Implantable, refillable infusion device

ES 2 277 604 T3

DESCRIPTION

Implantable, refillable infusion device.

Technical field

The invention relates to implantable infusion devices for in vivo controllable administration of drugs to a patient.

Background of the invention

Implantable infusion devices that provide a patient with an in vivo source of a drug to be administered, in a device that allows controlled administration of the drug over a predetermined period of time. Certain drugs, such as chemotherapy drugs and opioids, can be highly effective when given at a constant dose rate rather than at discrete intervals.

A typical infusion device or pump includes a hermetically sealed outer housing that contains a vapor pressure fluid or other means to exert a compressive force on a compressible or flexible inner drug reservoir that communicates with a drug delivery port. Alternatively, the drug may be arranged in the outer housing, with a propellant arranged in the inner housing. When the outer housing is filled with drug, the propellant contained in the inner housing is compressed and changes its state from vapor to liquid, thus recharging the drive mechanism of the device. In still other embodiments the outer housing may be divided into two chambers separated by a liquid impermeable diaphragm. One chamber contains the drug and includes a drug delivery port, and the other chamber contains a propellant or spring member to exert a force against the diaphragm to expel the drug through the delivery port.

The infusion device has to meet numerous requirements for safety and efficacy. For example, the housing material must not react with bodily fluids or with drugs and propellants contained within the housing. Furthermore, the flexible membrane or barrier between the chambers must not leak and must be impermeable to fluids in the gas phase to prevent contamination of the drug with the propellant. Since the device is designed for implantation in a patient, great care must be taken to prevent any leakage of drug or propellant into the patient's body. In addition, the device is desirably as small and lightweight as possible in order to cause minimal invasive trauma, discomfort, and disfigurement to the patient, and yet must be large enough to provide a useful therapeutic dosage of the drug that being administered and minimize the frequency with which the device has to be recharged. It is desirable to make the pump refillable so that it does not need to be surgically removed and replaced when the drug is depleted. However, the refillability of the pump requires a port that is outside the skin or transcutaneously accessible without introducing infection or compromising the release of an excessive and potentially harmful amount of the drug to the patient. Also, in devices in which a propellant is contained within a flexible bag that expands and contracts in response to changes in propellant pressure, it is necessary to ensure that the introduction of the drug into the surrounding drug reservoir propellant bag is not impeded by the presence and location of the bag in the reservoir and / or does not puncture or pinch the bag. Thus, it may be necessary to secure the thruster chamber or bag to the housing to avoid such problems. There is the additional problem of ensuring that the drug reservoir can be completely depleted and refilled to achieve optimal device efficiency.

Delivering a desired dosage of a drug over a period of time may require a constant controllable flow of drug from the device. However, as the drug in the reservoir is depleted or if the force exerted on the drug reservoir cannot be controlled, a constant dose rate can be difficult to sustain.

US Patent No. 3,840,009 to Michaels et al. describes a vapor pressure drug delivery device having two chambers separated by a flexible wall or blister. The outer chamber contains a drug to be administered to a patient and the inner chamber contains a fluid under pressure that expands to conform to the shape of the outer chamber, thus allowing the expulsion of substantially all of the drug contained within the outer chamber. The pressurized fluid is maintained at a positive pressure at the temperature at which the device is used, so no external power source is required.

US Patent No. 5,167,633 to Mann et al. describes a medication infusion pump in which constant pressure is exerted on a liquid medication to be administered. The pump includes a pressure reservoir in the form of a hollow enclosure with at least one flexible wall to contain a fluid under pressure. The medication to be administered is outside the pressure reservoir. The fluid under pressure undergoes a phase change from liquid to vapor to expel the drug from the pump. The device of Mann et al. it is maintained at a negative pressure at the temperature of use to prevent leakage of medication from the pump to the patient.

