U.S. patent application number 13/758907 was filed with the patent office on 2013-06-13 for prefilled syringe jet injector.
This patent application is currently assigned to ANTARES PHARMA, INC.. The applicant listed for this patent is Antares Pharma, Inc.. Invention is credited to Paul R. Lesch, JR..
Application Number | 20130150797 13/758907 |
Document ID | / |
Family ID | 36218390 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130150797 |
Kind Code |
A1 |
Lesch, JR.; Paul R. |
June 13, 2013 |
PREFILLED SYRINGE JET INJECTOR
Abstract
A jet injector that includes a prefilled syringe. The syringe
includes a fluid chamber that contains a medicament. The syringe
also has an injection-assisting needle, and a plunger is movable
within the fluid chamber. A housing is configured for allowing
insertion of the needle to a penetration depth. An energy source is
configured for biasing the plunger to produce an injecting pressure
in the medicament in the fluid chamber of between about 80 and 1000
p.s.i. to jet inject the medicament from the fluid chamber through
the needle to an injection site.
Inventors: |
Lesch, JR.; Paul R.; (Lino
Lakes, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Antares Pharma, Inc.; |
Ewing |
NJ |
US |
|
|
Assignee: |
ANTARES PHARMA, INC.
Ewing
NJ
|
Family ID: |
36218390 |
Appl. No.: |
13/758907 |
Filed: |
February 4, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13236120 |
Sep 19, 2011 |
|
|
|
13758907 |
|
|
|
|
11781832 |
Jul 23, 2007 |
8021335 |
|
|
13236120 |
|
|
|
|
PCT/US2006/002429 |
Jan 24, 2006 |
|
|
|
11781832 |
|
|
|
|
60709116 |
Aug 18, 2005 |
|
|
|
60645590 |
Jan 24, 2005 |
|
|
|
Current U.S.
Class: |
604/187 |
Current CPC
Class: |
A61M 5/30 20130101; A61M
5/3202 20130101; A61M 2005/2013 20130101; A61M 5/178 20130101; A61M
2005/206 20130101; A61M 5/28 20130101; A61M 5/484 20130101; A61M
5/46 20130101; A61M 5/2033 20130101 |
Class at
Publication: |
604/187 |
International
Class: |
A61M 5/178 20060101
A61M005/178 |
Claims
1-22. (canceled)
23. A prefilled syringe, comprising between about 0.02 mL and about
4 mL of a medicament contained in the prefilled syringe.
24. The prefilled syringe of claim 23, wherein the prefilled
syringe is configured for use in an injector device.
25. The prefilled syringe according to any of claims 23 and 24,
wherein the medicament is a hazardous agent.
26. The prefilled syringe of claim 25, wherein the hazardous agent
is atropine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/US2006/002429, filed Jan. 24, 2006, which
claims the benefit of U.S. Provisional Application Nos. 60/645,590,
filed Jan. 24, 2005, and 60/709,116, filed Aug. 18, 2005, the
content of each of which is expressly incorporated herein by
reference thereto.
FIELD OF THE INVENTION
[0002] The present invention relates to a jet injector, and more
particularly to a needle-assisted jet injector that uses a low jet
injection pressure.
BACKGROUND OF THE PRESENT INVENTION
[0003] Examples of needle-free injectors are described in U.S. Pat.
Nos. 5,599,302; 5,062,830; and 4,790,824. These traditional
injectors administer medication as a fine, high velocity jet
delivered under sufficient pressure to enable the jet to pass
through the skin. The pressure used to deliver the medication is
typically greater than approximately 4000 p.s.i. inside the
compartment that contains the medicament in the injector. Benefits
derived from such pressures, in addition to allowing injection
without needles, include the speed of the injection, the dispersion
of the injected medicament in the tissue and injection delivery
without impact from the resistance by the tissue where the
medicament is delivered.
[0004] Self-injectors or autoinjectors like the ones disclosed in
U.S. Pat. Nos. 4,553,962 and 4,378,015 and PCT Publications WO
95/29720 and WO 97/14455 are constructed to inject medicament at a
rate and in a manner similar to hand-operated hypodermic syringes.
