U.S. patent application number 09/256310 was filed with the patent office on 2002-01-24 for needle assisted jet injector.
Invention is credited to BERMAN, CLAUDE L., DCBOER, DAVID M., LESCH JR., PAUL R., SADOWSKI, PETER L..
Application Number | 20020010456 09/256310 |
Document ID | / |
Family ID | 22257462 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020010456 |
Kind Code |
A1 |
SADOWSKI, PETER L. ; et
al. |
January 24, 2002 |
NEEDLE ASSISTED JET INJECTOR
Abstract
A needle assisted jet injector and method for jet injecting
medicament are disclosed. In one embodiment of the injector, the
needle is retractably located within an injector nozzle assembly.
Upon activation of the energy source, a portion of the needle
extends past the nozzle assembly and penetrates the outer layer of
skin to deliver the medicament via jet injection to a deeper
region. After activation, the needle retracts back into the nozzle
assembly. In another embodiment, the needle is fixed to the end of
the nozzle assembly. In both embodiments, the length of the portion
of the needle that penetrates the skin is less than 5 mm.
Inventors: |
SADOWSKI, PETER L.;
(WOODBURY, MN) ; DCBOER, DAVID M.; (WACONIA,
MN) ; BERMAN, CLAUDE L.; (ST.PAUL, MN) ; LESCH
JR., PAUL R.; (LEXINGTON, MN) |
Correspondence
Address: |
PENNIE & EDMONDS LLP
1667 K STREET NW
SUITE 1000
WASHINGTON
DC
20006
|
Family ID: |
22257462 |
Appl. No.: |
09/256310 |
Filed: |
February 24, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60096464 |
Aug 11, 1998 |
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Current U.S.
Class: |
604/511 |
Current CPC
Class: |
A61M 5/002 20130101;
A61M 5/30 20130101; A61M 2005/3247 20130101; A61M 5/24 20130101;
A61M 5/2466 20130101; A61M 5/349 20130101; A61M 5/3243 20130101;
A61M 5/20 20130101; A61M 5/326 20130101; A61M 5/3232 20130101; A61M
5/2425 20130101; A61M 5/288 20130101; A61M 5/3286 20130101; A61M
5/282 20130101; A61M 5/3202 20130101; A61M 2205/583 20130101 |
Class at
Publication: |
604/511 |
International
Class: |
A61M 005/30; A61M
031/00 |
Claims
What is claimed is:
1. An injection device comprising a housing, a nozzle assembly
defining a fluid chamber, having an opening for slidingly receiving
at least a portion of the needle and being removably associated
with the housing, a plunger movable in the fluid chamber, a trigger
assembly, an energy generating source operatively associated with
the trigger assembly so that movement of the trigger assembly
activates the energy source to move the plunger in a first
direction to expel a fluid from the fluid chamber, and a
retractable injection-assisting needle at a distal end of the
injector, said retractable injection-assisting needle comprising: a
needle tip located at a distal end of the needle with at least a
portion configured and dimensioned to slide through the nozzle
assembly opening; a discharge channel within the needle tip and
terminating in an orifice through which the fluid is expelled; a
body portion to direct fluid towards the discharge channel; a
plunger receptor configured and dimensioned to receive at least a
portion of the plunger; and a retraction element operatively
associated with the nozzle assembly; wherein the needle is located
within the nozzle assembly in a retracted position prior to
activation of the energy source; movement of the plunger in the
first direction upon activation of the energy source results in at
least a portion of the needle tip extending beyond the nozzle
assembly opening; and the retraction element returns the needle tip
to the retracted position after activation of the energy
source.
2. The injection device of claim 1, wherein the retraction element
is a resilient O-ring, a spring, or a flexible membrane which moves
to allow extension of the needle tip beyond the nozzle assembly
opening and then returns to its original position to return the
needle tip to its retracted position.
3. The injection device of claim 1, wherein the needle body has an
exterior surface which includes a ridge or recess for accommodating
the retraction element.
