GB2391858A

GB2391858A - Counter for an inhaler

Info

Publication number: GB2391858A
Application number: GB0312932A
Authority: GB
Inventors: Jeffrey Kenneth Allen
Original assignee: Trumeter Co Ltd
Current assignee: Trumeter Co Ltd
Priority date: 2002-06-05
Filing date: 2003-06-05
Publication date: 2004-02-18
Anticipated expiration: 2023-06-05
Also published as: GB0212896D0; AU2003241035A1; WO2003103759A1; GB0312932D0; GB2391858B

Abstract

An attachment 20 for inhaler canisters 10 has an integrated circuit including an electronic counter triggered by a switch 22 which is actuated when the nozzle 14 of the inhaler canister has been depressed to the extent necessary to dispense a dose. The counting device preferably maintains an accurate record of the number of doses delivered from the inhaler canister and is preferably retained with the canister when the canister is removed from the inhaler body 54, for example for cleaning. The counter may provide a warning when a predetermined number of doses have been dispensed from the canister and preferably the attachment does not radially protrude beyond the side wall of the canister allowing the attachment to be mounted in known inhaler housings.

Description

239 1 858

COUNTER

The present invention relates to a counting device capable of recording the number of doses dispensed from 5 inhalers and particularly, but. not. exclusively from Pressurised Metered Dose Inhalers (PMDIs).

Inhalers are commonly used to administer medication such as bronchodilators, corticosteroids and anti-

allergenics to the pulmonary tracts of humans and other lo animals, and in particular to treat nasal and bronchial complaints such as asthma.

A typical inhaler includes a casing or body and a canister containing the drug. The canister may be an integral part of the inhaler, but more commonly is removable, so that the actuator may be cleaned. In most applications, the canister contains the drug in powder or liquid form, and the dispensing action forces out a regulated dose of the drug in aerosol form.

The aerosol may be created using a propellant e.g. 20 CFC or HFA forced through the drug by the dispensing motion, or more preferably in PMDIs by creation of a significant overpressure inside the canister.

In most PMDIs, the dispensing action consists of moving the canister relative to the casing, the action of

the casing on the nozzle of the canister causing the predetermined dose to be released when the nozzle has been depressed a set distance.

Typical canisters for use In PMDIs contain between 5 60 and 200 doses, and may be administered on a regular (e.g. daily) basis, or only occasionally to relieve particular symptoms. Even in the former case, the patient is unlikely to keep a record of the doses administered, so will not be aware when the canister no lo longer contains any drug. The patient will not necessarily be immediately aware that the drug IS no longer being dispensed as the pressure of the canister, or the dispensing motion, will appear unaltered. In an extreme situation, this could result in a patient needing 5 a dose in an emergency finding that their inhaler had in fact been exhausted in earlier use.

Therefore, there is a need for some form of counting device which can count the number of doses dispensed from a canister and so provide an indication of when the 20 canister is empty. In order to be of use, such a counting device must accurately record each actuation of the canister.

Previous attempts to provide such a counting device have had a number of drawbacks. In particular, some

solutions have been proposed with a counting device which is mounted on the casing of the inhaler and records each actuation of the canister using, for example, a pressure pad or a lever based switch. These devices suffer from 5 the problem that they either have to be reset manually, or if a canister is removed from the inhaler, the counter automatically resets, so if the same canister is replaced (e.g. after cleaning), the reading will be incorrect.

To overcome this problem, other solutions have JO proposed a counter mounted on the "top" end of the canister (the opposite end from the dispensing nozzle and normally the part which the user presses to use the inhaler), and includes a pressure-activated switch which increments the counter.

5 These latter devices do not provide particularly accurate indications of the number of doses dispensed from or remaining in the canister. This is because the pressure required to close the pressure switch is rarely exactly the same as that required to operate the inhaler 20 to dispense the drug. In particular the pressure required to move the nozzle the set distance for dispensing the drug may vary considerably, both from canister to canister and indeed during the life of each canister as the pressure inside the canister changes.

