Abstract:
A counter for indicating the number of doses left in a canister that is suitable for use in a metered dose inhaler. The counter is affixed to the canister and includes a module for providing an indication of the number of doses left in the canister and a triggering mechanism for updating the indication in response to activation of the inhaler.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to electronic monitoring and counting of medication dosages, and in particular to a metered dose inhaler that includes an electronic counter module.  
       BACKGROUND OF THE INVENTION  
       [0002]     Metered dose inhalers (“MDI”) of various configurations are known for dispensing medication into the mouth or nasal passages of a patient. Medication is expelled from the actuator and inhaled by the patient and absorbed by the mouth, nose, throat and lungs. One example is the device commonly used by asthma sufferers for dispensation of airway opening drugs. These are often called “Press &amp; Breathe” inhalers and require simple pressing on the canister and inhalation by the user.  
         [0003]     A pressurized metered dose inhaler (“pMDI”) is designed to deliver therapeutic agents, e.g. medicaments, to the human respiratory tract or nasal cavity. Accordingly, the pMDI contains the active substance, dissolved or suspended, in a fluid propellant system that contains at least one liquefied gas in a pressurized container that is sealed with a metering valve. The actuation of the valve delivers a metered dose of medicament in the form of an aerosol spray and is directed by a suitable adapter/activator for dispensation via oral or nasal inhalation.  
         [0004]     Another type of inhaler is the breath-activated inhaler (“BAI”). A BAI is a device typically for use with a pressurized metered dose inhaler system, and is comprised primarily of an inhalation sensing means, a means to actuate the canister automatically upon an appropriate inhalation profile, and a triggering means to communicate between the two. A BAI can be of any conventional design that has or is capable of being adapted to have, using any conventional means, such as mechanics, electro mechanics, pneumatics, fluid dynamics, a trigger pressure drop of about 0.1 to about 20 cm of water pressure. The “trigger force” refers to the force that is minimally required by the patient to activate the dosing mechanism associated with the device. The breath-activated inhaler typically uses the suction of the user as the triggering force to release the medication.  
         [0005]     Inhalation may be sensed by measuring changes in pressure through the device or by measuring flow rate, directly or indirectly and separately or in combination. The literature is replete with methods for accomplishing this and includes moving vanes or flaps, elastomeric diaphragms, electronic pressure sensors, flow sensors, and combinations of mechanical sensors with electronic timing circuits.  
         [0006]     The canister may be actuated by mechanical (e.g. springs, levers, etc.) electromechanical (e.g. solenoids, motors) or pneumatic means. The canister may be actuated and remain in the actuated position until intervened upon by the patient or may be caused to dwell in the actuated position for some duration returning automatically to rest position without any intervention.  
         [0007]     Traditional MDI inhaler devices are known to be confusing to the user with respect to the number of medication containing actuations remaining in the canister at any one time. Accordingly, the user is faced with the possibility of running out of necessary medication at a critical time. Alternatively, the user must carry additional costly medication at all times to insure that it is always on hand. Further, the disposal of a canister of medication when there are still a number of doses remaining can lead to increased expense in the treatment of an ailment.  
         [0008]     Still further complications with the traditional inhalers mean that a user is forced to manually determine the timing between dosing. As a result it is up to the user to insure that a proper time period has expired between dosing to prevent an overdosing of medication. Similarly, many medications have a maximum threshold for dosing over a specific period. As a result overdosing can occur when more than the predetermined number of actuations are administered in a set period, for example 24 hours. Once again it is up to the user to ensure that no more than the maximum number of actuations is administered over the time period. In addition, the medications may require a sequence of multiple device activations to deliver a complete dose. The user must accurately monitor these activations. With the state of current medical treatments, often a user will have multiple drugs prescribed for the treatment of a single malady. When coupled with the irregularity of the dosing schedules improper dosing of a patient becomes a genuine concern.  
       SUMMARY OF THE INVENTION  
       [0009]     In view of the drawbacks associated with prior inhalers, the inventors have recognized the desirability of tracking the use history of a reservoir device that is used for delivering drugs to the lungs of patients for the purpose of treating local and systemic diseases. Accordingly, the present invention is directed toward such tracking  
         [0010]     In an illustrative embodiment, the invention is implemented in a dose counter for indicating the number of doses left in a canister that is suitable for use in a metered dose inhaler. The counter is affixed to the canister and includes a module for providing an indication of the number of doses left in the canister and a triggering mechanism for updating the indication in response to activation of the inhaler. As an optional feature, the counter can provide an indication of the number of doses taken as part of a predetermined dosage sequence, and/or the number of doses remaining to be taken as part of a predetermined dosage sequence. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The following detailed description, given by way of example and not intended to limit the present invention solely thereto, will best be appreciated in conjunction with the accompanying drawings, wherein like reference numerals denote like elements and parts, in which:  
         [0012]      FIG. 1A  shows a pressurized metered dose inhaler (pMDI) in accordance with the invention;  
         [0013]      FIG. 1B  shows the pMDI of  FIG. 1A  disassembled into a canister assembly and an actuator;  
         [0014]      FIG. 2  is a plan view of a pMDI in accordance with a first embodiment of the invention;  
         [0015]      FIG. 3  is a plan view of a pMDI in accordance with a second embodiment of the invention;  
         [0016]      FIG. 4  is a plan view of a pMDI in accordance with a third embodiment of the invention;  
         [0017]      FIG. 5  is a plan view of a pMDI in accordance with a fourth embodiment of the invention; and  
         [0018]      FIG. 6  is a plan view of a pMDI in accordance with a fifth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     In view of the drawbacks associated with prior inhalers, the inventors have recognized the desirability of tracking the use history of a reservoir device, such as an inhaler, that is used for delivering drugs to the lungs of patients.  