US Patent No. 5,514,103 to Srisathapat et al. describes a medication infusion pump that includes a drug reservoir and a pressurized fluid reservoir that are separated by a movable wall or a flexible bag. The pressurized fluid reservoir includes a spacer to prevent contraction of said pressurized fluid reservoir below a minimum volume that is slightly greater than the volume of the liquid phase of the pressurized fluid, thereby allowing a portion of the fluid to Pressure always remains in the vapor phase. As a result, even when the drug reservoir is completely filled, the fluid under pressure is not fully in the liquid phase. Thus, no additional energy is required to restore a vapor phase.

US Patent No. 3,951,147 to Tucker et al. discloses a refillable implantable infusion pump in which a drug-bearing bellows is contained within a housing that is filled with a pressurized fluid or propellant. The Tucker et al. It includes a filtering chamber to ensure the removal of residues of the infused drug prior to its administration to the patient.

US Patent No. 5,045,064 to Idriss

ES 2 277 604 T3 describes an implantable constant pressure pump employing shape memory metal bands around a reservoir containing a fluid to be infused. The bands compress the reservoir containing the fluid to be infused, thus eliminating the need for a propellant.

US Patent No. 5,395,324 to Hinrichs et al. describes an infusion pump having a primary inlet port leading to a drug reservoir, a separate bolus port leading to a bolus chamber, and means for ensuring that the bolus chamber is not inadvertently filled with the intended drug. for the primary drug reservoir.

Otto US Patent No. 5,769,823 discloses an implantable infusion pump comprising a plastic housing, a bellows chamber that encloses a propellant, and two separate elastic plastic bags that enclose an infusion, that is, an infuse. The bags are surrounded by glycerin or the like that combines with any propellant that passes through the wall of the bellows into the housing, thus preventing passage of the propellant through the housing to the patient.

US 5176644 by Srisathapat et al. discloses an implantable medication infusion pump that utilizes a simplified and improved pressure reservoir to maintain a selected medication in liquid form within a pump housing under substantially constant pressure. The pressure reservoir comprises a hollow structural enclosure that has at least one flexible resilient wall and is adapted to be filled with a selected quantity of a pressurized fluid, such as a selected fluorocarbon in a liquid-vapor state, prior to mounting the reservoir as a structural unit within the infusion pump housing. Within the pump housing, the flexible wall of the reservoir defines one side of a medication chamber, the pressurized fluid undergoing an appropriate change of state to expand or contract the reservoir in a manner that maintains the medication under substantially constant pressure. The reservoir can be supplied in a variety of structural shapes and / or used in pump housings of various sizes and shapes to allow the pump to be reduced in size, or, alternatively, to increase the medication capacity of the pump without increase the size of the housing of said pump.

US Patent No. 5,575,770 to Melsky et al. describes an implantable infusion pump having a valve actuated bolus delivery chamber. Inadvertent administration of an overdose to the patient through the bolus delivery chamber is prevented by a design that requires the use of a lateral access delivery needle that is inserted through a pair of septa that are spaced from each other to define a bolus chamber. The tip of the needle extends beyond the lower septum and presses a lever to actuate the normally closed valve. The side opening of the needle is disposed between the septa in the bolus chamber for delivery of the bolus dose to the bolus chamber. The design prevents delivery of erroneous doses by requiring simultaneous valve opening with drug delivery to the bolus using a lateral access delivery needle.

It would be advantageous to provide an implantable infusion pump that is simple in construction and operation, is made of lightweight materials, is inexpensive to manufacture, is effective in administering medicine, and is easy to refill.

Summary of the invention

The essential and optional features of the present invention are set forth in the main claim and the accompanying dependent claims, respectively.

An implantable infusion device is disclosed having a housing that includes an inner wall and having an inner region defined at least in part by the inner wall. At least a portion of the interior region defines an infuse reservoir adapted to store an infuse therein for administration to a patient. A closed chamber of variable volume is disposed within the interior region of the housing. The variable volume chamber contains a pressure source.

