Abstract:
Rapid, high-volume, intradermal infusion with minimal pain, is achived by applying an array of 10 to 30 hollow microneedles having a length of greater than 100 um to less than 1 mm into the skin of a patient, with a microneedle spacing of no less than 1.5 mm on average between adjacent microneedles, and pumping greater than 200 uL of fluid through the hollow microneedles at a rate of greater than 20 uL/min.

Description:
FIELD 
       [0001]    The present invention relates to hollow microneedle drug delivery devices. 
       BACKGROUND 
       [0002]    Transdermal patches have long been used for the administration of small molecule lipophilic drugs that can be readily absorbed through the skin. This non-invasive delivery route is advantageous for the administration of many drugs incompatible with oral delivery, as it allows for direct absorption of the drug into the systemic circulation, by-passing both the digestive and hepatic portal systems which can dramatically reduce the bioavailability of many drugs. Transdermal delivery also overcomes many of the challenges associated with subcutaneous injection by greatly reducing patient discomfort, needle anxiety, risk of accidental injury to the administrator and issues surrounding sharps disposal. 
         [0003]    Despite these many advantages, transdermal delivery of drugs is confined to classes of molecules compatible with absorption through the skin. Delivery of small molecule salts and therapeutic proteins are not typically viable with traditional transdermal delivery, as the skin provides an effective protective barrier to these molecules even in the presence of absorption-enhancing excipients. 
         [0004]    Microneedle (including microblade) drug delivery devices have been proposed based on a wide variety of designs and materials. Some are solid, e.g., with drug coated thereon, and others are hollow, e.g., with drug delivered from a reservoir. Some are made of metal, whereas others are etched from silicon material, and still others are made of plastics such as polycarbonate. 
         [0005]    The number, size, shape, and arrangement of the microneedles also varies considerably. Some have a single needle, while others, especially solid microneedles, have hundreds of needles per array. Most range in size from 100 microns to 2 mm. 
         [0006]    Microneedles have shown promise for delivery drugs intradermally and transdermally, particularly where a relatively small quantity of drug is needed such as in the case of vaccines or potent drugs. 
         [0007]    One of the desired benefits of microneedles is of course to replace, where appropriate, conventional hypodermic needles, which can cause anxiety and/or pain for many patients. There are also benefits to delivering some drugs, e.g., vaccines, into the skin rather than via intramuscular injection. However, microneedle delivery systems often have been seen as providing quite low rates of delivery, thus limiting the usefulness of such systems by requiring either small quantities of drug formulation to be used or long delivery times. For example, typical intradermal infusion using microneedles has been documented with slow infusion rates of less than 30 mcL/hour, and low infusion volumes less than 200 mcL. Some reports have also indicated significant pain if higher infusion rates are attempted. 
       SUMMARY 
       [0008]    It has now been found that the number of microneedles used and their density per unit area can produce much larger rates of delivery with virtually no pain induced. This offers for the first time the prospect for using microneedle arrays to replace hypodermic injections for rapid, painless delivery of injectable drug formulations. 
         [0009]    The method involves rapid, high-volume intradermal infusion with minimal pain by applying an array of 10 to 30 hollow microneedles having a length between 100 um to and 1 mm into the skin of a patient, with a microneedle spacing of no less than 1.5 mm on average between adjacent microneedles, and pumping greater than 200 uL of fluid through the hollow microneedles at a rate of greater than 20 uL/min. 
