Abstract:
An inhaler for administering powder by inhalation, including a plurality of surfaces defining a flow path through which a stream of air is in use drawn on inhalation by a user. The flow path including a mouthpiece; and dosing means for providing a dose of powder to the flow path for entrainment in the stream of air. The inhaler further comprises a movable member downstream of the dosing means for inhibiting accumulation of powder on a surface of the flow path downstream of the dosing means.

Description:
BACKGROUND 
     The present invention relates to a powder inhaler for administering powder by inhalation. 
     A number of powder inhalers are known which use different systems for introducing a dose of powder into an air stream. Typically, the powder is inhaled into the lungs of a patient in order to treat, for example, asthma. 
     One such powder inhaler is disclosed in EP-A-0237507. This inhaler comprises an inhalation channel and a mouthpiece comprising an air chamber and an outlet nozzle, which together define a flow path through which a stream of air is drawn during inhalation by a user. This inhaler further comprises means for introducing powder into the inhalation channel. During inhalation, air is first drawn into and through the inhalation channel so as to pick up powder. The stream of air containing powder is then drawn through the air chamber and out of the outlet nozzle of the mouthpiece. 
     FIG. 1 illustrates such a powder inhaler. The inhaler comprises a mouthpiece  2  comprising an outlet nozzle  4 , an inhaler body  6  and a rotatable grip portion  8  for operating a dosing mechanism for providing doses of powder for inhalation. The inhaler body  6  is provided with an opening  10  which is filled with a window  12  through which an indicating wheel  42  is visible so as to provide an indication as to the usage of the inhaler. 
     FIG. 2 illustrates in exploded view component parts disposed within and to the inhaler body  6 . The inhaler body  6  is capped with a divider  14  which is fixed thereto. For aesthetic reasons the inhaler body  6  is an opaque moulding. The divider  14  is a transparent moulding which has a depending tongue  15 , a part of which forms the window  12 . 
     Within the inhaler body  6  are housed the component parts of the dosing mechanism. These component parts include a dosing unit  16  which comprises a member  17  having a planar surface in which a plurality of dosing means  18  are provided and a shaft  20  which extends axially from the centre of the member  17 , an inhalation unit  22  which comprises an inhalation channel  24  and a storage unit  26  which comprises a storage chamber  28  for storing powder. The above-mentioned component parts of the dosing mechanism are assembled by passing the inhalation channel  24  through an opening  30  in the storage unit  26  and passing the shaft  20  through central openings  32 ,  34  in the inhalation unit  22  and the storage unit  26  respectively. When so assembled, the upper ends of the inhalation channel  24  and the storage chamber  28  pass respectively through first and second openings  36 ,  38  in the divider  14 . In this way, the inhalation unit  22  and the storage unit  26  are fixed in position in relation to one another and the dosing unit  16  can be rotated relative thereto. 
     In this inhaler the storage unit  28  is open at the bottom such that in use powder is provided to the dosing unit  16  under the action of gravity and the inhalation unit  22  further comprises scrapers  40  which are resiliently biased against the surface of the member  17  in which the dosing means  18  are provided. In this way, as the dosing unit  16  is rotated, the dosing means  18 , which in this inhaler comprise a plurality of through holes, are filled with powder by the scrapers  40 . Powder is prevented from passing through the dosing means  18  by a plate (not illustrated) which is disposed beneath the dosing unit  16 . 
     As illustrated in FIG. 2, the divider  14  further comprises supporting means  41  for rotatably supporting an indicating wheel  42 . The indicating wheel  42  has a plurality of teeth  44  disposed around the periphery thereof which engage with a spiral groove or protrusion  46  on the end face of the shaft  20 . The supporting means  41  is configured to align the indicating wheel  42  such that a part of the periphery thereof is disposed adjacent the inner surface of the window  12 . In use, as the dosing unit  16  is rotated, the spiral groove or protrusion  46  engages with one or more of the teeth  44  on the indicating wheel  42  so as to rotate the same. In this way, by providing a coloured marking on the periphery of the indicating wheel  42 , it is possible to provide the user with a visible indication at the window  12  as to the usage of the inhaler. 
     As illustrated in FIG. 4, the mouthpiece  2  is fixed to the divider  14 . The mouthpiece  2  comprises first and second parts  48 ,  50 , the first part  48  being the part which is gripped by the lips of a user and the second part  50  being an insert fitted within the first part  48 . The second part or insert  50  comprises a tubular section  52 , which includes one or more spirally or helically shaped projections  54  that act to deflect the air drawn therethrough and thereby deagglomerate any larger particles of entrained powder, and a substantially radially-directed flange  56 , which provides a surface that together with upper surface of the divider  14  defines an air chamber  58  that is in fluid communication with the inhalation channel  24  through which air containing powder is drawn on inhalation by a user. 
