WO2004028601A1

WO2004028601A1 - Systems for controlling injection rate through a hypodermic needle

Info

Publication number: WO2004028601A1
Application number: PCT/US2003/030733
Authority: WO
Inventors: Ralf V. Bitdinger
Original assignee: Biogen, Inc.
Priority date: 2002-09-26
Filing date: 2003-09-26
Publication date: 2004-04-08
Also published as: AU2003277065A1

Abstract

A system to control the flow of fluid through a hypodermic needle is provided. The system includes an elongated needle having an injection end, a fluid receiving end opposite the injection end, and a fluid pathway extending between the receiving end and the injection end. The system also includes a member (12) positioned at the fluid receiving end of the needle. The member is provided with a passage in communication with the pathway of the needle and through which fluid is introduced into the pathway of the needle. The passage includes a diameter (d) relatively smaller than (D) that of the pathway, so that fluid directed therethrough and exiting the injection end of the needle can be dispensed at a substantially uniform rate. A method for controlling the rate of hypodermic injection is also provided.

Description

SYSTEMS FOR CONTROLLING INFECTION RATE THROUGH A HYPODERMIC NEEDLE

Technical Field This invention relates to the hypodermic needles, and more particularly, to hypodermic needles having means to control the injection rate through the needles.

Background Art Certain treatments require the hypodermic injection of a dose of a therapeutic compound or compounds into patients on a long-term basis, whereas other treatments only require the hypodermic administration of the therapeutic compound or compounds in the event of an emergency. In either of the situations, there is a certain benefit in self-injection, i.e. the injection of a therapeutic dose outside of any hospital or care facility, in the absence of a health care professional by the patient, a non-medical family member or a friend. The benefits of self-injection include, among other things, the prompt treatment of an on-setting symptom, the convenience of home use, thereby avoiding a doctor's visit, and cost savings, as it does not involves a health care professional.

Generally, therapeutic compounds can be injected through a needle and a syringe. The use of a needle and a syringe, however, can be threatening and intimidating to a patient, for example, the nature of the exposed needle. In addition, the patient may find the needle and syringe difficult to handle, problematic in maintaining sterility, and complicated in use. As a result, auto-injectors are being marketed to help reduce injection anxiety and needle phobia, while making the self-injection process user-friendly.

An auto-injector is a device that, while accommodating a drug-filled syringe and an injection needle, performs, by the push of a button, the automatic insertion of the injection needle into the tissue, followed by the automatic injection of the drug. Most auto-injectors are spring-driven, i.e. one or more internal coil springs exerting the forces needed to perform needle insertion and subsequent injection of the therapeutic compound. Auto-injectors are available for the administration of subcutaneous (SQ) and intramuscular (IM) injections. While the SQ injectors make use of a short and thin SQ needle, IM injectors operate with a longer and thicker IM needle.

At present, certain auto-injectors operate with a prefilled syringe having an attached needle, while some are designed to operate with a syringe having a standard Luer tip to which a common injection needle can be coupled. It should be noted that prefilled syringes are syringes that act as both, a storage container for a therapeutic compound and an injection device, so as to eliminate the common vial.

The processing of a prefilled syringe, commonly manufactured from pharmaceutical grade borosilicate glass, includes the lubrication of the syringe barrel with, for instance, silicone. This lubrication can act to minimize the amount of friction generated as a rubber piston at the tip of a syringe plunger moves along the length of the syringe barrel. However, there can be variations in the lubrication process, which can result in variability of the forces required to drive the plunger and the rubber piston along the length of the syringe barrel. As a result, the rate of injection through the needle may not be uniform. Accordingly, it would be desirable to provide a hypodermic needle which can be used with various syringes and auto-injectors, and which permits a substantially uniform rate of injection through the needle.

Summary of the Invention The present invention, through various embodiments, provides a system which includes a physical restriction of fluid flow through the fluid path within the needle to control the rate of injection.

The present invention, in accordance with one embodiment, provides a system having an elongated needle provided with an injection end, a fluid receiving end opposite the injection end, and a fluid pathway extending between the receiving end and the injection end. The system also includes a member positioned at the fluid receiving end of the needle. The member, in one embodiment, includes a passage in communication with the pathway of the needle and through which fluid is introduced into the pathway of the needle. The passage, in an embodiment, includes a diameter relatively smaller than that of the pathway, so that fluid directed therethrough and exiting the injection end of the needle can be dispensed at a substantially uniform rate. In one embodiment, the passage includes a diameter that is up to about 80% of the diameter of the pathway of the needle.

The present invention, in accordance with another embodiment, provides a method for controlling the rate of hypodermic injection. The method includes providing a needle having an injection end, a fluid receiving end opposite the injection end, and a fluid pathway extending between the receiving end and the injection end. Next, a restriction passage may be provided at the receiving end of the needle through which fluid is introduced into the pathway of the needle. Thereafter, fluid may be directed across the passage into the pathway, such that fluid exiting the injection end of the needle is being dispensed at a substantially uniform rate.

Brief Description of Drawings Figs. 1A-B illustrate a system for controlling the rate of dispensing fluid from a hypodermic needle in accordance with one embodiment of the present invention.