         [0010]    In preferred configurations the microneedle arrays of the present invention can deliver up to 1 mL or more of liquid formulation at the astonishingly high rate of 500 uL/min. Thus, for example, in contrast to other reported microneedle arrays that only deliver 100 uL at a slow rate of 10 uL per hour (not per minute), the present microneedle arrays can delivery a full 1 mL injection intradermally in about a minute or less. 
         [0011]    A microneedle array according to the invention will generally have from 13 to 20 microneedles, with a spacing density of 30 to 50 microneedles per cm 2 . In one embodiment 18 microneedles are used. Preferably the microneedles are spaced at least 2 mm between adjacent microneedles. 
         [0012]    The microneedles generally have a length of between 500 um and 750 um, and an average channel bore of 20 to 50 μm 2  cross-sectional area. 
         [0013]    The method of the invention can provide infusion whereby at least 750 uL of fluid is pumped through the microneedles. The fluid may be pumped through the hollow microneedles at a rate of at least 400 uL/min. The back pressure during pumping is usually no greater than 25 psi and generally maintained at 20 psi. 
         [0014]    The microneedles have an exit hole located on a sidewall of each microneedle. 
         [0015]    The microneedles typically penetrate from 100 um to 400 um into the dermis (hence the depth of penetration is not the full height of the microneedles themselves). 
         [0016]    Without wishing to be bound to any particular theory, many prior art microneedle arrays appear to use a large number of closely spaced microneedles, which may limit the volume and rate of fluid that can be accommodated within the dermal tissue. Trying to inject fluid rapidly with such devices may then either create undue back-pressure, fluid leakage back out of the skin during injection, needle array dislodgement, tissue doming, and/or significant pain. 
         [0017]    As used herein, certain terms will be understood to have the meaning set forth below: 
         [0018]    “Microneedle” refers to a specific microscopic structure associated with the array that is designed for piercing the stratum corneum to facilitate the transdermal delivery of therapeutic agents or the sampling of fluids through the skin. By way of example, microneedles can include needle or needle-like structures, including microblades, as well as other structures capable of piercing the stratum corneum. 
         [0019]    The features and advantages of the present invention will be understood upon consideration of the detailed description of the preferred embodiment as well as the appended claims. These and other features and advantages of the invention may be described below in connection with various illustrative embodiments of the invention. The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify illustrative embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Preferred embodiments of the invention will now be described in greater detail below with reference to the attached drawings, wherein: 
           [0021]      FIGS. 1A  and B are a perspective view of a microneedle array embodiment, also showing a closer view of an individual hollow microneedle. 
           [0022]      FIGS. 2A  and B show images of hairless guinea pig skin after hollow microneedle patch removal with staining 
           [0023]      FIGS. 3A  and B show images of a microneedle infusion site showing methylene blue 
           [0024]      FIG. 4  shows a comparative graph of naloxone blood levels versus time by delivery route. 
           [0025]      FIG. 5  plots pain of infusion versus certain infusion categories. 
           [0026]      FIG. 6  plots maximum infusion pressure versus certain infusion categories. 
           [0027]      FIG. 7  plots maximum infusion rate versus certain infusion categories. 
           [0028]      FIG. 8  plots infusion volume versus certain infusion categories. 
           [0029]      FIG. 9  plots pain of infusion versus maximum infusion pressure. 
           [0030]      FIG. 10  plots pain of infusion versus maximum infusion rate. 
           [0031]      FIG. 11  plots pain of infusion versus infusion volume. 
       