The self-injectors or autoinjectors have needles that are extended
at the time of activation to penetrate the user's skin to deliver
medicament through movement of the drug container and related
needle. Thus the mechanism that provides the force to deliver the
medicament in self-injectors and autoinjectors is also used to
extend the needle and the drug container to cause the insertion of
the needle through the user's skin. The autoinjectors manufactured,
for example by Owen Mumford, thus use very low pressures to inject
the medicament, which is injected through a needle in a relatively
slow stream. The pressures applied in the medicament-containing
compartments of this type of device are very low, reaching a
maximum of around 60 p.s.i. and take around 6 seconds to inject 1
mL. These devices do not deliver of the medicament using jet
injection, so the medicament is delivered in a bolus at the tip the
needle, which typically penetrates the patient by typically at
least about 12 mm. When these low pressures and injection rates are
used with shorter needles, especially those that penetrate the
patient around 5 mm or less, there is a high incidence of leakback
of the injected medicament around the needle or through the hole in
the tissue created.
[0005] Prefilled syringes, such as those presently sold by Becton
and Dickinson as the BD Hypak.TM. are intended for slow speed,
manual or autoinjector injections. While prefilled syringes are
readily available, the manufacturing techniques employed result in
dimensional tolerances that traditionally have been considered too
loose for jet injectors since the syringe would need to withstand a
very sharp application of an elevated pressures sufficient to jet
inject the medicament. Additionally, prefilled syringes include
portions shaped to hold the needle and flanges for grasping for
injection by hand that result in features that can be susceptible
to breakage. Residual stresses that are present in the syringe
bodies also increase their fragility, which is one of the reasons
they have typically been considered too fragile for use in a jet
injector. Thus, jet injectors have typically used more robust
cartridges without features intended for handheld use, and which
are manufactured with tighter tolerances than typical prefilled
syringes.
[0006] An injector is needed that can reliable inject medicament to
a desired site without a substantial risk of the medicament leaking
back out from the patient's skin, at a fast speed substantially
without regard to tissue resistance, and preferably being able to
use a standard prefilled syringe.
SUMMARY OF THE INVENTION
[0007] The invention is related to a jet injector. The preferred
embodiment employs a prefilled syringe that is preferably prefilled
with a medicament prior to the assembly of the device. The syringe
has a container portion that defines a fluid chamber containing a
medicament. An injection-assisting needle is disposed at the distal
end of the chamber and has an injecting tip configured for piercing
an insertion location. The needle defines a fluid pathway in fluid
communication with the chamber for injecting the fluid from the
chamber into an injection site. The syringe also has a plunger that
is movable within the fluid chamber.
[0008] In this embodiment, a housing houses the prefilled syringe
and is configured for allowing insertion of the needle at the
injection location to an insertion point that is at a penetration
depth below the surface at the insertion location. A syringe
support supportively mounts the prefilled syringe to the housing,
and an energy source is configured to bias the plunger with a force
selected to produce an injecting pressure in the medicament in the
fluid chamber of between about 80 and 1000 p.s.i. This pressure
injects the medicament from the fluid chamber through the needle to
an injection site that is remote from the injecting tip. The
penetration depth and injecting pressure are preferably sufficient
to permit better medicament distribution than in autoinjectors and
to substantially prevent backflow of the injected medicament. In
the preferred embodiment, the injection rate is substantially
unaffected by tissue resistance.
[0009] The energy source, which preferably comprises a spring, is
preferably configured to produce the injecting pressure that
remains below about 500 p.s.i. and above about 90 p.s.i. during the
injection of the medicament. More preferably, the injecting
pressure remains at least at about 100 p.s.i. and up to about 350
p.s.i. during the injection of the medicament.
[0010] The preferred housing is configured for allowing insertion
of a portion of the needle to the penetration depth of between
about 0.5 mm and 5 mm below the surface at the insertion location.
In one embodiment, the penetration depth is between about 1 mm and
4 mm, and more preferably is less than about 3 mm. The injecting
pressure and penetration depth in some embodiments preferably are
sufficient such that the injection site is subcutaneous, although
other types of injection can be achieved in other embodiments. For
intramuscular injections, for example, the exposed portion of the
needle can be around 10 mm to 15 mm, for example, with a preferred
embodiment being around 13 mm.
