Abstract:
An inhaler for use by an individual to inhale a particulate medicament from a reservoir comprises a chamber having a first end connectable to the reservoir to be in air flow communication therewith, a second end for delivering the medicament to the individual upon inhalation and a conduit defining an air flow path extending between the first end and the second end; and, an orifice in the chamber between the first end and the second end, the orifice utilizing the Coanda Effect when the reservoir is in air flow communication with the chamber and upon inhalation by the individual to draw medicament from the reservoir into the air flow path.

Description:
FIELD OF THE INVENTION 
     This invention relates to inhalers for powders and other fluids such as a volatile liquid or a gel and more particularly to hand held inhalers for use without medical assistance. 
     BACKGROUND OF THE INVENTION 
     The medical community and society in general have been concerned with reducing the hazardous effects of cigarette smoking for many years. The chemicals contained in cigarette smoke produce unwanted effects, including unpleasant odours and health hazards for smokers and bystanders breathing the smoke. 
     Of the various chemicals contained in cigarette smoke, nicotine is primarily responsible for the pleasurable effects of smoking. Nicotine replacement devices, such as chewing gums or patches, allow a smoker to obtain doses of nicotine without inhaling the other hazardous chemicals in cigarette smoke and without creating smoke that is hazardous to bystanders. Accordingly, nicotine replacement devices may be useful in programs to reduce or eliminate the smokers&#39; dependency on smoking. 
     Inhaling nicotine as a powder is an effective way to deliver nicotine to the bloodstream. The inhaled powder is deposited on the inner surfaces of the lungs and absorbed into the bloodstream. However, in addition to their desire for nicotine, smokers are also accustomed to the process of smoking. This process includes one or more of the following: handling the cigarettes, tapping the cigarettes against a hard surface before smoking, tapping the cigarette between inhalations to remove ashes and discarding the cigarette when done. Further, smokers are accustomed to inhaling on the cigarette several times to withdraw the nicotine. 
     Although hand held inhalers, including hand held powder inhalers, for use by a patient without medical assistance currently exist, they have various undesirable features. For example, many devices are designed for medical conditions where a patient requires immediate delivery of a medicament. These devices deliver the medicament in one or, at most, a small number of inhalations. These devices are not suitable for medicaments that are preferably delivered over several inhalations. Further, these devices rely on air currents that flow directly through or across the medicament which causes some of the medicament to travel at high speed and impact the user&#39;s airway rather than enter the user&#39;s lungs. 
     Other existing devices rely on complicated or awkward mechanisms for their use. For example, propellers may be used to rotate a capsule to expel powder by centrifugal force, or various rotating or sliding mechanisms may be used to deposit discrete amounts of powder into the airflow path of an inhaler. These devices are complicated and difficult to use discretely. Similarly, many devices require a person to manually insert a medicament container, such as a capsule of powder, into the device in a manner that breaks the container open, again making it difficult to use the device discretely or conveniently. The expense and size of these devices requires them to be reused whereas it would be more convenient and hygienic to make them disposable. 
     One inhaler of note is Priestly (U.S. Pat. No. 2,587,215). Priestly discloses a device which uses a sliding mechanism to deliver small portions of powder from a remote reservoir to a chamber. The primary airflow enters this chamber and flows through or across the powder. A downstream air inlet provides a secondary airflow that mixes with the primary airflow coming from the chamber to diffuse the powder mixture. To use the device, a person would need to first insert a capsule into the device, and then manipulate the sliding mechanism to put a portion of powder in the chamber for inhalation. 
     Another inhaler of note is Cavazza (U.S. Pat. No. 4,338,931). Cavazza discloses a device which has two pre-assembled telescoping components which contain a capsule of powder. Each of the two components has a hollow open ended spike which pierces the capsule when the two components are slid together. Air flows into the first spike, through the capsule and through the second spike to a mouthpiece. The device is compact and easily used, but the direct airflow through the powder would deliver most of the powder at high speed in a single inhalation. 
     Inhalers which comprise a hollow longitudinally extending member are known. For example, Rose et al (U.S. Pat. No. 5,441,060) discloses a hollow cylindrical member wherein the medicament is stored in a thin annular band or in a porous member. According to this patent, air passing longitudinally through the inhaler entrains the medicament. Slutsky et al. (application No. PCT/CA95/0056) also discloses such an inhaler wherein air passing longitudinally through the inhaler entrains the medicament. In these devices, the air passing through the inhaler contacts the medicament as the air travels directly through the inhaler. 
