GB2276101A - Spray nozzles for pharmaceutical inhalers - Google Patents

Abstract

A spray nozzle structure for a pharmaceutical inhaler is disclosed in which the nozzle is positioned in a curved or conical convex portion (28) of the nozzle structure. The valved outlet of a pressurised medicament container engages step (16) in the nozzle to cause discharge when the container is depressed. An alternative nozzle shown in Fig. 8 is provided with a plurality of parallel passages (36). <IMAGE>

Description

SPRAY N07 FS FOR PHARMACEUTICAL INHALERS This invention relates to spray nozzles for pharmaceutical inhalers, for example for use by asthma sufferers.

In the accompanying drawings, Figures 1, 2 and 3 show a conventional inhaler nozzle structure. Figure 2 is a section on line 2-2 of Figure 1, and Figure 3 is an enlarged reversed view of the circled part of Figure 3.

Referring to the figures, a conventional pharmaceutical inhaler consists of a body portion 10 into which a pressurised canister containing a drug and a suitable carrier propellant may be inserted, and located by means of ribs 11.

A stem 14 of the body portion has a bore 15 which receives a valved outlet pipe of the canister. The end of the outlet pipe bears on a step 16 within the base so that compressing the body portion and canister together opens the valve and causes the discharge under pressure of a single measured quantity of the drug in its carrier medium.

The dose passes down a passage 17 in the stem 14, through a parallel-bore conduit 18 to a discharge nozzle 20, and thence through a mouthpiece 22 of the housing 10.

The shape and direction of the discharge plume and the dispersion of the droplets or particles therein are critical to effective administration of a controlled dose to the patient.

Conventionally, the nozzle 20 is positioned in a cylindrical recess 23 in the stem having a parallel sided portion 24 and a frusto-conical base 26. In order for the patient to insert the mouthpiece at the correct orientation for discharge of the spray whilst at the same time holding the housing 10 and the canister at a convenient angle, the axis of the mouthpiece 22 is inclined at an obtuse angle of about 105 degrees to that of the housing 10 and stem 14. Because of this geometry, the conical recess is not perpendicular to the surface of the stem 14, resulting in the parallel sided portion 24 being shorter on one side than the other.

The dimensions of the nozzle 20 and the recess 23 are such that the discharge plume does not impinge directly upon the sides of the recess 23. However it has been found that for no obvious reason the drug is nevertheless deposited on the surfaces of the recess 23, reducing the quantity of drug administered, rendering the dose inaccurate and causing a build-up of deposits around the nozzle wihch could obstruct or deflect the plume, further compounding the problem.

For example, a deflected plume could strike the side wall of the mouth piece, or it may be directed on to the patient's tongue or mouth rather than dispersed into his airway. In these circumstances, the patient does not receive the full dose into his respiratory system, and if some of the drug is instead taken into his digestive system, eg.

because it has been received in his mouth or on his tongue undesirable clinical side effects may be produced.

Furthermore, we have found that again for no obvious reason the plume from a clean nozzle may be deflected or asymmetric, its axis being displaced by perhaps 1.5cm over a path of about 7cm, thereby reducing the probability of correct dispersion of the dose for inhalation.

One partial but unsatifactory solution to this problem is to reduce the angle of divergence of the plume, ie. to make it a narrower more concentrated jet. However this may result in the jet striking the back of the throat, again depositing the drug rather than dispersing it for inhalation and causing added discomfort to a patient who may already be distressed due to an asthma attack.

A further problem with known inhaler spray nozzles is that of adequately matching the dimensions of the conduit 18 and nozzle 20 to the particular drug formulation and carrier-propellant. Different drugs have different flow and dispersion characteristics (particularly as between powder and liquid formulations) and it is often difficult to achieve the optimum balance between plume shape, total dose volume and discharge duration.

The present invention has amongst its objections the avoidance or at least reduction of one or both of these problems.

We have analysed the performance of the conventional nozzle and we believe that the plume when issuing from the nozzle at the base of the conical recess 23 causes a reduction in pressure in the air immediately surrounding it, by entrainment thereof. This reduction in pressure leads to turbulence in the surface of the plume and the generation of vortices which upon rotation out of the plume come into contact with the base 26 and wall 24 of the recess and deposit drug thereon. Furthermore the unequal length of the sides of the parallel portion 24 results in the plume being affected by the presence of the wall more on one side than the other, probably due to drag or pressure-difference effects causing deflection of the plume, so that it is no longer evenly distributed about the axis of its initial discharge.

To avoid these disadvantages, the present invention provides in one aspect a spray nozzle structure for a pharmaceutical inhaler wherein the nozzle is positioned in a domed or conical convex portion of the nozzle structure.

The convex portion may be recessed within the surrounding nozzle structure.

Preferably, the dimension of the recess perpendicular to the axis of discharge of the nozzle is between one tenth and one third (and preferably about one sixth) greater than the base width of the convex portion structure.

The height of the convex portion may be between one tenth and one third and preferably about one sixth of its base width.

A projection (for example a step) may be provided within the nozzle structure to engage an outlet pipe of a pressurised canister whereby to discharge medication into a passage connected to the nozzle, the projection being on the opposite side of the passage to the nozzle.

Placing the projection on the opposite side of the passage may avoid an undesirable increase in the length of the flow path through the convex structure to the nozzle compared to the path length in the conventional device.

In another aspect the invention provides a spray nozzle structure for a pharmaceutical inhaler, comprising a recess defined in said structure and having an open end and a base, and a nozzle in a portion of the base of the recess which projects towards the open end of the recess.

In a further aspect, the invention provides a spray nozzle structure for a pharmaceutical inhaler comprising an array of separate nozzles.

