U.S. patent application number 11/791385 was filed with the patent office on 2008-06-05 for dry powder inhaler formulations comprising surface-modified particles with anti-adherent additives.
This patent application is currently assigned to VECTURA LIMITED. Invention is credited to David Morton.
Application Number | 20080127972 11/791385 |
Document ID | / |
Family ID | 33548732 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080127972 |
Kind Code |
A1 |
Morton; David |
June 5, 2008 |
Dry Powder Inhaler Formulations Comprising Surface-Modified
Particles With Anti-Adherent Additives
Abstract
The present invention is concerned with a refinement of the
processing of particles that are to form a dry powder formulation
which is to be administered to the lung using a dry powder inhaler
(DPI) device. In particular, the present invention provides the
processing of particles of active material and particles of carrier
material in the presence of additive material to provide a powder
composition which exhibits excellent powder properties and which is
economical to produce.
Inventors: |
Morton; David; (Wiltshire,
GB) |
Correspondence
Address: |
Davidson, Davidson & Kappel, LLC
485 7th Avenue, 14th Floor
New York
NY
10018
US
|
Assignee: |
VECTURA LIMITED
Chippenham, Wiltshire
GB
|
Family ID: |
33548732 |
Appl. No.: |
11/791385 |
Filed: |
November 23, 2005 |
PCT Filed: |
November 23, 2005 |
PCT NO: |
PCT/GB2005/050211 |
371 Date: |
July 5, 2007 |
Current U.S.
Class: |
128/203.15 ;
206/528; 424/489 |
Current CPC
Class: |
A61K 9/145 20130101;
A61K 47/26 20130101; A61M 2202/064 20130101; A61M 15/0028 20130101;
A61K 31/58 20130101; A61K 31/55 20130101; A61K 31/473 20130101;
A61K 31/522 20130101; A61P 43/00 20180101; A61K 9/0075 20130101;
A61K 31/135 20130101; A61K 47/12 20130101 |
Class at
Publication: |
128/203.15 ;
424/489; 206/528 |
International
Class: |
A61M 15/00 20060101
A61M015/00; A61K 9/14 20060101 A61K009/14; B65D 1/09 20060101
B65D001/09 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 23, 2004 |
GB |
0425758.0 |
Claims
1. A method of preparing a powder formulation, wherein active
particles are co-milled with an additive material, carrier
particles are separately co-milled with an additive material, and
the co-milled active and carrier particles are then combined.
2. A method as claimed in claim 1, wherein the additive material
co-milled with the active particles is the same as the additive
material co-milled with the carrier particles.
3. A method as claimed in claim 1, wherein the additive material
co-milled with the active particles is the different to the
additive material co-milled with the carrier particles.
4. A method as claimed in claim 1, wherein the amount of additive
material co-milled with the active particles is more by weight than
the amount of the additive material co-milled with the carrier
particles.
5. A method as claimed in claim 1, wherein the active particles
have a diameter of less than 10 .mu.m.
6. A method as claimed in claim 1, wherein the carrier particles
have a median diameter of between 3 .mu.m and 40 .mu.m.
7. A method as claimed in claim 1, wherein the co-milling is
Mechnofusion, Cyclomixing, or impact milling.
8. A method as claimed in claim 1, wherein the active particles and
carrier particles are co-milled using different milling
processes.
9. A method as claimed in claim 1, wherein the active particles are
first jet-milled to obtain the desired small particles size, then
they are co-milled with the additive material.
10. A method as claimed in claim 1, wherein the co-milled active
and/or carrier particles subsequently undergo a Mechanofusion
step.
11. A powder formulation obtainable using the method of claim
1.
12. A formulation as claimed in claim 11, wherein the additive
material forms a coating on the surfaces of the active and carrier
particles.
13. A formulation as claimed in claim 12, wherein the coating is
discontinuous.
14. A formulation as claimed in claim 12, wherein the coating is in
the form of additive material fused to the surfaces of the active
or carrier particles.
15. A formulation as claimed in claim 11, wherein the powder
formulation has a tapped density of at least 0.1 g/cc.
16. A formulation as claimed in claim 11, wherein the active agent
is one or more of: a steroid, a bronchodilator such as a
.beta..sub.2-agonist, an antimuscarinic or a xanthine; a nitrate;
an antihistamine; an anti-inflammatory agent; an anticholinergic
agent; a leukotriene receptor antagonist; an anti-allergic; an
anti-emetic; a hormonal drug (including a hormone analogue); a
sympathomimetic drug; an opioid; an analgesic such as a salicylate
or a non-steroidal anti-inflammatory drug; an acetylcholinesterase
inhibitor; an immunomodulatory; an NMDA receptor antagonist; a
hypoglycaemic such as a sulphonylurea; a biguanide or a
thiazolidinedione; a narcotic agonist or opiate antidote; a
phosphodiesterase inhibitor such as a non-specific
phosphodiesterase inhibitor or a phosphodiesterase type 3, type 4
or type 5 inhibitor; an antidepressant such as a tricyclic or
tetracyclic antidepressant, a selective serotonin and noradrenaline
reuptake inhibitor, a selective serotonin reuptake inhibitor, a
selective noradrenaline reuptake inhibitor, a noradrenaline and
selective serotonin reuptake inhibitor, a monoamine oxidase
inhibitor, a muscarinic antagonist or an azaspirone; a serotonin
agonist; a serotonin antagonist; an adrenergic agonist; an
adrenergic antagonist; an adrenergic neurone blocker; a
benzodiazepine; a mucolytic agent; an antibiotic or antibacterial
agent; an anti-fungal drug; an antiviral; a vaccine; an
immunoglobulin; a local anaesthetic; an anticonvulsant; an
angiotensin converting enzyme inhibitor; an angiotension II
receptor blocker; a calcium channel blocker; an alpha-blocker; an
antiarrhythmic; an anti-clotting agent; a potassium channel
modulator; a cholesterol-lowering drug; a diuretic; a smoking
cessation drug; a bisphosphonate; a dopamine agonist; a
nucleic-acid medicine; an antipsychotic; and pharmaceutically
acceptable salts or derivatives thereof.
17. A dry powder inhaler device comprising a powder formulation as
claimed in claim 11.
18. A device as claimed in claim 17, wherein the device is an
active device.
19. A device as claimed in claim 17, wherein the device is a
passive device.
20. A receptacle comprising a single dose of a powder formulation
as claimed in claim 11, which allows the dose to be dispensed using
a dry powder inhaler device.
21. A receptacle as claimed in claim 20, wherein the receptacle is
a capsule or blister.
22. The method of claim 5, wherein the carrier particles have a
median diameter less than 5 .mu.m.
23. The method of claim 6, wherein the carrier particles have a
median diameter of between 5 .mu.m and 30 .mu.m.
24. The method of claim 6, wherein the carrier particles have a
median diameter of between 5 .mu.m and 20 .mu.m.
25. The method of claim 6, wherein the carrier particles have a
median diameter of between 5 .mu.m and 15 .mu.m.
26. The method of claim 7, wherein the co-milling is ball milling,
jet milling, or milling using a high pressure homogeniser, or
combinations thereof.
27. The formulation of claim 15, wherein the powder formulation has
a tapped density of at least 0.2 g/cc.
28. The formulation of claim 15, wherein the powder formulation has
a tapped density of at least 0.3 g/cc.
29. The formulation of claim 15, wherein the powder formulation has
a tapped density of at least 0.4 g/cc.
30. The formulation of claim 15, wherein the powder formulation has
a tapped density of at least 0.5 g/cc.
Description
[0001] The present invention is concerned with a refinement of the
processing of particles that are to form a dry powder formulation
which is to be administered to the lung, for example using a dry
powder inhaler (DPI) device. In particular, the present invention
provides the processing of particles of active material and
particles of carrier material in the presence of additive material
to provide a powder composition which exhibits excellent powder
properties and which is economical to produce.
[0002] Inhalation represents a very attractive, rapid and
patient-friendly route for the delivery of systemically acting
drugs, as well as for drugs that are designed to act locally on the
lungs themselves. It is particularly desirable and advantageous to
develop technologies for delivering drugs to the lungs in a
predictable and reproducible manner.
[0003] The key features which make inhalation an exciting drug
delivery route are: rapid speed of onset; improved patient
acceptance and compliance for a non-invasive systemic route;
reduction of side effects; product life cycle extension; improved
consistency of delivery; access to new forms of therapy, including
higher doses, greater efficiency and accuracy of targeting; and
direct targeting of the site of action for locally administered
drugs, such as those used to treat lung diseases such as asthma,
COPD, CF or lung infections.
[0004] However, the powder technology behind successful dry powders
and DPI products remains a significant technical hurdle to those
wishing to succeed with this route of administration and to exploit
the significant product opportunities. Any formulation must have
suitable flow properties, not only to assist in the manufacture and
metering of the powders, but also to provide reliable and
predictable resuspension and fluidisation, and to avoid excessive
retention of the powder within the dispensing device.
[0005] The drug particles or particles of pharmaceutically active
material (also referred to herein as "active" particles) in the
resuspended powder must aerosolise into an ultra-fine aerosol so
that they can be transported to the appropriate target area within
the lung. Typically, for lung deposition, the active particles have
a diameter of less than 10 .mu.ms, frequently 0.1 to 7 .mu.m, 0.1
to 5 .mu.m, or 0.5 to 5 .mu.m.
[0006] For formulations to reach the deep lung or the blood stream
via inhalation, the active agent in the formulation must be in the
form of very fine particles, for example, having a mass median
aerodynamic diameter (MMAD) of less than 10 .mu.m. It is well
established that particles having an MMAD of greater than 10 .mu.m
are likely to impact on the walls of the throat and generally do
not reach the lung. Particles having an MMAD in the region of 5 to
2 .mu.m will generally be deposited in the respiratory bronchioles
whereas particles having an MMAD in the range of 3 to 0.05 .mu.m
are likely to be deposited in the alveoli and to be absorbed into
the bloodstream.
[0007] Preferably, for delivery to the lower respiratory tract or
deep lung, the MMAD of the active particles is not more than 10
.mu.m, and preferably not more than 5 .mu.m, more preferably not
more than 3 .mu.m, and may be less than 2 .mu.m, less than 1.5
.mu.m or less than 1 .mu.m. Especially for deep lung or systemic
delivery, the active particles may have a size of 0.1 to 3 .mu.m or
0.1 to 2 .mu.m.
[0008] Ideally, at least 90% by weight of the active particles in a
dry powder formulation should have an aerodynamic diameter of not
more than 10 .mu.m, preferably not more than 5 .mu.m, more
preferably not more than 3 .mu.m, not more than 2.5 .mu.m, not more
than 2.0 .mu.m, not more than 1.5 .mu.m, or even not more than 1.0
.mu.m.
[0009] When dry powders are produced using conventional processes,
the active particles will vary in size, and often this variation
can be considerable. This can make it difficult to ensure that a
high enough proportion of the active particles are of the
appropriate size for administration to the correct site. It is
therefore desirable to have a dry powder formulation wherein the
size distribution of the active particles is as narrow as possible.
For example, the geometric standard deviation of the active
particle aerodynamic or volumetric size distribution (.sigma.g), is
preferably not more than 2, more preferably not more than 1.8, not
more than 1.6, not more than 1.5, not more than 1.4, or even not
more than 1.2. This will improve dose efficiency and
reproducibility.
[0010] Fine particles, that is, those with an MMAD of less than 10
.mu.m and smaller, tend to be increasingly thermodynamically
unstable as their surface area to volume ratio increases, which
provides an increasing surface free energy with this decreasing
particle size, and consequently increases the tendency of particles
to agglomerate and the strength of the agglomerate. In the inhaler,
agglomeration of fine particles and adherence of such particles to
the walls of the inhaler are problems that result in the fine
particles leaving the inhaler as large, stable agglomerates, or
being unable to leave the inhaler and remaining adhered to the
interior of the inhaler, or even clogging or blocking the
inhaler.
