Dry powder inhaler

Abstract

The present invention provides a dry powder inhaler comprising one or more containers of powdered medication for inhalation; an outlet through which a user may inhale a dose of medication; and an airway comprising a cyclone chamber The cyclone chamber has a tangential powder inlet channel for supplying the powdered medication from at least one of the one or more dose containers; one or more tangential bypass inlet channels; and an axial exit opening connected to the outlet. When a user inhales on the outlet to create an air flow, medication is entrained in the air flow and flows through the airway via the cyclone chamber, and out through the outlet. The invention is characterized in that the airway comprises a grate between the dose container and the powder inlet channel that prevents large agglomerates of powder from entering the powder inlet channel.

Description

[0001] Dry powder inhaler

[0002] Technical Field of the invention

[0003] The present invention relates to a dry powder inhaler for oral or nasal delivery of medicament in powdered form.

[0004] Background to the invention

[0005] Dry powder inhalers (DPIs) are commonly used to deliver a pharmaceutically active ingredient to the lungs of a patient in order to treat local respiratory illnesses, such as asthma. There is also interest in using DPIs to deliver drugs systemically to the bloodstream via the lungs, for treating other medical conditions. In order to be effective, the powder must be aerosolized (e.g. from a blister or capsule) and deagglomerated so that the fine particles are dispersed into the air flow and transported to the user's lungs.

[0006] Some inhalers have a cyclone (vortex) chamber for deagglomerating the powder, for example WO 2024 / 196247. WO 2010 / 040779 discloses an inhaler which has a cyclone chamber of substantially circular cross-section, inlet and outlet ports at opposite ends of the chamber for the flow of drug laden air through the chamber between said ports and, a bypass air inlet for the flow of clean air into the chamber. The bypass air inlets are configured so that air entering the chamber through said inlet forms a cyclone in the chamber that interacts with the drug laden air flowing between the inlet and outlet ports. The aerosolized powder experiences increased shear forces and differential velocities as it flows through the chamber. This deagglomerates the particles, resulting in an increased fine particle fraction of the emitted dose. The outlet port of the cyclone chamber that leads to the mouthpiece has a grid through which the aerosolized powder passes. The grid can help to disperse the powder, as well as preventing any large fragments of e.g. a blister lid from entering the patient's mouth. The inhaler may also have a deagglomerating mesh with fine apertures (less than 0.5 mm in size) through which the drug-laden air flows at the inlet port to the cyclone chamber. However, this has the disadvantage that a fine mesh creates a significant additional air flow resistance, which means that, especially for patients with relatively weak inhalation capability, the flow rate through the inhaler is too low to evacuate all of the powder from its container. Moreover, the velocity in the cyclone chamber is reduced, resulting in less effective deagglomeration. Furthermore, a mesh with 0.5mm holes is too fine to be made by plastic moulding, so a metal mesh would be required, which adds cost and complexity.

[0007] Thus, there is a need for an inhaler that addresses these drawbacks, in particular that is capable of delivering a large volume of powder with a high fine particle dose that does not vary across a range of inhalation flow rates.

[0008] Brief Description of the invention

[0009] Powders that require large volumes for each dose and / or which are cohesive present particular challenges. Cohesive powders may contain relatively large lumps that may be reduced in size in the cyclone chamber, but not fully deagglomerated. As a result, the powder particles may be small enough to pass through the grid at the outlet of the cyclone chamber but are still too large to reach the patient's lungs. Particles that are greater than about 5pm in size are typically deposited in the patient's upper airways. In particular, relatively large particles are deposited in the patient's throat, which can cause the patient to cough. This can be unpleasant for the patient and may also result in the fine particles being coughed up so that the patient does not receive the expected fine particle dose.

[0010] It might be expected that the most effective dose would be achieved when most or all of the powder is evacuated from the dose container, so that it can be deagglomerated in the cyclone chamber. However, counterintuitively, the present inventors have found that selectively preventing the largest powder agglomerates from leaving the dose container so that they do not enter the cyclone chamber can actually increase the fine particle fraction that is delivered to the patient's lungs, as well as reducing the likelihood of the patient coughing.