Figs. 2A-B illustrate, in accordance with another embodiment of the present invention, a system for controlling the rate of dispensing fluid from a hypodermic needle.

Fig. 3 illustrates, in accordance with a further embodiment of the present invention, a system for controlling the rate of dispensing fluid from a hypodermic needle.

Detailed Description of Specific Embodiments In connection with dispensing fluid, such as a dosage of a therapeutic compound, from a syringe through a hypodermic needle, there are several forces which need to be considered.

F≤: Spring force that needs to be applied to the plunger to assure a complete injection.

F_BO: Break-loose force between the plunger resting in the barrel, the material from which the syringe barrel is made (e.g., glass or plastic), and the lubrication (e.g., silicone). This force is usually higher than the following sustaining force (F_F). In the case of prefilled syringes, F_BO is increasing with longer storage times.

FF: Sustaining or friction force between the rubber piston at the tip of the plunger, the syringe barrel, and the lubrication (silicone). This force is usually increasing with the advancement of the plunger/piston, as the distribution of silicone decreases towards the tip of the syringe barrel.

F_DFR: Fluid resistance of the liquid injected drug. This dynamic force increases with injection speed, applied plunger force, needle length and reduction in needle diameter.

F_Hτ: Resistance in the skin /muscle. The resistance of the human tissue to receive the liquid and give way to it as it forms a pool. This force is usually negligible compared to forces F_Bo_> Fs, and F_DFR.

In order to assure a complete injection, the applied or spring force (Fs) has to overcome the other forces mentioned above. Generally, as the plunger is advanced and the sustaining or friction force (F_F) increases, the spring force (F_s) decreases with further relaxation of the spring. Those are conflicting parameters. In order to compensate for this, the spring may have to be overdimensioned. In other words, the spring force Fs may be made stronger than the resisting forces FF + FHT early in the injection in order to assure that towards the end, the spring force Fs, now weaker, can still overcome an increase in the resistance forces FF + FHT- The need to provide a sufficiently strong initial spring force Fs to compensate for the decreasing spring force as the spring relaxes can lead to very high injection speeds, which can be painful to the patient.

As for the dynamic fluid resistance force (F_DFR), while it increases with an increase in needle length and a reduction in needle diameter, it also acts as a regulator or dampener. In particular, the smaller the needle diameter and the longer the needle, the higher the resistance force F_DFR- AS it is a dynamic force, it is "0" at injection speed "0", and hence acts as the variable in the system. The plunger, once moving, is in an equilibrium. On one side, the plunger receives the spring force (Fs), which is constantly declining. On the other side, the plunger encounters friction force (F_F), which is variably increasing (lubrication quality dependent), plus the variable dynamic flow resistance (FDFR). These forces can thus be expressed as follows:

Fs = F_F + F_DFR (F_HT neglected)

In order to provide an injection which is substantially uniform in its dispensing rate, it is desirable to have Fs just a little bit greater than Fp at any given point during the injection. F_DFR, therefore, would make up the difference, and would be small. As a result, the injection speed would also be very small.

The present invention provides, in one embodiment, an increase to the dynamic fluid resistance force F_DF_R through a physical restriction of the fluid path, in order to provide a substantially uniform rate of injection.

During injections given by a caregiver operating a syringe in the traditional way without the aid of an auto-injector, a restricted fluid path can minimize the variability in applying more or less force that traditionally would result in different injection speeds. To that end, for any therapeutic outcome, or to simply reduce injection pain, a modification to the fluid pathway can make it possible to apply a slower injection, and thus a substantially uniform injection rate, regardless of needle diameter and the applied plunger force. Fluid flow restriction can be achieved in a variety of different ways depending on the physical embodiment of the syringe: Prefilled or non-prefilled syringe with a Luer tip and common Luer needle:

As illustrated in Figs. 1 A-B, there is provided a hypodermic needle 11 coupled to a needle hub 12. The needle hub 12, in one embodiment, allows the needle 11 to engage a syringe (not shown) designed with a Luer tip. To provide a restriction in the flow of fluid into pathway 13 of needle 11, the needle hub 12 may be designed to include a passage 14 at a junction where the pathway 13 meets the passage 14. As shown in Fig. IB, passage 14 includes a diameter "d" that is measurably smaller than diameter "D" of pathway 13. In one embodiment, the diameter d may be up to about 80% the size of the diameter D. In this manner, fluid flowing into the pathway 13 can be restricted as it moves across the passage 14. To further enhance the restriction of fluid flow into the pathway 13, the needle hub 12 may be designed with a narrowing diameter at its tip near the juncture between the pathway 13 and the passage 14. Alternatively, the tip of the syringe (not shown) may be narrowed.