[0011] The uncertainty as to the extent of formation of stable
agglomerates of the particles between each actuation of the
inhaler, and also between different inhalers and different batches
of particles, leads to poor dose reproducibility. Furthermore, the
formation of agglomerates means that the MMAD of the active
particles can be vastly increased, with agglomerates of the active
particles not reaching the required part of the lung.
[0012] These micron to submicron particle sizes required for deep
lung or systemic delivery lead to the problem that the respirable
active particles tend to be highly cohesive, which means they
generally exhibit poor flowability and poor aerosolisation.
[0013] To overcome the highly cohesive nature of such respirable
active particles, formulators have, in the past, included larger
carrier particles of an inert excipient in powder formulations, in
order to aid both flowability and drug aerosolisation. Relatively
large carrier particles have a beneficial effect on the powder
formulations because, rather than sticking to one another, the fine
active particles tend to adhere to the surfaces of the larger
carrier particles whilst in the inhaler device. The active
particles are supposed to release from the carrier particle
surfaces and become dispersed upon actuation of the dispensing
device, to give a fine suspension which may be inhaled into the
respiratory tract. In general, it has been considered that the
carrier particles should preferably have a mass median aerodynamic
diameter (MMAD) of at least about 90 .mu.m, and in general terms
should preferably have a mass median aerodynamic diameter (MMAD) of
greater than 40 .mu.m, and not less than 20 .mu.m.
[0014] However, whilst the addition of relatively large carrier
particles does tend to improve the powder properties, it also has
the effect of diluting the drug, usually to such an extent that 95%
or more by total weight of the formulation is carrier. Relatively
large amounts of carrier are required in order to have the desired
effect on the powder properties because the majority of the fine or
ultra-fine active particles need to adhere to the surfaces of the
carrier particles, otherwise the cohesive nature of the active
particles still dominates the powder and results in poor
flowability. The surface area of the carrier particles available
for the fine particles to adhere to decreases with increasing
diameter of the carrier particles. However, the flow properties
tend to become worse with decreasing diameter. Hence, there is a
need to find a suitable balance in order to obtain a satisfactory
carrier powder. An additional consideration is that one can get
segregation if too few carrier particles are included, which is
extremely undesirable.
[0015] An additional major problem experienced by formulators is
the variability in surface properties of drug and excipient
particles. Each active agent powder has its own unique inherent
stickiness or surface energy, which can range tremendously from
compound to compound. Further, the nature of the surface energies
can change for a given compound depending upon how it is processed.
For example, jet milling is notorious for generating significant
variations in surface properties because of the aggressive nature
of the collisions it employs. Such variations can lead to increased
surface energy and increased cohesiveness and adhesiveness.
[0016] Even in highly regular, crystalline powders, the short range
van der Waals forces (which include fixed dipole and similar fixed
charge related forces and which depend on the chemistry of the
functional groups exposed on the surface of the particles) can lead
to highly cohesive and adhesive powders.
[0017] Solutions to some of the problems touched upon above are
already known. For example, flow problems associated with larger
amounts of fine material (for example, in powder formulations
including relatively high proportions (such as up to from 5 to 20%
by total weight of the formulation) of fine lactose or drug and
fine lactose) may be overcome by use of a large fissured lactose as
carrier particles, as discussed in earlier patent applications
published as WO 01/78694, WO 01/78695 and WO 01/78696.
[0018] In order to improve the properties of powder formulations,
and in particular to improve the flowability and dispersibility of
the formulation, dry powder formulations often include additive
materials which are intended to reduce the cohesion between the
fine particles in the dry powder formulation. It is thought that
the additive material interferes with the weak bonding forces
between the small particles, helping to keep the particles
separated and reducing the adhesion of such particles to one
another, to other particles in the formulation if present and to
the internal surfaces of the inhaler device. Where agglomerates of
particles are formed, the addition of particles of additive
material decreases the stability of those agglomerates so that they
are more likely to break up in the turbulent air stream created on
actuation of the inhaler device, whereupon the particles are
expelled from the device and inhaled.
[0019] In the prior art, dry powder formulations are discussed
which include additive material (for example in the form of
distinct particles of a size comparable to that of the fine active
particles). In some embodiments, the additive material may be
applied to and form a coating, generally a discontinuous coating,
on the active particles or on any carrier particles.
[0020] Preferably, the additive material is an anti-adherent
material and it will tend to reduce the cohesion between particles
and will also prevent fine particles becoming attached to surfaces
within the inhaler device. Advantageously, the additive material is
an anti-friction agent or glidant and will give the powder
formulation better flow properties in the inhaler. The additive
materials used in this way may not necessarily be usually referred
to as anti-adherents or anti-friction agents, but they will have
the effect of decreasing the cohesion between the particles or
improving the flow of the powder. As such, the additive materials
are sometimes referred to as force control agents (FCAs) and they
usually lead to better dose reproducibility and higher fine
particle fractions (FPFs).
[0021] Therefore, an additive material or FCA, as used herein, is a
material whose presence on the surface of a particle can modify the
adhesive and cohesive surface forces experienced by that particle,
in the presence of other particles and in relation to the surfaces
that the particles are exposed to. In general, its function is to
reduce both the adhesive and cohesive forces.
[0022] The reduced tendency of the particles to bond strongly,
either to each other or to the device itself, not only reduces
powder cohesion and adhesion, but can also promote better flow
characteristics. This leads to improvements in the dose
reproducibility because it reduces the variation in the amount of
powder metered out for each dose and improves the release of the
powder from the device. It also increases the likelihood that the
active material which does leave the device will reach the lower
lung of the patient.
[0023] It is favourable for unstable agglomerates of particles to
be present in the powder when it is in the inhaler device. For a
powder to leave an inhaler device efficiently and reproducibly, it
is generally accepted that the particles should ideally be large,
preferably larger than about 40 .mu.m. Such a powder may be in the
form of either individual particles having a size of about 40 .mu.m
or larger and/or agglomerates of finer particles, the agglomerates
having a size of about 40 .mu.m or larger. The agglomerates formed
can have a size of as much as about 1000 .mu.m and, with the
addition of the additive material, those agglomerates are more
likely to be broken down efficiently in the turbulent airstream
created on inhalation. Therefore, the formation of unstable or
"soft" agglomerates of particles in the powder may be favoured
compared with a powder in which there is substantially no
agglomeration.
[0024] Such unstable agglomerates are retained whilst the powder is
inside the device but are then disrupted and broken up when the
powder is dispensed.
[0025] The use of additive materials in this manner is disclosed in
two earlier patent applications, published as WO 96/23485 and WO
97/03649.
[0026] It is also known that intensive co-milling of micronised
drug particles with additive material may be carried out in order
to produce composite particles. This co-micronisation can improve
dispersibility, as disclosed in the earlier patent application
published as WO 02/43701. In addition, the earlier application
published as WO 02/00197 discloses the intensive co-milling of fine
particles of excipient material with additive material, to create
composite excipient particles to which fine active particles and,
optionally, coarse carrier particles may be added. This
co-micronisation of fine excipient particles and additive material
has also been shown to improve dispersibility.
[0027] Whilst the various disclosures in the prior art of the use
of additive materials as force control agents do indicate
improvements in powder properties (such as the dispersibility and
flow) as a result of the addition of the additive material, the
known powders and processing methods fail to provide the maximum
effect possible with the optimum combination of small carrier and
drug, and do not provide the maximum effect possible from the least
necessary amount of additive material. The optimisation of the use
of the additive material is important for several reasons. Firstly,
it is clearly desirable to provide a dry powder formulation with
the best possible powder properties in order to ensure efficient,
reliable and accurate dosing. Secondly, it is also desirable to
minimise the amount of the additive material (or indeed of any
material) administered to the lung. This will reduce the risk of
adverse effects that may be caused by the material. Thirdly, it is
desirable to be able to deliver the maximum dose with optimum
efficiency from a minimum powder payload, especially for high dose
drugs. Finally, the use of as little additive material as possible
will also be more economical. These features will also help to keep
the device size small, maximise number of doses per device and
reduce device complexity.
[0028] The present invention seeks to improve upon the powder
formulations provided in the prior art, to ensure that their powder
properties are optimised and the powder preparation is simple and
economical.
[0029] It is also an object of the present invention to permit an
increased percentage of ultra-fine drug to be used in a
formulation, optionally with a fine carrier component, whilst still
providing a powder formulation which exhibits improved flow, and
improved aerosolisation due to the individually tailored surface
conditioning of the respective drug and carrier particles.
[0030] It has been found that the most advantageous powder system
incorporates one or more additives or force control agents on the
surface of the both the drug particles and the carrier particles,
in order to maximise the potential for flow and aerosolisation.
[0031] In the prior art, it is generally not suggested to attach
the additive to both the active particles and carrier or excipient
particles to obtain the advantages outlined here.
[0032] The minimum amount of the additive or FCA necessary to
improve powder properties is preferably used, for toxicology and
dosing reasons. What is more, the ideal incorporation of the
additive is in the form of at least an approximate single minimum
layer of additive material as a coating around each powder
component, that is around both the active particles and any carrier
particles present. As the drug particles are generally smaller
(i.e. less than 5 .mu.m), they will have a correspondingly higher
surface area to volume ratio than the generally larger (>5
.mu.m) carrier particles.
[0033] According to a first aspect of the present invention, a
method of preparing a powder formulation is provided, the method
comprising co-milling active particles with an additive material,
separately co-milling carrier particles with an additive material,
and then combining the co-milled active and carrier particles.
[0034] The co-milling steps preferably produce composite particles
of active and additive material or carrier and additive
material.
[0035] The powder formulations prepared according to the methods of
the present invention exhibit excellent powder properties that may
be tailored to the active agent, the dispensing device to be used
and/or various other factors. In particular, the co-milling of
active and carrier particles in separate steps allows different
types of additive material and different quantities of additive
material to be milled with the active and carrier particles.
Consequently, the additive material can be selected to match its
desired function, and the minimum amount of additive material can
be used to match the relative surface area of the particles to
which it is being applied.
[0036] In one embodiment, the active particles and the carrier
particles are both co-milled with the same additive material or
additive materials. In an alternative embodiment, the active and
carrier particles are co-milled with different additive
materials.
[0037] In one embodiment of the invention, active particles of less
than about 5 .mu.m diameter are co-milled with an appropriate
amount of an additive or force control agent, whilst carrier
particles with a median diameter in the range of about 3 .mu.m to
about 40 .mu.m are separately co-milled with an appropriate amount
of an additive.
[0038] Generally, the amount of additive co-milled with the carrier
particles will be less, by weight, than that co-milled with the
active particles. Nevertheless, the amount of additive used is kept
to a minimum whilst being sufficient to have the desired effect on
the powder properties. The treated drug and carrier particles are
then combined to provide a formulation with the desired
features.
[0039] The additive material is preferably in the form of a coating
on the surfaces of the active and carrier particles. The coating
may be a discontinuous coating. In another embodiment, the additive
material may be in the form of particles adhering to the surfaces
of the active and carrier particles. Preferably, the additive
material actually becomes fused to the surfaces of the active and
carrier particles
[0040] It is advantageous for carrier particles to be used in the
size range having a median diameter of about 3 to about 40 .mu.m,
preferably about 5 to about 30 .mu.m, more preferably about 5 to
about 20 .mu.m, and most preferably about 5 to about 15 .mu.m. Such
particles, if untreated with an additive are unable to provide
suitable flow properties when incorporated in a powder formulation
comprising ultra-fine active particles. Indeed, previously,
particles in these size ranges would not have been regarded as
suitable for use as carrier particles, and instead would have been
added in small quantities as a fine component. Such fine components
are known to increase the aerosolisation properties of formulations
containing a drug and a larger carrier, typically with median
diameter 40 .mu.m to 100 .mu.m or greater. However, the amount of
the fine components that may be included in such formulations is
limited, and formulations including more than about 10% fines tend
to exhibit poor properties unless special carrier particles are
included, such as the large fissured lactose carrier particles
mentioned above.
[0041] Alternatively, compositions of micronised drug and
micronised lactose are known, but only where this blend has
subsequently been successfully compressed and granulated into
pellets. This process is generally very difficult to control and
pellets are prone to destruction, resulting in powders with poor
flow properties.
