U.S. patent application number 10/403548 was filed with the patent office on 2003-10-30 for systems and processes for spray drying hydrophobic drugs with hydrophilic excipients.
Invention is credited to Brewer, Thomas K., Clark, Andrew, Gordon, Marc S..
Application Number | 20030203036 10/403548 |
Document ID | / |
Family ID | 29253881 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030203036 |
Kind Code |
A1 |
Gordon, Marc S. ; et
al. |
October 30, 2003 |
Systems and processes for spray drying hydrophobic drugs with
hydrophilic excipients
Abstract
Methods for preparing dry powders having hydrophobic and
hydrophilic components comprise combining solutions of the
components and spray drying them simultaneously in a spray dryer.
The hydrophilic and hydrophobic component are separately dissolved
in separate solvents and directed simultaneously through a nozzle,
usually a coaxial nozzle, into the spray dryer. The method provides
dry powders having relatively uniform characteristics.
Inventors: |
Gordon, Marc S.; (Sunnyvale,
CA) ; Clark, Andrew; (Half Moon Bay, CA) ;
Brewer, Thomas K.; (Walnut Creek, CA) |
Correspondence
Address: |
NEKTAR THERAPEUTICS
150 INDUSTRIAL ROAD
SAN CARLOS
CA
94070
US
|
Family ID: |
29253881 |
Appl. No.: |
10/403548 |
Filed: |
March 31, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10403548 |
Mar 31, 2003 |
|
|
|
10072407 |
Feb 8, 2002 |
|
|
|
6572893 |
|
|
|
|
10072407 |
Feb 8, 2002 |
|
|
|
09528758 |
Mar 17, 2000 |
|
|
|
6365190 |
|
|
|
|
Current U.S.
Class: |
424/489 ; 264/5;
514/167; 514/171; 514/20.5; 514/21.1; 514/454; 514/458; 514/53;
514/54; 514/573; 514/682; 514/725 |
Current CPC
Class: |
A61K 9/1611 20130101;
A61K 31/59 20130101; A61K 31/56 20130101; A61K 31/557 20130101;
A61K 31/715 20130101; A61K 31/12 20130101; A61K 9/1623 20130101;
A61K 31/573 20130101; A61K 9/0075 20130101; A61K 31/7012 20130101;
A61K 31/355 20130101; A61K 31/353 20130101 |
Class at
Publication: |
424/489 ; 264/5;
514/2; 514/167; 514/171; 514/725; 514/458; 514/573; 514/682;
514/53; 514/54; 514/454 |
International
Class: |
A61K 038/17; A61K
031/7012; A61K 031/573; B29B 009/00; A61K 031/715; A61K 031/59;
A61K 031/56; A61K 031/355; A61K 031/353; A61K 031/557; A01N 031/04;
A61K 031/12 |
Claims
What is claimed is:
1. A method for preparing a dry powder composition, said method
comprising: preparing an aqueous solution of a hydrophilic
component; preparing an organic solution of a hydrophobic component
in an organic solvent; and spray drying the aqueous solution and
the organic solution simultaneously to form particles comprising a
mixture of the hydrophilic and hydrophobic component.
2. A method as in claim 1, wherein the hydrophilic component has a
concentration in the aqueous solution from 1 mg/ml to 100
mg/ml.
3. A method as in claim 2, wherein the hydrophobic component has a
solubility of at least 0.01 mg/ml in the organic solvent.
4. A method as in claim 3, wherein the hydrophobic component has a
concentration in the range from 0.01 mg/ml to 10 mg/ml in the
organic solvent.
5. A method as in claim 1, wherein the organic solvent is selected
from the group consisting of alcohols, ketones, ethers, aldehydes,
hydrocarbons, and polar aprotic solvents and mixtures thereof.
6. A method as in claim 1, wherein the aqueous solution and the
organic solution are sprayed through a common nozzle.
7. A method as in claim 6, wherein the nozzle is a coaxial spray
nozzle.
8. A method as in claim 1, wherein the hydrophobic component
comprises a hydrophobic drug.
9. A method as in claim 8, wherein the hydrophobic drug is a
steroid selected from the group consisting of budesonide,
testosterone, progesterone, estrogen, flunisolide, triamcinolone,
beclomethasone, betamethasone, dexamethasone, fluticasone,
methylprednisolone, prednisone, hydrocortisone.
10. A method as in claim 8, wherein the hydrophobic drug comprises
a peptide, a retinoid, vitamin D, vitamin E, vitamin K, precursors
and derivatives of these vitamins, a prostaglandin, a leukotriene,
tetrahydrocannabinol, lung surfactant lipid, an antioxidant, a
hydrophobic antibiotic, and a chemotherapeutic drug.
11. A method as in claim 1, wherein the hydrophilic component
comprises an excipient for the hydrophobic drug.
12. A method as in claim 11, wherein the hydrophilic excipient
comprises a material selected from the group consisting of lactose,
sodium citrate, mannitol, povidone, pectin, citric acid, sodium
chloride, and mixtures thereof.
13. A method as in claim 1, further comprising screening the spray
dried particles to disrupt agglomerates.
