Abstract:
An autoinjector useful for, inter alia, providing an injection of liquid medicament is uniquely capable of providing injections, utilizes a needle depth adapter to provide injection depths with a combination of accuracy and precision not heretofore seen. In addition, the autoinjector with needle depth adapter can include a variety of size needle depth adapters to provide an autoinjector of varying, precise injection depths and which can be readily and easily manufactured. The autoinjector includes a housing, cartridge assembly, needle, needle depth adapter, and power providing assembly.

Description:
[0001]    The present application is a continuation of U.S. patent application Ser. No. 11/788,823 filed Apr. 20, 2007 entitled “Autoinjector with Needle Depth Adapter”, which claims benefit of U.S. provisional patent application Ser. No. 60/852,493 entitled “AUTOINJECTOR WITH NEEDLE DEPTH ADAPTER” filed Oct. 18, 2006 which is hereby incorporated by reference. Additionally all patents and publications described or discussed herein are hereby incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to an autoinjector with a novel needle depth adapter useful for applications including administering injections to both humans and animals. More particularly, the present invention relates to autoinjectors capable of injecting medicaments into a precise location within the subject. Furthermore, this invention can be specially adapted for subcutaneous injections and also includes a novel method of administering medicaments to a desired depth within a patient. 
         [0004]    2. Background Art 
         [0005]    Autoinjectors have become quite popular and have experienced widespread use due to a variety of advantages autoinjectors have over typical manual syringe injectors. Essentially, an autoinjector is an automatic injection system which is designed to deliver a specific dosage of a liquid medicament into an individual. Through their pen-styled design, autoinjectors are fairly simple to use and often have design characteristics enabling an individual to administer a self-injection. The majority of autoinjectors in production today are spring-loaded autoinjectors which provide an individual with less hesitation in self-administering liquid medicaments than would a manual syringe and needle. Furthermore, automatic injectors are much simpler to use in times of stress, pain, or other medical ailments and require less concentration then would a standard manual syringe and needle. 
         [0006]    An additional advantage of autoinjectors is that these injectors contain a specific size dose of a liquid medicament sealed within and can be stored for a significant duration. Despite the capability for being stored for a significant duration, the autoinjector is still able to provide an immediate injection even under severe medical stress. Furthermore, automatic injectors will deliver a previously determined dosage of the medicament upon activation, thus precluding the need to measure the specific amount of medicament needed at the time the injection is administered. 
         [0007]    Depending on the type of drug and the ailment which the medicament is designed to alleviate, the autoinjector is designed to penetrate to a certain depth. Commonly, most autoinjectors are used for intramuscular injections and have only most recently been designed to provide for subcutaneous injections. Specifically, certain medicines, especially medicines for alleviating migraine headaches, must be injected in the subcutaneous region of a patient rather than have the injection site be at an intramuscular location. The key design consideration in creating an autoinjector for a subcutaneous injection is to attempt to insure that the needle of the autoinjector does not penetrate to a depth beyond the subcutaneous region of the patient. For example, in Sarnoff et al., U.S. Pat. No. 5,102,393, an autoinjector is disclosed which claims to be convertible from an intramuscular to subcutaneous mode of injection. The autoinjector of the &#39;393 patent is taught to have the capability of being actuated in a manner so as to cause virtually no compression of the subcutaneous tissue under the skin at the injection site of the user. For using the autoinjector of the &#39;393 patent in a subcutaneous mode, another device is secured to the autoinjector which attempts to preclude the needle from extending substantially beyond the subcutaneous tissue. 
         [0008]    In U.S. Pat. No. 5,873,856, Hjertman et al., a device is disclosed which claims to have a limited depth penetration needle housing. The &#39;856 patent teaches a device which can be adjusted for specific depths of penetration which claims to include a subcutaneous depth of penetration. Furthermore, the disclosure teaches a device where one can readily adjust the needle penetration depth between different pre-set values. 
         [0009]    In Saied et al., U.S. Pat. No. 6,312,412, injectors are disclosed which can provide for either intramuscular or subcutaneous injection. The specific injector of the &#39;412 patent includes means for adjusting the medication needle so that the medication needle can be inserted to varying depths within the patient. 