4. The injection device of claim 1, wherein a shoulder is disposed
between the needle tip and the needle body for accommodating the
retraction element.
5. The injection device of claim 1, wherein the needle tip has a
length of approximately 1-5 mm.
6. The injection device of claim 1, wherein the needle body has a
funnel-shaped interior tapering towards the discharge channel to
accelerate the fluid as it is discharged.
7. An injection device comprising a housing, a nozzle assembly
removably associated with the housing and defining a fluid chamber,
a plunger movable in the fluid chamber, a trigger assembly, and an
energy generating source operatively associated with the trigger
assembly so that movement of the trigger assembly activates the
energy source to move the plunger in a first direction to expel a
fluid from the fluid chamber, and a fixed injection-assisting
needle at a distal end of the injection device, said
injection-assisting needle comprising a body fixed to a distal end
of the nozzle assembly; and a discharge channel extending through
the needle body, in fluid communication at a first end with the
fluid channel, and terminating at a second end in an orifice
through which the fluid is expelled.
8. The injection device of claim 7, wherein the body has a length
of approximately 1-5 mm.
9. A method of delivering medicament to an injection site of a
patient, comprising the steps of: inserting a needle into a needle
insertion point, said needle having a length less than 5 mm and
being operatively associated with an orifice in a nozzle assembly
in fluid communication with an ampule chamber containing the
medicament; activating an energy mechanism; and coupling a pressure
wall member disposed and movable within the ampule chamber to the
activated energy mechanism to move the pressure wall member at a
speed sufficient to eject the medicament from the ampule chamber
through the orifice and needle under a pressure which is sufficient
to deliver a substantial portion of the medicament to the injection
site, wherein the needle insertion point is located more
superficial than the injection site.
10. The method of claim 9, further comprising the step of extending
a needle from a shield prior to inserting the needle into the
needle insertion point, said shield concealing the needle.
11. The method of claim 10, further comprising the step of
retracting the needle into the shield after the medicament has been
delivered to the injection site.
12. The method of claim 9, wherein the needle insertion point is
the epidermis layer of skin and the injection site is the
subcutaneous region.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to a device for delivery
of medicament, and in particular to a jet injector with a short
needle to reduce the pressure at which the jet injector must eject
the medicament for proper delivery.
BACKGROUND OF THE INVENTION
[0002] A wide variety of needleless injectors are known in the art.
Examples of such injectors include those described in U.S. Pat. No.
5,599,302 issued to Lilley et al., U.S. Pat. No. 5,062,830 to
Dunlap, and U.S. Pat. No. 4,790,824 to Morrow et al. In general,
these and similar injectors administer medication as a fine, high
velocity jet delivered under sufficient pressure to enable the jet
to pass through the skin.
[0003] As the skin is a tissue composed of several layers and the
injector is applied to the external surface of the outermost layer,
the delivery pressure must be high enough to penetrate all layers
of the skin. The layers of skin include, the epidermis, the
outermost layer of skin, the dermis, and the subcutaneous region.
The required delivery pressure is typically greater than
approximately 4000 p.s.i. (measured as the force of the fluid
stream divided by the cross-sectional area of the fluid
stream).
[0004] Although this pressure is readily achievable with most
injectors, there are some circumstances in which delivery of
medicament to the subcutaneous region under a reduced pressure is
desirable. For example, drugs that require a specific molecular
structural arrangement, such as a linear protein configuration, may
be rendered ineffective due to shear forces caused by the delivery
of the drug at high pressures that alter the structural arrangement
of the drug. As it is more difficult to deliver a large volume of
fluid at a high pressure compared to a small volume, using a lower
pressure facilitates delivery of a larger volume of fluid.
Furthermore, the lower pressure could make manufacturing an
injector device less expensive. The lower pressure would also
reduce adverse stresses on the device and result in a corresponding
increased useable device lifetime.
