Device for controlled drug delivery

FIELD OF THE INVENTION

This invention relates to a device for controlled drug delivery, the device comprising multiple drug reservoirs for comprising a drug, releasing means for releasing the drug from the drug reservoir and a controller for controlling the drug release.

BACKGROUND OF THE INVENTION

In US patent 3,692,072 a self-powered implanted device is disclosed, comprising a store of medicine in powdered, liquid or other dispensable form. The medicine is gradually discharged incrementally over a substantially long period of time. The medicine is comprised in capsules situated in cavities at the circumference of a wheel. Each cavity has an associated piston member for pushing the capsule out of the cavity. One capsule a day is released in this way. Due to the complex mechanical structure of this device, the amount of drug that can be stored in it is very small relative to the size of the device.

US patent 5,660,846 discloses an implantable device for the automatic delivery of an active ingredient according to an adjustable delivery profile. The device includes a reservoir for storing the active ingredient in a solid composition. An actuator moves the solid composition from the reservoir to a transit area. The solid composition exits the housing at the transit area. A controller acts on the actuator to adjust movement of the solid composition out of the housing according to the delivery profile. The solid composition is a cable-like carrier comprising a drug and rolled over a pin. The cable is slowly rolled out for moving the composition out of the housing. The rolling out of the carrier must be performed continuously, because otherwise water from the environment will diffuse into the device. The drug and the carrier are carefully selected and compounded in such a proportion that the drug is immediately released from the carrier upon contact with a liquid. Selecting and compounding of the drug-carrier combination is therefore a complex task.

It is a problem of those known drug delivery devices, that the amount of drug that can be stored in it (to be released later on) is relatively small compared to the space occupied by the mechanical and electronic parts of the device.

OBJECT OF THE INVENTION

It is an object of the invention to provide a device for controlled drug delivery, which device can store more drugs, using less volume.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, this object is achieved by providing a device for controlled drug delivery, the device comprising a rotatable drum, multiple drug reservoirs, a housing enclosing the drum, rotating means and a controller for controlling the rotating means. The drug reservoirs are arranged along a helical track at an outer surface of the rotatable drum. The housing comprises an opening for enabling release of a drug from one of the drug reservoirs to a surrounding tissue. The rotating means are arranged for rotating the drum in order to bring a drug reservoir in front of the opening. Releasing means are provided for releasing the drug from the drug reservoir in front of the opening. Compared to the planar arrangement of the drugs in the known drug delivery devices, the drug delivery device according to the invention saves space by bending the plane with the drug reservoirs in a cylindrical shape (at least in the shape of a rotatable drum). In theory this would save a factor π (3,14159). The invention thus makes it possible to put more drugs in a smaller device. For implantable drug delivery devices this is very advantageous. The arrangement of drug reservoirs along the helical track makes it very easy to put the reservoirs in front of the opening in the housing, one by one, by just rotating the drum. The controller controls the rotating means, and therewith the time scheme for the drug delivery.

In a preferred embodiment, the rotating means and/or the controller are at least partially situated inside the rotatable drum in order to further reduce the size of the device relative to the amount of drugs it can comprise.

The releasing means may be realized in many different ways. Some exemplary embodiments are described below in the detailed description of the invention.

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 an embodiment of the drug delivery device according to the invention,

Fig. 2 shows a further drug delivery device according to the invention, Fig. 3 shows a releasing mechanism comprising a strip for closing the drug reservoirs,

Fig. 4 shows a releasing mechanism comprising a cutting part, Fig. 5 shows a releasing mechanism based on a narrowing of the available space for the drug reservoir, and

Fig. 6 shows the releasing mechanism of Fig. 5 from another point of view.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 schematically shows an embodiment of the drug delivery device 10 according to the invention. The device 10 comprises a housing 13 with an opening 14. Inside the housing 13, a rotatable drum 11 is located. The rotatable drum 11 is preferably cylindrical, but other shapes may also be used. At the surface of the drum 11, a plurality of drug reservoirs 12 is arranged. The reservoirs 12 are arranged along a helical track. One of the drug reservoirs 12 is situated in front of the opening 14 in the housing 13. A releasing mechanism (not shown in Fig. 1) close to the opening, releases the drug from the drug reservoir 12. Some mechanisms for releasing the drug are described below with reference to Figs. 3 to 6.

