Abstract:
A simple method and device enabling a unit dose from a reservoir is provided. The dose is drawn into the reservoir and is then expelled from the device by depressing a plunger. The plunger has features which divide the dose into discrete intervals. As the plunger is moved during delivery, the features on the plunger and features connected to a barrel interact to provide for intermittent stops to the delivery. Other aspects of the device provide for reduced dead space, safety and selective interconnection with other devices. Thus, the device divides the dose.

Description:
This application is continuation of U.S. patent application Ser. No. 13/922,779 filed Jun. 20, 2013 which is a continuation of U.S. patent application Ser. No. 12/864,685 filed Feb. 1, 2011, now abandoned, which is a National Stage Application under 35 U.S.C. §371 of PCT Application No. PCT/IB2008/001028, filed Jan. 30, 2008. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to delivery devices for delivering substances such as drugs, vaccines and the like, and more specifically relates to a drug delivery system and device having a system for dividing the dose into multiple sub-doses for injection through a needle. More specifically, the present invention relates to a method and apparatus for filling, dosing and disposing an intradermal delivery device using a needle sized for intradermal delivery and a dose divider for dividing the dose for multiple injections using the same needle. 
     BACKGROUND OF THE INVENTION 
     Traditionally, syringes are filled by inserting the needle into a vial. The dose is drawn from the vial, pulling the liquid drug dose from the vial into the syringe. The dosage is then expelled from the device by depressing the plunger. If it is desired to divide the total dose into discrete intervals, it must be accomplished manually, or via complicated and costly systems. In the actual usage of devices of this type, multiple doses are given to the same patient at various locations. With a conventional syringe the practitioner must stop depressing the plunger based on visual feedback (from the scale on the syringe). Consequently, it is difficult to perform the repeat dose injections with a high degree of accuracy and/or precision. Furthermore, intradermal injections which can be performed at repeated sites are difficult to perform and adding the difficulty of manually dividing the dose at each site has historically been difficult. Medication pens were developed to produce multiple injections, but are complicated and comprised of many parts. For example, a pen like device is described in U.S. Pat. No. 4,592,745. This pen device is complicated and performs multiple injections but with significant cost. Furthermore, medication pens are not readily adapted for use with fill at time of use systems, especially systems which require reconstitution steps. What is needed is a device and technique for expelling repeated doses from a fill able single syringe to perform multiple injections without having to solely rely on visual feedback from the scale of the syringe, or complicated devices with multiple parts. Furthermore, what is needed is a system that divides the dose that is compatible with conventional reconstitution practices. Attached are the results of a general background search which was conducted for the dose dividers. 
     SUMMARY OF THE INVENTION 
     In one embodiment the medication device having aspects of the invention uses a radially moving collar having a cantilevered beam which serves as a pawl. The collar is slidable from a first position to a second position on the flange of the syringe barrel. Furthermore, the plunger of the device is ratcheted with a plurality of spaced detents. In the first position the collar is positioned such that the pawls of the cantilevered beams do not interact with the ratchets of the plunger. A filling needle is attached to the syringe barrel. The first position is the filling position and allows the syringe to be used as a conventional syringe; however, in the usage of this device, the first position primarily serves to fill the syringe using a filling needle without interference by the ratchets. The filling needle is removed from the barrel and an injection needle is attached. The collar is moved to a second position. In the second position the collar is positioned such that the pawls of the cantilevered beams interfere with the detents of the plunger. This position allows the syringe to be used as a multiple repeat dose device. The practitioner inserts the needle into the patient and depresses the plunger. As the plunger is depressed, the pawls interact with the detents which provide for tactile feedback to the practitioner that the discrete intermediate dosage has been delivered. The practitioner then moves the needle to a new injection site and repeats the process. This process continues until the entire dose is delivered. 