[0005] One of the advantages associated with jet injectors is the
absence of a hypodermic needle. Given the aversion to needles
possessed by some, the absence of a needle provides a psychological
benefit. Even devices that utilize conventional hypodermic needles
have attempted to capitalize on this psychological benefit. For
example, self-injectors or autoinjectors like the ones disclosed in
U.S. Pat. Nos. 4,553,962, 4,378,015 have retractable needles which
are hidden until activation. Upon activation, the needle extends
from the bottom of the device and penetrates the user's skin to
deliver medicament. As none of these devices involves delivery of
the medicament using jet injection, the medicament delivery
location is limited by the length of the needle. For example, if
delivery in the subcutaneous region is desired, the needle must be
long enough to reach the subcutaneous region. Furthermore, as
auto-injectors operate like syringes, the injection time is several
seconds or longer. In contrast, jet injectors typically inject in
fractions of a second.
[0006] Thus, there exists a need for a jet injector with a short
needle to reduce the pressure at which the jet injector must eject
the medicament for proper delivery.
SUMMARY OF THE INVENTION
[0007] The present invention relates to a needle assisted jet
injector. In one embodiment, the injection device includes a
housing; a nozzle assembly defining a fluid chamber, having an
opening for slidingly receiving at least a portion of the needle
and removably associated with the housing; a plunger movable in the
fluid chamber; a trigger assembly; an energy generating source
operatively associated with the trigger assembly so that movement
of the trigger assembly activates the energy source to move the
plunger in a first direction to expel a fluid from the fluid
chamber; and a retractable injection-assisting needle at a distal
end of the injector. The retractable injection-assisting needle has
a needle tip located at a distal end of the needle with at least a
portion configured and dimensioned to slide through the nozzle
assembly opening; a discharge channel within the needle tip and
terminating in an orifice through which the fluid is expelled; a
body portion to direct fluid towards the discharge channel; a
plunger receptor configured and dimensioned to receive at least a
portion of the plunger; and a retraction element operatively
associated with the nozzle assembly. The needle is located within
the nozzle assembly in a retracted position prior to activation of
the energy source. Movement of the plunger in the first direction
upon activation of the energy source results in at least a portion
of the needle tip extending beyond the nozzle assembly opening and
the retraction element returns the needle tip to the retracted
position after activation of the energy source.
[0008] The retraction element can be a resilient O-ring, a spring,
or a flexible membrane which moves to allow extension of the needle
tip beyond the nozzle assembly opening and then returns to its
original position to return the needle tip to its retracted
position. The needle body can have an exterior surface which
includes a ridge or recess for accommodating the retraction
element. A shoulder can be disposed between the needle tip and the
needle body for accommodating the retraction element. Preferably,
the needle tip has a length of approximately 1-5 mm.
[0009] In another embodiment, the injector has a non-retracting
fixed needle. The injection-assisting needle comprises a body fixed
to a distal end of the nozzle assembly and a discharge channel
extending through the needle body, in fluid communication at a
first end with the fluid chamber, and terminating at a second end
in an orifice through which the fluid is expelled. Preferably, the
body has a length of approximately 1-5 mm.
[0010] The present invention also relates to a method of delivering
medicament to an injection site of a patient. The method includes
the steps of: inserting a needle into a needle insertion point,
said needle having a length less than 5 mm and being operatively
associated with an orifice in a nozzle assembly in fluid
communication with an ampule chamber containing the medicament;
activating an energy mechanism; and coupling a pressure wall member
disposed and movable within the ampule chamber to the activated
energy mechanism to move the pressure wall member at a speed
sufficient to eject the medicament from the ampule chamber through
the orifice and needle under a pressure which is sufficient to
deliver a substantial portion of the medicament to the injection
site. The needle insertion point is located more superficial than
the injection site.