[0011] Accordingly, the present invention provides a dry powder inhaler comprising:

[0012] • one or more dose containers containing powdered medication for inhalation;

[0013] • an outlet, such as a mouthpiece or nose piece, through which a user may inhale a dose of the medication; • an airway comprising a cyclone chamber, the cyclone chamber having:

[0014] • a tangential powder inlet channel for supplying the powdered medication from at least one of the one or more dose containers to the cyclone chamber;

[0015] • one or more tangential bypass (i.e. clean air) inlet channels; and

[0016] • an axial exit opening connected to the outlet; wherein, when a user inhales on the outlet to create an air flow, medication is entrained in the air flow and flows through the airway via the cyclone chamber, and out through the outlet, characterized in that the airway comprises a grate between the dose container and the powder inlet channel that prevents large agglomerates of powder from entering the powder inlet channel.

[0017] The grate comprises a number of generally parallel bars (as opposed to a grid or mesh which typically comprises two sets of bars arranged perpendicularly to each other). Whilst a grid formed of intersecting bars would perform the function of preventing large agglomerates of powder from entering the cyclone chamber, it would block a greater area of the flow path, and hence increase the air flow resistance of the inhaler more than a grate formed of parallel bars (with the same thickness and spacing). Nonetheless, the grate may have one or two cross bars arranged generally at right angles to the parallel bars, for example to strengthen the grate, provided that the openings between the bars are substantially larger (such as at least twice, preferably at least three times longer) in the direction of the parallel bars than in the direction of the cross bars. Preferably the grate does not have any cross bars since the cross bars increase the air flow resistance.

[0018] The grate may comprise a number of parallel bars that are spaced apart from each other, such as from 3 to 15 bars, or from 5 to 10 bars, for example, 6, 7, 8 or 9 bars.

[0019] The bars are suitably from 0.5 to 1.5mm in width, such as from 0.6 to 1.2mm or from 0.7 to 1mm, for example 0.75 to 0.9mm, such as about 0.8mm.

[0020] The spacing between the bars is suitably from about 0.5 to 1.5mm, such as from 0.8 to 1.2mm, for example 0.9 to 1.1mm, such as about 1mm. The bars are suitably from 0.5 to 3mm in height (i.e. parallel to the general direction of the air flow) such as from 1 to 2mm, such as about 1.5mm.

[0021] The bars may be of constant thickness (in the direction of the air flow), or they may be shaped. For example, they may be tapered, rounded or shaped as an aerofoil.

[0022] The bars may be arranged horizontally (i.e. perpendicular to the general direction of air flow). Alternatively, the bars may be inclined to the horizontal at an angle of from 5° to 45°, such as from 10° to 30° or from 15° to 20°, such as about 18°.

[0023] The dose container(s) may be blister(s), capsule(s) or a reservoir.

[0024] The inhaler may have a passage that connects the dose container to the powder inlet channel of the cyclone chamber via an entrance from the passage to the powder inlet channel. The grate may be located in the passage, preferably close to the dose container.

[0025] The grate may be a separate component that is inserted into the inhaler, in particular into the passage. Alternatively, the grate may be moulded integrally with the inhaler, in particular moulded inside the passage.

[0026] The term "tangential powder / bypass inlet channel" means that the channel directs the air flow in a substantially tangential direction into the cyclone chamber. Thus, the inlet channels are preferably tangential to the cyclone chamber, but they do not have to be exactly tangential.

[0027] Preferably the cyclone chamber has no other inlets, such as axial clean air inlets situated in the base of the cyclone chamber.

[0028] Brief Description of the Figures

[0029] Figure 1 shows an embodiment of an inhaler according to the invention. Figures 2 shows the inhaler of Figure 1 removed from its cover.

[0030] Figure 3A is an expanded view showing the components of the inhaler of Figure 1.

[0031] Figure 3B shows a cross-section through the inhaler of Figure 1.

[0032] Figure 4 shows one embodiment of the central part of the inhaler with a grate.

[0033] Figure 5 shows a first embodiment of a grate located upstream of the cyclone chamber according to the invention.

[0034] Figure 6 shows a second embodiment of a grate located upstream of the cyclone chamber according to the invention.