     In another embodiment having aspects of the invention, the device uses a radially slidable component having a follower. The component is slidable from a first position to a second position on the flange of the syringe barrel or on an intermediate part snapped on the syringe flange. Furthermore, the sides of the plunger are grooved with a track having a plurality of spaced units having at least a stop portion. In some embodiments the track has an angled portion, and in others there is a capture portion. In alternate embodiments the track is along the contoured radial surface of the plunger, as the track. In yet another embodiment, the track is configured with units such that the follower is caught in retention areas. In alternate embodiments the plunger contains a plurality of followers and the track is on the slider, thus reversing the location of the features on the parts. In the first position the component is positioned such that the follower of the component does not interact with the tracks of the plunger. Optionally, a filling needle is attached to the syringe barrel. The first position is the filling position and allows the syringe to be used as a conventional syringe; however, in usage of this device the first position primarily serves to fill the syringe using a filling needle (or injection needle) without interference by the follower/tracks. The filling needle is removed from the barrel and an ID injection needle is attached. The component is moved to a second position. In the second position the component is positioned such that the follower of the component is riding in the track of the plunger, and is at the start of an injection cycle. In this case it is at the bottom of a unit. This is the discrete injection position and allows the syringe to be used as a multiple repeat dose device. The practitioner inserts the needle into the patient and depresses the plunger. As the plunger is depressed and begins to move distally, the follower travels along the track. As the follower travels along the angled portion of the track, the component is moved to a third position which is intermediate to the first and second position. At the cusp of the unit, the follower hits a stop point, which is the beginning of the adjacent unit, wherein the plunger is prevented from moving distally. The practitioner then moves the component from the third position to the second position which places the follower at the beginning of angled portion of the adjacent unit. The practitioner then moves the needle to a new injection site and repeats the process. This process continues until the entire dose is delivered. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  shows a perspective view of a delivery device having aspects of the invention. 
         FIG. 2  shows and Enlargement of Detail “A” of the delivery device of  FIG. 1 . 
         FIG. 3  shows a side view of the distal end of the device of  FIG. 1  with the shield of the device removed. 
         FIG. 4  shows a perspective view of a slider of the embodiment of  FIG. 1 . 
         FIG. 5  shows side view of a plunger of the embodiment of  FIG. 1 . 
         FIG. 6  shows a perspective view of a slider/clip assembly of the device of  FIG. 1 . 
         FIG. 7  shows a perspective view of a slider, clip and plunger assembly of the device of  FIG. 1 . 
         FIG. 7A  shows a perspective view of a clip and plunger assembly of an alternate embodiment having aspects of the invention. 
         FIG. 8  shows an enlarged side view of the plunger of  FIG. 5 . 
         FIGS. 9A and 9B  show an enlarged side view of Detail “B” and Detail “C” the plunger of  FIG. 5 , respectively. 
         FIG. 10  shows a cross-sectional view of the hub and barrel assembly of  FIG. 3  with the sheath and shield removed for clarity. 
         FIG. 11A  shows a perspective view of an alternate embodiment of a clip, plunger and barrel having aspects of the invention. 
         FIG. 11B  is a reverse perspective view of the components of  FIG. 11A . 
         FIG. 12  shows an enlarged side view of a plunger used in the embodiment of  FIGS. 11A-B . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As used herein, the term “proximal” and derivatives thereof, shall mean the end of an item or direction closest to the caregiver during use of the subject invention. The term “distal” and derivatives thereof, shall mean the end of an item or direction towards a patient during use of the subject invention. As used herein, the term “drug substance” and derivatives thereof shall mean any substance that is intended for injection into a patient, including, by way of non-limiting example, drugs, vaccines, therapeutics, and the like. It will be obvious to a person of skill in the art, and from the disclosure provided herein, that the subject invention is not limited or otherwise defined by the type or class of substance administered using the inventive injection device. 
     For many drug substances, it may be desirable to fill the delivery device at the point of, and immediately prior to use. In this situation, the delivery device is normally filled from a unit dose or multi-dose vial. A multi-dose vial may be more economical and it enables the user to fill the delivery device with the specific dose required. Alternatively, the syringe is pre-filled with a diluent. Alternatively, the syringe is pre-filled with the drug substance, and no filling step is required, and in this case the follower may be pre-set to be within the track. The multi-dose vial may be pre-filled with a liquid substance or with a dry substance. For example, it is now conventional to reduce certain drugs to a dry or powdered form to increase the shelf life of drugs and reduce inventory space. Multi-dose vials are typically sealed with an elastomeric stopper or septum. A needle on the delivery device may be used to pierce the stopper or septum and draw the drug substance from the vial into the delivery device, typically a syringe. The drug substance may then be administered using the delivery device, which is discarded after use, and the unit-dose vial may be stored for further use. Alternatively, the drug substance may be contained in a cryogenic vial. Furthermore, the cryogenic vial may be involved in a complex multi-step reconstitution procedure. 