     SUMMARY OF THE PRESENT INVENTION 
     In accordance with one embodiment of this invention, there is provided an inhaler for use by an individual to inhale a medicament from a reservoir comprising: 
     (a) a chamber having a first end connectable to the reservoir to be in air flow communication therewith, a second end for delivering the medicament to the individual upon inhalation and a conduit defining an air flow path extending between the first end and the second end; and, 
     (b) an orifice in the chamber between the first end and the second end, the orifice utilizing the Coanda Effect when the reservoir is in air flow communication with the chamber and upon inhalation by the individual to draw medicament from the reservoir into the air flow path. 
     In accordance with another embodiment of this invention there is provided an inhaler for use by an individual to inhale a medicament from a reservoir comprising: 
     (a) a chamber having a first end connectable to the reservoir to be in air flow communication therewith, a second end for delivering the medicament to the individual upon inhalation and a conduit defining an air flow path extending between the first end and the second end; 
     (b) the conduit including a first portion adjacent the first end, the first portion having an upstream end adjacent the first end and an opposed downstream end, the cross sectional surface area of the first portion decreasing from the downstream end of the first portion to the upstream end of the first portion; and, 
     (c) an orifice positioned between the first end and the second end for introducing undirected air into the chamber upon inhalation by the individual. 
     The orifice may be positioned in the chamber adjacent the first portion. Alternately, the orifice may be positioned in the first portion. The cross sectional area preferably decreases continuously from the downstream end of the first portion to the upstream end of the first portion. More preferably, the first portion is frusto-conical in shape. 
     The inhaler may include a seal between the first end and the reservoir when the reservoir is connected to the inhaler, and rupturable by relative movement between the reservoir and the first end. 
     The inhaler may include a connector which connects the reservoir and the first end of the chamber together when the inhaler is used such that the interior of the reservoir is open to the first end of the chamber but otherwise the reservoir substantially seals the first end of the chamber. The connector may comprise a second portion of the inhaler slidably engaged in relation to the chamber between a first position and a second position, the interior of the reservoir being open to the first end of the chamber in the second position. Alternately, the reservoir may be releasably sealed in the first position and openable by the first end of the reservoir as the second portion is moved from the first position to the second position. In a more preferred embodiment, the reservoir is formed of a folded strip of material sealed at its edges between a closed end and an openable end, the openable end being releasably sealed. 
     In one embodiment the inhaler resembles a cigarette, the reservoir contains a nicotine formulation and the orifice is located so that the nicotine formulation is withdrawn over a number of inhalations to approximate the nicotine delivery of smoking a cigarette. 
     In another embodiment, the inhaler further comprises at least one by pass air passage so that the orifice supplies the primary air of inhalation and the by pass passage supplies supplemental air to the reservoir. Preferably, the by pass air passage directs air at the medicament in the reservoir to assist the primary air to remove the medicament from the reservoir. 
     One advantage of the instant invention is that it provides an inhaler suitable for delivering a dosage of a medicament, preferably a particulate or a powdered medicament, over several inhalations and therefore better simulates the action of smoking. A further advantage is that the inhaler is uncomplicated and simple to use. 
     One aspect of the present invention involves a device comprising a chamber of increasing cross sectional area. The larger end is connected to a mouthpiece and, in use, the smaller end is open to a reservoir of a medicament to be inhaled. An orifice is preferably provided in the wall of the chamber near but preferably not at the reservoir. It has been found that on inhalation through such a device, air enters the orifice in the chamber and flows to the mouthpiece. There is no primary airflow through or across the medicament (i.e. as the air does passes through the inhaler from the air entry port to the air exit port, it does not travel in a continuous route so as to entrain the medicament). Instead, a portion of the air that enters through the orifice (eg. about half) moves in a direction opposed to the air exit port of the inhaler as it travels towards the reservoir where it entrains a portion of the medicament. The air with the entrained medicament then doubles back to travel to the air exit port of the inhaler. Over several inhalations, all of the medicament may be inhaled. 