         [0010]    De La Serna et al. (U.S. Pat. No. 7,011,649) describes a syringe cartridge which may include an adjustable tip which will allow a user to easily adjust the injection depth for the desired application. 
         [0011]    Unfortunately, autoinjectors produced by the prior art processes are not effective for administering subcutaneous injections at an exact and repeatable depth of penetration. The injectors generally available do not have as tight a range of penetration depth as is desired, and furthermore, include needle tips which are adjustable and provide for another variable which can lead to an incorrect penetration depth in times of emergency trauma. In addition, prior art subcutaneous injectors do not include a method wherein the depth of penetration is limited to a small range of penetration depths. 
         [0012]    What is desired, therefore, is an autoinjector which has a tight range regarding the needle&#39;s depth of penetration wherein the medicament contained within the autoinjector is injected into a specific location within the patient, including the subcutaneous region. Indeed a combination of characteristics including a much more precise range of penetration depths as well as simplicity of use have been found to be necessary for the use of autoinjectors for administering specific medicament into the subcutaneous region of a subject. Also desired is the method for providing more exact injections, including injections within the subcutaneous region. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention provides an autoinjector which is uniquely capable of providing injections, preferably subcutaneous injections, with improved precision. The inventive autoinjector utilizes a needle depth adapter to provide injection depths with a combination of accuracy and precision not heretofore seen. In addition, the autoinjector with needle depth adapter can include a variety of size needle depth adapters to provide an autoinjector of varying, precise injection depths and which can be readily and easily manufactured. 
         [0014]    More particularly, the autoinjector with needle depth adapter can provide injections in the subcutaneous region wherein the injection is at a depth of from about 0.15 inches to about 0.30 inches, and more preferably of from about 0.2 inches to about 0.25 inches within the subject. An important characteristic of the autoinjector when intended for self-administered injections is that the autoinjector comes preassembled with a fixed injection depth thereby limiting the possibility of injecting at erroneous depths during times of trauma. 
         [0015]    The inventive autoinjector with needle depth adapter should have a needle depth adapter comprised of a material which includes thermoplastics, polymers, hydrocarbon polymers or cellulosic compositions as well as deformable metals to provide for the desired depth of injection in a vary precise range. Furthermore, the needle depth adapter is comprised of a deformable material to eliminate tight tolerances in manufacturing while still providing for a very controlled injection depth. Yet furthermore, by use of a deformable material in forming the needle depth adapter of the autoinjector, the needle depth adapter can dissipate excessive mechanical force created by the powering mechanism of the autoinjector, and thus, can eliminate autoinjector failure wherein the force-providing component is too strong. 
         [0016]    More particularly, the needle depth adapter is in close proximity to the needle hub, with the needle depth adapter having a partition for the extension of the needle there through. As such, the needle depth adapter can be contoured to align closely with the needle hub and will move with the cartridge assembly toward the proximal end of the autoinjector upon activation of the autoinjector. 
         [0017]    The autoinjector with needle depth adapter is especially useful for providing the subcutaneous injection of medicaments where the medicament&#39;s effectiveness depends on the location of injection within the patient. With the preferred small range of from about 0.20 inches to about 0.25 inches for subcutaneous injections, the autoinjector with needle depth adapter is suitable for medicaments such as sumatriptan, rizatriptan, frovatriptan, zolmitriptan, naratriptan, and loperamide hydrochloride. Furthermore, a variety of other drugs, including drugs of the epinephrine variety can be loaded into the autoinjector and injected also to a precise depth. 
         [0018]    Advantageously, the autoinjector with needle depth adapter provides a method for administering injections at a much more precise injection depth making this method highly suitable for use in emergency trauma situations. 
         [0019]    An object of the invention, therefore, is an autoinjector with a needle depth adapter having characteristics which enable it to be employed for subcutaneous injections which can be self-administered. 
         [0020]    Another object of the invention is an autoinjector having improved precision with regard to depth of needle penetration within the subject to be injected. 
         [0021]    Yet another object of the invention is an autoinjector having a needle depth adapter so that the depth of penetration of the needle is located within the subcutaneous region of the subject. 