    
    
       [0032]    While the above-identified drawing figures set forth several embodiments of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale. Like reference numbers have been used throughout the figures to denote like parts. 
       DETAILED DESCRIPTION 
       [0033]    The invention will now be described with reference to the following non-limiting embodiment. 
       Microneedle Array 
       [0034]    A microneedle device  10  has a microneedle array  11  comprising a substrate  12  from which extend a plurality of eighteen microneedles  14 . Each microneedle  14  has a height of approximately 500 μm from its base  16  to its tip  18 . A hollow channel (not shown) extends through the substrate  12  and microneedle  14 , exiting at a channel opening  20  near the tip of the microneedle. This allows fluid communication from the back of the array (e.g., from a reservoir, not shown) through each microneedle  14 . The channel runs along a central axis of the microneedle  14 , but exits similar to a hypodermic needle on a sloping side-wall of the microneedle to help prevent blockage by tissue upon insertion. The channel has an average cross-sectional area about 20-50 μm 2 . 
         [0035]    The microneedles  14  are spaced apart so that the distance d between adjacent microneedles  14  is 2 mm. The disk shaped substrate  12  has an area of about 1.27 cm 2  and the microneedles  14  are spread out over an area of about 0.42 cm 2  as measured using the perimeter of the outermost rows of microneedles  14 . This gives a microneedle density of about 14 microneedles/cm 2 . 
         [0036]    The microneedle array  11  is made by thermocycled injection molding of a polymer such as medical grade polycarbonate, followed by laser drilling to form the channel of the microneedle. 
         [0037]    An array rim structure  22  is used for attaching to the microneedle substrate  12  a backing member (not shown) that incorporates an adhesive disk (not shown) (3M 1513 Medical Tape, 3M Corp, St. Paul Minn.) that will extent outward from the perimeter  24  of the substrate  12  to secure the hollow microneedle array  11  to the skin during infusion. The skin contacting surface of the entire microneedle device  10  including an adhesive ring will be about 5.5 cm 2 . 
         [0038]    The microneedle device  10  is typically applied to the skin using an external applicator (not shown). The applicator is designed, e.g., using a spring mechanism, to achieve a desired velocity so the microneedles will penetrate into the skin rather then merely deforming the skin. Once applied, the adhesive ring secures the microneedle device against the skin. Various applicator devices are disclosed in, for example, WO2005/123173, WO2006/055802, WO2006/05579, WO2006/055771, WO2006/108185, WO2007/002521, and WO2007/002522 (all incorporated herein by reference). 
         [0039]    Fluid to be delivered through the microneedle array can be contained in a reservoir (not shown) containing the fluid or by having the fluid pumped from an external source such as a syringe or other container that may be connected by, e.g., tubing or using a luer connector. Drug can be dissolved or suspended in the formulation, and typical formulations are those of the type that can be injected from a hypodermic needle. 
         [0040]    Any substance that can be formulated and delivered via hypodermic injection may be used, including any pharmaceutical, nutraceutical, cosmaceutical, diagnostic, and therapeutic agents (collectively referred to herein as “drug” for convenience). Examples of drugs that may be useful in injectable formulations with the present invention include but are not limited to ACTH (e.g. corticotropin injection), luteinizing hormone-releasing hormone (e.g., Gonadorelin Hydrochloride), growth hormone-releasing hormone (e.g., Sermorelin Acetate), cholecystokinin (Sincalide), parathyroid hormone and fragments thereof (e.g. Teriparatide Acetate), thyroid releasing hormone and analogs thereof (e.g. protirelin), secretin and the like, 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, Luteinizing hormone, Luteinizing hormone releasing hormone and analogs, Heparins, Low molecular weight heparins and other natural, modified, or synethetic glycoaminoglycans, M-CSF, metoclopramide, Midazolam, Monoclonal antibodies, Peglyated antibodies, Pegylated proteins or any proteins modified with hydrophilic or hydrophobic polymers or additional functional groups, Fusion proteins, Single chain antibody fragments or the same with any combination of attached proteins, macromolecules, or additional functional groups thereof, Narcotic analgesics, nicotine, Non-steroid anti-inflammatory agents, Oligosaccharides, ondansetron, Parathyroid hormone and analogs, Parathyroid hormone antagonists, Prostaglandin antagonists, 
         [0041]    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 Virsu, CMV, chlamydia, non-typeable haemophilus, moraxella catarrhalis, human papilloma virus, tuberculosis including BCG, gonorrhoea, asthma, atherosclerosis malaria,  E-coli , Alzheimer&#39;s Disesase,  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, and sexual hypofunction and tranquilizers. 
         [0042]    It will be understood that a wide range of hollow microneedle shapes can be used, such as cone shaped, cylindrical, pyramidal, truncated, asymmetrical, and combinations thereof. Various materials can also be used, such as polymers, metals, and silicon-based, and can be manufactured in any suitable way, such as injection molding, stamping, and using photolithography. The arrangement of the microneedles on the substrate can be of any pattern, such as random, polygonal, square, and circular (as viewed facing to the skin-contacting surface of the array). 