In one embodiment, an infuse refill fluid flow path is present which is arranged and adapted to transport infuse from a first point external to the housing to a region adjacent to the internal portion of the housing to refill the infuse reservoir.

In a second embodiment an infuse refill fluid flow path is present which is arranged and adapted to transport infuse from a first point external to the housing to the infuse reservoir. An outlet fluid flow path is arranged and adapted to transport infuse from the infuse reservoir to a second point external to the housing. A bolus port is provided in the device in fluid communication with the outlet fluid flow path.

The variable volume chamber is free floating within the interior region of the housing, and in a third embodiment a fluid flow path is provided for transporting infuse between a point external to the housing and the interior region of the housing. A spacer is supported in at least one of the housing and the variable volume chamber to maintain the fluid flow path in an unobstructed condition.

The device housing can be of any shape and is preferably made of a biologically inert material. The variable volume chamber supported within the housing is freely floating. The variable volume chamber can be any such device known to those of ordinary skill in the art, such as an accordion-type bellows, bag, or envelope. A fluid or infuse may be contained by the remaining space or main reservoir in the interior region of the housing. The variable volume chamber contains a source of pressure that will cause the chamber to expand and expel fluid from the housing through an outlet fluid flow path. Preferably, the refill fluid flow path extends from a point external to the housing to the main reservoir. The refill fluid flow path has an inlet port that can be sealed by a self-sealing septum and is intended to fill the main reservoir of the housing with infuse. The refill fluid flow path is preferably located in a coupling region between the variable volume chamber and the housing. The way can be 3

ES 2 277 604 T3 consists of a channel to help disperse the fluid towards the main reservoir. Preferably, the refillable fluid flow path includes a fluid dispersion flow path in the coupling region.

A separate bolus port may be provided in the implantable infusion device. The bolus port has direct access to the outlet fluid flow path, thus bypassing the main reservoir actuated by the pressure source. A self-sealing septum may also be arranged in the bolus port. Preferably, the bolus port includes two self-sealing septa spaced from one another that form a bolus reservoir between them such that a special delivery needle with an opening offset from the needle tip is used to deliver fluid to the reservoir. bolus.

According to one embodiment of the invention, there is provided an implantable infusion device comprising a housing having an annular portion with an inner wall defining an inner region having a width dimension D and extending along a central axis. , a lower portion extending from the annular portion and encompassing a first end of the inner region, and an upper portion extending from the annular portion and encompassing a second end of the annular region and facing the lower portion, the interior region being substantially closed. The device further includes a closed hollow fluid impervious bellows. The housing includes a refill fluid flow path from points external to the housing to a region adjacent to the central portion of the portion of the housing from which the bellows extends. The housing further defines a fluid flow path that extends from the region between the bellows and the annular portion of the housing to points external to the housing.

The device may include a pierceable self-sealing septum disposed in the recharge fluid flow path and may further include a recharge fluid reservoir disposed along the recharge fluid flow path. The septum can be removable from the housing.

The device may include at least one of a flow restrictor and / or filter disposed along the fluid outlet flow path.

In one embodiment the housing is made of a gas-impermeable material and the bellows enclosing the pressure source is made of a substantially rigid, gas-impermeable material. In a preferred embodiment the bellows is hermetically sealed.

The pressure source comprises one or more elements from the group consisting of multi-phase fluids, springs, shape memory metal alloys, Belville washers, and compressible materials. In one embodiment, a multi-phase fluid propellant is present in at least one of a liquid phase and a gas phase within the variable volume region of the bellows as a function of ambient temperature. Conversion of the propellant fluid from a liquid phase to a gas phase increases the volume displaced by the bellows in the interior region of the housing, thus exerting forces on a fluid external to the bellows contained in the housing in order to provide a substantially constant flow rate of the fluid. through the fluid outlet flow path.

In one embodiment the propellant is disposed in the variable volume region of the bellows at a pressure that is not less than atmospheric pressure at room temperature.