         [0022]    A further object of the invention is an autoinjector having a punctureable needle sheath wherein the sheath does not have to be removed prior to administering the injection. 
         [0023]    Another object of the invention is an autoinjector for injecting sumatriptan into the subcutaneous region of the subject. 
         [0024]    Still another object of the invention is an autoinjector with needle depth adapter wherein the needle depth adapter is deformable and is easily assembled into the autoinjector without the need for precise interface geometry. 
         [0025]    Yet another object of the invention is an autoinjector with a needle depth adapter wherein the depth of the injection is fixed so as to reduce the possibility of erroneous depth injections. 
         [0026]    Another object of the invention is a method of providing injections with improved precision which can be self-administered by an individual. 
         [0027]    These aspects and others that will become apparent to the artisan upon review of the following description can be accomplished by providing an automatic injector with a needle depth adapter wherein the needle depth adapter limits the forward progression of the needle, and thus, controls the depth of injection within the patient. The inventive autoinjector with needle depth adapter advantageously can provide precise injections, including subcutaneous injections in the range of from about 0.15 inches to about 0.30 inches and more preferably of from about 0.20 inches to about 0.25 inches. 
         [0028]    Preferably, the needle depth adapter is comprised of a deformable material which can include a variety of polymers as well as deformable metals which will limit the forward progression of the needle and can also dissipate excess force created by the spring-type mechanism within the autoinjector. Advantageously, the needle depth adapter can range from about 0.4 inches to about 0.6 inches in width and from about 0.2 inches to about 0.4 inches, preferably about 0.3 inches in length although it can be modified to include greater or smaller lengths depending on the specific desired depth of injection. Advantageously, the automatic injector with needle depth adapter includes a fixed injection depth of the final injector product thereby eliminating the potential for erroneous injection depths which can occur from adjustable autoinjector types. 
         [0029]    Furthermore, the method for producing more precise injections includes the use of the needle depth adapter to preclude the forward movement of the needle thereby precisely limiting the depth of injection to a specifically tailored range. 
         [0030]    It is to be understood that both the foregoing general description and the following detailed description provide embodiments of the invention and are intended to provide an overview or framework of understanding to nature and character of the invention as it is claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a longitudinal sectional view of a prior art automatic injector in the non-actuated position. 
           [0032]      FIG. 2  is a longitudinal sectional view of the prior art automatic injector of  FIG. 1  in the actuated position. 
           [0033]      FIG. 3  is a longitudinal sectional view of an automatic injector according to the present invention in the non-actuated position. 
           [0034]      FIG. 4  is a view of a needle depth adapter according to the present invention. 
           [0035]      FIG. 5  is a longitudinal section view of an automatic injector according to the present invention in the actuated position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    General automatic injector  10  of the prior art typically includes housing  12 , powering assembly  14 , and needle cartridge assembly  16  as illustrated in  FIG. 1 . Automatic injector  10  may further include needle  18  attached by needle hub  20  with needle  18  being shrouded by buckling sheath  22 . 
         [0037]    Needle cartridge assembly  16  is slidingly located within housing  12  of autoinjector  10  and contains the liquid medicament intended for injection within the patient. Specifically, chamber  24  contains the liquid medicament wherein upon activation, plunger  26  will force liquid medicament out through the piercing end of needle  18 . Needle hub  20  holds needle  18  in a fixed position with chamber  24  so that the liquid medicament can communicate from chamber  24  to needle  18  and out through the piercing end of needle  18  and into a subject. 
         [0038]    As further illustrated in  FIG. 1 , power assembly  14  includes compressed spring  28  which possesses the potential energy capable of thrusting the needle out of autoinjector  10  and also infusing the liquid medicament from chamber  24  out through piercing end of needle  18 . In the inactivated condition, needle  18  is contained within autoinjector  10 , the length as illustrated by needle containment length  11 . Otherwise stated, needle containment length  11  is the length of needle  18  within autoinjector  10  prior to utilizing autoinjector  10  to dispense a medicament. 