[0011] The syringe has a distal portion of the prefilled syringe,
in which the injection-assisting needle is located, and a proximal
portion opposite the distal portion. The syringe support can be
configured to axial support the proximal portion of the pre-filled
syringe during the jet injection of the medicament, such that the
distal portion of the prefilled syringe is substantially
unsupported in an axial direction.
[0012] The prefilled syringe is preferably made of blown glass,
which can be formed on the injection-assisting needle, but is
usually formed and adhered to the needle. Additionally, the
preferred volume of the fluid chamber is about between 0.02 mL and
4 mL of the medicament.
[0013] The housing of the preferred embodiment comprises a
retractable guard that is movable between a protecting position and
an injecting position. In the protecting position, the needle is
disposed within the guard, but in the injecting position, the tip
of the needle is exposed for insertion to the insertion point. A
trigger mechanism can be operably associated with the energy source
for activating the energy source to jet inject the medicament. The
trigger mechanism is preferably configured for activating the
energy source after the retractable guard is retracted from the
protecting position, and most preferably once it is retracted to
the injecting position.
[0014] A syringe cushion can be provided in association with the
syringe support and the prefilled syringe to compensate for shape
irregularities of the pre-filled syringe and/or to cushion and
provide shock absorption to the syringe during the device firing.
In one embodiment, a ram that is biased by the spring against the
plunger to produce the injecting pressure is provided with a bell
portion on which the spring of the energy source is seated. The
bell portion defines a hollow interior configured for receiving the
prefilled syringe when the device is fired, such that the spring
surrounds the prefilled syringe.
[0015] The present invention thus provides a jet injection device
that offers better medicament distribution and can reliably use a
shorter needle that low pressure, non-jet injectors. Also, the
inventive jet injector can benefit from simplified manufacturing by
using a prefilled syringe, which traditionally is used for slow
injections.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a side view of a preferred embodiment of a jet
injector constructed according to the present invention, showing
the injector prior to injection;
[0017] FIG. 2 is a cross-sectional view thereof taken along plane
II-II;
[0018] FIG. 3 is a perspective view of a prefilled syringe for use
in the preferred embodiment
[0019] FIG. 4 is a perspective view of a syringe cushion of the
preferred embodiment;
[0020] FIG. 5 is a cross-sectional view of embodiment of FIG. 1,
showing the injector at the start of the jet injection of the
embodiment contained therein;
[0021] FIG. 6 is a graph showing the typical pressure present in
the polluted chamber that contains medicament in the preferred
embodiments during jet injection;
[0022] FIG. 7 is a side view of another embodiment of an injector
that is configured for using a narrow diameter prefilled
syringe;
[0023] FIG. 8 is a cross-sectional view thereof; taken on
VIII-VIII; and
[0024] FIG. 9 is a cross-sectional view of another embodiment of an
injector using a needle for intramuscular jet-injection.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Referring to FIGS. 1 and 2, a preferred embodiment of an
injector 10 has a housing 12 configured for allowing a user to
handle the injector 10. The housing 12 includes an outer housing
member 14 that substantially houses most of the components shown in
FIG. 2. A syringe support member 16 is housed within and mounted
with the housing 12. The syringe support member 16 is configured to
hold and position a prefilled syringe 18, which is shown in FIG. 3.
In the preferred embodiment, the syringe support member 16 is
substantially fixed to the housing 12, such as by snaps, an
adhesive, a weld, or another known attachment. The prefilled
syringe 18 has a container portion 20 that defines in its interior
a fluid chamber 22, which is prefilled with medicament to be
injected. At the distal end of the prefilled syringe 18 is an
injection-assisting needle 24. Needle 24 has an injecting tip 26
configured as known in the art to penetrate the tissue of a
patient, preferably the skin. A needle bore extends through the
needle 24, as known of the art. The bore is in fluid communication
with the medicament in the fluid chamber 22 and is open at the
needle tip 26 to inject the medicament.
[0026] At a proximal side of the fluid chamber 22, opposite from
the needle 24, is a plunger 28 that seals the medicament in the
fluid chamber 22. A syringe wall 30 preferably comprises a tubular
portion, preferably closed at a distal end and open at a proximal
end, to define the fluid chamber 22. Plunger 28 is slideably
received in the tubular portion. The prefilled syringe 20 is
configured such that when the plunger 28 is displaced in a distal
direction, the volume of the fluid chamber 22 is decreased, forcing
the medicament out therefrom and through the bore of needle 24.