[0042] However, following treatment with additive materials,
substantial changes in the powder characteristics of our fine
carrier powders are seen. Powder density is increased, even
doubled, for example from 0.3 g/cc to over 0.5 g/cc. Other powder
characteristics are changed, for example, the angle of repose is
reduced and contact angle increased.
[0043] Carrier particles having a median diameter of 3 to 40 .mu.m
are advantageous as their relatively small size means that they
have a reduced tendency to segregate from the drug component, even
when they have been treated with an additive, which will reduce
cohesion. This is because the size differential between the carrier
and drug is relatively small compared to that in conventional
formulations which include ultra-fine active particles and much
lager carrier particles. The surface area to volume ratio presented
by the fine carrier particles is correspondingly greater than that
of conventional large carrier particles. This higher surface area,
allows the carrier to be successfully associated with higher levels
of drug than for conventional larger carrier particles.
[0044] Carrier particles may be of any acceptable inert excipient
material or combination of materials. For example, carrier
particles frequently used in the prior art may be composed of one
or more materials selected from sugar alcohols, polyols and
crystalline sugars. Other suitable carriers include inorganic salts
such as sodium chloride and calcium carbonate, organic salts such
as sodium lactate and other organic compounds such as
polysaccharides and oligosaccharides. Advantageously, the carrier
particles comprise a polyol. In particular, the carrier particles
may be particles of crystalline sugar, for example mannitol,
dextrose or lactose. Preferably, the carrier particles are composed
of lactose.
[0045] Advantageously, the additive material or FCA includes one or
more compounds selected from amino acids and derivatives thereof,
and peptides and derivatives thereof. Amino acids, peptides and
derivatives of peptides are physiologically acceptable and give
acceptable release of the active particles on inhalation.
[0046] It is particularly advantageous for the additive to comprise
an amino acid. The additive may comprise one or more of any of the
following amino acids: leucine, isoleucine, lysine, valine,
methionine, and phenylalanine. The additive may be a salt or a
derivative of an amino acid, for example aspartame or acesulfame K.
Preferably, the additive consists substantially of an amino acid,
more preferably of leucine, advantageously L-leucine. The D- and
DL-forms may also be used. As indicated above, leucine has been
found to give particularly efficient dispersal of the active
particles on inhalation.
[0047] The additive may include one or more water soluble
substances. This helps absorption of the additive by the body if it
reaches the lower lung. The additive may include dipolar ions,
which may be zwitterions. It is also advantageous to include a
spreading agent as an additive, to assist with the dispersal of the
composition in the lungs. Suitable spreading agents include
surfactants such as known lung surfactants (e.g. ALEC.TM.) which
comprise phospholipids, for example, mixtures of DPPC (dipalmitoyl
phosphatidylcholine) and PG (phosphatidylglycerol). Other suitable
surfactants include, for example, dipalmitoyl
phosphatidylethanolamine (DPPE), dipalmitoyl phosphatidylinositol
(DPPI).
[0048] The additive may comprise a metal stearate, or a derivative
thereof, for example, sodium stearyl fumarate or sodium stearyl
lactylate. Advantageously, it comprises a metal stearate, for
example, zinc stearate, magnesium stearate, calcium stearate,
sodium stearate or lithium stearate. Preferably, the additive
material comprises magnesium stearate, for example vegetable
magnesium stearate, or any form of commercially available metal
stearate, which may be of vegetable or animal origin and may also
contain other fatty acid components such as palmitates or
oleates.
[0049] The additive may include or consist of one or more surface
active materials, in particular materials that are surface active
in the solid state, which may be water soluble or water
dispersible, for example lecithin, in particular soya lecithin, or
substantially water insoluble, for example solid state fatty acids
such as oleic acid, lauric acid, palmitic acid, stearic acid,
erucic acid, behenic acid, or derivatives (such as esters and
salts) thereof such as glyceryl behenate. Specific examples of such
materials are phosphatidylcholines, phosphatidylethanolamines,
phosphatidylglycerols and other examples of natural and synthetic
lung surfactants; lauric acid and its salts, for example, sodium
lauryl sulphate, magnesium lauryl sulphate; triglycerides such as
Dynsan 118 and Cutina HR; and sugar esters in general.
Alternatively, the additive may be cholesterol.
[0050] Other possible additive materials include sodium benzoate,
hydrogenated oils which are solid at room temperature, talc,
titanium dioxide, aluminium dioxide, silicon dioxide and starch.
Also useful as additives are film-forming agents, fatty acids and
their derivatives, as well as lipids and lipid-like materials.
[0051] In one embodiment of the invention, the additive comprises
an amino acid, a derivative of an amino acid, a metal stearate or a
phospholipid. Preferably, the additive comprises one or more of L-,
D- or DL-forms of leucine, isoleucine, lysine, valine, methionine,
phenylalanine, or Aerocine.TM., lecithin or magnesium stearate. In
another embodiment, the additive comprises leucine and preferably
L-leucine.
[0052] In some embodiments, a plurality of different additive
materials can be used.
[0053] The present invention can be carried out with any
pharmaceutically active agent. The terms "active particles" and
"particles of active material" and the like are used
interchangeably herein. The active particles comprise one or more
pharmaceutically active agents. The preferred active agents
include:
1) steroid drugs such as aclometasone, beclomethasone,
beclomethasone dipropionate, betamethasone, budesonide,
ciclesonide, clobetasol, deflazacort, diflucortolone,
desoxymethasone, dexamethasone, fludrocortisone, flunisolide,
fluocinolone, fluometholone, fluticasone, fluticasone proprionate,
hydrocortisone, triamcinolone, nandrolone decanoate, neomycin
sulphate, rimexolone, methylprednisolone and prednisolone; 2)
bronchodilators such as .beta..sub.2-agonists including salbutamol,
formoterol, salmeterol, fenoterol, bambuterol, bitolterol,
sibenadet, metaproterenol, epinephrine, isoproterenol, pirbuterol,
procaterol, terbutaline and isoetharine antimuscarinics including
ipratropium and tiotropium, and xanthines including aminophylline
and theophylline; 3) nitrates such as isosorbide mononitrate,
isosorbide dinitrate and glyceryl trinitrate; 4) antihistamines
such as azelastine, chlorpheniramine, astemizole, cetirizine,
cinnarizine, desloratadine, loratadine, hydroxyzine,
diphenhydramine, fexofenadine, ketotifen, promethazine,
trimeprazine and terfenadine; 5) anti-inflammatory agents such as
piroxicam, nedocromil, benzydamine, diclofenac sodium, ketoprofen,
ibuprofen, heparinoid, cromoglycate, fasafungine, iodoxamide and
p38 MAP kinase inhibitors; 6) anticholinergic agents such as
atropine, benzatropine, biperiden, cyclopentolate, oxybutinin,
orphenadine, glycopyrronium, glycopyrrolate, procyclidine,
propantheline, propiverine, tiotropium, trihexyphenidyl,
tropicamide, trospium, ipratropium bromide and oxitroprium bromide;
7) leukotriene receptor antagonists such as montelukast and
zafirlukast; 8) anti-allergics such as ketotifen; 9) anti-emetics
such as bestahistine, dolasetron, nabilone, prochlorperazine,
ondansetron, trifluoperazine, tropisetron, domperidone, hyoscine,
cinnarizine, metoclopramide, cyclizine, dimenhydrinate and
promethazine; 10) hormonal drugs (including hormone analogues) such
as lanreotide, octreotide, insulin, pegvisomant, protirelin,
thyroxine, salcotonin, somatropin, tetracosactide, vasopressin and
desmopressin; 11) sympathomimetic drugs such as adrenaline,
noradrenaline, dexamfetamine, dipirefin, dobutamine, dopexamine,
phenylephrine, isoprenaline, dopamine, pseudoephedrine, tramazoline
and xylometazoline; 12) opioids, preferably for pain management,
such as buprenorphine, dextromoramide, dextropropoxypene,
diamorphine, codeine, dextropropoxyphene, dihydrocodeine,
hydromorphone, papaveretum, pholcodeine, loperamide, fentanyl,
methadone, morphine, oxycodone, phenazocine, pethidine, tramadol
and combinations thereof with an anti-emetic; 13) analgesics such
as aspirin and other salicylates, paracetamol, clonidine, codine,
coproxamol, ergotamine, gabapentin, pregabalin, sumatriptan, and
non-steroidal anti-inflammatory drugs (NSAIDs) including celecoxib,
etodolac, etoricoxib and meloxicam; 14) acetylcholinesterase
inhibitors such as donepezil, galantamine and rivastigmine; 15)
immunomodulators such as interferon (e.g. interferon beta-1a and
interferon beta-1b) and glatiramer;
16) NMDA receptor antagonists such as mementine;
[0054] 17) hypoglycaemics such as sulphonylureas including
glibenclamide, gliclazide, glimepiride, glipizide and gliquidone,
biguanides including metformin, thiazolidinediones including
pioglitazone, rosiglitazone, nateglinide, repaglinide and acarbose;
18) narcotic agonists and opiate antidotes such as naloxone, and
pentazocine; 19) phosphodiesterase inhibitors such as non-specific
phosphodiesterase inhibitors including theophylline, theobromine,
IBMX, pentoxifylline and papaverine; phosphodiesterase type 3
inhibitors including bipyridines such as milrinone, amrinone and
olprinone; imidazolones such as piroximone and enoximone;
imidazolines such as imazodan and 5-methyl-imazodan;
imidazo-quinoxalines; and dihydropyridazinones such as indolidan
and LY181512
(5-(6-oxo-1,4,5,6-tetrahydro-pyridazin-3-yl)-1,3-dihydro-indol-2-
-one); dihydroquinolinone compounds such as cilostamide,
cilostazol, and vesnarinone; phosphodiesterase type 4 inhibitors
such as cilomilast, etazolate, rolipram, roflumilast and
zardaverine, and including quinazolinediones such as nitraquazone
and nitraquazone analogs; xanthine derivatives such as denbufylline
and arofylline; tetrahydropyrimidones such as atizoram; and oxime
carbamates such as filaminast; and phosphodiesterase type 5
inhibitors including sildenafil, zaprinast, vardenafil, tadalafil,
dipyridamole, and the compounds described in WO 01/19802,
particularly
(S)-2-(2-hydroxymethyl-1-pyrrolidinyl)-4-(3-chloro-4-methoxy-benzylamino)-
-5-[N-(2-pyrimidinylmethyl)carbamoyl]pyrimidine,
2-(5,6,7,8-tetrahydro-1,7-naphthyridin-7-yl)-4-(3-chloro-4-methoxybenzyla-
mino)-5-[N-(2-morpholinoethyl)carbamoyl]-pyrimidine, and
(S)-2-(2-hydroxymethyl-1-pyrrolidinyl)-4-(3-chloro-4-methoxy-benzylamino)-
-5-[N-(1,3,5-trimethyl-4-pyrazolyl)carbamoyl]-pyrimidine); 20)
antidepressants such as tricyclic and tetracyclic antidepressants
including amineptine, amitriptyline, amoxapine, butriptyline,
cianopramine, clomipramine, dosulepin, doxepin, trimipramine,
clomipramine, lofepramine, nortriptyline, tricyclic and tetracyclic
amitryptiline, amoxapine, butriptyline, clomipramine,
demexiptiline, desipramine, dibenzepin, dimetacrine, dothiepin,
doxepin, imipramine, iprindole, levoprotiline, lofepramine,
maprotiline, melitracen, metapramine, mianserin, mirtazapine,
nortryptiline, opipramol, propizepine, protriptyline, quinupramine,
setiptiline, tianeptine and trimipramine; selective serotonin and
noradrenaline reuptake inhibitors (SNRIs) including clovoxamine,
duloxetine, milnacipran and venlafaxine; selective serotonin
reuptake inhibitors (SSRIs) including citalopram, escitalopram,
femoxetine, fluoxetine, fluvoxamine, ifoxetine, milnacipran,
nomifensine, oxaptotiline, paroxetine, sertraline, sibutramine,