         [0039]    When using autoinjector  10  of the prior art, the safe pin of autoinjector  10  is removed and subsequently autoinjector  10  is pressed at proximal end  30  against the patient for which the injection is to be administered. When injector  10  is actuated, compressed spring  28  of power assembly  14  decompresses and propels needle assembly  16  toward proximal end  30  of injector  10 . As illustrated in  FIG. 2 , needle assembly  16  including needle  18  and chamber  24  as well as plunger  26  are propelled forward under the influence of the decompression of spring  28 . With this forward motion, buckling sheath  22  compresses between proximal end  30  of autoinjector  10  and needle assembly  16 . The piercing end of needle  18  breaks through buckling sheath  22  and emanates out of proximal end  30  of autoinjector  10 . At the instant needle  18  reaches its extended length, the medicament contained in chamber  24  is pushed forward by plunger  26  and thus exits the piercing end of needle  18  and into the subject. 
         [0040]    The depth to which needle  18  penetrates the patient is determined by the forward progression of needle  18  out of proximal end  30  of autoinjector  10  and by the extent of buckling sheath  22 . When needle  18  is in the foremost position, needle  18  is precluded from going more forward by the force provided by buckling sheath  22  against the inside of proximal end  30  of autoinjector  10 . Specifically, buckling sheath  22  buckles under the force provided from decompressing spring  28  of power assembly  14  and thereby determines the extended length of needle  18  of prior art autoinjector  10 . Compressed sheath length  21  is the length of buckling sheath  22  after buckling and thus maintains a portion of needle  18  within autoinjector  10 , a length about equal to compressed sheath length  21 . By buckling sheath  22  buckling to compressed sheath length  21 , needle  18  only extends to extended needle length  23 , as a length of needle  18  about equal to compressed sheath length  21  is maintained within autoinjector  10 . 
         [0041]    When used for intramuscular injections, the extended length of the needle, extended needle length  23 , is of from about 0.7 inches to about 0.9 inches determined through the buckling of the sheath at the proximal end of the prior art autoinjector. Much more precise injection depths are difficult to achieve as the buckling of the sheath can vary slightly from one autoinjector to another. Generally, prior art autoinjectors with buckling sheaths are difficult to produce wherein the range of injection depth from one autoinjector to another varies less than about 0.1 inches. Moreover, when autoinjectors are used to administer medicaments in the subcutaneous region of a patient, a buckling sheath used for determining the needle depth is quite problematic as injections within the subcutaneous region require a very precise injection location and have a low tolerance for injections administered outside of this location. 
         [0042]    As illustrated in  FIG. 3 , autoinjector  32  of the present invention includes housing  34 , cartridge assembly  36 , needle  38 , needle depth adapter  40 , and power providing assembly  42 . 
         [0043]    Housing  34  includes an outer tube-type design with proximal end  44  and distal end  46 . Housing  34  of autoinjector  32  is designed so that proximal end  44  is the end nearest to the injection site of the subject, as distal end  46  is the end most distant from the injection site. Furthermore, housing  34  may be constructed of any rigid material including metals, alloys, polymer-type materials, glass, as well as ceramic composites. Preferably, housing  34  is comprised of a rigid material so as to be able to withstand the mechanical stress received upon the actuation of power providing assembly  42 . Most often, a polymer or plastic material is suitable for housing  34  as these materials provide sufficient strength while also possessing a high ratio of strength to density allowing for the creation of a relatively lightweight autoinjector. 
         [0044]    In one embodiment, housing  34  of autoinjector  32 , is designed so that cartridge container  48  fits within the inner diameter of housing  34 . Cartridge container  48  is designed so as to maintain a sliding configuration within housing  34  upon application of force to the distal end of cartridge container  48 . As such, the outer diameter of cartridge container  48  is about slightly less than the inner diameter of housing  34 . Both housing  34  and cartridge container  48  can be designed in a variety of sizes and configurations dependent upon the specific use desired for the autoinjector. For example, in designing autoinjectors for easy portability, the autoinjector may be designed in a longer, slimmer fashion so as to be easily carried with the user at all times. Furthermore, when a large quantity of medicament is required, the autoinjector and cartridge container can be designed so as to accommodate the large amount of medicament. 
         [0045]    Cartridge container  48  may be retained within housing  34  of autoinjector  32  in a variety of ways. In one embodiment, cartridge container  48  may be retained within housing  34 , by a return flange to maintain cartridge container  48  within autoinjector  32 . 