         [0043]    In addition to the above description, the following patent documents disclose microneedle devices, materials, fabrication, applicators, and uses that are useful or adaptable for use according to the present invention: U.S. Pat. No. 6,881,203; U.S. Pat. No. 6,908,453; U.S. 2005-0261631; WO2005/065765; WO2005/082596; WO2006/062974; WO2006/135794; U.S. 2006/048640; US provisional application 60/793611; U.S. 2007/064789; WO2006/062848; WO2007/002523; and US provisional application 60/793564. 
       Experimental 
       [0044]    The microneedle array device as described above in connection with the  FIG. 1A  was used for the following experiments and examples. 
       Animal Models and Skin Preparation 
     Hairless Guinea Pigs (HGP) 
       [0045]    Male HGPs were ordered from Charles River Laboratories (Wilmington, Mass.) under a 3M IACUC-approved animal use application and used according to that protocol. All animals used in this study weighed 0.8-1 kg. 
       Domestic Pigs 
       [0046]    Testing was conducted on female domestic pigs approximately 6-18 weeks old and weighing approximately 10-30 kg, and obtained under a 3M IACUC-approved animal use application. During infusion and throughout the studies, the pigs were maintained under anesthesia with isoflurane (2-5%) oxygen mix. The upper portion of the pig&#39;s hip was shaved first using a surgical clipper (clip blade #50) and then with a Schick 3 razor using a small amount of Gillette Foam shaving cream. After shaving, the site was rinsed with water, patted dry and then wiped with isopropyl alcohol (Phoenix Pharmaceutical, Inc., St. Joseph, Mo.). 
       Serum Naloxone Determination 
       [0047]    At each time point, 1.5-2 mL of whole blood was collected from the ear vein of the pig using a Vacutainer Collections Set (Becton Dickenson &amp; Co., Franklin Lakes, N.J.). The blood was allowed to set at room temperature for at least 30 minutes prior to being centrifuged at 1500 rpm for 10 minutes. After centrifugation, the serum was separated from the whole blood and stored cold until extraction. 
         [0048]    Room temperature serum samples were prepared using solid phase extraction cartridges (Phenomenex, Torrance, Calif.). Cartridges were conditioned with methanol (EMD Chemicals, Inc, Gibbstown, N.J.) and equilibrated with reagent grade water before loading with the serum samples. Serum was washed with 2 mL of 5% methanol in reagent grade water and naloxone eluted with 100% methanol. The eluent was collected in a 14 mL glass tube or a 16×100 mm tube and dried under 15 psi of nitrogen in a 37 C. water bath. 
         [0049]    Extracts were reconstituted with 5% acetonitrile/95% 0.1% formic acid (Alfa Aesar, Ward Hill, Mass.) in water, transferred to microcentrifuge tubes (Eppendorf, Westbury, N.Y.) and centrifuged at 14000 rpm for 10 minutes. 
         [0050]    Extracts were quantitatively analyzed using LCMSMS. Separation was achieved using an Agilent Eclipse XDB-C18 column (Agilent Technologies, Wilmington, Del.) in sequence with a Phenomenex C18 Guard Column (Phenomenex, Torrence, Calif.); the mobile phase was 0.1% formic acid and acetonitrile; the formic acid was ramped from 95% to 10% over 1 minute. A Sciex API3000 triple quad mass spectrometer (Applied Biosystems, Foster City, Calif.) running in positive ion mode using a Turbo IonSpray interface, was used to quantitatively monitor the product ions resulting from the following m/z transitions: 328.17→310.10 and 342.16→324.30. The linear range for naloxone was 0.1 to 100 ng/mL evaluated using a 1/x curve weighting. 
         [0051]    Various sizes of pigs were dosed, so to normalize blood naloxone levels with respect to pig weight, the blood naloxone levels were multiplied by a conversion factor of 62 mL blood/kg of pig weight and then multiplied by the weight of the pig at dosing (kg). Final results are plotted as μg naloxone/pig. 
       Depth of Penetration in HGPs and Pigs 
       [0052]    Based on the technical literature, and considering the size of the microstructures, it was estimated that a force of 0.004-0.16 N per microstructure is required for penetration of the stratum corneum. S. P. David, B. J. Landis, Z. H. Adams, M. G. Allen, M. R. Prausnitz. Insertion of microneedles into skin: measurement and prediction of insertion force and needle fracture force.  Journal of Biomechanics.  37:115-116 (2004). To ensure sufficient durability of the microstructures used herein, the array was pressed against a non-elastic surface; tip bending occurred when approximately 245 N of force was applied to the array. 
         [0053]    With the exception that it contains no sweat glands, porcine skin is generally regarded as being similar to human skin in thickness, hair density and attachment to the underlying tissue. If the depth of the epidermis in the pig used in these studies is approximately similar to that found in humans, depth of penetration data indicate that the likely depth of infusion for the hollow microneedle devices used herein (see  FIG. 1A ) is 180-280 μm (average 250 μm), a depth that could correspond to either the dermis or the epidermis which may affect the magnitude of back pressure encountered during infusion. It will thus be understood that although the microneedle height was about 500 μm, the actual depth of penetration was about half of that. 
         [0054]    The depth of penetration (DOP) experiments were completed in both HGPs and in domestic pigs; the results are summarized in Table I. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Summary of DOP Data collected on  
               
