IMPLANT INJECTION DEVICE

Abstract: The invention relates to an injection device (1), in particular for once-only use, for injecting an implant (6) which can release a drug in a controlled manner, which device comprises a housing (2) which is provided at the injection end with an injection needle (3) in which the implant (6) can be disposed and in which a passage opening is disposed at the actuating end of the housing for a plunger (7,8), mounted in the housing and displaceable in the axial direction of the needle (3), which, on the one hand, can interact with the implant (6) and, on the other hand, is provided with an actuating element, which element is constructed as an element (10) for pressing and supporting against or on the part of the body to be treated.

Description: The invention relates to an injection device, in particular for once-only use, for injecting an implant which can release a drug in a controlled manner, which device comprises a housing which is provided at the injection end with an injection needle in which the implant can be disposed and in which a passage opening is disposed at the actuating end of the housing for a plunger, mounted in the housing and displaceable in the axial direction of the needle, which, on the one hand, can interact with the implant and, on the other hand, is provided with an actuating element. Such devices (see GB-A-2138298) are known and are being used to an increasing extent for disposing, beneath the skin of the human body, a holder containing drugs which are gradually released over a relatively long time, for example a few weeks to a few years, to the body. In view of the usually great importance of such injections, they have to be carried out extremely accurately and carefully so that the implant is disposed in the correct position and manner beneath the skin and the satisfactory action of the drugs concerned is guaranteed. It is not satisfactorily possible to meet the requirements set using the known injection devices, inter alia, that which is described in WO 84/00304. The object of the invention is to provide an injection device of the type mentioned in the introduction in which very high requirements as regards accurate injection and satisfactory action of the drugs are met over the required time. According to the invention, the injection device is characterized by the fact that the actuating element is constructed as an element for pressing and supporting against or on the part of the body to be treated, the supporting element being formed by a supporting surface, preferably provided with transverse ribs, whose surface area is 1 to 10 cm², in particular 2-5 cm². According to the invention, an embodiment of the injection device to be chosen is characterized by the fact that the supporting surface is elongated and extends in the longitudinal direction and at some radial distance from the plunger, and in that the pressing element is formed by a pressing surface, preferably provided with transverse ribs, which is disposed on the plunger opposite the supporting surface. Advantageously, according to the invention, the supporting surface is situated at an acute angle (α) of the size of, for example, approximately 5° to the longitudinal direction of the plunger. The use of the device according to the invention is improved if the outside surface of the housing has over at least a section of the length one ore more essentially flat surfaces. Said flat surfaces may be disposed in a manner such that the housing has an approximately polygonal section, for example hexagonal, transversely to its longitudinal direction. According to the invention, a beneficial embodiment of the injection device is characterized by the fact that the housing and the plunger are provided with stop elements which interact with each other and which are constructed in a manner such that the distance over which the plunger can be displaced in the hollow needle towards the extremity thereof is limited. According to the invention, the housing and the plunger are advantageously linked to each other via a coupling which, in the closed coupled state, links the housing and the plunger immovably to each other and, in the opened decoupled state, permits movement of the plunger in the housing and in the hollow needle. According to the invention, one half of the coupling is in this case formed at the end of the said supporting surface of the plunger facing the needle. The injection device according to the invention is advantageously characterized by the fact that the housing moulded from a thermoplastic material, in particular polyacetal, polyethylene, polypropylene or the like, is provided with a cylindrical axial bore adjoining the hollow metal needle, that the plunger, also moulded from a thermoplastic material, is disposed so as to be axially displaceable in the bore of the housing and in the hollow needle and that the actuating element of the plunger is provided with pressing and supporting surfaces situated opposite each other in a diametrically oblique manner with respect to the plunger axis, the plunger having, at the actuating end, a first section with a large diameter which fits into the bore of the housing and the plunger having, at the injections end, a second section with a smaller diameter which fits into the hollow needle. The invention also comprises the injection device described which is provided with, in particular, an elongated, implant which can release a drug in a controlled manner. According to the invention, the implant is preferably formed by a polymer such as polysiloxane, polyalkylene or polylactide, in which the drug is homogeneously dispersed or which encases the drug. The invention also comprises the sterilized device which is disposed in a closed packaging, inaccessible