Dry powder inhaler

A dry powder inhaler (10) having a chamber (26) divided into first and second blister compartments (28, 30) for storing unused and used portions (34, 36) of a blister strip (12) is provided. A moveable dividing wall (32) separates the first and second blister compartments. One or more arcuate supporting surfaces (38, 40, 42) are disposed in either the first and/or the second blister compartments and these surfaces support the used or unused blister strip during successive actuations of the inhaler. Use of the arcuate supporting surfaces facilities compact coils of unused and used portions of blister strip, thereby reducing the size of the chamber required for the inhaler.

This application is a U.S. national phase application under 35 U.S.C. of § 371 of International Application No. PCT/EP2016/067208, filed Jul. 19, 2016, which claims priority of European Patent Application No. 15177556.6, filed Jul. 20, 2015, the disclosure of which is hereby incorporated by reference herein.

The present invention relates to an inhalation device for oral or nasal delivery of medicament in powdered form. More specifically, the invention relates to a dry powder inhaler in which powdered medicament is stored within a strip of blisters. The invention also relates to an inhaler containing a strip of blisters each having a puncturable lid and containing a dose of medicament for inhalation by a user of the device according to the invention.

Oral or nasal delivery of a medicament using an inhalation device is a particularly attractive method of drug administration as these devices are relatively easy for a patient to use discreetly and in public. As well as delivering medicament to treat local diseases of the airway and other respiratory problems, they have more recently also been used to deliver drugs to the bloodstream via the lungs, thereby avoiding the need for hypodermic injections.

It is common for dry powder formulations to be pre-packaged in individual doses, usually in the form of capsules or blisters which each contain a single dose of the powder which has been accurately and consistently measured. A blister is generally cold formed from a ductile foil laminate or a plastics material and includes a lid which is permanently or peelably sealed around the periphery of the blister during manufacture and after the dose has been introduced into the blister.

A foil blister is preferred over capsules as each dose is protected from the ingress of water and penetration of gases such as oxygen in addition to being shielded from light and UV radiation, all of which can have a detrimental effect on the delivery characteristics of the inhaler if a dose becomes exposed to them. Therefore, a blister offers excellent environmental protection to each individual drug dose.

Inhalation devices that receive a coiled blister strip comprising a number of blisters each of which contain a pre-metered and individually packaged dose of the drug to be delivered are well known. Actuation of the device causes a mechanism to breach or rupture a blister, such as by puncturing it or peeling the lid off, so that when the patient inhales, air is drawn through the blister entraining the dose therein that is then carried out of the blister through the device and via the patient's airway down into the lungs. Pressurized air or gas or other propellants may also be used to carry the dose out of the blister. Alternatively, the mechanism that punctures or opens the blister may push or eject the dose out of the blister into a receptacle from which the dose may subsequently be inhaled.

It is advantageous for the inhaler to be capable of holding a number of doses to enable it to be used repeatedly over a period of time without the requirement to open and/or insert a blister into the device each time it is used. Therefore, many conventional devices include means for storing a number of blisters each containing an individual dose of medicament. When a dose is to be inhaled, an indexing mechanism moves a previously emptied blister away from the opening mechanism so that a fresh one, a target blister, is moved into a position ready to be opened for inhalation of its contents. An inhaler of this type is known from the Applicant's own international patent application which published as WO2005/037353 A1.

The device known from WO2005/037353 A1 has already been modified so as provide a fully integrated device, i.e. one in which the used blisters are retained within its housing so that a user never has to come into direct contact with the blister strip.

In one modified embodiment, known from the Applicant's own previous application that has now been published as WO2009/007352 A1, there is provided a flexible and resilient spiral element mounted within the housing of the device into which the used portion of the blister strip is directed so that, as the strip is gradually used up, the spiral expands as more and more of the strip is fed or pushed into it between its coils.

Like the present invention, the device in WO2009/007352 A1 has a dividing wall to separate the interior of the housing into used and unused blister compartments. The dividing wall is rigid and slideably mounted so that the size of the unused and used blister compartments changes relative to each other as the number of blisters that are used increases and the number of unused blisters decreases. A moveable wall is also known from US 2010/0288278 (Valois S.A.S.).

