FIELD OF THE INVENTION
The present invention relates to an improved process of manufacturing sterile, ophthalmic
pharmaceutical suspensions comprising sterile active ingredient(s) such as carbonic anhydrase
inhibitors (CAIs), preferably sterile brinzolamide. The sterile ophthalmic pharmaceutical
suspensions are useful in the treatment of elevated intraocular pressure in persons suffering from
ocular hypertension or primary open angle glaucoma.
BACKGROUND OF THE INVENTION
Brinzolamide is a carbonic anhydrase inhibitor used to lower intraocular pressure in
patients with ocular hypertension or open-angle glaucoma. Brinzolamide is chemically (R)-(+)-
4-Ethylamino-2-(3-methoxypropyl)-3,4- dihydro-2H-thieno [3, 2-e]-l,2-thiazine-6-sulfonamide-
1,1 -dioxide and has the empirical formula C12H21N3O5S3. Brinzolamide has a molecular
weight of 383.5 and a melting point of about 131.deg.C.
This compound is disclosed in U. S. Pat. No. 5,378,703 (Dean, et al.). The compound is
also disclosed in European patent EP 527801. US Pat. No. 6,071,904 discloses processes for
preparation of brinzolamide ophthalmic composition.
Brinzolamide ophthalmic suspension is developed and marketed by Alcon Laboratories
Inc. in United States under the brand name AZOPT(R) (Brinzolamide ophthalmic suspension
1%). Brinzolamide is indicated for lowering elevated intra-ocular pressure (IOP) in patients with
open- angle glaucoma or ocular hypertension (OHT).
Various methods have been disclosed in the prior for the preparation of brinzolamide
ophthalmic suspension. International patent application WO 98/25620 teaches that conventional
sterilization methods cannot be employed in the manufacture of suspensions comprising
brinzolamide since the compound recrystallizes at autoclaving temperatures forming large
needle-type crystals.
According to WO 98/25620, also dry heat sterilization is not suitable since it causes
melting of the material, whereas sterilization by ethylene oxide and gamma irradiation introduces
unacceptable degradation products.
3
EP0941094 discloses a process for making brinzolamide suspension by autoclaving of
concentrated slurry of brinzolamide in milling bottle, ball milling of the hot slurry, and then
adding the slurry to the rest of the ingredients.
EP2394637 discloses a process for sterilizing brinzolamide suspensions using gamma
irradiation or ethylene oxide.
In these cited references procedures, the use of a typical ball milling process to reduce
particle size of ophthalmic drugs in aqueous suspensions is not desirable for several reasons.
Firstly, the ball-milling process and parameters must be carefully controlled in order to ensure
adequate particle size reduction.
Secondly, it was found that the ball-milling process does not prevent subsequent
aggregation of the drug particles in the suspension formulation. As a result, the suspension
formulation may contain drag aggregates having a particle sizes above the recommended range
for ophthalmic formulations. Thus, formulations prepared according to WO 98/25620 may not
have the desired stability towards drug particle aggregation.
Thus, a cited reference discloses autoclaving of the slurry of brinzolamide and surfactant
and further ball milling the slurry. However, the drawback associated with this method is that it
requires a milling bottles in which the slurry of brinzolamide could initially be autoclaved and
then ball milled for further size reduction of needle shaped crystals of brinzolamide that are
formed during autoclaving leading to wastage, expensive, time consuming and non-reproducible
process. Furthermore the use of expensive instruments adds to the cost of production.
The inventors of the present invention have surprisingly invented a cost effective, easily
reproducible process with minimal use of equipment’s and complex technology for
manufacturing a sterile ophthalmic suspension comprising sterile brinzolamide wherein the
process does not require the use of any specific equipment’s such as ball mill, milling bottle
and/or jet mill. This process ameliorates the drawbacks associated with cited references methods
for preparation of brinzolamide ophthalmic suspension.
4
OBJECTS OF THE PRESENT INVENTION
The main object of the present invention is to provide an improved process of manufacturing a
sterile, ophthalmic pharmaceutical suspension comprising a sterile therapeutic active agent or
acceptable salts thereof and pharmaceutically acceptable excipients thereof.
Yet another object of the present invention is to provide a process which is simple, easily
reproducible and cost effective.
Yet another object of the present invention is to provide a process for manufacturing ophthalmic
pharmaceutical formulation without use of any specific equipment such as ball mill, milling
bottle and/or jet mill.
Yet another object of the present invention is to provide a sterile ophthalmic pharmaceutical
suspension that are useful in the treatment of elevated intraocular pressure in patients with ocular
hypertension or open angle glaucoma.
SUMMARY OF THE INVENTION
The present invention provides a simple and efficient process of manufacturing a sterile
brinzolamide ophthalmic suspension.
The present invention provides a process of manufacturing a sterile, ophthalmic
pharmaceutical suspension comprising sterile active ingredient(s) such as sterile carbonic
anhydrase inhibitors (CAIs) wherein the process doesn’t involve the use of any special
equipment’s such as ball mill, milling bottle and/or jet mill.