               
                 HGPs and Domestic Pigs 
               
             
          
           
               
                   
                   
                 DOP in HGPs 
                 DOP in Pig 
               
               
                   
                   
               
             
          
           
               
                   
                 Number of 
                 6 
                 6 
               
               
                   
                 applications* 
                   
                   
               
               
                   
                 Average (μm) 
                 210 μm 
                 250 μm 
               
               
                   
                 Standard Deviation 
                  30 μm 
                  40 μm 
               
               
                   
                 (μm) 
                   
                   
               
               
                   
                 % RSD 
                 15% 
                 16% 
               
               
                   
                   
               
               
                   
                 *each application consists of 1 array with 18 measured microstructures 
               
             
          
         
       
     
         [0055]    Fracturing of the microstructures was not observed in the force testing experiment nor were any broken needles observed following DOP testing.  FIGS. 2A and 2B  show an application site on an HGP after patch removal.  FIG. 2A  shows markings made by Rhodamine B dye that had been coated on the microneedles prior to application.  FIG. 2B  shows markings made by staining with methylene blue after a microneedle array was removed. Penetration of the stratum corneum by each of the 18 microstructures is evident from the pattern of methylene blue dots in  FIG. 2B . No blood was observed during or after application. 
         [0056]    In swine, several infusions of up to 1 mL were conducted using a sterile 5% dextrose or 0.001% methylene blue solution. Once the formulation had been delivered, the device was allowed to stay in place for up to 10 minutes while the back pressure on the system returned to pre-infusion levels.  FIG. 2  shows the results of an 8004 intradermal infusion of a 0.001% methylene blue formulation into pig. The skin is dry to the touch after patch removal; the deep blue of the infused formulation provides a visual assessment of the treatment. 
         [0057]      FIGS. 3A and 3B  show images of intradermal infusion of a 0.05% methylene blue formulation in pig at T=0 and T=9 min, respectively, post-patch removal. The skin was dry to the touch. 
         [0058]    Each blue spot on the skin corresponds to one of the eighteen hollow microstructures on the array. Although the dye appears somewhat smeared (diffused) after nine minutes, the blue stain remained, essentially unchanged 24 hours later although the wheal disappeared in under an hour. It is likely that the dye actually stained or precipitated in the tissue and, in this sense, is probably not an effective indicator of extended intradermal infusion patterns post infusion. 
         [0059]    Upon removal of the hollow microneedle patch after infusion, a small amount (1-3 μL) of formulation is typically observed on the surface of the skin. When this fluid is removed by gentle wiping with a tissue, no additional fluid is observed. A pinkish blotch, the size of the hollow microneedle array, is typically seen upon patch removal, but the blotch fades so as to become nearly indistinguishable within 5 minutes. A small dome, again approximately the size of the hollow microneedle array was observed on the pig skin as well. The dome yielded, but did not “leak”, under gentle pressure. The dome was resolved, both visually and by touch, within 40 minutes of removing the application patch. Observations of the application site 24- and 48-hours post application showed no evidence of erythema or edema. 
       EXAMPLE 1 
     High Volume Dextrose Infusion in Pigs 
       [0060]    High volume infusions have been demonstrated in domestic swine. Connected to the hollow microneedle array patch after application, the infusion system used with the swine employs standard medical equipment to provide delivery of the formulation. The hollow microneedle application patch is coupled to a Medfusion 3500 syringe pump (Smiths Medical, St. Paul, Minn.) via a commercial, pre-sterilized Polyethylene IV Extension Set (Vygon Corporation, Ecouen, France) that includes an in-line pre-sterilized, DTX Plus TNF-R pressure transducer (BD Infusion Therapy Systems, Inc, Sandy, Utah). The Medfusion 3500 pump is commonly used in hospital settings and has pre-set safety stop features. Pressure readings were recorded at a rate of approximately one measurement every two seconds. A 5% Dextrose, USP, solution for injection (Baxter Healthcare, Deerfield, Ill.) was used for infusion as received. The 0.001% methylene blue solution was prepared using sterile water and was filtered prior to administration. 
         [0061]    Testing was conducted on female domestic pigs approximately 6-18 weeks old and weighing approximately 10-30 kg, and obtained under a 3M IACUC-approved animal use application. During infusion and throughout the studies, the pigs were maintained under anesthesia with isoflurane (2-5%) and an oxygen mix. The upper portion of the pig&#39;s hip was shaved first using a surgical clipper (clip blade #50) and then with a Schick 3 razor using a small amount of Gillette Foam shaving cream. After shaving, the site was rinsed with water, patted dry and then wiped with iso-propyl alcohol (Phoenix Pharmaceutical, Inc., St. Joseph, Mo.). 
         [0062]    Up to 1 mL of 5% dextrose in water or up to 425 mcL of naloxone was delivered to the upper hip portion of the swine. Back pressure was monitored continually during the infusion to verify the absence of a leak in the infusion system. Typical infusion rate profiles utilized in the swine is provided in Table II, below. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 Summary of infusion conditions for 2 separate  
               
               
                 1 mL infusions of dextrose into pig 
               
             
          
           
               
                   
                 Max 
                   
               
               
                   
                 Rate 
                   
               
               
                 Infusion 
                 (μL/min) 
                 Infusion Rate Program in μL/min (time) 
               
               
                   
               
             
          
           
               
                 1003 μL dextrose 
                  50 
                  10 (5 min), 20 (7.5 min), 30(10 min),  
               
               
                   
                   
                  40 (7.5 min), 50 (4 min) 
               
               
                 1003 μL dextrose 
                  75 
                  10 (1 min), 25 (2 min), 50 (4 min),  
               
               
                   
                   
                  75 (approx 10 min) 
               
               
                  425 μL naloxone 
                 100 
                  10 (1 min), 25 (1 min), 50 (1 min),  
               
               
                   
                   
                 100 (duration) 
               
               
                  330 μL naloxone 
                  75 
                  10 (1 min), 25 (2 min), 50 (5 min),  
               
               
                   
                   
                  75 (duration) 
               
               
                   
               
             
          
         
       
     
         [0063]    After infusion, the hollow microneedle array was removed, leaving a small bleb under the skin. This bleb disappeared completely within 40 minutes. No site reaction was observed on the swine during observations through 48 hours post patch-removal. 
         [0064]    Back pressure was monitored and recorded continuously during the dextrose and methylene blue infusions. The maximum back pressure measured, along with infusion conditions, for three infusions are provided in Table III. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE III 
               
             
             
               
                   
               
               
                 Summary of infusion conditions for 2 separate  
               
               
                 1 mL infusions of dextrose into pig 
               
             
          
