Method of intradermally injecting substances

Details Method of intradermally injecting substances Method of intradermally injecting substances

2001-04-13

2003-05-27

Mendez, Manuel (Department: 3763)

Surgery

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

Treating material introduced into or removed from body...

C604S117000

Reexamination Certificate

active

06569143

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a method for delivering substances such as drugs, vaccines and the like used in the prevention, diagnosis, alleviation, treatment, or cure of diseases into the skin of an animal using an injection device having a needle cannula and a limiter for engaging the surface of the skin and limiting penetration of the tip of the needle cannula into the skin, and more specifically to a method for injecting such substances intradermally, i.e., preferably from approximately 1.0 mm to approximately 2.0 mm, and most preferably around 1.5 mm±0.2 mm to 0.3 mm, such that the substance is injected into the dermis layer of the animal. In addition, the method of the present invention includes fixing the orientation of the needle cannula, i.e., so that the needle cannula is preferably generally perpendicular to the plane of the skin engaging surface of the limiter within about fifteen degrees, and the skin engaging surface is generally flat.
BACKGROUND OF THE INVENTION
Intradermal injections are used for delivering a variety of substances. Many of these substances have proven to be more effectively absorbed into or react with the immune response system of the body when injected intradermally. Recently, clinical trials have shown that hepatitis B vaccines administered intradermally are more immunogenic than if administered intramuscularly. In addition, substances have been injected intradermally for diagnostic testing, such as, for example using what is known in the art as the “Mantoux test” to determine the immunity status of the animal against tuberculosis and the immediate hypersensitivity status of Type I allergic diseases.
An intradermal injection is made by delivering the substance into the epidermis and upper layers of the dermis. Below the dermis layer is subcutaneous tissue (also sometimes referred to as the hypodermis layer) and muscle tissue, in that order. There is considerable variation in the skin thickness both between individuals and within the same individual at different sites of the body. Generally, the outer skin layer, epidermis, has a thickness between 50-200 microns, and the dermis, the inner and thicker layer of the skin, has a thickness between 1.5-3.5 mm. Therefore, a needle cannula that penetrates the skin deeper than about 3.0 mm has a potential of passing through the dermis layer of the skin and making the injection into the subcutaneous region, which may result in an insufficient immune response, especially where the substance to be delivered intradermally has not been indicated for subcutaneous injection. Also, the needle cannula may penetrate the skin at too shallow a depth to deliver the substance and result in what is commonly known in the art as a “wet injection” because of reflux of the substance from the injection site.
The standard procedure for making an intradermal injection is known to be difficult to perform, and therefore dependent upon experience and technique of the healthcare worker. This procedure is recommended to be performed by stretching the skin, orienting the bevel of a 26 Gauge short bevel needle cannula upwardly and inserting the needle cannula to deliver a volume of 0.5 ml or less of the substance into the skin of an animal with the needle cannula being inserted into the skin at an angle varying from around 10-15 degrees relative to the plane of the skin to form a blister or wheal in which the substance is deposited or otherwise contained. Accordingly, the technique utilized to perform the standard intradermal injection is difficult and requires the attention of a trained nurse or medical doctor. This procedure also makes it essentially impossible to self-administer an intradermal injection. Inserting the needle to a depth greater than about 3.0 mm typically results in a failed intradermal injection because the substance being expelled through the cannula will be injected into the subcutaneous tissue of the animal. Further, the present method is not suitable for self-administration of intradermal injections.
The most frequent cause of a failed intradermal injection is derived from inserting the needle into the skin at an angle greater than 15 degrees. A further cause of error is derived from pinching rather than stretching the skin in the area of the injection, which is normally done when giving a subcutaneous rather than an intradermal injection. Pinching increases the likelihood of giving a subcutaneous injection. Procedural errors as described above result in delivering the contents of the injection into the subcutaneous layer, which can reduce the effectiveness of the injection, as well as possibly deliver the substance in a way not approved for delivery. Intradermal injections performed by using the standard procedure also are known to cause a significant amount of pain to the recipient of the injection because the needle cannula is inserted into the skin at an angle of about 10-15 degrees. By inserting the needle cannula at this angle, about 5 mm to about 6 mm of the needle is actually inserted into the skin. This results in a significant disruption of the pain receptors dispersed throughout the upper layers of the skin.
Accordingly, there has been a long felt need for a simplified method of performing an intradermal injection of substances which overcomes the problems and limitations associated with conventional methods, especially including reducing the probability of error and pain caused from the injection by making such injections less dependent upon experience and technique. In addition, there has been a need to limit the depth of penetration of the needle cannula into the skin of the animal to avoid entry into the subcutaneous layer of the skin as well as reliably fixing the orientation of the needle cannula relative to the skin. Also, there has been a need to apply pressure to the skin of the animal to facilitate formation of the blister or wheal in the skin in which the substance is deposited or otherwise contained and avoid wet injections.
SUMMARY OF THE INVENTION AND ADVANTAGES
In contrast to the conventional methods discussed above, it has been found by the applicant that a method of intradermally injecting substances into the skin can be used in accordance with the present invention to effectively and reliably deliver such substances intradermally. Specifically, the method includes fixing the orientation of the needle cannula relative to the skin and engaging the surface of the skin to limit the depth of penetration of the needle cannula into the skin, i.e., preferably from approximately 1.0 mm to approximately 2.0 mm, and most preferably around 1.5 mm±0.2 mm to 0.3 mm, to avoid entry into the subcutaneous layer. In addition, the method includes applying pressure to the surface of the skin to facilitate delivery of the substance, particularly formation of a blister or wheal in the skin in which the substance is deposited or otherwise contained. Further, the pressure applied masks the pain derived from the intradermal injection by stimulating the muscle fibers to block the pain receptors. Many substances have proven to be more effective when injected intradermally in the prevention, diagnosis, alleviation, treatment, or cure of diseases. These include several drugs and vaccines such as, for example, influenza vaccines, hepatitis B vaccine, rabies vaccines tuberculin test substance and many others. These vaccines, drugs and the like will hereinafter be referred to as substances. It is also possible to self-administer intradermal injections by the method of this invention.
The hypodermic needle assembly set forth above includes the elements necessary to perform the present invention directed to an improved method of making an intradermal injection into the skin of an animal including the steps of providing a drug delivery device including a needle cannula having a forward needle tip and the needle cannula being in fluid communication with a substance contained in the drug delivery device and including a limiter portion surrounding the needle cannul

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