14. A method as in claim 1, further comprising: measuring a single
dosage of the dry powder; and sealing the single dosage in a
package.
15. A dry powder composition prepared according to claim 1.
16. A unit dose of a dry powder composition comprising a unit dose
receptacle having a therapeutically effective amount of a dry
powder composition according to claim 1.
17. A method for aerosolizing a dry powder composition said method
comprising: providing an amount of a dry powder composition
according to claim 1; and dispersing the dry powder composition
into a flowing gas stream.
Description
[0001] This application is a continuation-in-part of Provisional
Application No. 60/034,837, filed on Dec. 31, 1996, the full
disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to dry powder
compositions and methods for their preparation and use. In
particular, the present invention relates to methods for spray
drying pharmaceutical and other compositions comprising a
hydrophobic drug or other component and a hydrophilic excipient or
other component.
[0004] Over the years, certain drugs have been sold in formulations
suitable for oral inhalation (pulmonary delivery) to treat various
conditions in humans. Such pulmonary drug delivery formulations are
designed to be inhaled by the patient so that the active drug
within the dispersion reaches the lung. It has been found that
certain drugs delivered to the lung are readily absorbed through
the alveolar region directly into blood circulation. Such pulmonary
delivery can be effective both for systemic delivery and for
localized delivery to treat diseases of the lungs.
[0005] Pulmonary drug delivery can itself be achieved by different
approaches, including liquid nebulizers, aerosol-based metered dose
inhalers (MDI's), and dry powder dispersion devices. Aerosol-based
MDI's are losing favor because they rely on the use of
chlorofluorocarbons (CFC's), which are being banned because of
their adverse effect on the ozone layer. Dry powder dispersion
devices, which do not rely on CFC aerosol technology, are promising
for delivering drugs that may be readily formulated as dry
powders.
[0006] The ability to deliver pharmaceutical compositions as dry
powders, however, is problematic in certain respects. The dosage of
many pharmaceutical compositions is often critical, so it is
desirable that dry powder delivery systems be able to accurately,
precisely, and reliably deliver the intended amount of drug.
Moreover, many pharmaceutical compositions are quite expensive.
Thus, the ability to efficiently formulate, process, package, and
deliver the dry powders with a minimal loss of drug is critical..
With dry powder drug delivery, both the delivered dose efficiency,
i.e. the percentage of drug from a unit dose receptacle which is
aerosolized and delivered from a delivery device, and the median
particle size distribution, i.e. the deviation from the median
size, are critical to the successful delivery of powders to a
patient's lungs.
[0007] A particularly promising approach for the pulmonary delivery
of dry powder drugs utilizes a hand-held device with a hand pump
for providing a source of pressurized gas. The pressurized gas is
abruptly released through a powder dispersion device, such as a
venturi nozzle, and the dispersed powder made available for patient
inhalation. While advantageous in many respects, such hand-held
devices are problematic in a number of other respects. The
particles being delivered are usually less than 5 .mu.m in size,
making powder handling and dispersion more difficult than with
larger particles. The problems are exacerbated by the relatively
small volumes of pressurized gas, which are available using
hand-actuated pumps. In particular, venturi dispersion devices are
unsuitable for difficult-to-disperse powders when only small
volumes of pressurized gas are available with the handpump. Another
requirement for hand-held and other powder delivery devices is
efficiency. High device efficiency in delivering the drug to the
patient with the optimal size distribution for pulmonary delivery
is essential for a commercially viable product.
[0008] Spray drying is a conventional chemical processing unit
operation used to produce dry particulate solids from a variety of
liquid and slurry starting materials. The use of spray drying for
the formulation of dry powder pharmaceuticals is known, but has
usually been limited to spray drying of hydrophilic drugs in
aqueous solutions, usually in combination with hydrophilic
excipients. Many drugs, however, are hydrophobic, preventing spray
drying in aqueous solutions. While spray drying of hydrophobic
materials can often be accomplished using an organic solvent, the
use of such non-aqueous solvents generally limits the ability to
simultaneously spray dry a hydrophilic excipient.
[0009] For these reasons, it would be desirable to provide improved
methods for spray drying pharmaceutical and other compositions
which comprise both hydrophobic and hydrophilic components, such as
hydrophobic drugs and hydrophilic excipients. Such spray drying
methods should be compatible with a wide variety of hydrophobic
drugs as well as conventional hydrophilic excipients, such as
povidone (polyvinylpyrrolidone) and other water soluble polymers,
citric acid, mannitol, pectin and other water soluble
carbohydrates, and particularly with those excipients which are
accepted for use in inhalation formulations, such as lactose,
sodium chloride, and sodium citrate. Such spray drying methods will
preferably produce particles having a uniform size distribution,
with a mean particle size below 10 .mu.m, preferably below 5 .mu.m,
and a standard deviation less than or equal to .+-.2 .mu.m. Such
powders should further exhibit uniform composition from batch to
batch so that any tendency for particles of different compositions
and/or sizes to separate in the lungs will have a reproducible
impact on the therapeutic effect. Additionally, such spray drying
methods should provide for dry powders which are physically and
chemically stable and which have low levels of any residual organic
solvents or other components which might be used in the spray
drying process. At least some of the above objectives will be met
by the various embodiments of the present invention which are
described in detail below.