     In use, as described hereinabove, powder is transferred from the storage chamber  28  to one of the dosing means  18 , and, with rotation of the dosing unit  16 , the one dosing means  18  provides a dose of powder to the inhalation channel  24 . In this inhaler the dosing unit  16  is rotated by rotating the grip portion  8  in one sense, the counter-clockwise sense when viewed from above, between first and second angularly-spaced positions. For this purpose the dosing unit  16  comprises wedge-shaped elements  60  disposed around the periphery of the member  17  and the grip portion  8  comprises a resilient member (not illustrated) which is configured to engage with an axially-directed surface  60   a  of a respective one of the wedge-shaped elements  60  so as to rotate the dosing unit  16  by pushing the respective wedge-shaped element  60 . On rotation of the grip portion  8  in the opposite sense, the clockwise sense when viewed from above, between the second and the first angularly-spaced positions, the dosing unit  16  remains stationary and the resilient member is located behind the axially-directed surface  60   a  of the adjacent wedge-shaped element  60 ; the resilient member riding over an inclined surface  60   b  of the adjacent wedge-shaped element  60 . 
     Although the above-described known powder inhaler functions quite adequately, powder may possibly accumulate on surfaces in the flow path therethrough. 
     U.S. Pat. No. 4524769 discloses a powder inhaler in which the mouthpiece includes rotating means provided for deagglomerating powder agglomerates drawn therethrough. The deagglomeration of powder agglomerates is facilitated by air inlets disposed around the periphery of the mouthpiece. None of these inhalers, however, address the problem of powder accumulation on surfaces in the flow path therethrough as identified hereinabove. 
     It is thus an aim of the present invention to provide a powder inhaler having a construction which is such as to reduce the possibility of powder accumulating on surfaces in the flow path therethrough. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides an inhaler for administering powder by inhalation, comprising: a flow path defined by a plurality of surfaces through which a stream of air is in use drawn on inhalation by a user, the flow path including a mouthpiece; and dosing means for providing a dose of powder to the flow path for entrainment in the stream of air; characterized in that the inhaler further comprises a movable member downstream of the dosing means for inhibiting accumulation of powder on a surface of the flow path downstream of the dosing means. 
     Embodiments of this aspect of the invention may include one or more of the following features. 
     Preferably, the flow path includes a chamber having an inlet and an outlet. 
     More preferably, the movable member interrupts the stream of air drawn through the inlet of the chamber and is movable at least partially by the stream of air. 
     Still more preferably, the movable member is a rotatable member which is rotatable about an axis within the chamber and is disposed opposite the inlet of the chamber so as, in use, to present a moving surface towards which the stream of air containing powder drawn through the inlet of the chamber is directed. 
     Yet more preferably, the rotatable member includes at least one element on which the stream of air drawn through the inlet of the chamber acts so as to cause rotation of the rotatable member on inhalation by the user. 
     In one embodiment the rotatable member comprises a disc comprising a plurality of angled arms. 
     Preferably, the angled arms are shaped and configured so as to provide no direct flow path between the inlet and the outlet of the chamber. 
     In another embodiment the rotatable member comprises a tubular section having disposed therein at least one spirally or helically shaped projection and a radially outwardly-extending flange which defines a surface of the chamber. 
     Preferably, the flange is disposed opposite the inlet of the chamber. 
     More preferably, a surface of the flange opposed to the inlet of the chamber includes a relief profiling. 
     In one embodiment the relief profiling comprises an array of recesses. 
     In another embodiment the relief profiling comprises an array of projections. 
     Preferably, the mouthpiece comprises a first, outer part which is gripped by the lips of the user and a second, inner part disposed therewithin, the rotatable member comprising the inner part, with the lower surface of the flange defining an upper surface of the chamber. 
     Preferably, a circumferential outer surface of the flange is a close sliding fit with a circumferential inner surface of the outer part of the mouthpiece. 
     More preferably, the flange includes a downwardly-depending peripheral skirt which defines the circumferential outer surface of the flange. 
     In one embodiment the outer part of the mouthpiece includes a central spindle about which the inner part of the mouthpiece is rotatably mounted. 
     In another embodiment the outer part of the mouthpiece includes an annular sleeve within which the inner part of the mouthpiece is rotatably mounted. 
     Preferably, the outer part of the mouthpiece includes a plurality of holes disposed in spaced relation about the periphery thereof through which supplementary air is drawn on inhalation by the user and the inner part of the mouthpiece includes at least one air deflecting member which is adapted so as to be acted upon by the supplementary air drawn through the plurality of holes. 
     In one embodiment the at least one air deflecting member comprises a plurality of flutes provided to the circumferential outer surface of the inner part of the mouthpiece and the plurality of holes in the outer part of the mouthpiece are disposed in opposed relation to the circumferential outer surface of the inner part of the mouthpiece. 