Another embodiment of the present invention is to provide an efficient and economic
process of manufacturing a sterile brinzolamide ophthalmic pharmaceutical suspension
compared to ball milled process wherein the present improved process can minimize or prevent
the suspended drug particles from forming aggregates.
Further embodiment of the present invention provides a process of manufacturing a
sterile, ophthalmic pharmaceutical suspension comprising sterile active ingredient(s) such as
sterile carbonic anhydrase inhibitors (CAIs) wherein the compositions are formulated optionally
5
with a pharmaceutically acceptable preservative such that the suspension may be formulated both
as a unit-dose as well as multi-dose composition.
Furthermore in an embodiment, the manufacturing process of the present invention
reduces the generation of Impurity A wherein the reduction of Impurity A will enhance the shelflife
of the product thereby increases the stability of the present invention.
Another embodiment of the present invention is to provide a process of manufacturing a
sterile brinzolamide ophthalmic pharmaceutical suspension which ameliorates one or more
drawbacks of the reference processes.
The sterile ophthalmic pharmaceutical suspensions of the present invention are useful in
the treatment of elevated intraocular pressure in patients with ocular hypertension or open-angle
glaucoma.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: Showing the particle size evaluation of present invention formulation of
brinzolamide ophthalmic suspension 1.0% using Morphology G3 instrument from Malvern at
Aimil Labs in Vadodara.
Figure 2: Showing the particle size evaluation of Reference listed drug (AZOPT(R)) using
Morphology G3 instrument from Malvern at Aimil Labs in Vadodara.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, the term “BAC” wherever appears is an abbreviation for “benzalkonium
chloride”.
As used herein, the “CAIs” wherever appears is an abbreviation for “carbonic anhydrase
inhibitors”.
As used herein, the “brinzoalmide API” wherever appears is a sterile brinzolamide
procured from ICROM S.p.A, Italy.
6
As used herein, the “API” wherever appears is an abbreviation for “active pharmaceutical
ingredient”.
As used herein, the “USP” wherever appears is an abbreviation for “United States
Pharmacopeia”.
As used herein, the “LDPE” wherever appears is an abbreviation for “low density
polyethylene”.
As used herein, the “HDPE” wherever appears is an abbreviation for “high density
polyethylene”.
As used herein, the “BKC” wherever appears is an abbreviation for “benzalkonium
chloride”.
As used herein, the “NaOH” wherever appears is an abbreviation for “Sodium
Hydroxide”.
As used herein, the “HCl” wherever appears is an abbreviation for “Hydrochloric Acid”.
As used herein, the “EDTA” wherever appears is an abbreviation for “edetate disodium”.
As used herein, the “RLD” wherever appears is an abbreviation for “Reference listed drug” as
developed and marketed by Alcon Laboratories Inc. in United States under the brand name
AZOPT(R) (brinzolamide ophthalmic suspension 1%).
As used herein, wherever the drug comprises brinzolamide, the impurities preferably
measured include Impurity A (S)-4-(ethylamino)-3,4-dihydro-2-(3-methoxypropyl)-2Hthieno[
3,2-e]-1,2-thiazine-6-sulfonamide 1,1-dioxide; Impurity B, (R)-4-(amino)-3,4-dihydro-2-
(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide 1,1-dioxide, Impurity C (S)-4-
(hydroxy)-3,4-dihydro-2-(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide 1,1-
dioxide and Impurity D 6-(amino-hydroxy-oxo-6-sulfanyl)-2-(3-methoxypropyl)-1,1-dioxo-3Hthieno[
3,2-e]thiazin-4-one.As used herein, the “active ingredient” is defined as the chemical
substance, which is used in the prevention or treatment of various diseases associated with
human or non-human animals.
7
The present invention relates to an improved process of manufacturing a sterile
ophthalmic pharmaceutical suspension of sterile active ingredient(s) such as sterile carbonic
anhydrase inhibitor (CAI) or combinations thereof.
The term sterile active ingredient(s) can be interchangeably used with their
pharmaceutically acceptable salt(s), hydrate(s), solvate(s), polymorph(s), stereoisomers), ester(s),
prodrug(s), complex(es) and their metabolites thereof.
According to one embodiment of the present invention there is provided a sterile
ophthalmic suspension prepared by the process as described herein comprising sterile
brinzolamide in an amount from 0.001% to 5.0% by weight.