In one embodiment the central portion of the bellows is offset relative to the plane of the annular peripheral portion of said bellows. A central region of the portion of the housing from which the bellows extends is correspondingly offset from the plane of the annular portion of the housing. The displaced central region of the housing is accommodated substantially within the displaced central portion of the bellows.

In one embodiment the housing and the bellows are cylindrical.

The device may further include a separate bolus port in fluid communication with the fluid outlet flow path. The bolus port may include a pair of septa that are spaced from one another to define a bolus reservoir between them. A side access delivery needle with an opening near the center of its length is required to deliver a bolus dose of the infusion to the bolus reservoir.

In one embodiment the bellows extends from the upper portion of the housing. In another embodiment the bellows extends from the lower portion of the housing.

According to another embodiment, an implantable infusion device is provided comprising a housing having an annular portion with an inner wall defining an inner region having a width dimension D and extending along the central axis, a lower portion extending from the annular portion and encompassing a first end of the inner region, and an upper region extending from the annular portion and encompassing a second end of the inner region, the upper portion facing the lower portion and the inner region being substantially closed. The device further includes a fluid impervious closed hollow bellows disposed around a region of variable volume and having an upper member, a lower member, and a plurality of serially coupled annular members extending between them. The joints of the coupled annular members are flexed coupled. The bellows has a maximum outer width dimension D ', where D' is less than D. At least one of the upper and lower members includes a substantially flat annular peripheral portion disposed around a central portion. A pressure source is contained within the variable volume region of the bellows, and the bellows is disposed within the interior region of the housing, with one of the upper and lower members facing the housing. The annular members of the bellows are spaced from the annular portion of the housing. The housing includes a refill fluid flow path from points external to the housing to a region adjacent to the central portion of one of the upper and lower members of the bellows. The coupling region between the housing and the bellows defines a fluid dispersion flow path from the region adjacent to the central portion of the coupled member of the bellows to a region between the annular members of the bellows and the annular portion of the housing. The housing further defines a fluid outlet flow path extending from

ES 2 277 604 T3 the region between the bellows and the annular portion of the housing to points external to said housing.

In one embodiment a central portion of at least one of the upper and lower members of the bellows is offset relative to the plane of the annular peripheral portion of the upper and lower members of the bellows. A central region of the portion of the housing that is coupled to the bellows is correspondingly offset from the plane of the annular portion of the housing, so that the offset central region of the portion of the housing that is coupled to the bellows is accommodated within the central portion. of the coupled portion of the bellows.

According to yet another embodiment, a septum replacement kit is provided for an enclosed device that is sealed with a septum, wherein the enclosed device defines a fluid reservoir, a fluid flow inlet, and a fluid flow outlet. . The kit comprises a compressible septum adapted to be applied with sealing action at the fluid flow inlet of the reservoir and a septum installation tool adapted to compress the septum to a nominal insertion size, maintaining the nominal insertion size of the septum before installation of the latter and install the septum at the fluid flow inlet of the reservoir.

The septum installation tool preferably comprises a tubular member adapted for insertion into the fluid flow inlet of the reservoir, an opening in the tubular member for insertion and retention of the septum therein, and a plunger member that may be disposed in the tubular member for expulsion of the septum of said tubular member. Insertion of the septum into the tubular member compresses the septum. Expulsion of the septum from the tubular member into the fluid inlet reservoir allows the septum to expand to fill and seal the fluid inlet reservoir.

The septum is preferably made of a self-sealing pierceable elastomeric or rubbery material.

These and other objects and advantages of the invention will become in part apparent and will appear in part in the following. Accordingly, the invention comprises the apparatus having the construction, combination of elements and arrangement of parts that are exemplified in the following detailed description, the scope of which will be indicated in the claims.