     Standard methods for preserving the therapeutic and/or diagnostic substances, such as maintaining them in liquid or powder form in conventional vials for future use, may be used with the intradermal devices of the present invention. The substances for use with the device and method include vaccines and certain medicaments and drugs. Additionally, these substances can be used for diagnostic testing such as, for example, the Mantoux test to determine immunity status against tuberculosis and immediate hypersensivity status of Type I allergic diseases. Also, the substance preferably intradermally delivered in accordance with aspects of the methods and devices of the present invention is selected from the group consisting of drugs, vaccines and the like used in the prevention, diagnosis, alleviation, treatment, or cure of disease, with the drugs including Alpha-1 anti-trypsin, Anti-Angiogenesis agents, Antisense, butorphanol, Calcitonin and analogs, Ceredase, COX-II inhibitors, dermatological agents, dihydroergotamine, Dopamine agonists and antagonists, Enkephalins and other opioid peptides, Epidermal growth factors, Erythropoietin and analogs, Follicle stimulating hormone, G-CSF, Glucagon, GM-CSF, granisetron, Growth hormone and analogs (including growth hormone releasing hormone), Growth hormone antagonists, Hirudin and Hirudin analogs such as hirulog, IgE suppressors, Insulin, insulinotropin and analogs, Insulin-like growth factors, Interferons, Interleukins, Leutenizing hormone, Leutenizing hormone releasing hormone and analogs, Low molecular weight heparin, M-CSF, metoclopramide, Midazolam, Monoclonal antibodies, Narcotic analgesics, nicotine, Non-steroid anti-inflammatory agents, Oligosaccharides, ondansetron, Parathyroid hormone and analogs, Parathyroid hormone antagonists, Prostaglandin antagonists, Prostaglandins, Recombinant soluble receptors, scopolamine, Serotonin agonists and antagonists, Sildenafil, Terbutaline, Thrombolytics, Tissue plasminogen activators, TNF-, and TNF-antagonist, the vaccines, with or without carriers/adjuvants, including prophylactics and therapeutic antigens (including but not limited to subunit protein, peptide and polysaccharide, polysaccharide conjugates, toxoids, genetic based vaccines, live attenuated, reassortant, inactivated, whole cells, viral and bacterial vectors) in connection with, addiction, arthritis, cholera, cocaine addiction, diphtheria, tetanus, HIB, Lyme disease, meningococcus, measles, mumps,  rubella , varicella, yellow fever, Respiratory syncytial virus, tick borne japanese encephalitis, pneumococcus,  streptococcus , typhoid, influenza, hepatitis, including hepatitis A, B, C and E, otitis media, rabies, polio, HIV, parainfluenza, rotavirus, Epstein Barr Virus, CMV,  chlamydia , non-typeable  haemophilus, moraxella catarrhalis , human papilloma virus, tuberculosis including BCG, gonorrhoea, asthma, atheroschlerosis malaria,  E - coli , Alzheimers,  H. Pylori, salmonella , diabetes, cancer, herpes simplex, human papilloma and the like other substances including all of the major therapeutics such as agents for the common cold, Anti-addiction, anti-allergy, anti-emetics, anti-obesity, antiosteoporeteic, anti-infectives, analgesics, anesthetics, anorexics, antiarthritics, antiasthmatic agents, anticonvulsants, anti-depressants, antidiabetic agents, antihistamines, anti-inflammatory agents, antimigraine preparations, antimotion sickness preparations, antinauseants, antineoplastics, antiparkinsonism drugs, antipruritics, antipsychotics, antipyretics, anticholinergics, benzodiazepine antagonists, vasodilators, including general, coronary, peripheral and cerebral, bone stimulating agents, central nervous system stimulants, hormones, hypnotics, immunosuppressives, muscle relaxants, parasympatholytics, parasympathomimetrics, prostaglandins, proteins, peptides, polypeptides and other macromolecules, psychostimulants, sedatives, sexual hypofunction and tranquilizers and major diagnostics such as tuberculin and other hypersensitivity agents. 
       FIG. 1  shows a delivery device having aspects of the invention. Delivery device  10  includes a syringe  11  with a barrel  40  and plunger  30 . Plunger  30  is inserted into barrel  40  at the proximal end of device  10 . At the distal end of plunger  30  is a stopper which is used to seal barrel  40  to form a reservoir for the drug substance. At the proximal end of plunger  30  is push pad  32 . At the distal end of barrel  40  is attached needle assembly  12 . Needle assembly  12  is preferably comprised of hub  50  having a needle, sheath  80  and shield  70 . Shield  70  is removably attached to the distal end of needle assembly  12 . Preferably, needle assembly  12  is attached to barrel  40  via a threaded luer connection, however other connection methods may be used, inter alia luer slip or integral formation. Optional sheath  80  is slidably connected to hub  50  in order to protect the needle after use of the device. Alternatively, a conventional needle assembly may be used such as the type depicted in U.S. Pat. No. 6,494,865 to Alchas, the entire contents of which is incorporated by reference herein, or a standard hypodermic detachable needle. Alternatively, the needle may be integrally assembled onto or into the barrel  40 , such that it is a not removable barrel. Typically barrel  40  is plastic but it may be comprised of glass or any other material suitable for drug delivery. At the proximal end of delivery device  10  is dose divider  13 . Preferably, dose divider  13  includes a slider  20  and clip  60  which cooperate with plunger  30  to divide the entire dose contained within the syringe  11  into preselected increments. The construction and operation of the dose divider  13  is more readily seen in  FIG. 2  and is described below. 