Therefore, there Is significant potential for either under- or overcounting the doses actually delivered, which can result in patients believing that the inhaler is still dispensing the drug when it has in fact run out, or in canisters which still contain several doses of the drug being disposed of because they are indicated as being exhausted.

Accordingly, at its broadest, the present invention provides an attachment for an inhaler canister, 0 containing a counter which is actuated when the nozzle of the inhaler canister has been depressed to the extent necessary to dispense a dose.

Therefore, the present invention preferably provides a counting device which maintains an accurate record of 5 the number of doses delivered from a canister, and which: is retained with that canister when the canister is removed from the inhaler.

One aspect of the present invention provides an attachment for the nozzle end of an inhaler canister, 20 including: a counter, display means connected to the counter and a switch wherein, in use, the switch triggers -

the counter when the canister has travailed far enough to dispense a dose of the drug contained in the canister.

The counter may be mechanical, but IS preferably electronic, forming part of an electrical circuit with the switch, the display means and/or a battery. The counter may be contained in an integrated clrcult.

5 When attached to the canister, the attachment may not radially protrude more than lmm beyond the side wall of the canister. Preferably, it does not protrude more than 0.5mm beyond the side wall. Most preferably, it does not radially protrude beyond the side wall of the lo canister at all. Having a small or no protrusion beyond the side wall of the canister means that the attachment of the invention can be mounted in known inhaler housings. Preferably, the attachment includes at least one arm 5 for engaging a groove in the side of the canister, the arrangement being such that, when attached to the canister, the at least one arm does not radially protrude more than lmm beyond the side wall of the canister.

Preferably, it does not protrude more than 0.5mm beyond 20 the side wall. Most preferably, it does not radially protrude beyond the side wall of the canister at all.

Preferably, the cross-sectional area of the attachment is never more than 1.1 x A, where is the cross-sectional area of the canister. Preferably, it is

never more than 1.025 x p. Thus, the cross-sectional area of the attachment taken normal to the axis of the attachment does not exceed 1.1 x (preferably 1.025 x p) at any point along the axis.

5 Preferably, the electronic components in the attachment are all located In a region having an area less than the cross-sectional area of the canister.

Preferably, the electronic components do not radially protrude from the side wall of the canister, i.e. the JO region is located directly below the nozzle end of the canister. Preferably, the electronic components are all located in a region of the attachment having a longitudinal length of less than 15mm. Preferably, the 5 length is less than 12mm. Most preferably it is less than 10.5mm. When attached to the canister, the attachment preferably extends less than 15mm below the bottom of the canister. Preferably, it extends less than 12mm. Most 20 preferably it extends less than 10.5mm.

Preferably, the maximum diameter of the attachment is no more than 32mm. More preferably, it is no more than 23mm.

Preferably, the maximum longitudinal length of the attachment is 50mm. More preferably, it is no more than 30mm. Most preferably, lt- is no more than 20mm.

The counter may be arranged to count upwards or 5 downwards, and may have respectively a fixed upper limit or a fixed starting number. Alternatively, the attachment may allow the upper limit or the starting number to be set for each canister.

Preferably the display means provides at least a lo warning when a number of doses equal to the upper limit or the starting number have been dispensed. Alternative warning means may also be used.

Particular examples of the display means are a mechanical display, a clock, and/or a liquid crystal display (LCD) any or all of which may display the number of doses dispensed and/or remaining, and may display other information as well, and/or light emitting diodes (LEDs), which may according to the patterns displayed, indicate one or more states of the canister (e.g. full, 20 in use, nearly empty and/or empty).

In one embodiment, before the counter reaches a first predetermined level, a first LED is lit permanently or flashes in a first predetermined pattern, and when the counter reaches the first predetermined level, that first

LED flashes in a second predetermined pattern. Then, when the counter reaches a second predetermined level, a second LED Is lit or flashes In a predetermined pattern.