[0010] 2. Description of the Background Art
[0011] Methods for spray drying hydrophobic and other drugs and
components are described in U.S. Pat. Nos. 5,000,888; 5,026,550;
4,670,419, 4,540,602; and 4,486,435. Bloch and Speison (1983)
Pharm. Acta Helv 58:14-22 teaches spray drying of
hydrochlorothiazide and chlorthalidone (lipophilic drugs) and a
hydrophilic adjuvant (pentaerythritol) in azeotropic solvents of
dioxane-water and 2-ethoxyethanol-water. A number of Japanese
Patent application Abstracts relate to spray drying of
hydrophilic-hydrophobic product combinations, including JP 806766;
JP 7242568; JP 7101884; JP 7101883; JP 71018982; JP 7101881; and JP
4036233. Other foreign patent publications relevant to spray drying
hydrophilic-hydrophobic product combinations include FR 2594693; DE
2209477; and WO 88/07870.
[0012] WO 96/09814 describes spray dried pharmaceutical powders. In
particular, Example 7 describes spray drying budesonide and lactose
in ethanol where the budesonide is partially soluble and the
lactose is insoluble. U.S. Pat. Nos. 5,260,306; 4,590,206; GB 2 105
189; and EP 072 046 describe a method for spray drying nedocromil
sodium to form small particles preferably in the range from 2 to 15
.mu.m for pulmonary delivery. U.S. Pat. No. 5,376,386, describes
the preparation of particulate polysaccharide carriers for
pulmonary drug delivery, where the carriers comprise particles
sized from 5 to 1000 .mu.m. Mumenthaler et al. (1994) Pharm. Res.
11:12 describes recombinant human growth hormone and recombinant
tissue-type plasminogen activator. WO 95/23613 describes preparing
an inhalation powder of DNase by spray drying using
laboratory-scale equipment. WO 91/16882 describes a method for
spray drying proteins and other drugs in liposome carriers.
[0013] The following applications assigned to the assignee of the
present application each describe that spray drying may be used to
prepare dry powders of biological macromolecules; application Ser.
No. 08/644,681, filed on May 8, 1996, which was a
continuation-in-part of application Ser. No. 08/423,S15, filed on
Apr. 14, 1995; application Ser. No. 08/383,475, which was a
continuation-in-part of application Ser. No. 08/207,472, filed on
Mar. 7, 1994; application Ser. No. 08/472,563, filed on Apr. 14,
1995, which was a continuation-in-part of application Ser. No.
08/417,507, filed on Apr. 4, 1995, now abandoned, which was a
continuation of application Ser. No. 08/044,358, filed on Apr. 7,
1993, now abandoned; application Ser. No. 08/232,849, filed on Apr.
25, 1994, which was a continuation of application Ser. No.
07/953,397, now abandoned. WO 94/07514 claims priority from Ser.
No. 07/953,397. WO 95/24183 claims priority from Ser. Nos.
08/207,472 and 08/383,475.
SUMMARY OF THE INVENTION
[0014] According to the present invention, methods for spray drying
hydrophobic drugs and other materials are provided which overcome
at least some of the deficiencies noted above with respect to prior
spray drying processes. In particular, the spray drying methods of
the present invention permit the simultaneous spray drying of the
hydrophobic component with a hydrophilic component, such as a
hydrophilic pharmaceutical excipient, under conditions which result
in a dry powder comprising mixtures of both the hydrophilic and
hydrophobic components. Although the methods of the present
invention are particularly useful for forming pharmaceutical
compositions where the hydrophobic component is a hydrophobic drug,
usually present at from 0.01% to 95% of the powder, and the
hydrophilic component is a hydrophilic excipient, usually present
at from 99.99% to 5% of the powder, the methods may be applied more
broadly to form dry powders comprising a variety of hydrophobic and
hydrophilic components at different concentration ranges, including
hydrophilic drugs and hydrophobic excipients.
[0015] The spray drying methods of the present invention are
compatible with at least most hydrophilic pharmaceutical
excipients, particularly including mannitol, povidone, pectin,
lactose, sodium chloride, and sodium citrate. Use of the latter
three excipients is particularly preferred for powders intended for
pulmonary delivery as they are "generally recognized as safe"
(GRAS) for such applications. The methods are also suitable for use
with numerous hydrophobic drugs and nutrients, including steroids
and their salts, such as budesonide, testosterone, progesterone,
estrogen, flunisolide, triamcinolone, beclomethasone,
betamethasone; dexamethasone, fluticasone, methylprednisolone,
prednisone, hydrocortisone, and the like; peptides, such as
cyclosporin and other water insoluble peptides; retinoids, such as
all-cis retinoic acid, 13-trans retinoic acid, and other vitamin A
and beta carotene derivatives; vitamins D, E, and K and water
insoluble precursors and derivatives thereof; prostaglandins and
leukotrienes and their activators and inhibitors including
prostacyclin (epoprostanol), and prostaglandins E.sub.1 E.sub.2;
tetrahydrocannabinol; lung surfactant lipids; lipid soluble
antioxidants; hydrophobic antibiotics and chemotherapeutic drugs
such as amphotericin B, adriamycin, and the like.