In an embodiment of the present invention there is provided an improved process of
manufacturing a sterile ophthalmic suspension wherein the process comprising the steps of:
a) preparing a solution comprising polymer (Carbomer(R) 974 P), chelating
agent (edetate disodium), one or more tonicity agents (mannitol and/or
sodium chloride) and optionally with a preservative (benzalkonium
chloride).
b) adjusting the pH of the solution of step a) between 7.5 ± 0.3 by adding
sodium hydroxide/ hydrochloric acid, in increments, if required.
c) sterilizing the bulk of step a) by in-situ sterilization.
d) preparing a surfactant (Tyloxapol(R) or Triton X-100(R)) solution in
another pressure vessel.
e) filtering a surfactant solution of step d) through 0.2 μ filter.
f) adding aseptically sterile API to the above surfactant solution of step e).
g) homogenizing the above slurry using high pressure homogenizer at
pressure 1000±200 bar to achieve uniform dispersion.
h) transfering this homogenized slurry into sterile bulk in filtration tank of
step c).
i) Continue the stirring to get a uniform bulk.
j) Volume makeup with water for injection.
8
Another embodiment of the present invention is to provide an improved process for
preparation of sterile brinzolamide ophthalmic suspension, the process being efficient, economic,
and feasible for commercial scale preparation and which does not involve the use of any special
equipment’s such as ball mill, milling bottle and/or jet mill.
In another embodiment of the present invention is to provide a process of manufacturing
a sterile brinzolamide ophthalmic pharmaceutical suspension which ameliorates one or more
drawbacks of the cited references processes.
In one of the preferred embodiment the present inventors uses approximately only 1/10th
of the batch volume for high pressure homogenization at pressure 1000±200 bar whereas the
innovator uses the entire batch for ball milling. Thus the process of present invention leads to the
minimal wastage of batch product. Also there are no viscosity issues in the product of present
invention with the use of carbomer which further leads to easily homogenisable product which is
easy to process and handle.
According to a preferred embodiment, the present invention provides a sterile
brinzolamide ophthalmic suspensions comprising: the sterile active ingredient brinzolamide,
tyloxapol(R); Carbomer(R) 974 P; mannitol, sodium chloride, edetate disodium, benzalkonium
chloride, sodium hydroxide and/or hydrochloric acid (to adjust the pH) wherein the process does
not involve the use of any special equipment’s such as ball mill, milling bottle and/or jet mill.
According to a another preferred embodiment, the present invention provides a sterile
ophthalmic suspensions comprising: the sterile active ingredient brinzolamide, tyloxapol(R);
Carbomer(R) 974 P; mannitol, sodium chloride, edetate disodium, sodium hydroxide and/or
hydrochloric acid (to adjust the pH) wherein the process does not involve the use of any special
equipment’s such as ball mill, milling bottle and/or jet mill.
The active ingredient used in the pharmaceutical ophthalmic suspension, may be a
soluble or sparingly soluble or slightly soluble or very slightly soluble or practically insoluble
compound(s) selected from the group but are not limited to a carbonic anhydrase inhibitor (CAI),
such as sterile brinzolamide, acetazolamide, dorzolamide, methazolamide; a beta-blocker, such
as timolol, arteolol, metopranolol, betaxolol or other actives used for ophthalmic formulation or a
9
pharmaceutically acceptable salt(s), hydrate(s), solvate(s), polymorph(s), stereoisomers), ester(s),
prodrug(s), complex(es) and their metabolites thereof. One of the preferred active is a CAI, or a
beta-blocker or a steroid. In a preferred embodiment the CAI is brinzolamide which is sterile in
nature, can be in combination with a beta-blocker.
Brinzolamide API used in the preparation of pharmaceutical suspension of the present
invention is a sterile brinzolamide procured from ICROM S.p.A, Italy.
Examples of polymers that may be used according to the invention include, but are not
limited to Carbomer(R) such as Carbomer(R) 974 P (a synthetic, high molecular weight
crosslinked polymer of acrylic acid), povidone, hydroxypropylmethylcellulose,
hydroxypropylcellulose, hydroxyethylcellulose and mixtures thereof. Polymers may be used in
amount from about 0.1% to about 5.0%, preferably from about 0.3% to about 1.0%.
Examples of preservatives that may be used according to the invention include but are not
limited to quaternary ammonium salts such as benzalkonium chloride (BKC) and benzethonium
chloride; cationic compounds such as chlorhexidine gluconate; p-hydroxybenzoates such as
methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate and butyl phydroxybenzoate;
alcohol compounds such as chlorobutanol and benzyl alcohol; sodium
dehydroacetate; and thiomersal, benzethonium chloride, phenyl ethanol, phenyl propanol, phenyl
mercuric acetate, phenyl mercuric nitrate, phenyl mercuric borate, chlorhexidine acetate or
gluconate, cetrimide, chlorocresol, sodium methyl paraben, sodiumpropyl paraben, thimerosal,
benzalkonium chloride and mixtures thereof and may be used in an amount from about 0.001%
to about 0.5%, preferably from about 0.005% to about 0.05%. Of the recited preservatives,
quaternary ammonium salts and cationic compounds are preferable as they suppress formation of
agglomerates, prevent lowering of pH, and provide a suspension superior in redispersibility and
stability. Of the quaternary ammonium salts, benzalkonium chloride and benzethonium chloride
are particularly preferable, and chlorhexidine gluconate is particularly preferable as the cationic
compound.