     In one preferred embodiment the flutes are aligned parallel to the axis of rotation of the inner part of the mouthpiece. 
     In another preferred embodiment the flutes are inclined to the axis of rotation of the inner part of the mouthpiece. 
     In another embodiment the at least one air deflecting member comprises a plurality of angled blades surrounding the tubular section of the inner part of the mouthpiece. 
     In an alternative embodiment the mouthpiece comprises a tubular section having disposed therein at least one spirally or helically shaped projection and a radially outwardly-extending flange which defines a surface of the chamber, and the rotatable member is rotatably mounted adjacent a surface of the flange defining the surface of the chamber. 
     Preferably, the lower surface of the flange defines an upper surface of the chamber. 
     More preferably, the flange is disposed opposite the inlet of the chamber. 
     In one embodiment the rotatable member comprises a disc. 
     Preferably, the disc has the form of a downwardly-opening cone. 
     Preferably, the disc includes at least one substantially centrally located hole. 
     Preferably, a circumferential outer surface of the disc is a close sliding fit with a circumferential inner surface of the chamber. 
     More preferably, the disc includes a downwardly-depending peripheral skirt which defines the circumferential outer surface thereof. 
     Preferably, the chamber includes a plurality of holes disposed in spaced relation about the periphery thereof through which supplementary air is in use drawn on inhalation by the user and the disc includes at least one air deflecting member which is adapted so as to be acted upon by the supplementary air drawn through the plurality of holes. 
     In one embodiment the at least one air deflecting member comprises a plurality of flutes provided to the circumferential outer surface of the disc and the plurality of holes are disposed in opposed relation to the circumferential outer surface of the disc. 
     In one preferred embodiment the flutes are aligned parallel to the axis of rotation of the disc. 
     In another preferred embodiment the flutes are inclined to the axis of rotation of the disc. 
     In another embodiment the at least one air deflecting member comprises a plurality of fins disposed on a surface of the disc directed away from the inlet of the chamber. 
     Preferably, the fins are substantially radially directed. 
     Preferably, a surface of the disc opposed to the inlet of the chamber includes a relief profiling. 
     In one embodiment the relief profiling comprises an array of recesses. 
     In another embodiment the relief profiling comprises an array of projections. 
     The powder inhaler of the present invention may be used with any suitable form of powder, including powders introduced into the air stream in the raw state or as conglomerate, micronized or ordered mixture particles. Furthermore, the active ingredient or ingredients of the powder may be diluted with one or more substances such as lactose and may be for the treatment of various conditions, not necessarily respiratory conditions. Indeed, the powder can include genetic material and need not be restricted to human use only. 
     Medicaments suitable for administration by the powder inhaler of the present invention are any which may be delivered by inhalation and include for example β2-adrenoreceptor agonists, for example, salbutamol, terbutaline, rimiterol, fenoterol, reproterol, adrenaline, pirbuterol, isoprenaline, orciprenaline, bitolterol, salmeterol, formoterol, clenbuterol, procaterol, broxaterol, picumeterol, TA-2005, mabuterol and the like, and their pharmacologically acceptable esters and salts; anticholinergic bronchodilators, for example, ipratropium bromide and the like; glucocorticosteroids, for example, beclomethasone, fluticasone, budesonide, tipredane, dexamethasone, betamethasone, fluocinolone, triamcinolone acetonide, mometasone and the like, and their pharmacologically acceptable esters and salts; antiallergic medicaments, for example, sodium cromoglycate and nedocromil sodium; expectorants; mucolytics; antihistamines; cyclooxygenase inhibitors; leukotriene synthesis inhibitors; leukotriene antagonists; phospholipase-A2 (PLA2) inhibitors; platelet aggregating factor (PAF) antagonists and prophylactics of asthma; antiarrhythmic medicaments; tranquilisers; cardiac glycosides; hormones; antihypertensive medicaments; antidiabetic medicaments; antiparasitic medicaments; anticancer medicaments; sedatives; analgesic medicaments; antibiotics; antirheumatic medicaments; immunotherapies; antifungal medicaments; antihypotension medicaments; vaccines; antiviral medicaments; proteins; polypeptides and peptides, for example, peptide hormones and growth factors; polypeptide vaccines; enzymes; endorphines; lipoproteins and polypeptides involved in the blood coagulation cascade; vitamins; and others, for example, cell surface receptor blockers, antioxidants, free radical scavengers and organic salts of N,N′-diacetylcystine. 
    
    
     Preferred embodiments of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings. 