     Another aspect of the present invention involves the manner in which the reservoir of medicament is attached to the device, including the chamber. In one embodiment, the reservoir is formed of a strip of material, folded over and sealed partway along the edges to create a reservoir. The open end of the reservoir may be temporarily sealed to create a cone that fits over the smaller end of the chamber. The loose ends of the strip of material are attached to a second portion of the device that slides relative to the chamber and mouthpiece. The reservoir may be opened simply by sliding the second portion towards the chamber causing the chamber to open the temporary seal and be inserted into the reservoir. It has been found that such a device is easy to use and may be economically produced. 
     When smokers attempt to stop smoking the recidivism rate is high due to the negative symptoms of withdrawal from nicotine addiction. Replacement therapy with cigarette substitutes is designed to lessen the impact of nicotine withdrawal and to assist a person in withdrawing from cigarette induced nicotine dependency. Cigarette substitutes are suggested as a replacement for cigarettes during the withdrawal period. 
     Another aspect of the invention is that it can be used to inhale nicotine medicament and preferably a particulate or a powdered nicotine formulation, in a manner similar to smoking a cigarette, cigar or the like. For example, the device may be made of a similar size and appearance as a cigarette. Further, it may be constructed to feel like a cigarette (i.e. it may have a soft feel). 
     An advantage of the instant invention is that the inhaler may be constructed so as to it may be handled like a cigarette. For example, the inhaler may be constructed so that the nicotine may be delivered over about the same number of inhalations as are required to smoke a cigarette. Thus, the reservoir may contain a single dose of medicament which is equal to the nicotine present in a single cigarette. Further, tapping the device between inhalations may be used to disturb the nicotine powder in the reservoir and enhance the feel of smoking. In particular, multiple inhalations may be required to inhale all of the medicament in the reservoir and it may be tapped between inhalations, as a smoker would tap a cigarette to get rid of ash from the burning end of a cigarette, to loosen some of the medicament in the reservoir so that it will be entrained in the subsequent inhalation. 
     Such a device may be used as part or all of a smoking cessation or smoking replacement therapy to reduce or eliminate the use of cigarettes, cigars, pipes and the like by an individual. Successful withdrawal from smoking may require the use of the inhaler of the instant invention over a period of time during which inhalers are used to deliver successively smaller nicotine doses until complete withdrawal may be effected. In some cases, such as when a person is unable or unwilling to stop smoking, an inhaler of the instant invention may be used as a permanent tobacco replacement. 
     In one embodiment a series of inhalers, each having a predetermined dose of a nicotine formulation, are used. Each inhaler is used at time intervals sufficient to reduce the negative effects of nicotine withdrawal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, which show a preferred embodiment of the present invention and in which: 
     FIG. 1 is a partially sectioned isometric view of the present invention in a first position; 
     FIG. 2 is a partially sectioned isometric view of the resent invention in a second position; 
     FIG. 3 is a sectional view of a portion of the invention along line III—III in FIG. 2; 
     FIG. 4 is an end view in the direction of Arrow A in FIG. 1; 
     FIG. 5 is an end view in the direction of Arrow B in FIG. 1; and, 
     FIG. 6 is a cross-section along the line  6 — 6  in FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     FIGS. 1 and 2 show the inhaler  10  which comprises a first portion  12  and a second portion  14 . First portion  12  includes, and may consist of, a chamber  21  positioned at its upstream end. 
     Generally, first and second portions  12  and  14  may be of any particular shape and configuration provided chamber  21  is shaped as described herein to produce a reverse flow of air. In the preferred embodiment, both first portion  12  and second portion  14  are generally cylindrical so as to resemble a cigarette or even a cigar and may be made of any suitable material including paper or plastic which are inexpensive and recyclable. 
     As shown in FIG. 1, first portion  12  has two parts which are separated by an abutment  16 . The abutment  16  separates the first portion  12  into a mouthpiece  18  and a plug  20  which has a chamber  21  positioned at its upstream end. Mouthpiece  18  is the downstream exit of inhaler  10  and is configured to deliver the medicament to the oral passageway of the user, and preferably to the mouth of the user. If a shorter inhaler is desired, then the downstream end of plug  20 , or even the downstream end of chamber  21 , may be used as the mouthpiece. 
     To increase the resemblance of inhaler  10  to a cigarette, the outer diameter of the mouthpiece  18  is preferably the same as the outer diameter of the second portion  14 . Although other sizes or cross sections may also be used, the mouthpiece  18  is also preferably made to resemble the filter portion of a cigarette and the second portion  14  is preferably made to resemble the tobacco portion of a cigarette. 