[0011] The method preferably includes the steps extending a needle
from a shield prior to inserting the needle into the needle
insertion point and then retracting the needle into the shield
after the medicament has been delivered to the injection site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view of a needle assisted jet
injector according to the present invention;
[0013] FIG. 2 is a cross-sectional view of the needle on the jet
injector of FIG. 1;
[0014] FIG. 3 is a perspective view of the needle of FIG. 2;
[0015] FIG. 4 is an enlarged cross-sectional view of the jet
injector of FIG. 1 with the needle in the retracted position;
[0016] FIG. 5 is an enlarged cross-sectional view of the jet
injector of FIG. 1 with the needle in the extended position;
[0017] FIG. 6 is a perspective view of a second embodiment of the
needle according to the present invention;
[0018] FIG. 7 is a partial cross-sectional view of a jet injector
according to the present invention with the needle of FIG. 6 in the
retracted position;
[0019] FIG. 8 is a partial cross-sectional view of a jet injector
according to the present invention with the needle of FIG. 6 in the
extended position;
[0020] FIG. 9 is a cross-sectional view of another embodiment of
the present invention with a flexible member as the retraction
element and the needle in the retracted position;
[0021] FIG. 10 is a cross-sectional view of the embodiment of FIG.
9 with the needle in the extended position;
[0022] FIG. 11 is a cross-sectional view of a two piece nozzle
assembly having a fixed needle;
[0023] FIG. 12 is a cross-sectional view of another embodiment of a
two piece nozzle assembly having a fixed needle;
[0024] FIG. 13 is a cross-sectional view of another embodiment of a
two piece nozzle assembly having a fixed needle; and
[0025] FIG. 14 is a schematic expressing a pressure-time curve for
a jet injector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] For convenience, the same or equivalent elements of the
invention of embodiments illustrated in the drawings have been
identified with the same reference numerals. Further, in the
description that follows, any reference to either orientation or
direction is intended primarily for the convenience of description
and is not intended in any way to limit the scope of the present
invention thereto.
[0027] As shown in FIG. 1, a jet injector 10 according to the
present invention comprises a nozzle assembly 12 attached to a
housing 14. As used in this application, the term distal shall
designate the end or direction toward the front of jet injector 10.
The term proximal shall designate the end or direction toward the
rear of the injector. The term longitudinal designates an axis
connecting nozzle assembly 12 to jet injector 10, and the term
transverse designates a direction substantially perpendicular to
the longitudinal direction including arcs along the surface ofjet
injector 10, or nozzle assembly 12.
[0028] Nozzle assembly 12 can be threadably connected to housing 14
such that it can be readily attached and detached. Alternatively,
other known structures for mounting or attaching two components can
be utilized as well to detachably mate nozzle assembly 12 to
housing 14. In this manner, injector 10 can be reused with various
nozzle assemblies that may contain different medications of
different doses either together or at different times. For
instance, nozzle assembly 12 can be prefilled with medication and
disposed of after each use. Further, a medication filling device
such as a coupling device can be used to fill the fluid chamber
with medication. U.S. Pat. No. 5,769,138 to Sadowski et al., the
disclosure of which is herein incorporated by reference, is
directed to such a coupling device.
[0029] A trigger assembly 16 is located at the proximal end of
housing 14. Trigger assembly 16 activates and triggers an energy
source or energy generating means 18 which forces medicament out of
nozzle assembly 12. Energy source 18 can be a coil spring, a gas
spring, or a gas propellant.
[0030] According to a first embodiment of the present invention,
nozzle assembly 12 has an injection assisting needle 20 movable
within nozzle assembly 12. Needle 20 will be discussed in detail
after first describing the other components of injector 10. The
nozzle assembly 12 includes a nozzle member 22 having an opening 24
at the distal end, preferably having a diameter of about 0.04-0.4
inches or any other suitable diameter that would allow for the
introduction of injection assisting needle 20 therein. Nozzle
member 22 includes a cylindrical fluid chamber 26 terminating at
the distal end in a right circular cone 28. Cone 28 can be a convex
cone (as shown), a right circular cone, or any other suitable
configuration. A plunger 30 having a pressure wall contoured to
cone 28 is positioned to slide within fluid chamber 26. Plunger 30
can include sealing means such as one or more O-rings or the like
(not shown) that are formed around its outer periphery to provide a
seal, or the plunger itself can be a seal, as described in U.S.
