Surgery – Liquid medicament atomizer or sprayer – Pre-pressurized container holding medicament
Reexamination Certificate
2000-02-22
2003-09-09
Dawson, Glenn K. (Department: 3761)
Surgery
Liquid medicament atomizer or sprayer
Pre-pressurized container holding medicament
C128S200140, C128S203120
Reexamination Certificate
active
06615826
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an inhaler for medicament and in particular to an inhaler for transferring to the respiratory system of a patient a metered dose of medicament contained in a pressurised dispensing canister.
BACKGROUND OF THE INVENTION
In known metered dose inhalers, the aerosol stream comprising liquefied propellant and medicament from a pressurised dispensing canister is fired into a chamber towards a mouthpiece of the inhaler into an air space that allows airflow travelling in the same direction via openings to the outside air. In known devices at actuation, a user inhales through a mouthpiece of the inhaler and creates an airflow through the chamber from air inlets which are generally at a part of the inhaler located upstream from the mouthpiece. Upon actuation, the medicament is then released into this airflow at a point between the air inlets and the mouthpiece so that it is travelling in the same direction as the airflow. Typically in such devices, there is little restriction in the airflow between the air inlets and the mouthpiece. Because of this, a substantial airflow may be created by a user of the device and, because the medicament is fired into the airflow in the same direction as the airflow, the effect is that particles of medicament can be travelling at quite substantial velocities e.g. in excess of 40 m/s when they reach the mouthpiece. As inhalers of this type are normally designed to be as small as practical for the convenience of users, the distance between the point at which the medicament is fired into the airflow and the patient's mouth is usually quite small so that there is little distance to reduce the inertia of the particles of medicament with the result that the particles may impact and deposit in the oropharynx rather than being carried with inhaled air into the lungs. This is normally quite undesirable, since the medicaments were designed for delivery to the respiratory system and may not have an appropriate effect when deposited in the oropharynx and allowed to enter the digestive tract.
In an effort to overcome this problem, devices have been produced in which the medicament is fired into a holding volume, commonly called a Spacer, which allows the velocity of the medicament to be reduced and also allows some propellant evaporation to occur. Spacers can improve the performance of a metered dose inhaler by reducing oropharyngeal deposition, see S. P. Newman & S. W. Clarke, Chest, vol 103 (5) pp. 1442-1446 (1993) Bronchodilator Delivery From Gentlehaler, A New Low-Velocity Pressurized Aerosol Inhaler and S. P. Newman, A. R. Clark, N. Talee & S. W. Clarke, Thorax, vol 44 pp.706-710 (1989), Pressurised aerosol deposition in the human lung with and without an “open” spacer device.
However, these devices with a holding volume and other spacer devices tend to be of significantly larger size than the conventional metered dose inhalers and therefore less convenient and attractive to users.
Various attempts have been made to modify the spray characteristics of inhalers.
GB-A-2279879 discloses an inhaler in which the air inlets are arranged such that during inhalation an airflow is created which has a component directed away from the mouthpiece towards the aerosol spray. The reverse airflow component is intended to create turbulence and slow the velocity of the medicament particles.
WO93/05837 and U.S. Pat. No. 4,972,830 disclose inhalers in which the passage which directs the pressurised medicament from the canister to the chamber has particular configurations to reduce the velocity of the spray and enhance dispersion of the medicament in the airflow.
EP-A-0412648 discloses an inhaler in which a frusto-conical diverter with a small orifice is positioned in the path of the spray before the mouthpiece. Aerosol droplets are said to predominantly pass through the small orifice, decelerate and be inhaled while the propellant gas is predominantly diverted away from the mouthpiece out of the inhaler.
It is known to modify the airflow through an inhaler to achieve particular effects. WO93/09830 discloses an inhaler which is constructed and arranged to prevent inhalation through the device prior to the dose being fired. The object of the arrangement is to synchronise inhalation and firing the dose to ensure the dose is dispensed during inhalation. U.S. Pat. No. 5,758,638 discloses an inhaler which includes an air port so that during inhalation flow of air through the port activates an audio or visual signal generates, such as a whistle or flag, that signals to the user that the user is inhaling and that the conditions are appropriate for the administration of the medicament.
Similarly for intranasal inhalers it is desirable to reduce the velocity of the spray in the interests of patient comfort and efficacity.
SUMMARY OF THE INVENTION
The present invention provides alternative constructions of an inhaler which reduce the velocity of the spray exiting the mouthpiece or nasal adapter.
According to the present invention there is provided an inhaler for medicament comprising an aerosol canister containing a pressurised medicament formulation equipped with a metered dose dispensing valve having a valve stem movable between non-dispensing and dispensing positions, and an actuator comprising a housing adapted to receive the aerosol container and defining a chamber having one or more air inlets and a patient port in the form of a mouthpiece or nasal adapter, and a nozzle block adapted to receive the valve stem of the dispensing valve, the nozzle block comprising a passage in communication with the valve stem and terminating in an orifice for directing medicament from the valve stem into the chamber, in which the actuator is constructed and arranged to inhibit patient-induced airflow in the vicinity of the orifice of the nozzle block when the valve stem is in its dispensing position.
The inhaler of the invention may be constructed such that airflow due to patient inhalation is prevented or reduced in the vicinity of the orifice at all times or only during dispensing of the medicament from the valve. Either arrangement has the effect of substantially reducing the velocity of the emitted spray compared to an inhaler which allows free flow of air in the vicinity of the nozzle block during dispensing of the medicament. It is possible to modify existing press and breathe inhalers to prevent such airflow by the provision of a suitable gasket.
It has been discovered that the velocity of an aerosol spray from a metered dose inhaler is significantly influenced by the presence of an open conduit in the vicinity of the nozzle through which the spray emerges. The spray exits the nozzle as a high velocity stream which creates low pressure regions. The ability of the free-flowing air entering through air vents to fill the low pressure regions influences the velocity of the emitted spray. If a free flow of air is allowed in the vicinity of the nozzle, as in a standard press-and-breathe inhaler where the patient breathes through the mouthpiece and an airflow is established around the canister and nozzle to the mouthpiece, the emitted spray maintains a high velocity. If the actuator is sealed to outside airflow in the vicinity of the nozzle, the low pressure regions cannot immediately be occupied by the surrounding air and the low pressure regions exert a retarding influence on the stream emanating from the nozzle, thereby causing the stream to lose velocity.
It has been found that inhibiting make-up, or free-flowing air in the vicinity of the nozzle when the spray is generated significantly reduces the velocity of the emitted spray and spray force from the mouthpiece, resulting in an extremely soft, low velocity spray plume.
The vicinity of the orifice includes on all sides upstream to the temporary or permanent closure behind the nozzle block, and downstream to the first communication with the outside atmosphere. That is, during dispensing there is no communication to the outside atmosphere for the region surrounding the orifice of the nozzle block.
Gabrio Brian J.
Velasquez David J.
3M Innovative Properties Company
Dawson Glenn K.
Ringsred Ted
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