venlafaxine, viqualine and zimeldine; selective noradrenaline
reuptake inhibitors (NARIs) including demexiptiline, desipramine,
oxaprotiline and reboxetine; noradrenaline and selective serotonin
reuptake inhibitors (NASSAs) including mirtazapine; monoamine
oxidase inhibitors (MAOIs) including amiflamine, brofaromine,
clorgyline, .alpha.-ethyltryptamine, etoperidone, iproclozide,
iproniazid, isocarboxazid, mebanazine, medifoxamine, moclobemide,
nialamide, pargyline, phenelzine, pheniprazine, pirlindole,
procarbazine, rasagiline, safrazine, selegiline, toloxatone and
tranylcypromine; muscarinic antagonists including benactyzine and
dibenzepin; azaspirones including buspirone, gepirone, ipsapirone,
tandospirone and tiaspirone; and other antidepressants including
amesergide, amineptine, benactyzine, bupropion, carbamazepine,
fezolamine, flupentixol, levoprotiline, maprotiline, medifoxamine,
methylphenidate, minaprine, nefazodone, nomifensine, oxaflozane,
oxitriptan, rolipram, sibutramine, teniloxazine, tianeptine,
tofenacin, trazadone, tryptophan, viloxazine, and lithium salts;
21) serotonin agonists such as 2-methyl serotonin, buspirone,
ipsaperone, tiaspirone, gepirone, lysergic acid diethylamide, ergot
alkaloids, 8-hydroxy-(2-N,N-dipropylamino)-tetraline,
1-(4-bromo-2,5-dimethoxyphenyl)-2-aminopropane, cisapride,
sumatriptan, m-chlorophenylpiperazine, trazodone, zacopride and
mezacopride; 22) serotonin antagonists including ondansetron,
granisetron, metoclopramide, tropisetron, dolasetron,
trimethobenzamide, methysergide, risperidone, ketanserin,
ritanserin, clozapine, amitryptiline,
R(+)-.alpha.-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidi-
ne-methanol, azatadine, cyproheptadine, fenclonine,
dexfenfluramine, fenfluramine, chlorpromazine and mianserin; 23)
adrenergic agonists including methoxamine, methpentermine,
metaraminol, mitodrine, clonidine, apraclonidine, guanfacine,
guanabenz, methyldopa, amphetamine, methamphetamine, epinephrine,
norepinephrine, ethylnorepinephrine, phenylephrine, ephedrine,
pseudo-ephedrine, methylphenidate, pemoline, naphazoline,
tetrahydrozoline, oxymetazoline, xylometazoline,
phenylpropanolamine, phenylethylamine, dopamine, dobutamine,
colterol, isoproterenol, isotharine, metaproterenol, terbutaline,
metaraminol, tyramine, hydroxyamphetamine, ritodrine, prenalterol,
albuterol, isoetharine, pirbuterol, bitolterol, fenoterol,
formoterol, procaterol, salmeterol, mephenterine and
propylhexedrine; 24) adrenergic antagonists such as
phenoxybenzamine, phentolamine, tolazoline, prazosin, terazosin,
doxazosin, trimazosin, yohimbine, ergot alkaloids, labetalol,
ketanserin, urapidil, alfuzosin, bunazosin, tamsulosin,
chlorpromazine, haloperidol, phenothiazines, butyrophenones,
propranolol, nadolol, timolol, pindolol, metoprolol, atenolol,
esmolol, acebutolol, bopindolol, carteolol, oxprenolol, penbutolol,
carvedilol, medroxalol, naftopidil, bucindolol, levobunolol,
metipranolol, bisoprolol, nebivolol, betaxolol, carteolol,
celiprolol, sotalol, propafenone and indoramin; 25) adrenergic
neurone blockers such as bethanidine, debrisoquine, guabenxan,
guanadrel, guanazodine, guanethidine, guanoclor and guanoxan; 26)
benzodiazepines such as alprazolam, bromazepam, brotizolam,
chlordiazepoxide, clobazam, clonazepam, clorazepate, demoxepam,
diazepam, estazolam, flunitrazepam, flurazepam, halazepam,
ketazolam, loprazolam, lorazepam, lormetazepam, medazepam,
midazolam, nitrazepam, nordazepam, oxazepam, prazepam, quazepam,
temazepam and triazolam; 27) mucolytic agents such as
N-acetylcysteine, recombinant human DNase, amiloride, dextrans,
heparin, desulphated heparin and low molecular weight heparin; 28)
antibiotic and antibacterial agents such as metronidazole,
sulphadiazine, triclosan, neomycin, amoxicillin, amphotericin,
clindamycin, aclarubicin, dactinomycin, nystatin, mupirocin and
chlorhexidine; 29) anti-fungal drugs such as caspofungin,
voriconazole, polyene antibiotics including amphotericin, and
nystatin, imidazoles and triazoles including clotrimazole,
econazole nitrate, fluconazole, ketoconazole, itraconazole,
terbinafine and miconazole; 30) antivirals such as oseltamivir,
zanamivir, amantadine, inosine pranobex and palivizumab, DNA
polymerase inhibitors including aciclovir, adefovir and
valaciclovir, nucleoside analogues including famiciclovir,
penciclovir and idoxuridine and interferons; 31) vaccines; 32)
immunoglobulins; 33) local anaesthetics such as amethocaine,
bupivacaine, hydrocortisone, methylprednisolone, prilocaine,
proxymetacaine, ropivacaine, tyrothricin, benzocaine and
lignocaine; 34) anticonvulsants such as sodium valproate,
carbamazepine, oxcarbazepine, phenyloin, fosphenytoin, diazepam,
lorazepam, clonazepam, clobazam, primidone, lamotrigine,
levetiracetam, topiramate, gabapentin, pregabalin, vigabatrin,
tiagabine, acetazolamide, ethosuximide and piracetam; 35)
angiotensin converting enzyme inhibitors such as captopril,
cilazapril, enalapril, fosinopril, imidapril hydrochloride,
lisinopril, moexipril hydrochloride, perindopril, quinapril,
ramipril and trandolapril; 36) angiotension II receptor blockers,
such as candesartan, cilexetil, eprosartan, irbesartan, losartan,
olmesartan medoxomil, telmisartan and valsartan; 37) calcium
channel blockers such as amlodipine, bepridil, diltiazem,
felodipine, flunarizine, isradipine, lacidipine, lercanidipine,
nicardipine, nifedipine, nimodipine and verapamil; 38)
alpha-blockers such as indoramin, doxazosin, prazosin, terazosin
and moxisylate; 39) antiarrhythmics such as adenosine, propafenone,
amidodarone, flecainide acetate, quinidine, lidocaine
hydrochloride, mexiletine, procainamide and disopyramide; 40)
anti-clotting agents such as aspirin, heparin and low molecular
weight heparin, epoprostenol, dipyridamole, clopidogrel, alteplase,
reteplase, streptokinase, tenecteplase, certoparin, heparin
calcium, enoxaparin, dalteparin, danaparoid, fondaparin, lepirudin,
bivalirudin, abciximab, eptifibatide, tirofiban, tinzaparin,
warfarin, lepirudin, phenindione and acenocoumarol; 41) potassium
channel modulators such as nicorandil, cromakalim, diazoxide,
glibenclamide, levcromakalim, minoxidil and pinacidil; 42)
cholesterol-lowering drugs such as colestipol, colestyramine,
bezafibrate, fenofibrate, gemfibrozil, ciprofibrate, rosuvastatin,
simvastatin, fluvastatin, atorvastatin, pravastatin, ezetimibe,
ispaghula, nictotinic acid, acipimox and omega-3 triglycerides; 43)
diuretics such as bumetanide, furosemide, torasemide,
spironolactone, amiloride, bendroflumethiazide, chlortalidone,
metolazone, indapamide and cyclopenthiazide; 44) smoking cessation
drugs such as nicotine and bupropion; 45) bisphosphonates such as
alendronate sodium, sodium clodronate, etidronate disodium,
ibandronic acid, pamidronate disodium, isedronate sodium,
tiludronic acid and zoledronic acid; 46) dopamine agonists such as
amantadine, bromocriptine, pergolide, cabergoline, lisuride,
ropinerole, pramipexole and apomorphine; 47) nucleic-acid medicines
such as oligonucleotides, decoy nucleotides, antisense nucleotides
and other gene-based medicine molecules; 48) antipsychotics such
as: dopamine antagonists including chlorpromazine,
prochlorperazine, fluphenazine, trifluoperazine and thioridazine;
phenothiazines including aliphatic compounds, piperidines and
piperazines; thioxanthenes, butyrophenones and substituted
benzamides; atypical antipsychotics including clozapine,
risperidone, olanzapine, quetiapine, ziprasidone, zotepine,
amisulpride and aripiprazole; and 49) pharmaceutically acceptable
salts or derivatives of any of the foregoing.
[0055] In preferred embodiments of the present invention, the
active agent is heparin (fractionated and unfractionated),
apomorphine, clobazam, clomipramine or glycopyrrolate.
[0056] In addition, the active agents used in the present invention
may be small molecules, proteins, carbohydrates or mixtures
thereof.
[0057] The term co-milling is used herein to refer to a range of
methods, including co-micronising methods, some examples of which
are outlined below. In the prior art, co-milling or co-micronising
active agents or excipients with additive materials has been
suggested.
[0058] It is stated that milling can be used to substantially
decrease the size of particles of active agent. However, if the
particles of active agent are already fine, for example have a MMAD
of less than 20 .mu.m prior to the milling step, the size of those
particles may not be significantly reduced where the milling of
these active particles takes place in the presence of an additive
material. Rather, milling of fine active particles with additive
particles using the methods described in the prior art (for
example, in the earlier patent application published as WO
02/43701) will result in the additive material becoming deformed
and being smeared over or fused to the surfaces of the active
particles. The resultant composite active particles have been found
to be less cohesive following the milling treatment.
[0059] The prior art mentions two types of processes in the context
of co-milling or co-micronising active and additive particles.
First, there is the compressive type process, such as Mechanofusion
and the Cyclomix and related methods such as the Hybridiser or the
Nobilta. As the name suggests, Mechanofusion is a dry coating
process designed to mechanically fuse a first material onto a
second material. The first material is generally smaller and/or
softer than the second. The principles behind the Mechanofusion and
Cyclomix processes are distinct from those of alternative milling
techniques in that they have a particular interaction between an
inner element and a vessel wall, and in that they are based on
providing energy by a controlled and substantial compressive
force.
[0060] The fine active particles and the additive particles are fed
into the Mechanofusion driven vessel (such as a Mechanofusion
system (Hosokawa Micron Ltd)), where they are subject to a
centrifugal force which presses them against the vessel inner wall.
The inner wall and a curved inner element together form a gap or
nip in which the particles are pressed together. The powder is
compressed between the fixed clearance of the drum wall and a
curved inner element with high relative speed between drum and
element. As a result, the particles experience very high shear
forces and very strong compressive stresses as they are trapped
between the inner drum wall and the inner element (which has a
greater curvature than the inner drum wall). The particles are
pressed against each other with enough energy to locally heat and
soften, break, distort, flatten and wrap the additive particles
around the active particles to form coatings. The energy is
generally sufficient to break up agglomerates and some degree of
size reduction of both components may occur. Whilst the coating may
not be complete, the deagglomeration of the particles during the
process ensures that the coating may be substantially complete,
covering the majority of the surfaces of the particles.
[0061] These Mechanofusion and Cyclomix processes apply a high
enough degree of force to separate the individual particles of
active material and to break up tightly bound agglomerates of the
active particles such that effective mixing and effective
application of the additive material to the surfaces of those
particles is achieved.
[0062] An especially desirable aspect of the described co-milling
processes is that the additive material becomes deformed during the
milling and may be smeared over or fused to the surfaces of the
active particles. However, in practice, this compression process
produces little or no size reduction of the drug particles,
especially where they are already in a micronised form (i.e. <10
.mu.m). The only physical change which may be observed is a plastic
deformation of the particles to a rounder shape.