WO09/007352 A1 also describes an embodiment in which used blisters are crushed between the blister strip drive or indexing wheel and the inner surface of the casing of the device, which is also a feature of the inhaler of the present invention. As crushing takes place, i.e. as the used strip passes around the blister strip drive member, a curl or curved form is imparted to the strip which helps it to coil up within the used blister compartment.

A full operation of the inhaler according to the present invention is described in WO2012/069854 A1. The indexing mechanism is specifically described in WO2009/092652 A1.

The disclosures of WO2005/037353 A1, WO09/007352 A1, WO2009/092652 A1 and WO2012/069854 A1 are all incorporated herein by reference.

The present invention seeks to provide an inhalation device that retains a used blister strip within the housing of the device, whilst optimising the internal configuration in order to enhance the compactness of the device.

According to a first aspect of the invention, there is provided an inhaler comprisinga housing,a mouthpiece,a blister strip having a plurality of blisters, each blister containing, at least initially, a dose of medicament for inhalation by a user via the mouthpiece,a blister opening assembly for facilitating withdrawal of medicament from a target blister of the blister strip,an actuator mechanism operable to sequentially move each blister into alignment with the blister opening assembly so as to become said target blister,the housing comprising a first blister compartment for storing an unopened portion of the blister strip as a first coil, a second blister compartment for receiving an opened portion of the blister strip and coiling it into a second coil, and a movable dividing wall separating the first and second blister compartments,the movable dividing wall being displaced progressively during successive actuations of the inhaler, thereby causing the volume of the first blister compartment to decrease progressively and the volume of the second blister compartment to increase progressively,the inhaler further comprising an arcuate supporting surface within the housing for supporting at least a portion of the first or second coils.

Optionally, a radius of the arcuate supporting surface matches the radius of the first coil, at a stage in the life of the inhaler, when the diameter of the first coil is at a maximum.

Optionally, a radius of the arcuate supporting surface matches the radius of the first coil, at a stage in the life of the inhaler, when the sum diameter of the first and second coils is at a maximum.

Optionally, a radius of the arcuate supporting surface matches the radius of the second coil, at a stage in the life of the inhaler, when the diameter of the first coil is at or near a maximum.

The arcuate supporting surface may be disposed in, or form part of, the first blister compartment.

The arcuate supporting surface may be disposed in, or form part of, the second blister compartment.

Preferably, the arcuate supporting surface extends from an internal surface of the housing. Alternatively, the arcuate supporting surface may extend from an internal wall within the housing.

Preferably, the arcuate supporting surface has a length equivalent to an arc of the first coil of at least 30 degrees when the diameter of the first coil is at a maximum.

Preferably, the position of the arcuate supporting surface relative to the housing is fixed such that it is immoveable.

The first coil may be disposed intermediate the arcuate supporting surface and the moveable dividing wall. Alternatively, the second coil may be disposed intermediate the arcuate supporting surface and the moveable dividing wall.

Preferably, the inhaler further comprises a blister strip guide rib for controlling the direction of the used blister strip as it enters the second blister compartment, the used blister strip passing between the guide rib and an internal surface of the housing during successive actuations of the inhaler. Ideally, the blister strip has a height a and the guide rib is spaced apart from the internal surface of the housing by distance b, wherein distance b is less than height a.

Optionally, the inhaler further comprises a blister crushing member for at least partially squashing the blisters after they have been opened.

Preferably, the arcuate supporting surface has a thickness of up to 1 mm. Preferably, the arcuate supporting surface is spaced apart from the moveable dividing wall.

Preferably, the arcuate supporting surface is inflexible or rigid.

Optionally, the movable dividing wall may be configured to facilitate the formation of the second coil as the used portion of the blister strip enters the second blister compartment.

Preferably, the blister strip carries between 30 and 60 blisters.

Preferably, each blister has a dose payload of up to 100 mg, preferably up to 50 mg, and more preferably between 10 and 25 mg.