     Second portion  14  may be provided merely for aesthetic reasons to cover plug  20 . If second portion  14  is made of a structural material, then it may function to provide a protective cover for plug  20 . Further, if inhaler  10  is configured to resemble a cigarette or a cigar, then second portion  14  may comprise a longitudinally extending hollow cylinder so that, with mouthpiece  18 , inhaler  10  appears to be a single longitudinally extending cylinder. In this embodiment, plug  20  and second portion  14  are configured to lockingly receive second portion  14  in place on plug  20  so that, during use, plug  20  is not accidentally dislodged. To this end, the outer diameter of the plug  20  is preferably substantially the same as the inner diameter of the second portion  14  allowing the second portion  14  to slide on the plug  20  between a first position shown in FIG. 1 and a second position shown in FIG. 2 in which second portion  14  abuts against abutment  16 . 
     When in use, air flows generally longitudinally through the inhaler  10 . The distal end of the second portion  14  may have a cap  22  provided with an inlet  24  that allows air to enter the inhaler  10  (see FIG.  4 ). Optionally, a filter might be placed in the inlet  24 , or the cap  22  sloped inward to act as a baffle if there is some concern about contaminants entering the inhaler  10 , or concern that users might try to extract the nicotine in bulk from the inhaler  10 . Further, the inclusion of a filter, which may have an exposed face which has the appearance of tobacco would assist inhaler  10  to resemble a cigarette. Similarly, distal end  27  of the mouthpiece  18  may have a plate  26  with an air outlet  28  that allows air to exit the inhaler  10  (see FIG.  5 ). Again, a filter might be placed in the outlet  28  or the plate  26  angled inwardly to act as a baffle. The inclusion of a filter at distal end  27  would result in inhaler  10  more closely resembling a cigarette. Further, by drawing through a filter, inhaler  10  would better simulate smoking. 
     Air transfer between first portion  12  and second portion  14  occurs through an orifice  30  in the wall of the first potion  12 . Thus, a user inhales through distal end  27  of mouthpiece  18  which creates an area of reduced pressure at the outlet  28  extending throughout the inhaler  10 . Air is drawn into the inlet  24 , through the second portion  14 , through the orifice  30 , through the chamber  21 , through the remainder of the first portion  12  and into the user&#39;s mouth through the outlet  28 . 
     Referring now to FIG. 6, a reservoir  32  is shown in the first position. Reservoir  32  may be of any configuration which is large enough to hold the desired quantity of medicament. The medicament may be any medicament which may be inhaled. For example, the medicament may be a solid (e.g. a powdered medicament or a particulate medicament) or an otherwise fluid medicament (such as a gel or a volatile liquid) wherein a passing airflow through the inhaler can entrain the air directly over the medicament into which some of the medicament has volatilized. Preferably, the medicament is a “solid” medicament comprising individual particles capable of being inhaled. 
     The solid medicament is preferably a stable powder in a size range suitable for deposition on and absorption across the small airways and the alveolar lining taking into account the amount of water which may be absorbed by the particles as they pass through the lungs. Larger particles, over 5 μm tend to be deposited in the oral cavity and upper airways, whereas small particles under 0.5 μm tend to be exhaled from the lung without deposition. The particles grow in size as they are exposed to water in the atmosphere and in the airways of the user. For example, a 0.1 μm particle may increase to about 0.5 μm as it passes through the airways to the alveoli and smaller airways of a user. In order to have an appropriate mass, the individual medicament particles, when they exit from the inhaler, may vary in size from about 0.1 μm to about 5, preferably from about 0.1 μm to about 3 μm, more preferably from about 0.1 μm to about 2 μm and most preferably from about 0.1 μm to about 1 μm. However, it should be noted that the individual particles in the medicament introduced into the inhaler may be aggregated into larger aggregates which are subsequently broken down in the turbulent air flow on inhalation. 
     The following discussion is premised on the medicament being a “solid”. It will be appreciated that the inhaler may also be used with suitable modifications with the other formulations described herein. Reservoir  32  may contain one or a plurality of dosages wherein each dose is preferably removed from reservoir  32  by a plurality of inhalations. Each dose may be in its own individually sealed reservoir  32 . If inhaler  10  is configured to resemble a cigarette, then the medicament in reservoir  32  may be a nicotine formulation preferably a solid nicotine formulation and reservoir  32  may be sized so as to receive from about 0.1 to about 5 mg. of nicotine, more preferably from about 0.5 to about 2 mg. of nicotine and, most preferably, the amount of nicotine which is contained in a single cigarette (eg. about 1 mg.). Preferably, reservoir  32  contains a single dose and that dose is equivalent to the amount of nicotine which is contained in a single cigarette. It will be appreciated that reservoir  32  may be relatively large to hold multiple doses of a medicament. 