[0027] At the distal end of the fluid chamber 22 is a needle hub
portion 32 to which the needle is mounted. A syringe flange 34
extends radially, preferably from the proximal end of the syringe
wall 30.
[0028] In the preferred embodiment, the syringe 18 has a syringe
body 36 that includes the flange 34 wall 30 and hub portion 32 is
of unitary construction. A preferred material for the syringe body
36 is glass, but other materials can be used in other embodiments.
A suitable prefilled syringe is the BD Hypak.TM., which is
available in various sizes and volumes and is sold prefilled with
medicament. The glass of the syringe body is adhered to the needle.
Typical medicaments and medicament categories include epinephrine,
atropine, sumatriptan, antibiotics, antidepressants, and
anticoagulants. Using a prefilled syringe facilitates handling of
the medicament when the injector is assembled, and there is an
extensive body of knowledge of how the medicaments keep and behave
in a prefilled syringe.
[0029] A syringe cushion 38, which is shown in detail in FIG. 4, is
preferably made of an elastomeric material or other resilient
material. A flange 40 of the syringe cushion 38 extends radially
and is disposed and serves as an interface between the distal side
of the syringe support member 16 and the syringe flange 34.
Elevated portions, such as nubs 42 extend proximately from the
cushion flange 40 and are configured and dimensioned to abut the
syringe flange 34.
[0030] Prefilled syringes that are manufactured by a blown glass
process can have significant dimensional tolerances and unevenness,
particularly in the glass body 36. The cushion 38 can serve to
accommodate the shape irregularities and to properly position and
locate the prefilled syringe 18 within the syringe support 16.
Typically, the axial thickness of glass blown syringe flanges on a
1 mL prefilled syringe is within about +0.5 mm. For a BD Hypak.TM.
1 mL standard prefilled syringe, the thickness of the syringe
flange 34 is 2 mm +0.5 mm or -0.4 mm, and in a 1 mL long
configuration BD Hypak.TM. syringe, the flange axial thickness is
about 1.65 mm.+-.0.25 mm. Other dimensional variations that occur
in typical glass prefilled syringes are in the internal and
external diameters of the tubular wall 30. These variations can be
accommodated by the resilient sleeve portion 44 of the syringe
cushion 38, which extends axially around the interior of the
syringe support 16. The syringe cushion 38 is preferably received
in the interior of the syringe support member and receives the
syringe body 36, preferably fitting snugly therein.
[0031] The sleeve portion 44 preferably has radially inwardly
extending protrusions 46 with a surface area and configuration
selected to allow the insertion of the prefilled syringe 18 therein
during assembly, but providing sufficient friction to maintain the
syringe 18 in place and to provide cushioning and shock absorption
during the firing of the injector. Outward protrusions 48 are also
provided on the sleeve portion 44, which can be received in
corresponding recesses of the syringe support 16 to prevent axial
rotation therebetween. Recessed areas 50 can be provided on the
interior and exterior of the syringe cushion 38 opposite
corresponding protrusions 48 on the opposite radial side of the
sleeve portion 44 if an increased wall thickness of the sleeve
portion 44 is not desired. In an alternative embodiment one or both
of the flange 40 and sleeve 44 of the syringe cushion 38 are
substantially smooth, substantially without any protrusions.
Preferably, the material and configuration of the syringe cushion
38 is also sufficient to entirely support the prefilled syringe 20
to withstand a firing force applied axially in a distal direction
on the plunger 28. Thus, the entire support for the prefilled 20
can be provided on the syringe flange 34, while the distal end of
the syringe 18 may itself be substantially unsupported in an axial
direction. This can help withstand the shock on the glass body 36
of the prefilled syringe 20 produced by the elevated pressures
within the fluid chamber 22.
[0032] To radially position the distal end of the prefilled syringe
18, the syringe support 16 preferably has a narrowed bore portion
51 that is preferably configured to abut the outside of the syringe
wall 30. This is especially beneficial when the needle is inserted
into the patient's skin. The narrowed bore portion can be made of a
resilient material, such as an elastomer, or it can be made
unitarily with the rest of the syringe support 16, preferably of a
plastic material.