           
               
                   
                   
                 Max  
                   
               
               
                   
                 Max  
                 Back 
                   
               
               
                   
                 Rate 
                 Pressure 
                   
               
               
                 Infusion 
                 (μL/min) 
                 (psi) 
                 Infusion Rate Program in μL/min (time) 
               
               
                   
               
             
          
           
               
                 1003 μL 
                  50 
                  9.1 
                  10 (5 min), 20 (7.5 min), 30(10 min), 
               
               
                 dextrose 
                   
                   
                  40 (7.5 min), 50 (4 min) 
               
               
                 1003 μL 
                  75 
                  4.4 
                  10 (1 min), 25 (2 min), 50 (4 min), 
               
               
                 dextrose 
                   
                   
                  75 (approx 10 min) 
               
               
                  750 μL 
                 100 
                 16.2 
                  10 (1 min), 25 (1 min), 50 (1 min), 
               
               
                 methylene  
                   
                   
                 100 (duration) 
               
               
                 blue 
               
               
                   
               
             
          
         
       
     
       EXAMPLE 2 
       [0065]    Naloxone Infusion with Resulting PK Profile 
         [0066]    In an effort to better quantify the infusion, a 1 mg/mL commercial formulation of naloxone was infused into the pig using the hollow microneedle POC device. Naloxone is a μ-opioid receptor competitive antagonist used primarily to combat overdose of drugs such as heroin. Typically administered intravenously for fast response, naloxone is only about 2% bioavailable when administered orally. Naloxone is well-absorbed but is nearly 90% removed during first pass. Literature review indicates that the half life of naloxone in human adults is 30-81 minutes and considerably longer (approx 3 hours) in children. Naloxone is excreted in the urine as metabolites. 
         [0067]    Blood samples were collected from the ear vein of the pig before infusion and at specified time points up to 2 hours following infusion. The samples were prepared and analyzed to determine naloxone level in sera. For comparison, naive pigs were dosed with the same commercial naloxone formulation using either subcutaneous or intravenous injection. As with the intradermal infusion, blood samples were collected and analyzed for naloxone levels. 
         [0068]    Three different animals were used for the study comparing the PK profiles generated after hollow microneedle infusion, subcutaneous injection and IV injection. The pigs weighed between 10-22 kg at the time of dosing and ranged in age from 1.5-3 months. A commercial formulation (1 mg/mL) of naloxone hydrochloride (International Medication Systems, Ltd, So. El Monte, Calif.) was used for the infusion. Table IV shows the infusion profiles used with the naloxone administrations performed with the hollow microneedle device. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE IV 
               
             
             
               
                   
               
               
                 Summary of infusion conditions for naloxone infusion 
               
             
          
           
               
                 Total  
                   
                   
               
               
                 Volume 
                 Max Rate 
                 Infusion RateProfile in μL/min (time) 
               
               
                   
               
             
          
           
               
                 425 μL 
                 30  
                 (μL/min) 
                 10 (5 min), 20 (7.5 min), 30 (duration) 
               
               
                 200 μL 
                 75 
                 μL/min 
                 25 (1 min), 50 (2 min), 75 (duration) 
               
               
                 330 μL 
                 75  
                 μL/min 
                 10 (1 min), 25 (2 min), 50 (5 min), 75 (duration) 
               
               
                   
               
             
          
         
       
     
         [0069]    A comparative graph of naloxone blood levels versus time by delivery route is shown in  FIG. 4 . Pigs were also administered naloxone via subcutaneous injection. These pigs were similar in weight and age to those administered naloxone via the hollow microneedle device. These results indicate comparable delivery of naloxone via the hollow microneedle and subcutaneous injection. Based on blood samples collected up to 2 hours after initiation of the infusion, the bioavailability for the naloxone administered by the hollow microneedle technology is estimated to be 107+/−35% of that resulting from subcutaneous administration. 
       EXAMPLE 3 
       [0070]    Human Infusion Study with Dextrose 
         [0071]    Using the same apparatus described above, a demonstration of the high volume, high rate infusion was conducted on humans. During a human clinical trial, 28 subjects were administered 4-6 sequential hollow microneedle placebo infusions to their upper arms and/or upper legs. Back pressure was monitored continuously throughout the infusion. Using a 10-point pain scale (see  FIG. 4 ), each subject was asked to rate the pain associated with application and removal of the hollow microneedle patch; subjects were also asked to rate pain associated with infusion every 10 minutes during the infusion or at the end of infusion if the infusion ended in less than 10 minutes. 
         [0072]      FIGS. 5 ,  9 ,  10  and  11  plot data involving pain based on the following pain scale. 