     Now turning to  FIG. 2 , the dose divider  13  includes a slider  20  having a button  21  which is depressible by the health care professional. Slider  20  includes follower  28  which cooperates with track  100  of plunger  30  to divide the entire dose of the drug substance contained in the reservoir of the syringe into discrete unit doses. The unassembled slider is shown in  FIG. 4 . Slider  20  includes follower  28  which is preferably mounted on deflectable beam  27 . In this embodiment opening  26  serves to allow beam  27 , and thus follower  28  to deflect in the radial direction. Thus since opening  26  is a closed hole, beam  27  is a double supported beam. Alternatively, opening  26  could be formed such that beam  27  is a cantilevered beam. Alternatively, opening  26  could be omitted such that follower  28  is located on a rigid portion of slider  20 , and follower  28  and/or track  100  is elastically deformed and movement on a beam is not required. In this case, the parts would be sized dimensionally such that the interference of the parts was not so great to cause permanent deformation of the parts. Preferably, slider  20  also includes at least one rail  22  which cooperates with features on clip  60  to allow secure slidable engagement between the parts. Follower  28  is a cylindrical protrusion with a portion which is chamfered. Other profiles of protrusions may be used for follower  28 . Slider  20  is slidably engaged to clip  60  which is attached to barrel  40 . The engagement of slider  20  and clip  60  is shown clearly in  FIG. 6 . Rails  22  cooperate with opening  62  on the proximal side of clip  60  to provide a secure sliding connection between clip  60  and slider  20 . Other slidable connection means may be employed inter alia detents, holes and pins, and slots and followers. Clip  60  optionally includes radial opening  68  which receives a flanged portion of barrel  40 . Slider  20  with clip  60  attached to barrel  40  and slider  20  slidably engaged to clip  60 , slider  20  is able to be slid in a radial direction with respect to the longitudinal axis of barrel  40 , which would extend through barrel opening  69  on distal side of clip  60 . Furthermore, substantial proximal and or distal movement of follower  28  with respect to barrel  40  is substantially prevented by the design of slider  20 , clip  60  and connection methods employed. Preferably, crush ribs  67  of clip  60  are used to provide a secure connection between flange of barrel  40  and clip  60 , which substantially prevents relative movement in the barrel axial direction. Optionally, all of the aspects of Clip  60  described herein would be readily integrally formed into barrel  40 , however, for ease of using glass barrels, clip  60  is a separate component, however since the connection of clip  60  to barrel  40  is a connection which prevents any substantial distal or proximal movement of clip  60  to barrel  40 , they (clip  60 , barrel  40 ) function as one. Clip  60  optionally includes tactile ribs  61  for gripping by the health care professional. Clip  60  is attached to the distal end of barrel  40 , which preferably includes a flange. In this embodiment, Clip  60  is slid radially onto a flange of barrel  40  before insertion of plunger  30  into barrel  40 . Clip  60  also preferably includes tang  66  which serves to guide plunger  30  in use of dose divider  30 . Now referring back to  FIG. 2 , for clarity, slider  20  is only shown with follower  28  outside of track  100  of plunger  30 . Furthermore, this setting of slider  20  enables use of the syringe  11  as if there were no dose divider  13  attached. In this setting, follower  28  does not interact with track  100  to substantially hinder distal or proximal movement of plunger  30 . The dose dividing operation and cooperation of follower  28  and track  100  are further shown in  FIGS. 5, 8, and 9A-9B . 