[0035] Detailed Description of the invention

[0036] Figure 1 shows an inhaler according to the invention. The inhaler 1 has a housing 3 and a mouthpiece 4. A cover 2 holds and protects the inhaler. In particular, the cover has an extension 7 that extends over the mouthpiece 4, thereby preventing foreign material from entering the mouthpiece before use. The inhaler has a pair of grips 5 located on either side of the housing, and the cover has a pair of grips 6, for removing the inhaler from the cover.

[0037] To prepare the inhaler for use, the user holds the grips 5 of the housing 3 between the finger and thumb of one hand, and the grips 6 on the cover 2 between the finger and thumb of their other hand. The inhaler 1 is pulled out of the cover which uncovers the mouthpiece as shown in Figure 2. This action also causes a blister containing the medication to be pierced, thereby avoiding the need for any further user steps (such as pressing a button or lever to cause piercing) before use. The user then inhales on the mouthpiece to receive the medication.

[0038] Figure 3A is an expanded view of the components of the inhaler 1. Figure 3B shows a crosssection through the inhaler. The inhaler has an upper housing part 10 with the mouthpiece 4, a central part 30, a mixing element 35, a blister 40 and a lower housing part 20. The central part 30 has two pairs of piercing elements 31 (for example of the type described in WO 2014 / 114916) on its lower surface.

[0039] The central part 30 is fixed (e.g. clipped or welded) in the upper housing part 10 so that the internal surface of the upper housing part and the upper surface of the central part together define an airway that fluidically connects the blister 40 (once it has been pierced) to the mouthpiece 4 via a passage 32 and a cyclone (deagglomeration) chamber 33. The passage 32 contains a grate 34 whose function is explained below. The mixing element 35 is located inside the cyclone chamber 33. An exit opening 11 with a grid 12 is formed in the upper housing part; this connects the cyclone chamber to the mouthpiece 4.

[0040] The blister 40 has a lid 41 and a base 42 with a rim 43 which fits into slots 21 on either side of the lower housing part 20, thereby holding the blister in place.

[0041] The upper 10 and lower 20 housing parts are movable relative to each other. When the inhaler is in the cover 2, the upper and lower housing parts are held in an initial position in which the piercing elements 31 are held spaced apart from the lid 41 of the blister 40. The cover prevents the upper and lower housing parts from accidentally being pushed together before use. When the inhaler is removed from the cover, the cover interacts with the upper and lower housing parts, so that they are pushed together into an actuated position, in which the piercing elements 31 pierce the lid and enter the blister. The mechanism for this consists of a pair of cams 8 in the form of pegs on the inside of the cover and two sloping cam surfaces 22, one in each side of the lower housing part 20. As the inhaler 1 is removed from the cover 2, the cams 8 slide along the cam surfaces 22, pushing the lower housing part 20 upwards into the upper housing part 10. One pair of piercing elements 31 creates an air entry hole in the lid 41 of the blister 40, and the other pair creates a powder exit hole. In the actuated position, the blister is located directly below (in the orientation shown in Figure 3B) the passage 32, while there is a small gap between the base of the cyclone chamber and the lid, which allows air to flow into the air entry hole.

[0042] Figure 4 shows the central part 30 from above. The grate is formed by seven parallel bars 34a that span the width of the passage. The grate prevents agglomerates of powder that are larger than the spacing between the bars from entering the cyclone chamber. The bars also break up large agglomerates of powder by impaction, as well as making the air flow into the cyclone chamber more laminar and reducing turbulence. The embodiment shown in Figure 4 is one example of a grate; however, the grate may comprise any suitable number of spaced apart parallel bars, such as from 3 to 15 bars, or from 5 to 10 bars, for example, 6, 7, 8 or 9 bars. The bars are suitably from about 0.5 to 1.5mm in width, such as from 0.6 to 1.2mm or from 0.7 to 1mm, for example 0.75 to 0.9mm, such as about 0.8mm. The spacing between the bars is suitably from about 0.5 to 1.5mm, such as from 0.8 to 1.2mm, for example 0.9 to 1.1mm, such as about 1mm. The bars are suitably from 0.5 to 3mm in height (i.e. parallel to the general direction of the air flow) such as from 1 to 2mm, for example about 1.5mm. The bars may be arranged horizontally (i.e. perpendicular to the general direction of air flow). Alternatively, the bars may be inclined to the horizontal at an angle of from 5° to 45°, such as from 10° to 30° or from 15° to 20°, such as about 18°. The bars may be of constant thickness (in the direction of the air flow), or they may be shaped. For example, they may be tapered, rounded or shaped as an aerofoil.