[0063] However the most preferred milling techniques include those
described in R. Pfeffer et al. "Synthesis of engineered
particulates with tailored properties using dry particle coating",
Powder Technology 117 (2001) 40-67. These include processes using
the MechanoFusion.RTM. machine, the Hybidizer.RTM. machine, the
Theta Composer.RTM., magnetically assisted impaction processes and
rotating fluidised bed coaters. Cyclomix methods may also be
used.
[0064] Preferably, the technique employed to apply the required
mechanical energy involves the compression of a mixture of
particles of the dispersing agent and particles of the
pharmaceutically active agent in a nip formed between two portions
of a milling machine, as is the case in the MechanoFusion.RTM. and
Cyclomix devices.
[0065] Some preferred milling methods will now be described in
greater detail:
MechanoFusion.RTM.:
[0066] As the name suggests, this dry coating process is designed
to mechanically fuse a first material onto a second material. The
first material is generally smaller and/or softer than the second.
The MechanoFusion and Cyclomix working principles are distinct from
alternative milling techniques in having a particular interaction
between inner element and vessel wall, and are based on providing
energy by a controlled and substantial compressive force.
[0067] The fine active particles and the particles of dispersing
agent are fed into the MechanoFusion driven vessel, where they are
subject to a centrifugal force and are pressed against the vessel
inner wall. The powder is compressed between the fixed clearance of
the drum wall and a curved inner element with high relative speed
between drum and element. The inner wall and the curved element
together form a gap or nip in which the particles are pressed
together. As a result the particles experience very high shear
forces and very strong compressive stresses as they are trapped
between the inner drum wall and the inner element (which has a
greater curvature than the inner drum wall). The particles
violently collide against each other with enough energy to locally
heat and soften, break, distort, flatten and wrap the particles of
dispersing agent around the core particle to form a coating. The
energy is generally sufficient to break up agglomerates and some
degree of size reduction of both components may occur. Embedding
and fusion of additive particles of dispersing agent onto the
active particles may occur, and may be facilitated by the relative
differences in hardness (and optionally size) of the two
components. Either the outer vessel or the inner element may rotate
to provide the relative movement. The gap between these surfaces is
relatively small, and is typically less than 10 mm and is
preferably less than 5 mm, more preferably less than 3 mm. This gap
is fixed, and consequently leads to a better control of the
compressive energy than is provided in some other forms of mill
such as ball and media mills. Also, in general, no impaction of
milling media surfaces is present so that wear and consequently
contamination are minimised. The speed of rotation may be in the
range of 200 to 10,000 rpm. A scraper may also be present to break
up any caked material building up on the vessel surface. This is
particularly advantageous when using fine cohesive starting
materials. The local temperature may be controlled by use of a
heating/cooling hacked built into the drum vessel walls. The powder
may be re-circulated through the vessel.
Cyclomix Method (Hosokawa Microm):
[0068] The cyclomix comprises a stationary conical vessel with a
fast rotating shaft with paddles which move close to the wall. Due
to the high rotational speed of the paddles, the powder is
propelled towards the wall, and as a result the mixture experiences
very high shear forces and compressive stresses between wall and
paddle. Such effects are similar to those in MechanoFusion as
described above and may be sufficient to locally heat and soften,
to break, distort, flatten and wrap the particles of dispersing
agent around the active particles to form a coating. The energy is
sufficient to break up agglomerates and some degree of size
reduction of both components may also occur depending on the
conditions and upon the size and nature of the particles.
Hybridiser.RTM. Method:
[0069] This is a dry process which can be described as a product
embedding or filming of one powder onto another. The fine active
particles and fine or ultra fine particles of dispersing agent are
fed into a conventional high shear mixer pre-mix system to form an
ordered mixture. This powder is then fed into the Hybridiser. The
powder is subjected to ultra-high speed impact, compression and
shear as it is impacted by blades on a high speed rotor inside a
stator vessel, and is re-circulated within the vessel. The active
and additive particles collide with each other. Typical speeds of
rotation are in the range of 5,000 to 20,000 rpm. The relatively
soft fine particles of dispersing agent experience sufficient
impact force to soften, break, distort, flatten and wrap around the
active particle to form a coating. There may also be some degree of
embedding into the surface of the active particles.
[0070] The second of the types of processes mentioned in the prior
art is the impact milling processes. Such impact milling is
involved, for example, in ball milling, jet milling and the use of
a homogeniser.
[0071] Ball milling is a milling method used in many of the prior
art co-milling processes. Centrifugal and planetary ball milling
are especially preferred methods.
[0072] Jet mills are capable of reducing solids to particle sizes
in the low-micron to submicron range. The grinding energy is
created by gas streams from horizontal grinding air nozzles.
Particles in the fluidised bed created by the gas streams are
accelerated towards the centre of the mill, colliding with slower
moving particles. The gas streams and the particles carried in them
create a violent turbulence and, as the particles collide with one
another, they are pulverized.
[0073] High pressure homogenisers involve a fluid containing the
particles being forced through a valve at high pressure, producing
conditions of high shear and turbulence. Suitable homogenisers
include EmulsiFlex high pressure homogenisers which are capable of
pressures up to 4000 bar, Niro Soavi high pressure homogenisers
(capable of pressures up to 2000 bar) and Microfluidics
Microfluidisers (maximum pressure 2750 bar).
[0074] Milling may, alternatively, involve a high energy media mill
or an agitator bead mill, for example, the Netzsch high energy
media mill, or the DYNO-mill (Willy A. Bachofen AG,
Switzerland).
[0075] All of these processes create high-energy impacts between
media and particles or between particles. In practice, while these
processes are good at making very small particles, it has been
found that the ball mill, jet mill and the homogenizer were not as
effective in producing dispersion improvements in resultant drug
powders as the compressive type processes. It is believed that the
impact processes discussed above are not as effective in producing
a coating of additive material on each particle as the compressive
type processes.
[0076] For the purposes of this invention, all forms of co-milling
and co-micronisation are encompassed, including methods that are
similar or related to all of those methods described above. For
example, methods similar to Mechanofusion are encompassed, such as
those utilizing one or more very high-speed rotors (i.e. 2000 to
50000 rpm) with blades or other elements sweeping the internal
surfaces of the vessels with small gaps between wall and blade
(i.e. 0.1 mm to 20 mm). Conventional methods comprising co-milling
active material with additive materials (as described in WO
02/43701) are also encompassed. These methods result in composite
active particles comprising ultra-fine active particles with an
amount of the additive material on their surfaces.
[0077] Thus, the milling methods used in the present invention are
simple and cheap compared to the complex previous attempts to
engineer particles, providing practical as well as cost benefits. A
further benefit associated with the present invention is that the
powder processing steps do not have to involve organic solvents.
Such organic solvents are common to many of the known approaches to
powder processing and are known to be undesirable for a variety of
reasons.
[0078] In the past, jet milling has been considered less attractive
for co-milling active and additive particles in the preparation of
powder formulations to be dispensed using passive devices, with
compressive processes like or related to Mechanofusion and
Cyclomixing being preferred. The collisions between the particles
in a jet mill are somewhat uncontrolled and those skilled in the
art, therefore, considered it unlikely that this technique would be
able to provide the desired deposition of a coating of additive
material on the surface of the active particles.
[0079] Moreover, it was believed that, unlike the situation with
compressive type processes such as Mechanofusion and Cyclomixing,
segregation of the powder constituents occurred in jet mills, such
that the finer particles, that were believed to be the most
effective, could escape from the process. In contrast, it could be
clearly envisaged how techniques such as Mechanofusion would result
in the desired coating.
[0080] However, more recently, jet milling has been shown to be an
attractive process for co-milling active and additive particles,
especially for preparing powder formulations that are to be used in
active devices (see the disclosure in the earlier patent
application published as WO 2004/001628).
[0081] It should also be noted that it was also previously believed
that the compressive or impact milling processes must be carried
out in a closed system, in order to prevent segregation of the
different particles. This has also been found to be untrue and the
co-milling processes used in the present invention do not need to
be carried out in a closed system. In an open system, the co-jet
milling has surprisingly been found not to result in the loss of
the small particles, even when using leucine as the additive
material. Leucine was previously considered to present something of
a problem when co-jet milled.
[0082] Further, co-jet milling at lower pressures can produce
powders which perform well in passive devices whilst powders milled
at higher pressures may perform better in active devices, such as
Aspirair.TM..
[0083] The co-milling processes can be specifically selected for
the active and carrier particles. For example, the active particles
may be co-jet milled or homogenized with the additive, whilst the
carrier particles may be mechanofused with the additive.
[0084] The co-milling processes according to the present invention
may be carried out in two or more stages, to provide beneficial
effects. Various combinations of types of co-milling and/or
additive material may be used, in order to obtain advantages.
Within each step, multiple combinations of co-milling and other
processing steps may be used.
[0085] For example, milling at different pressures and/or different
types of milling or blending processes may be combined. The use of
multiple steps allows one to tailor the properties of the milled
particles to suit a particular inhaler device, a particular drug
and/or to target particular parts of the lung.
[0086] In one embodiment of the present invention, the milling
process is a two-step process comprising first jet milling the drug
on its own at suitable grinding pressure to obtain the required
particle sizes. Next, the milled drug is co-milled with an additive
material. Preferably, this second step is carried out at a lower
grinding pressure, so that the effect achieved is the coating of
the small active particles with the additive material. This
two-step process may produce better results than simply co-milling
the active material and additive material at a high grinding
pressure.
[0087] The same type of two-step milling process can be carried out
with the carrier particles, although these particles, as a rule, do
not have to be milled to such small particle sizes.
[0088] In another embodiment of the present invention, the
composite particles, which may optionally have been produced using
the two-step co-milling process discussed above, subsequently
undergo Mechanofusion. This final Mechanofusion step may "polish"
the composite particles, further rubbing the additive material into
the particles. This provides beneficial properties afforded by
Mechanofusion, in combination with the very small particles sizes
made possible by the co-jet milling. Such an additional
Mechanofusion step is particularly attractive for composite active
particles, especially where they are very small.
[0089] The reduction in particle size may be increased by carrying
out the co-jet milling at lower temperatures. Whilst the co-jet
milling process may be carried out at temperatures between
-20.degree. C. and 40.degree. C., the particles will tend to be
more brittle at lower temperatures and they therefore fracture more
readily so that the milled particles tend to be even smaller.
Therefore, in another embodiment of the present invention, the jet
milling is carried out at temperatures below room temperature,
preferably at a temperature below 10.degree. C., more preferably at
a temperature below 0.degree. C.
[0090] The benefits of the methods according to the present
invention are illustrated by the experimental data set out
below.
COMPARATIVE EXAMPLES
Example 1
Mechanofused Budesonide with Magnesium Stearate
[0091] This example studied magnesium stearate processed with
budesonide. The blends were prepared by Mechanofusion using the
Hosokawa AMS-MINI, with blending being carried out for 60 minutes
at approximately 4000 rpm.
[0092] The magnesium stearate used was a standard grade supplied by
Avocado Research Chemicals Ltd. The drug used was micronised
budesonide. The powder properties were tested using the Miat
Monohaler.
[0093] Blends of budesonide and magnesium stearate were prepared at
different weight percentages of magnesium stearate. Blends of 5%
w/w and 10% w/w, were prepared and then tested. MSLIs and TSIs were
carried out on the blends. The results, which are summarised below,
indicate a high aerosolisation efficiency. However, this powder had
poor flow properties, and was not easily handled, giving high
device retention.
TABLE-US-00001 FPF FPD ED Formulation (ED) (mg) (mg) Method
Budesonide:magnesium 73% 1.32 1.84 MSLI stearate (5% w/w)
Budesonide:magnesium 80% 1.30 1.63 TSI stearate (10% w/w)
Example 2
Mechanofused Budesonide with Fine Lactose and Magnesium
Stearate
[0094] A further study was conducted to look at the Mechanofusion
of a drug with both a force control agent and fine lactose
particles. The additive or force control agent used was magnesium
stearate (Avocado) and the fine lactose was Sorbolac 400 (Meggle).