to bacteria, formed preferably from a transparant thermoplastic material or from aluminium foil. If the needle in said packaging contains the implant and is provided with a protective cap, the injection device can be carefully manufactured commercially in its entirety in said packaged form even in large numbers. In this case, in carrying out the injection, it is necessary only to remove the packaging, provided, for example, with a tear strip, and the protective cap from the needle. In other words, at the treatment site, the operations to be carried out by the doctor or nurse involved are limited to a minimum. Risks of infection are excluded by the once-only use of the device according to the invention. Infections and transferable diseases are avoided by the once-only use especially in the treatment of fairly large groups of people. As a result of the practical and simple construction of the injection device according to the invention with the pressing and supporting elements described, the injection device can easily be pressed and supported with one hand on the body to be treated, while the other hand is free and, after injecting the needle with the implant therein, can be used for possibly opening the said coupling between plunger and housing and for withdrawing the needle from the body. In this process, the implant is simultaneously pushed by the free extremity of the plunger out of the hollow needle, as a result of which the implant remains behind in the body. The construction of the injection device according to the invention with the said stop elements on the housing and plunger has the advantage that, during injection of the needle with the implant, undesirable premature movement of the implant in the hollow needle can be prevented. In particular, as a result of this, it is possible to prevent, with the injection device according to the invention, the implant being pushed during the insertion of the needle in the body by the plunger wholly or partially outwards from the needle with all the disadvantages thereof such as, for example, the breaking off of the implant or the excessively deep insertion of the implant. All this has the consequence that, with the simple injection device according to the invention, the injection of an implant, which is important to an increasing extent, can be carried out particularly accurately and carefully. The satisfactory action and the accuracy of the injection device according to the invention are improved still further if the housing and the plunger are linked to each other in the manner described via a coupling. The invention also comprises a method for inserting an implant in a body, which implant can release a drug in a controlled manner, the injection device described and according to the invention being used. The invention will be explained in more detail by reference to the diagrammatic drawing. Figure 1 shows the injection device according to the invention with lock or coupling. Figures 2-5 show the device according to Figure 1 in various states during use. Figures 6-8 show, on a larger scale, the construction of the lock or the coupling in the device according to Figures 1-5. Figure 9 shows an actual construction of the injection device according to the invention in elevation. Figure 10 shows the device according to Figure 9 in the state during the withdrawal of the needle. Figure 11 shows the device according to Figure 9 in the state following the complete withdrawal of the needle and following the injection of the implant. Figures 12 and 13 show two somewhat modified embodiments, no lock or coupling being disposed between the plunger and the housing. Figure 14 shows a construction with the supporting surface in another position. Figure 15 and 16 show an embodiment in which the housing has a hexagonal section. Figure 1 shows, in longitudinal section, a first embodiment of the injection device according to the invention, indicated in general by 1, which contains a housing 2 and an injection needle 3 attached thereto, from which the protective cap 4 shown in Figure 9 has been removed. The packaging for the injection device 1 has also already been removed in the situation according to Figure 1. Just in front of the start of the sloping point 5 of the needle 3 there is located therein the cylindrical implant 6 which contains a drug to be released in a controlled manner. Furthermore, the housing 2 contains an axially displaceable and rotatable plunger therein, which, at the injection end of the device has a cylindrical section 7 with smaller diameter and, at the actuating end of the device, has a cylindrical section 8 with larger diameter. The plunger section 7 with smaller diameter rests against and can interact with the implant 6, for which purpose plunger section 7 fits into the hollow needle 3 with a fit which permits axial movement. The plunger section 8 with larger diameter is mounted in the housing 2 with a fit which permits axial movement. At the end facing away from the needle 3, the plunger is provided with an actuating element which, in the embodiment according to Figure 1, is constructed with a supporting element in the form of the supporting surface 9 and a pressing element in the form of the pressing surface 10. The supporting surface 9 and the pressing surface 10 both form flat surfaces which are provided with ribs 11 and which are attached obliquely and diametrically opposite each other to the plunger section 8. On the housing 2 an upright projection 12 has been formed which interacts with the end of the supporting surface 9 to form an axial stop to limit the maximum distance over which the plunger and the housing can be displaced towards each other. In the state according to Figures 1 and 2, the housing 2 and the plunger 7, 8 are linked