Powder inhaler

Abstract: An inhaler for inhaling pulverulent medicament from within a capsule comprises a chamber 24 within which the capsule is free to rotate while having its longitudinal axis in the median plane of the chamber and thus generally parallel to the front and rear walls 29 and 30 of the chamber, by virtue of the fact that the spacing between said front and rear walls is less than the axial length of the capsule but just greater than the diameter of the capsule. The device includes pins 21 serving as opening means to pierce the ends of the capsule while it is seated in a recess 25, whereupon the retraction of the pins 21 allows the capsule to be entrained into swirling airflow in the chamber 24 during inhalation of air through air inlets 26 and out through a mouthpiece nozzle 27.

Description: The present invention relates to an inhaler for the inhalation of a medicament, usually pulverulent, from a capsule. Various forms of inhaler are already known, and among these are the ones in which the capsule is pierced, usually at the ends, in order to allow the medicament to be withdrawn during inhalation, and those in which the cap portion of the capsule is removed from the body portion in order to allow the medicament to be extracted. Extraction of the medicament usually occurs as a result of the inhaled airstream passing over or through the capsule. With both of the above types of inhaler, it is known to allow the airstream passing through the inhaler to adopt a vortical configuration which results in the pierced capsule or the separated capsule cap and body portions tumbling in the airstream. It is a disadvantage of virtually all of the known inhalers that not all of the medicament is withdrawn from the capsule or the separated capsule cap and body portions, and this is frequently because the capsule portions or the capsule as a whole can become lodged in the inhaler in a position where either the extraction effect of the inhalation air is unable to operate effectively or the capsule or capsule cap and body portions can become prevented from tumbling freely by a mechanical constraint. It is an object of the present invention to provide an inhaler in which the disadvantages mentioned above are eliminated. In accordance with the present invention there is provided an inhaler which comprises a chamber defined by (a) first and second generally parallel spaced opposed walls defining a median plane of said chamber mid-way therebetween, and between which parallel spaced walls the capsule can fit with its longitudinal axis generally parallel to said first and second walls but in any angular orientation, and (b) at least one peripheral wall; an exhaust nozzle through which air can be exhausted from said chamber by inhalation; at least one air inlet arranged in relation to the exhaust nozzle to generate in the chamber during inhalation an airflow rotating about an axis generally perpendicular to said first and second walls; and holding means in the inhaler in association with means operable from outside the closed chamber for opening a capsule while held in the holding means, wherein the holding means are effective to hold a capsule having a length greater than the minimum spacing between said first and second walls and less than the minimum cross-sectional dimension of said chamber when viewed parallel to said axis of rotation and is configured to hold a capsule having a diameter less than said minimum spacing between the first and second walls; characterised in that the holding means are effective to hold said capsule with the longitudinal axis of the capsule perpendicular to said axis about which the inhalation air rotates and substantially coincident with the median plane of said chamber, and in that said capsule opening means comprises means for physically separating the cap portion of the capsule from the body portion of the capsule whereupon said separated cap and body portions are able to tumble in the chamber during inhalation. WO 89/07464 discloses an inhaler comprising two body parts hinged together, one of them including an internal socket to receive one end of a capsule and also including a central pin which will pierce the end of a capsule pressed into that socket. After piercing, the capsule is then placed in an inhalation chamber which confines the capsule to an orientation substantially perpendicular to the axis of rotation of the swirling chamber during operation. EP-A1-0041783 discloses an inhaler comprising male and female parts which are pressed together while a capsule is placed in a recess in the top of the male part, so as to be oriented parallel to two capsule-piercing pins which are activated as the female part is slid into position. EP-A1-0005585 discloses a similar inhaler having an elongated mouth piece operating in the same way. In order that the present invention may more readily be understood the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:- FIGURE 1 is a side elevational view of an inhaler in accordance with the present invention; FIGURE 2 is a transverse sectional view of the inhaler of Figure 1; FIGURE 3 is a sectional view taken on the line 3-3 of Figure 2, with the capsule in position ready for opening by the opening means; FIGURE 4 is a view similar to Figure 3 but showing the inhaler slightly later during the operating cycle in which the capsule has just been opened; FIGURE 5 is a view, again similar to Figure 3, but this time showing the two separated capsule portions in