When it is time for a new drug dose to be released, the actuator 15 rotates the drum 11, such that the empty reservoir 12 moves away from the opening 14 and a drug filled reservoir 12 moves in front of the opening 14. The releasing means then releases the drug from the drug filled reservoir 12. If the releasing of the drug results in any waste material, e.g., (part of) an empty drug reservoir 12, then the waste material is preferably collected in a waste collection space 17 inside the device. The actuator 15 may be motor-driven, electro- magnetic based, osmotic pressure based, etc.

Electronic circuitry 16 is provided to rotate the drum 11 according to a predetermined time schedule. If the electronic circuitry 16 also comprises a transmitter/receiver for communicating with external control equipment, the device 10 may be programmed and reprogrammed after it has been implanted in a patient. The device 10 may further comprise one or more sensors for monitoring some biological parameters of the tissue in which the device 10 has been implanted or for monitoring the functioning of the device 10. The sensor output may, e.g., be used for triggering drug delivery or for adapting the drug release schedule. Such adaptations may be performed by the electronic circuitry 16 or by a user after receiving the obtained parameters via a transmitter/receiver. The electronic

circuitry 16 and the actuator 15 are powered by a power source (e.g. a battery). Preferably, the battery, the electronic circuitry 16 and the actuator 15 are partially or fully situated inside the drum 11 for further reducing the size of the device 10.

The device 10 delivers medication to the surrounding tissue or fluid. The surrounding fluids into which the substances are released can be, for example, environments such as intravenous infusions, interstitial fluids and stomach and intestinal juices. In another embodiment the fluid into which the drug is dissolved is provided by the device 10 itself (e.g. stored in an extra reservoir), which with the help of a catheter may be brought to the desired treatment location. The drum 11 with the drug may be suspended in a non-solvent (e.g. oil), which protects the drug from the surrounding watery environment.

Fig. 2 shows a further drug delivery 10 device according to the invention. In addition to the features already described with reference to Fig. 1, this drug delivery device 10 comprises a compressible carrier fluid reservoir 21 for compensating for the pressure difference caused by releasing the drug from the device 10. If this pressure difference is not compensated for, water from the device's surrounding environment may enter the housing 13 and deteriorate the functioning of the device 10. The carrier fluid reservoir 21 may comprise a reservoir fill port 22 for filling the carrier fluid reservoir 21 with additional fluid in order to minimize the pressure difference between the device 10 and its environment. The device 10 of Fig. 2 further comprises a catheter 23 for transportation of the released drug from the opening 14 in the housing 13 to the environment of the device 10.

As described above, releasing the drug from the drug reservoir 12 may be performed by a variety of releasing mechanisms. For example, the fluid reservoir 21 may provide a fluid for dissolving the material of the drug reservoir 12 in order to release the drug from the reservoir 12. Some other exemplary releasing mechanisms are described below with reference to Figs. 3 to 6.

Fig. 3 shows a releasing mechanism comprising a strip 31 for closing the drug reservoirs 12. The reservoir 12 is a medicine bag, which is protected by a strip 31. The drug is released by pulling off the strip 31. The pulled-off strip 31 may be collected in the waste collecting space 17. The pulling off is performed mechanically and is preferably a direct result of the rotating of the drum 11. Alternatively, a separate actuator performs the pulling. This actuator may also be controlled by the electronic circuitry 16. In the cross section shown in Fig. 3, only a few drug reservoirs 12 are drawn. Due to the spiral arrangement of the drug reservoirs 12, not all drug reservoirs 12 are visible in one cross section.

Fig. 4 shows a releasing mechanism comprising a cutting part 41. This embodiment is based on "tea-bag- like"- formed drugs bags 42, made of water soluble material. Inside of the device, between the drum 11 and the housing, oil is present that protects the bags 42 against water. Once cut loose by the cutting part 41 the drug bags 42 will 'transport' to the human body tissue where water causes the bags 12 to degrade. After this degradation the drug is finally active and providing a therapeutic effect.

Fig. 5 shows a releasing mechanism based on a narrowing 51 of the available space for the drug reservoir 12 and Fig. 6 shows the releasing mechanism of Fig. 5 from another point of view. This embodiment is based on a drug bag 12 with a drug 61, which is pressed into a pyramidal form or another form with sharp corners. A small region 51 of the envelope of the device is made flat so that the drum 11 will squeeze the drug 61 against the wall of the reservoir 12. Since the drug 61 itself has sharp edges it will break the shell of the reservoir 12 and will be released. In another modification other sharp objects (attached to the shell or loose) might be used for cutting through the shell instead of the drug 61 itself. 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.