Examples of surfactants that may be used according to the invention include but are not
limited to Tyloxapol(R), Triton X-100(R), polysorbates, polyoxyl 35 castor oil, polyoxyl 40
hydrogenated castor oil, polyoxyl 40 stearates, sorbitan monolaureates, poloxamer and mixtures
10
thereof and may be used in amount from about 0.001% to about 15 %, preferably from about
0.01% to about 0.5%. Tyloxapol(R) is chemically known as 4-(l, l,3,3-Tetramethylbutyl)phenol
polymer with formaldehyde and oxirane. Triton X-100(R) is chemically known as (a-[4-(l, l,3,3-
tetramethylbutyl)phenyl]- co-hydroxypolyoxy-l,2-ethane diyl).
The surfactants used in the pharmaceutical ophthalmic suspension for enhancing
dispersion stability preferably include nonionic surfactant(s). The nonionic surfactant to be used
is nontoxic, non-irritant and applicable to the eye. Non-limiting examples of the nonionic
surfactant include but are not limited to polymer of the alkyl aryl polyether alcohol like
tyloxapol; polyoxyethylene polyoxypropylene polymer like triton X-100;
polyoxyethylenesorbitan fatty acid esters such as polyoxyethylenesorbitan monooleate,
polyoxyethylenesorbitan monolaurate, polyoxyethylenesorbitan monopalmitate and
polyoxyethylenesorbitan monostearate; polyoxyethylene hydrogenated castor oils; sorbitan fatty
acid esters such as sorbitan monooleate, sorbitan monolaurate, sorbitan monopalmitate and
sorbitan monostearate; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; and
polyoxyethylene fatty acid esters such as polyoxyethylene monostearate and mixtures thereof. Of
the recited nonionic surfactants, alkyl aryl polyether alcohol like tyloxapol, polyoxyethylene
polyoxypropylene polymer like triton X-100 are preferable, since they suppress formation of
agglomerates, prevent lowering of pH, and provide a suspension superior in redispersibility and
stability. The nonionic surfactant is generally contained in a proportion of from about 0.005 w/v
% to about 1.0 w/v %, preferably from about 0.01 to about 0.5 w/v % and more preferably from
about 0.05 w/v % to about 0.3 w/v % relative to the entire suspension.
Examples of tonicity agents that may be used according to the invention include but are
not limited to mannitol, dextrose, glycerin, potassium chloride, sodium chloride and mixtures
thereof. The tonizing agent is added in such an amount that makes the osmotic pressure of the
suspension identical to that of tears, preferably tonicity agents may be used in amount from about
l% to about 5%.
The pharmaceutical ophthalmic suspension may further include a buffer. The buffer
should have buffering capacity in the range of pH from about 5.0 to about 9.0. Examples of the
buffer include but are not limited to acetates such as sodium acetate; phosphates such as sodium
dihydrogenphosphate, disodium hydrogenphosphate, potassium dihydrogenphosphate and
11
dipotassium hydrogenphosphate; .epsilon.- aminocaproic acid; amino acid salts such as sodium
glutamate; and boric acid and a salt thereof. Of the mentioned buffers, acetates and .epsilon.-
aminocaproic acid are preferable as they suppress formation of agglomerates, prevent lowering
of pH, and provide a suspension superior in re-dispersibility and stability. The buffer is generally
contained in a proportion of form about 0.01 w/v % to about 2.0 w/v %, preferably form about
0.05 w/v % to about 0.5 w/v % relative to the entire suspension.
Examples of the pH adjusting agent include but are not limited to hydrochloric acid, citric
acid, phosphoric acid, acetic acid, tartaric acid, sodium hydroxide, potassium hydroxide, sodium
carbonate and sodium hydrogen carbonate. The pharmaceutical ophthalmic suspension is
generally adjusted to pH from about 5.0 to about 9.0, the range which is less irritating to the
mucosal membrane of the eye.
Suitable chelating agents include but are not limited to edetate disodium, edetate
trisodium, edetate tetrasodium, diethyleneamine pentaacetate and mixtures thereof. Most
preferred is edetate disodium. The chelating agent is generally present in an amount from about
0.001 w/v % to about 0.1 w/v % relative to the entire suspension. In the case of edetate disodium,
the chelating agent is preferably present at a concentration of from about 0.005 w/v % to about
0.05 w/v % relative to the entire suspension.
Examples of the antioxidant include but are not limited to ascorbic acid, sodium
ascorbate, tocopherol and sulfite salts like sodium sulfite, potassium sulfite, magnesium sulfite,
calcium sulfite, sodium bisulfite, potassium bisulfite, magnesium bisulfite, calcium bisulfite,
sodium metabisulfite, potassium metabisulfite, calcium metabisulfite, sodium thiosulfate and
sodium hydrogensulfite. The sulfite salt is generally being present in an amount from about 0.01
w/v % to about 1 % w/v % relative to the entire suspension.
