This invention relates to a novel air amplifying system and a novel powder delivery device comprising such a system, for example, a medicament delivery device, such as an inhaler.
In particular the invention provides a novel form of dry powder inhaler and a method of delivering a powder using such an inhaler.
Conventional powder delivery devices, such as dry powder inhalers (DPIs), deliver a powder dosage by the aerosolisation of the powder, the aerosolisation being largely driven by the inhalation of the patient. One disadvantage with these conventional DPIs is that the extent of aerosolisation, and therefore the consistency of the dosage delivered, is dependent upon, inter alia, the inspiratory flow of the patient, the nature of the air passage and the nature of the formulation.
Attempts have been made to improve on conventional DPIs by using, for example, an air jet directed at or across a powder. However, such systems suffer from a number of disadvantages in that, inter alia,
(i) A powder container may be difficult to completely empty, giving rise to problems with dosage consistency and with efficiency of delivery. There may also be a lack of any real element of control of the air stream.
(ii) There is no amplification, i.e., the volume of air entering the device is the same as the volume of air leaving the device; which nay limit the efficiency of powder aerosolisation.
(iii) Air flowing across the powder due to the inhalation of a patient can only lift the powder into the airstream and therefore does not efficiently aerosolise the powder.
Conventional metered dose inhalers (MDIs) attempt to address this problem by the use of a volatile propellant to create a pressure sufficient to aerosolise the medicament. However, one disadvantage of MDIs is that the combination of a volatile propellant to create a pressure sufficient to aerosolise the medicament, and a solubilised medicament can give rise to blocking or clogging of the valve through which the aerosolised medicament is emitted. In addition MDIs are disadvantageous in that, inter alia, they lack the ability to co-ordinate actuation with inhalation, and suffer from high drug impaction in the oropharynx, although breath actuation systems may overcome these issues to a certain extent.
U.S. Pat. No. 6,158,675 to Nathaniel Hughes, describes a microatomising device which uses a vortex accumulation resonant chamber the use of which creates a vacuum to enable outside entrainment air to be drawn into the device, lowering the speed of delivery of the medicament particles to the lung.
U.S. Pat. No. 4,114,615 to Draco AB, describes an aerosol inhalation device which, inter alia, activates a liquid propellant. In use, the propellant flows past a capillary arranged in a medicament container. The specification describes, at column 3, lines 59 to 63, that when the propellant passes across the top of the capillary, the medicament is drawn from the chamber.
U.S. Pat. No. 5,657,794 to Inhale Therapeutics Inc. describes a dry powder inhaler which is provided with a curved section of a passage which creates a Venturi effect to empty a powder containing receptacle. A feed tube is positioned so that an inlet end of the tube enters the receptacle and a high velocity gas stream is released which creates a ‘low pressure region’ at the outlet end of the feed tube. This low pressure region that is created acts to draw fluidisation air into the receptacle, to fluidise and/or aerosolise the powder and extract the powder through the feed tube and into the high velocity gas stream. Although the device addresses the problem of more complete emptying of the powder receptacle by the utilisation of a walled passage which communicates and co-operates with a depression in the powder receptacle to create a Venturi effect, such a device may, inter alia, have limitations in efficiency of powder aerosolisation and may not address all previously mentioned problems of prior art devices.
In addition, one particular disadvantage of the Inhale device is its large size. The Inhale system generates a substantially laminar flow of, e.g. powder. Thus, in order to achieve the necessary deagglomeration, a large dose of high impact air must be delivered in order to achieve the magnitude of impact required for deagglomeration of the powder. Thus, the Inhale system suffers from the disadvantage that, inter alia, is cumbersome and does not readily lend itself to a portable delivery system.
International Patent application No. WO 01/87378 to Dura, describes a dry powder inhaler wherein a powder port extends into a dispersion tube. A small burst of compressed gas is released into the dispersion tube and expands, the rapidly moving and expanding gas disperses the powder and entrains the powder in the gas flow. However, the device suffers from the disadvantage that, inter alia, deagglomeration of the powder remains unsatisfactory.