the chamber being tumbled to remove the contained medicament; and FIGURE 6 is an underneath plan view showing the rear casing, with an optional hinged cover to facilitate loading of a capsule to be opened. Referring now to the drawings, Figure 1 shows a mouthpiece nozzle 1 on a plate 2 forming one wall of a capsule-emptying chamber 3 (Figure 2). The opposite wall of the chamber 3 is defined by a rear casing panel 4 which is removable in order to allow a capsule 5 to be inserted into the inhaler ready for opening. The two parts of the device are held together by means of a bayonet system to be described later. In register with the air passage 6 centrally within the mouthpiece nozzle 1 is a grid 7 which is preferably anti-static by virtue of a high electrical conductivity and/or low surface resistivity, and/or high surface electrostatic dissipativity, through which grid the inhalation air passes but through which fragments of the capsule casing are unable to pass, and hence unable to enter the respiratory tract of the user. Figure 2 shows an important characteristic of the present invention in that the cross-section of the capsule 5 is only slightly smaller than the minimum spacing between the planar right hand chamber wall (defined by the panel 2 and the screen 7) and the planar left hand chamber wall (defined by the rear casing panel 4) with the result that both the capsule body 5 a and the capsule cap 5 b are prevented from adopting any other orientation than one in which their axes of symmetry are parallel to the planes of the left hand and right hand chamber walls. It will of course be appreciated that the chamber 3 is defined not only by the left hand and right hand walls 4 and 7, respectively, but also by transversely extending walls such as the partition 8 shown in Figure 2. Figure 1 illustrates an air inlet 9 which is one of several such inlets of the inhaler. Figure 3 shows a sectional view taken on the line 3-3 of Figure 2, and illustrates not only the above-mentioned air inlet opening 9, but also two further air inlets 10 and 11, the functions of which will be described below. Figure 3 again shows the capsule 5 in position ready for opening, with the capsule cap portion 5 b held between an arcuate baffle 12 and an anvil 13. Alternatively the capsule could be positioned in the same manner except that the body portion 5 a is squeezed between the baffle 12 and anvil 13 and the cap portion 5 c will be removed by a knife 14 (Figure 4). In this position the capsule 5 has its longitudinal axis in the median plane of the chamber, i.e. the plane perpendicular to the axis of symmetry and located mid-way between the panels 2 and 4. The capsule is inserted into this position by sliding in a direction perpendicular to the plane of the paper of Figure 3, either with the rear casing panel 4 removed from the rest of the inhaler or by insertion through an optional insertion port to be described below with reference to Figure 6. Figure 3 also shows a capsule holding anvil 13 moulded integrally with the mouthpiece panel 2. Likewise, the arcuate baffle 12 is integrally moulded with the panel 2. Rotatable relative to the arcuate baffle 12, by virtue of being moulded integrally with the rear casing panel 4, is an opening knife 14 which rotates in the clockwise direction during operation of the inhaler from the loading configuration to the inhalation configuration, so as to flick the capsule body portion 5 a away from the cap portion 5 b , as shown in Figure 4 at the instant of separation of the capsule portions 5 a and 5 b . Behind the opening knife 14 is a guide member 15 which, at the instant when a capsule ejector 16 also carried by the rear casing panel 4 ejects the capsule cap portion 5 b from between the baffle 12 and the anvil 13, as shown in Figure 5, cooperates with the anvil 13 to define a passage along which the portion of the capsule which has just been ejected from between the anvil 13 and the baffle 12 must pass towards the inhalation chamber 3. This guiding action prevents the ejected capsule portion from being jammed. It will also be appreciated that the trailing wall 19 on which the guide member 15 is formed also provides a near seal with the baffle 12, having the result that the majority of the inhalation air sweeps generally tangentially into the chamber 3 by way of the inlet orifices 9 and 10, although the additional air inlet orifice 11 does allow a purge stream to pass along an arcuate passage 17 between the arcuate baffle 12 and an outer wall 18 of the inhaler, in order to purge the spacing between the baffle 12 and the anvil 13 of any medicament which may have been spilt there as a result of the opening operation. The existence of this purge stream through the air inlet 11 therefore further enhances the degree of emptying of the medicament from the inhaler as a whole. The various inlets 9, 10 and 11 thus contribute to the creation of a vortical airflow in the chamber 3. It will of course be appreciated that there are three important criteria of the device in accordance with the present invention:- (i) the pressure drop across the loaded inhaler, between inlet 9 or 10 and the inhalation mouthpiece 1 should be as low as possible; (ii) there is a need for as near perfect as possible delivery of the medicament from within the capsule in order to allow the medicament to enter the inhalation airstream; and (iii) there is equally a need for as high as possible a degree of emptying of the device as a whole, because the