According to a second aspect of the invention there is provided an inhaler, comprisinga housing,a mouthpiece,a blister strip having a plurality of blisters, each blister containing, at least initially, a dose of medicament for inhalation by a user via the mouthpiece,a blister opening assembly for facilitating withdrawal of medicament from a target blister of the blister strip,an actuator mechanism operable to sequentially move each blister into alignment with the blister opening assembly so as to become said target blister,the housing comprising a first blister compartment for storing an unopened portion of the blister strip as a first coil, a second blister compartment for receiving an opened portion of the blister strip and coiling it into a second coil, and a movable dividing wall separating the first and second blister compartments,the movable dividing wall being displaced progressively during successive actuations of the inhaler, thereby causing the volume of the first blister compartment to decrease progressively and the volume of the second blister compartment to increase progressively,the inhaler further comprising an arcuate supporting surface within the housing for supporting at least a portion of the first coil,characterised in that a radius of the arcuate supporting surface matches the radius of the first coil, at a stage in the life of the inhaler, when the diameter of the first coil is at a maximum.

According to a third aspect of the invention, there is provided an inhaler, comprisinga housing,a mouthpiece,a blister strip having a plurality of blisters, each blister containing, at least initially, a dose of medicament for inhalation by a user via the mouthpiece,a blister opening assembly for facilitating withdrawal of medicament from a target blister of the blister strip,an actuator mechanism operable to sequentially move each blister into alignment with the blister opening assembly so as to become said target blister,the housing comprising a first blister compartment for storing an unopened portion of the blister strip as a first coil, a second blister compartment for receiving an opened portion of the blister strip and coiling it into a second coil, and a movable dividing wall separating the first and second blister compartments,the movable dividing wall being displaced progressively during successive actuations of the inhaler, thereby causing the volume of the first blister compartment to decrease progressively and the volume of the second blister compartment to increase progressively,the inhaler further comprising an arcuate supporting surface within the housing for supporting at least a portion of the first coil,characterised in that a radius of the arcuate supporting surface matches the radius of the first coil, at a stage in the life of the inhaler, when the sum diameter of the first and second coils is at a maximum.

According to a fourth aspect of the invention, there is provided an inhaler, comprisinga housing,a mouthpiece,a blister strip having a plurality of blisters, each blister containing, at least initially, a dose of medicament for inhalation by a user via the mouthpiece,a blister opening assembly for facilitating withdrawal of medicament from a target blister of the blister strip,an actuator mechanism operable to sequentially move each blister into alignment with the blister opening assembly so as to become said target blister,the housing comprising a first blister compartment for storing an unopened portion of the blister strip as a first coil, a second blister compartment for receiving an opened portion of the blister strip and coiling it into a second coil, and a movable dividing wall separating the first and second blister compartments,the movable dividing wall being displaced progressively during successive actuations of the inhaler, thereby causing the volume of the first blister compartment to decrease progressively and the volume of the second blister compartment to increase progressively,the inhaler further comprising an arcuate supporting surface within the housing for supporting at least a portion of the second coil,characterised in that a radius of the arcuate supporting surface matches the radius of the second coil, at a stage in the life of the inhaler, when the diameter of the first coil is at or near a maximum.

This coincides with a stage in the life of the inhaler when the diameter of the second coil is at a minimum.

According to a fifth aspect of the invention, there is provided an inhaler, comprising a housing, a mouthpiece extending from or mounted to the housing, a blister strip having a plurality of blisters, each blister containing, at least initially, a dose of medicament for inhalation by a user via the mouthpiece, a blister opening assembly for facilitating withdrawal of medicament from a target blister of the blister strip, an actuator mechanism operable to sequentially move each blister into alignment with the blister opening assembly so as to become said target blister, the housing comprising a first blister compartment for storing an unopened portion of the blister strip as a first coil, a second blister compartment for receiving an opened portion of the blister strip and coiling it into a second coil, and a movable dividing wall separating the first and second blister compartments, the movable dividing wall being displaced progressively during successive actuations of the inhaler, thereby causing the volume of the first blister compartment to decrease progressively and the volume of the second blister compartment to increase progressively, the inhaler further comprising an arcuate supporting surface in the first blister compartment for supporting at least a portion of the first coil, a second said arcuate supporting surface in the first blister compartment for supporting a further portion of the first coil and a third said arcuate supporting surface in the second blister compartment for supporting a portion of the second coil.