U.S. Pat. No. 5,740,794—Inhale describes an inhalation apparatus which comprises, inter alia, a powder containing receptacle. A feed tube is positioned so that an inlet end of the tube enters the receptacle and a high pressure gas stream is released which creates a ‘low pressure region’ at the outlet end of the feed tube. Tis low pressure region acts to draw fluidisation air into the receptacle, to fluidise and extract the powder through the feed tube and into the high velocity gas stream.
However, there is no disclosure that the powder will undergo a circulatory trajectory on its way to the mouthpiece. Indeed, the disclosure, for example in FIG. 12 of Inhale describes a system wherein the powder is evacuated from the receptacle through a ‘central’ feed tube, no substantial circulatory motion being introduced.
Furthermore, the description refers to an “undisrupted” flow path for the powder, which would lead one to conclude that a “feed tube” which is central rather, than one which is peripheral, is desirable.
International Patent Application No. WO 00/45878—Fraunhofer describes a device which utilises a vacuum aerosolisation of a liquid/powder. However, it is notable, particularly from FIG. 2, that the powder/liposome travels through the central conduit with compressed air circulating around the outside of the conduit.
Thus there has long been a need for a powder delivery system which is capable of overcoming the aforementioned disadvantages. Attempts have been made to improve the respirable fraction of a powder (FPF) but these generally comprise the use of very low density particles. For example U.S. Pat. No. 6,254,854 describes the use of particles with a density of less than 0.4 g cm−3, whereas conventional particles in powders administered, e.g. by inhalation, may have a density of about 0.8 to 1 g cm3.
Thus, there is clearly a need for the development of a device suitable for the delivery of particles of any density, which provides low powder retention and provides a high respirable dose. For example, particles of conventional density, or low density particles as hereinbefore described, or even higher density particles.
We have now developed a powder delivery system which may comprise a number of high efficiency, controllable, elements and therefore overcomes or mitigates the disadvantages of the prior art. In particular the powder delivery system of the present invention overcomes the problem of MDIs by separation of the propellant volatile fluid and the powder. Furthermore, the powder delivery system of the invention overcomes the problems associated with prior art DPI devices and, inter alia, provides a greater efficiency of aerosolisation. It is therefore especially suited for use as a portable or hand held delivery device.
Thus according to a first feature of the invention we provide an air amplifying system comprising an amplify fluid jet provided with a fluid inlet and a fluid outlet, the fluid outlet being linked to an outlet nozzle via an amplifying passage, the amplifying passage also being linked to a powder chamber, said chamber being adapted for non-laminar powder flow, such that fluid travelling from the fluid outlet of the jet draws extraneous air and aerosolised powder through the powder chamber so that the extraneous air and aerosolised powder mix with the amplifying fluid in the amplifying passage and the amplified mixture exits through the outlet nozzle.
In particular, the ail amplifying system of the invention utilises an amplified fluid, e.g. gas, stream to disperse a powder. An unamplified gas stream can be created which is of sufficient velocity, for example by passing through an amplifying jet, so that, as it exits the jet and passes across an amplification passage, in the form of a first opening of a contiguous powder chamber or conduit, the gas stream creates a vacuum in the contiguous chamber or conduit.
The chamber or conduit can be provided with a powder reservoir or a powder metering member adjacent au inlet to the powder chamber, such that the vacuum created by the exit of the gas stream from the amplifying jet creates a vacuum in the powder chamber and an entrainment air flow through the powder.
This entrainment air flow is sufficient to cause deagglomeration and/or entrainment and then subsequent aerosolisation of the powder. One effect of the vacuum is to deagglomerate the powder without direct impingement of the gas stream on the powder. This may limit impaction of powder and hence retention of powder within the device which may be a problem with some prior art devices. Moreover, the gas stream can also be adapted to be deflected against a solid surface, the effect being the tendency of the flow to become attached to or flow around the solid surface. The exploitation of this effect, therefore enables a ‘shape’ to be given to the existing gas stream. One advantage of the system of the invention is that, inter alia, it provides a greater efficiency of deagglomeration and/or aerosolisation over prior art devices by the direction of the entrained air.