to each other via a coupling or lock between parts of the projection 12 and the pressure surface 9 which interacts with each other in the zone 13 encircled by a broken line. The circled zone 13 of the injection device is drawn for clarification on a larger scale in Figures 6, 7 and 8. In order to bring about the coupling between the housing 2 and the plunger 7, 8, the projection is provided with a groove 14, to some extent following a circle, having a cross section with a swallow-tail shape. As can be seen from the front view in Figure 6 and the plan view in Figure 7, the supporting surface 9 rigidly linked to the plunger is provided with a projection 15 having a cross section which is also of swallow-tail shape and which engages in the groove 14 at least in the situation with closed coupling or lock shown in Figures 1, 2, 6 and 7. It will be clear that in the last mentioned closed state of the coupling or the lock, the housing and the plunger are linked to each other immovably in the axial direction. This linking between housing and plunger can be broken by opening the coupling, which can be done by rotating the plunger around its axis in the direction of the arrow 16 indicated in the side view of Figure 6, in which process the projection 15 is released from the groove 14. Figures 2-5 indicate diagrammatically the course of events during the insertion of the implant 6 beneath the skin of the body 18 of a patient. In this process, the point of the needle 3 of the device 1 is placed at the desired point of the skin 17 (Figure 2) and then the complete device 1 is displaced axially in the direction of the arrow 19, the needle 3 with the implant 6 therein being inserted over the length of the needle into the body 18 beneath the skin 17. The last mentioned situation is shown in Figure 3. After the needle 3 with the implant 6 therein has reached the subcutaneous position according to Figure 3, the coupling between the housing 2 and the plunger 7, 8 is opened by rotating the plunger through 180° about its axis, in which process the projection 15 is released from the groove 14 and the supporting surface 9 and the pressing surface 10 reach the position shown in Figure 3 with respect to the skin. Then the pressing surface 10 is pressed downwards with one hand 20, as a result of which the large supporting surface 9 forming a whole with the plunger is firmly pressed on the skin 17. Then the housing 2 is slid axially over the plunger in the direction of the arrow 21 using the other hand. During the last metioned sliding movement, the housing 2 and the needle 3 firmly attached to it are withdrawn from the body 18. Immediately the needle 3 has left the body 18, the projection 12, which also acts as a stop, comes up against the linking piece 22 of the supporting surface 9 and the pressing surface 10 (see Figure 4). During the last mentioned withdrawal of the needle 3, the section 7 of the plunger gradually drives the implant 6 out of the needle, as a result of which the implant is just completely free of the needle in the body and the needle has just left the body. The device 1 can then be removed in the direction of the arrow 23 (see Figure 5) and be destroyed since it is intended only for once-only use. In order to give a still clearer picture of the practical construction and the design, the injection device according to the invention of the type according to Figures 1-8 is again shown in elevation in various situations in Figures 9, 10 and 11. Figure 9 in this case shows the injection device in the same position as is shown in section in Figure 1, but with the needle provided with a protective cap 4. Figure 10 shows the injection device in an intermediate state in which approximately half of the needle may be withdrawn from the body. Figure 11 shows the injection device in the state in which the needle may have been withdrawn completely from the skin, which state corresponds to Figure 4. Figures 12 and 13 show somewhat modified embodiments of the injection device 1 according to the invention, in which corresponding parts have been indicated with the same reference numerals. The most important difference of the two devices shown in Figures 12 and 13 from that according to Figures 1-11 is that the device according to Figures 12 and 13 lacks the said coupling or the lock between the housing 2 and the plunger 7, 8. In the device according to Figure 12, supporting surface 9 has a smaller surface area than in the device according to Figures 1-11, which may be of practical importance in situations in which little space is present for the supporting surface. In the device according to Figure 13, the pressing surface 10 and the supporting surface have an equally large square surface area. Figure 14 shows a somewhat different embodiment in which the supporting surface 9 is situated obliquely, i.e. at an acute angle α of, for example, approximately 5° with respect to the longitudinal axis of the plunger 7, 8. The angle β between the supporting surface 9 and the linking piece 22 is also then acute and is then approximately 85°. Figure 15 with the associated outline of the cross section at the point XVI-XVI shown in Figure 16 show an embodiment in which the periphery of the housing 2 has a hexagonal cross section over the section 24 of the length. The outline of the housing 2 has, as a result of this, six flat surfaces over the length 24, as a result of which the use of the device according to the invention is improved. Of course, instead of a hexagonal section, a more or less truncated or another polygonal cross section such as a retangle can also be used. Various modifications can be made within the scope of the invention. In particular, couplings or locks of another type may be disposed between the housing and the plunger.