Preferably, the inhaler further comprises a blister strip guide rib for controlling the direction of the used blister strip as it enters the second blister compartment, the used blister strip passing between the guide rib and an internal surface of the housing during successive actuations of the inhaler. Ideally, the blister strip has a height a and the guide rib is spaced apart from the internal surface of the housing by distance b, wherein distance b is less than height a.

Referring toFIGS. 1 and 2of the accompanying drawings, there is shown a dry powder inhaler10for dispensing powdered medicament from a blister strip12. The inhaler10comprises a housing14formed from two shell portions14a,14ba cap16pivotally mounted to the housing14for rotation about a first axis of rotation A, a mouthpiece18pivotally mounted to the housing14about a second axis of rotation B, a blister piercing member20depending from the mouthpiece18for piercing the blister strip12, an indexing system for advancing the blister strip12past the blister piercing member20and an actuating lever22operable to cause both indexing and piercing of the blister strip12.

The cap16is moveable, from a closed position in which the cap16covers and protects the mouthpiece18, to a fully open position, and in a direction indicated by arrow “R” inFIG. 2(a), in which the mouthpiece18is exposed to enable a user to inhale a dose of medicament through the mouthpiece18from the blister strip12.

The cap16is rotated into its fully open position in the direction of arrow “R”. The actuating lever22is revealed as soon as the cap16is rotated out of its closed position. The user then applies pressure to the actuating lever22, so that it rotates in the direction indicated by arrow “S” inFIG. 2(b).

During initial rotation of the actuating lever22through a first portion of its stroke into the position as it is shown inFIG. 2(b), the blister strip12is indexed so as to move an unused blister into alignment with the blister piercing member20.

When the actuating lever22is rotated through a second portion of its stroke beyond the position shown inFIG. 2(b)and after having completed the first portion of its stroke, in the direction of arrow “T” inFIG. 2(c), the blister strip12remains stationary but the mouthpiece18is now pivoted so that the blister piercing member20pierces the lid of the previously aligned blister.

Once the actuating lever22is in the position shown inFIG. 2(c), the user now inhales through the mouthpiece18, as shown by arrows indicated by “U” inFIG. 2(d).

After inhalation, the user rotates the cap16in the opposite direction, i.e. in the direction indicated by “V” inFIG. 2(e). During this movement, the cap16engages with the actuating lever22so that the actuating lever22also returns to its initial position as shown inFIG. 2(a), the blister strip remaining stationary during this return movement of the actuating lever22.

It should be noted that the cap16is ‘passive’ in the sense that it can be opened and closed freely without performing the function of indexing of the blister strip12or causing a blister piercing member20depending from the mouthpiece18to pierce the lid of an aligned blister. However, although the cap16is passive, it does perform the function of re-setting the actuating lever back to its original position in the event that the actuating lever22is depressed prior to closing the cap16.

The cap16and actuating lever22are configured so that, when the cap16is in its closed position and the actuating lever22has returned to its initial position, the cap16overlies the actuating lever22which is pressed by a user to operate the device. This prevents a user from attempting to operate the device by rotating the actuating lever22prior to opening the cap16.

As previously mentioned, the inhaler10has an indexing mechanism that has previously been described in WO2009/092652 A1 and a thus further detailed description will be omitted here.

The indexing mechanism comprises a blister strip drive member or indexing wheel24, around which the used blister strip travels, and which drives the blister strip12onwards. The indexing wheel24may also be used to squeeze the used blister cavities as they pass around it, thereby at least partially crushing them. This is achieved by enlarging the axle or hub of the indexing wheel24so that the distance between the hub and the casing or wall of the inhaler10, or a component fixed to the casing, is less than the maximum height of a blister cavity. As the blister cavities are entrained between spokes of the indexing wheel24, onward rotation of the indexing wheel24causes the cavities to be at least partially squashed or sandwiched between the enlarged hub of the indexing wheel24and the casing of the inhaler10. The advantage of at least partially crushing the empty blister cavities is that they then take up less space when coiled within the used blister compartment of the device as the coiled strip has a smaller radius. Furthermore, a natural curvature is imparted to the strip, both as a result of being fed around the indexing wheel24and also as a result of the crushing of the blister cavities. This encourages the used portion of the blister strip12to coil more readily. It is also apparent that, when the blister cavities have been crushed, the cavity is more resilient to denting at the point at which the spoke of the indexing wheel24contacts the strip, i.e. at the root where the blister cavity meets the remainder of the blister strip12. Therefore, a more positive and precise drive of the blister strip12is achieved when the blisters have been crushed.

