Metering device for a medicament

Dosing device for a drug

The invention relates to a metering device for a medicament, which is stored in a non-liquid form in a memory and for application to a patient this is supplied by means of a conveyor for a long time via an outlet opening.

In the case of a dosing device, for example for insulin, it is important to spare the patient, as long as possible, the path to the doctor or the refilling of the drug into the reservoir by the patient himself. In an implantable or externally portable on the body dosing device, it is appropriate to use the available memory for the drug in the best possible way. Since medicaments can be produced more concentrated in solid form than in liquid form, it is expedient to store the medicament in solid form in the metering device. The main reason for the use of solid drugs would be their usually longer shelf life under the conditions of use of a metering device.

In DE-OS 2,721,752 a metering device of the type mentioned is described, which is implantable. In this dosing device liquid is sucked by means of a pump, which flows around the drug present as a solid block. As a result, parts of the drug are dissolved in the liquid. The liquid thus added to the medicament is then brought to the application site in the patient via an outlet opening on the housing, which can be extended by a catheter. The electric pump used is driven by a battery and controlled by a control unit. The problem with this Dosiorworrichtung is to keep the dissolved content of the solid drug in the liquid constant, ie regardless of the flow rate, the temperature and the composition of the liquid.

US Pat. No. 3,995,632 describes an implantable dosing device in which a thixotropic drug is administered to a patient for an extended period of time. The term "thixotropic substance" is understood to mean a jelly-like or paste-like substance which is solid without the action of force and liquid above a certain, substance-specific force effect. In the metering device according to this US patent, the force required for the dosing process is obtained by osmosis. In a device of this type there is the disadvantage that the metering rate depends on the osmotic pressure of the fluid used, wherein the metering rate is not controllable. A control according to program according to the times of day or a sensor-controlled dosage, which takes into account the current data of the patient, is therefore not possible.

Object of the present invention is to avoid the mentioned solution fluctuations in a dosing device of the type mentioned with non-liquid drug in the memory, while at the same time should be taken to ensure that the controllability of the dosage is possible that the occurring in a drug in liquid form Problems of instability are avoided, and that a concentrated storage of the drug is possible, that the refilling of the drug for longer periods is eliminated.

This object is achieved in that the conveyor for time-variable transport of the drug is set up in a non-liquid form, the delivery rate is controlled as needed.

The advantages associated with the invention are that fluctuations in the drug concentration are avoided at the site of application, since the non-liquid, known in the composition drug itself in unresolved form, that is unchanged, transported by the conveyor to the application site, and that this process by the controller adapted in the course of time to the needs of the patient. For a diabetic patient eg eliminates the need to manually administer additional doses of insulin when the sugar level in the blood increases. The delivery rate automatically set higher by the controller in this case relieves him of the annoying self-monitoring and additional insulin delivery.

In the accompanying drawings three embodiments of the invention are shown, which are described in more detail below. Identical components are provided in the figures with the same reference numerals. FIG. 1 shows the basic structure of a first metering device in section, in which a powdered medicament is transported by means of a motor-driven delivery spindle, FIG. 2 3 shows the basic structure of a third metering device in section, in which a jelly or paste-shaped medicament is pressed out of a hose by means of two rollers ,

FIG. 1 shows a first metering device with which a medicament 1 is supplied to a patient, ie a human or animal body, for a prolonged period of time at a specific application site. The metering device comprises a capsule or a housing 2, which houses all structural components.

The housing 2 consists of a compatible with the human or animal body material, eg

Stainless steel or titanium. In the housing 2 there is an outlet opening 3 for the medicament 1, which can optionally be displaced by a catheter (not shown) to the desired application site. Otherwise, the housing 2 is hermetically closed. It is thus suitable for implantation. At the outlet opening 3 is the output end of a housed in a tubular body 4 feed screw 5, which is provided with an electric drive 6 or motor. With the drive 6, an electrical control unit 7 is electrically connected. The control unit 7 and the drive 6 are fed from an electrical energy source, in this case from a battery 8. The delivery spindle 5 serves as a delivery device for the medicament 1.

For filling the tubular body 4 in the area around the feed screw 5 with the medicament 1, the body 4 adjoins a reservoir or a storage 9 on one side. In this memory 9, the drug 1 is stored in powdery, ie solid form. A Nachschiebe- or printing device 10 causes a constant refilling of the turns of the feed screw. 5

The memory 9 is a tubular member which opens at the outlet side 11 with a conical, ie tapered end 12 into the body 4. This tail 12 facilitates drug delivery.

The pressure device 10 may comprise a spring 13 or a bellows (not shown), which is supported on the inner wall of the housing 2 and thereby presses against a piston 14 which is housed in the rear part of the memory 9 on the outlet side 11 facing away from side 15 ,

The drug 1, for example, pure insulin in a finely crystalline structure or eg crystalline insulin, which is stretched with a placebo substance such as glucose to a desired concentration is introduced into the memory 9 and held there with the pressure device 10 under pressure. By the pressure device 10, the drug 1 is pressed against the feed screw 5.

During the dosing process, it constantly replenishes their empty turns. The feed screw 5 transports the drug 1 in its powdery form. The full turns of the feed screw 5 are emptied during rotation at the outlet opening 3.

