LOW FRICTION COATING FOR CARTRIDGE SEAL CAP

Abstract: Disclosed is an improvement in a coupling system for transferring liquid medicament from a cartridge (10) to a needle unit (60), wherein the improvement comprises a low friction coating deposited on the metallic seal cap (30) (36).

Description: LOW FRICTION COATING FOR CARTRIDGE SEAL CAP BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a low friction coating for a coupling system for transferring liquid medicaments from one flow conduit to another and, more particularly, to a low friction coating for a cartridge seal cap used in conjunction with disposable liquid medicament-containing cartridge-needle units. Reported Developments Disposable medicament-containing cartridge needle units are well known in the art and in widespread commercial use. Such cartridges conventionally feature a cartridge barrel, formed of glass or plastic having a distal end and a proximal end. The proximal end of the cartridge is closed with a slideable plunger, while the distal end has a neck portion which terminates in an opening closed by a diaphragm or septum secured to the cartridge by a crimped-on metal collar, usually aluminum collar. The neck portion of the distal end is adapted to receive and engage a needle-hub-needle-needle guard assembly. The needle-hub portion snaps onto the diaphragm in a mating relationship. When tne needle hub is snapped on the cartridge, the proximal end of the needle cannula pierces the diaphragm thereby providing communica ion between said needle cannula and the liquid medicament contained in the cartridge barrel . Such a needle-hub- needle-needle guard assembly is shown, for example, in U.S. Patent No. 5,358,491. One of the major concerns relating to the delivery of liquid pharmaceutical products via injection to patients is the generation and presence of particulate foreign matter which may contaminate such products. In order to eliminate macroscopic and microscopic particulates , elaborate measures have been taken to remove them, such as filtration of the product and special washing and drying of the closure-system components. These steps help assure that the products meet the requirements and guidelines of the pharmaceutical industry, such as compendia guidelines, when the products reach the point of use. However, at the point of use new particulate matter is frequently generated by the practitioner when the septum is penetrated by the needle of the injection assembly. During such penetration a combination of elastic and plastic deformation of the target area increases the septum contact surface with the needle as the needle is pressed into the septum. Typically, untreated elastomer septums offer a high resistance against the exterior surface of the needle as the needle is being inserted into the penetration area. Most frequently, when septum fragments are generated, they are the result of the elastomeric portion of the septum being abraded off the upper surface of the septum as it conforms to the shape of the needle. The fragments then either enter into the needle cannula or the interior of the cartridge as the needle drags the fragments during penetration. The most common solution to the problem of particulate matter generation has been the application of silicone lubricant to the septum to reduce the frictional drag between the septum and the needle. While silicone does reduce generation of particulate matter, it also increases the risk of product contamination from its own composition. Another approach proposed in the prior art to reduce the tendency of the stopper to generate particulate matter is to coat the elastomeric core of the septum with a thermoplastic film on the fluid contacting side thereof. Still another approach was proposed in U.S. Patent No. 5,219,083 to eliminate or greatly reduce particle generation from the septum during needle penetration, by applying an inert, abrasion -resistant coating to the proximal surface of the stopper, i.e. , to the surface of the septum which has no contact with the liquid pharmaceutical contained in the cartridge. While these approaches greatly reduce the generation and presence of particulate matter originating from the septum during the penetration process, we have observed the presence of particulates originating from the cnmped-on metal collar holding the septum in place in the cartridge. Such particulates are generated during the process of making the collar and the crimping process. Similarly to the result of generation of particulate matter originating from the septum, the particulate matter originating from the metal collar may get into the needle cannula causing clogging or delivery of a liquid pharmaceutical contaminated with metallic particles into the patient. One of the objects of the present invention is to eliminate or at least greatly reduce the tendency of this occurrence. Another object of the present invention relates to the reduction of activating force needed to activate the needle-hub- needle-needle guard assembly when the cartridge content is to be injected into the patient. Conventionally, the cartridge, containing the liquid medicament is packaged separately from the needle-hub-needle guard assembly Prior to injection the assembly is snapped on the cartridge, the proximal end of the needle cannula penetrating the septum, and the needle guard removed to render the device ready for injection. During the process, it is desirable that the snap-on step is easy, not requiring excessive force, as well as when the injection is completed and the needle- hub-needle-needle guard assembly is removed from the cartridge, the force of removal is not excessive to the average practitioner We have found that both the snap-on and the removal steps tended to be cumbersome for some practitioners As a result of