We have especially found that by influencing the shape of the gas stream to have a substantially non-laminar motion provides an improvement in the deagglomeration of the powder reflected in a significant improvement in respirable or fine particle fraction (FPF) of the delivered powder aerosol and a reduction in the powder retention within the device. Furthermore, Computational Fluid Dynamics (CAD) studies indicate significantly improved fluid dynamics.
In a particular preferred embodiment of the invention the powder chamber is adapted such that the aerosolised powder is deliberately subjected to a non-laminar flow. Preferentially, the non-laminar flow may be achieved by the use of an annular powder chamber. Thus, in particular, the air amplification system of the invention is provided with an annular powder chamber and an axial fluid jet.
Thus, in one embodiment of the invention the powder chamber may substantially form the body of the amplification system or be circumferential to the body of the device and the amplifying fluid jet may be axial to the body. In this particular embodiment the powder chamber may be a thin annular chamber. Preferably, the thin annular chamber may be created by bringing together male and female portions. Therefore, the outlet end of the fluid jet may comprise, or alternatively, may be fitted to, a frusto conical male member which fits into an outer portion of the powder chamber, e.g. in the form of a female member.
In this embodiment of the invention the separation between the male and female members may vary. Preferably, the separation between the male and female members which may be identified as the clearance may be from 100 to 5000 μm, preferably from 500 to 2000 μm. Most preferably, the clearance may be about 1000 μm.
Thus, the diameter of the jet may be from 100 to 500 μm, preferably from 200 to 300 μm, most preferably 250 μm. The diameter of the nozzle may vary, but may be from 100 to 1500 μm, preferably from 400 μm to 1200 μm especially from 400 μm to 600 μm, e.g. 500 μm.
In the air amplifying system of the invention the dimensions of the nozzle and jet may vary depending, inter alia, upon the nature of the powder to be delivered. However, importantly, the nozzle should possess a greater diameter than that of the diameter of the jet. This particular aspect of the invention is advantageous in that as the fluid, e.g. air, leaves the jet through the nozzle it expands creating a vacuum in the adjacent powder chamber. Thus, the ratio of the diameter of the jet to the diameter of the nozzle may vary, but may be in the range of from 1:8 to 1:2, preferably 1:4 to 1:2 and especially 1:2. Furthermore, in the air amplifying system of the invention the shape of the nozzle may be changed and/or multiple nozzles may be used to, inter alia, reduce oropharyngeal deposition. A particular advantage of the present invention is that, inter alia, the air amplifying system has the ability to “slow” the aerosol. Conventionally known inhalers require the use of, for example, a spacer tube to achieve this. Thus, the air amplifying system cam ‘slow’ the aerosol without the use of such a spacer tube.
The powder reservoir and/or metering member may be contiguous with the powder chamber. Alternatively, the powder chamber may be connected to the powder reservoir and/or metering member by one or more conduits.
The air amplifying system of the invention may be useful in a variety of situations. However, it is especially useful when incorporated in a powder delivery device.
Thus according to a second feature of the invention we provide a powder delivery device which comprises a delivery passage, a powder reservoir and/or a metering member adapted to present a measured dose of powder to the delivery passage characterised in that the powder delivery device is provided with an air amplification system as hereinbefore described.
In a particularly preferred embodiment of the invention, the air amplifying system creates an entrained air flow through the powder reservoir and/or metering member. Thus, the powder reservoir and/or metering member, may be positioned adjacent a powder inlet and the flow through the amplifying jet is sufficient to draw entrained air and powder through the inlet. The reservoir and the metering member may be separate, e.g. a bulk powder reservoir with a metering member. Alternatively the reservoir and metering member may comprise a single item, thus, for example, the device of the invention may be provided with one or a plurality of prefilled metering members.