         [0020]     It should be noted that while the invention will be described in the context of dispensing a medicament from canister, it is possible to use the invention for dispensing materials other than medicament from the canister. For example, a breath freshener or candy may be dispensed. Further it will be appreciated by those of skill in the art that the administration of a dose may comprise a single actuation of the device, multiple actuations of the device in succession, or multiple single actuations over a period of time. Further, the term dose as used herein is interchangeable with sprays, puffs, or actuations, administrations, and other terms known to those of skill in the art to signify an available or administered medication release or amount, whether used singularly or to identify a plurality of such actions or amounts.  
         [0021]     In one medical implementation of the invention, the invention provides means for indicating to a patient the number of puffs or actuations remaining in a pressurized metered dose inhaler (pMDI). An additional function provides for display of the number of metered puffs or actuations in a sequence when multiple actuations are required to achieve particular medication levels. The counter/display devices employed in the invention are affixed to the medicament canister. Counting function occurs when a switch coupled to the event counter circuit board is triggered in response to the displacement of the drug canister within an actuator body.  
         [0022]     The display may carryout any number of functions including displaying the number of actuations remaining in the canister, the number of doses remaining in the canister, the time since the last administration, the time till the next administration, an alarm either visual, or audible, or both, administrations over a given time period, and warnings against over administration. Other display options are also available as would be understood by those of skill in the art.  
         [0023]     In this description several alternative embodiments are presented for incorporating an Electronic Dose Counter (EDC) within a pMDI. In each embodiment the counter module is affixed to the pMDI canister, and is thus differentiated from an embodiment in which the counter is affixed or built into an actuator body. In the embodiments of the invention, the visual display is read from above the inhaler, or from a direction that is generally radial with respect to the major axis of the inhaler.  
         [0024]     In each of the described embodiments, relative motion of the canister within the actuator body activates a switch component of the EDC module by means of a trigger mechanism positioned within a cap that is fixedly mounted to the canister. Thus, it is not the relative motion of the canister body or the valve which triggers the counting function, but the trigger mechanism mounted in the cap.  
         [0025]     Preferably, the devices depicted in  FIGS. 1A-6  are generally made of molded plastic, with the exception of the EDC module, the springs, seals and trigger elements. The springs are preferably made of metal and the seals and trigger elements are preferably made of elastomeric materials. Although, one skilled in the art of the invention will, upon review of this description, be able to substitute various materials for the preferable materials.  
         [0026]     Referring now to  FIGS. 1A and 1B , there is shown a pressurized metered dose inhaler (PMDI)  6  in accordance with the invention. As can be seen from  FIGS. 1A and 1B , the inhaler is made up of an actuator  5  and a canister assembly  5   a.  The actuator is constructed to accommodate the canister assembly while providing an inhalation air pathway  4 . The canister assembly includes a canister  3  for holding a medication or other material to be dispensed by the inhaler, an Electronic Dose Counter (EDC) circuit module  1  (as may be more clearly seen in  FIG. 2 ), a Liquid Crystal Display (LCD)  7  for displaying dose count information to a user, and a cap  2  that houses the circuit module and liquid crystal display and is permanently secured to the canister upon manufacture.  
         [0027]     The cap may be attached to the canister using various adhesives, through interference fit, or through snap fit. Regardless of methodology, the counter module  1  is isolated and sealed from the inhalation pathway  4  of the actuator body  5 . This prevents any possible contaminants from entering the air pathway to or from the EDC module.  
         [0028]     By fixedly attaching EDC  1  to canister  3  during manufacture, the numerical count displayed is always associated with the particular canister. When canister  3  is removed from actuator  5  for cleaning, the integral counter module in cap  2  comes with it as a unit. Thus, the counter and canister can not become separated, a condition potentially leading to an inaccurate count. Fully assembled, pMDI  6  is ready for use.  
         [0029]     Upon actuation, the entire canister assembly is depressed and the cap  2  and canister  3  move together as a unit. At the appropriate point, just prior to the discharge of medicament via the metering valve, a switch on the EDC module is triggered as the cap moves toward the top edge of the actuator body  5  (see  FIGS. 2-6 ). The design of such switching takes into account the appropriate travel distance of the canister to the drug discharge position with accommodation for over-travel to ensure that actuation of the EDC module never impedes the motion of the canister within the actuator body. At the end of travel of canister valve stem  3   a,  the assembly comes to a “hard stop.” 
