invention are medication units which assure that the liquid medication does not contact insterile parts of the medication unit or the injection system prior to entering the skin.
In the field of medicine there are numerous methods for the targeted dispensing of medicines. Forms of medicine administration such as tablets, dragees, creams, and similar are all known. For a plurality of active ingredients such forms of administration are unsuitable because the physiologically active ingredient degrades before they can become active. In tablets which must be taken orally, the medicament, for example, has to be constructed such that it is resistant to aggressive stomach acids and on the other hand can be resorbed by the stomach or the intestinal wall into the blood circulation. For a large number of medicines it is not possible to develop a patient-friendly form of adminstration such as a tablet or a dragee. In such cases it is therefore necessary to introduce the medicine directly into body tissue or into the vascular blood system. Today it is usual practice that the injection occurs using a syringe. In the prior art however injection devices have been known for a long time which can be operated without using a hollow needle which is uncomfortable for the patient. Injection systems without a hollow needle employ a jet of liquid which is ejected at high velocity from an orifice and is capable of penetrating through skin and tissue. Such an injection is significantly less painful and can be performed by personnel who have not been trained in the use of syringes.
Injection systems employing a pressurized liquid jet of medication which penetrates the skin are called hypodermic injection systems within this application. Hypodermic injection is meant to include intra-dermal, subcutaneous and intra-muscular injections.
With an injection system in accordance with the invention, all medicines available in liquid form can be injected. The field of application covers for example painkillers (analgesics), insulin and also protein solutions. For protein solutions, especially solutions of human protein, remarkably it has been discovered that they can be administered substantially without any degradation by way of a high pressure jet.
Needle-free injection systems were described in the 50s and 60s. In U.S. Pat. Nos. 2,322,244 and 3,335,722 devices have been described, which use explosive substances for the generation of the necessary high pressure jet. Present-day systems, such as for example Vitajet® of the company Vitajet Corporation, employ a steel spring for the generation of the high pressure jet. A device which operates in an analogous manner is also marketed by Mediject Corporation. Such systems have the disadvantage that the user has to perform several awkward operational steps. First of all, the liquid to be injected is introduced into the injection device. Thereafter a steel spring is loaded by the rotation of device parts against each other. Especially for persons, who are ill or like many diabetics who are physically disabled, the necessary operational steps requires the application of enormous effort. An alternative to this system is offered by the aforementioned injection systems using explosives, because the energy from the explosive substance is used and a complicated loading of the spring is not necessary. The turning away from such systems which has taken place in the course of time is directly related to severe disadvantages with respect to hygiene and technical-safety aspects. U.S. Pat. No. 3,335,722 reveals, that cross-contamination of explosives and medicines are a particular problem of such constructions. In the U.S. patent an arrangement is suggested, in which capsules containing the medicine and the explosive substance are separated from each other and a special arrangement for the transfer of energy is employed. In the arrangement described an explosive is ignited by a contacting rod, as is the case, for example, with a rifle bullet. The gas resulting from the explosion accelerates a piston which is mechanically linked to a second piston which accelerates a rubber stopper which in turn forces a medicinal liquid out of the orifice on the opposite side. To prevent cross-contamination of combustion cases and medicine, complicated technical constructions are necessary which disadvantageously complicate the injection device and make it more expensive. Furthermore an ampule is required into which a rubber stopper is pushed. Because of the pressure in the ampule created by the movement of the stopper, it is necessary to make arrangements to ensure prevention of leaks between the ampule and the stopper. In this respect the choice of material for the ampule is critical, because a deformation when pressure is applied must not lead to leaks in the region of the stopper. The devices described in the prior art all exhibit generally the disadvantage that for the generation of pressure parts which can be compressed together, stoppers are employed and therefore sealing areas have to be controlled.
In the prior art there are also known devices for a needle-free injection of liquids which avoid stoppers or the like. European patent application 0 370 571 describes a system where an ampule which contains a liquid medication is being mechanically compressed by a rod. This compression drives the liquid medication through one or more orifices to generate a liquid jet. While this apparatus mostly avoids the problems associated with frictional surfaces and stoppers moving in a cylinder this apparatus has a drawback that the flexible part of the ampule may be destroyed when pressed by the rod. A further drawback of this device is that the pressures which can be applied to the ampule are limited due to the risk of destruction and also by the relatively low energy stored in a spring. Another disadvantage of this apparatus is that a mechanical compression of the ampule by a rod cannot guarantee that the liquid within the ampule is being ejected totally. Such a device is therefore insufficient when it is desired to inject a specific amount of medication.
In FR-1.121.237 there is described a device for the hypodermic injection of liquids using a high pressurized liquid jet. The device comprises a compressible container for liquid medication which is attached to a unit having a fluid channel. The unit with the fluid channel is connected to a unit with a nozzle so that a continuous channel is being formed through which the liquid medication can be expelled. For a hypodermic injection the unit with the channel is placed on a mounting element so that the medication container is surrounded by a chamber and pressure is applied to said chamber by ignition of an explosive. The apparatus described in FR-1.121.237 seems very similar to the present invention but has some technical drawbacks which are overcome by the present invention. The document FR-1.121.237 teaches that the medication container and the unit with the channel are combined by the user. The user fills the liquid to be injected into the medication container and tightly closes the medication container by screwing on the unit with the fluid channel.

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