Within the housing14, a chamber26is separated into first and second compartments28,30by a rigid dividing wall32. The unused portion of blister strip12is stored within the first blister compartment28as a first coil34and the used portion of blister strip12is received into the second blister compartment30to form a second coil36. The dividing wall32is slideably mounted within the chamber26so that, as more of the blisters are used, the force of the used coil36of blisters in the second blister compartment30presses against the dividing wall32and pushes it so as to enlarge the space for the used blisters and reduce the space previously occupied by the unused blisters.

It is here where the invention lies. The configuration of the interior of the housing14has been optimised to minimise the space required for the first and second blister compartments28,30, thereby reducing the overall size of the inhaler10.

The inhaler10comprises three arcuate supporting surfaces38,40,42within the housing14for supporting at least a portion of the first coil34, of the second coil36, or both the first and second coils34,36during successive actuations of the inhaler10. In this embodiment, three distinct arcuate supporting surfaces38,40,42are provided, but any one or two combinations of the arcuate supporting surfaces38,40,42could feasibly be used. It is only when all three arcuate supporting surfaces38,40,42are used that the configuration is optimised. With only one or two arcuate supporting surfaces38,40,42, the configuration is improved so that less space is required for the unused and used portions of blister strip12, but it is not an optimum configuration, which is preferable.

FIG. 3shows the coil34of unused blister strip12after one or two actuations have taken place but before the second coil36has begun to form in the second blister compartment30. The diameter of the first coil34is just less than its maximum.

FIG. 4indicates the coil34of unused blister strip12at or near its maximum diameter but with enough used blister strip in the second blister compartment30to form the second coil36. InFIG. 4, a first arcuate supporting surface38is seen to support the theoretical outermost spiral of the first coil34. The first arcuate supporting surface38forms part of the first blister compartment28. The first arcuate supporting surface38extends from an internal wall of the inhaler10, proximate to the indexing wheel24.

In this position, the first arcuate supporting surface38supports the first coil34in a substantially central position within the inhaler10, urging the moveable dividing wall32to the right hand side of the inhaler10as viewed inFIG. 4. The first arcuate supporting surface38has a length equivalent to an arc of the first coil34of at least 30 degrees when the diameter of the first coil34is at a maximum. This length of arcuate supporting surface provides sufficient support for the first coil34to hold it in place initially but without unnecessarily increasing the complexity of the design of the inhaler10.

A second arcuate supporting surface40supports the second coil36. The second arcuate supporting surface40forms part of the second blister compartment30. The second arcuate supporting surface40is situated in the vicinity of the exit region of the indexing wheel24. The length of the second arcuate supporting surface40is equivalent to an arc of the second coil36of at least 30 degrees when the diameter of the first coil34is at a maximum.

Thus, the configuration of the first and second blister compartments28,30is specific to the stage in the life of the inhaler10when the diameter of the first coil34is at or near a maximum. It is also at this time, that the diameter of the second coil36is at a minimum. At this stage, the radius of the first arcuate supporting surface38matches the radius of the first coil34. Also, the radius of the second arcuate supporting surface40matches the radius of the second coil36.

Turning now toFIG. 5, a third arcuate supporting surface42extends inwardly from an internal surface of the inhaler10. The third arcuate supporting surface42forms part of the first blister compartment28. The third arcuate supporting surface42is situated in the vicinity of the entry region of the indexing wheel24. Again, the length of the third arcuate supporting surface42is equivalent to an arc of the first coil34of at least 30 degrees when the diameter of the first coil34is at a maximum.

InFIG. 5, the configuration of the first and second blister compartments28,30is specific to the stage in the life of the inhaler10when the combined diameter of the first and second coils34,36is at a maximum. At this stage, the radius of the third arcuate supporting surface42matches the radius of the first coil34.