     Shown in  FIG. 5  is the plunger  30 . Plunger  30  comprises distal end with stopper retention means  33 , and proximal end with push button  32 . Along an exterior surface of plunger  30  is track  100 . Track  100  is comprised of one or more discrete units  101  which each of which correspond to a unit dose. The distance between units on Plunger  30  is directly correlated to the amount of substance delivered for each unit. In one embodiment units are of equal size, thus providing equal volumetric unit doses. In an alternate embodiment, the units are differing sizes, thus providing varying volumetric unit doses. Optionally, track  100  includes on distal portion of plunger  30  a starting portion  107 . Optionally, track  100  includes on proximal portion of plunger  30  an ending portion  108 . These portions are described more fully below and in  FIG. 9A-B . In  FIG. 9B  one can see a detail of starting portion  107  of track  100 . The two positions of the follower  28  are represented in  FIG. 9B  by the position circles labeled A and B, labeled reference numerals  128  and  129 , respectively. Position A  128  represents a position of the follower that is outside of track  100 . In this position there is no interference of the movement of the plunger  30  by the follower  28 . To activate the dose dividing system the follower  28  is biased in the direct of the arrow labeled  118 , from position A  128  to position B  129 . In position B  129  the follower is within the track, and subject to the guidance of track  100 . More specifically the follower  28  is within the starting portion  107  of the track  100 ; however, it is not mandatory that the follower  28  start in the starting portion  107  of the track  100 , only that in order to use the device the follower  28  is within the track  100 . In  FIG. 9A  one can see a detail of finishing portion  108  of track  100  with angled wall  112 . Furthermore, the details of the unit  101  are described below and in  FIG. 8 . 
     Now turning to  FIG. 8 , the sides of plunger  30  comprise track  100  with a plurality of spaced units  101 . Preferably units  101  are “Z” shaped. Track  100  has angled portions  102  with angled wall portions  112 , which are skewed from the longitudinal axis of plunger  30 . Track  100  also comprises a plurality of abutting walls  110  which are a portion of track  100  which is substantially perpendicular to the longitudinal axis of plunger  30 . Track  100  also preferably comprises a plurality of detent tabs  104  which are aligned substantially parallel to the longitudinal axis of plunger  30 . In the first position the slider  20  is positioned such that the follower  28  of the slider  20  does not interact with the track  100  of plunger  30 . A filling needle is attached to the syringe barrel. The first position of slider as described above is the filling position and allows syringe  11  to be used as a conventional syringe; however, in usage of delivery device  10  in the first position of slider  20  primarily serves to fill the syringe using either a filling needle or needle assembly  12  without any substantial interference. Thus the plunger  30  may enter the barrel  40  along the length of the plunger  30  with no stoppages. If a filling needle is employed, the filling needle is removed from the barrel and needle assembly  12  is attached in preparation for the unit dosing, after the entire dose is drawn into the barrel  40 . In preparation for unit dosing, the slider  20  is moved to a second position in the direction of arrow  114 , upon which the follower  28  is now within track  100 . 
     Preferably, the follower  28  is positioned within the track at the starting position  107  (shown in  FIG. 9B ) which serves as an area to purge the syringe of air and set the plunger to the first unit dose, however, the follower may be placed directly in one of the plurality of units. The health care professional then moves the plunger  30  distally, in the direction of arrow  115 . The follower  28  is then directed to position “P0” at the proximal end of starting position  107  via the angled wall  112  of track  100 . The dose expelled during this phase is optionally discarded. Alternatively, the dose created during this phase is injected into the patient. When the follower reaches position “P0” labeled as reference numeral  119 , the follower  28  abuts abutting wall  110  and distal movement of the plunger is prevented. Position “P0” is the initial position of unit dosing which corresponds to position labeled “P1” identified by reference numeral  120  in  FIG. 8 . As distal movement of the plunger is prevented by abutting wall  110 , the health care professional depresses the slider button  21  to move slider  20  radially in the direction of arrow  114 , and reset the dose divider  13 . Preferably, follower  28  abuts detent tab  104  which provides resistance to follower  28 , thus the slider  20  to move in the radial direction; however, since follower  28  is flexibly mounted on beam  27  of slider  20 , movement in the radial direction is possible with deflection of the follower. As discussed previously, a designed deformation of the follower, track or combinations thereof would serve the same purposes. The resistance of the deflection of follower  28  over detent tab  104  is preferably selected so that it gives tactile feedback to the health care professional that the next dose is ready to be delivered. Optionally, the follower  28 , beam  27  and detent tab  104  dimensions are selected such that an audible click is heard by the health care professional. 