The drug used was micronised budesonide.
[0095] The blends were prepared by Mechanofusion of all three
components together using the Hosokawa AMS-MINI, blending was
carried out for 60 minutes at approximately 4000 rpm.
[0096] Formulations were prepared using the following
concentrations of budesonide, magnesium stearate and Sorbolac 400:
[0097] 5% w/w budesonide, 6% w/w magnesium stearate, 89% w/w
Sorbolac 400; and [0098] 20% w/w budesonide, 6% w/w magnesium
stearate, 74% w/w Sorbolac 400.
[0099] TSIs and MSLIs were performed on the blends. The results,
which are summarised below, indicate that, as the amount of
budesonide in the blends increased, the FPF results increased.
Device and capsule retention were notably low in these dispersion
tests (<5%), however a relatively large level of magnesium
stearate was used and this was applied over the entire
composition.
TABLE-US-00002 FPF (ED) FPF (ED) Formulation (TSI) (MSLI) 5:6:89
66.0% 70.1% 20:6:74 75.8% --
[0100] As an extension to this work, different blending methods of
budesonide, magnesium stearate and Sorbolac 400 were investigated
further. Two formulations were prepared in the Glen Creston
Grindomix. This mixer is a conventional food-processor style bladed
mixer, with 2 parallel blades.
[0101] The first of these formulations was a 5% w/w budesonide, 6%
w/w magnesium stearate, 89% w/w Sorbolac 400 blend prepared by
mixing all components together at 2000 rpm for 20 minutes. The
formulation was tested by TSI and the results, when compared to
those for the mechanofused blends, showed the Grindomix blend to
give lower FPF results (see table below).
[0102] The second formulation was a blend of 90% w/w of
mechanofused magnesium stearate:Sorbolac 400 (5:95) pre-blend and
10% w/w budesonide blended in the Grindomix for 20 minutes. The
formulation was tested by TSI and MSLI.
[0103] It was also observed that this formulation had notably good
flow properties for a material comprising such fine particles. This
is believed to be associated with the Mechanofusion process.
TABLE-US-00003 FPF (ED) FPF Formulation (TSI) (MSLI) Grindomix
5:6:89% 57.7 -- Grindomix 10% budesonide 65.9 69.1 (Mechanofused
pre-blend)
Example 3
Mechanofused Salbutamol with Fine Lactose and Magnesium
Stearate
[0104] A further study was conducted to look at the Mechanofusion
of an alternative drug with both a force control agent and fine
lactose particles. The additive or force control agent used was
magnesium stearate and the fine lactose was Sorbolac 400 (Meggle).
The drug used was micronised salbutamol sulphate. The blends were
prepared by Mechanofusion using the Hosokawa AMS-MINI, blending for
10 minutes at approximately 4000 rpm.
[0105] Formulations prepared were: [0106] 20% w/w salbutamol, 5%
w/w magnesium stearate, 75% w/w Sorbolac 400; and [0107] 20% w/w
salbutamol, 2% w/w magnesium stearate, 78% w/w Sorbolac 400.
[0108] NGIs were performed on the blends and the results are set
out below. Device and capsule retention were again low in these
dispersion tests (<10%).
TABLE-US-00004 Formulation FPF (ED) FPF (ED) 20:5:75 80% 74%
20:2:78 78% 70%
Example 4
Preparation of Mechanofused Formulation for Use in a Passive
Device
[0109] 20 g of a mix comprising 20% micronised clomipramine, 78%
Sorbolac 400 (fine lactose) and 2% magnesium stearate were weighed
into the Hosokawa AMS-MINI Mechanofusion system via a funnel
attached to the largest port in the lid with the equipment running
at 3.5%. The port was sealed and the cooling water switched on. The
equipment was run at 20% for 5 minutes followed by 80% for 10
minutes. The equipment was switched off, dismantled and the
resulting formulation recovered mechanically.
[0110] 20 mg of the collected powder formulation was filled into
size 3 capsules and fired from a Miat Monohaler into an NGI. The
FPF measured was good, being greater than 70%.
[0111] The data above suggest that magnesium stearate content in
the region 5-20% yielded the greatest dispersibility. Above these
levels, experience suggests significant sticking inside the device
could occur, and the quantities used became unnecessary for further
performance improvement.
[0112] Fine particle fraction values were consistently obtained in
the range 50 to 60%, and doubled in comparison with controls
containing no magnesium stearate.
EXAMPLES OF THE INVENTION
Example 5
Mechanofused Apomorphine and Mechanofused Fine Lactose
[0113] Firstly, 15 g of micronised apomorphine and 0.75 g leucine
are weighed into the Hosokawa AMS-MINI Mechanofusion system via a
funnel attached to the largest port in the lid with the equipment
running at 3.5%. The port is sealed and the cooling water switched
on. The equipment is run at 20% for 5 minutes followed by 80% for
10 minutes. The equipment is then switched off, dismantled and the
resulting formulation recovered mechanically.
[0114] Next, 19 g of Sorbolac 400 lactose and 1 g leucine are
weighed into the Hosokawa AMS-MINI Mechanofusion system via a
funnel attached to the largest port in the lid with the equipment
running at 3.5%. The port is sealed and the cooling water switched
on. The equipment is run at 20% for 5 minutes followed by 80% for
10 minutes. The equipment is switched off, dismantled and the
resulting formulation recovered mechanically.
[0115] 4.2 g of the apomorphine-based material and 15.8 g of the
Sorbolac-based material are combined in a high shear mixer for 5
minutes, and the resulting powder is then passed through a 300
micron sieve to form the final formulation. 2 mg of the powder
formulation are filled into blisters and fired from an Aspirair
device into an NGI. An FPF of over 50% was obtained with MMAD 1.5
microns, illustrating this system gave a very good dispersion. The
device retention was also very low, with only 10% left in the
device and 7% in the blister.
Example 6
Mechanofused Clomipramine and Mechanofused Fine Lactose
[0116] Firstly, 20 g of a mix comprising 95% micronised
clomipramine and 5% magnesium stearate are weighed into the
Hosokawa AMS-MINI Mechanofusion system via a funnel attached to the
largest port in the lid with the equipment running at 3.5%. The
port is sealed and the cooling water switched on. The equipment is
run at 20% for 5 minutes followed by 80% for 10 minutes. The
equipment is then switched off, dismantled and the resulting
formulation recovered mechanically.
[0117] Next, 20 g of a mix comprising 99% Sorbolac 400 lactose and
1% magnesium stearate are weighed into the Hosokawa AMS-MINI
Mechanofusion system via a funnel attached to the largest port in
the lid with the equipment running at 3.5%. The port is sealed and
the cooling water switched on. The equipment is run at 20% for 5
minutes followed by 80% for 10 minutes. The equipment is switched
off, dismantled and the resulting formulation recovered
mechanically.
[0118] 4 g of the clomipramine-based material and 16 g of the
Sorbolac-based material are combined in a high shear mixer for 10
minutes, to form the final formulation.
[0119] 20 mg of the powder formulation are filled into size 3
capsules and fired from a Miat Monohaler into an NGI.
Example 7
Mechanofused Theophylline and Mechanofused Fine Lactose
[0120] Firstly, 20 g of a mix comprising 95% micronised
theophylline and 5% magnesium stearate are weighed into the
Hosokawa AMS-MINI Mechanofusion system via a funnel attached to the
largest port in the lid with the equipment running at 3.5%. The
port is sealed and the cooling water switched on. The equipment is
run at 20% for 5 minutes followed by 80% for 10 minutes. The
equipment is then switched off, dismantled and the resulting
formulation recovered mechanically.
[0121] Next, 20 g of a mix comprising 99% Sorbolac 400 lactose and
1% magnesium stearate are weighed into the Hosokawa AMS-MINI
Mechanofusion system via a funnel attached to the largest port in
the lid with the equipment running at 3.5%. The port is sealed and
the cooling water switched on. The equipment is run at 20% for 5
minutes followed by 80% for 10 minutes. The equipment is switched
off, dismantled and the resulting formulation recovered
mechanically.
[0122] 4 g of the theophylline-based material and 16 g of the
Sorbolac-based material are combined in a high shear mixer for 10
minutes, to form the final formulation. 20 mg of the powder
formulation are filled into size 3 capsules and fired from a Miat
Monohaler into an NGI.
[0123] The active agent used in this example, theophylline, may be
replaced by other phosphodiesterase inhibitors, including
phosphodiesterase type 3, 4 or 5 inhibitors, as well as other
non-specific ones.
Example 8
Jet Milled Clomipramine and Mechanofused Fine Lactose
[0124] 20 g of a mix comprising 95%/micronised clomipramine and 5%
magnesium stearate are co-jet milled in a Hosokawa AS50 jet
mill.
[0125] 20 g of a mix comprising 99% Sorbolac 400 (fine lactose) and
1% magnesium stearate are weighed into the Hosokawa AMS-MINI
Mechanofusion system via a funnel attached to the largest port in
the lid with the equipment running at 3.5%. The port is sealed and
the cooling water switched on. The equipment is run at 20% for 5
minutes followed by 80% for 10 minutes. The equipment is switched
off, dismantled and the resulting formulation recovered
mechanically.
[0126] 4 g of the clomipramine-based material and 16 g of the
Sorbolac-based material are combined in a high shear mixer for 10
minutes, to form the final formulation.
[0127] 20 mg of the powder formulation are filled into size 3
capsules and fired from a Miat Monohaler into an NGI.
[0128] A number of micronised drugs were co-jet milled with
magnesium stearate for the purposes of replacing the clomipramine
in this example. These micronised drugs included budesonide,
formoterol, salbutamol, glycopyrrolate, heparin, insulin and
clobazam. Further compounds are considered suitable, including the
classes of active agents and the specific examples listed
above.
Example 9
Jet Milled Bronchodilator and Mechanofused Fine Lactose
[0129] 20 g of a mix comprising 95% micronised bronchodilator drug
and 5% magnesium stearate are co-jet milled in a Hosokawa AS50 jet
mill.
[0130] 20 g of a mix comprising 99% Sorbolac 400 lactose and 1%
magnesium stearate are weighed into the Hosokawa AMS-MINI
Mechanofusion system via a funnel attached to the largest port in
the lid with the equipment running at 3.5%. The port is sealed and
the cooling water switched on. The equipment is run at 20% for 5
minutes followed by 80% for 10 minutes. The equipment is switched
off, dismantled and the resulting formulation recovered
mechanically.
[0131] 4 g of the drug based material and 16 g of the Sorbolac
based material are combined in a high shear mixer for 10 minutes,
to form the final formulation.
[0132] 20 mg of the powder formulation is filled into size 3
capsules and fired from a Miat Monohaler into an NGI.
[0133] The results of these experiments are expected to show that
the powder formulations prepared using the method according to the
present invention exhibit further improved properties such as FPD,
FPF, as well as good flow and reduced device retention and throat
deposition.
[0134] In accordance with the present invention, the % w/w of
additive material will typically vary. Firstly, when the additive
material is added to the drug, the amount used is preferably in the
range of 0.1% to 50%, more preferably 1% to 20%, more preferably 2%
to 10%, and most preferably 3 to 8%. Secondly, when the additive
material is added to the carrier particles, the amount used is
preferably in the range of 0.01% to 30%, more preferably of 0.1% to
10%, preferably 0.2% to 5%, and most preferably 0.5% to 2%. The
amount of additive material preferably used in connection with the
carrier particles will be heavily dependant upon the size and hence
surface area of these particles.
Example 10
Lactose Study
[0135] A study was conducted to characterize the changes in the
properties of fine carrier particles, and of ultra-fine drug
particles, when they are co-milled with an additive material.
[0136] Micronised ultra-fine lactose was selected as a model for a
drug, as it is readily available in a micronised form and it
carries a reduced hazard compared to handling pharmaceutically
active substances. Ultra-fine lactose is also regarded as a
particularly cohesive material, hence improving its dispersibility
represents a severe challenge.
