Double pointed injection needle

Details Double pointed injection needle Double pointed injection needle

2001-05-30

2003-04-15

Lazarus, Ira S. (Department: 3749)

Surgery

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

Treating material introduced into or removed from body...

C604S198000, C604S188000, C604S171000, C604S111000, C604S110000

Reexamination Certificate

active

06547764

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a disposable double pointed injection needle having an injection part with a skin piercing end and a cartridge part for inserting into a cartridge containing a liquid medicine to be injected subcutaneously. The cannula of the injection needle is fastened in a needle hub for mounting on a syringe, which syringe supports the cartridge into which the cartridge part of the injection needle penetrates.
The invention further relates to an insulin injection system comprising a pen shaped syringe supporting a cartridge with insulin, a dose setting and injection mechanism and a disposable double pointed injection needle.
Injections where a liquid is expelled into the human body are usually performed either as intramuscular injections i.e. injections into the muscle tissue, or as subcutaneously injections i.e. injections into the subcutaneous tissue lying between the cutis and the muscle tissue.
When performing intramuscular injections of a vaccine it is according to British Medical Journal, volume 321, p. 931, important to use long injections needles in order to avoid local reactions such as redness and swelling. According to the article, use of injection needles having a length of 25 mm reduced the rate of local reaction significantly compared to an injection needle having a length of 16 mm.
Long injection needles must have a relatively large diameter in order not to break during injection. The injection needles referred to in the above mentioned article has a diameter of 23 G for the 25 mm long injection needle and 25 G for the 16 mm long injection needle.
The outside diameters of injection needles are indicated by a “G” and a gauge number increasing with thinner needles. Thus the outside diameter of a G 23 is 0.60 mm and of a G 25 0.50 mm.
It has for some years been known to provide long injection needles with safety protective devices in order to prevent accidental needle stick injuries. Such safety protective devices are e.g. known from EP 409.180 and U.S. Pat. No. 4.813.940. These known safety protective devices comprises a number of telescopic sleeves, which telescopic sleeves slides into each other in order to expose an injection needle covered by the telescopic sleeves when not in use. The injection needles used has opposite the skin piercing end a needle connector for connecting the injection needle with an ordinary hypodermic syringe. By the expression “ordinary hypodermic syringe” is meant a syringe of the type where the medicine to be injected is drawn from a vial into the syringe prior to each injection. In practical use the medicine has to flow through the injection needle twice for every injection when using such an ordinary hypodermic syringe, but due to the large diameter and the large bore of a long injection needle clogging is not a problem.
U.S. Pat. No. 5.429.612 discloses yet another long injection needle having a safety protective sleeve which can be moved into a position where the safety protective sleeve covers the injection part of the needle cannula. As can be seen in FIG. 1 of U.S. Pat. No. 5.429.612 the injection part of the needle cannula has a length, which makes it necessary to support the needle cannula by at least one disk
21
. The syringe is loaded with a flask containing the medicament to be injected. Since the syringe has no dose setting and injection mechanism like the ones known from insulin injection pens, the entire content of the flask is emptied into the patient in one injection, which is the usual procedure when injecting anaesthesia in dentistry. When using the embodiments shown in
FIGS. 2 and 3
, the user must manually rotate the shield after use in order to bring the tongue
26
from the first track
23
and into the second track
24
. Doing so the user is exposed to a great danger, since the rotation must be done after the contaminated needle cannula has been retracted from the body of the patient.
When providing long injection needle with safety protective sleeves there are hardly any limitation to the length of the injection needle as long as the relationship between the length and the diameter is sufficient to prevent unwanted needle breakage. The muscular tissue is in a human body normally located approximately 10 to 14 mm below the surface of the skin. The part of a long injection needle entering the human body therefore has to be at least 14 mm in order to reach into the muscular tissue of the human body. As can be seen from the prior art injection needles, the length of the needle cannula from its fastenings point in the needle connector to its skin piercing end is substantially longer than the part of the needle cannula, which enters the human body during injection. This presents however no problem since these needle has a large diameter sufficient to withstand breakage.
Some medicines however has to be injected subcutaneously i.e. in the subcutis lying between the cutis and a muscle membrane which cover the underlying muscles. If for instead insulin for treating diabetes is injected into the muscle tissue it will be absorbed in the body to quickly and an unwanted drop in the blood sugar may be the result. In order to prevent intramuscular injection of insulin it is quite common for people suffering from diabetes to inject into a lifted skin fold. It is however becoming more and more preferred by diabetic persons to inject directly at an angle of 90° without the skin fold, using an extra short needle. The extra short needle must have an overall length of the injection part of the needle cannula short enough to avoid intramuscular injections. Such extra short needles are e.g. known from WO 97.23253, which discloses an injection needle having an overall length of the injection part laying in the interval 4 to 6 mm.
Very short injection needle are not subject to breakage in the same degree as long injection needles, and can therefore be made with a much smaller diameter. WO 93.00948 reveals a short injection needle, having an injection part in the interval 8 to 12 mm, for injecting insulin. The diameter of the needle cannula is thinner than G 29. Such short and thin needles cannot be used in connection with an ordinary hypodermic syringe where the medicine is drawn up from a vial prior to each injection since this requires the medicine to flow through the needle twice for every injection, which can result in clogging of the bore of the injection needle, especially if the medicine is a suspension. However when the short and thin needle are used in connection with a syringe supporting a cartridge containing the medicine to be injected, the medicine only has to flow through the injection needle once which in itself halves the risk of clogging, and thereby allows very thin injection needles to be used. At the same time, when an injection needle has only a small diameter both outside and inside, the pressure needed to force a liquid through the bore of the injection needle is high when the injection needle is long, but substantially smaller if the injection needle is short.
SUMMARY OF THE INVENTION
These known short and thin injection needles are however not provided with any safety protective devices, while the safety protective sleeves known from the prior art would permanently cover a large part of the injection part of the injection needle thereby preventing a short injection needle from penetrating through the cutis layer, which layer usually is between 2 to 3 mm thick, and into the subcutis layer of a human body.
Injection needles with relatively thin diameter and with a length of the injection part of the needle cannula between 4 to 12 mm are often used for self-injection of insulin i.e. where the patient injects him or herself. However for self-injection in private settings, safety protective devices providing safety against accidental needle stick injuries are not considered to be important, since no other person beside the patient performing the self-injection has contact with the injection needle. Safety protective devices providing safety against accidental needle stick

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