intensive studies directed to solving this problem, as well as solving the problem of the presence of particulate matter originating from the metal cap holding the septum in place, we have found that a coating during the manufacture of the metal cap or after the cap is crimped on the septum and the cartridge, greatly reduces the tendency, or completely eliminates the necessity of applying excessive force by the practitioner to activate and/or deactivate the cartridge containing the liquid medicament. SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a low friction coating for a coupling system for transferring liquid medicaments from one flow conduit to another, and more particularly, to a low friction coating for a cartridge seal cap used in conjunction with disposable, liquid medicament-containing cartridge-needle units to eliminate or at least greatly reduce, the presence of particulate materials originating from the coupling system and to reduce the force of activation and deactivation of the device. In particular, the invention provides an improvement m a cartridge-needle assembly wherein said cartridge comprises: (a) a cartridge barrel having a distal end and a proximal end, a plunger axially and reciprocally εlideable in the cartridge barrel; a septum of a resilient material sealing the distal end of the cartridge barrel; and a cartridge seal cap having an aperturee located at its center for allowing a needle to penetrate the septum, said cartridge seal cap securely holding said septum in place; ( b ) a needle assembly unit comprising a hub axially holding a needle, said needle having a distal end and a proximal end, said hub comprising a sleeve constructed to be snapped on the distal end of said cartridge while said proximal end of said needle penetrates the septum in the cartridge; and (c) a sheath covering the distal end of the needle constructed to be snapped on the hub for protection against injury by the needle to the user; wherein said improvement comprises: a coating of low friction material covering the cartridge seal cap to prevent particulate material originating from the cartridge seal to enter into the needle and to reduce tne fπctional force needed to activate and deactivate the cartridge . The coating of the metallic cartridge seal cap may be done during the manufacturing of the cap or after the cap is crimped on the cartridge. Such coating may be: a polyolefin, such as polypropylene and polymethylpentene; a polyvinyl, such as polystyrene, polyvinyl acetate (PVA) , polyvinyl chloride (PVC) , polyvinylidene chloride (PVDC) , a copolymer of polyvinylchloride (PVC) and polyvinylidene chloride (PVDC) , polyvinyl fluoride, and polyvinylidene fluoride; an ether, such as polymethylene oxide, polyphenylene oxide and polyphenylene sulphone; an ester, such as polyethylene terephthalate (PET) , polycarbonate and copolyester,- an ester, such as polycaprolactam (Nylon 6) , polyhexamethylene adipamide (Nylon 66) and polyundecanoamide (Nylon 11) . We have found polytetrafluoroethylene (TEFLON) to provide one of the best low friction coating materials. The coating thickness will be in the range of about 0.002 to about 1.0 mm, and preferably about 0.02 to 0.5 mm. The coating may be applied or bonded to the metallic cap material in any suitable manner known in the art, such as, but not limited to, by the use of adhesives, solvents, spray applications, radio waves, infrared, microwaves, ultrasonics and heat. If the coating of the seal cap is done after the crimping operation, the coating may also cover the central portion of the septum which is exposed by the aperture in the seal cap. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate an embodiment of the present invention in which: FIG. 1 is a plan view of a needle assembly unit showing a hub axially holding the needle; FIG. 2 is a plan view of a cartridge; FIG. 3 is a plan view of a sheath to cover the needle shown in FIG. 1; FIG. 4 is plan view of a plunger for use in the cartridge shown in FIG. 2; FIG. 5 is a plan view of a fully assembled cartridge, plunger and hub-needle assembly without the sheath; FIG. 6 is an enlarged, fragmentary, longitudinal cross section of the distal end of the cartridge having the septum in place, the crimped-on seal cap and a portion of the hub and needle prior to the needle piercing the septum; and FIG. 7 is an enlarged, fragmentary, longitudinal cross section of the distal end of the cartridge having the septum m place, the crimped-on seal cap and a portion of the hub and needle after the needle has pierced the septum. DETAILED DESCRIPTION OF THE INVENTION This invention is useful in conjunction with a wide variety of cartridges activatable by a snap-on needle unit. The invention will now be described with reference to the drawings which illustrate a preferred embodiment of the invention. Shown in FIG. 2, cartridge 10 comprises: a cartridge barrel 20, formed of glass and plastic, having a distal end 26 and a proximal end 40. Distal end 26 has a neck portion 28 which terminates in an opening (not shown) , closed by a seal or diaphragm cap 30 and a septum or diaphragm 36. Seal cap 30 contains an annular groove 32 to receive a snap-on hypodermic needle assembly 60 shown in FIG. 1. Hypodermic needle assembly 60 comprises a snap-on portion 62 which is to engage seal cap 30 in a mating relationship, and a conical portion 64 which is to receive and engage proximal end 74 of sheath 70. When the hypodermic needle assembly 60 is snapped on the cartridge, the proximal end of needle 66 pierces the septum 36, thereby providing communication between said needle and liquid medicament 24 contained m cartridge barrel 20. The proximal end 40 of cartridge 10 is open for receipt of a plunger or piston 50, shown m FIG. 4, which has a forward, liquid-interfacing surface 