Brief description of the drawings

For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a perspective view of an infusion device in accordance with an illustrative embodiment of the invention;

Figure 2 is a schematic diagram of the device illustrating the structure and principles of operation;

Figure 3 is a sagittal view of the device of Figure 1;

Figure 4 is a sagittal view of an alternate design of the device, in which the lateral bolus port is positioned at an angle at a peripheral edge of the device;

Figure 5 is a sagittal view of a replaceable septum in a device in accordance with an illustrative embodiment of the present invention;

Figures 6A-6C illustrate one embodiment of a septum replacement kit with the steps for installing a replacement septum with a septum replacement tool;

Figures 7A-7B illustrate one embodiment of a bolus port safety feature that prevents inadvertent administration of a drug overdose to the patient through the bolus injection port; Y

Figure 8 does not illustrate the invention.

Like features in the drawings are indicated by like numbers.

Preferred description of the drawings

The infusion device of the present invention can be configured to have a relatively low profile, as shown in Figures 1, 3, 4, and 8. The device may include a housing formed of a lightweight, biologically inert material that need not be hermetically sealed. This is because, unlike most prior art infusion devices, the pressure source in the present device, which can be a propellant fluid, mechanical spring, or the like, or a combination of such elements, is contained in a separate closed container within the device housing, and the infuse or drug to be delivered is stored outside the container containing the pressure source.

The pressure source container may be in the form of a variable volume container, such as a mechanical bellows, a flexible bag or an envelope or any other suitable variable volume container apparent to one of ordinary skill in the art. However, unlike an expandable balloon bag, the variable volume container can have a defined maximum and minimum volume. The infuse is administered to the patient from the device upon expansion of the variable volume container within the interior region of the housing until said variable volume container effectively fills the interior volume of the housing, at which time the infuse is substantially depleted.

The device can also be reloaded transcutaneously with infusion without requiring the device to be removed from the patient. Infuse refill effectively recharges the pressure source by compressing the variable volume container to a reduced volume and creating a pressure that is used to expel the infuse from the device.

The device may also include a separate bolus injection port for the introduction of a bolus dose into the patient that bypasses the delivery of the pressure source-induced infusion from the main reservoir of the device. Self-sealing pierceable septa, through which infuse can be injected into the device, may be located in the primary and bolus ports of the device for convenient introduction and containment of infuse and bolus injections.

In addition, because the housing can be made of a lightweight material, such as plastic, many features, such as fluid flow channels, compartments, needle stops, and suture loops, can be integrated into the housing during manufacture. which can be done by molding or other low-cost, high-volume manufacturing processes.

Figure 1 shows a perspective view of a

ES 2 277 604 T3 infusion device 10 according to an illustrative embodiment of the invention. Figure 2 schematically illustrates the basic structure and the operating principle of the device. Figure 3 is a detailed sectional view of the device of Figure 1 along a sagittal (vertical longitudinal) axis. Figure 4 is a sagittal view of an alternate design of the device, in which the lateral bolus port is positioned at an angle to an upper edge of the device. Figure 5 is a sagittal view of a replaceable septum for the device. Figures 6A-6C illustrate one embodiment of a septum replacement kit and a method of using it to remove a spent septum and replace it with a new septum. Figures 7A-7B illustrate one embodiment of a bolus safety feature that prevents inadvertent delivery of a major dose of drug to be infused through the bolus injection port. Figure 8 is a sagittal view of another illustrative embodiment of the device according to the present invention.

Device 10 includes a housing 12 that may be made of a lightweight, durable, and biologically inert material, such as plastic. The housing may be formed of an upper housing 12a and a lower housing 12b that are joined with an O-ring 14 disposed between them to create a fluid impervious seal. The housing halves can be joined by, for example, ultrasonic or thermal welding, solvent bonding, or another form of adhesive-based bonding.

The device housing defines an interior region 15 that forms a main reservoir 16 for infusion 18, which is typically a drug to be administered over a period of time at a constant low dose to a patient in whom the device has been surgically implanted. . The infuse is introduced into the main reservoir through a main inlet port 20 which is sealed with a self-sealing pierceable septum 22. The infuse is delivered from the main reservoir to a catheter 24 through an outflow path 25.