Claims: 1. An injection device (1), in particular for once-only use, for injecting an implant beneath the skin which implant can release a drug in a controlled manner, which device comprises a housing (2) provided at the injection end with an injection needle (3) in which an implant can be disposed and in which a passage opening is disposed at the actuating end of the housing for a plunger (7, 8), mounted in the housing and displaceable in the axial direction of the injection needle, which plunger on the one hand, can interact with the implant and, on the other hand, is provided with an actuating element, characterized in that the actuating element comprises a pressing element (10) and a supporting element (9) situated opposite each other in a diametrically oblique manner with respect to the plunger axis, for pressing and supporting against or on the part of the body to be treated. 2. The device of claim 1, characterized in that the supporting element is formed by a supporting surface (9), preferably provided with transverse ribs (11), whose surface area is 1 to 10 cm², in particular 2-5 cm². 3. The device of claim 2, characterized in that the surface of the supporting element is elongated and extends in a longitudinal direction and at some radial distance from the plunger (18). 4. The device of claim 3, characterized in that the surface of the supporting element is situated at an acute angle (α) with respect to the longitudinal direction of the plunger. 5. The device of claim 2, characterized in that the pressing element (10) comprises a pressing surface, preferably provided with transverse ribs, disposed on the plunger opposite the supporting surface (9). 6. The device of claim 1, characterized in that the outside surface of the housing has (2) at least one essentially flat surface. 7. The device of claim 6, characterized in that the device has more than one flat surface which flat surfaces are disposed in a manner such that the housing has a polygonal cross-section (transversly to its longitudinal direction). 8. The device of one or more of preceding claims, characterized in that the housing (2) is associated with a stop element (12) which interacts with the plunger and which is constructed in such a manner that the distance over which the plunger can be displaced in the injection needle is limited. 9. The device of claim 1, characterized in that the housing (2) and the plunger (7, 8) are linked to each other via a coupling (14, 15) which, in a closed state, links the housing and the plunger immovably to one another and, in an open state, permits movement of the plunger in the housing and in the injection needle. 10. The device according to claims 3 and 9, characterized in that one half of the coupling is formed at the end of the supporting surface of the plunger facing the injection needle. 11. The device of one or more of the preceding claims, characterized in that the housing, moulded from a thermoplastic material, in particular polyacetal, is provided with a cylindrical axial bore adjoining the injection needle and in that the plunger, also moulded from a thermoplastic material, is disposed so as to be axially displaceable in the bore of the housing and in the injection needle. 12. The device of claim 11, further characterized in that the plunger has, at the actuating end, a first section with a large diameter which fits into the bore of the housing and, at the injection end, a second section with a smaller diameter which fits into the injection needle. 13. The device of one or more of the preceding claims, characterized in that the device further comprises an implant (6) which can release a drug (in a controlled manner). 14. The device of claim 13, characterized in that the implant comprises a polymer such as polysiloxane, polyalkylene or polylactide, in which the drug is dispersed or which encases the drug. 15. The device of one or more of the preceding claims, characterized in that the sterilized device is disposed in a closed packaging, inaccessible to bacteria, formed preferably from a transparent thermoplastic material or from aluminium foil.

Inventors: FREDERICK, MERVYN JOSEPH, KOENEN, WILHELM ENGELINUS
Applicants: AKZO N.V.
Application year: 1988
Main classification: A61M37
IPC codes: A61M5, A61M31, A61M37