It should be understood that the basis of this aspect of the present invention is the creation of a pressure differential across or through the powder reservoir and/or metering member which enables the deagglomeration of the powder to occur. Therefore, the creation of a pressure differential may generally comprise the creation of a vacuum. It is especially preferred that the entrained air will flow through the powder which is presented either direct from the reservoir or, preferentially from the metering member. Thus, preferably, the entrained air inlet will be positioned adjacent to a first side of the reservoir and/or metering member and the vacuum is created adjacent a second, opposite side of the reservoir and/or metering member. In a further embodiment, a further inlet tube may be provided which is adapted to introduce entrainment air, e.g. flushing air into the reservoir/metering member.
It is further preferred that the entrained air flow is sufficient to both deagglomerate and aerosolise the powder, although, as hereinbefore described, inter alia, improved deagglomeration can be achieved by the use of a non-laminar entrained air flow.
The air amplifying system of the invention may be used in conjunction with a variety of delivery devices. However, the powder delivery system is especially suited for use in the delivery of a powdered medicament. Such a system may be used for the delivery of an type of powdered medicament, but the system finds particular utility in the delivery of an inhaled medicament. Thus the system of the invention may be used as or in conjunction with an inhaler, e.g. a dry powder inhaler.
Thus according to a preferred aspect of the invention the powder delivery device of the invention may be an inhaler. We especially provide a, dry powder inhaler characterised in that it incorporates a powder delivery device as hereinbefore described.
In a further embodiment of the invention the amplification system may be provided with a plurality of nozzles and/or a plurality fluid jets. Such a plurality of nozzles and/or jets may increase the volume of powder which may be drawn the powder chamber. At the same time the total velocity of the fluid flowing through the jets and/or exiting through the nozzle. This is especially advantageous in the case of delivery of a powdered medicament, e.g. in an inhaler, since it enables a low velocity aerosolised powder cloud to be generated. In a yet further embodiment the fluid jet may comprise a plurality of interlocking jets. In such a case each jet may, optionally, be provided with one or more powder inlets. Furthermore, the system may be arranged to provide the separate, sequential or simultaneous operation of the jets to enable the creation of an aerosolised powder which coincides with, for example, the inspiration of a patient.
When the vacuum means comprises a Venturi-type system as hereinbefore described the pressurised fluid may be any fluid moving system. The fluid may be a liquid, however, preferentially, the fluid is a gas, for example, compressed air or a gas/vapour generated from the volatilisation of a volatile propellant, such as that delivered from a pressurised canister. Alternatively, the fluid flow may be generated by an electric motor, e.g. a battery operated motor, or by a manually primed piston, e.g. a hand pump.
When the vacuum means comprises the use of a volatilised propellant, any conventionally known pharmaceutically and/or environmentally acceptable propellants may be utilised. Such propellants include, but are not limited to, non-CFC propellants, such as a hydrofluoroalkane (HFA). Any conventionally known HFA propellant may be used, including those disclosed in, for example, EP0372777, WO91/04011, WO91/11173, WO91/11495 and WO91/14422. However, the most preferred HFA is a fluoroalkane such as a fluoromethane or a fluoroethane or a mixture of fluoroalkanes. Such fluoroalkanes include, but are not limited to, trichlorofluoromethane, dichlorodifluoromethane, 1,2-dichlorotetrafluorethane, trichlorotrifluoroethane and chloropentafluoroethane. One HFA which may be mentioned is HFA 134 (1,1,1,2-tetrafluoroethane) or HFA 227.
When the delivery device of the invention is utilised as or in conjunction with an inhaler, it is especially advantageous utilisation of entrained air not only deagglomerates the powder but also helps to facilitate aerosolisation of the powder.
When the powder delivery device comprises an inhaler, it may comprise a conventionally known inhaler with a system of the invention attached thereto. An example of a conventional inhaler is a CLICKHALER (available from Innovata Biomed in the UK and described in European Patent application No. 0 539 469) which is provided with an inhalation passage. The delivery device of the invention may optionally be attached, for example, at the outlet end of such an inhaler, to a spacer device.