     FIG. 1 illustrates a perspective view of a known powder inhaler; 
     FIG. 2 illustrates in exploded view component parts of the inhaler of FIG. 1; 
     FIG. 3 illustrates the underside of the mouthpiece of the inhaler of FIG. 1; 
     FIG. 4 illustrates a part-sectional side view of the inhaler of FIG. 1; 
     FIG. 5 illustrates a perspective view of a powder inhaler in accordance with a first embodiment of the present invention; 
     FIG. 6 illustrates a fragmentary part-sectional side view of the inhaler of FIG. 5; 
     FIG. 7 illustrates a fragmentary part-sectional side view of a powder inhaler in accordance with a second embodiment of the present invention; 
     FIG. 8 illustrates a perspective view of the insert of the mouthpiece of the inhaler of FIG. 7; 
     FIG. 9 illustrates a vertical cross-sectional view of a first modification of the insert of FIG. 8; 
     FIG. 10 illustrates a bottom view of the insert of FIG. 9; 
     FIG. 11 illustrates a vertical cross-sectional view of a second modification of the insert of FIG. 8; 
     FIG. 12 illustrates a fragmentary part-sectional side view of a powder inhaler in accordance with a third embodiment of the present invention; 
     FIG. 13 illustrates a fragmentary perspective view of the inhaler of FIG. 12; 
     FIG. 14 illustrates a perspective view of the insert of the mouthpiece of the inhaler of FIG. 12; 
     FIG. 15 illustrates a perspective view of a modification of the insert of FIG. 14; 
     FIG. 16 illustrates a fragmentary part-sectional side view of a powder inhaler in accordance with a fourth embodiment of the present invention; 
     FIG. 17 illustrates a fragmentary perspective view of the inhaler of FIG. 16; 
     FIG. 18 illustrates a perspective view of the insert of the mouthpiece of the inhaler of FIG. 16; 
     FIG. 19 illustrates a fragmentary part-sectional side view of a powder inhaler in accordance with a fifth embodiment of the present invention; 
     FIG. 20 illustrates a fragmentary part-sectional side view of a powder inhaler in accordance with a sixth embodiment of the present invention; 
     FIG. 21 illustrates a fragmentary perspective view of the inhaler of FIG. 20; 
     FIG. 22 illustrates a perspective view of the rotatable disc of the inhaler of FIG. 20; 
     FIG. 23 illustrates a bottom view of the rotatable disc of FIG. 22; 
     FIG. 24 illustrates a vertical cross-sectional view of a first modification of the rotatable disc of FIG. 22; 
     FIG. 25 illustrates a vertical cross-sectional view of a second modification of the rotatable disc of FIG. 22; 
     FIG. 26 illustrates a fragmentary part-sectional side view of a powder inhaler in accordance with a seventh embodiment of the present invention; and 
     FIG. 27 illustrates a perspective view of the rotatable disc of the inhaler of FIG.  26 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Structurally, the powder inhalers in accordance with the preferred embodiments of the present invention have many features in common with the above-described known powder inhaler. For this reason, and in order to avoid unnecessary duplication of description, only the structural differences will be described in detail and reference is made to the preceding description of the known powder inhaler. 
     FIGS. 5 and 6 illustrate a powder inhaler in accordance with a first embodiment of the present invention. 
     This inhaler is a modification of the above-described known powder inhaler. As in the above-described known powder inhaler, this inhaler comprises a mouthpiece  2 , an inhaler body  6  and a rotatable grip portion  8 . In FIG. 5, for convenience of illustration, the mouthpiece  2  is illustrated in phantom with the second part or insert  50  thereof (corresponding to the insert  50  of the mouthpiece  2  of the above-described known powder inhaler) omitted in order that the features of the inhaler ordinarily concealed thereby may be clearly illustrated. This inhaler differs from the above-described known powder inhaler in further comprising a rotatable member, in this embodiment a rotatable disc  62 , having, similarly to a fan, a plurality of angled arms  64  which define an undersurface  65  which opposes the outlet of the inhalation channel  24  (illustrated in phantom in FIG. 6) through which a stream of air containing powder is in use drawn on inhalation by a user. The disc  62  is disposed in the air chamber  58  so as to rotate in a plane parallel to the upper surface of the divider  14  which has associated therewith the outlet of the inhalation channel  24 . The angled arms  64  of the disc  62  are shaped and configured so that there is no direct, that is uninterrupted, flow path therethrough from the inhalation channel  24  to the opposing surface of the air chamber  58  defined by the lower surface of the flange  56  of the insert  50 . In this embodiment the disc  62  is fitted to the divider  14  by an axial fitting  66 . 