Along the outflow path, a filter 26 may be arranged to remove particles from the infuse as it is being delivered from the main reservoir. It is to be appreciated that the device can employ any suitable filter apparent to one of ordinary skill in the art.

Along the outflow path, a flow restrictor 28 may be provided to regulate the flow of the infuse from the reservoir to the patient for a predetermined period of time. The device can use any suitable flow restrictor apparent to a person skilled in the art. For example, the flow restrictor may include a glass capillary flow restrictor, a chemically etched silicone wafer restrictor, and the like.

It is to be appreciated that the flow restrictor may also include a programmable flow control device, as would be apparent to one of ordinary skill in the art. Thus, the device can be pre-programmed or reprogrammed to deliver certain dosages to the patient.

In a preferred embodiment of the invention the device may include a separate restrictor chamber in the upper housing 12a. This separate restrictor chamber allows the use of interchangeable restrictors to set different infuse rates.

The delivery of the infuse from the main reservoir is induced by a pressure source P contained within a closed chamber 30 of variable volume. The chamber is freely floating within the housing. The pressure source can be a multi-phase fluid that expands from a liquid phase to a gas phase with increasing temperature, thus increasing in volume and pushing against the walls of the variable volume vessel to enlarge it, thereby decreasing the volume. of the main reservoir 16 and expelling the infuse therefrom from the device. Alternatively, the pressure source can be a mechanical device, such as a spring or other compressible member, or a shape memory metal alloy. A combination of a propellant fluid and a compressible mechanical member can also be used to obtain a desired infuse delivery rate from the device. The mechanical member can exert a constant force throughout the range of its stroke, but it does not have to.

If a propellant fluid is used as a source of pressure within the variable volume chamber, the chamber can be configured with a minimum volume that is greater than the liquid volume of the propellant fluid, so that the propellant fluid contained in the chamber remains in both liquid and gas phases when the chamber is compressed to its minimum volume. Furthermore, it may be desirable to select a propellant fluid that is at a pressure of not less than one atmosphere at room temperature, so that at the temperature of use (typically the nominal temperature of the patient's body) the propellant is at a pressure that is even higher than one atmosphere pressure. This allows the surgeon to prime and operate the device at room temperature in order to verify its performance before implantation of the device in the patient, thus eliminating the need to warm the device and infuse to body temperature. Furthermore, such a positive pressure device substantially reduces the risk of external air or gases being drawn into the device during storage of the device. In one embodiment, the propellant fluid may include a refrigerant, such as a FREON-type fluid.

The inert plastic housing containing the infuse 18 may be hermetically sealed, but need not be. The housing, if made of a moldable or easily shaped material, may include, for example, integrally formed needle stops 32, 34 for the primary and bolus injection sites, as well as one or more integrally formed suture loops 36 for the passage of anchor sutures through when the device is placed on the patient's body. An adhesion resistant material, such as silicone rubber or other suitable material, may be disposed within the loops 36 to prevent tissue growth into the loops.

Variable volume chamber 30 may be a substantially rigid, gas-impermeable bellows structure or other similar rigid-walled or spring-loaded structure that occupies a volume that approaches the volume of main reservoir 16 when expanded. In an illustrati6

ES 2 277 604 T3 is shown in Figures 3 and 4 the variable volume chamber 30 includes an accordion type bellows. It is to be appreciated that any suitable chamber may be employed to enclose the pressure source of the device. Preferred materials for the bellows chamber can include, but are not limited to, metals and plastics.

The operation of the infusion device can be affected by the width or diameter dimension D 'of the variable volume chamber relative to the diameter D of the housing. It may be desirable to make D 'less than D so that the walls of the bellows are spaced from the walls of the housing, but preferably only to such an extent that it will allow the walls of the bellows to move freely within the housing. The walls of the bellows may be located as close as possible to the walls of the housing so that a substantial displacement of the infusion can be achieved by effect of the movement of the bellows in the reservoir. However, it is desirable to avoid the drag resistance of the bellows walls on the walls of the housing. Thus, the variable volume chamber can be centered in the main reservoir to achieve increased volume and avoid drag resistance and so that the distance DD 'is sufficient to avoid such drag resistance.