The display means may include a green LED as the first 5 LED and a red LED as the second LED. Thus, in normal use, the green LED may be lit permanently. When the number of doses remaining in the canister reaches a first level (for example 10 doses remaining), the green LED may flash continuously. When there are no more doses JO remaining in the canister, the green LED is no longer lit and the red LED may be lit permanently. In this way, the user can be given some warning that the canister is about to run out, and so be able to obtain a replacement before it becomes necessary.

Is In a different embodiment, the display means includes at least two and preferably three LEDs.

Preferably the display means includes control means for operating one or more of the LEDs for a predetermined time interval at a predetermined point in the operation 20 of the device. for example, the LED(s) may activate for a predetermined time e.g. lo, 15 or 20 seconds immediately after the canister has been activated or a dose dispensed. In one example, a green LED would flash when the canister was operating normally, an amber LED

would instead operate or flash when a set level is reached (e.g. the canister Is becoming nearly empty) and a red LED would operate or flash when the canister is empty. The operation of the LEDs for a suitable time 5 after a dose is dispensed from the canister has the advantages of conserving battery life and also serving as an indication that a dose has been dispensed.

Preferably, all of the components of the counter, switch and display means are sealed within a body of the lo attachment, and that body is waterproof. This allows the canister and attachment to be removed from the inhaler and both parts cleaned without any risk of damaging those components with water or damp. In one embodiment the body of the attachment is made from silicone rubber.

15 When electronic components are used, various orientations and locations of the circuitry within the body of the attachment are envisaged. Preferably some of the electronics are mounted on a printed circuit board, and more preferably that circuit board is made from a 20 flexible substrate which allows that circuit board to be fitted into the best location in the attachment.

In an alternative embodiment, the electronic components (including an integrated circuit containing the counter) are mounted on one or more metal frames.

These frames may also form part of the switch, such as one of the contacts of the switch. The or each frame may connect one or more of the electronic components to each other, or to the power source (e.g. a battery).

5 The switch of the present: invention may be mounted on the side of the attachment, in which case it may include a button which is displaced radially (relative to the canister) when it encounters an obstruction on the body of the inhaler whilst being moved in a longitudinal lo direction. Such an obstruction is preferably formed as part of the inhaler body, and located such that the button is depressed when the canister and attachment have moved a sufficient distance to depress the nozzle of the canister and dispense a dose.] ib Alternatively, the switch can include a button which is mounted on the base of the body, and is depressed by contact with the inhaler body, or with an upward projection from the inhaler body, when the attachment has moved a sufficient distance to depress the nozzle of the so canister and dispense a dose.

In all alternative mountings of the switch, it is preferable that the switch is moulded at the same time as the body is formed. In a preferred embodiment of this, the switch includes two electrical contacts and a

substantially circular button with a head portion, the button being connected to the body of the attachment by a skirt, wherein both the head portion and the skirt are made from resl]ient material, and the button has a 5 projection extending radially inwards from the head portion, wherein the face of the projection opposite the head portion is made from, or has on it, conducting material, such that when the button is subjected to a longitudinal force on the head portion, the button lo deforms urging the conducting face of the projection into contact with both of the contacts, thereby completing an electrical circuit.

Further aspects of the present invention provide a canister with an attachment according to this invention, 15 and an inhaler incorporating such a canister.

The canister and inhaler may be any of the usual types used in these devices.

Preferably an inhaler according to the present invention includes a body portion, and that body portion 20 is adapted so as to allow the display means of the attachment to be visible at least some of the time.

Preferably the body of an inhaler according to the present invention contains a projection which is designed to interface with the switch of the attachment, so that

the switch IS activated when the nozzle of the canister has been depressed Particular embodiments of the present invention will now be described in relation to the attached drawings, in 5 which: Figure 1 shows an inhaler canister and an attachment according to the present invention; Figure 2 shows the inhaler canister and attachment according to the present invention mounted in an inhaler; lo Figure 3 is an exploded view of Figure 3; Figure 4 shows a cut-away view inside an attachment according to the present invention; Figure 5 shows a cut-away view inside another attachment according to the present invention showing an 15 alternative circuit board position; Figure 6 shows a cut-away top view of an attachment according to the present invention; Figure 7 shows an attachment according to the present invention which utilises LEDs; 20 Figure 8 shows an alternative embodiment of the present invention wherein the switch is mounted on the base of the attachment; Figure 9 shows an inhaler body which may be used with the embodiment of Figure 8;

Figures 10 and 11 show an alternative embodiment of the present invention with a different mounting of the electronic components; Figures 12a to 12c show alternative designs by which 5 an attachment according to the present invention can be attached to an inhaler canister; Figures 13a to 13c show alternative mechanisms by which an attachment according to the present invention can be secured to an inhaler canister; 10 Figures 14a and 14b show a further embodiment of an attachment according to the present invention; Figure 15 shows the attachment of Figure 14 attached to an inhaler canister; and Figure 16 shows a cross-section of a button suitable 15 for use as part of the switch of the present invention.

In Figure 1, an attachment 20 is shown about to be attached to an inhaler canister 10. The attachment includes a body 26, from which arms 24 extend. The arms 24 will engage with the ridges 16 on the body of the 20 inhaler canister. The attachment has an aperture 32 through which the nozzle 14 of the canister 10 can pass, so the dispensing action of the canister is not impeded by the attachment. On the outside of body 26, a switch 22 is mounted.

Figure 2 shows the assembly of Figure 1 completed and further mounted in the body 54 of an inhaler 50. -

Figure 3 shows the units of Figure 2 in expanded view -

prior to assembly. Arm 52 of the Inhaler 50 receives and 5 engages nozzle 14 of the canister 10. When the canister -

10 is forced towards arm 52, nozzle 14 is forced into the canister. When nozzle 14 has been depressed by a predetermined amount, a dose of the drug contained In canister TO is dispensed in aerosol form. The body of lo inhaler 50 may include further nozzles or a mouthpiece to facilitate administration of the drug concerned. -

Switch 22 is located such that when canister 10 has travelled far enough to dispense a dose, as detailed above, it is engaged by projection. This causes switch 15 22 to be depressed radially into the body 26 of the attachment, which motion causes the counter to either increment (in the case of a counter initially set to zero which is counting the number of doses dispensed from the inhaler canister) or decrement (in the case of a counter -

20 initially set to the number of doses in the canister and recording the number remaining at any time.

The body 54 of the inhaler 50 shown in Figure 3 also has viewing means, e. g. a window 56, which may be cut out from the body, or be an integral part of the body which

Is translucent. This allows display 30 (see Figure 4 or Figure 5) to be visible to the patient through the body of the inhaler. It will be appreciated that many other ways of mounting the display are possible, and this is s purely an example.

Figure 4 shows a cut-away view of the inside of a first embodiment of attachment 20, showing the switch 22 and hole 32 through which the nozzle 14 passes when the attachment is attached to a canister. Also inside the lo attachment are the circuit board 2B on which the circuitry for the electronic counter is mounted, powered by a power source 36. Mounted in the body 26 of the attachment is a liquid crystal display (LCD) 30 which displays the current status of the counter.

15 Figure 5 shows an alternative embodiment wherein the circuit board 34 is mounted in an alternative position, substantially radially across the body of the attachment.

Figure 7 shows a cut-away view inside a second embodiment of an attachment 20, where the display means 20 includes LEDs 37, 38, (but may include more or fewer) and has a lens 40 mounted on the exterior of body 26 which may focus or disperse the light from those LEDs.

Using LEDs to display the state of the canister rather than an LCD connected to the counter is much

cheaper in terms of components. The second embodiment of the attachment also shows that when using LEDs as the display means, the attachment can be made much smaller, since there is no need to incorporate the display.

5 In a further alternative embodiment, the attachment may have both LEDs and an LCD. For example, the LEDs may be visible to the patient/user when the canister IS in the inhaler body, and give general indication as to the state of the canister, whilst removing the canister from lo the inhaler body allows the LCD to be viewed which gives more detailed information, for example about the exact number of doses used from or remaining In the canister.

Whatever form the display means takes, in order to minimise the size of the attachment, some or all of the 15 electrical components may be mounted on a printed circuit board made from flexible substrate, which allows the circuit board to be fitted into a smaller space.

The embodiments of the invention shows thus far have had a switch 22 mounted on one side of the attachment 20.

20 Figure 8 shows an alternative embodiment in which the switch 42 is mounted on the underside of the attachment (the side furthest from the canister). The switch in this position is activated by coming into contact with the body of the inhaler when the canister and attachment

have moved the required distance for the canister to dispense a dose of the drug.

Figure 9 shows an inhaler body 50 for use with the embodiment of Figure 8. The inhaler body 50 has an arm 5 52, which receives and engages the nozzle 14 of a canister. The body 50 has a further projection 58 which is arranged so as Lo engage with switch 42 when the inhaler and attachment have been moved to a position In which the nozzle 14 of the canister IS sufficiently lo depressed to dispense a dose of drug.

Figure 10 shows a cut-away of an attachment according to a further embodiment of the present invention in which the electronic components are mounted on metal lead frames 90, 92 and 94 rather than on printed circuit boards. The lead frames provide common contacts for the components, such as the application specific integrated circuit (ASIC) counter and tri-colour LED, whilst other connections are made by fine bond-wires (not shown for clarity). Lead frames 94 and 90 are connected 20 to the positive and negative terminals of battery 36 respectively. Lead frame 92 is connected by a bond-wire to ASIC 96. When the switch (not visible) is depressed it connects lead frames 90 and 92 thereby supplying a negative voltage to the ASIC which initiates a count.

The lead frames, components and bond-wires are normally bonded in an epoxy prior to insertion into the attachment 20. This gives the arrangement mechanical stability and strength. The area around the battery 36 5 is not bonded in this manner Lo allow attachment, removal and replacement of the battery after manufacture.

Figure 11 shows the lead frames 90, 92 and 94 before the components are attached and before introduction into

the attachment.

0 The embodiments of the invention shown thus far have generally included four arms 24 which are designed to engage with the ribs 16 of the canister and hold the attachment to the canister. Whilst it is desirable that the attachment may be manufactured separately from the IS canister and the two brought together, for example before distribution or at the point of prescription or sale, the attachment should be reasonably securely fastened to the canister to prevent accidental separation, which could in turn negate the advantage of having the counter attached 20 to the canister.

Figures 12a to 12c show alternative arrangements for the arms 24 of the attachment 20 which engage with the canister. These arrangements are given as examples only, and it will be appreciated that other arrangements are

encompassed by this invention. Similarly, as Figure 12c shows, the counter and associated electronics need not be positioned in a separate body below, but could be housed in the walls of the attachment, for example by mounting 5 on a flexible substrate PCB.

Alternatively or additionally, the attachment may be secured to the canister using devices such as those shown in Figures 13a to 13c.

In alternative embodiments, the attachment may be 0 secured to the canister by other means, such as shown in Figures 14a, 14b and 15. Figures 14a and 14b shows an attachment 20 which has a body 26, but no legs. The attachment is similar to that shown in Figure 8 with the switch 42 mounted on the bottom surface of the body 26.

15 The attachment 20 is secured to the canister by an adhesive which is applied to surface 44 in Figure 14a.

Figure 15 shows the attachment 20 of Figure 14 attached to a canister 10.