[0016] The spray drying methods can produce a uniform particle size
distribution. For example, the mean particle diameter can be
controlled below 10 .mu.m, preferably below 5 .mu.m, with a size
distribution (standard deviation) less than .+-.2 .mu.m. The
particles of the powders so produced have a minimum batch-to-batch
variability in composition, and are physically and chemically
stable. The powders have minimum residual organic solvents to the
extent they may have been used in the spray drying process.
[0017] In particular, the method of the present invention comprises
preparing an aqueous solution of a hydrophilic component and an
organic solution of a hydrophobic component in an organic solvent.
The aqueous solution and the organic solution are simultaneously
spray dried to form particles comprising a mixture of the
hydrophilic and hydrophobic components. Usually the hydrophilic
component has a concentration in the aqueous solution from 1 mg/ml
to 100 mg/ml, preferably from 5 mg/ml to 60 mg/ml. The hydrophobic
component has a solubility in the organic solution of at least 0.01
mg/ml, preferably at least 0.05 mg/ml. The concentration of the
hydrophobic component in the organic solution is usually in the
range from 0.01 mg/ml to 10 mg/ml, preferably from 0.05 mg/ml to 5
mg/ml. Preferred organic solvents include alcohols, ketones,
ethers, aldehydes, hydrocarbons, and polar aprotic solvents, and
the like and mixtures thereof. The use of a separate aqueous and
organic solution to carry the hydrophilic and hydrophobic
components, respectively, is advantageous in that it allows a much
broader range of selection for the organic solvent, since the
organic solvent does not also have to solubilize the hydrophilic
component. It is also particularly advantageous for spray drying
hydrophobic components and hydrophilic components which are
chemically or physically incompatible in solution, since the
solutions of the hydrophobic components and hydrophilic components
do not reside together until they are passing through the spray
nozzle during spray drying. This severely minimizes the contact
time between the two solutions before drying occurs, and hence
minimizes the potential for undesirable reactions o occur. Usually,
the aqueous solution and organic solution will be spray dried
through a common spray nozzle, more usually through a coaxial spray
nozzle.
[0018] Powders prepared by any of the above methods will be
collected from the spray dryer in a conventional manner for
subsequent use. For use as pharmaceuticals and other purposes, it
will frequently be desirable to disrupt any agglomerates which may
have formed by screening or other conventional techniques. For
pharmaceutical uses, the dry powder formulations will usually be
measured into a single dose, and the single dose sealed into a
package. Such packages are particularly useful for dispersion in
dry powder inhalers, as described in detail below. Alternatively,
the powders may be packaged in multiple-dose containers.
[0019] The present invention further comprises dry powder
compositions produced according to the methods described above, as
well as unit dose and multidose packages of such dried powder
compositions containing a therapeutically effective amount of the
dry powder.
[0020] The present invention further provides methods for
aerosolizing a dry powder composition comprising the steps of
providing an amount of dry powder composition produced by any of
the methods described above and subsequently dispersing the dry
powder composition into a flowing gas stream.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a block diagram illustrating a spray drying system
suitable for performing the methods of the present invention.
[0022] FIG. 2. illustrates a coaxial spray nozzle used in spray
drying as described in the Experimental section.
[0023] FIG. 3 illustrates a two-tube spray nozzle used in spray
drying as described in the Experimental section.
[0024] FIG. 3A is a detail cross-section view of region 3A in FIG.
3.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0025] The present invention relates to methods for preparing
compositions comprising ultrafine dry powders having both
hydrophobic and hydrophilic components. The methods are
particularly suitable for producing ultrafine pharmaceutical dry
powders where the hydrophobic component is a hydrophobic drug and
the hydrophilic component is a hydrophilic excipient. The present
invention, however, may find use for preparing a variety of other
compositions including pharmaceutical compositions having
hydrophilic drugs and hydrophobic excipients and compositions
intended for non-pharmaceutical applications. The methods rely on
spray drying liquid media in which the components are solubilized
or suspended. In particular, the hydrophobic and hydrophilic
components are solubilized in separate liquid media and the media
are simultaneously spray dried through a common nozzle.
[0026] The term "hydrophobic component" refers to materials which
are insoluble or sparingly or poorly soluble in water. As used
herein, such compositions will have a solubility below 5 mg/ml,
usually below 1 mg/ml. Exemplary hydrophobic drugs include certain
steroids, such as budesonide, testosterone, progesterone, estrogen,
flunisolide, triamcinolone, beclomethasone, betamethasone;
dexamethasone, fluticasone, methylprednisolone, prednisone,
hydrocortisone, and the like; certain peptides, such as cyclosporin
cyclic peptide, retinoids, such as all-cis retinoic acid, 13-trans
retinoic acid, and other vitamin A and beta carotene derivatives;
vitamins D, E, and K and water insoluble precursors and derivatives
thereof; prostagladins and leukotrienes and their activators and
inhibitors including prostacyclin (epoprostanol), and
prostaglandins E.sub.1 E.sub.2; tetrahydrocannabinol; lung
surfactant lipids; lipid soluble antioxidants; hydrophobic
antibiotics and chemotherapeutic drugs such as amphotericin B and
adriamycin and the like.