     As the follower  28  has now passed detent tab  104 , the follower is now at position labeled “P2” identified by reference numeral  121  at the distal end of unit  101 . Thus, this is the start of the unit  101  and the start of the delivery of a unit dose. The health care professional inserts the needle  56  into the patient and depresses the plunger  30 , preferably by push button  32 . As the push button  32  is depressed and the plunger  30  begins to move distally, and since the follower  28  is contained within track  100 , the follower  28  travels along the angled portion  102  of track  100 . Angled wall  112  biases follower  28  in the direction of arrow  116 , and therefore moves slider  120  in the direction of arrow  116 . Angled wall  112  serves to cam the follower into another position. At the approximate middle of the unit  101 , the follower is now at position labeled “P3” identified by reference numeral  122 , in which as the follower  120  travels along the angled portion  102  of track  100 , the slider  20  is radially moved proportionally to the distal movement of the plunger  30 , dependant on the angle of angled portion  102 . As the follower  28  reaches position labeled “P1′” identified by reference numeral  120 ′ at the proximal end of unit  101 , the follower  28  reaches a stop point which is the beginning of the adjacent unit  101 , wherein the plunger  30  is prevented from moving distally by the interaction of follower  28  and abutting wall  110 . Thus, the resetting of the dose divider process is repeated to bring the follower to position labeled “P2′” which is labeled with reference numeral  121 ′. The practitioner then moves the needle to a new injection site and repeats the process of injection. This process continues until the entire dose is delivered in a series of unit doses. Optionally, the last unit dose has the follower  28  traveling within the ending portion  108  (shown in  FIG. 9A ) of track  100 . In the ending portion  108  there is a large space of track  100  which allows follower  28  of slider  28  to move radially, which indicates to the health care professional that the last dose is delivered. The volumetric unit doses are comprised of the axial distance between positions P2 and P2′ multiplied by the area of the cross section of the barrel  40 . Preferably, the unit doses are equally spaced, although it would be possible to pre-select unit doses of varying volumes by selecting the spacing of P2 and P2″ for each unit  101  of track  100 . 
     Now turning to  FIGS. 11A-B  and  FIG. 12  which shows an alternate embodiment of dose divider which is similar to the dose divider as described above. The dose divider of this embodiment contains similar features and operates similarly to the dose divider as described above with a modification in the track and configuration of the unit and the addition of a biasing feature between the slider and the clip. Plunger  30  of this embodiment comprises track  200  having unit  201 . Furthermore clip  600  has slider  220  integrally formed therein. Clip  600  is slide onto flange  41  of barrel  40  as described above. Clip  600  also comprises stabilizer  255  which serves to stabilize plunger  30  and slider  220 , as well as secure the clip  600  onto the flange  41 , or combinations of these purposes. Slider  220  further comprises follower  280 . In this embodiment follower  280  is a ratchet-like protrusion on slider  220 , although may have other shapes, such as any of the embodiments described herein. Slider  220  is biased radially outward by biasing means  250 . In this embodiment biasing means  250  are a series of integrally molded leaf springs  251 . Biasing means  250  is designed to place a bias to slider  220  and therefore follower  280  in the operation of the device. Slider  220  also contains optional push button  210 . Although Slider  220  is integrally formed with clip  600 , slider  220  is able to be slid in a radial direction with respect to the longitudinal axis of barrel  40 . Furthermore, substantial proximal and or distal movement of follower  280  with respect to barrel  40  is substantially prevented by the design of slider  220 , clip  600  and connection methods employed. Optionally, all of the aspects of Clip  600  described herein would be readily integrally formed into barrel  40 , however, for ease of using glass barrels, clip  600  is a separate component, however since the connection of clip  600  to barrel  40  is a connection which prevents any substantial distal or proximal movement of clip  60  to barrel  40 , they (clip  60 , barrel  40 ) function as one. 