In one embodiment, the metering member is adapted to transfer measured doses of powder from the powder reservoir to the delivery passage.
However, in an alternative embodiment, the powder may be presented to the delivery passage in a closed form, wherein it is opened in the delivery passage. Thus, the metering member may be a capsule, in which case the device may optionally be provided with means for piercing or rupturing the capsule.
In a yet further and preferred embodiment the powder may be presented to the delivery passage in an open form. Thus, for example, the metering member may be a spool carrying a powder, in which case the device may be provided with means for presenting the spool, in an open form into the delivery member.
Thus, the metering member may comprise a spool housed in a spool carrier. Such spools are generally described in the prior art. An example of such an inhaler system is a TECHNOHALER (available from Innovata Biomed in the UK and described in European Patent Application No. 0 626 689). Each spool has a flange at each end which form a tight slidable fit within the body of the spool carrier. The space left between the body of the spool and the spool carrier is filled with an appropriate powder. In an alternative embodiment the delivery device may be provided with a spool chamber, for example, in the form tube adjacent the delivery passage. In a preferred embodiment the spool chamber may form a snug fit around the spool and may therefore replace the spool carrier. The spool chamber may therefore optionally be fitted with an actuator member which may comprise a push rod mechanism.
The delivery device of the invention is advantageous in that, inter alia, it may operate by the administration of a cloud of powder. The device provides a dry powder delivery system which is independent of the rate of inspiration of a patient, and without the need for a patient to inhale undesirable propellants.
Furthermore, the inhaler of the invention is especially advantageous in that, inter alia, it may provide a significant increase in the respirable fraction of a delivered powder. As hereinbefore described, it is a particular aspect of the inhaler of the present invention that the inhaler may not require the use of a spacer, but still be able to “slow” the aerosol.
A variety of powders may be administered by using the inhaler of the invention. Such powders are generally drugs for the treatment of asthma, chronic obstructive pulmonary disease and respiratory infections. Such powders include, but are not limited to B2-agonists, e.g. fenoterol, formoterol, pirbuterol, reproterol, rimiterol, salbutamol, salmeterol and terbutaline; non-selective beta-stimulants such as isoprenaline; xanthine bronchodilators, e.g. theophylline, aminophylline and choline theophyllinate; anticholinergics, e.g. ipratropium bromide; mast cell stabilisers, e.g. sodium cromoglycate and ketotifen; bronchial anti-inflammatory agents, e.g. nedocromil sodium; and steroids, e.g. beclomethasone dipropionate, fluticasone, budesonide and flunisolide; and combinations thereof.
It is within the scope of this invention for two or more powders to be administered.
Specific combinations of powders which may be mentioned include combinations of steroids, such as, beclomethasone dipropionate, fluticasone, budesonide and flunisolide; and combinations of to β2-agonists, such as, formoterol and salmeterol. It is also within the scope of this invention to include combinations of one or more of the aforementioned steroids with one or more of the aforementioned β2-agonists.
Further powders which may be mentioned include systemically active materials, such as, proteinaceous compounds and/or macromolecules, for example, hormones and mediators, such as insulin, human growth hormone, leuprolide and alpha interferon; growth factors, anticoagulants, immunomodulators, cytokines and nucleic acids.
It is within the scope of this invention to include combinations of any of the aforementioned medicaments.
The particle size of the powder may be varied depending, inter alia, on the type of aerosol being formed. In the case of a dry powder medicament, the particle size of the powder, and the carrier, if one is present may be varied. The nature of the carrier may also be varied. Thus, the particle size of the powder may be substantially between 1 and 100 μm. That is, at least 90% w/w of the powder should have a particle size of between 1 and 100 μm. The preferred particle size may also depend upon the nature of the powder being delivered. Thus, for example, for the treatment of respiratory disorders a particle size of 4 to 8 μm may be preferred, e.g. 6 μm.