         [0030]     The EDC module is sealed in the cap as noted above. It is further noted that in some embodiments it may be desirable to key or index the canister assembly so that the assembly does not turn about the axis of the actuator. In other cases, the canister assembly and actuator may rotate independently of each other.  
         [0031]     Referring now to  FIG. 2 , there is shown a plan view of a pMDI in accordance with a first embodiment of the invention. In the  FIG. 2  embodiment, the LCD  7  is located on top of EDC module  1 , and a trigger assembly  8  is mounted at a peripheral edge of cap  2 . The trigger assembly is made up of a first plunger  10  in communication with an upper edge  11  of actuator body  5 . A second plunger  12  is positioned about the proximal end of a spring  13  that is fitted between the first and second plungers. The second plunger is positioned to contact button  19  of switch  14  on EDC  1  circuit board. As a user urges the canister assembly down into the actuator body, upper edge  11  of the actuator body forces plunger  10  to compress spring  13  which, in turn, causes plunger  12  to contact button  19  to close switch  14 . The closing of switch  14  causes the dose count to be updated. The updated dose count is displayed on LCD  7 . Thus, update of the display count occurs at a predetermined point in the travel of canister  3  within actuator  5 , and spring  13  absorbs any over travel of canister  3  after the discharge of medicament.  
         [0032]      FIG. 3  is a plan view of a pMDI in accordance with a second embodiment of the invention. As in the  FIG. 2  embodiment, the LCD is positioned at the top of the cap. The attachment of the cap to the canister is also the same as described in connection with the  FIG. 2  embodiment. However, the switching mechanism in  FIG. 3  differs from that of  FIG. 2 . In  FIG. 3 , count actuation is achieved through a horizontally mounted flip-up style switch  14  (e.g. PANASONIC P11152STR). When the canister is depressed relative to the actuator, switch  14  is closed to register a count, as upper edge  11  of the actuator deflects an integral, spring-biased, position-sensing arm  15  on switch  14 . Over travel is accommodated within the switch mechanism itself.  
         [0033]      FIG. 4  is a plan view of a pMDI in accordance with a third embodiment of the invention. As in the  FIG. 2  and  FIG. 3  embodiments, the LCD is positioned at the top of the cap. Also the attachment of the cap to the canister is the same as described in connection with the  FIGS. 2 and 3  embodiments. However, in the  FIG. 4  embodiment, switching is achieved through a switch  16  that is mounted at an edge  17  of an EDC  1  circuit board. Orientation is such that the direction of actuation of switch  16  is parallel to the plane of the circuit board of EDC  1 . A boss, or rib,  18  on the inside of upper edge  11  of actuator  5  slides against switch  16  depressing contact button  19  to initiate a count. Actuator  5  with rib  18  can then travel past the closure position of switch  16  by an amount sufficient to accommodate over travel without causing a false count by again actuating switch  16  on return travel.  
         [0034]      FIG. 5  is a plan view of a pMDI in accordance with a fourth embodiment of the invention. As in the  FIGS. 2, 3  and  4  embodiments, LCD  7  is mounted at the top of the cap. A switch  16   a  is mounted to the EDC  1  circuit board and has a line of action that is horizontal relative to orientation of the depicted inhaler. The actuation mechanism is similar to the plunger mechanism in the device of  FIG. 2 . A plunger  20  is slideably retained in a cylindrical compartment  21  within the cap. Plunger  20  has a circumferential protrusion, or lobe,  22  near proximal end  23 . A spring  24  is retained in a compartment  21   a  and engages the end of plunger  20 . The distal end of plunger  20  rides on the upper edge  11  of actuator  5 . Downward motion of the canister assembly relative to the actuator causes plunger  20  to move upward against the force of spring  24 , raising lobe  22  and displacing contact button  19  in transit, thereby initiating a count. Over travel is accommodated by additional compression of spring  24 . Range of motion is constrained to prevent an additional count upon return of plunger  20  to the “at rest” position. The  FIG. 5  embodiment has potential advantages for sealing during manufacture.  
         [0035]      FIG. 6  is a plan view of a pMDI in accordance with a fifth embodiment of the invention. In the  FIG. 6  embodiment, LCD  7  mounted on EDC  1  within cap  2  is attached to canister  3  such that it faces out from the side of the inhaler rather than facing up from the top of the inhaler. In this manner, the LCD  7  can be keyed to face the user when the user holds the inhaler in position to deliver medicament. The cap of the  FIG. 6  embodiment is keyed to prevent rotation of the canister within the actuator body, thereby maintaining the appropriate orientation of the display. A switch  14  is mounted on EDC  1  circuit board such that contact button  19  is lodged against an elastomeric seal  25 . A ramp shaped projection  26  is molded into seal  25  and is displaced by the upper edge  11  of actuator  5  as the canister assembly moves downward relative to the actuator body. The motion of the seal  25  and projection  26  against button  19  effects a display count on EDC  1 .  
         [0036]     Modifications to the present invention would be obvious to those of ordinary skill in the art in view of this disclosure, but would not bring the invention so modified beyond the scope of the appended claims.