[0043] The width, spacing, height, shape and inclination of the bars spacing may be selected to optimise the performance of the inhaler for different powders, thereby preventing lumps of powder above a certain size from entering the cyclone chamber. The number of bars may be chosen according to the dimensions of the inhaler, in particular the passage.

[0044] Figure 5 is a cross-sectional view of the central part from the side. The bars 34a of the grate are arranged horizontally within the passage (i.e. perpendicular to the general direction of air flow). Figure 6 shows an alternative configuration in which the bars 34a of the grate are inclined to the horizontal. The inclined bars are thought to encourage trapped agglomerates to move up the incline, and hence to the edge of the passage so that they obstruct the flow less. The grates shown in Figures 5 and 6 are separate components that are designed to be inserted into the passage 32 of the central part 30. Consequently, they have legs 34b for locating and holding the grate in the correct position in the passage. However, the grate could alternatively be moulded integrally with the central part.

[0045] Once the inhaler has been removed from the cover, the user inhales on the mouthpiece 4. This creates an air flow into the blister through the air entry hole which aerosolizes the powder, and then carries it out through the powder exit hole through the grate 34 and into the passage 32. The powder-containing air then flows through a powder inlet channel 36 into the cyclone chamber 33. External clean (i.e. powder-free) air also enters the cyclone chamber through two bypass inlet channels 37, 38. The powder inlet channel 36 and the bypass inlet channels 37, 38 are located 120° apart from each other and are tangential to the wall of the cyclone chamber, so that the air flow into the chamber creates a vortex. The entrance to the powder inlet channel 36 is located generally towards, but not exactly at, the centre of the passage 32 (at about one third of the width of the passage). The vortexed air flow, in combination with the mixing element 35 (not shown in Figures 4, 5 and 6) which is freely movable within the cyclone chamber, breaks the powder up into fine particles.

[0046] The diameter of the mixing element is larger than the widths of the powder inlet channel 36 and the bypass inlet channels 37, 38 at the points where they enter the cyclone chamber, so that the mixing element cannot enter the inlet channels. The height of the cyclone chamber is relatively short, and is less than its diameter. The cyclone chamber must be tall enough that the mixing element can move freely. However, if the cyclone chamber were relatively tall (compared to the diameter of the mixing element), the mixing element would mostly move around the upper part of the cyclone chamber. Consequently, it would not be very effective at dislodging powder from the lower part of the cyclone chamber.

[0047] The aerosolized fine powder then leaves the cyclone chamber 33 via the grid 12 at the exit opening 11 and flows out through the mouthpiece 4 to the user's lungs. The grid 12 prevents any large lumps of powder from leaving the cyclone chamber. The grid 12 also reduces the vorticity of the air. Without this rectification of the air flow, the powder would spread outwards after it leaves the inhaler, resulting in deposition in the user's mouth and throat.

[0048] The inhaler described above has a blister that contains the powdered medication, which is pierced by the piercing elements. However, the invention also encompasses other containers, such as capsules, and other opening mechanisms, such as peeling a lid off, pulling two halves of a capsule apart or piercing a capsule by means of needles. Regardless of which type of opening mechanism is used, the inhaler may be automatically actuated by the action of removing it from the cover. The inhaler may have a single dose of medication and may be pre-loaded with a blister or capsule. The inhaler may be re-usable, so that a new blister or capsule in inserted each time it is to be used. Alternatively, the inhaler may be a multi-dose device and contain a number of doses, for example 30 or 60 doses in a blister strip, dose disk or a reservoir, along with a suitable mechanism for preparing each dose so that the respective dose container communicates with the powder inlet channel.

[0049] The dry powder medication for inhalation comprises a pharmaceutically active ingredient and may also comprise one or more pharmaceutically acceptable excipients. The excipient may be present in relatively small amounts, so that the powder may comprise at least 50%, at least 70%, at least 90% or more of the active ingredient. The amount of the powdered medication in the blister or capsule may be 5-300 mg, preferably 20-200 mg, more preferably 30-150 mg, even more preferably 40-100 mg. For example, there may be about 50, 60, 70, 80 or 90 mg of powder in the blister or capsule.