52 and a rearwardly extending threaded portion 56 for interconnec ion with a plunger rod mot shown) when the cartridge is readied for use. FIG. 6 shows an enlarged, fragmentary, longitudinal cross section of the distal end of cartridge barrel 20, having septum 36 covering the distal opening of the barrel, the crimped-on seal cap 30 and snap-on portion 62 of the hypodermic needle assembly. As shown, at this stage of the process, the proximal end of needle 66 has not pierced septum 36. FIG. " shows the same parts and spacial configuration thereof, except the proximal end of needle 66 has now pierced septum 36. As shown, crimped-on seal cap 30 includes aperture 38 in its center portion to expose underlying septum 36 to allow piercing of same by the proximal end of needle 66. Crimped-on seal cap 30 is coated with a low friction polymeric coating 80. The coating may cover the exterior surface of the seal cap or it may cover it both on its exterior and interior surfaces. When the coating is applied after the seal cap is crimped on the cartridge, the coating may also cover the center, exposed surface of the septum. Referring now to materials of construction, such materials are available from commercial sources. The septum can be made of compliant, rubbery materials capable of resealmg itself after being pierced. Preferred materials possess a Shore A durometer hardness of from about 50 to about 70. The seal cap, which holds the septum in place after it is crimped on, is made of any suitable metallic materials, preferably aluminum. The needle unit, except the needle which is of stainless steel, is fabricated of plastic. Suitable plastics include polypropylene, polystyrene, nylons, acetals, polyethylene and polyester. Referring now to the use of the device, the health professional receives the device in a form wherein the cartridge is pre-filled with the liquid medicament and is sealed at both ends: the distal end is sealed by the septum and seal cap, while the proximal end is sealed by the plunger. The plunger rod is not attached to the plunger and neither is the needle unit snapped-on the distal end of the cartridge. In readying the device for use, the cartridge-needle unit is activated by causing the proximal end of the needle to pierce the septum and the cartridge is moved forward in the hub to reach the snapped position. The snap-on step is convenient and easy since the smooth coated surface of the seal cap exerts little frictional force on the hub of the needle unit. The plunger rod is screwed onto the post of the plunger. Lastly, the sheath covering the exposed portion of the needle is removed. Thereafter, the distal end of the needle is inserted into the injection site and the liquid medication is delivered to the patient by applying an axially directed force to the plunger rod. Cartridge activation force was determined using TEFLON-coated and non-coated seal caps crimped onto cartridges. Instron 4502 equipment was used to determine the maximum load expressed in pounds to activate the needle into the cartridges of 40-samples of each of the coated and uncoated samples. The average forces and standard deviations were as follows: Samples Average Standard Deviation TEFLON-coated 5.585 0.800 Non-coated 10.561 1.534 The present invention has been described in connection with the preferred embodiment show in the drawings, it is to be noted, however, that various changes and modifications are apparent to those skilled m the art.

Claims: WHAT IS CLAIMED IS: 1. An improved cartridge-needle assembly wherein said assembly comprises : (a) a cartridge, (b) a needle assembly unit and a sheath, wherein said cartridge comprises : a cartridge barrel having a distal end and a proximal end; a plunger, axially and reciprocally slideable in tne cartridge barrel; a septum of a resilient material sealing the distal end of the cartridge barrel; a cartridge seal cap having an aperture located at its center for allowing a needle to penetrate the septum, said cartridge seal cap securely holding said septum in place; wherein said needle assembly unit comprises: a hub axially holding a needle, said needle having a distal end and a proximal end, said hub comprising a sleeve constructed to be snapped on the distal end of said cartridge while said proximal end of said needle penetrates the septum m the cartridge; and a sheath covering the distal end of the needle constructed to be snapped on the hub for protection against injury by tne needle to the user; wherein said improvement comprises: a coating of low friction material covering the cartridge seal cap to prevent contamination oy particulate material originating from the cartridge seal cap and to reduce frictional force needed to activate and deactivate the cartridge-needle assembly. 2. The cartridge-needle assembly of claim 1 wherein said coating is polytetrafluoroethylene . 3. The cartridge-needle assembly of claim 1 wherein said coating covers the cartridge seal cap or. both its exterior and interior surfaces. 4. The cartridge-needle assembly of claim 1 wherein said coating further covers the center portion of the septum exposed by the aperture in said cartridge seal cap. 5. The cartridge-needle assembly of claim 1 wherein said coating of the cartridge seal cap is done prior to crimping the seal cap on the cartridge. 6. The cartridge-needle assembly of claim 1 wherein said coating is done after the cartridge seal cap is crimped on the cartridge. 7. The cartridge-needle assembly of claim 1 wherein said coating is accomplished by the use of spray application, radio waves, infrared, microwaves, ultrasonics or heat.

Inventors: NIEDOSPIAL JOHN J, STIEHL MARK A, NIEDOSPIAL, JOHN, J., STIEHL, MARK, A.
Applicants: SANOFI WINTHROP INC, SANOFI WINTHROP, INC.
Application year: 1996
Main classification: A61M5
IPC codes: A61M5