efficiency of delivery of the medicament depends not only upon the medicament being removed from the capsule but also upon the medicament actually reaching the respiratory tract of the user during inhalation. The final position, shown in Figure 5, when the inhaler is in the relative rotational positioning of its two major parts where the capsule has been opened and released into the spinning chamber 3 for capsule emptying, is the only one in which the various air inlets 9, 10 and 11 all communicate with the interior of the device by means of the corresponding inlet gaps 9 a , 10 a and 11 a respectively. In all other positions they are closed in that the ports are not aligned until the capsule has been opened. Figure 6 shows an alternative embodiment of the device in which the rear casing panel 4 a includes a capsule insertion port with a hinged or push fit cover 20 which can be opened to facilitate insertion of a capsule 5 in order to allow the device to be loaded without the need to separate the mouthpiece 1 and its panel 2 from the rear casing panel 4. However, these portions will nevertheless normally need to be separated at the end of the operating cycle in order to allow the spent capsule body and cap portions to be removed and permit cleaning of the device by the user. The bayonet system, mentioned above, for holding the two parts of the device together comprises a pin 17 on the exterior of the skirt of the mouthpiece member engageable in an axially extending slot 18 (Figure 1) in the skirt of the rear panel part. This slot opens into a groove 19 running round the skirt of the rear panel over approximately 80° of arc of the rear panel part, so as to permit rotation of the rear panel part relative to the mouthpiece part without axial separation of these two parts. In order to minimise the extent to which the released powdered medicament can agglomerate on the surface of the air passage through the inhaler, the panels 2, 4 and the partition 8 which define the chamber portion 3 may be formed of a polymer with a low surface resistivity, thereby having anti-static properties. Preferably the material defining the inside wall of the chamber 3 is a polymer having a surface resistivity less than 10 12 Ohms or more preferably less than 10 8 Ohms. In the present embodiment, the entire device is formed of the same polymer of low surface resistivity, but if desired the chamber-defining walls may be provided with an inner lining of the polymer of low surface resistivity. There are various additives known to increase the anti-static properties of polymers, for example by increasing the electrical conductivity or reducing the surface resistivity, or enhancing the static dissipativity properties. One possibility is to incorporate carbon or steel filler, often in the form of fibres, into the polymer used for manufacture of those components to be given enhanced anti-static properties. This enhances the electrical conductivity and/or lowers the surface resistivity. Alternatively non-fibrous chemical additives, often blended into the moulding polymer in chip form prior to the moulding process, may be used to lower the surface resistivity in the moulded product. The product Pebax manufactured by the company Atochem of France is a polyether block amide product which may be obtained in an antistatic grade by use of such additives. Alternative materials for this application include the Atmer range of polypropylenes, containing antistatic additives, manufactured by ICI. Another possibility is for the moulded component to be coated with an electrically conducting layer which thus reduces the surface resistivity. Preferably the surface resistivity is less than 10 12 Ohms, and more preferably it is less than 10 8 Ohms. More preferably the mouthpiece in any of the embodiments may have at least its inner wall formed of such a polymer of low surface resistivity. The embodiment of Figures 1 to 6 is formed by injection moulding. The above-mentioned polymeric material of low surface resistivity is itself capable of injection moulding to form the relevant parts of the device, or the whole of it. Provided the inhaler is kept dry, and if the material chosen for all of the embodiments of the inhaler in accordance with the invention is one which has relatively low electrostatic attraction for the powder in the capsule, the inhaler will not need regular cleaning when used by the same patient (i.e. other than for considerations of hygiene). It will be appreciated that each of the embodiments described in the present application has the feature of the capsule being opened in the inhaler, while oriented with its major axis in the median plane of the chamber in which the swirling inhalation airflow will cause the capsule to tumble to discharge its contents. This opening operation relies on physical separation of the capsule body from the capsule cap while positioned to one side of the chamber, in a position almost tangential to the airflow which is generated during inhalation. The present invention achieves high efficiency of removal of the medicament from not only the capsule but also the inhalation device as a whole, by (i) allowing random impact of the capsule ends with the walls of the chamber, and by (ii) ensuring that the axis of symmetry of the capsule or of the individual separated capsule cap and body parts during the tumbling operation remains generally parallel to the median plane of the chamber so as to give the best possible centrifugal action, and