Prefilled syringe with attached (staked^*) needle:

Figs. 2 A-B illustrate an embodiment wherein hypodermic needle 21 is attached to a syringe 22. In the embodiment shown in Figs. 2A-B, a restriction member 23 may be provided at an end 24 opposite an injection end 25 of the needle 21. The restriction member 23, in one embodiment, may be substantially cylindrical in shape and includes a flared end 231 and an exit end 232. As shown in Fig. 2B, the exit end 232 may be placed within pathway 26 of the needle 21. The flared end 231 can be positioned against the end 24 of the needle 21 and act to prevent the restriction member 23 from being pushed into the pathway 26. The restriction member 23 may further include a passage 233 extending from the flared end 231 to the exit end 232 through which fluid may flow into the pathway 26 of the needle 21. The passage 233 can be provided with a diameter measurably smaller than that of the pathway 26. In one embodiment, the diameter of the passage 233 can be up to about 80% of the diameter of the pathway 26.

The restriction member 23 provides a flow restriction to fluid being directed into the pathway 26, such that fluid exiting from the injection end 25 of the needle 21 can be dispensed at a substantially uniform rate.

The restriction member 23 may be placed within the pathway 26 of the needle 21 during the assembly process of the needle 21 to the syringe 22. Other designfs)

Fig. 3 illustrates another embodiment of the present invention. As illustrated, needle 31 may be provided with a restriction member 32 circumferentially positioned about an end 33 opposite an injection end 34 of the needle 31. The restriction member 32, in one embodiment, may be cylindrical in shape to approximate the shape of the needle 31. The restriction member 32 may be provided with a passage 321 in communication with pathway 35 of needle 31. Passage 321, in an embodiment, includes a diameter "d" that is measurably smaller than diameter "D" of the pathway 35. In one embodiment, the diameter d can be up to about 80% of the diameter D. In this manner, fluid flow across the passage 321 into the pathway 35 can be restricted, so that the rate of fluid flow from the injection end 34 of the needle 31 can be substantially uniform.

The restriction member 32, in an embodiment, may be designed to engage the tip of a syringe (not shown), or a needle hub (not shown) which can subsequently be coupled to the tip of a syringe. By providing a restricted passage through which fluid, such as a dosage of therapeutic compound(s) (e.g., β-interferon), may be directed into the pathway of the hypodermic needle, the system of the present invention can, for instance, minimize leakage of fluid into tissue through which the needle must travel before arriving at the required depth. For instance, in an intramuscular injection, the hypodermic needle must travel through the subcutaneous space before reaching the intramuscular tissue. The presence of a restricted passage, such as that provided in the present invention, can initially restrict fluid flow into the pathway of the needle during insertion of the needle, and therefore, can minimize incidents of leakage of the therapeutic compound into the subcutaneous space. To that end, the therapeutic compound may only be dispensed when the needle has reached the intramuscular tissue. In addition, as certain therapeutic compounds can undesirably precipitate from solution, especially when being dispensed through a conventional hypodermic needle, it is believed that the presence of a restricted passage can minimize incidents of precipitation. In particular, as the restricted passage can generate a substantially uniform rate of fluid dispensing, rather than a variable rate of fluid dispensing (which can generate fluid turbulence leading to precipitation) typically observed in connection with a conventional hypodennic needle, the uniformity of the dispensing rate, is believed, to minimize incidents of precipitation.

While the invention has been described in connection with the specific embodiments thereof, it will be understood that it is capable of further modification. Furthermore, this application is intended to cover any variations, uses, or adaptations of the invention, including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as fall within the scope of the appended claims.

Claims

What is claimed is:

1. A system to control the flow of fluid through a needle, the system comprising: an elongated needle having an injection end, a fluid receiving end opposite the injection end, and a fluid pathway extending between the receiving end and the injection end; and a member positioned at the fluid receiving end of the needle and having a passage in communication with the pathway of the needle and through which fluid is introduced into the pathway of the needle; the passage having a diameter relatively smaller than that of the pathway, so that fluid directed therethrough and exiting from the injection end of the needle can be dispensed at a substantially uniform rate.

2. A system as set forth in claim 1 , wherein the diameter of the passage is up to about 80% of the diameter of the pathway of the needle.

3. A system as set forth in claim 1, wherein the member includes a needle hub for engaging a tip of a syringe.

4. A system as set forth in claim 1, wherein the needle hub includes a narrowing tip proximate to a juncture between the passage and the pathway of the needle.

5. A system as set forth in claim 1, wherein the member is positioned within the pathway at the receiving end of the needle.

6. A system as set forth in claim 5, wherein the member includes a flared end adjacent the receiving end of the needle and an exit end positioned within the pathway of the needle.

7. A system as set forth in claim 5, wherein the passage extends from the flared end to the exit end of the member.

8. - A system as set forth in claim 1, wherein the member, substantially cylindrical in shape, is positioned circumferentially about the receiving end of the needle.

9. A system as set forth in claim 8, wherein the member is designed to engage one of a syringe tip and a needle hub.

10. A method for controlling the rate of hypodermic injection, the method comprising: providing a needle having an injection end, a fluid receiving end opposite the injection end, and a fluid pathway extending between the receiving end and the injection end; generating a restricted passage at the receiving end of the needle through which fluid is introduced into the pathway of the needle; directing fluid across the restricted passage into the pathway, such that fluid exiting the injection end of the needle is being dispensed at a substantially uniform rate.

11. A method as set forth in claim 10, wherein directing includes minimizing leakage of fluid from the injection end of the needle prior to the needle reaching a desired depth