The average particle size of the dispersed or the suspended active is generally from about
0.01 μ - to about 50 μ, preferably from about 0.01 μ - to about 30 μ, more preferably from about
0.1 μ - to about 20 μ and most preferably from about 0.1 μ - to about 5.0 μ. The use of the active
in this particle size range affords a suspension having superior dispersibility, which is less
irritating to the mucosal membrane of the eye.
12
Any pharmaceutically acceptable packaging material may be use, preferably packaging
material that is suitable for containing ophthalmic pharmaceutical suspensions.
The ophthalmic pharmaceutical suspension is preferably sterile. An article comprising the
ophthalmic pharmaceutical suspension filled in a container is preferably sterile, preferably at the
time the container is filled. The ophthalmic pharmaceutical suspension is preferably filled into
sterile multi-use or single-use containers.
Pharmaceutically acceptable packaging materials include but are not limited to low
density polyethylene ("LDPE"), high density polyethylene ("HDPE"), polypropylene,
polystyrene, polycarbonate, polyesters (such as polyethylene terephthalate and polyethylene
naphthalate), nylon, polyvinyl chloride), poly(vinylidine chloride), poly(tetrafluoroethylene) and
other materials known to those of ordinary skill in the art. Flexible bottles prepared from, or
comprising, LDPE, HDPE or polypropylene are particularly preferred.
In another embodiment of the present invention, the homogenized ophthalmic suspension
of sterile brinzolamide prepared according to the process as described herein may be filled in
three piece low density polyethylene bottle (LDPE), of suitable capacity in volumes of 2.5ml,
5ml, 10ml and 15ml plugged with natural (LDPE) nozzle and seal with orange colored high
density polyethylene (HDPE) cap.
Any suitable method can be used to sterilize the containers, and can be determined by the
person of ordinary skill in the art. Some preferred methods include exposure to gamma
irradiation and/or exposure to ethylene oxide gas.
The present invention provides a method of using the ophthalmic pharmaceutical
formulation for treating ocular hypertension and glaucoma.
The preferred active ingredient includes but are not limited to the active which is useful
in the treatment or prevention of diseases associated to eye like elevated intraocular pressure in
patients with ocular hypertension or open-angle glaucoma, ocular surface pain, uveitis, scleritis,
episcleritis, keratitis, surgically-induced inflammation, endophthalmitis, iritis, atrophic macular
degeneration, retinitis pigmentosa, iatrogenic retinopathy, retinal tears and holes, cystoid macular
edema, diabetic macular edema, diabetic retinopathy, sickle cell retinopathy, retinal vein and
13
artery occlusion, optic neuropathy, exudative macular degeneration, neovascular glaucoma,
corneal neovascularization, cyclitis, sickle cell retinopathy, pterygium, seasonal allergic
conjunctivitis, palpebral and bulbar conjunctiva, acne rosacea, superficial punctuate keratitis,
herpes zoster keratitis, iritis, cyclitis, selected infective conjunctivitides, post-operative
inflammation following ocular surgery.
The main embodiment of the present invention provides an improved process of manufacturing a
sterile, ophthalmic pharmaceutical suspension comprising a sterile active ingredient, at least one
surfactant, wherein the said process comprises steps of:
i. subjecting a suspension of the sterile active ingredient in an aqueous solution of
surfactant to homogenization to form a mixture; and,
ii. combining the mixture formed in step (a) with the rest of the inactive ingredients,
wherein inactive ingredients comprises of:
a) at least one polymer(s),
b) at least one or two tonicity agent(s) or combinations thereof, and
c) optionally a pharmaceutically acceptable preservative; wherein the process
doesn’t involve the use of any special equipment’s such as ball mill,
milling bottle and/or, jet mill to achieve desired particle size.
In another embodiment of the present invention, the sterile active ingredient is a sterile
carbonic anhydrase inhibitor.
In another embodiment of the present invention, the sterile carbonic anhydrase inhibitor
is sterile brinzolamide.
In another embodiment of the present invention, the manufacturing process reduces the
generation of Impurity A.
In another embodiment of the present invention, the ophthalmic pharmaceutical
suspension upon storage for 3 months, comprises less than 0.4 w/v % of Impurity A (S)-4-
(ethylamino)-3,4-dihydro-2-(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide
1,1-dioxide.
In another embodiment of the present invention, wherein the surfactant is selected from
the group consisting of Tyloxapol(R), Triton X-100(R), polysorbates, polyoxyl 35 castor oil,
14
polyoxyl 40 hydrogenated castor oil, polyoxyl 40 stearates, sorbitan monolaureates, poloxamer
and the mixture thereof.
In another embodiment of the present invention, wherein the polymer is selected from the
group consisting of Carbomer(R), povidone, hydroxypropyl methyl cellulose, hydroxypropyl
cellulose, hydroxyethyl cellulose and the mixture thereof.
In another embodiment of the present invention, wherein the preservative is selected from
the group consisting of benzethonium chloride, phenyl ethanol, phenyl propanol, phenyl
mercuric acetate, phenyl mercuric nitrate, phenyl mercuric borate, chlorhexidine acetate or
gluconate, cetrimide, chlorocresol, sodium methyl paraben, sodiumpropyl paraben, thimerosal,
benzalkonium chloride and the mixture thereof.