     Now turning to  FIG. 12 , as the follower  280  has three positions (P1, P2, P3) which will be described below. At the beginning of a unit dose, follower is located as position “P1.” In order to begin the dosing sequence, the health care professional depresses button  210  which applies a bias to slider  220  in the direction of arrow  114  and thus forces follower  280  to pass now passed detent tab  104 , the follower  280  is now at position labeled “P2” identified by reference numeral  121  at the distal end of unit  201 . The health care professional inserts the needle  56  into the patient and depresses the plunger  30 , preferably by push button  32 . As the push button  32  is depressed and the plunger  30  begins to move distally in the direction of arrow  115 , and since the follower  280  is contained within track  200 , the follower  28  travels along track  200 . However, since there is a bias applied by bias means  250  applied to the slider  220  and follower  280  in the direction in the direction of arrow  202 , and therefore moves slider  220  in the direction of arrow  202 . At the approximate middle of the unit  201 , the follower is now at position labeled “P3” identified by reference numeral  122 , in which as the follower  280  travels along track  200 , the slider  220  is biased by bias means  250  into the capture portion  202  of track  200 . As the follower  280  reaches position labeled “P1′” identified by reference numeral  120 ′ at the proximal end of unit  201 , the follower  280  reaches a stop point which is the beginning of the adjacent unit  201 , wherein the plunger  30  is prevented from moving distally by the interaction of follower  28  and abutting wall  110 . Thus, the resetting of the dose divider process is repeated to bring the follower to position in which the plunger may be moved distally as described above. The practitioner then moves the needle to a new injection site and repeats the process of injection. This process continues until the entire dose is delivered in a series of unit doses. Optionally, the last unit dose has the follower  280  traveling within the ending portion of track  200 , similarly as described in the previous embodiment. As in the previous embodiment, the volumetric unit doses are comprised of the axial distance between positions P2 and P2′ multiplied by the area of the cross section of the barrel  40 . Preferably, the unit doses are equally spaced, although it would be possible to pre-select unit doses of varying volumes by selecting the spacing of P2 and P2″ for each unit  201  of track  200 . 
     Now turning to  FIG. 7A  which shows an alternate embodiment of dose divider  1300  which uses a radially moving collar  160  having a cantilevered beam  270  which serves as a pawl having follower  280 . The collar  160  is slidable from a first position to a second position on the flange of the barrel  40 . Furthermore, the plunger  30  of the device is ratcheted with a plurality of spaced detents  1110 . Detents  1110  are formed into units  1010 . In the first position collar  160  is positioned such that the follower  280  of the cantilevered beams  270  do not interact with the detents  1110  of the plunger  30 . A filling needle is attached to the syringe barrel. The first position is the filling position and allows the syringe  11  to be used as a conventional syringe; however, in the usage of this device, the first position of collar  160  primarily serves to fill the syringe using a filling needle without interference by the dosing device  1300 . The filling needle is removed from the barrel and a needle assembly  12 . The collar  160  is moved to a second position on the flange of barrel  40 . In the second position the collar  160  is positioned such that the follower  280  of the cantilevered beams  270  interfere with the detents  1110  of the plunger  30 . This is the discrete injection position and allows the syringe  11  to be used as a multiple repeat dose device. The practitioner inserts the needle into the patient and depresses the plunger. As the plunger is depressed, the follower  280  interacts with the detents  1110  which provide for tactile feedback to the health care professional that the discrete intermediate dosage has been delivered. The health care professional then moves the needle to a new injection site and repeats the process. This process continues until the entire dose is delivered. 
     Now turning to  FIG. 3  and  FIG. 10 , the needle assembly  12  includes a needle cannula  56  located at the distal end of the hub  50 . In the embodiment depicted in  FIGS. 3 and 10 , needle  56  is inserted into hub  50  defined at that distal end of needle assembly  12  in a manner known to those skilled in the art. For example, needle  56  may be secured using a friction fit, snap fit, suitable adhesive, solvent weld, or other now known or hereafter developed means of securing a needle to a hub. Sheath  80  is slidably engaged to hub  50  by ribs  53 ,  54 . In one embodiment rib  54  has detents which cooperate with detenting means  82  to lock sheath  80  in at least one of two or more positions. In the intradermal embodiment of needle assembly  12 , hub  50  includes a specifically designed skin engaging surface  57 , which cooperates with needle  56 , extending from the distal end of surface  57  from 0.3 mm to 3 mm, preferably 0.5 mm to 1.5 mm. 