By providing a plurality of nozzles (preferably three to ten, and in preferred embodiments five, six or seven) it is possible at the design stage to select a combination of nozzle diameter, spacing and number of nozzles to enable discharge of a measured dose in a time interval and with a plume shape suited to the particular drug and carrier-propellant.

Preferably each nozzle is at the end of a separate conduit connecting with a passage into which medication is discharged.

With this arrangement, the ability to vary the length and/or shape of each conduit gives the designer an additional variable with which to control the characteristics of the discharge.

The nozzles may be parallel and/or may be disposed in a convex domed or conical structure or in a recess having any or all of the features contemplated above. They may for example all be at the apex of a frusto-conical projection, or may be distributed around the central region of a domed surface.

Specific embodiments of the invention will now be described by way of example only with reference to the remainder of the accompanying drawings, wherein: Figures 4, 5 and 6 show sections through first, second and third embodiments of the first aspect of the invention.

Figures 7 and 8 show an embodiment of a second aspect of the invention, Figure 8 being a section on line 8-8 of Figure 7.

In Figures 4 to 8, features already described carry the same reference numerals.

In Figure 4, the base of the recess instead of having a frusto-conical form 23 is of a domed configuration 28 projecting towards the open end of the recess, the conduit 18 passing through the domed structure to the nozzle 20 at the apex thereof. The nozzle 20 thus is much nearer the external perimeter 30 of the recess 23, with the result that the discharge plume is much less affected by any area of low pressure created behind it, or by the asymmetry of the parallel walls 24 of the recess. Consequently drug deposition around the nozzle is reduced in this embodiment by some 60% compared to the conventional device of Figures 1 to 3. Furthermore the deviation of the axis of the plume is reduced to about one-tenth of that of the conventional comnstruction. The diameter of the nozzle 20 is in this example 0.51mm, the base diameter of the domed portion 28 is 3.3mm and its height is 0.5mm, ie. 15% or just under one sixth of the base diameter. The diameter of the recess, at 3.8mm is approximately 15% greater than the base diameter of the domed portion 28.

By locating the domed portion 28 in the recess 23 excessive lengthening of the conduit 18 is avoided. A substantially longer conduit would necessitate radical revision of the nozzle diameter if the nozzle is to be used with the same canister as that of Figure 3, to compensate for increased drag in the conduit. The conduit 18 furthermore can be maintained at substantially the same length, as in Figure 3, if the step 16 is placed on the opposite side of the passage 17 to the nozzle 20 and conduit 18. If a longer conduit 18 can be tolerated, the convex portion 28 need not be disposed in a recess.

However, more complicated injection moulding tooling could then be required.

Figure 5 shows a modified form of the device of Figure 4 in which the domed (part-spherical) portion 28 is replaced by a frusto-conical convex portion.

In Figure 6 the domed construction of the Figure 4 embodiment is shown in combination with a modified projection or step in the form of an annular shoulder 34. This again provides some reduction in the additional length of the conduit 18, further reduction being achieved by setting the domed portion 28 rather deeper in the recess 23, although perhaps at some cost to the improvement in drug deposition and plume deflection. Tooling cost may however be somewhat lower. The frusto-conical form 32 of the convex structure can also be employed in the Figure 6 embodiment.

In Figures 7 and 8 the stem 14 is provided with a spray nozzle structure having an array of seven separate nozzles 34 each at the end of a respective parallel conduit 36 communicating with the passage 17.

The nozzles are disposed at the base of a flat-bottomed recess 38.

Alternatively the array of nozzles could be disposed at or around the apex of a projecting, preferably convex portion as described with reference to Figures 4 to 6, or at the base of a conventional recess as in Figure 3. The flat or convex arrangements are preferred however.

In any of the embodiments of the invention the nozzle structure may be manufactured as a separate insert which is fitted in to the stem 14.

Alternatively or in addition the stem may be a separate component fitted into the housing 10.

Claims (12)

1. A spray nozzle structure for a pharmaceutical inhaler wherein the nozzle is positioned in a domed or conical convex portion of the nozzle structure.

2. A spray nozzle structure as claimed in Claim 1, wherein the convex portion is recessed within surrounding nozzle structure.

3. A spray nozzle structure as claimed in Claim 2, wherein the dimension of the recess perpendicular to the axis of discharge of the nozzle is between one tenth and one third (and preferably about one sixth) greater than the base width of the convex portion structure.

4. A spray nozzle structure as claimed in any preceding claim wherein the height of the convex portion is between one tenth and one third and preferably about one sixth of its base width.

5. A spray nozzle structure as claimed in any preceding claim wherein a projection is provided within the nozzle structure to engage an outlet pipe of a pressurised canister whereby to discharge medication into a passage connected to the nozzle, the projection being on the opposite side of the passage to the nozzle.

6. A spray nozzle structure as claimed in Claim 5, wherein the projection is a step.

7. A spray nozzle structure for a pharmaceutical inhaler, comprising a recess defined in said structure and having an open end and a base, and a nozzle in a portion of the base of the recess which projects towards the open end.

8. A spray nozzle structure for a pharmaceutical inhaler and comprising an array of separate nozzles.

9. A spray nozzle structure as claimed in Claim 7, wherein each nozzle orifice is at the end of a separate conduit connecting with a passage into which medication is discharged.

10. A spray nozzle structure as claimed in Claim 8 or 9, wherein the nozzles are parallel.

11. A spray nozzle structure as claimed in Claim 8, 9, or 10, wherein the nozzles are positioned in a domed or conical convex portion of the nozzle structure.

12. A spray nozzle structure substantially as herein described with reference to Figures 4 to 8 of the accompanying drawings.