     In use, when a user inhales by sucking through the mouthpiece  2 , a stream of air containing powder is drawn through the inhalation channel  24 . This stream of air impacts upon the disc  62  causing the same to rotate. Since the disc  62  interrupts the stream of air drawn through the inhalation channel  24 , preferably by forming an indirect flow path as described hereinabove, powder drawn through the air chamber  58  past the angled arms  64  of the disc  62  is prevented from accumulating on the lower surface of the flange  56  of the insert  50  opposite the outlet of the inhalation channel  24 . Instead, any powder which accumulates deposits continuously around the undersurface  65  of the disc  62  as a thin film. Furthermore, powder is prevented from accumulating on the undersurface  65  of the disc  62  in any appreciable amount as any powder which accumulates is tended to be flung from the undersurface  65  by the centrifugal force developed on rotation of the disc  62 . In this way, powder is prevented from depositing on surfaces within the flow path or is at least continuously dislodged so as to prevent any appreciable accumulation thereon. 
     FIGS. 7 and 8 illustrate a powder inhaler in accordance with a second embodiment of the present invention, with a first modification being illustrated in FIGS. 9 and 10 and a second modification being illustrated in FIG.  11 . 
     This inhaler is a modification of the above-described known powder inhaler. As in the above-described known powder inhaler, this inhaler comprises a mouthpiece  2 , an inhaler body  6  and a rotatable grip portion  8  (not illustrated). This inhaler differs from the above-described known powder inhaler in that the second part or insert  70  of the mouthpiece  2  is rotatably mounted about a spindle  72  which depends downwardly from a crossbeam member  74  that is fixed across and just beneath the outlet nozzle  4  of the outer, first part  48  of the mouthpiece  2 . The spindle  72  is located in a tubular member  76  which has a closed lower end  78  and is centrally axially mounted within the tubular section  79  of the inset  70 , whereby the spirally or helically shaped projections  81  of the tubular section  79  surround the tubular member  76 . The flange  83  of the insert  70  includes a downwardly-depending annular skirt  80  having a circumferential outer surface  82  which is a close, yet freely movable, fit with the corresponding circumferential inner surface  85  of a lower tubular part  84  of the first part  48  of the mouthpiece  2 . 
     In use, when a user inhales by sucking on the mouthpiece  2 , a stream of air containing powder is drawn through the inhalation channel  24  (illustrated in phantom in FIG.  7 ), through the air chamber  58  and upwardly through the tubular section  79  around the spirally or helically shaped projections  81 . The flow of the stream of air past the spirally or helically shaped projections  81  imparts a rotational moment to the insert  70  about the spindle  72 . This rotational moment causes a constantly moving annular part of the undersurface  86  of the flange  83  to be disposed above the outlet of the inhalation channel  24 . The provision of this constantly moving surface towards which the stream of air containing powder is directed tends to prevent localized accumulation of powder, which could happen if the insert  70  were stationary, as a result of a large surface area being presented in a continuously moving fashion above the inhalation channel  24  and the flow being turbulent being at that surface. In addition, any powder which deposits on that moving surface tends to be prevented from accumulating in any appreciable amount as a result of the centrifugal forces developed on rotation of the insert  70  which tend to break up any large bodies of powder that may form. In this way, the possibility of large bodies of powder being formed in the flow path of the inhaler is significantly reduced, thereby preventing a user from receiving an unusually large dose of powder during any given inhalation. 
     FIGS. 9 and 10 illustrate a first modification of the insert  70  of the inhaler of the above-described second embodiment. In this modification the undersurface  86  of the flange  83  is provided with a relief profiling  92  in the form of an array of small recesses  94 . By way of example, the recesses  94  can be any of part-spherical, typically hemi-spherical, or frusto-spherical, the latter consisting of a part-spherical innermost portion inwardly of a frusto-conical portion. The array of recesses  94  is illustrated in FIG.  10 . It will be seen that the recesses  94  are closely packed. 
     FIG. 11 illustrates a second modification of the insert  70  of the inhaler of the above-described second embodiment. In this modification the undersurface  86  of the flange  83  is provided with a relief profiling  92  in the form of an array of small projections  96 . Again, by way of example, the projections  96  can be any of part-spherical, typically hemi-spherical, or frusto-spherical, the latter consisting of a frusto-spherical innermost portion inwardly of a part-spherical portion. Preferably, the array of projections  96  has the same packing as the recesses  94  illustrated in FIG.  10 . 
     In both of the above-described modifications, the provision of recesses  94  and projections  96  on the undersurface  86  of the flange  83  assists in preventing the accumulation of powder which impacts thereagainst as a result of the stream of air containing powder being sucked upwardly through the inhalation channel  24 . Specifically, the recesses  94  and the projections  96  provide an enhanced turbulent flow adjacent the undersurface  86  of the flange  83 , thereby inhibiting the deposition of powder. 
     FIGS. 12 to  14  illustrate a powder inhaler in accordance with a third embodiment of the present invention, with a modification being illustrated in FIG.  15 . 