In another embodiment of the present invention, wherein the tonicity agents are selected
from the group consisting of mannitol, dextrose, glycerin, potassium chloride, sodium chloride
and the mixture thereof.
In another embodiment of the present invention, wherein the chelating agents if used,
include edetate disodium, edetate trisodium, edetate tetrasodium, diethyleneamine pentaacetate
and the mixture thereof.
In another embodiment of the present invention, the homogenization is carried out by
using high pressure homogenization at pressure 1000±200 bar for uniform dispersion.
In another embodiment of the present invention, the process does not involve the use of
any special equipment’s such as ball mill, milling bottle and/or jet mill.
Yet another embodiment of the present invention provides a sterile, ophthalmic
pharmaceutical suspension as prepared by the claimed process of manufacturing.
Yet another embodiment of the present invention provides a process of manufacturing a
sterile, ophthalmic pharmaceutical suspension comprising a carbonic anhydrase inhibitor (CAI),
which comprises the steps of:
a) preparing a solution comprising polymers, chelating agents, one or more tonicity
agents and optionally a pharmaceutically acceptable preservative.
b) adjusting the pH of the solution of step a) between 7.5 ± 0.3 by adding sodium
hydroxide/ hydrochloric acid, in increments, if required.
c) sterilizing the bulk of step a) by in-situ sterilization.
d) preparing a surfactant solution in another pressure vessel.
e) filtering a surfactant solution of step d) through 0.2 μ filter.
15
f) adding aseptically sterile API to the above surfactant solution of step e).
g) homogenizing the above slurry using high pressure homogenizer at pressure
1000±200 bar to achieve uniform dispersion.
h) transfering this homogenized slurry into sterile bulk in filtration tank of step c).
In another embodiment of the present invention, the ophthalmic pharmaceutical
suspension is stable when stored for 3 months at 40°C at no more than 25% relative humidity.
In another embodiment of the present invention, the ophthalmic pharmaceutical
suspension is packaged in a multi dose container.
In another embodiment of the present invention, the ophthalmic pharmaceutical
suspension is packaged in a unit dose container.
Yet another embodiment of the present invention provides a sterile, ophthalmic
pharmaceutical suspension as prepared by the claimed process of manufacturing.
In another embodiment of the present invention, wherein the ophthalmic pharmaceutical
suspension is used for treating elevated intraocular pressure in persons suffering from ocular
hypertension or primary open angle glaucoma, comprising applying once a day to an eye of a
patient in need thereof.
In another embodiment of the present invention, the applying of ophthalmic solution is
done twice a day.
In another embodiment of the present invention, the applying of ophthalmic solution is
done at least once a day.
STABILITY STUDIES:
A sterile, ophthalmic pharmaceutical suspension of the present invention is prepared by
the process described herein in the specification and is tested for stability against a control
product (herein referred to as “AZOPT(R)”). Three (3) months accelerated testing refers to
storage at 40° C, at not more than 25% relative humidity (RH). Results for 3-months accelerated
testing for both the control product (herein referred to as “AZOPT(R)”) and the present invention
formulation are provided in Table 1.
16
An accelerated study comprises placing the composition/suspension is filled in 10 mL 3
piece natural LDPE bottles, natural LDPE nozzle and orange colored cap. (Sterilized by ETO gas
Sterilization) and maintaining at 40° C, at not more than 25% relative humidity (RH) in the dark.
As understood by those of skill in the art, when the drug comprises brinzolamide, the
impurities preferably measured include Impurity A (S)-4-(ethylamino)-3,4-dihydro-2-(3-
methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide 1,1-dioxide; Impurity B, (R)-4-
(amino)-3,4-dihydro-2-(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide 1,1-
dioxide, Impurity C (S)-4-(hydroxy)-3,4-dihydro-2-(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-
thiazine-6-sulfonamide 1,1-dioxide and Impurity D 6-(amino-hydroxy-oxo-6-sulfanyl)-2-(3-
methoxypropyl)-1,1-dioxo-3H-thieno[3,2-e]thiazin-4-one and total impurities, as well as
identification of the amount of the any independent unspecified impurity.
TABLE 1: Comparative Stability Data of “Reference listed drug” AZOPT(R) and present
invention formulation.
Batch No.
Release
Specifications Initial
Shelf life
Specifications
40°C/25% RH
Assay 1 Month 3 Months
RLD (AZOPT(R)) B.
No. 203168F
93.0 – 107.0
%
of labeled
amount
98.6% 90.0 – 110.0
% of
labeled
amount
100.2% 100.7%
Exhibit batch E14010 97.8% 99.4% 99.5%
Impurity
Related compound A
(Impurity A)
RLD (AZOPT(R)) B.