[0027] By "hydrophilic component," it is meant that the component
is highly soluble in water and frequently capable of swelling and
formation of reversible gels. Typical aqueous solubilities of
hydrophilic components will be greater than 5 mg/ml, usually
greater than 50 mg/ml, often greater than 100 mg/ml and often much
higher. In addition to their hydrophilic nature, the pharmaceutical
excipients will generally be selected to provide stability,
dispersibility, consistency and/or bulking characteristics to
enhance the uniform pulmonary delivery of the dried powder
composition to a patient. For pulmonary delivery, the excipients
must be capable of being taken into the lungs with no significant
adverse toxicological effects on the lungs. Exemplary hydrophilic
excipients include carbohydrates and other materials selected from
the group consisting of lactose, sodium citrate, mannitol,
povidone, pectin, citric acid, sodium chloride, water soluble
polymers, and the like. Particularly preferred are lactose, sodium
chloride, sodium citrate, and citric acid which are generally
accepted for pulmonary delivery in dry powder formulations.
[0028] The phrase "ultrafine dry powder" means a powder composition
comprising a plurality of discrete, dry particles having the
characteristics set forth below. In particular, the dry particles
will have an average particle size below 10 .mu.m, usually below 5
.mu.m, preferably being in the range from 0.4 to 5 .mu.m, more
preferably from 0.4 to 4 .mu.m. The average particle size of the
powder will be measured as mass median diameter (MMD) by
conventional techniques. A particular powder sizing technique uses
a centrifugal sedimentary particle size analyzer (Horiba Capa 700).
The powders will be capable of being readily dispersed in an
inhalation device and subsequently inhaled by a patient so that the
particles are able to penetrate into the alveolar regions of the
lungs.
[0029] Of particular importance to the present invention, the
ultrafine dry particle compositions produced by the method will
have particle size distributions which enable them to target the
alveolar region of the lung for pulmonary delivery of locally
acting steroids, systemically acting proteins, and other
biologically active materials that can be administered to or
through the lungs. Such compositions advantageously may be
incorporated into unit dosage and other forms without further size
classification. Usually, the ultrafine dry powders will have a size
distribution where at least 90% of the powder by weight will
comprise particles having an average size in the range from 0.1
.mu.m to 7 .mu.m, with preferably at least 85% being in the range
from 0.4 .mu.m to 5 .mu.m. Additionally, it is desirable that the
particle size distribution avoid having an excess amount of
particles with very small average diameters, i.e., below 0.4
.mu.m.
[0030] The term "dry" means that the particles of the powder have a
moisture and residual solvent content such that the powder is
physically and chemically stable in storage at room temperature and
is readily dispersible in an inhalation device to form an aerosol.
Usually, the moisture and residual solvent content of the particles
is below 10% by weight, usually being below 5% by weight,
preferably being below 3% by weight, or lower. The moisture and
residual solvent content will usually be controlled by the drying
conditions, as described in more detail below. The term "dry"
further means that the particles of the powder have a moisture and
residual solvent content such that the powder is readily
dispersible in an inhalation device to form an aerosol. In some
cases, however, non-aqueous medium may be used for dispersing the
components, in which case the aqueous content may approach
zero.
[0031] The term "therapeutically effective amount" is the amount
present in the composition that is needed to provide the desired
level of hydrophobic drug in the subject to be treated to give the
anticipated physiological response. This amount is determined for
each drug on a case-by-case basis. The term "physiologically
effective amount" is that amount delivered to a subject to give the
desired palliative or curative effect. This amount is specific for
each drug and its ultimate approval dosage level.
[0032] The therapeutically effective amount of hydrophobic drug
will vary in the composition depending on the biological activity
of the drug employed and the amount needed in a unit dosage form.
Because the subject powders are dispersible, it is highly preferred
that they be manufactured in a unit dosage form in a manner that
allows for ready manipulation by the formulator and by the
consumer. This generally means that a unit dosage will be between
about 0.5 mg and 15 mg of total material in the dry powder
composition, preferably between about 1 mg and 10 mg. Generally,
the amount of hydrophobic drug in the composition will vary from
about 0.01% w/w to about 95% w/w. Most preferably the composition
will be about 0.05% w/w to about 25% w/w drug.
[0033] Referring now to FIG. 1, processes according to the present
invention for preparing dispersible dry powders of hydrophobic and
hydrophilic components comprise an atomization operation 10 which
produces droplets of a liquid medium which are dried in a drying
operation 20. Drying of the liquid droplets results in formation of
the discrete particles which form the dry powder compositions which
are then collected in a separation operation 30. Each of these unit
operations will be described in greater detail below.
[0034] The atomization process 10 may utilize any one of several
forms of atomizers, so long as the atomizer is specially designed
to deliver the liquid containing the hydrophobic components and the
liquid containing the hydrophilic components separately to the
lower portion of the atomizer, for which FIG. 2 and FIG. 3 serve as
nonlimiting examples. The atomization process increases the surface
area of the starting liquid. Due to atomization there is an
increase in the surface energy of the liquid, the magnitude of
which is directly proportional to the surface area increase. The
source of this energy increase depends on the type of atomizer
used. Any atomizer (centrifugal, sonic, pressure, two fluid)
capable of producing droplets with a mass median diameter of less
than about 20 .mu.m could be used. Preferred for the present
invention is the use of two fluid atomizers where the liquid medium
is delivered through a nozzle concurrently with a high pressure gas
stream. Particularly preferred is the use of two-fluid atomization
nozzles as described in copending application Ser. No. 08/644,681,
which is capable of producing droplets having a median diameter
less than 20 .mu.m.
[0035] The atomization gas will usually be nitrogen which has been
filtered or otherwise cleaned to remove particulates and other
contaminants. Alternatively, other gases, such as air may be used.
The atomization gas will be pressurized for delivery through the
atomization nozzle, typically to a pressure above 5 psig,
preferably being above 10 psig. Although flow of the atomization
gas is generally limited to sonic velocity, the higher delivery
pressures result in an increased atomization gas density. Such
increased gas density has been found to reduce the droplet size
formed in the atomization operation. Smaller droplet sizes, in
turn, result in smaller particle sizes. The atomization conditions,
including atomization gas flow rate, atomization gas pressure,
liquid flow rate, and the like, will be controlled to produce
liquid droplets having an average diameter below 20 .mu.m as
measured by phase doppler velocimetry.
[0036] The drying operation 20 will be performed next to evaporate
liquid from the droplets produced by the atomization operation 10.
Usually, the drying will require introducing energy to the
droplets, typically by mixing the droplets with a heated gas which
causes evaporation of the water or other liquid medium. Preferably,
the heated gas stream will flow concurrently with the atomized
liquid, but it would also be possible to employ counter-current
flow, cross-current flow, or other flow patterns.
[0037] The drying rate may be controlled based on a number of
variables, including the droplet size distribution, the inlet
temperature of the gas stream, the outlet temperature of the gas
stream, the inlet temperature of the liquid droplets, and the
manner in which the atomized spray and hot drying gas are mixed.
Preferably, the drying gas stream will have an inlet temperature of
at least 70.degree. C. The outlet temperature will usually be at
least about 40.degree. C. The drying gas will usually be air or
nitrogen which has been filtered or otherwise treated to remove
particulates and other contaminants. The gas will be moved through
the system using conventional blowers or compressors.
[0038] The separation operation 30 will be selected in order to
achieve very high efficiency collection of the ultrafine particles
produced by the drying operation 20. Conventional separation
operations may be used, although in some cases they should be
modified in order to assure collection of sub-micron particles. In
an exemplary embodiment, separation is achieved using a filter
medium such as a membrane medium (bag filter), a sintered metal
fiber filter, or the like. Alternatively, and often preferably,
separation may be achieved using cyclone separators, although it is
usually desirable to provide for high energy separation in order to
assure the efficient collection of sub-micron particles. The
separation operation should achieve collection of at least 80% of
all particles above 1 .mu.m in average particle size, preferably
being above 85%, more preferably being above 90%, and even more
preferably being above 95%, in collection efficiency.
[0039] In some cases, a cyclone separator can be used to separate
very fine particles, e.g. 0.1 .mu.m, from the final collected
particles. The cyclone operating parameters can be selected to
provide an approximate cutoff where particles above about 0.1 .mu.m
are collected while particles below 0.1 .mu.m are carried over in
the overhead exhaust. The presence of particles below 0.1 .mu.m in
the pulmonary powder is undesirable since they will generally not
deposit in the alveolar regions of the lungs, but instead will be
exhaled.
[0040] The present invention relies on proper selection of the
liquid medium or media for solubilizing the hydrophobic drug or
other component and hydrophilic excipient or other component as
well as on the manner of introducing the component to the spray
dryer. In particular, the compositions are spray dried by forming
separate solutions of the hydrophobic drug or other component and
the hydrophilic excipient or other component. The separate
solutions are then concurrently but separately introduced to the
spray nozzle, typically by passing through a common spray nozzle or
nozzles in the spray dryers described above. This method has the
advantage that both the hydrophobic drug and the hydrophilic
excipient may be easily dissolved since it is generally straight
forward to select compatible solvents capable of fully dissolving
only one of the components. By properly directing the two solutions
through a nozzle, such as a coaxial nozzle, spray dried powders
having uniform characteristics may be achieved. This approach has
the additional advantage that it minimizes the amount of organic
solvent required since only the hydrophobic drug or other component
requires an organic solvent for dissolution. The hydrophilic
excipient is dissolved in water.
[0041] An exemplary coaxial spray nozzle 100 is illustrated in FIG.
2 and includes a housing 102 defining a chamber 103. A pair of
inlets 104 are disposed at the top of the housing 102 for receiving
the excipient solution (which is usually delivered at a higher
volumetric flow rate than is the solution of the hydrophobic
component). The excipient solution enters the chamber 103 at a
pressure sufficient to achieve a desired flow rate through an
outlet orifice 105 at the bottom of the housing 102. The
hydrophobic component solution is fed through a feed tube 106 which
usually terminates in a reduced diameter section 108 which is
disposed coaxially within the orifice 105. The absolute and
relative sizes of the orifice 105 and section 108 of feed tube 106
will depend on the total flow rates, operating pressures, and
nature of materials being spray-dried. A specific example is
described in the Experimental section hereinafter.
[0042] A second exemplary spray nozzle 200 is illustrated in FIGS.
3 and 3A. The nozzle 200 comprises a housing 202, inlets 204 and
feed tube 206, generally similar to those described above for
nozzle 100. Nozzle 200, however, is not coaxial and instead
includes a second, parallel feed tube 208 which receives solution
from chamber 203 defined within the housing 202. Both the feed tube
206 and feed tube 208 have outlet orifices 210 and 212,
respectively, at their distal ends which direct the solution flow
generally horizontally into a mixing chamber 214 disposed at the
bottom of the housing 202. The mixing chamber is shown to have a
conical geometry terminating at its bottom tip in outlet passage
216. The orifices 210 and 212 are preferably oriented as shown in
FIG. 3A where the relative angle a is in the range from 5.degree.
to 25.degree., usually about 10.degree.. Such an orifice
arrangement results in a vortical mixing flow in the chamber 214
prior to ejection from the passage 216. A variety of other mixing
chamber designs could also be utilized.
[0043] Once the dry powders have been prepared, they may be
packaged in conventional ways. For pulmonary pharmaceutical
applications, unit dosage forms may comprise a unit dosage
receptacle containing a dry powder. The powder is placed within a
suitable dosage receptacle in an amount sufficient to provide a
subject with drug for a unit dosage treatment. The dosage
receptacle is one that fits within a suitable inhalation device to
allow for the aerosolization of the dry powder composition by
dispersion into a gas stream to form an aerosol and then capturing
the aerosol so produced in a chamber having a mouthpiece attached
for subsequent inhalation by a subject in need of treatment. Such a
dosage receptacle includes any container enclosing the composition
known in the art such as gelatin or plastic capsules with a
removable portion that allows a stream of gas (e.g., air) to be
directed into the container to disperse the dry powder composition.
Such containers are exemplified by those shown in U.S. Pat. Nos.
4,227,522 issued Oct. 14, 1980; 4,192,309 issued Mar. 11, 1980; and
4,105,027 issued Aug. 8, 1978. Suitable containers also include
those used in conjunction with Glaxo's Ventolin Rotohaler.RTM.
brand powder inhaler or Fison's Spinhaler.RTM. brand powder
inhaler. Another suitable unit-dose container which provides a
superior moisture barrier is formed from an aluminum foil plastic
laminate. The pharmaceutical-based powder is filled by weight or by
volume into the depression in the formable foil and hermetically
sealed with a covering foil-plastic laminate. Such a container for
use with a powder inhalation device is described in U.S. Pat. No.
4,778,054 and is used with Glaxo's Diskhaler.RTM. (U.S. Pat. Nos.
4,627,432; 4,811,731; and 5,035,237). Preferred dry powder inhalers
are those described in U.S. patent application Ser. Nos. 08/309,691
and 08/487,184, assigned to the assignee of the present invention.
The latter application has been published as WO 96/09085.
[0044] The following examples are offered by way of illustration,
not by way of limitation.
[0045] Experimental
[0046] The following materials were used:
[0047] Budesonide (micronized to a median particle size of 1-2
.mu.m; Steraloids)
[0048] Lactose monohydrate (NF grade; Foremost Ingredient
Group)
[0049] Sodium Chloride (reagent grade from VWR and USP grade from
EM Industries)
[0050] Deionized water
[0051] Ethanol, 200 proof (USP/NF; Spectrum Chemical Mfg.
Corp.)
[0052] Acetone (for histology; EM Industries)
[0053] All batches were spray dried on Buchi 190 Mini Spray Dryers,
with nozzles and cyclones that were designed to generate and catch
very fine particles. A Buchi 190 Mini Spray Dryer was used that was
modified so that it was supplied with nitrogen as the gas source
and equipped with an oxygen sensor and other safety equipment to
minimize the possibility of explosion. The solution feed rate was 5
ml/minute, inlet temperature was adjusted to obtain the outlet
temperature noted in each example, and the top of the cyclone was
jacketed and cooled to a temperature of-about 30.degree. C. for the
examples in Table 1, but it was not cooled for the examples in
Table 2. The drying nitrogen flow rate was about 18 SCFM, and the
atomizing nitrogen was supplied at 0.5 to 1.5 SCFM. The powders
were further dried in the collector for 5 minutes by maintaining
approximately the outlet temperature and air volume after the
feeding of the liquid formulation was completed.
[0054] Particle size was determined with a Horiba Particle Size
Analyzer, model CAPA 700. Median particle size refers to the volume
based particle size distribution of the prepared bulk powders
determined via centrifugal sedimentation as follows. A sample of
the powder was suspended in an appropriate liquid medium (one that
minimizes solubilizing the particle), sonicated to break up the
agglomerates, and then centrifuged. The median particle size was
determined by measuring the sedimentation rate during
centrifugation. This method provides the median size of the
"primary" particle, that is, the size of the particles produced by
the manufacturing process, plus potential modification during
sample preparation. Because these formulations are composed of both
water soluble and water insoluble materials, it is likely that the
suspension step during sample preparation does to some extent
solubilize part of the particle, and thereby modify the particle
size that is determined. Therefore, the resultant particle sizes
should be viewed as estimated values, rather than absolute
values.
[0055] Moisture content was determined by the Karl-Fischer Reagent
titrimetric method.
[0056] Delivered dose efficiency refers to a measure of the
percentage of powder which is drawn out of a blister package and
which exits the mouthpiece of an inhaler device as described in
U.S. patent application Ser. No. 08/487,184. Delivered dose
efficiency is a measure of efficiency for the powder package/device
combination. The test was performed by connecting a vacuum system
to the device mouthpiece. The vacuum system was set to be similar
to a human inhalation with regard to volume and flow rate (1.2
liters total at 30 liters/minute). A blister package containing 0.5
to 10 mg of the formulation to be evaluated (5 mg of powder was
used for the following examples) was loaded into a device which was
held in a testing fixture. The device was pumped and fired, and the
vacuum "inhalation" was switched on. The aerosol cloud was thus
drawn out of the device chamber by the vacuum, and the powder was
collected on a filter placed between the mouthpiece and the vacuum
source. The weight of the powder collected on the filter was
determined. Delivered dose efficiency was calculated by multiplying
this weight by one hundred and dividing by the fill weight in the
blister. A higher number was a better result than a lower
number.
[0057] MMAD (mass median aerodynamic diameter) refers to a measure
of the particle size of the aerosolized powder. MMAD was determined
with an Andersen cascade impactor. In a cascade impactor the
aerosolized powder (which was aerosolized using an inhaler device
as described in U.S. patent application Ser. No. 08/487,184) enters
the impactor via an air stream, and encounters a series of stages
that separate particles by their aerodynamic diameter (the smallest
particles pass farthest down the impactor). The amount of powder
collected on each stage is determined gravimetrically, and the mass
median aerodynamic diameter is then calculated.
[0058] Coaxial Nozzle System:
[0059] Manufacturing procedure:
[0060] The budesonide was mixed in the organic solvent until all of
the budesonide was completely dissolved to form a solution, with
sonication if necessary. The excipient was mixed with the water
until all of the excipient was completely dissolved to form a
solution, with sonication, if necessary. The solutions were spray
dried using a coaxial nozzle spray drying system having a nozzle as
illustrated in FIG. 2 or FIG. 3. The FIG. 2 orifice 105 had a
diameter of 1.0 mm and outlet tube section 108 had an outside
diameter of 0.73 mm and an inside diameter of 0.6 mm. The FIG. 3
orifice 216 had a diameter of 1.0 mm and outlet orifices 210 and
212 had diameters of 0.15 mm.
[0061] The two solutions were fed to the nozzle at constant rates
such that they both finished being fed to the nozzle at the same
time.
[0062] Table 1 and Table 2 show the spray dryer atomization air
pressure and outlet air temperature, the quantitative composition
of example formulations, a description of the particle morphology,
the moisture content, particle size, and delivered dose efficiency
or MMAD of the resultant powders. Table 1 examples were spray dried
using the nozzle illustrated in FIG. 2, whereas Table 2 examples
were spray dried using the nozzle illustrated in FIG. 3.
1TABLE 1 Batch No., Formula No. (Spray Dryer Atomization Particle
Delivered Air Pressure/Outlet Air Quantitative Particle Moisture
Size Dose Temperature) Composition Morphology Content (.mu.m)
Efficiency 329-44 Budesonide 75 mg Slighdy 0.76% 2.11 42.0% (RSD =
25) B-13 Ethanol 25 ml wrinkled (20PSI/76.degree. C.) Lactose 1425
mg spheres DI water 25 ml 329-47 Budesonide 50 mg 1.09% 1.99 49.5%
(RSD = 16) B-14 9:1 Acetone:water 1.25 ml (40PSI/77.degree. C.)
Lactose 950 mg DI water 98.75 ml
[0063]
2TABLE 2 Batch No., Formula No., Particle Powder (Spray Drier
Atomization Air Quantitative Particle Moisture Size MMAD
Pressure/Outlet Air Temperature) Composition morphology Content
(.mu.m) (.mu.m) 446-63E-S Budesonide 187.5 mg Smooth 0.81% 1.34
.mu.m 2.41 13-38 Ethanol 62.5 ml irregular (40PSI/77.degree. C.)
Lactose 656.25 mg spheres NaCl 656.25 mg DI Water 12.5 ml 529-44B-S
Budesonide 165 mg 1.16% 1.33 .mu.m 2.68 B-48 Acetone 55 ml
(30PSI/77 .degree. C.) Lactose 577.5 mg NaCl 577.5 mg DI Water 11
ml
[0064] Although the foregoing invention has been described in some
detail by way of illustration and example, for purposes of clarity
of understanding, it will be obvious that certain changes and
modifications may be practiced within the scope of the appended
claims.
* * * * *