Abstract:
An actuator for a pressurised metered dose inhaler, including: a tubular section ( 38 ) providing an outlet through which medicament is in use inhaled; and a nozzle block ( 42 ) including a tubular element ( 44 ) having a free end over which the valve stem ( 14 ) of a canister ( 2 ) is in use located and a spray orifice ( 50 ) in fluid communication with the tubular element ( 44 ) for directing a spray into the tubular section ( 38 ).

Description:
This application is a continuation of Application Ser. No. 09/840,875, filed Apr. 25, 2001, now abandoned which is a continuation of 09/380,294, filed Aug. 31, 1999, now abandoned, which is a National Phase under 35 U.S.C. §371 of PCT/SE99/01198, filed Jul. 3, 1999, the entire content of which is hereby incorporated by reference in this application. 
   The present invention relates to an actuator for a pressurised metered dose inhaler and a pressurised metered dose inhaler including the same. 

   BACKGROUND OF THE INVENTION 
   In using conventional pressurised metered dose inhalers with some hydrofluoroalkane (HFA) formulations being developed by the applicant company it has been found that medicament tends to deposit in the valve stems of the canisters thereof. It will be appreciated that this deposition could lead to the user receiving an unusually high dose of medicament if the deposit were at least in part to break away or, indeed, result in the valve stems becoming blocked, thereby rendering the pressurised metered dose inhalers inoperative. Ideally, one would simply just wash the canisters to remove the deposit. Unfortunately, however, it is not possible to wash the canisters as the formulations are sensitive to moisture and would as a result of washing be contaminated. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention provides an actuator for a pressurised metered dose inhaler, including: a tubular section providing an outlet through which medicament is in use inhaled; and a nozzle block including a tubular element having a free end over which the valve stem of a canister is in use located and a spray orifice in fluid communication with the tubular element for directing a spray into the tubular section. 
   By providing the nozzle block of the actuator with a tubular element over which the valve stem of a canister is located, medicament will deposit on the inner radial surface of the tubular element and not in the valve stem of the canister. In this way, the user is able to prevent the build up of any appreciable amount of deposit by washing the actuator regularly: the actuator being washable when separated from the canister. 
   Preferably, the tubular element is configured such that an outer radial surface thereof is a close fit with an inner radial surface of the valve stem of the canister. 
   More preferably, the tubular element is configured such that an outer radial surface thereof is a tight fit with an inner radial surface of the valve stem of the canister. 
   Preferably, the tubular element is of circular section. 
   Preferably, the nozzle block includes an abutment against which in use bears the distal end of the valve stem of the canister. 
   More preferably, the abutment comprises a surface which extends radially outwardly of the tubular element. 
   In a preferred embodiment the nozzle block includes a further tubular element co-axial with the first-mentioned tubular element such that the tubular elements define an annular channel in which the valve stem of the canister is in use located. 
   Preferably, the further tubular element is configured such that an inner radial surface thereof is a close fit with an outer radial surface of the valve stem of the canister. 
   More preferably, the further tubular element is configured such that an inner radial surface thereof is a tight fit with an outer radial surface of the valve stem of the canister. 
   Preferably, the further tubular element is of circular section. 
   The present invention also extends to a pressurised metered dose inhaler comprising the above-described actuator and a canister including a valve stem extending therefrom. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which: 
       FIG. 1  illustrates a front view of an actuator of a pressurized metered dose inhaler in accordance with a preferred embodiment of the present invention; 
       FIG. 2  illustrates a side view of the actuator of  FIG. 1 ; 
       FIG. 3  illustrates a vertical sectional view of the actuator of  FIG. 1 ; and 
       FIG. 4  illustrates a vertical sectional view of the pressurised metered dose inhaler of the preferred embodiment of the present invention. 
   