         [0046]    Furthermore, in the aforementioned embodiment, cartridge container  48  has abutment surface  35  for abutting needle depth adapter  40 . In embodiments not including cartridge container  48 , the housing assembly may contain an abutment surface for abutting needle depth adapter  40 . Abutment surface  35  may be angled as illustrated in  FIG. 3  and  FIG. 5 . or in other embodiments may be rounded or flat. Typically, abutment surface  35  is angled so as to only contact and compress the corner of the needle depth adapter upon abutment. 
         [0047]    Cartridge assembly  36  is moveably situated within cartridge container  48  and thus will move toward proximal end  44  of autoinjector  32  upon sufficient force provided by power providing assembly  42 . Cartridge assembly  36  is designed so that the exterior diameter of cartridge assembly  36  is slightly less than that of the interior diameter of cartridge container  48  so that cartridge assembly  36  can move in a longitudinal direction without excessive friction. Furthermore, the medicament is contained within cartridge assembly  36  and can be designed to accommodate a variety of medicament types including larger or smaller quantities as well as high or low viscosity medicaments. Typically, cartridge assembly  36  is comprised of a rigid material often including glass, metals, polymers, thermoplastics, or composites. As the medicament is contained within cartridge assembly  36 , the cartridge assembly is designed so as to preclude the absorption of the contained medicament as well as to preclude the migration of the medicament out of cartridge assembly  36 . 
         [0048]    The proximal end of cartridge assembly  36  is designed to connect to needle assembly  50  which is comprised of needle  38 , needle hub  54 , and punctureable sheath  56 . Needle hub  54  has a first connection point for connecting to the proximal end of cartridge assembly  36  and a second connection point for receiving the attachment end of needle  38 . Needle hub  54  may connect to the cartridge assembly in multiple ways including, but not limited to, a screw-type attachment, a pressure fit, or even an adhesive connection between the needle hub  54  and cartridge assembly  36 . Furthermore, needle hub  54  may preferably be spun or crimped into place about the end of cartridge assembly  36  so that a secure connection is achieved. Generally, needle hub  54  may communicate needle  38  to cartridge assembly  36  in the manners commonly taught in U.S. Pat. No. 3,380,449, the disclosure of all of which is hereby incorporated by reference into the present specification. 
         [0049]    Needle  38  of needle assembly  50  may be of any design suitable for the injection of a medicament into a patient. For example, needle  38  may have an interior diameter suitable for either low viscosity or high viscosity medicament, may be of either an oval or circular cross-sectional design and can also be of a variety of different lengths depending upon the size and intended use of the novel autoinjector. 
         [0050]    Punctureable sheath  56  functions to maintain sterility of needle  38  and may be comprised of a polymer, plastic, or suitable metal material such as aluminum. The distal portion of punctureable sheath  56  is attached to needle hub  54 . This attachment may be by pressure fitting, shrinking, folding, screw type, or adhesion wherein the complete encompassing of needle  38  by punctureable sheath  56  provides for an enduring sterile environment for needle  38 . In a preferable arrangement, punctureable sheath  56  may be elastically fit to needle hub  54  by the inherent elastic characteristics of sheath  56 , as the open end of sheath  56  may be stretched to fit over a portion of needle hub  54 . Advantageously, punctureable sheath  56  does not require specific design criteria or as precise manufacturing as the prior art buckling sheath as punctureable sheath  56  is not responsible for controlling the depth of penetration of the needle of the autoinjector. As such, punctureable sheath  56  may be comprised of an extremely thin material or can be designed to more closely guard needle  38  thereby being able to better maintain a sterile environment around the needle while providing a compact autoinjector design. 
         [0051]    Needle depth adapter  40  is located within cartridge container  48  in contact with needle hub  54  at the proximal end of cartridge assembly  36  and has an opening for needle  38  to extend there through. Depth adapter  40  is moveable with needle hub  54  and will move toward the proximal end of the autoinjector upon the application of mechanical force by power providing assembly  42 . 