[0050] Each dose may be delivered from the inhaler in a single inhalation or in two or more inhalations. The width of the inlet channels, in particular the powder inlet channel, can be chosen to achieve a desired rate of flow of powder from the blister. Thus, the inlet channels can be narrower if the dose is intended to be delivered over two inhalations instead of one inhalation.

[0051] The medication may be capable of treating or preventing a thromboembolic event. The pharmaceutically active ingredient in the medication may be an antiplatelet drug. For example, the pharmaceutically active ingredient may be a non-steroidal anti-inflammatory drug (NSAID). Preferably, the pharmaceutically active ingredient is a salicylate (a salt or ester of salicylic acid), most preferably acetylsalicylic acid or a pharmaceutically acceptable salt thereof. The pharmaceutically active ingredient may be another type of NSAID. For example, the pharmaceutically active ingredient may be Celecoxib (Celebrex), Dexdetoprofen (Keral), Diclofenac (Voltaren, Cataflam, Voltaren-XR), Diflunisal (Dolobid), Etodolac (Lodine, Lodine XL), Etoricoxib (Algix), Fenoprofen (Fenopron, Nalfron), Firocoxib (Equioxx, Previcox), Flurbiprofen (Urbifen, Ansaid, Flurwood, Proben), Ibuprofen (Advil, Brufen, Motrin, Nurofen, Medipren, Nuprin), Indomethacin (Indocin, Indocin SR, Indocin IV), Ketoprofen (Actron, Orudis, Oruvail, Ketoflam), Ketorolac (Toradol, Sprix, Toradol IV / IM, Toradol IM), Licofelone (under development), Lomoxicam (Xefo), Loxoprofen (Loxonin, Loxomac, OxOrjo), Lumiracoxib (Prexige), Meclofenamic acid (Meclomen), Mefenamic acid (Ponstel), Meloxicam (Movalis, Mel ox, Recoxa, Mobic), Nabumetone (Relafen), Naproxen (Aleve, Anaprox, Midol Extended Relief, Naprosyn, Naprelan), Nimesulide (Sulide, Nimalox, Mesulid), Oxaporozin (Daypro, Dayrun, Duraprox), Parecoxib (Dynastat), Piroxicam (Feldene), Rofecoxib (Vioxx, Ceoxx, Ceeoxx), Salsalate (Mono-Gesic, Salflex, Disalcid, Salsitab), Sulindac (Clinoril), Tenoxicam (Mobi flex), Tolfenamic acid (Clotam Rapid, Tufnil), or Valdecoxib (Bextra). The pharmaceutically active ingredient may be an alternative to an NSAID. Such alternatives include P2Y12 inhibitors. Examples of P2Y12 inhibitors include Plavix (clopidogrel), ticlopidine, ticagrelor, prasugrel, and cangrelor. Other pharmaceutically active ingredients may include COX-2 inhibitors, and Nattokinase (an enzyme (EC 3.4.21.62, extracted and purified from a Japanese food called natto). The medication may comprise both acetylsalicylic acid, or a pharmaceutically acceptable salt thereof, and a P2Y12 inhibitor.

[0052] The pharmaceutically active ingredient may alternatively be a bronchodilator, such as a beta- 2 agonist or anticholinergic for the treatment of an asthma exacerbation; adrenaline and / or atropine for the treatment of cardiac failure, cardiac dysfunction, cardiac arrest, anaphylaxis, drug overdose or the like; glucose and / or glucagon for the treatment of hypoglycaemia, diabetes induced coma or the like; benzodiazepine, phenytoin or anti-seizure medications for the treatment of seizure; di hydroergotamine for the treatment of migraine; naloxone for treating an opioid overdose; insulin for managing blood sugar level or the like.

[0053] The medication may include one or more agents for inducing an immune response, e.g. a vaccine, such as a measles vaccine, a Hepatitis B vaccine, or an influenza vaccine.