   The pressurised metered dose inhaler comprises an actuator  1  and an aerosol canister  2  fitted therein. 
   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The canister  2  comprises a body  4  which defines a storage chamber  6  for holding a suspension or solution of a medicament in a propellant under pressure. The body  4  includes a head  8  which includes a housing  10  that defines a metering chamber  12  and a valve stem  14  that is movably disposed in the housing  10  and extends from the head  8 . The valve stem  14  is movable between an extended, closed position (as illustrated) and a depressed, open position (not illustrated), the valve stem  14  normally being biased by a compression spring  16  disposed in the housing  10  into the closed position. The valve stem  14  includes a first conduit  18  which includes a first, outlet opening  20  located at the distal end of the valve stem  14  and a second, inlet opening  22  located in the side wall of the valve stem  14 . The valve stem  14  further includes a second conduit  24  in that part thereof which is always disposed within the body  4 . The second conduit  24  includes first and second axially-spaced openings  26 ,  28  located in the side wall of the valve stem  14  and enables communication between the storage chamber  6  and the metering chamber  12  via bores  30  in the housing  10 . In this regard, it will be noted that the structure of the metering chamber  12  and the valve stem  14  of the canister  2  is known per se. 
   The actuator  1  comprises a first, main tubular section  32 , one, the upper, end of which is open and provides an opening  34  into which the canister  2  is in use inserted and the other, lower, end of which is closed by a wall member  36 . The actuator  1  further comprises a second tubular section  38  which extends substantially laterally from the other, that is, the lower, end of the main tubular section  32 ; the second tubular section  38  acting as a mouthpiece which is in use gripped in the lips of a user and including an opening  40  at the distal end thereof through which medicament is in use inhaled. The actuator  1  still further comprises a nozzle block  42  which extends upwardly from the wall member  36  into the main tubular section  32 . The nozzle block  42  includes a first tubular element  4 , in this embodiment of circular section, over which the valve stem  14  of the canister  2  is located. The first tubular element  44  is configured such that the radial dimension of the outer radial surface thereof is a close fit with the inner radial surface of the first conduit  18  in the valve stem  14 . In this way, no appreciable amount of medicament can build up between the outer radial surface of the first tubular element  44  and the inner radial surface of the first conduit  18  in the valve stem  14 . In a preferred embodiment the first tubular element  44  is configured such that the radial dimension of the outer radial surface thereof is a tight fit with the inner radial surface of the first conduit  18  in the valve stem  14 . In this way, material cannot escape between the outer radial surface of the first tubular element  44  and the inner radial surface of the first conduit  18  in the valve stem  14 . The first tubular element  44  is further configured to be of such a length as to extend within the first conduit  18  in the valve stem  14  to a position adjacent that part of the second opening  22  in the valve stem  14  which is axially closest to distal end of the valve stem  14 . In this way, the second opening  22  in the valve stem  14  is always open. The first tubular element  44  is located on the longitudinal axis of the main tubular section  32 . In this way, the valve stem  14  will always be aligned with the first tubular element  44  on insertion of the canister  2  into the actuator  1 , thereby allowing easy fitting and removal. The nozzle block  42  further includes a second tubular element  46 , in this embodiment also of circular section, which is co-axial with the first tubular element  44  and is disposed such that the outer radial surface of the first tubular element  44  and the inner radial surface of the second tubular element  46  define an annular channel  48 , the bottom surface  49  of which provides an abutment for the distal end of the valve stem  14 . The second tubular element  46  is configured such that the radial dimension of the inner radial surface thereof is a close fit with the outer radial surface of the valve stem  14 . In this way, lateral movement of the valve stem  14  is prevented, thereby ensuring that the first tubular element  44  cannot be damaged by such lateral movement of the valve stem  14 . In a preferred embodiment the second tubular element  46  is configured such that the radial dimension of the inner radial surface thereof is a tight fit with the outer radial surface of the valve stem  14 . In this way, material cannot escape between the outer radial surface of the valve stem  14  and the inner radial surface of the second tubular element  46 . The nozzle block  42  still further includes a laterally-directed spray orifice  50  which is in fluid communication with the first tubular element  44  and configured to direct a spray into the second tubular section  38  acting as the mouthpiece. 
   In use, a user grips the mouthpiece provided by the second tubular section  38  in the lips. The user then depresses the base of the body  4  of the canister  2  which extends out of the opening  34  in the main tubular section  32  so as to release a dose of medicament from the canister  2  and at the same time inhales so as to inhale the dose of medicament. 
   In this embodiment the actuator  1  is formed entirely of a plastics material, typically by moulding. In an alternative embodiment the first tubular element  44  could be provided by a preformed thin-walled metal tube, such as a stainless steel tube, to which is fitted or moulded a component providing the remainder of the actuator  1 . 
   Finally, it will be understood that the present invention has been described in its preferred embodiment and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.