     It will also be appreciated that reservoir  32  may be used with a variety of different medicaments. Due to its construction, inhaler  10  preferably requires from about 1 to about 30, more preferably from about 2 to about 15 and, most preferably, from about 3 to about 10 inhalations to withdraw a single dose of medicament from reservoir  32  and transport it into the airways of the user. Therefore, inhaler  10  may be used with any medicament where an entire dose is to be withdrawn slowly. In many cases, the rate at which a medicament is ingested is neutral in terms of the efficacy of the medicament and inhaler  10  may be used with any such medicament. 
     As will be appreciated by those skilled in the art, if inhaler  10  is not designed to resemble a cigarette, then reservoir  32  may be any medicament storage device known in the industry. For example, reservoir  32  may be a capsule or a bulk medicament dispenser. This will necessitate the inclusion of a device for piercing the capsule so as to expose the medicament in reservoir  32  to airflow through inhaler  10  or to dose a medicament in reservoir  32  into a position where it is within the airstream created by inhaler  10 . 
     In the preferred embodiment, inhaler  10  is configured so as resemble a cigarette, cigar or the like (i.e. a longitudinally extending cylinder) and therefore reservoir  32  is designed to be pierced by a mechanism positioned within section portion  14 . Further, reservoir  32  is preferably openable by the external manipulation of inhaler  10  without any obvious controls to activate a piercing mechanism provided on the exterior of inhaler  10  or the need to disassemble inhaler  10  to pierce reservoir  32 . 
     For example, as shown in the Figures, reservoir  32  may be designed to be pierced by a relative motion between reservoir  32  and first portion  12 . Reservoir  32  may also be opened by removing a sealing cover such as be peeling off a releasably attached panel. The reservoir  32  may be accordingly formed from a strip  34  of plastic, foil or other material that is substantially impervious to airflow and can be conveniently bonded together. The strip  34  is folded onto itself and the edges sealed together to form the reservoir  32  having a closed end  36  and an openable end  38  and containing the powder  39  to be inhaled. The openable end  38  is temporarily or releasably sealed for example, in a cruciform pattern, in addition to the edge sealing. The edge sealing of the strip  34  ceases shortly after the cruciform pattern of the openable end  38  leaving loose ends  40  which are attached to the inner surface of the second portion  14  in the region of the plug  20 . The loose ends  40  thus hold the openable end  38  of the reservoir  32  in close proximity to the chamber  21  in the first position. The device can be stored or transported in this first position without spilling the powder  39  from the reservoir  32 . 
     As shown in FIG. 6, chamber  21  extends between a first end  42  and a second end  44 . Second end  44  is provided at the junction of chamber  21  and plug  20 . First end  42  defines an opening  43  which is positioned so as to draw medicament from reservoir  32 . Reservoir  32  is preferably positioned adjacent opening  43 . Opening  43  is relatively small. Opening  43  is preferably circular in shape and may have a diameter from about 3 mm to about 0.5 mm, more preferably from about 2 mm to about 1 mm, and most preferably about 1.5 mm. 
     Orifice  30  may be positioned at an intermediate point along plug  20  or chamber  21 . Orifice  30  may be positioned on plug  20  adjacent second end  44 , or preferably, orifice  30  is positioned in chamber  21  between second end  44  and first end  42 . The closer orifice  30  is positioned to opening  43 , the greater the amount of medicament which will be withdrawn from reservoir  32  upon each inhalation. Accordingly, in order to increase the efficiency of inhaler  10 , orifice  30  is positioned closer to opening  43 . In order to better simulate cigarette smoking, orifice  30  may be positioned at an intermediate position between first and second ends  42  and  44  so that a number of inhalations will be required to withdraw a full dose of medicament from reservoir  32 . 
