Patent Document

FIELD OF THE INVENTION 
     This invention relates to a medicine reservoir for use with a drug delivery device, the medicine reservoir being arranged for comprising a drug and comprising a dispensing hole for dispensing the drug into an environment of the drug delivery device. 
     This invention further relates to a drug delivery device comprising such a medicine reservoir. 
     BACKGROUND OF THE INVENTION 
     Such drug delivery devices make it possible to control the release of drugs in the gastrointestinal tract. The drug delivery may take place in accordance with a predetermined delivery schedule and/or may be triggered by external signals or environmental conditions. The device may include additional electronics, sensors and communication devices for controlling the drug delivery. In many swallowable drug delivery devices, the drug release is effected using a displacement based actuator system. For example, a piston may push a predetermined amount of the drug through the dispensing hole. 
     The dispensing hole often is an open orifice. However, an open orifice introduces the possibility for exchange of material between the reservoir and outside environment, resulting, for example, in delivery of the drug before the intended time and a reduction of the amount delivered when intended. The main processes involved are diffusion and convection. Diffusion, because of the open connection between the inside and the outside of the capsule. Convection, because of small differences in specific weight of the substance stored in the capsule and the fluid outside. E.g. when the fluid in the capsule is heavier than the fluid in the intestines and the hole is directed downwards the fluid in the capsule flows out and will be replaced by the fluid of the intestines. Both processes may be slowed down by reduction in the exit hole cross-sectional size, extending the length of the exit hole and increasing the viscosity of the material in the reservoir. However the hole dimensions and the viscosity of the medicine to be administered must be chosen such that it allows the actuator to dispense the medicine. 
     Often, a valve is used for separating the drug reservoir from the outside environment. Valves which operate in small spaces, provide good sealing and use low power are however very difficult to implement. It would thus be advantageous to avoid diffusion or convection of the drug without the use of a valve. 
     OBJECT OF THE INVENTION 
     It is an object of the invention to provide a medicine reservoir for a drug delivery device according to the opening paragraph, which device does not need a valve for keeping the drug inside until the intended moment of release. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, this object is achieved by providing a medicine reservoir for use with a drug delivery device, the medicine reservoir being arranged for comprising a drug and comprising a dispensing hole for dispensing the drug into an environment of the drug delivery device, the medicine reservoir further comprising a deformable plug which plug is removable by a pressure caused by a dispensing action of the drug delivery device. 
     As long as no drug is delivered, the plug seals the dispensing hole and no drug is allowed to leave the medicine reservoir. When the drug delivery device tries to deliver a first amount of the drug, the pressure inside the medicine reservoir increases. The resulting pressure upon the plug then causes the plug to be pushed out of the dispensing hole, thereby enabling the delivery of the drug to the environment. The composition and dimensions of the deformable plug are such that the plug is easily removed by the pressure caused by the first drug delivery. Concurrently, the composition and dimensions of the plug should ensure that the plug will not be removed due to other causes (e.g. temperature changes, gravity, diffusion). A non-deformable plug such as, e.g., a plastic plug would be very suitable for sealing the dispensing hole, but cannot be removed by the dispensing action of the drug delivery device. For easy removal, the plug should be deformable. 
     A suitable plug may, for example, comprise an oil which does not mix with the drug or the gastro-intestinal fluid. For example, a mineral oil or castor oil is very suitable for use as a plug in a medicine reservoir according to the invention, but other non-rigid materials may also be used. When the plug material does not mix with the drug or the medium outside the drug delivery device, the plug will not disintegrate before the first drug delivery is due. In most drug delivery devices oily materials are very suitable because they do not mix with the watery gastro-intestinal environment or the drugs which are often supplied in a watery solution. 
     In a preferred embodiment of the medicine reservoir according to the invention, a nozzle is provided for partly filling the dispensing hole, the nozzle comprising the deformable plug. The main advantage of the use of the nozzle is that the same drug delivery device and medicine reservoir may be used for different drugs. Due to differences in, e.g., viscosity, different drugs may require dispensing holes with different dimensions (length and/or diameter). Different nozzles may be designed for different drugs, such that a dispensing hole with optimal dimensions is available for all drug types. The holes in those nozzles are filled with the plug according to the invention. The filled nozzle is then used for sealing the medicine reservoir. When the first amount of drug is to be delivered and the pressure inside the medicine reservoir increases, the plug will be pushed out of the nozzle. The resulting dispensing hole will then have the desired dimensions. 