However, for the delivery of systematically active powders a smaller particle size may be desirable, for example from 1 to 5 μm, e.g. 2 μm.
In a dry powder formulation a variety of carriers may be used. Certain carriers may be mentioned, by way of example only, such as sugars, e.g. dextran, mannitol and lactose, for example α-lactose monohydrate. The particle size of the carrier may be across a wide range, between 0.1 and 500 μm, preferably between 1 and 200 μm. Alternatively, the carrier may itself comprise a mixture of fine and coarse particles.
According to a further feature of the invention we provide a method of administering a medicament which comprises the use of a powder delivery device as hereinbefore described.
As previously mentioned the powder delivery device of the invention is especially suited for use as a medicament delivery device, e.g. an inhaler. Therefore, we further provide a method of treatment of a patient with a respiratory disorder which comprises the administration of a powdered medicament using a device as hereinbefore described. In an especially preferred embodiment the method comprises administration of medicament by inhalation.
In a preferred embodiment we provide a method of treatment of a patient with a systemic disorder which comprises the administration of a medicament using an inhaler as hereinbefore described.
The device of the invention is especially suited for the efficient delivery of macromolecules, such as insulin. Thus, according to a particular feature of the invention we provide a method of treating insulin dependent diabetes which comprises administration of an effective amount of insulin using a device as hereinbefore described.
When the device of the invention is used for the delivery of macromolecules, such as insulin, it is important that they be provided in a moisture resistant system. Thus, according to the invention we provide a device as hereinbefore described provided with a moisture resistant coating e.g. a paraxylylene coating.
The device of the invention is advantageous un that, inter alia, a significantly increased respirable fraction is achieved. A conventional inhaler might be expected to deliver a respirable or fine particle fraction of, for example, 20-40%. However, the delivery device of the invention is able to provide an FPF of in excess of 70%.
The respirable fraction of a powder, known as FPF is generally a measurement of the percentage of a powder that reaches the lung of a patient as of function of the delivered dose. Respirable powder particles are considered to be about 6 μm (aerodynamic diameter) or less and therefore the FPF value of an aerosolised powder is a measure of the percentage of particles with the desired respirable size. A delivery device with a high FPF value is therefore desirable. Conventionally known DPI's provide an FPF of about 20-30% w/w.
One measure of the efficiency of a delivery device is the difference between the metered dose (MD) and the delivered dose (DD), conventionally this is known as the retention. Thus, a delivery device with low retention is desirable. Conventionally known DPI's provide a powder retention of approximately 10% w/w.
Conventionally know DPI's that provide a high FPF will provide a relatively high powder retention. Alternatively, those DPI's that provide a low powder retention may provide a relatively low FPF.
The delivery device of the invention is advantageous in that, inter alia, it provides a high APT and a low powder retention. The achievement of a combined high FPF and low retention in a dry powder inhaler is novel per se.
Thus, according to a further aspect of the invention we provide a powder delivery device characterised in that the delivery device provides a high FPF and low powder retention.
In a preferred aspect of the invention the delivery device of the invention is a dry powder inhaler.
Thus we especially provide a delivery device as hereinbefore described which comprises a substantially axial jet and a substantially annular deagglomeration chamber.
The dry powder inhaler may therefore provide an FPF of at least 70% w/w. Preferably, the dry powder inhaler of the invention may provide an FPF of at least 80% w/w, more preferably at least 90% w/w and most preferably at least 95% w/w. The dry powder inhaler of the invention may provide a powder retention of less than 10% w/w, preferably less than 0.5% w/w and most preferably less than 2% w/w.
According to a further aspect of the invention we provide a method of delivery of a powder with a high FPF and low powder retention as hereinbefore described which comprises the use of a delivery device comprising an air amplifier.
According to a further aspect, we provide a method of treatment of a patient suffering from a respiratory disorder which comprises the delivery of a medicament powder comprising a high FPF and low powder retention.