     This inhaler is a modification of the inhaler of the above-described second embodiment and incorporates means for providing an additional rotational force to the insert  70  of the mouthpiece  2 . In this embodiment the insert  70  is, inhaler of the above-described second embodiment, rotatably mounted about the spindle  72 . However, this inhaler differs from the inhaler of the above-described second embodiment in that the circumferential outer surface  82  of the skirt  80  includes a plurality of substantially axially-directed flutes  102  and in that the lower tubular part  84  of the first part  48  of the mouthpiece  2  includes a plurality of angularly-spaced peripheral holes  104  extending circumferentially therearound which are located so as to coincide with the circumferential outer surface  82  of the insert  70 . In this embodiment the holes  104  are rectangular and elongate in the circumferential direction. In practice, however, the holes  104  may be of any shape and configuration. For example, the holes  104  could be circular. In one preferred embodiment the mouthpiece  2  includes four uniformly-spaced holes  104 . The provision of the holes  104  in the lower tubular part  84  of the first part  48  of the mouthpiece  2  provides additional openings through which supplementary air is drawn when a user inhales by sucking on the mouthpiece  2 . 
     In use, when a user inhales by sucking on the mouthpiece  2 , air is drawn not only through the inhalation channel  24  (illustrated in phantom in FIG. 12) but also inwardly through the holes  104 , which supplementary air drawn through the holes  104  is directed against the flutes  102  on the circumferential outer surface  82  of the insert  70 . This incoming supplementary air tends to impart an additional rotational force on the insert  70 , thereby increasing the rotational effect and further reducing the possibility of powder accumulating on surfaces, particularly the undersurface  86 , of the insert  70 . In this embodiment, the supplementary air, after impacting on the flutes  102 , passes downwardly into the air chamber  58 , and thereafter upwardly through the spirally or helically shaped projections  81  in the tubular section  79 . In an alternative embodiment the inhaler can be configured such that the supplementary air is deflected upwardly from the flutes  102  and thereafter through the outlet nozzle  4  of the mouthpiece  2  via a gap  105  between the outer surface  106  of the tubular section  79  of the insert  70  and the inner surface  108  of the first part  48  of the mouthpiece  2 . 
     FIG. 15 illustrates a modification to the insert  70  of the inhaler of the above-described third embodiment. In this embodiment the flutes  102  on the circumferential outer surface  82  of the skirt  80  are arranged so as to be inclined at an angle, typically around 45°, relative to the axial direction. The provision of such inclined flutes  102  imparts a yet further additional rotational force to the insert  70  when a user inhales by sucking through the mouthpiece  2 . 
     FIGS. 16 to  18  illustrate a powder inhaler in accordance with a fourth embodiment of the present invention. 
     This inhaler is a modification of the inhaler of the above-described third embodiment. In this embodiment, similarly to the inhaler of the above-described third embodiment, the insert  70  is rotatably mounted about the spindle  72  and means are provided for imparting an additional rotational force to the insert  70  for reducing the possibility of powder accumulating on the undersurface  86  thereof. This inhaler differs from the inhaler of the above-described third embodiment in that, similarly to the inhaler of the above-described second embodiment, the circumferential outer surface  82  of the skirt  80  of the flange  83  of the insert  70  is smooth and forms a close but sliding fit with the circumferential inner surface  85  of the lower tubular part  84  of the first part  48  of the mouthpiece  2 . This inhaler further differs from the inhaler of the above-described third embodiment in that the insert  70  further comprises a plurality of angled arms  110 , having the form of the vanes of a fan or turbine wheel, disposed around the lower end of the tubular section  79  of the insert  70  and above the flange  83 . Again, similarly to the inhaler of the above-described third embodiment, a plurality of angularly-spaced peripheral holes  104  are disposed around the lower tubular part  84  of the first part  48  of the mouthpiece  2 . Differently from the inhaler of the above-described third embodiment, however, the peripheral holes  104  are located at an axial position above the circumferential outer surface  82  of the skirt  80 . The provision of the holes  104  in the lower tubular part  84  of the first part  48  of the mouthpiece  2  provides additional openings through which supplementary air is drawn when a user inhales by sucking on the mouthpiece  2 . 
     In use, when a user inhales by sucking on the mouthpiece  2 , air is drawn not only through the inhalation channel  24  (illustrated in phantom in FIG. 16) but also inwardly through the peripheral holes  104 , where the supplementary air drawn through the holes  104  is directed against the angled arms  110  on the tubular section  79 . This incoming supplementary air tends to impart an additional rotational force on the insert  70 , thereby increasing the rotational effect and further reducing the possibility of powder accumulating on surfaces, particularly the undersurface  86 , of the insert  70 . In this embodiment, the supplementary air, after impacting on the angled arms  110 , passes upwardly through the outlet nozzle  4  via the gap  105  between the outer surface  106  of the tubular section  79  and the inner surface  108  of the first part  48  of the mouthpiece  2 . 