     Chamber  21  is configured so that the cross-sectional area of first end  42  is less than the cross-sectional area of second end  44 . Preferably, as shown in FIG. 6, the cross-sectional area continually diminishes from second end  44  to first end  42 . More preferably, the cross-sectional area decreases at a constant rate from second end  44  to first end  42 . The cross-sectional shape of chamber  21  may be of an particular geometric configuration. For example, chamber  21  may be circular, square or triangular in cross-section. In the preferred embodiment, chamber  21  is frusto-conical in shape. The first end may have a diameter of approximately 15 mm and chamber  21  may taper at approximately 20 degrees. Such a chamber is both effective and easily produced although chambers of other shapes or dimensions are workable. In particular, a chamber  21  having decreasing cross sectional area near the first end  42  only is operable. The taper of the first end  42  of the chamber  21  preferably approximates that of the openable end  38  of the reservoir  32 . 
     To use the inhaler, reservoir  32  must be brought into air flow communication with first end  42 . To do this, the user may slide the second portion  14  relative to the first portion  12  from the first position (FIG. 1) to the second position (FIG.  2 ), such as by tapping the inhaler  10  on a hard surface. The movement between the first and second positions may be about 5 mm and results in the inhaler  10  being configured as shown in FIG.  2 . As the second portion  14  is moved to the second position, the chamber  21  advances through the temporary seal of the openable end  38  of the reservoir  32 . In the resulting second position, it is preferred that reservoir  32  have sealed edges which surround and substantially seal, and preferably completely seal, the first end  42  of the chamber  21 . Thus, in the second position, air and powder  39  can travel to or from the reservoir  32  via opening  43 . 
     Reservoir  32  need not provide an absolute airtight seal around the first end  42  of the chamber  21 , but any leaks should not entrain an appreciable amount of powder  39  and transport it into the chamber  21 . Inhaler  10  will function with secondary air entering reservoir  32  directly from second portion  14  without travelling through chamber  21 . For example, any leaks in the airtight seal between first end  42  and reservoir  32  may permit up to, for example, about 5 percent of the air inhaled by a user to travel directly into reservoir  32 . Such air is preferably directed at the surface of medicament  39  so as to break up or deconsolidate the medicament in reservoir  32 . The loosened material resulting from this process becomes more readily drawn into chamber  21  though the action of the primary air entering through orifice  30 . Chamber  21  may be designed, such as by providing one or more grooves  45  on the outer surface of chamber  21  so as to direct jets of air at the surface of medicament  39 . 
     Upon inhalation, powder  39  is drawn from the reservoir  32  through the opening  43  of the chamber  21  primarily by air currents (or entirely if there are no leaks or grooves  45 ) originating in the chamber  21 . If desired, the inhaler  10  could also be adapted to use a standard pharmaceutical capsule as the reservoir  32 . For example, the capsule could be held in fixed relation to the second portion  14  and the first end  42  of the chamber  21  adapted to pierce the capsule when the second portion  14  is moved to the second position (not shown). 
     Referring now to FIG. 3, a portion of the inhaler  10  is shown in the second position. As discussed above, a person inhaling on the inhaler  10  draws air through the second portion  14  which flows through the orifice  30  and into the chamber  21 . The movement of air through the inhaler  10  is most restricted at the orifice  30 . For example, orifice  30  may be circular and may have a diameter from about 4 mm to about 1 mm, more preferably from about 3 mm to about 1.5, and most preferably about 2 mm in diameter. Further, an inhaler may be provided with more than one orifice  30 . Because of the restriction in cross sectional area of airflow at the orifice  30 , the air travels quickly in the area of the orifice  30  creating an inflow jet  46 . Orifice  30  is shaped and configured so as to direct air into chamber  21  in an undirected fashion. For example, orifice  30  is provided in the side wall of chamber  21  without any baffles or other deviation in the wall surrounding orifice  30  so as to direct air either towards first end  42  or second end  44 . Accordingly, inflow jet  46  travels inwardly into chamber  21  along an axis which is substantially transverse to the wall of chamber  21  adjacent orifice  30 . 