InFIG. 6, all or almost all of the doses from the blister strip12have been dispensed from the inhaler10. The configuration of the first and second blister compartments28,30is specific to the stage in the life of the inhaler10when the diameter of the second coil36is at a maximum. This coincides with same stage as when the diameter of the first coil34is at or near a minimum.

With reference toFIG. 7, the diameter of the first coil is indicated at curve44, the diameter of the second coil at curve46, and the sum of these two diameters, i.e. the sum diameter of the first and second coils is indicated at curve48.

At the beginning of the life of the inhaler10when few or no doses have been dispensed, and also up to substantially mid-way through the life of the inhaler, it is very important for the space within the first and second blister compartments28,30to be tightly controlled or allocated so as to minimise the internal volume required subsequently for the first and second coils34,36. If this did not happen, the curve48indicating the sum diameter of the first and second coils34,36would shift upwardly and would begin at a much higher point on the graph. Consequently, the space required for the first and second coils34,36when their combined diameters are at a maximum, i.e. the peak of the sum of diameters curve48occurring approximately mid-way through the life of the inhaler10, would be higher. In brief, it is imperative that the combined diameter of the first and second coils is as small as possible at the start of the useful life of the inhaler.

At or towards the end of the life of the inhaler10, the role of the arcuate supporting surfaces38,40,42becomes increasingly insignificant because there is less need now for the used blister strip to be coiled up tightly. In practice, the second coil36simply expands to fill most, if not all, of the space available within the second blister compartment30.

When blister crushing is incorporated into the inhaler10, as explained earlier, this reduces the sum diameter of the first and second coils34,36generally throughout the life of the inhaler10, as indicated inFIG. 8. In particular, the space required for the first and second coils34,36when the combined diameter of the first and second coils34,36is at a peak, is reduced compared to when no blister crushing is used.

Blister crushing does not affect the diameter of the first coil34since blister crushing takes place after blister piercing and dose inhalation has occurred. It does affect the diameter of the coiling used blister strip, and facilitates a tighter second coil36. Therefore, the sum diameter of the first and second coils34,36is less than when no blister crushing occurs.

It is clear from bothFIGS. 7 and 8that it is important to constrain the first and second coils34,36as much as possible in the early stages of the life of the inhaler10in order to minimise the sum diameter of the first and second coils34,36. This, in turn, minimises the amount of space required when the sum diameter of the first and second coils34,36is at its peak (or maximum). This is achieved by employing one or more the arcuate supporting surfaces38,40,42described above.

None of the aforementioned arcuate supporting surfaces38,40,42form part of the moveable dividing wall32. For a period of time, the first arcuate supporting surface38is near to the moveable dividing wall32, as the moveable dividing wall32travels across the breadth of the inhaler10from right to left as viewed when looking atFIGS. 4, 5 and 6. The second arcuate supporting surface40is separated from the moveable dividing wall32by the second coil36. The third arcuate supporting surface42is separated from the moveable dividing wall32by the first coil34.

In this embodiment of the invention, the moveable dividing wall32comprises an elongate foot50which is attached to and integrally formed with a baffle52that divides the chamber26within the inhaler10into the first and second blister compartments28,30. An approximate central region of the foot50is attached to the baffle52so that it extends in opposite directions on either side of the baffle52. The foot50is slideably received in a recess54formed in a wall of the housing14and is wider at its ends than in its centre where it joins the baffle52so that contact with the walls of the recess50is primarily made with the wider ends of the foot50.

The baffle52itself is generally ‘J’ shaped, with a linear body portion56and an arcuate tail portion58extending from a lower end of the linear body portion56. The arcuate tail portion58is curved to encourage the incoming used blister strip within the second compartment30to curl tightly into the second coil36. The smaller the radius of the arcuate tail portion58, the tighter the second coil36becomes. The advantage of this is that the resulting second coil36is smaller when at its greatest radius than it would be otherwise.

Turning now toFIG. 9, a blister strip guide rib60is positioned in the second blister compartment30. The blister strip guide rib60controls the direction of the used blister strip as it enters the second blister compartment30. A gap or channel exists between the blister strip guide rib60and the housing14to allow the used blister strip to pass therethrough during successive actuations of the inhaler10. The size of the gap is important. If the blister strip12has a height a and the blister strip guide rib60is spaced apart from an internal surface of the housing14by a distance b, distance b must be less than height a.