     FIG. 19 illustrates a powder inhaler in accordance with a fifth embodiment of the present invention. 
     This inhaler is a modification of the inhaler of the above-described second embodiment. As in the inhaler of the above-described second embodiment, the insert  112  comprises a tubular section  114  which includes one or more spirally or helically shaped projections  116  that act to deflect the air drawn therethrough and thereby deagglomerate any larger particles of entrained powder, and a substantially radially-directed flange  118 , which has an undersurface  119  that together with upper surface of the divider  14  defines the air chamber  58  (as depicted in FIGS.  7  and  12 ). This inhaler differs from the inhaler of the above-described second embodiment in that the insert  112  is rotatably mounted to a tubular sleeve  120  which is fixed by a pair of opposed mounts  122 ,  124  to the inner surface  108  of the first part  48  of the mouthpiece  2 . In this embodiment the cylindrical outer surface of the tubular section  114  and the cylindrical inner surface of the tubular sleeve  120  act as bearing surfaces which allow for free rotation of the tubular section  114  within the tubular sleeve  120 . Again, as in the inhaler of the above-described second embodiment, the flange  118  has a downwardly depending skirt  128 , the circumferential outer surface  129  of which is arranged to provide a close, yet sliding fit, with the circumferential inner surface  85  of the lower tubular part  84  of the first part  48  of the mouthpiece  2 . 
     In use, when a user inhales by sucking through the mouthpiece  2 , a stream of air containing powder is drawn through the inhalation channel  24  (illustrated in phantom), and, as in the inhaler of the above-described second embodiment, the insert  112  is caused to rotate as a result of the flow of that stream of air through the spirally or helically shaped projections  116  in the tubular section  114 . 
     In each of the inhalers of the above-described third to fifth embodiments, the undersurface  86 ,  119  of the flange  83 ,  118  of the insert  70 ,  112  which faces the inhalation channel  24  may be provided with a relief profiling of the kind as described in relation to FIGS. 9 to  11 . 
     FIGS. 20 to  23  illustrate a powder inhaler in accordance with the sixth embodiment of the present invention, with modifications being illustrated in FIGS. 24 and 25. 
     This inhaler is a modification of the above-described known powder inhaler. As in the above-described known powder inhaler, this inhaler comprises a mouthpiece  2 , an inhaler body  6  and a rotatable grip portion  8  (not illustrated). In this embodiment, again as in the above-described known powder inhaler, the first part  48  and the second part or insert  134  of the mouthpiece  2  are fixed to one another. Again, similarly to the above-described known powder inhaler, the insert  134  comprises a tubular section  136  which includes one or more spirally or helically shaped projections  140  that act to deflect the air drawn therethrough and thereby deagglomerate any larger particles of entrained powder, and a substantially radially-directed flange  142 , which provides a surface that together with upper surface of the divider  14  defines the air chamber  58 . This inhaler differs from the above-described known powder inhaler in further comprising a rotatable disc  150  which is mounted to and beneath the insert  134 . In this embodiment the disc  150  has the form of a downwardly opening cone. The disc  150  is provided with a spindle  151  which extends upwardly and centrally axially therefrom, which spindle  151  is rotatably received within a tubular member  152  centrally axially mounted within the spirally or helically shaped projections  140  of the tubular section  136 . The disc  150  includes an annular downwardly-depending skirt  154 , the circumferential outer surface  155  of which includes a plurality of flutes  156 . In this embodiment the flutes  156  are axially-aligned. The flutes  156  may, however, be inclined at an angle relative to the axial direction in a similar manner to the flutes  102  provided to the insert  70  as illustrated in FIG.  15 . The disc  150  further includes at least one hole  158 , preferably a plurality of circularly-extending spaced holes  158 , in the region thereof surrounding the rotational axis along which the spindle  151  and the tubular member  152  are located. The holes  158  permit a flow of air from the air chamber  58  into the tubular section  136 . In this embodiment, three holes  158  are provided, each of kidney shape, with the holes  158  being slightly spaced from each other in a circular direction so as to define a substantially annular composite air conduit through the disc  150 . This inhaler further differs from the above-described known powder inhaler in that, similarly to the inhaler of the above-described third embodiment, the lower tubular part  84  of the first part  48  of the mouthpiece  2  includes a plurality of peripheral holes  104 , with the holes  104  being located opposite the circumferential outer surface  155  of the skirt  154 . The provision of the holes  104  in the lower tubular part  84  of the first part  48  of the mouthpiece  2  provides additional openings through which supplementary air is drawn when a user inhales by sucking on the mouthpiece  2 . 