 
         [0073]    Of the 125 infusions initiated, 46 infusions equal to or greater than 750 μL were administered. Different infusion rate profiles were used during the study, encompassing infusion rates from 10-433 μL/min. There was no statistically significant difference between the subjects&#39; perceived pain and the volume of the infusion. Table V summarizes, by category, highest infusion rates, infusion volume and maximum discomfort during infusion for those subjects receiving high volume (Category 3, &gt;750 μL) infusions. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE V 
               
             
             
               
                   
               
               
                 Summary of infusion parameters by category 
               
             
          
           
               
                   
                 # of 
                   
                 Avg Back 
                 Avg Vol 
                 Highest 
               
               
                   
                 Infusions 
                 Avg Pain 
                 Pressure (psi) 
                 μL 
                 Rate μL/min 
               
               
                   
               
             
          
           
               
                 Category 1 (0-250 μL) 
                 52 
                 1.40 +/− 0.77 
                 8.8 +/− 5.2 
                 133 +/− 60  
                 76 +/− 79 
               
               
                 Category 2 (250-750 μL) 
                 27 
                 1.96 +/− 1.66 
                 13.5 +/− 5.0  
                 427 +/− 148 
                 90 +/− 73 
               
               
                 Category 3 (750-1000 μL) 
                 46 
                 1.83 +/− 1.12 
                 13.37 +/− 4.20  
                 970 +/− 65  
                 126 +/− 93  
               
               
                   
               
             
          
         
       
     
         [0074]      FIGS. 5-8  provide a distribution summary of infusion parameters sorted by category.  FIG. 5  plots pain of infusion versus Category.  FIG. 6  plots maximum infusion pressure versus Category.  FIG. 7  plots maximum infusion rate versus Category.  FIG. 8  plots infusion volume versus Category. 
         [0075]    Table VI provides a summary of infusion parameters for all Category 3 infusions. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE V1 
               
             
             
               
                   
               
               
                 Summary of infusion parameters and pain scores for subjects receiving high volume infusions 
               
             
          
           
               
                   
                   
                 End rate 
                 Initial rate 
                 Max rate 
                   
                 MaxPress 
                 Total Infusion 
                   
               
               
                 Subj ID 
                 Site 
                 (μL/min) 
                 (mcL/min) 
                 (μL/min) 
                 Vol (μL) 
                 (psi) 
                 Time (min) 
                 Pain of Infusion 
               
               
                   
               
             
          
           
               
                 7 
                 LLT 
                 30 
                 10 
                 30 
                 800 
                 9.6 
                   
                 2 
               
               
                 7 
                 LUT 
                 35 
                 10 
                 35 
                 1000 
                 8.3 
                   
                 1 
               
               
                 7 
                 RUT 
                 46.7 
                 10 
                 46.7 
                 908 
                 7.3 
                   
                 1 
               
               
                 10 
                 LUT 
                 25 
                   
                 25 
                 767 
                 5.6 
                   
                 4 
               
               
                 10 
                 LLT 
                 58.3 
                 10 
                 58.3 
                 1001 
                 11.8 
                   
                 4 
               
               
                 10 
                 RUT 
                 58.3 
                   
                 58.3 
                 1001 
                 5.9 
                   
                 4 
               
               
                 11 
                 RLT 
                 30 
                 10 
                 30 
                 804 
                 16.9 
                   
                 3 
               
               
                 11 
                 LUT 
                 46.7 
                 10 
                 46.7 
                 1000 
                 12.9 
                   
                 2 
               
               
                 12 
                 LUT 
                 46.7 
                 10 
                 46.7 
                 1001 
                 7.8 
                   
                 4 
               
               
                 12 
                 LLT 
                 58.3 
                 10 
                 58.3 
                 1001 
                 8.6 
                   
                 4 
               
               
                 12 
                 RLT 
                 80 
                 10 
                 80 
                 1001 
                 13.1 
                   
                 5 
               
               
                 13 
                 LLT 
                 66.7 
                 166.7 
                 166.7 
                 1000 
                 13.3 
                   
                 3 
               
               
                 13 
                 RUT 
                 95 
                 25 
                 95 
                 1000 
                 9.2 
                   
                 3 
               
               
                 13 
                 LUT 
                 58.3 
                 16.6 
                 58.3 
                 1000 
                 8.5 
                   
                 3 
               
               
                 14 
                 RA 
                 58.3 
                 16.6 
                 58.3 
                 858 
                 14.0 
                   
                 1 
               
               
                 15 
                 LLT 
                 83.3 
                 83.3 
                 83.3 
                 1000 
                 14.0 
                   
                 2 
               
               
                 15 
                 RLT 
                 243.3 
                 83.3 
                 243.3 
                 1000 
                 10.0 
                   
                 2 
               
               
                 16 
                 LUT 
                 100 
                 83.3 
                 100 
                 1002 
                 13.8 
                   