No. 203168F NMT 1.0 %
0.91%
NMT 1.5 %
0.96% 1.39%
Exhibit batch E14010 ND 0.08% 0.25%
Related compound B
(Impurity B)
RLD (AZOPT(R)) B. NMT 0.4% 0.05% NMT 0.5 % 0.05% 0.04%
17
No. 203168F
Exhibit batch E14010 0.13% 0.15% 0.17%
Related compound D
(Impurity D)
RLD (AZOPT(R)) B.
No. 203168F NMT 0.4%
ND
NMT 0.5 %
ND ND
Exhibit batch E14010 0.01% ND 0.02%
Any individual
impurity
RLD (AZOPT(R)) B.
No. 203168F NMT 0.4%
0.08% NMT 0.5 %
0.10% 0.18%
Exhibit batch E14010 0.11% 0.14% 0.15%
Total impurities
RLD (AZOPT(R)) B.
No. 203168F NMT 1.0%
0.12%
NMT 2.0 %
0.15% 0.35%
Exhibit batch E14010 0.25% 0.29% 0.34%
As used herein, the “NMT” wherever appears is an abbreviation for “Not more than”.
As used herein, the “ND” wherever appears is an abbreviation for “Not detected”.
DETAILS OF THE BATCHES:
Batch No. Mfg. date/Expiry date Date of initiation of study
Exhibit batch E14010 Mfg. date: May 14 31 May 14
RLD (AZOPT(R)) B. No.
203168F manufactured by
Alcon Laboratories Inc.
Exp. Date: Mar 14 29 Nov 13
18
Table 2: Comparative data of different lots of RLD from different markets
Russia RLD EU RLD US RLD
Batch No. 13F21F 12F19G 203411F 203168F 231374F
Expiry date Jun 15 May 14 Apr 14 Mar 14 May 16
Date of analysis Nov 13 Nov 13 May 13 Nov 13 Sep 14
Approximate age of
the product at the time
of analysis
5 months* 1.5 years* 1 year* 1.7 year* 4 months*
Assay (By HPLC) 98.90% 100.50% 102.00% 98.58% 97.30%
Related compound A
(Impurity A)
0.86% 0.60% 0.90% 0.91% 0.75%
Impurity B 0.05% 0.04% 0.05% 0.05% 0.05%
Impurity D ND ND ND ND 0.01%
Any individual
impurities
0.07% 0.13% 0.04% 0.08% 0.32%
Total impurity 0.12% 0.24% 0.22% 0.13% 0.38%
* Approximate age of the product at the time of analysis based on anticipated two (2) years of shelf life.
OBSERVATIONS
It is observed from the stability data that due to an improved process, formation of related
substance A (Impurity A) at initial time point is much less in present invention formulation than
RLD (AZOPT(R)) due to which its formation over the time at accelerated condition has
decreased.
In case of RLD, the impurity A has increased from 0.91% (at initial) to 1.39% in three (3)
months at accelerated condition whereas in case of present invention formulation the impurity
was not detected at initial analysis and has increased to 0.25% over three (3) months at same
condition indicating that the rate of increase of impurity A has decreased by exactly half in case
of present invention formulation due to an improved process.
19
The impurity A of RLD is more than the present invention formulation whether the analysis
is done near to the expiry of the RLD or one (1) year before its expiry, as it can be seen from the
table that initial assay of impurity A is not correlating well with the age of the product. This
supports the statement that manufacturing process is a main contributor for the formation of
impurity A. Impurity A is also formed on stability. However controlling Impurity A by
manufacturing process gives a better control over it.
Some other parameters like content of BKC, content of Edetate Disodium, Osmolality,
Viscosity, pH and Particle Size were also analyzed and were found to be within specifications
and comparable with the RLD.
CONCLUSION:
From the above stability results it can be easily concluded that the present invention
formulation complies with the specifications as per USP and in–house specification throughout
the study and is comparable with the RLD.
It is also concluded that the present invention formulation is more stable over the period of
three (3) months at accelerated condition (40±2ºC/25%RH) and stability data is well within the
specifications and comparable with the RLD (AZOPT(R)). Hence the present invention
formulation prepared by the improved process is more patient compliant.
Further, it is also concluded that the manufacturing process of the present invention reduces
the generation of Impurity A wherein the reduction of Impurity A will enhance the shelf-life of
the product thereby increases the stability of the present invention.
Furthermore, the ophthalmic pharmaceutical suspension of the present invention upon
storage for 3 months, comprises less than 0.4 w/v % of Impurity A (S)-4-(ethylamino)-3,4-
dihydro-2-(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide 1,1-dioxide.
Zeta Potential
The Study was done in the Malvern Application Laboratory (Delhi) which is a joint venture
between Malvern Instruments (UK), a particle characterization and Rheological instrumentation
manufacturer, and Aimil Ltd (India), “India’s leading civil engineering instrumentation
manufacturer’’. Malvern’s Zetasizer ZS90 was used for the study.