An inhaler canister is generally expected to have a 20 "shelf life" prior to prescription or sale of 2 years or more. Once in use, a canister may also last for some time (200 doses daily would last for slightly less than 7 months). Therefore, the counter and display means must be made to consume as little power as possible,

otherwise, the power from the battery may run out towards the end of the life of the canister, just when It IS most needed. Since an inhaler may often be needed at a moment's 5 notice, it will frequently be carried by the user/patient at all times. This can result in the inhaler becoming dirty and therefore unhygienic. Most inhalers are designed so that the canister can be removed and the inhaler body and the canister cleaned separately before 10 being fitted back together. Therefore, if an inhaler canister 10 is fitted with an attachment 20 according to the invention, it is preferable that the attachment can be cleaned without removing it from the canister (thereby avoiding any erroneous readings or users forgetting to reattach the two parts before reassembling the inhaler).

To this end, the body 26 of the inhaler attachment 20 is made waterproof so that it can be cleaned along with the canister 10, without any damage to the counter or electronics contained in the body. This can be done by 20 making the majority of the body from a single piece mould of waterproof material, for example plastic. Once the counter, switch, battery and any other devices have been placed into the attachment, a further piece of waterproof

material (preferably of the same type as the first) can be used to seal the attachment, for example by welding.

To produce a waterproof attachment as described above, it is preferable that the switch can be formed in 5 the mould along with the rest of the attachment, thereby eliminating the need for a further join. This can be particularly achieved if the attachment is moulded from silicone rubber.

In the case of a switch 22 which is mounted on the lo side of the body 26 of the attachment 20, the switch needs to convert the longitudinal motion of the canister 10 and attachment 20 in the inhaler 50 into radial motion of the switch to increment or decrement the counter.

A particular embodiment of a switch 22 which is 15 suitable for use in this invention is shown in Figure 19.

The switch 22 is made from moulded silicone rubber, and is therefore formed from the same material as the surrounding body 26, creating a waterproof seal. The switch 22 is essentially circular in shape (viewed from 20 above) and includes a head 60 and a resilient skirt 62 which joins the head to the body of the attachment 26.

The top of the head has only planar symmetry (about the plane of the drawing) such that the top of the head is offset from the centre of the head 60. A projection 64

extends inwardly away from the head 60. When the head 60 encounters an obstruction whilst moving in the longitudinal direction (relative to the canister/attachment) 75, the head 60, through angled face 5 68 transforms the force exerted in the longitudinal direction 75 into a force acting in the radial direction 80, which deforms the resilient skirt 62 and causes the head and projection to move into the body of the attachment. lo When the inner face 66 of the projection 64 has moved a predetermined distance, it actuates the switch to adjust the counter. This actuation is preferably performed by the face 66 being made from, or covered with, conducting material and being forced into contact 15 with both of two contacts forming opposite sides of an electrical switch (not shown), thereby closing the electrical circuit.

The problems associated with a moulded rubber device which attempts to translate motion in one direction to 20 motion in a perpendicular direction are mainly associated with making sure that the device deforms in the correct direction. In the particular example of this application, it is particularly preferable that the switch 22 deforms such that the projection 64 is

displaced solely in radial direction 80 so that it actuates the counter, for example by contacting the two contacts mounted opposite it and thereby closing the circuit. 5 In order to achieve this, it is preferable that the skirt 62 is thinner towards the front 68 of the head 60 than it IS towards the rear 70 of the head 60. When the head 60 encounters an obstruction when moving in the longitudinal direction 75, this causes the front of the lo skirt 62 to deform before the back and the projection 64 to move substantially in the radial direction 80.

Claims

1. An attachment for the nozzle end of an inhaler canister, the attachment including: 5 an integrated circuit having electronic components including an electronic counter; display means connected to the counter; and a switch, wherein, in use, the switch triggers the counter lo when the canister has travelled far enough to dispense a dose of a drug contained in the canister.

2. An attachment according to claim 1, which, when attached to the canister, does not radially protrude more than 0.5mm beyond the side wall of the canister.

3. An attachment according to claim 1, which, when attached to the canister, does not radially protrude beyond the side wall of the canister.