[0054] The medication may include a natural or synthetic cannabinoid, such as Cannabidiol (CBD) or Tetrahydrocannabinol (THC). Examples

[0055] Example 1

[0056] The air flow resistances of five variants of an inhaler with a cyclone chamber were measured. The first inhaler had no grate, so that the passage between the blister and the powder inlet to the cyclone chamber was open. The second inhaler had a grate according to the invention consisting of seven thin horizontal bars, with a width of 0.8mm and a spacing of 1mm, as shown in Figure 5. The third inhaler had another grate according to the invention consisting of seven sloping bars, with a width of 0.8mm and a spacing of 1mm, inclined at 18° to the horizontal as shown in Figure 6. In the fourth and fifth inhalers, the grates were replaced with fine meshes, similar to the deagglomeration meshes disclosed in WO 2010 / 040779. The mesh in the fourth inhaler had 40 holes per linear inch (LPI). It was made from 0.22mm thick metal wires and had apertures 0.42mm in size. The mesh in the fifth inhaler had 70 holes per linear inch and was made from 0.14mm thick metal wires with apertures 0.22mm in size. The inhalers were identical apart from the grates / meshes. The cyclone chambers were 17.5mm in diameter and had a central (axial) circular exit opening to the mouthpiece 10mm in diameter, with one powder inlet channel and two bypass inlet channels. The exit opening contained a grid formed from circular rings with a spacing of 0.85mm and radial ribs, as described in our co-pending application PCT / EP2025 / 065843. Each cyclone chamber contained a mixing element in the form of three orthogonal circular discs with diameter of 6mm and a common centre, as shown in Figures 3A and 3B and described in our co-pending application PCT / EP2025 / 065842.

[0057] The air flow resistance each inhaler was determined by applying pressure drops of lkPa (representing a relatively weak inhalation) and 4kPa (representing a relatively strong inhalation) and measuring the resulting flow rates. For a given pressure drop, a higher flow rate indicates a lower air flow resistance. The results are shown in Table 1.

[0058] Table 1: Air flow resistance results

[0059] The flow rates for both fine meshes were lower than those with the grates at both pressure drops. This is expected, because the smaller apertures in the fine mesh obstruct the air flow more than the large gaps between the bars in the grates. A lower air flow resistance is advantageous because it results in a greater flow rate for a given inhalation strength (i.e. pressure drop), which in turn results in higher particle velocities inside the cyclone chamber, and hence better deagglomeration.

[0060] The flow rates for the grate with the horizontal bars were very similar to those of the inhaler with no grate. The flow rates for the grate with the inclined bars were somewhat higher than those of the inhaler with no grate. It might be expected that the presence of the bars would obstruct the air flow (albeit to a significantly lesser degree than the fine meshes). However, without wishing to be limited by theory, it is believed that the bars make the flow into the cyclone chamber more laminar, which reduces the airflow resistance. The inclined bars cause less restriction of the air flow than the horizontal ones, because only part of the flow is obstructed at any given point within the grate (so, for example, at the lower end of the grate, only the flow on one side of the passage is obstructed by the presence of the bars). For the horizontal bars, it appears that the two effects (more laminar flow, but additional obstruction) approximately cancel each other out, so that the overall airflow resistance of the inhaler is very close to that of the inhaler with no grate. Example 2

[0061] Blisters were filled with lOOmg of a powder consisting of micronized acetylsalicylic acid powder (99.5% ASA) and magnesium stearate (0.5% MgSt) and placed into each of the inhalers described in Example 1.

[0062] A Fast Screening Impactor (FSI, Copley Scientific) was used to measure the Fine Particle Dose (< 5pm) and Fine Particle Fraction (< 5pm) delivered from each inhaler. The FSI has a filter which captures emitted aerosol particles of less than 5pm in size. Simulated inhalation manoeuvres were performed on each inhaler. The manoeuvres consisted of two inhalations each inhalation having a volume of 2 litres at a fixed pressure drop. Two different pressure drops were used, lkPa (representing a relatively weak inhalation) and 4kPa (representing a relatively strong inhalation). The Fine Particle Dose (FPD) was determined gravimetrically by weighing the filter before and after each manoeuvre (i.e. after each pair of inhalations). The Fine Particle Fraction (FPF) was calculated as the percentage of fine particles in the total mass of powder emitted from the inhaler during the inhalation manoeuvre. The results (the mean value from three separate measurements in each case) are shown in Table 2.