         [0052]      FIG. 4  illustrates needle depth adapter  40  in one embodiment having an annular shape. For limiting the needle depth for subcutaneous injections, needle depth adapter  40  has a longitudinal length  64  which is from about 0.2 inches to about 0.4 inches and more preferably about 0.27 inches to about 0.33 inches in length. Radial exterior diameter  62  is designed so that exterior diameter  62  is less than the interior diameter of cartridge container  48  and is typically from about 0.4 inches to about 0.6 inches and more preferably from about 0.50 inches to about 0.52 inches. 
         [0053]    Furthermore, distal end  66  of needle depth adapter  40  is in contact with the proximal end of cartridge assembly  36 . Generally, distal end  66  of needle depth adapter is perpendicular to exterior surface  68  of needle depth adapter  40  providing for a flat and even surface for contacting cartridge assembly  36 . Additionally, abutting side  70  of needle depth adapter  40  may be in a perpendicular relation to exterior surface  68  and thus parallel to distal surface  66  providing a cylindrical-type shape to needle depth adapter  40 . 
         [0054]    Typically, needle depth adapter  40  has a ratio of exterior diameter  62  to longitudinal length  64  of greater than about 1. Furthermore, interior diameter  74  is of from about 0.2 to about 0.4 and preferably of from about 0.25 inches to about 0.35 inches to accommodate the extension of the proximal end of cartridge assembly  36  there through. Internal diameter  74  must be at least large enough for needle  38  to extend there through and can optionally be designed even larger so that a substantial portion of cartridge assembly  36  extends into the interior of needle depth adapter  40 . As such, radial thickness  72  may be varied to accommodate a variety of autoinjector designs while still providing for a precise depth of injection. Most often, radial thickness  72  is of from about 0.05 inches to about 0.18 inches and preferably from about 0.10 inches to about 0.12 inches. Additionally, the needle depth adapter can also have a ratio of longitudinal length  64  of the needle depth adapter as measured from the distal surface to the proximal surface, to radial thickness  72  of greater than about 2, and preferably about 3. 
         [0055]    Needle depth adapter  40  can be comprised of a variety of materials including thermoplastics, polymers, hydrocarbon polymers, deformable metals, cellulosic compositions and combinations thereof. Preferably, the material used for needle depth adapter  40  is a deformable material which is defined as material which can experience a change in shape due to the application of force. The choice of deformable materials is to negate the need to design precise interface geometry with tight tolerances when assembling autoinjector  32 . Furthermore, the use of a deformable material for needle depth adapter  40  provides for the absorption of excess force created by power providing assembly  42 . In a preferable embodiment, needle depth adapter  40  will be comprised of a hydrocarbon polymer having slight deformable characteristics when abutting side  70  of needle adapter  40  contacts abutting surface of needle hub  54  of needle assembly  50 . Upon abutting abutment surface  35  of the autoinjector with abutting side  70  of needle adapter  40 , abutting side  70  can deform slightly to dissipate mechanical energy. This deformation is described as slight as only the corner edge between exterior surface  68  and abutting side  70  deforms as is best illustrated in  FIG. 5 . 
         [0056]    Power providing assembly  42  is capable of releasing mechanical energy and thus driving cartridge assembly  36  with needle assembly  50  as well as needle depth adapter  40  toward the proximal end of autoinjector  32 . The power providing assembly may extend into the distal portion of housing  34  of autoinjector  32  and is in contact with the distal end of cartridge assembly  36 . In one embodiment, the power providing assembly  42  contains a compressed spring which contains the mechanical energy necessary to propel cartridge assembly  36 , needle assembly  50 , and needle depth adapter  40  toward the distal end of autoinjector  32 . 