The thickness of the blister strip guide rib60is critical. Too thin and the blister strip guide rib60is problematic during manufacturing. Too thick and the used blister strip will not coil tightly; instead the used blister strip will form an elongate (as opposed to rounded) loop that pushes away from the blister strip guide rib60towards the centre of the chamber26, before eventually beginning to coil. The resulting diameter of the second coil36would therefore be a lot greater than it would be otherwise, thereby increasing the combined diameter of the first and second coils34,36, and consequently increasing the internal volume required for the used and unused blister strip12. When the thickness of the rib is at an optimum value, as the used blister strip begins to coil, it will coil back on itself, and engage the incoming used blister strip. The force acting on the incoming blister strip to move it forward is consequently augmented by the force acting on the free end of the blister strip12. The inventors have found the optimum thickness of the blister strip guide rib60to be up to 1 mm.

In terms of impact on the overall internal volume required, the blister strip guide rib60has been found to be more influential than the three aforementioned arcuate supporting surfaces38,40,42. The third arcuate supporting surface42is then most influential, followed by the first arcuate supporting surface38and finally the second arcuate supporting surface40.

If no blister crushing were to be incorporated into the inhaler10, the device would still benefit from one or more of the three arcuate supporting surfaces38,40,42and/or the blister strip guide rib60. However, the overall space required for the used and unused blister strip12when the combined diameter of the coiled used and unused blister strip12is at a maximum, would be higher.

With higher dose payload blisters, optimisation of the internal space required can still occur but again the peak sum diameter of the coiled used and unused blister strip12would be higher than it would be otherwise.

Optimisation would work for a 60 (sixty) dose inhaler10as well as a 30 (thirty) dose inhaler10. With a 30 dose inhaler10, the entire device could in theory be made proportionally smaller. However, in reality, since the cost of tooling has already been paid for once for the 60 dose configuration and a 30 dose inhaler10would use common components, it would be economically prudent to use the existing tooling. Furthermore, the question of optimising the internal space required for a 30 dose inhaler10would be rather moot simply because there would be plenty of space already available.

Many modifications and variations of the invention falling within the terms of the following claims will be apparent to those skilled in the art and the foregoing description should be regarded as a description of the preferred embodiments of the invention only. For example, although reference is made to a “mouthpiece”, the invention is also applicable to devices in which the dose is inhaled through the nasal passages. Therefore, for the purposes of this specification, the term “mouthpiece” should also be construed so as to include within its scope a tube which is inserted into the nasal passages of a patient for inhalation therethrough.

Furthermore, although the blister piercing member is described as being attached to the mouthpiece so that the mouthpiece and the blister piercing member move together, it is also envisaged that the mouthpiece itself could remain stationary and the blister piercing element could be pivotally mounted to the mouthpiece so that the blister piercing member rotates relative to the mouthpiece to pierce the lid of an aligned blister.

In another embodiment, the cap and the actuating member could be combined into a single component so that rotation of the cap also causes indexing of the strip and piercing of an aligned blister.

It will be appreciated that the inhaler of the invention may be either a passive or active device. In a passive device, the dose is entrained in a flow of air caused when the user inhales through the mouthpiece. However, in an active device, the inhaler would include means for generating a pressurised flow of gas or air through the blister to entrain the dose and carry it out of the blister through the mouthpiece and into the user's airway. In one embodiment, the inhaler may be provided with a source of pressurised gas or air within the housing.

Reference is made throughout this specification to both “unused” and “used” blisters. It will be appreciated that “unused” blisters refer to those blisters that have not passed the blister piercing member and which remain intact with the dose contained therein. “Used” blisters refer to those blisters which have passed the blister piercing member in response to movement of the actuator by a user and which have been pierced to enable access to the dose contained therein to be obtained. Although in general, a “used” blister refers to a blister from which a dose has been inhaled, it should also be taken to include blisters which have passed the blister piercing member and have been pierced but which still contain either some or all of the dose contained therein. This may happen, for example, when a user moves the actuator to move the blister strip without inhaling the dose from a previously pierced blister.