4. An attachment according to claim 1, wherein the attachment includes at least one arm for engaging a groove in the side of the canister, the arrangement being such that, Allen attached to the canister, the at least

one arm does not radially protrude more than 0.5mm beyond the side wall of the canister.

5. An attachment according to any one of the preceding 5 claims, wherein the cross-sectional area of the attachment is never more than 1.025 x 0, where is the cross-sectional area of the canister.

6. An attachment according to any one of the preceding lo claims, wherein the electronic components are all located in a region of the attachment having an area less than the cross-sectional area of the canister.

7. An attachment according to any one of the preceding 5 claims, wherein the electronic components are all located in a region of the attachment having a longitudinal length of less than 10.5mm.

8. An attachment according to any one of the preceding 20 claims, which, when attached to the canister, extends less than 10.5mm below the bottom of the canister.

9. An attachment according to claim 1, wherein the integrated circuit includes a printed circuit board to

which one or more of the electronic components are connected, the printed circuit: board being made from a flexible substrate.

10. An attachment according to claim 9, wherein the printed circuit board is located in at least one side wall of the attachment.

An attachment according to either one of claims 9 or lo 10, wherein the counter and associated electronic components are located in at least one side wall of the attachment. 12. An attachment according to claim 1, wherein the integrated circuit is mounted on a metal frame, thereby providing a common contact for some of the electronic components. An attachment according to claim 12, wherein at 20 least part of the frame also forms at least part of the switch.

l 14. An attachment according to claim 13, wherein at least part of the frame forms at least part of one of the contacts of the switch.

5 15. An attachment according to any one of claims 12 to 14, wherein the integrated circuit is connected to a battery via the frame and bond wires.

16. An attachment according to claim 15, wherein the lo frame, integrated circuit and bond wires are bonded together as a single piece prior to insertion Into the attachment. 17. An attachment according to any one of claims 12 to 5 16, wherein the frame includes curved leads such that the frame fits around the nozzle of the canister.

18. An attachment according to any one of the preceding claims, wherein the switch includes a button which is 20 displaced radially when it encounters an obstruction on the body of the inhaler whilst being moved in a longitudinal direction.

19. An attachment according to claim 18, wherein the switch includes two electrical contacts and a substantially circular button with a head portion, the button being connected to the body of the attachment by a 5 skirt, both the head portion and the skirt being made from resilient material and the button having a projection extending radially inwards from the head portion. lo 20. An attachment according to claim 19, wherein the face of the projection opposite the head portion is made from, or has on it, conducting material, such that when the button is subjected to a longitudinal force on the head portion, the skirt deforms and the face of the is projection is radially urged into contact with both of the electrical contacts.

21. An attachment according to either one of claims 19 or 20, wherein the skirt has a variable thickness such 20 that a portion of the skirt on the opposite side of the button from the canister deforms before a portion of the skirt between the canister and the button.

l 22. An attachment according to any one of the preceding claims, wherein the attachment includes a waterproof body which encloses the components of the attachment.

s 23. An attachment according to claim 22, wherein the waterproof body is formed from moulded silicone rubber.

24. An attachment according to either one of claims 22 or 23, wherein the switch is moulded as part of the lo waterproof body.

25. An attachment according to any one of the preceding claims, wherein the display means includes one or more light emitting diodes.

26. An attachment according to any one of the preceding claims, wherein the display means includes a liquid crystal display.

20 27. An attachment according to any one of the preceding claims, including a surface for applying adhesive to attach the attachment to the canister.

28. An inhaler canister attached to an attachment according to any one of claims 1 to 27.

29. An inhaler including a body, an inhaler canister and 5 an attachment accordant to any one of claims 1 to 27 attached to said canister.

30. An attachment for the nozzle end of an inhaler canister substantially as described herein, with reference to the accompanying drawings.

31. An inhaler canister, including an attachment, substantially as described herein, with reference to the accompanying drawings.

32. An inhaler, including a canister and an attachment, substantially as described herein, with reference to the accompanying drawings.