The metering rate is adjustable via the rotational speed of the feed screw 5. This rotational speed is predetermined by the drive unit 6 by the control unit 7.

The control unit 7 can be programmable, so that the patient at certain times of the day more and at other times less drug 1 feeds.

The control unit 7 may also be sensor-controlled, ie a sensor 50 determines the interest instantaneous value, a comparator compares selbigen with a desired value, and the control unit 7 determines from the difference the necessary speed of the feed screw 5. The sensor 50 may be, for example, a Glucose sensor act when the metering device is intended for the long-term administration of insulin. Control units 7 of the type described are known in the field of control technology.

In the dosing device described so far, the medicament 1 present in powder form, if it is hydrophilic, would attract body fluid via the outlet opening 3, which could reach the reservoir 9 via the delivery spindle 5. As a result, there would be a risk that the medicament 1 would liquefy and would be expelled uncontrollably into the body under the action of the pressure device 9 as a slightly viscous liquid through the feed screw 5.

To prevent this, the powdered medicament 1 is either hydrophobicized (eg by treatment with silicone, paraffin or endogenous oil or fat), or it is admixed with a hydrophobic or hydrophobized additive. The hydrophobic additive must be present in such an amount that the individual parts or crystals of the medicament 1 are not in continuous contact. A hydrophobized or hydrophobic substance is understood to be a substance which acts water-repellent. The additive and the hydrophobing substance must either be degradable in the body medium or, if supplied only in small amounts, be physiologically harmless.

FIG. 2 shows a second metering device for a non-liquid medicament 1. In this case, the outlet opening for medicament 1 designated by 3a is displaced by a catheter 16 to the site of application. In the inlet opening of the catheter 16, the output of a peristaltic pump 17, which is provided with an electric drive 6 opens. The catheter 16 is connected in a liquid-tight manner by means of a coupling 18 to a housing connection piece at a housing outlet opening 3a. Connected to the drive 6 is a control unit 7. The control unit 7 and the drive 6 are fed by a battery 8 again. The control unit 7 and the drive 6 are designed as in FIG. At the inlet side of the peristaltic pump 17, a memory 9 connects. The interior 19 of the housing 2 is subjected to overpressure.

Thixotropic, ie gelatinous or pasty substances, are preferably used as medicament 1 in this metering device. As already mentioned, thixotropic substances are substances which, in the normal state, are solid without the action of deformation forces, flow under the action of a substance-specific force and solidify again when the deformation forces are suspended. Such materials include, in principle, metals that in the plastic range, ie at very high forces, flow, which are not meant here. Here, thixotropic substances are understood to be jelly-like substances and pastes which are non-liquid in the non-reactive state and flow at certain substance-specific deformation stresses.

It may be both organic and inorganic substances. For such substances, Figure 2 shows the preferred embodiments.

When using a thixotropic substance as medicament 1, the reservoir 9 may be a tubular body.

But he can also be a metal bellows. Instead, he may also have a bag-like appearance with a wall made of an elastic material, eg. B. it may be a plastic bag. Such a memory 9 is shown in FIG. On this plastic bag act by means of a printing device from the environment Auspreßkräfte. In the illustrated preferred case, a gas is filled in the housing 2 and maintained at overpressure. Thus, all-sided Auspreßkräfte are effective. The Auspreßkräfte can instead be caused by a vaporizing liquid, a spring or by the inherent elasticity of the memory 9.

In the illustrated embodiment of Figure 2, the peristaltic pump 17 is used as a conveyor for the gelatinous or pasty drug 1. Such peristaltic pumps are known for example from DE-PS 26 51 962. As an alternative conveyor but here also shown in Figure 1 feed screw 5 in question.

FIG. 3 shows a third metering device which is set up for thixotropic substances. A housing 2 has a housing outlet opening 3a, from which an elongate tube 20 acting as a storage 9 is brought out. The tube 20 contains the thixotropic medicament 1 The tube 20 is accommodated without knotting in a chamber 21 in the upper part of the housing 2. Preferably, it is wound on a drum 51. But it can also be laid serpentine in the chamber 21. The one end of the hose 20 is guided between two rotatable rollers 22 lying in the same plane. A partition 23 separates a lower chamber 21a for the empty tube part from the upper chamber 21 for the still filled tube part.

The lower chamber 21a is thus a storage space for the empty tube part. The two rollers 22 are connected to an electric motor drive 6. In principle, it is sufficient if only one of the two rollers 22 is driven. The drive 6 is controlled by an electrical control unit 7. The self-or externally controlled control unit 7 and the drive 6 are powered by a battery 8. This embodiment corresponds in principle to that of FIG. 1.

In this metering device, the deformation pressure, which causes a flow of the drug 1, achieved in that under control of the control unit 7, the drive 6 is activated and squeezed upon rotation of the rollers 22 of the tube 20. The pressure continues inside the tube 20 as far as the outlet opening 3a, so that the medicament 1 is pushed out there at the site of application and is thus available for the treatment of the body.

The metering devices according to FIGS. 1 to 3 can preferably be embodied as implantable metering devices. But they can also be externally portable dosing devices.

27 Claims 3 figures