Pat. No. 5,062,830, the disclosure of which is incorporated herein
by reference. The plunger can also include additional sealing means
at spaced intervals to provide a better seal.
[0031] Plunger 30 is connected to a ram 32 which in turn is
connected to energy source 18. Alternatively, ram 32 can be
integrally formed with an energy mechanism if desired. An inertia
mass 34 is connected to or integrally formed with ram 32 near the
end of ram 32 closest to plunger 30. Inertia mass 34 can be
removably connected to ram 32 such that the mass can be adjusted to
accommodate different types of injections, taking into
consideration, for instance, the viscosity of the medication, the
initial pressure build up desired, the strength of energy source
18, and the depth of injection penetration, etc. Inertia mass 34
cooperates with ram retainer 36 to limit the distance that ram 32
can travel toward nozzle assembly 12. One important safety aspect
of this feature is that ram 32 cannot become a dangerous projectile
if injector 10 is fired when nozzle assembly 12 is not present.
[0032] Trigger assembly 16 includes a trigger extension 38 having a
trigger engaging notch 40. Trigger extension 38 is attached to the
end of ram 32, for example, by a threaded engagement. Trigger
assembly 16 also comprises a latch housing sleeve 42 fixedly
attached to an actuating mechanism 44. Actuating mechanism 44 is
shown as a threaded coupling that operates by rotation movement.
Alternatively, the actuating mechanism of the provisional
application of DeBoer et al. filed Jul. 27, 1998 and entitled
"Loading Mechanism for Medical Injector Assembly", the disclosure
of which is herein incorporated by reference, can be used. Latch
housing sleeve 42 has a throughbore dimensioned to allow passage of
trigger extension 38. Latch housing sleeve 42 further has a
plurality of sidewall openings 46 dimensioned to allow passage of
balls or ball bearings 48. A tubular button 50 having one open end
and a closed end is telescopingly positioned with latch housing
sleeve 42 as shown. Button 50 has a circumferential or annular
groove 52 formed on an inner wall 54 thereof to allow portions of
the balls 48 to engage groove 52 when trigger assembly 16 is in the
fired position, i.e., not engaged with trigger extension 38 (not
shown). Balls 48 are positioned so that they are substantially
flush with an inner side wall surface 56 of latch housing sleeve 42
to allow trigger extension 38 to pass through latch housing sleeve
42. A latch ball retaining cup 58 is telescopingly positioned
within button 50. A compression spring 60 is positioned between the
cup 58 and button 50 to bias button 50 and cup 58 away from each
other in the axial direction.
[0033] The structure of injection assisting needle 20 is best seen
in FIGS. 2 and 3. Needle 20 has a plunger receptor 62 at the
proximal end which is configured to accommodate plunger 30 as it
slides within fluid chamber 26. Although plunger receptor 62 can be
of any shape conforming to the exterior profile of plunger 30, it
is preferably conical. A needle inner wall 64 is contoured to
narrow like a funnel to a needle discharge channel 66 to accelerate
the fluid as it is discharged. Needle discharge channel 66 extends
to a discharge orifice 68 at the distal end of needle 20. Needle
discharge orifice 68 has a diameter of 0.004 to 0.012 inches.
Preferably, the diameter is 0.005 to 0.0075 inches.
[0034] The outer periphery of needle 20 can be of varied geometries
such that it fits within fluid chamber 26 of nozzle assembly 12.
Advantageously, needle 20 has a conical body section 70 which
narrows gradually or tapers towards a cylindrical body section 72
of smaller circumference. Preferably, a shoulder 74 is positioned
to separate a needle tip 76 from cylindrical body section 72.