         [0057]      FIG. 5  illustrates a longitudinal view of the present invention in an actuated condition. Upon actuating activation point  58 , cartridge assembly  36 , needle assembly  50 , and needle depth adapter  40 , are propelled forward toward proximal end  44  of autoinjector  32 , preferably under the influence of the compressed spring contained within power providing assembly  42 . Specifically, cartridge assembly  36  slides forward within cartridge container  48  thus progressing needle  38  enclosed in punctureable sheath  56  forward for the injection. Preferably, proximal end  44  of autoinjector  32  is placed in close contact with the subject of which to be injected. As needle  38  moves proximately forward, needle  38  punctures punctureable sheath  56  and exits proximal end  44  of autoinjector  32  and subsequently enters the body of the subject at the location where the injection is to be administered. The forward progression of needle  38  is stopped at the point where abutting side  70  needle depth adapter  40  contacts abutting surface  35  at proximal end  44  of autoinjector  32  resulting needle  38  extending to needle extension length  39 . Specifically, abutting surface  35  is comprised of rigid interior shoulders of cartridge container  48  but may also be of housing  34  in other embodiments. Abutting surface  35  is also virtually nonflexible providing a surface so that a precise injection depth can be realized. As such, abutting surface  35  acts as a precise mechanical stop to the forward progression of needle  38  by contacting abutting side  70  of needle depth adapter  40 , resulting in a novel autoinjector having a very precise penetration depth. The length of needle extension length  39  of the novel autoinjector  32  is much more precise than the prior art needle length  23  illustrated in  FIG. 2 , as the deviation from a desired extension length is much smaller through the use of the needle depth adapter of the present invention than is by using the buckling sheath of the prior art. 
         [0058]    For example, in administering subcutaneous injections, the needle depth adapter of the present invention provides for a precise pre-determined depth of from about 0.15 inches to about 0.30 inches, and more preferably of from about 0.20 inches to about 0.25 inches. With this precise and advantageously smaller range of potential needle penetration depths, medicaments can be more accurately delivered to an exact location within the subject. 
         [0059]    Once needle  38  is fully extended to the needle extension length  39  limited by needle depth adapter  40 , power providing assembly  42  forces plunger  60  located within cartridge assembly  36  forward toward the proximal end of autoinjector  32 . The movement of plunger  60  applies pressure to the liquid medicament contained within cartridge assembly  36  causing the medicament to exit out through the piercing end of needle  18  at the desired depth within the subject. For example, medicaments such as, but not limited to, sumatriptan, rizatriptan, frovatriptan, zolmitriptan, naratriptan, as well as loperamide hydrochloride can be utilized by the autoinjector of the present invention. 
         [0060]    The invention of the present application can be utilized and is preferable for use with medicaments requiring injection at a specific depth within a subject. While the invention can be utilized for both intramuscular and subcutaneous injections, the invention is especially useful for subcutaneous injections wherein medicaments must usually be injected at a much more precise depth. While the preferable range for subcutaneous injections utilizing a needle depth adapter is from about 0.15 inches to about 0.30 inches and more preferably of from about 0.20 inches to about 0.25 inches, the needle depth adapter can be configured in a variety of sizes so as to provide for other precise needle injection depths. 
         [0061]    The invention of the present application can be utilized by an individual for self-administration or by another individual on a subject. With the medicament pre-loaded within the autoinjector and the needle being fixed at a specific length with the needle depth adapter providing for a specified injection depth, the autoinjector can be utilized by individuals having very little or no medical training. Furthermore, the simplicity of the autoinjector of the present invention having a fixed needle and predetermined injection depth determined by the needle depth adapter, makes the autoinjector suitable for use in emergency trauma situations wherein prior art autoinjectors may provide erroneous injection depths. Additionally, the punctureable sheath is preferably not removed prior to administering the injection as the needle of the autoinjector of the present invention pierces through the sheath upon activation of autoinjector. This design adds to the simplicity of use of the autoinjector when compared to many prior art autoinjectors where the sheath must be removed prior to activation of the injector. 
         [0062]    Accordingly, by the practice of the present invention, autoinjectors having heretofore unrecognized characteristics are disclosed. These autoinjector embodiments exhibit exceptionally high injection depth precision in administering liquid medicaments to subjects and have design characteristics enabling the autoinjectors to be used by unskilled individuals under the stress of emergency trauma. 
         [0063]    The disclosure of all cited patents and publications referred to in the application are incorporated herein by reference. 
         [0064]    The above description is intended to enable the person skilled in the art to practice the invention. It is not intended to detail all of the possible variations and modifications that will become apparent to the skilled worker upon reading the description. It is intended, however, that all such modifications and variations be included within the scope of the invention that is defined by the following claims. The claims are intended to cover the indicated elements and steps in any arrangement or sequence that is effective to meet the objectives intended for the invention, unless the context specifically indicates the contrary.