     In use, when a user inhales by sucking on the mouthpiece  2 , air is drawn not only through the inhalation channel  24  (illustrated in phantom in FIG. 20) but also inwardly through the peripheral holes  104 , where the supplementary air drawn through the holes  104  is directed against the flutes  156  on the circumferential outer surface  155  of the skirt  154 . This incoming supplementary air tends to impart a rotational force on the disc  150  so as to rotate the same, thereby reducing the possibility of powder accumulating on surfaces, particularly the undersurface  162 , of the insert  134 . In this embodiment, the supplementary air, after impacting on the flutes  156 , passes downwardly into the air chamber  58 , through the at least one hole  158  in the disc  150  and thereafter through the tubular section  136  and out of the outlet nozzle  4  of the mouthpiece  2 . 
     FIG. 24 illustrates a first modification of the disc  150  of the inhaler of the above-described sixth embodiment. In this modification the undersurface  162  of the disc  150  is provided with a relief profiling  166  in the form of an array of small recesses  168 . By way of example, in the same manner as the recesses  94  provided to the undersurface  86  of the insert  70  as illustrated in FIGS. 9 and 10, the recesses  168  can be any of part-spherical, typically hemi-spherical, or frusto-spherical, the latter consisting of a part-spherical innermost portion inwardly of a frusto-conical portion. Similarly, the array of recesses  168  can have the same packing as the recesses  94  as illustrated in FIG.  10 . 
     FIG. 25 illustrates a second modification of the disc  150  of the inhaler of the above-described sixth embodiment. In this modification the undersurface  162  of the disc  150  is provided with a relief profiling  166  in the form of an array of small projections  170 . Again, by way of example, the projections  170  can be any of part-spherical, typically hemi-spherical, or frusto-spherical, the latter consisting of a frusto-spherical innermost portion inwardly of a part-spherical portion. The array of projections  170  preferably has the same packing as the recesses  94  as illustrated in FIG.  10 . 
     In both of the above-described modifications, similarly to the projections  94  and the recesses  96  provided to the undersurface  86  of the insert  70  as illustrated in FIGS. 9 to  11 , the provision of the recesses  168  and the projections  170  on the undersurface  162  of the disc  150  assists in preventing the accumulation of powder which impacts thereagainst as a result of the stream of air containing powder being sucked upwardly through the inhalation channel  24 . 
     FIGS. 26 and 27 illustrate a powder inhaler in accordance with a seventh embodiment of the present invention. 
     This inhaler is a modification of the inhaler of the above-described sixth embodiment. Similarly to the inhaler of the above-described sixth embodiment, the first part  48  and the insert  134  of the mouthpiece  2  are fixed to one another. Again, similarly to the inhaler of the above-described sixth embodiment, the insert  134  comprises a tubular section  136  which includes one or more spirally or helically shaped projections  140  that act to deflect the air drawn therethrough and thereby deagglomerate any larger particles of entrained powder, and a substantially radially-directed flange  142 , which provides a surface that together with upper surface of the divider  14  defines the air chamber  58 . Likewise, similarly to the inhaler of the above-described sixth embodiment, this inhaler comprises a rotatable disc  150  which is mounted to and beneath the insert  134 . The disc  150  of this embodiment differs from that of the inhaler of the above-described sixth embodiment only in that the upper surface  172  thereof is provided with a plurality of spaced radially-oriented and upwardly-extending fins  174  which are configured to act as vanes. Similarly to the inhaler of the above-described sixth embodiment, the lower tubular part  84  of the first part  48  of the mouthpiece  2  includes a plurality of peripheral holes  104 , with the holes  104  being located opposite the circumferential outer surface  155  of the skirt  154 . Differently to the inhaler of the above-described sixth embodiment, however, the peripheral holes  104  extend axially above the circumferential outer surface  155  of the skirt  154 . The provision of the holes  104  in the lower tubular part  84  of the first part  48  of the mouthpiece  2  provides additional openings through which supplementary air is drawn when a user inhales by sucking on the mouthpiece  2 . 
     In use, when a user inhales by sucking on the mouthpiece  2 , air is drawn not only through the inhalation channel  24  (illustrated in phantom in FIG. 26) but also inwardly through the peripheral holes  104 , where the supplementary air drawn through the holes  104  is directed both against the flutes  156  on the circumferential outer surface  155  of the skirt  154  and the radially-directed fins  174  on the upper surface  172  of the disc  150 . This incoming supplementary air which impacts the flutes  156  and the radially-directed fins  174  tends to impart a rotational force on the disc  150  so as to rotate the same, thereby reducing the possibility of powder accumulating on surfaces, particularly the undersurface  162 , of the insert  134 . In this embodiment, the supplementary air, after impacting on the flutes  156  and the radially-directed fins  174 , passes through the tubular section  136  and out of the outlet nozzle  4  of the mouthpiece  2 . 
     Finally, it will be understood by a person skilled in the art that the present invention has been described in its preferred embodiments and can be modified in many different ways without departing from the scope of the invention as defined in the appended claims.