     A portion of the air entering via inflow jet  46  flows towards the second end  44  of the chamber  21  (primary airflow  48 ). This air is drawn towards the vacuum created by the person inhaling on the inhaler  10 . The other portion of the air flow (secondary airflow  50 ) flows towards the first end  42  of the chamber  21  and into the reservoir  32  before travelling through chamber  21  to distal end  27 . As shown in FIG. 3, the secondary airflow  50  travels rearwardly to reservoir  32  (delivery branch  52 ) and then scours the surface of the powder  39  in the reservoir  32  and entrains a small portion of the powder  39 . A return branch  54  of the secondary airflow  50  then flows back towards the second end  44  of the chamber  21  to a point where at least some and preferably all of it, mixes with the primary airflow  48 . Powder  39  is entrained in the return branch  54  of the secondary airflow  50  as it mixes with the primary airflow  48  and is carried through the inhaler  10  with the primary airflow  48  to the user. Because of dilution, the concentration of powder  39  in the primary airflow  48  is significantly less than the concentration of powder  39  in the secondary airflow  50 . 
     When air is drawn through inhaler  10 , a pressure differential is set up in inhaler  10 . The focal point of this pressure differential is across orifice  30  in chamber  21 . Upon inhalation, the air pressure inside chamber  21  is reduced and consequently, the air entering orifice  30  has a higher static pressure. It is believed that the effectiveness of inhaler  10  is assisted by the Coanda Effect whereby a stream of quickly moving air tends to travels along a nearby surface. Pursuant to the Coanda Effect, when a stream of gas at a given pressure is introduced to a gas at a lower pressure, the higher pressure gas will tend to stick to the nearest solid object. This creates a resultant negative pressure zone inwards of the nearest solid object. Without being limited by theory, referring to FIG. 3, as incoming air jet  46  enters chamber  21  via orifice  30 , a portion of the air travels along the decreasing cross-sectional area of chamber  21  towards opening  43  (deliver branch  52 ). A negative air pressure is created centrally within chamber  21  along axis III—III. This provides a low pressure zone for the air exiting reservoir  32  to travel towards distal end  27  of inhaler  10  (return branch  54 ). It is believed that the air entering orifice  30  has virtually no depth in which to produce a laminar flow component. Therefore, deliver branch  52  is turbulent in nature. 
     Due to the Coanda Effect, the tendency is for approximately half of the air entering orifice  30  to try and travel to opening  43  of chamber  21 . As the cross-sectional area of chamber  21  diminishes, the local air velocity pressure component increases and is matched by a decrease in static pressure. The drop in static pressure further encourages delivery branch  52  to travel in a reverse flow towards opening  43 . Thus, the resultant turbulent nature of the air adjacent to opening  43  is sufficient to entrain some of the powder  39 . Since the dominant effect is to force air through inhaler  10  to distal end  27 , a portion of the captured content of power  39  is turbulently drawn into first portion  12  and then out through mouthpiece  18 . 
     As well as entraining powder  39 , the turbulent airflow also has a consolidating effect on power  39  in reservoir  32 . This limits the amount of medicament which may be drawn up into chamber  21  with any particular inhalation. If a small secondary air supply is provided (e.g. a pair of opposed grooves  45 ) bypass air jets may be provided which are sufficient to just disrupt the surface of powder  39  within reservoir  32 . The portion of disrupted powder  39  at the air/medicament interface is caught up in the turbulent airflow and eventually leaves reservoir  32 . 
     As an alternative (or in addition) to introducing side air jets directed at powder  39 , it is also possible to simply agitate inhaler  10 . For example, if the device is tapped or flicked (similar to the action which would be required to dislodge ash from a burning cigarette) the surface of powder  39  can be encouraged to deconsolidate. The loosened material resulting from this process becomes more readily caught up in the turbulent air inside reservoir  32 , which scours out the predominantly empty volume of reservoir  32 . 
     The location of the orifice  30  can be altered to increase or decrease the effectiveness of the secondary airflow  50  in removing powder  39  from the reservoir  32 . Moving the orifice  30  to a position adjacent the second end  44  will reduce the amount of powder  39  inhaled with each inhalation. Similarly, moving the orifice  30  towards the first end  42  generally increases the amount of powder  39  drawn in with each inhalation. In a preferred embodiment for use as a device for inhaling nicotine as a replacement for smoking, an amount of nicotine similar to that inhaled from a regular cigarette would be inhaled in 5 to 10 inhalations. 
     The descriptions of airflow patterns given above have been simplified or idealized for assistance in understanding the invention. For example, it is likely that flows throughout the inhaler  10  are turbulent and may contain components of flows in many directions. Further, the use of FIG. 3 is not intended to imply that the airflows in the inhaler  10  move in a plane. Nor is it necessary for the working of the invention that the secondary airflow  50  be exactly as shown provided that a secondary airflow  50  capable of entraining the powder  39  is created.