Needle tip 76 is also cylindrical, but has a smaller circumference
than cylindrical body section 72 such that needle tip 76 can fit
within and extend through opening 24 of nozzle assembly 12.
However, cylindrical body section 72 of needle 20 has a
circumference such that shoulder section 74, existing at the
transition between cylindrical body section 72 and needle tip 76,
prevents cylindrical body section 72 from existing within opening
24. The length of needle tip 76 from its end to shoulder 74 is
approximately 1 to 5 mm. Thus, needle tip 76 will penetrate the
skin to a depth less than 5 mm. It should also be noted that
although needle tip 76 is shown having a single bevelled end at a
45.degree. angle, needle tip 76 can have any shape that penetrates
the skin.
[0035] As shown in FIGS. 4 and 5, needle 20 is positioned coaxially
and retractably within the distal end of fluid chamber 26 such that
when injector 10 is fired, needle tip 76 extends out opening 24 of
nozzle assembly 12 at a speed sufficient to penetrate the outer
layer of skin. By inserting needle tip 76 to a depth less than 5
mm, only the epidermis of the skin is penetrated and the pressure
needed to deliver the medicament to the desired region by jet
injection is lower than that would otherwise be needed. While
syringes and auto-injectors delivery the medicament to the depth of
the needle, the needle assisted jet injector according o the
present invention delivers the medicament to a depth deeper than
the length of the needle. This depth can include any region of the
skin and beyond including intradermal, subcutaneous, and
intramuscular.
[0036] To provide a seal between needle 20 and fluid chamber 26,
needle 20 includes a sealing means such as an O-ring(s) 78 or the
like formed around the outer periphery of needle 20 and
accommodated by slot 80. In an alternative embodiment shown in FIG.
6, needle 120 itself is the seal. Thus, slot 80 is not needed.
Needle 120 also differs from needle 20 in that cylindrical body
section 72 is absent so that conical body section 70 terminates at
shoulder 74.
[0037] FIG. 5 illustrates injection assisting needle 20 in its
extended position. Needle tip 76 extends beyond the distal end of
nozzle assembly 12. Shoulder 74 abuts the bored out inner section
of nozzle opening 24 to prevent needle 20 from extending beyond
needle tip 76. A retraction element 82, in this embodiment a
spring, is compressed to provide a recoil force once the medicament
is expelled so that needle tip 76 will retract back into nozzle
opening 24. Needle 20 preferably has a ridge 84, the distal surface
of which provides an annular area for the compression of retraction
element 82. Alternatively, a washer can be used instead of the
ridge 84 to contain O-ring 78 and compress the retracting mechanism
during operation.
[0038] FIGS. 7 and 8 show needle 120 of FIG. 6 with nozzle assembly
12 in which retraction element 82 is a resilient O-ring or other
like material known to those skilled in the art. When an O-ring is
used as retraction element 82, it can also act as a sealing
mechanism, and for this reason the O-ring is preferred. The
interior of needle 120 is similar to that of needle 20. FIG. 7
illustrates needle 120 in the retracted condition, before expelling
medicament, and FIG. 8 shows the extended condition during which
medicament is expelled. Similar to embodiments previously
described, this embodiment functions to extend the needle tip 76
beyond nozzle opening 24 and penetrate the outer layer of the
patient's skin during operation. Also, similar to embodiments
previously described, needle 120 also preferably has ridge 84
around the proximal end to provide a surface which compresses the
resilient material when the injector is triggered.
[0039] Another embodiment of the present invention, shown in FIGS.
9 and 10, uses a flexible member 86 as the retraction element. FIG.
9 illustrates the neutral condition before expelling the
medicament. Flexible membrane 86 spans between walls 88 of nozzle
assembly 12 which define fluid chamber 26 for holding medicament.
Similar to embodiments previously described, the distal end of
nozzle walls 88 act to conceal needle tip 76 until the injector is
fired. Needle 220 is attached to flexible membrane 86 by any
conventional means known to those skilled in the art. Preferably,
needle 220 is integrally attached to flexible membrane 86 with an
adhesive. FIG. 10 shows needle 220 in its extended position where
the needle tip 76 extends beyond the end of walls 88 such that
needle tip 76 penetrates the outer layer of skin to allow injection
and deliver of the medicine at reduced pressure.