     These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  schematically shows a drug delivery device with a medicine reservoir according to the invention, 
         FIG. 2  schematically shows a medicine reservoir according to the invention, 
         FIG. 3  shows the medicine reservoir of  FIG. 2  with the plug removed, 
         FIG. 4  shows a medicine reservoir with a nozzle comprising a plug, and 
         FIG. 5  shows a cross section of the medicine reservoir of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically shows a drug delivery device  50  with a medicine reservoir according to the invention. The drug delivery device  50  is a swallowable capsule comprising a drug to be released somewhere along the gastro-intestinal tract of a patient and an actuation mechanism for controlling the amount of drugs to be released and the moment of said release. Although the deformable and removable plug according to the invention is particularly advantageous in combination with swallowable drug delivery devices  50 , it is to be noted that it may also be used with implantable drug delivery devices. The drug to be released is stored in a compressible medicine reservoir  10 . The drug may, e.g., be stored as dry powder, dissolved in water or as a gel or liquid. An actuator means  12  is provided for compressing the medicine reservoir  10 , resulting in an increase of the pressure inside the medicine reservoir  10 . Instead of a compressible medicine reservoir  10 , a rigid reservoir may be used comprising a substance or element which is capable of increasing the pressure inside the reservoir. For example, a balloon filled with a swelling agent may be placed in the rigid reservoir. 
     The medicine reservoir comprises a dispensing hole  15  for allowing the drug to be pushed out of the drug delivery device  50  when the pressure inside the medicine reservoir  10  increases. The actuator means  12  may work mechanically using, e.g., a piston. Alternatively, the actuator means  12  may increase the pressure by sucking in water from the environment or by using chemical reactions for producing water or for expanding a volume of a swelling agent. The drug release may, e.g., be triggered by an internal clock, sensor values from a pH-sensor or trigger signals from an electrical or chemical detector element. If the drug delivery device  50  comprises means for wireless communication, the drug delivery may be externally triggered. The operation of all electronic functions of the device  50  is controlled by the processing electronics  17  and powered by a battery  16 . 
       FIG. 2  schematically shows (part of) a medicine reservoir  10  according to the invention. The medicine reservoir  10  is filled with a drug  13  and is partially enclosed by a housing  11  of the drug delivery device  50 . Here, the housing  11  of the drug delivery device  50  is also a wall of the medicine reservoir  10 . Alternatively, the medicine reservoir  10  may be a small bag inside the housing  11 . The medicine reservoir  10  is separated from the external environment of the drug delivery device  50  by a dispensing hole  15  in the housing  11  of the device. In this Figure, the dispensing hole  15  is blocked by a deformable plug  14 . The plug  14  prevents the drug  13  from leaking out of the medicine reservoir  10 . 
     The plug  14  may comprise an oil which does not mix with the drug  13  or the gastro-intestinal fluid outside the drug delivery device  50 . For example, a mineral oil or castor oil is very suitable for use as a plug  14 . Other non-rigid deformable materials may also be used. When the actuator means  12  of the drug delivery device  50  raise the pressure inside the medicine reservoir  10 , the deformable plug  14  will first be compressed and will then be pushed out of the dispensing hole  15 , followed by the first amount of drugs  13  to be released. 
       FIG. 3  shows the medicine reservoir of  FIG. 2  with the plug removed. When the actuator means  12  compress the medicine reservoir  10 , drugs  13  are pushed out through the dispensing hole  15 . 
       FIG. 4  shows a medicine reservoir  10  with a nozzle  31  comprising a plug  14 .  FIG. 5  shows a cross section of the medicine reservoir of  FIG. 4 . The main advantage of the use of the nozzle  31  is that the same drug delivery device  50  and medicine reservoir  10  may be used for different drugs  13 . Due to differences in, e.g., viscosity, different drugs  13  may require dispensing holes  15  with different dimensions (length and/or diameter). Different nozzles  31  may be designed for different drugs  13 , such that a dispensing hole  15  with optimal dimensions is available for all drug types. A thick gel does, for example, require a relatively wide dispensing hole  15 , while more liquid drugs require very narrow dispensing holes  15 . The hole  15  in the nozzle  31  is filled with a plug  14  as described above. The filled nozzle  31  seals the medicine reservoir  10 . When the first amount of drug  13  is to be delivered and the pressure inside the medicine reservoir  10  increases, the plug  14  is pushed out of the nozzle  31 . The dimensions of the dispensing hole  15  are defined by the design of the nozzle  31 . 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

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