[0033] A trigger mechanism 52 is preferably also housed within
housing 12. The trigger mechanism 52 includes an inner housing 54
that can be attached to the outer housing 14, such as by snaps, an
adhesive, a weld, or other known attachment. Trigger protrusions 56
extend inwardly from the proximal end of the inner housing 54 and
are resiliently biased outwardly. Trigger protrusions 56 are
received in a recess 58 of ram 60 in blocking association therewith
to prevent distal movement of the ram 60 prior to the firing of the
device. The ram 60 is urged towards the distal end of the injector
10 by an energy source, which preferably is a compression spring
52, although other suitable energy sources can alternative be used
such as elastomer or compressed-gas springs. A preferred type of
compression spring is a coil spring.
[0034] A trigger member of the trigger mechanism 52, such as a
latch housing 64, is provided exterior to the inner housing to
retain the trigger protrusions 56 in the blocking association in
the recess 58 to prevent premature firing of the injector 10. The
latch housing 64 is slideable inside the outer housing 14 with
respect to the inner housing 54, preferably in an axial direction,
and the latch housing 64 preferably surrounds the inner housing
54.
[0035] The housing 12 has a needle guard 66 that is moveable with
respect to the outer housing 14. The needle guard 66 is shown in
FIGS. 1 and 2 in a protecting position, in which the needle 24 is
disposed within the guard 66. The needle guard 66 is retractable,
preferably into the out housing 14, in a proximal direction to an
injecting position, in which the needle tip 26 and an end portion
of the needle 24 is exposed as shown in FIG. 5 for insertion into a
patient. In the preferred embodiment, the proximal movement of the
guard is prevented substantially at the injecting position.
[0036] The needle guard 66 is associated with the latch housing 64
such that when the guard 66 is displaced distally it slides the
latch housing 64 also in a distal direction to release the trigger
protrusions 56 from the recess 58. Preferably, the latch housing 64
has a latching portion 68 that abuts the inner housing 54 in an
association to bias and maintain the trigger protrusions 58
positioned in the blocking association with the ram 60 prior to the
firing of the device 10. When the latch is slid proximately by the
retracting of the guard 66 to the injecting position, the latching
portion 68 slides beyond the portion of inner housing 54 that is
contacts to flex the trigger protrusions 56 into the recess 58 of
the ram 60, allowing the trigger protrusions 56 to move radially
outwardly from the recess 58 and therefore from the blocking
association. When this happens, spring 62 biases the ram 60 against
plunger 28 to fire the jet injector. Latch housing 64 preferably
defines trigger openings 70 adjacent to latching portions 68, which
is configured to receive a portion of the inner housing 54, such as
the surface disposed radially outwardly from the trigger
protrusions 56.
[0037] The guard 66 is preferably resiliently biased distally
towards the protecting position by compression coil spring 72.
Also, the needle guard 66 has an axial opening 74 to allow the
needle 24 pass there through, and which may be sized according to
the type of injector desired. The construction of the present
embodiment allows a user to push the distal end of the injector 10
against the patient's skin, pushing the needle 24 into the skin at
an insertion location, substantially at the same speed as the
injector is pushed. Once the needle 24 is fully inserted to an
insertion point at a penetration depth, the trigger mechanism 56
fires the jet injection to an injection site.
[0038] Preferably, the prefilled syringe 18 and its needle 24 are
not shuttled forward automatically into the patient's skin, such as
by the firing energy source during the injection firing. The user
preferably gently pushes the entire device forward to insert the
needle, preferably retracting a guard against the skin in the
process. The prefilled syringe 18 preferably remains is a
substantially stationary within the housing 12, and is preferably
substantially fixed thereto. In this manner, the present invention
provides for a gentler treatment of the syringe during injection
that enables the use of a sufficiently powerful spring 62 or other
energy source to produce a jet injection without the risk of
damaging the relatively fragile and complex shapes of the prefilled
syringe, also allowing, for example, the injection of high
viscosity solutions, where the risk of breaking a syringe, such as
at the flange, is elevated in prior art injectors that shuttle the
syringe forward in the housing and into the patient. Residual
stresses are also often present in the glass bodies of prefilled
syringes, and this configuration reduces the additional stresses
imposed thereon during use, further protecting the syringe. Also,
misalignments in the prefilled syringe are also rendered
operationally less significant due to the gentle insertion of the
needle that is possible with this configuration.
[0039] Preferably, the injecting position of the guard 66 is such
that a predetermined length of the end of needle 24 is exposed from
the guard 66. In some embodiments, such as where the opening 74 is
of a sufficiently large diameter, the skin of the patient maybe
allowed to extend into the opening 74 when the device 10 is pressed
there against, and a needle that does not protrude beyond the
distal end of the guard 66 can be used while still penetrating the
skin to a certain depth. In most embodiments, the distance 76 by
which the needle tip 26 extends past the distal end of the guard 66
will be fairly close to the depth of the insertion of the
needle.
[0040] In the preferred embodiment, such as for subcutaneous
injection, the guard 66 is configured to allow insertion of the
needle to a penetration depth in the skin that is up to about 5 mm
below the skin surface. More preferably, the penetration depth is
less than about 4 mm, and in one embodiment is less than about 3
mm. Preferably, the insertion depth is at least about 0.5 mm and
more preferably at least about 1 mm. In another embodiment, the
distance 76 by which the needle extends past the guard 66 or the
distal surface of the guard 66 that contacts the skin is up to
about 5 mm, more preferably up to about 4 mm, and in one embodiment
up to about 3 mm. Preferably, extension distance 76 is at least
about 0.5 mm, more preferably at least about 1 mm, and most
preferably at least about 2 mm. In a preferred embodiment, tip 26
extends by a distance 76 of around 2.5 mm beyond the portion of the
guard 66 that contacts the skin in the injecting position.
[0041] In another embodiment, such as for intramuscular injection,
the injector is configured to allow the needle to be inserted into
the patient to a penetration depth in the skin, or alternatively
beyond the distal surface of the guard, by a distance of up to
about 15 mm. In one embodiment, this distance is about between 10
mm and 14 mm. In an embodiment for jet injection of epinephrine for
instance, a preferred penetration depth or distance beyond the
guard is between about 12 mm and 13.5 mm, and most preferably
around 12.7 mm. Jet injection with this length needle improves the
distribution of the medicament in the patient tissue compared to
non jet injection. Other exposed needle lengths can be selected for
jet injection to different depths below the skin, with a preferred
overall penetration length of between about 0.5 mm and about 20 mm.
In these embodiments, the needle guard is preferably configured for
retracting from a protecting position, preferably covering the
entire needle, to an injecting position, in which the desired
length of the end of the needle is exposed.
[0042] The spring 62 and the prefilled syringe 18 are configured to
jet inject the medicament. Thus, the spring 62 applies a force on
the plunger 28 that is sufficient to elevate the pressure within
the fluid chamber 22 to a level high enough to eject the medicament
from the needle 24 as a jet. Jet injection is to be understood as
an injection with sufficient velocity and force to drive the
medicament to locations remote from the needle tip 26. In manual
and autoinjector-type injections, in which the injection pressures
are very low, the medicament exits the needle tip inside the
patient and is typically deposited locally around the needle in a
bolus. On the other hand, with the present jet injection device 10,
the medicament is jet injected distally or in other directions,
such as generally radially by the elevated pressure jet, which
beneficially improves the distribution of the medicament after the
injection and keeps a large bolus from forming that can
detrimentally force the medicament to leak back out of the patient
around the needle or through the hole left behind by the needle
after it is removed.
[0043] Referring to the graph shown in FIG. 6, numeral 78
represents the point in time when device 10 is fired, and numeral
80 represents the point of completion of the medicament injection,
preferably when the plunger 28 hits the forward wall of the
container portion 20. Numeral 82 represents the initial and peak
pressure during the injection, and numeral 84 represents the final
and low pressure during the injection. Since the spring 62 of the
preferred embodiment has a linear spring constant and an
injection-assisting needle is used to puncture the skin before
commencing the injection, the pressure drops substantially linearly
from the start of the injection 78 until the injection is
completed. The final pressure 84 at the end 80 of the injection is
sufficiently elevated so that even at the end of the firing stroke
of ram 60, the medicament is still jet injected, and a very small
amount or none of the medicament is deposited in a bolus around the
needle tip 26.
[0044] Preferably the peak pressure during the injection is less
than about 1,000 p.s.i., more preferably less than 500 p.s.i., and
most preferably less than about 350 p.s.i. At the end 80 of the
injection, the pressure 84 applied to the medicament in the fluid
chamber 22 is preferably at least about 80 p.s.i., more preferably
at least about 90 p.s.i., and most preferably at least about 100
p.s.i. In one embodiment of the invention, the initial pressure 82
is around 330 p.s.i., and the final pressure is about 180 p.s.i.,
while in another embodiment the initial pressure 82 is about 300
p.s.i., dropping to around 110 p.s.i. at the end 80 of the
injection. The needles used in these embodiments are between 26 and
28 gage, and are most preferably around 27 gage, but alternatively
other needle gages can be used where the other components are
cooperatively configured to produce the desired injection.
Preferably, the components of the injector 10 are configured to jet
inject the medicament to a subterraneous injection site.
[0045] The amount of medicament contained and injected from fluid
chamber 22 is preferably between about 0.02 mL and 4 mL, and
preferably less than about 3 mL, and in the preferred embodiment is
around 1 mL. Larger volumes may also be selected depending on the
particular medicament and dosage required. Preferably, the
prefilled syringe is assembled into the remaining parts of the jet
injector 10 already containing the desired amount of medicament. In
a preferred embodiment, the prefilled syringe contains about 1 mL
of medicament.
[0046] Preferred injection rates are below about 0.75 mL/sec., more
preferably below about 0.6 mL/sec., and preferably at least about
0.2 mL/sec., more preferably at least about 0.3 mL/sec, and most
preferably at least about 0.4 mL/sec. Preferably, the injection of
the entire amount of medicament is completed in less than about 4
seconds, more preferably in less than about 3 seconds, and most
preferably in less than about 2.5 seconds. Preferably, the
medicament injection takes at least about 1 second, and more
preferably at least 1.5 seconds, and most preferably at least about
1.75 seconds. A preferred embodiment injects the medicament at
about 0.5 mL/sec., completing the injection of 1 mL in about 2
seconds.
[0047] U.S. Pat. No. 6,391,003 discloses several experimental
results of pressures that can be applied to medicament in a glass
cartridge, using 26 and 27 gage needles. The following table
illustrates injections with different peak pressures that can be
used with glass prefilled syringes:
TABLE-US-00001 Pressure and Time (sec.) to Inject 1 cc Pressure 26
Gauge needle 27 Gauge needle 150 p.s.i. 2.1 4.2 200 p.s.i. 1.9 3.9
240 p.s.i. 1.7 3.3 375 p.s.i. 1.4 3.1
It is foreseen that higher pressures and flow rates will be used
with shorter needle penetration into the patient skin to achieve
jet injections to a particular desired depth substantially without
medicament leakback.
[0048] It has been found that using the jet injection of the
present device, short needles can be used to inject medicament to
different parts of the skin, preferably subcutaneously,
substantially without any leakback. Using a needle that extends by
about 2.5 mm from the needle guard 66, a 27 gauge needle 24, and a
pressure in the fluid chamber 22 peaking at around 300 p.s.i. and
ending at around 100 p.s.i., resulting in a flow rate of about 0.5
mL/sec., 1 mL of medicament has been found to successfully be
injected without leakback in close to 100% of the tested
injections. Thus, the needle-assisted jet injector of the present
invention permits jet injection of the medicament using a very
short needle reliably regardless of the thickness of the patient's
skin or the patient's age, weight or other typical factors that
complicate non-jet injecting with short needles.
[0049] FIGS. 7 and 8 show another embodiment of the present
invention that uses a prefilled syringe that has a long, but
smaller-diameter configuration than the embodiment of FIG. 2. While
in the embodiment of FIG. 2, the firing spring 62 extends into the
bore of the prefilled syringe 18 during the firing stroke, the
narrower prefilled syringe 88 of injector 86 does not provide as
much space to accommodate a spring. Consequently, the ram 90 of
injector 86 includes a bell portion 92 defining a hollow interior
94 that is configured to receive the proximal end of the prefilled
syringe 88 and the syringe support 96 when the injector 86 is
fired. Similarly, a bell-receiving space 98 is defined around the
exterior of the prefilled syringe 88 and syringe support 96 to
receive the bell portion 92 during the firing. The bell 92 includes
a spring seat 100 extending radially outwardly and configured and
disposed to seat a compression spring 102. When the trigger
mechanism 56 is activated and the device 86 is fired, spring 102
acts against seat 100 to drive the ram 90 against plunger 104 to
jet inject the medicament from the fluid chamber 106. As a result,
after firing, the spring 102 radially surrounds the prefilled
syringe 88. The outer housing portion 108 is wider than outer
housing portion 14 of injector 10 to accommodate the bell portion
92 and larger diameter spring 102.
[0050] One available long configuration syringe with a 1 mL
capacity has a cylindrical syringe body portion with a diameter of
8.15 mm, which would typically be used in the injector of FIGS. 7
and 8, while one available shorter configuration syringe of the
same capacity has a cylindrical syringe body portion with a
diameter of 10.85 mm, which would be used in the injector of FIGS.
1 and 2. While the embodiment with a bell portion can be used with
wider/shorter syringes, I is preferred with prefilled syringes
having an outer diameter cylindrical wall of less than about 10 mm,
and more preferably of less than about 9 mm.
[0051] Injector 86 also includes a cap 110 fitted around the needle
guard 66, and associated with the outer housing 108 to prevent
retraction of the needle guard 66 and the triggering of the device
86. Additionally, the cap 110 seals off the needle tip 26 and can
be removed prior to using the device 86. The cap 110 is preferably
configured to fit over the needle guard 66 in a snap-fit
association therewith, such as by including a narrower diameter
portion 112 associated with an enlarged diameter portion 114 of the
needle guard 66.
[0052] Additionally, injector 86 employs a syringe cushion cap 116
that extends around the outside of the syringe flange 34 from the
syringe cushion 118 to help trap and retain the prefilled syringe
88. A cushion cap 122 is connected to the cushion 118 and is
preferably of unitary construction therewith. The cushion cap 122
abuts the distal end of the syringe body 120 to radially position
and hold the proximal end of the body 120 while the needle 24 is
being inserted into the patient. Similarly to the embodiment of
FIG. 2, the syringe holder 96 is associated with the housing in a
substantially fixed position, such as by mounting portion 124,
which traps protrusions 126 of the syringe holder.
[0053] Referring to FIG. 9, injector 128 has a needle guard 130
configured to retract further into the injector housing than the
injector of FIGS. 1 and 2 or FIG. 5 before the trigger mechanism 52
fires the jet injection. The injector in this figure is shown in a
position in which the trigger mechanism 52 is being released and
about to fire the injection. The distance 76 by which the needle
extends past the guard 130 or the distal surface of the guard 130
that contacts the skin preferably between about 12.5 and 13 mm. In
the preferred embodiments, the guard is preferably configured to
reextend to a protecting position after the device is fired and
removed from the patient, such as under the bias of spring 72, and
is locked in that position by locking members 132, as known in the
art to prevent reuse on the injector.
[0054] In other embodiments, the guard length, the location of the
guard injecting position with respect to the needle tip (including
the guard throw between the protecting and injecting positions),
and the length of the needle from the syringe body can be selected
to allow for shallower or deeper needle insertions before the
device is fired, providing lesser or greater distances 76,
respectively. Preferably, the guard is kept from sliding further
back than substantially at the firing position, to better control
in insertion depth into the patient.
[0055] The entire disclosure of U.S. Pat. No. 6,391,003 is hereby
incorporated herein by reference thereto.
[0056] While illustrative embodiments of the invention are
disclosed herein, it will be appreciated that'numerous
modifications and other embodiments may be devised by those skilled
in the art. For example, the features for the various embodiments
can be used in other embodiments, such as the needle and guard cap
of FIGS. 7 and 8, which can be applied to the embodiment of FIG. 1.
Therefore, it will be understood that the appended claims are
intended to cover all such modifications and embodiments that come
within the spirit and scope of the present invention.
* * * * *