[0137] Meggle Sorbolac 400 and Meggle Extra Fine were selected as
the fine carrier grades, as these are readily available. However
other lactose grades can be used, such as those produced by DMV,
Borculo, Foremost and other suppliers, or a grade custom-made for
the purpose, as long as it conforms to the size range
indicated.
[0138] The literature reveals various possible types of tests,
including measuring powder flow, powder cohesion, powder shear and
powder dustiness.
[0139] In the first instance, several basic powder characteristics
were tested. These were porosity and surface area using the Coulter
SA 3100 BET system, and particle size, which was measured using a
Mastersizer 2000, manufactured by Malvern Instruments, Ltd.
(Malvern, UK). This was followed by examining several standard
powder properties using the Hosokawa Powder Tester.
Porosity
[0140] The powder porosity was measured using the Coulter SA 3100
BET system, with the following results.
TABLE-US-00005 Total pore volume Sample (ml/g) Sorbolac 0.0027
Mechanofused Sorbolac (60 mins) 0.0044 Mechanofused Sorbolac and
magnesium 0.0056 stearate (98:2) (60 mins) Mechanofused Sorbolac
and magnesium 0.0052 stearate (95:5) (60 mins)
[0141] The microporosity of the lactose particles is also shown in
the graph of FIG. 1.
[0142] Whilst the total pore volume does increase significantly
upon processing, insufficient differences are seen in the different
pore sizes to use porosity testing as a measure of the process.
Therefore, Malvern particle sizing of a wet powder dispersion was
also conducted. The results are summarised below.
TABLE-US-00006 Surface Malvern Sample Area (m.sup.2/g) d.sub.50
(.mu.m) Sorbolac 1.023 8.760 Magnesium Stearate 13.404 9.145
Mechanofused Sorbolac (60 mins) 1.189 7.525 Mechanofused Sorbolac
and magnesium 1.562 8.191 stearate (98:2) (0 mins) Mechanofused
Sorbolac and magnesium 1.496 9.112 stearate (98:2) (60 mins)
Mechanofused Sorbolac and magnesium 2.028 8.281 stearate (95:5) (0
mins) Mechanofused Sorbolac and magnesium 0.961 8.551 stearate
(95:5) (60 mins) Extra fine lactose 0.798 16.523 Mechanofused Extra
fine lactose (60 mins) 0.714 18.139 Mechanofused Extra fine lactose
and 1.195 17.703 magnesium stearate (98:2) (60 mins) Cyclomixed
Sorbolac (60 mins) 1.629 7.894 Cyclomixed Sorbolac and magnesium
stearate 1.617 (98:2) (0 mins) Cyclomixed Sorbolac and magnesium
stearate 1.473 (98:2) (5 mins) Cyclomixed Sorbolac and magnesium
stearate 1.442 (98:2) (10 mins) Cyclomixed Sorbolac and magnesium
stearate 1.383 (98:2) (20 mins) Cyclomixed Sorbolac and magnesium
stearate 1.404 (98:2) (40 mins) Cyclomixed Sorbolac and magnesium
stearate 1.425 (98:2) (60 mins) Cyclomixed Sorbolac and magnesium
stearate 1.779 (95:5) (0 mins)
[0143] Whilst the surface area does decrease as the processing time
increased, this can probably be explained as being due to the
magnesium stearate becoming smeared over the surface.
Hosokawa Powder Tester
[0144] This system measures several different parameters,
including: angle of repose; aerated bulk density; packed bulk
density; angle of spatula before and after impact; angle of fall;
and dispersibility.
[0145] The system then calculates further parameters/indices,
including: angle of difference (repose-fall); compressibility
(Carrs index); average angle of spatula; and uniformity (based on
d.sub.10 and d.sub.60).
[0146] Various powders were tested using this system and the
resulting data are summarised in Tables 1 to 5, shown in FIGS. 2 to
6 respectively.
[0147] As can be seen from the data, on processing with magnesium
stearate (MgSt), virtually all of the powders showed a tendency to
decrease the angle of repose and the angle of fall, and to increase
in bulk density and dispersibility.
[0148] For the Sorbolac 400 and the ultra-fine lactose, which are
within the size range considered suitable for use as the carrier
according to the present invention, the powders mechnofused with
magnesium stearate show very considerable drops in the angle of
repose and the angle of fall, as well as increases in aerated bulk,
compared to the raw material (see Tables 1 and 2). Where the powder
is mixed using a low shear mix, in this study a Turbula mixer was
used, none of these changes are observed (see Table 1).
[0149] Table 3 shows Sorbolac 400 Cyclomixed with magnesium
stearate. In these examples, considerable drops in the angle of
repose and the angle of fall are observed, as well as increases in
aerated bulk density. However, these changes are generally slightly
less than those observed when the Sorbolac 400 and magnesium
stearate are mechanofused. This is consistent with the increasing
intensity of the processing methods producing increasing levels of
effect.
[0150] Table 4 shows micronised lactose, which in these tests is
used to represent a model micronised drug. Unfortunately, the
variability of the results was higher and the data provided,
especially for the angle of repose, the angle of fall for the raw
material, was regarded as unreliable. The density increased but was
still relatively low. These powders were observed as being highly
cohesive. Even after Mechanofusion only slight improvements were
seen, in contrast to the dramatic visible powder changes for
Sorbolac 400 and the ultra-fine lactose.
[0151] Table 5 shows SV003, a traditional large lactose carrier
material. In this case, the powder mechanofused with magnesium
stearate shows smaller drops in the angle of repose and no change
in the angle of fall (where it remains at an already low level in
its original state). Similarly, the aerated bulk density increased
slightly, but from an already high level.
[0152] Thus, the results indicate that the co-milled carrier
particles within the preferred size range for the present invention
and co-milled model drug particles showed a tendency to decrease in
angle of repose, to increase in bulk density and to increase in
dispersibility. These properties would be anticipated in
conjunction with reduced cohesion. This improvement was observed to
increase with increasing intensity of the co-milling methods and
with increasing levels of additive material (magnesium stearate).
The result is an improvement in performance of a formulation
containing this carrier in an inhaler, in terms of improved emitted
dose and in terms of improved fine particle dose, especially the
fine particle dose of metered dose.
[0153] The metered dose (MD) of a dry powder formulation is the
total mass of active agent present in the metered form presented by
the inhaler device in question. For example, the MD might be the
mass of active agent present in a capsule for a Cyclohaler.TM., or
in a foil blister in a Gyrohaler.TM. device.
[0154] The emitted dose (ED) is the total mass of the active agent
emitted from the device following actuation. It does not include
the material left on the internal or external surfaces of the
device, or in the metering system including, for example, the
capsule or blister. The ED is measured by collecting the total
emitted mass from the device in an apparatus frequently identified
as a dose uniformity sampling apparatus (DUSA), and recovering this
by a validated quantitative wet chemical assay (a gravimetric
method is possible, but this is less precise).
[0155] The fine particle dose (FPD) is the total mass of active
agent which is emitted from the device following actuation which is
present in an aerodynamic particle size smaller than a defined
limit. This limit is generally taken to be 5 .mu.m if not expressly
stated to be an alternative limit, such as 3 .mu.m, 2 .mu.m or 1
.mu.m, etc. The FPD is measured using an impactor or impinger, such
as a twin stage impinger (TSI), multi-stage impinger (MSI),
Andersen Cascade Impactor (ACI) or a Next Generation Impactor
(NGI). Each impactor or impinger has a pre-determined aerodynamic
particle size collection cut points for each stage. The FPD value
is obtained by interpretation of the stage-by-stage active agent
recovery quantified by a validated quantitative wet chemical assay
(a gravimetric method is possible, but this is less precise) where
either a simple stage cut is used to determine FPD or a more
complex mathematical interpolation of the stage-by-stage deposition
is used.
[0156] The fine particle fraction (FPF) is normally defined as the
FPD divided by the ED and expressed as a percentage. Herein, the
FPF of ED is referred to as FPF(ED) and is calculated as
FPF(ED)=(FPD/ED).times.100%.
[0157] The fine particle fraction (FPF) may also be defined as the
FPD divided by the MD and expressed as a percentage. Herein, the
FPF of MD is referred to as FPF(MD), and is calculated as
FPF(MD)=(FPD/MD).times.100%.
Flodex Measurement
[0158] A means of assessing powder flow is to use the Flodex.TM.
powder tester (Hansen Research).
[0159] The Flodex provides an index, over a scale of 4 to 40 mm, of
flowability of powders. The analysis may be conducted by placing 50
g of a formulation into the holding chamber of the Flodex via a
funnel, allowing the formulation to stand for 1 minutes, and then
releasing the trap door of the Flodex to open an orifice at the
base of the holding chamber. Orifice diameters of 4 to 34 mm can be
used to measure the index of flowability. The flowability of a
given formulation is determined as the smallest orifice diameter
through which flow of the formulation is smooth.
Carr's Index
[0160] A formulation may be characterised by its
density/flowability parameters and uniformity of distribution of
the active ingredient. The apparent volume and apparent density can
be tested according to the method described in the European
Pharmacopoeia (Eur. Ph.).
[0161] Powder mixtures (100 g) are poured into a glass graduated
cylinder and the unsettled apparent volume V.sub.0 is read; the
apparent density before settling (dv) was calculated dividing the
weight of the sample by the volume V.sub.0. After 1250 taps with
the described apparatus, the apparent volume after settling
(V.sub.1250) is read and the apparent density after settling (ds)
was calculated. The flowability properties were tested according to
the method described in the Eur. Ph.
[0162] Powder mixtures (about 110 g) are then poured into a dry
funnel equipped with an orifice of suitable diameter that is
blocked by suitable means. The bottom opening of the funnel is
unblocked and the time needed for the entire sample to flow out of
the funnel recorded. The flowability is expressed in seconds and
tenths of seconds related to 100 g of sample.
[0163] The flowability can also be evaluated from the Carr's index
calculated according to the following formula: Carr's index
(%)=((ds-dv)/ds).times.100
[0164] A Carr index of less than 25 is usually considered
indicative of good flowability characteristics.
[0165] The uniformity of distribution of the active ingredient may
be evaluated by withdrawing 10 samples, each equivalent to about a
single dose, from different parts of the blend. The amount of
active ingredient of each sample can be determined by
High-Performance Liquid Chromatography (HPLC).
Determination of the Aerosol Performances
[0166] An amount of powder for inhalation may be tested by loading
it into a dry powder inhaler and firing the dose into an impactor
or impinger, using the methods as defined in the European or US
Pharmacopoeias.
SEM
[0167] This is a potentially useful method which may be used to
identify powders exhibiting low cohesion, large magnesium stearate
agglomerates, and changes in surface morphology following
processing and/or segregation.
Differential Scanning Calorimetry (DSC) & Inverse Gas
Chromatography (IGC)
[0168] These techniques may be useful for quantifying the surface
energy and production of amorphous material during the processing
of the powder particles. Amorphous material is regarded as
potentially harmful to the long-term stability of powder
formulations, making them prone to recrystallisation.
[0169] Powder characterisation parameters such as flowability
indices or forms of surface characterisation have been considered.
The Hosokawa Powder Tester provided a good test to qualify changes
in powder properties. The mechanofused powders showed a tendency to
decrease in angle of repose, increase in bulk density and increase
in dispersibility. However, as the particles approach the micron
size, these Hosokawa Powder Tester tests were less equivocal. Also,
these parameters may not be directly linked to performance during
aerosolisation.
[0170] As well as characterizing the drug and fine carrier
component powders, these Hosokawa Powder Tester tests are also
helpful in characterizing the final combined formulation, where the
final formulation properties are advantageously similar to the
properties of the co-milled fine carrier. Consequently, the
combined formulation will have good flow properties and provide low
device retention.
[0171] Further, the good dispersibility of the drug component is
retained, providing high levels of fine particle fraction and fine
particle dose, as measured by standard in vitro tests. Such
improvements are also consistent, providing less variability in the
test results obtained than for traditional formulation
approaches.