                 2 
               
               
                 16 
                 LLT 
                 58.3 
                 83.3 
                 83.3 
                 1001 
                 15.3 
                   
                 1 
               
               
                 17 
                 RA 
                 50 
                 83.3 
                 83.3 
                 1000 
                 11.6 
                   
                 1 
               
               
                 17 
                 LT 
                 58.3 
                 83.3 
                 83.3 
                 1000 
                 14.1 
                   
                 2 
               
               
                 17 
                 RT 
                 58.3 
                 83.3 
                 83.3 
                 1000 
                 16.6 
                   
                 3 
               
               
                 18 
                 LUT 
                 83.3 
                 83.3 
                 83.3 
                 1001 
                 11.1 
                   
                 2 
               
               
                 18 
                 RUT 
                 100 
                 83.3 
                 100 
                 1001 
                 12.1 
                   
                 2 
               
               
                 19 
                 LLT 
                 83.3 
                 83.3 
                 83.3 
                 1000 
                 12.0 
                   
                 2 
               
               
                 19 
                 LUT 
                 100 
                 83.3 
                 100 
                 823 
                 14.3 
                   
                 1 
               
               
                 19 
                 RUT 
                 100 
                 83.3 
                 100 
                 1000 
                 4.3 
                   
                 1 
               
               
                 20 
                 LA 
                 66.7 
                 83.3 
                 83.3 
                 1001 
                 14.6 
                   
                 1 
               
               
                 20 
                 RA 
                 50 
                 83.3 
                 83.3 
                 1001 
                 14.6 
                   
                 1 
               
               
                 21 
                 LUT 
                 100 
                 100 
                 100 
                 1000 
                 15.2 
                 0:10:11 
                 2 
               
               
                 23 
                 LLT 
                 200 
                 100 
                 200 
                 840 
                 16.4 
                 0:05:30 
                 2 
               
               
                 22 
                 LLT 
                 166.7 
                 100 
                 166.7 
                 1000 
                 17.6 
                 0:08:30 
                 1 
               
               
                 22 
                 LMT 
                 183.3 
                 116.7 
                 183.3 
                 1001 
                 19.3 
                 0:07:12 
                 1 
               
               
                 24 
                 LUT 
                 266.7 
                 66.7 
                 266.7 
                 1000 
                 15.6 
                 0:06:30 
                 1 
               
               
                 26 
                 LMT 
                 250 
                 100 
                 250 
                 880 
                 15.3 
                 0:06:00 
                 1 
               
               
                 26 
                 LLT2 
                 116.7 
                 116.7 
                 116.7 
                 1002 
                 14.8 
                 0:10:50 
                 1 
               
               
                 26 
                 RLT 
                 100 
                 133.3 
                 133.3 
                 1001 
                 16.2 
                 0:12:10 
                 1 
               
               
                 28 
                 RUT 
                 200 
                 200 
                 200 
                 1000 
                 17.3 
                 0:07:06 
                 1 
               
               
                 28 
                 LUT 
                 150 
                 400 
                 400 
                 913 
                 16.6 
                 0:07:58 
                 1 
               
               
                 28 
                 LLT 
                 100 
                 433.3 
                 433.3 
                 1000 
                 10.4 
                 0:11:14 
                 1 
               
               
                 25 
                 RMT 
                 150 
                 100 
                 150 
                 970 
                 22.0 
                 0:09:00 
                 1 
               
               
                 25 
                 RUT 
                 180 
                 117 
                 180 
                 1000 
                 20.0 
                 0:08:48 
                 1 
               
               
                 27 
                 LUT 
                 117 
                 150 
                 150 
                 1000 
                 18.5 
                 0:11:00 
                 1 
               
               
                 27 
                 RUT 
                 183 
                 167 
                 183 
                 1000 
                 15.4 
                 0:07:00 
                 1 
               
               
                 27 
                 RLT 
                 200 
                 200 
                 200 
                 1000 
                 22.8 
                 0:07:38 
                 1 
               
               
                 27 
                 LMT 
                 117 
                 333 
                 333 
                 1000 
                 17.0 
                 0:10:17 
                 1 
               
               
                   
               
               
                 Key to site: 
               
               
                 1 - L/R = left/right; 
               
               
                 2 - L/U/M = lower/upper/mid; 
               
               
                 3 - T/A = thigh/arm 
               
             
          
         
       
     
         [0076]      FIGS. 9-11  plot the relationships between infusion pain and various infusion parameters for Category 3 (750-1000 μL) infusions only.  FIG. 9  plots pain of infusion versus maximum infusion pressure.  FIG. 10  plots pain of infusion versus maximum infusion rate.  FIG. 11  plots pain of infusion versus infusion volume. 
         [0077]    It will be understood that various unforeseen modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only be the claims set forth herein as follows.