Although the device and bellows are illustrated as being cylindrical in a preferred embodiment, they can be of any convenient shape.

The variable volume chamber may be positioned so that it does not obstruct the main inlet port 20 for infusion when the main reservoir is empty and the variable volume chamber is at its expanded volume. Along the refill fluid flow path 31, a fluid refill reservoir 29 may be provided to contain the infuse before it enters the interior region of the housing. Along the refill fluid flow path 31, a fluid dispersion flow path 33 may be provided in a coupling region 35 between the housing and the bellows to disperse the infuse into the interior region of the housing.

A spacer 27 may be provided in the housing, the bellows, or both, such that the refill fluid flow path is not obstructed by the movement of the bellows. The spacer can be any device or method apparent to one of ordinary skill in the art that serves to maintain the refill fluid flow path in a state unobstructed by the bellows, such as channels, grooves, or spacers. For example, in one embodiment the free bellows can be kept away from the infuse inlet port by means of spacers extending from the bellows or from said infuse inlet port.

To ensure the lowest possible profile for the device, it may be desirable to construct the housing so that the central portion 37 of one or both of its upper and lower portions, together with corresponding central portions or regions 39 of the upper and lower members of the bellows, is offset or depressed with respect to the nominal plane of the central portions, as shown in Figures 3 and 4, to form a structure of elements nested one in another. The infusion inlet port fits within a recessed central portion of the bellows.

As illustrated, the central portions or regions 37 and 39 of the upper and lower portions of the housing and / or the bellows may be surrounded by annular peripheral portions or regions 41,43. Although only the upper portions of the housing and the bellows are shown as being nested in one another in Figures 3 and 4, the lower portions of the housing and the bellows could also be nested in one another to further reduce the height of the device. Reductions in the volume of the infuse chamber 30 reduce the amount of infuse that can be delivered and increase the frequency with which the chamber 30 may need to be recharged if drug delivery is to take place over a prolonged period. However, the pressure source can be selected so that delivery is maximized from a given volume.

As illustrated in Figures 1 through 4, the device may include a separate bolus injection port 38 that includes a bolus inlet port 40 sealed with a self-sealing pierceable septum 42. Bolus inlet port 40 leads to a bolus reservoir 44 that is in fluid communication with fluid outlet flow path 25 and delivery catheter 24, albeit downstream of filter 26 and flow restrictor 28. The infuse introduced into the bolus port goes directly to the delivery catheter and avoids the controlled release provided by the action of the pressure source and the variable volume chamber over the infuse in the main reservoir.

Both the main infusion inlet port 20 and the bolus injection port 38 may include sensor devices known in the art that assist the patient and the medical team in positioning the devices transdermally so that additional infusion can be introduced into the device without the need for external palpation or surgical removal of the device.

The life of an implantable infusion device, such as those described herein, is largely determined by the life of the septum through which the infusion is introduced. The use of a self-sealing material, such as an elastomer, silicone rubber, or similar material, for the septum allows the septum to reseal after it has been pierced with a needle. However, even self-sealing materials lose some elasticity after a number of uses and may require replacement to ensure no infuse escapes from the device.

The life of the septum and thus the life of the infusion device can be optimized by careful selection of the septum material and the dimensions of the septum and the septum chamber in the device. This is shown in figure 5. The ratio of the dimension of the septum chamber opening (B) to the width of the septum chamber (A) is preferably such that the entire volume of the septum can fit within the chamber opening B when compressing the septum, and such that the width A of the chamber adequately compresses the septum to provide satisfactory pierce life. The selection of a material for the septum may also be a consideration, since its hardness, measured by a durometer, preferably allows a

ES 2 277 604 T3 adequate compression of the septum during insertion without understanding the piercing life. The height of the septum chamber (C) is preferably sufficient to allow the compressed septum to fill the chamber and still be sufficiently compressed in the axial direction to achieve the desired pierce life.