       FIG. 10  shows a cross section of needle assembly  12  attached to distal end of barrel  40 . Barrel  40  comprises collar  48  which contains internal threads  49  which engage with external threads  58  of hub  50 . Barrel  40  also comprises luer tip  46  which has a taper of “L” degrees. Typically “L” is approximately between 1.5 and 2.0 degrees. Preferably “L” is approximately 1.75 degrees. Hub  50  also has a corresponding taper within luer opening  51 . Preferably, luer opening  51  of hub  50  is adapted to only receive specialized luer tip  46  of barrel  40 . Luer opening  51  is designed to have a stepped opening, such that standard luer tips of standard syringes will not fully engage luer opening  51  and thus be un-usable with hub  50  of needle assembly  12 . Luer opening  51  is elongated and has a depth dimension of D1+D2. Preferably, dimension D2 is selected such that it is greater than the extension of standard luer tips. More preferably, dimension D2 is selected such that it does not allow engagement of threads  58  into standard luer lock barrels, but the fact that hub proximal end  51  protrudes at distance D2 from threads  58 , this does not allow engagement of the components. The interior diameter between D1 and D2 has a discontinuity  59  of dimension D3 such that a step is formed at the interface between D1 and D2. Typically D3 ranges from 0.05 mm to 0.15 mm, preferably approximately 0.1 mm. Typically D1 ranges from 6 mm to 10 mm, preferably approximately 8 mm. Typically D2 ranges from 4.5 mm to 8.5 mm, preferably approximately 6.5 mm. The location of the discontinuity  59  is selected such that effective use of hub  50  on standard luer tips is prevented. Preferably, the location of discontinuity  59  is at the same location as threads  58  along hub  50 . However, since the distal end of luer tip  46  is standard in nature, luer tip  46  allows attachment of a standard luer needle with no degradation in performance. As such, luer tip  46  allows both use of a standard luer needle for filling and hub  50  of specialized needle assembly  12  for injection. 
     Preferably inserted in the internal diameter of luer tip  46  is restrictor pin  92 . Restrictor pin  92  is substantially cylindrical and comprises a flattened portion  93  such that when restrictor pin  92  is inserted into internal diameter of luer tip  46 , the internal diameter is substantially but not completely obstructed to form flow path  91 . Preferably flow path  91  is sized to enable effective filling of delivery device  10  and prevent excessive shear forces on any substances delivered. Restrictor pin  92  also optionally comprises detent  94  which cooperates with optional detent rib  44  within luer tip  46  which serves to retain restrictor pin  92  in luer tip  46 . Other methods may be used to retain restrictor pin  92  in luer tip  46 . Hub  50  has dead space  90  which is included of the overall dead space of the system. It may be desirable to add a second restrictor pin within hub dead space  90 , as well. Alternatively, an elongated restrictor pin of similar design may be used in both spaces. Thus, restrictor pin  46  serves to reduce the overall “dead space” of delivery device  10 . 
     In use, a health care professional administering the injection will unwrap the protective packaging from the vial. The health care professional will then manually insert the medication device into the vial in preparation for aspiration of medication into barrel  40 . If supplied as separate components, the health care professional will then manually insert the syringe  11  into the filling needle in preparation for aspiration of medication. Alternatively, the filling needle and delivery device  10  are pre-assembled in a kit supplied with needle assembly  12 . In another embodiment, all three components (needle assembly  12 , syringe  40  and the filling needle are supplied in a kit. In another embodiment, syringe  40  is pre-filled with the drug substance and no filling is required. In another embodiment, syringe  40  is pre-filled with a diluent. Optionally, at this point, a diluent is injected in the medication vial. The healthcare professional then aspirates the syringe with the medication from the medication vial from syringe  11 . The health care professional will then manually remove the syringe  11  from the filling needle in preparation for administration of the injection. The needle assembly  12  is then attached to the device. In another embodiment, the filling needle is the same needle as the needle assembly  12 . Administration will, in one embodiment, involve pressing the skin engaging surface  57  of the hub  50  substantially perpendicular to a surface of the patient&#39;s skin. The first unit dose of the drug substance will then be injected using the plunger  30 . As the plunger is depressed the follower of the dose divider  13  follows the path of the track  100 , 200 . The follower then reaches stop point  122 . Upon completion of the unit dose, the health care professional withdraws the needle cannula from the patient&#39;s skin and prepares to reset the dose divider. Optionally the health care professional prepares the next injection site. The dose divider  13  is then reset in order to deliver the next unit dose, which entails moving the follower to start point  120 . Preferably, the reset involves pushing a button on the slider such that the follower is moved into the start point  120 . This cycle is then repeated for the number of units along the length of the plunger. Upon completion of the entire dose, the health care professional withdraws the needle cannula from the patient&#39;s skin and disposes the used injection device  10  in a suitable container. Prior to disposal, the health care professional optionally activates the shielding portion of delivery device by sliding sheath  80  distally. 
     As will now be understood, the delivery device having aspects of the invention may include a needle enclosure means which encloses or conceals the needle cannula tip following injection and which preferably cannot be retracted to prevent accidental needle contact or reuse. In the embodiment shown in  FIGS. 1 and 3 , a sheath  80  may be extended following injection and locked in place. The assembly includes sheath  80  which locks in the extended position, preventing contact with the needle by use of locking means  82 . Optionally arm  84  extends for the main portion of sheath  80  to aid in activation. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.