[0172] Another very important advantage of the system of the
present invention is the consistency of the high performance. One
of the many benefits of consistency is that it can also lead to
reduction in adverse side effects experienced, as it will allow one
to administer a smaller total dose than is possible when relying
upon conventional levels of inhaler efficiency or other routes of
administration. In particular, it allows one to target specific
dosing windows wherein the therapeutic effect is maximised whilst
causing the minimum side effects.
[0173] According to a second aspect of the present invention,
formulations which are obtainable by the methods according to the
first aspect of the invention are provided.
[0174] In powder compositions of the present invention, at least
some of the composite particles may be in the form of agglomerates,
preferably unstable agglomerates. However, when the composite
active particles are included in a pharmaceutical composition, the
additive material promotes the dispersal of the composite active
particles on administration of that composition to a patient, via
actuation of an inhaler. In the turbulence created upon actuation
of the inhaler device, the agglomerates break up, releasing the
composite particles of respirable size.
[0175] The powder particles according to the present invention,
which may be prepared as described herein, are not "low density"
particles, as tend to be favoured in the prior art. Such low
density particles can be difficult and expensive to prepare.
Indeed, previously, those skilled in the art have only reported
high performance in connection with powder particles that have been
prepared using fancy processing techniques such as complex spray
drying, which result in low density particles. In contrast, the
particles of the present invention are made using very simple and
economical processes.
[0176] In contrast to the suggestion in the prior art, it may be
advantageous not to produce severely dimpled or wrinkled particles
as these can yield low density powders, with very high voidage
between particles. Such powders have been reported as having good
flow and dispersion characteristics, but they occupy a large volume
relative to their mass as a consequence of their shape and can
result in packaging problems, i.e. require much larger blisters or
capsules to hold a given mass of powder.
[0177] In one embodiment of the present invention, the powders have
a tapped density of at least 0.1 g/cc, at least 0.2 g/cc, at least
0.3 g/cc, at least 0.4 g/cc or at least 0.5 g/cc.
Example 11
Surface Chemical Analysis of Powders
[0178] The aim of the analysis is to identify the presence of
magnesium stearate on the surface of a model co-micronised powder.
The model powders were processed in two different ways, with one
representing a conventional pharmaceutical blending process, and
the other being the intensive Mechanofusion process which is the
subject of the invention. The aim was to show the contrast in
surface coating efficiency. In this case the model material was
micronised lactose, which could represent a micronised drug or a
fine carrier.
[0179] The powders have been analyzed using both TOF-SIMS and XPS.
TOF-SIMS provides a mass spectrum of the outermost 1 nm of the
surface, and is used here to assess whether the magnesium stearate
coverage of the lactose is complete or in patches. XPS provides a
spectrum representative of the outermost 10 nm of the surface of
the sample and is used here in comparison to the TOF-SIMS data to
assess the depth of coverage of the magnesium stearate on the
lactose surface. In addition, the powders were studied using the
Zetasizer 3000HS instrument (Malvern Instruments Ltd, UK.) Each
sample was tested in cyclohexane, and zeta potential measurements
were obtained.
[0180] The following powder samples were prepared for testing:
[0181] Lactose; [0182] Lactose/Magnesium Stearate 19/1 mixed by
Turbula mixer; and [0183] Lactose/Magnesium Stearate 19/1 mixed by
Mechanofusion.
TOF-SIMS
[0184] SIMS is a qualitative surface analytical technique that is
capable of producing a high-resolution mass spectrum of the
outermost 1 nm of a surface.
[0185] In brief, the SIMS process involves bombarding the sample
surface with a beam of primary ions (for example caesium or
gallium). Collision of these ions with atoms and molecules in the
surface results in the transfer of energy to them, causing their
emission from the surface. The types of particles emitted from the
surface include positive and negative ions (termed secondary ions),
neutral species and electrons. Only secondary ions are measured in
SIMS. Depending on the type of bias applied to the sample, either
positive or negative ions are directed towards a mass spectrometer.
These ions are then analysed in terms of their mass-to-charge ratio
(m/z) yielding a positive or negative ion mass spectrum of counts
detected versus m/z. Different fragments will be diagnostic of
different components of the surface. TOF-SIMS is an advanced
technique that has increased sensitivity (<<parts per million
(ppm) sensitivity), mass resolution and mass range compared to
conventional SIMS techniques. SIMS operating in static mode was
used to determine the chemical composition of the top monolayer of
the surface. Under static SIMS conditions, the primary ion dose is
limited so that statistically the sample area analysed by the
rastered ion beam is exposed to the beam once only, and that the
spectrum generated is representative of a pristine surface.
[0186] TOF-SIMS analysis of the Turbula mixed sample
(Lactose/Magnesium Stearate 19/1 mixed by Turbula) indicated the
presence of both lactose and magnesium stearate in both positive
and negative mass spectra, as shown in the table below. The
presence of lactose in the spectra indicates that the surface
coverage of magnesium stearate is incomplete.
[0187] TOF-SIMS analysis of the Mechanofusion mixed sample
(Lactose/Magnesium Stearate 19/1 co-milled by Mechanofusion) also
indicated the presence of both lactose and magnesium stearate in
both positive and negative mass spectra. The presence of lactose in
the spectra indicates that the surface coverage of magnesium
stearate is incomplete.
[0188] It is important to note that SIMS spectra are not
quantitative and so the intensities of the peaks cannot be taken to
reflect the degree of surface coverage.
XPS
[0189] XPS is a surface analytical technique that can quantify the
amount of different chemical species in the outermost 10 nm of a
surface. In the simplest form of analysis, XPS measures the
relative amount of each element present. Quantitative elemental
identification can be achieved down to 1 atom in 1000. All elements
present can be detected with the exception of hydrogen. Elemental
analysis may be essential in determining the amount of a surface
contaminant or to quantify any surface species with a unique
elemental type.
TABLE-US-00007 Relative Atomic Percentage Composition (%) Sample C
O Mg Lactose Measurement 1 54.47 45.43 Nd* Measurement 2 55.29
44.71 Nd* Mean 54.9 45.1 <0.1 Lactose/Magnesium Stearate
(Turbula) Measurement 1 61.23 38.00 0.44 Measurement 2 60.40 39.02
0.50 Mean 60.8 38.5 0.5 Lactose/Magnesium Stearate (Mechanofusion)
Measurement 1 81.39 17.07 1.51 Measurement 2 80.72 17.80 1.49 Mean
81.1 17.4 1.5 *Nd = not detected (<0.1 atomic %)
[0190] XPS analysis of the Lactose/Magnesium Stearate 19/1 sample
mixed by Turbula revealed the presence of magnesium on the surface
of the lactose indicating the presence of magnesium stearate. Using
the percentage presence of magnesium on the surface it is
calculated that the magnesium stearate contributes 20% of the
overall signal from the outermost 10 nm of the sample surface. Peak
fitting the carbon 1 s envelope enables the identification and
quantification of the functionalities present at the surface. The
clear increase in C--H/C--C carbon centres at the surface is
ascribed to the coverage of magnesium stearate and demonstrates a
similar degree of signal intensity to that predicted from the
magnesium abundance.
[0191] XPS analysis of the Lactose/Magnesium Stearate 19/1
Mechanofusion mixed sample again demonstrates the presence of
magnesium stearate on the lactose surface by both the magnesium
abundance and the increase in C--C/C--H functionality over that
seen on pure lactose. Using the percentage of magnesium in the
spectrum the magnesium stearate is calculated to contribute 61.5%
of the signal from the outermost 10 nm of the sample surface. An
increase of similar magnitude is observed for the C--C/C--H
coverage.
[0192] The carboxyl functionality present on the surface of the
lactose can most likely be attributed to surface contamination, and
as such the carboxyl group is not used to assess the degree of
magnesium stearate coverage. However for the two mixed samples the
extent of carboxyl functionality follows the same trend as for
magnesium and the C--C/C--H increases.
[0193] The Mechanofusion mixed sample demonstrated significantly
increased amounts of magnesium stearate at the surface, over the
Turbula mixed sample. These differences could reflect either a
thickening of the coverage of magnesium stearate or an increased
surface coverage given the incomplete coverage as demonstrated by
TOF-SIMS analysis.
TABLE-US-00008 Area % of C 1 s Spectral Envelope Sample C--C C--O
O--C--O O--C.dbd.O Lactose Measurement 1 6.4 70.9 18.0 4.7
Measurement 2 4.4 57.8 22.0 12.8 Mean 5.5 64.3 20.0 8.7
Lactose/Magnesium Stearate (Turbula) Measurement 1 25.8 57.5 14.7
2.1 Measurement 2 24.7 58.8 15.0 1.6 Mean 25.2 58.1 14.8 1.8
Lactose/Magnesium Stearate (Mechanofusion) Measurement 1 75.7 16.1
3.9 4.3 Measurement 2 73.9 17.2 4.5 4.5 Mean 74.8 16.6 4.2 4.4
[0194] In conclusion both mixed samples demonstrate an incomplete
coverage of magnesium stearate, but with about three times more
magnesium stearate present on the Mechanofusion mixed sample than
the Turbula sample in the top 10 nm of the surface.
Zeta Potential
[0195] Zetasizer measures the zeta potential. This is a measure of
the electric potential on a particle in suspension in the
hydrodynamic plane of shear. The results are summarized as
follows:
TABLE-US-00009 Zeta Sample Potential (mV) Lactose 35.5
Lactose/Magnesium Stearate 4.8 (19/1) (Turbula) Lactose/Magnesium
Stearate -34.8 (19/1) (Mechanofusion)
[0196] Each result is an average of 10 measurements. The data are
presented in FIG. 7. This technique shows a clear difference in the
zeta potential measurements, as a function of surface coating
process, where the improved covering of magnesium stearate is
indicated by an increasingly negative zeta potential.
[0197] These results demonstrate that applying the additive
material to fine or ultra-fine carrier or active particles by
conventional mixing or blending, for example using a low shear
mixer like a Turbula mixer, does not provide the same improvement
in powder performance as the use of the co-milling process
according to the present invention. The latter processes appear to
literally fuse the additive material to the surfaces of the active
or carrier particles.
[0198] The powders of the present invention are extremely flexible
and therefore have a wide number of applications, for both local
application of drugs in the lungs and for systemic delivery of
drugs via the lungs.
[0199] The present invention is also applicable to nasal delivery,
and powder formulations intended for this alternative mode of
administration to the nasal mucosa.
[0200] The formulations according to the present invention may be
administered using active or passive devices, as it has now been
identified how one may tailor the formulation to the device used to
dispense it, which means that the perceived disadvantages of
passive devices where high performance is sought may be
overcome.
[0201] According to a third aspect of the present invention, a dry
powder device is provided, the device comprising a powder
formulation according to the second aspect of the invention.
[0202] In one embodiment of the invention, the inhaler device is an
active device, in which a source of compressed gas or alternative
energy source is used. Examples of suitable active devices include
Aspirair.TM. (Vectura Ltd) and the active inhaler device produced
by Nektar Therapeutics (as covered by U.S. Pat. No. 6,257,233).
[0203] In an alternative embodiment, the inhaler device is a
passive device, in which the patient's breath is the only source of
gas which provides a motive force in the device. Examples of
"passive" dry powder inhaler devices include the Rotahaler.TM. and
Diskhaler.TM. (GlaxoSmithKline) and the Turbohaler.TM.
(Astra-Draco) and Novolizer.TM. (Viatris GmbH).
[0204] The size of the doses can vary from micrograms to tens of
milligrams. The fact that dense particles may be used, in contrast
to conventional thinking, means that larger doses can be
administered without needing to administer large volumes of powder
and the problems associated therewith.
[0205] The dry powder formulations may be pre-metered and kept in
foil blisters which offer chemical and physical protection whilst
not being detrimental to the overall performance. Indeed, the
formulations thus packaged tend to be stable over long periods of
time, which is very beneficial, especially from a commercial and
economic point of view.
[0206] According to a fourth aspect of the present invention, a
receptacle is provided, holding a single dose of a powder according
to the second aspect of the present invention.
[0207] The receptacle may be a capsule or blister, preferably a
foil blister.
* * * * *