A septum replacement kit allows the surgeon to replace a worn septum without surgically removing the device from the patient. Such a kit is illustrated in Figures 6A-6C. Figure 6A shows a septum 22 that is typically in the shape of a cylindrical or square plug of height H and width W. The septum may be made of a compressible, elastic, penetrable, and self-sealing material, such as rubber or elastomer. Figure 6B shows the septum housed in a tubular member 46 that is dimensioned to fit the inlet port 20 (having the width B) of the infusion device 12. The septum is easily compressed sufficiently to house it within the tubular member 46 and a plunger 48 is used to dislodge the septum from the tubular member and into the septum chamber 50, which has a width A and a height C, then that it has been inserted into the inlet port 20, as shown in FIG. 6C. The septum is radially compressed in the chamber to form a penetrable gasket. The plunger and tubular member can then be removed.

Removal of a spent septum can be accomplished by inserting a sharp instrument into the septum to cut it into sections that can then be removed from the septum chamber with forceps or other suitable instrument.

Although Figures 6A-6C illustrate the use of the septum replacement kit to replace the primary septum 22, it should be understood that the kit can also be used to replace the bolus septum 42 at the bolus inlet port 40.

The device may include a safety fill device to ensure that the patient and medical team can distinguish between the primary inlet port and the bolus injection port to reduce the incidence of inadvertent administration of relatively large doses intended to be administered to the patient over time. When an implanted infusion pump is to be refilled, it can be difficult to determine whether a refilling needle is positioned to enter the main infusion port 20 or the bolus injection port 38. The entry of the refilling needle into the The wrong port for the dose being delivered can result in a patient receiving an excessive dose of the drug and therefore it is desirable to prevent this.

A bolus safety feature in accordance with an illustrative embodiment of the present invention is shown and described in connection with Figures 7A7B. Figure 7A illustrates the two infuse ports in a typical implantable infusion pump in accordance with the invention. The device includes a main or central access port 20 for delivering infuse to the device and a bolus access port 40 for delivering a bolus injection directly to the patient. Central access port 20 includes a single septum below which is disposed an infusion reservoir R. A refill needle having a hole in the tip is used to fill central access port 20, as shown.

In contrast, the lateral bolus access port 40 includes two septa that are spaced from each other to define an infusion reservoir R between them. The upper septum in bolus access port 40 secures the delivery needle in place and provides a seal to prevent bolus dose leakage once the needle is removed from the bolus port. The lower septum blocks the opening of the tip of a standard refill needle, as shown in Figure 20, if such a needle were inadvertently inserted into the bolus port. A special needle with a lateral access opening offset from the tip or located near the center of its length, as shown at 40, can be used to fill the bolus port, rather than at or near the tip. , as shown in 20.

Figure 7B shows the result of using a standard delivery needle at the bolus port. The standard supply needle includes an opening at its tip and does not have any opening on the side. The tip opening will be blocked by the lower septum when the needle is inserted into the bolus port, and no infusion will be delivered.

This design of the central port and bolus port in the device of the invention helps prevent inadvertent administration of a bolus dose to a patient due to the use of a bolus needle (with side access port) in the port. bolus port. If a standard delivery needle is accidentally inserted into the bolus port, no infusion can be delivered, and the surgeon can recognize that the wrong needle is being used, without administering any harmful doses to the patient.

However, it is to be appreciated that any safety features apparent to one skilled in the art can be employed to reduce the incidence of inadvertent delivery of a noxious infusion dose to the bolus reservoir.

Since certain changes may be made to the above apparatus without departing from the scope of the invention as defined in the claims, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings be construed in an illustrative sense and not limitative.