20
Zeta potential was determined from three (3) Azopt (RLD) batches, 2 batches made in Inhouse
lab and a placebo batch. Due to the high viscosity of the formulation, it was very difficult
to measure the zeta potential. So zeta potential was determined for all the above batches after
diluting 10 times. The results are shown in the Table 5.
Table 5: Zeta potential data of In-house batches and RLD
INFERENCE:
Based on the above data, the zeta potential for Sentiss batches and Azopt were similar and there
was no significant difference between them. Further, high negative value of placebo is indicative
of high viscosity with high polymeric cross links. Hence, suspension stability is maintained by
high polymeric network and not by electric charge. The present invention is further illustrated by
reference to the following examples which is for illustrative purpose only and does not limit the
scope of the invention in any way.
EXAMPLES:
The scope of the present invention is illustrated by the following examples which are not
meant to restrict the scope of the invention in any manner whatsoever.
Batch No. Mfg. date Measured after 10
times dilution
PR3F054-18B (Present invention) Jul 13, In-house Lab -34.5
PR3F054-10 (Present invention) May 13, In-house Lab -32.7
203411F (Azopt) Alcon USA (Exp.-
04/2014)
-33.9
12F19G (Azopt) Alcon, UK (Exp.-
05/2014)
-31.9
PR3F054-35P (Placebo) Oct 13, In-house Lab -35.8
21
The term 'q.s.' wherever appears in the examples is an abbreviation for 'quantity sufficient' which
is the amount of the excipient in such quantities that is just sufficient for its use in the
composition of the present invention.
Example 1:
Ingredients Quantity (%)
Brinzolamide 1
Tyloxapol 0.025
Carbomer 974P 0.45
Edetate disodium 0.01
BKC 0.01
Mannitol 3.3
Sodium Chloride 0.25
NaOH/HCl q.s.
Water for Injection Up to 100%
Example 2:
Ingredients Quantity (%)
Brinzolamide 1.0
Tyloxapol 0.025
Carbomer 974P 0.42
Edetate disodium 0.01
Benzalkonium Chloride 0.01
Mannitol 3.3
Sodium chloride 0.25
Sodium
hydroxide/Hydrochloric acid
q.s.
Water for Injection q.s.
Brief manufacturing procedure:
The process for preparation of pharmaceutical ophthalmic suspension shall be divided in
following parts.
1. Remaining product vehicle (solution of EDTA, Mannitol, Carbomer, sodium chloride,
Benzalkonium chloride) (37 kg)
2. Tyloxapol solution/API slurry
22
3. Slurry Homogenization (by mixing Tyloxapol solution)
4. Water for injection.
Part A. Remaining product vehicle:
5. Weigh and check the weight of all ingredients.
6. Take approximately 120% of required quantity of Water for injection in a Manufacturing
tank -1
7. Purge filtered Nitrogen gas and Cool Water for Injection, using cooling jacket to 30ºC
(range 25º to 35ºC), through sparger till the dissolved oxygen level reaches to not more
than 2 ppm.
8. Transfer 60 % of required quantity of cooled water for injection from manufacturing tank
-1 to Manufacturing tank -2.
9. Add and dissolve edetate disodium in the Manufacturing tank -2 with continuous stirring.
10. Add and dissolve Mannitol in the Manufacturing tank -2 with continuous stirring
11. Add and dissolve carbomer 974P slowly in the Manufacturing tank -2 with continuous
stirring.
12. Add and dissolve sodium chloride in the Manufacturing tank -2 with continuous stirring
at RPM 350±50.
13. Add and dissolve diluted Benzalkonium chloride solution in the Manufacturing tank -2
with continuous stirring. Rinse the container multiple times with sufficient water for
injection for complete transfer.
14. Adjust the pH of the solution between 7.5 ± 0.3 by adding 5 N Sodium Hydroxide/ 1N
Hydrochloric Acid, in increments, if required. Stir solution for 5 min between each
increment.
15. Make up the weight of bulk solution to 37 kg.
16. Transfer the above bulk solution from manufacturing tank-2 to filtration tank through
20μ Polypropylene filter. Record the loss during transfer.
17. Sterilize the bulk in filtration tank by in-situ sterilization (30min, NLT 121.6ºC, 1 cycle)
23
Part B. Tyloxapol solution
18. In separate pressure vessel prepare the solution of Tyloxapol by collecting 3-4 L water
for injection in pressure vessel and dissolve the dispensed batch quantity in hot water for
injection and adding this to pressure vessel. Make up the volume to 10% of batch size.
19. Filter this solution through 0.2 μ filter into filtration area (5 L tank).
Part C. Slurry Homogenization (by mixing Tyloxapol solution)
20. Add aseptically sterile API to the above tyloxapol solution.
21. Stir the slurry for not less than 3hr using magnetic stirrer at sufficient RPM to generate
vortex and avoiding high turbulence.
22. Create loop to facilitate the recirculation in homogenization process and its transfer to
filtration tank. Homogenize the slurry using high pressure homogenizer at pressure
1000±200 bar for 2 hr (for 50 L batch size)
23. