Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-07-26
2001-10-30
Seidel, Richard K. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S069000, C604S070000
Reexamination Certificate
active
06309371
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a device for delivery of medicament, and in particular to a jet injector with a skin tensioning probe to reduce the pressure at which the jet injector must eject the medicament for proper delivery.
BACKGROUND OF THE INVENTION
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 and enter the underlying tissues. These injectors typically have a nozzle assembly which has a barrel-like nozzle body having a medication holding chamber and an orifice through which a jet stream of medication is expelled from the chamber. Typically a plunger/piston actuated by an energy source, such as a coil spring, gas spring, or gas cartridge is used to expel the medicament.
Since at least the 1980s, the use of needleless injectors has become more desirable due to concerns over the spread of AIDS, hepatitis and other viral diseases caused by the possibility of accidental needle “sticks” from the conventional syringe and needle. One of the advantages associated with jet injectors is the absence of a hypodermic needle which removes apprehensions of healthcare workers and are superior in eliminating accidental disease transmission. Furthermore, 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 auto-injectors 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.
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 4,000 p.s.i., as measured by the force of the stream of fluid divided by the cross-sectional area of the stream of fluid.
Although this pressure is readily achievable with most injectors, there are some circumstances in which delivery under a reduced pressure is desirable. For instance, certain medications which contain molecules with long protein chains can be sheared and rendered ineffective when expelled at high pressures. Reduced pressure delivery is particularly useful in intradermal applications such as vaccine, specifically DNA vaccines in which a high force energy mechanism could disrupt the molecular structure. See “Intradermal DNA Immunization by Using Jet-Injectors in Mice and Monkeys,”
Vaccine
, 17:628-38, February 1999. Also, operation of the needleless injector at lower pressures can allow for a larger volume of medicament to be administered. 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.
Thus, there exists a need for ajet injector with an injection assisting probe to reduce the pressure at which the jet injector must eject the medicament for proper delivery.
SUMMARY OF THE INVENTION
The present invention is drawn to a needleless injection system for injecting a medical product, and in particular, to a portable hand held device for injecting a medical product into a patient. The present invention is additionally drawn to an improved probe that can be used with a needleless injector.
The needleless injector according to the present invention comprises a nozzle assembly having an fluid chamber for holding the medical product and an energy mechanism or energy means. The nozzle assembly has an orifice in fluid communication with the fluid chamber for allowing passage of the medical product in and out of the fluid chamber. The nozzle assembly is preferably removably connected and can be prefilled with a medical product if desired or can even be of a disposable type. A probe extends from the nozzle assembly to tension the skin and allow the jet to puncture the taut skin at a pressure that is substantially lower than the pressure normally needed to penetrate the skin.
In one embodiment, the probe is retractably disposed within the nozzle assembly such that when the injector is fired, the probe is forced out of the end of the nozzle assembly. This stretches the skin, allowing the drug to enter the skin more easily. The diameter of the probe tip is smaller than the diameter of the opening at the distal end of the injector so that the probe tip can move within the opening. After the device has completed the injection, the probe is forced back into the nozzle assembly by a retractable means or mechanism. An O-ring or a spring typically provides the force necessary to retract the probe.
Another aspect of the present invention includes the use of different retracting means. Either a membrane, O-ring seal and spring, or a coil spring may be used in any combination for this purpose.
In another embodiment, the probe is rigidly disposed in the nozzle assembly in a fixed position and extends outwardly therefrom.
In another embodiment, the probe is a metal cylinder inserted or molded in the injector to provide a large discharge channel length to orifice diameter ratio, i.e., in the range of at least about 6/1 to as high as 20/1 or even greater.
In another embodiment, the rigid probe nozzle assembly is assembled from two separate pieces that can be joined either by being snapped together or otherwise interlocked, including by friction fitting, by being joined with an adhesive or by being ultrasonically bonded together.
In yet another embodiment, the nozzle ratio of discharge channel length to orifice diameter is large, i.e., in the range of at least about 6/1 to as high as 20/1 or even greater, with a long and gradual approach angle of about 3 to 30 degrees.
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Berman Claude L.
DeBoer David M.
Giambattista Lucio
Lesch, Jr. Paul R.
Sadowski Peter L.
Medi-Jet Corporation
Pennie & Edmonds LLP
Seidel Richard K.
Thanh Lohn H.
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