equally the optimum pneumatic suction on the interior of the capsule, during the inhalation operation. If the capsule were able to tumble into a different orientation where the axis of symmetry becomes anything other than parallel to the median plane of the chamber, the degree of suction will be attenuated, or at least less reliable in strength. It is a feature of the inhalers disclosed in the present application that the contents of the capsule can be efficiently entrained in the airstream even at the relatively low airflow rates likely to be associated with users with impaired respiratory functions. There are various alternative possibilities for the configuration of the chamber, and it is felt that the adoption of a chamber in which the shape is not fully cylindrical is preferable in that this will give rise to an increased likelihood of percussive impact on the walls of the recess 25 to tap the contents of the capsule clear of the ruptured capsule shell and capsule body and cap portions. To ensure that there is no likelihood of the capsule being trapped in an inclined position, it is preferable for the axial length of the chamber to be less than the axial length of the cap portion (this being shorter than the body portion) of the capsule. There are known inhalers using recesses formed in the opposed walls As indicated above, the material used for the walls defining at least the swirling chamber, and preferably also the mouthpiece, may in all embodiments of the inhaler in accordance with the present invention be one which is not likely to generate a high electrostatic charge which would cause the released pulverulent medicament to adhere to the surface of the body of the inhaler rather than passing outwardly through the mouthpiece nozzle. Although in each of the above embodiments the first and second walls of the chamber, namely the opposed walls which together constrain the capsule or each separated capsule portion to maintain its axis of symmetry parallel to the median plane of the chamber are shown throughout as flat, it is of course possible for these walls to be other than truly flat, while still maintaining a shape sufficiently close to the flat shape for allowing the desired capsule-constraining action to be effected. Where the walls are not flat, it is the minimum spacing between these walls which is related to the dimensions of the capsule. The spacing between these first and second opposed walls defined by the rear casing panel 4 and the grid 7 is less than the axial length of the capsule body portion 5 a and less than the axial length of the capsule cap portion 5 b .

Claims: An inhaler which comprises a chamber defined by (a) first (4) and second (7) generally parallel spaced opposed walls defining a median plane of said chamber mid-way therebetween, and between which parallel spaced walls the capsule (5) can fit with its longitudinal axis generally parallel to said first and second walls but in any angular orientation, and (b) at least one peripheral wall; an exhaust nozzle (6) through which air can be exhausted from said chamber by inhalation; at least one air inlet (9, 10) arranged in relation to the exhaust nozzle to generate in the chamber during inhalation an airflow rotating about an axis generally perpendicular to said first and second walls; and holding means (12, 13) in the inhaler in association with means (13, 14) operable from outside the closed chamber for opening a capsule while held in the holding means, wherein the holding means are effective to hold a capsule having a length greater than the minimum spacing between said first and second walls and less than the minimum cross-sectional dimension of said chamber when viewed parallel to said axis of rotation and is configured to hold a capsule having a diameter less than said minimum spacing between the first and second walls; characterised in that the holding means are effective to hold said capsule with the longitudinal axis of the capsule perpendicular to said axis about which the inhalation air rotates and substantially coincident with the median plane of said chamber, and in that said capsule opening means (13, 14) comprises means for physically separating the cap portion (5 a ) of the capsule from the body portion (5 b ) of the capsule whereupon said separated cap and body portions are able to tumble in the chamber during inhalation. An inhaler according to claim 1 characterised in that the minimum spacing between said first and second walls of the chamber is less than the axial length of said capsule cap portion (5 a ) and than that of said capsule body portion (5 b ). An inhaler according to either of claims 1 and 2, and further characterised by including means for closing said air inlets until inhalation is required, and wherein said capsule opening means are effective to open the capsule only while said air inlets are closed. An inhaler according to any one of claims 1 to 3, characterised in that the chamber has walls defined of an anti-static member having a surface resistivity of less than 10 12 Ohms.

Inventors: CALVERT JOHN RICHARD, COOK ROBERT STANLEY, HOBBS MICHAEL ANTHONY, LEIGHTON ANN-MARIE, SIMPKIN GORDON THOMAS, TRUNLEY ROY, WEST ANTHONY DOUGLAS, CALVERT, JOHN RICHARD, COOK, ROBERT STANLEY, HOBBS, MICHAEL ANTHONY, LEIGHTON, ANN-MARIE, SIMPKIN, GORDON THOMAS, TRUNLEY, ROY, WEST, ANTHONY DOUGLAS
Applicants: AVENTIS PHARMA LTD, AVENTIS PHARMA LIMITED
Application year: 1991
Main classification: A61M15
IPC codes: A61M15, A61M13