[0040] Other embodiments of the present invention relate to
injectors with a fixed needle, i.e. a non-retracting needle that
permanently extends beyond the nozzle assembly. Both a one-piece
and a two-piece nozzle assembly with a fixed needle can be used and
are contemplated by this invention.
[0041] FIGS. 11 and 12 show embodiments of the present invention
with a two piece nozzle assembly with a fixed needle 320. A first
section 90 of nozzle assembly 12 has needle 320 at the distal end
and can either be attached internally or externally to a second
section 92 to form nozzle assembly member 12. Although any
conventional attaching means can be used, such as solvent or
adhesive bonding, FIG. 11 shows a preferable friction-fitting or
snapping attaching means 94 for both internal and external
attachment of first section 90 and second section 92. FIG. 12 shows
a preferable ultrasonic bonding means 96 of attachment. Although
ultrasonic bonding features 96 can be placed at any location to
attach the two pieces, preferably, the ultrasonic bonding features
96 are along the distal end at the interface between first and
second sections 90, 92 to facilitate ease of manufacturing.
[0042] Another embodiment of a multi-piece nozzle assembly with
fixed needle 320 is shown in FIG. 13. The nozzle assembly consists
of nozzle member 22 having an opening 24 designed to receive a
tubular insert to create fixed needle 320. Although FIG. 13 shows a
multi-piece nozzle assembly, fixed needle 320 can be made to be
integral with nozzle assembly 12.
[0043] A significant advantage of the needle assisted jet injector
according to the present invention is that it allows for a lower
pressure to deliver the medicament. In this regard, administering
an injection using either a fixed or retractable needle requires
less energy and force than conventional jet injector devices. FIG.
14 shows a pressure-time curve for a jet injector. The peak
pressure at point c is the pressure needed to penetrate the skin
and point d and beyond is the pressure at which ajet stream of
medicament is delivered. Needle assisted jet injectors do not need
to achieve as high as peak pressure as conventional jet injectors
because the outer layer of skin is penetrated by the needle.
Therefore, a lower peak pressure can be used to deliver the
medicament to the desired region. It is also possible that a lower
steady state pressure can be used to deliver the jet stream after
the needle and the jet injection have reached the desired
region.
[0044] Experimentation has confirmed that the needle assisted
injector according to the present invention can operated using a
lower generating energy source and still maintain the quality of
the injection. Specifically, experimentation has shown that a
higher percentage of successful injections can be achieved with a
needle assisted jet injector having a needle that penetrates the
skin to a depth of 1 mm and 20 lb. energy generating means as with
a conventional needleless jet injectors having 55 lb. energy
generating means. Similar results have been achieved with needles
that penetrate 1-3 mm and energy generating sources providing 20
lbs. and 40 lbs. of force.
[0045] Another advantage of the needle assisted jet injector
according to the present invention is the decreased injection time
compared to syringes or auto-injectors. As previously discussed,
auto-injectors and syringes have injection times of several seconds
or more. During this injection time, the quality of the injection
can be comprised due to any number of factors. For example, the
patient could move the syringe or auto-injector prior to completion
of the injection. Such movement could occur either accidently or
intentionally because of injection-related pain. In contrast, the
needle assisted jet injector, like otherjet injectors, has an
injection time around 0.25 seconds. The short injection time
minimizes the possibility of compromising the quality of the
injection.
[0046] While it is apparent that the illustrative embodiments of
the invention herein disclosed fulfil the objectives stated above,
it will be appreciated that numerous modifications and other
embodiments may be devised by those skilled in the art. Therefore,
it will be understood that the appended claims are intended to
cover all such modifications and embodiments which come within the
spirit and scope of the present invention.
* * * * *