[0063] Table 2: FSI results

[0064] The results show that the grates with horizontal and inclined bars and both meshes resulted in significant increases in the FPF compared to the inhaler with no grate / mesh, at both pressure drops. This demonstrates that the grates and meshes are effective at preventing large agglomerates of powder from leaving the inhaler (by trapping them and / or helping to break them up). As a result, the amount of powder deposited in the patient's throat is reduced. At the higher pressure drop, the grates and meshes also resulted in a significant increase in the FPD. This is believed to be because impaction of large agglomerates onto the bars / mesh additionally results in some deagglomeration.

[0065] At the low pressure drop, the results show an increased FPD for the inclined bars and the coarser mesh, i.e. the same effect as at the higher pressure drop. However, the finer mesh resulted in a substantial decrease in the FPD. This may be because the lower pressure drop results in less deagglomeration by impaction on the mesh, so that the fine mesh filters out a larger proportion of the agglomerates. There was also a small decrease in FPD for the horizontal bars, but this was too small for any conclusion to be drawn.

[0066] In summary, both the grates and the meshes were effective at removing the largest agglomerates. Thus, patients are much less likely to cough due to the low throat deposition, whilst still receiving a similar, or in some cases, a somewhat larger fine particle dose. The grates have the advantage over the meshes that they can be produced by moulding, so do not require a separate component made from a different material from the rest of the inhaler, thus reducing cost and complexity.

[0067] The grate with the inclined bars gave the best overall performance. Firstly, it resulted in an acceptable FPD at the low flow rate. Secondly, the difference between the FPDs at the low and high flow rates was smaller than with the other grate and with the meshes. In other words, the FPD was less dependent on the flow rate, so that the dose that the patient receives is less dependent on the strength of their inhalation. Thirdly, the air flow resistance was reduced.

Claims

1. Claims1. A dry powder inhaler comprising:• one or more dose containers containing powdered medication for inhalation;• an outlet through which a user may inhale a dose of medication;• an airway comprising a cyclone chamber, the cyclone chamber having:• a tangential powder inlet channel for supplying the powdered medication from at least one of the one or more dose containers to the cyclone chamber;• one or more tangential bypass inlet channels; and• an axial exit opening connected to the outlet; wherein, when a user inhales on the outlet to create an air flow, medication is entrained in the air flow and flows through the airway via the cyclone chamber, and out through the outlet, characterized in that the airway comprises a grate between the dose container and the powder inlet channel that prevents large agglomerates of powder from entering the powder inlet channel.

2. A dry powder inhaler according to claim 1, wherein the grate comprises from 3 to 15 generally parallel bars.

3. A dry powder inhaler according to claim 2, wherein the grate does not have any cross bars that are generally perpendicular to the parallel bars.

4. A dry powder inhaler according to claim 2 or claim 3, wherein the bars are from 0.5 to 1.5mm in width.

5. A dry powder inhaler according to any of claims 2 to 4, wherein the spacing between the bars is from 0.5 to 1.5mm.

6. A dry powder inhaler according to any of claims 2 to 5, wherein the bars are from 0.5 to 3mm in height.

7. A dry powder inhaler according to any of claims 2 to 6, wherein the bars are of constant thickness.

8. A dry powder inhaler according to any of claims 2 to 6, wherein the bars are tapered, rounded or shaped as an aerofoil.

9. A dry powder inhaler according to any of claims 2 to 8, wherein the bars are arranged horizontally, i.e. perpendicular to the general direction of air flow.

10. A dry powder inhaler according to any of claims 2 to 8, wherein the bars are inclined to the horizontal at an angle of from 5° to 45°, such as from 10° to 30° or from 15° to 20°.

11. A dry powder inhaler according to any of claims 1 to 10, wherein the dose container is a blister, capsule or reservoir.

12. A dry powder inhaler according to any of claims 1 to 11, further comprising a passage that connects the dose container to the powder inlet channel.

13. A dry powder inhaler according to claim 12, wherein the grate is located in the passage, preferably close to the dose container.

14. A dry powder inhaler according to claim 13, wherein the grate is a separate component that is inserted into the passage.

15. A dry powder inhaler according to claim 13, wherein the grate is moulded integrally in the passage.

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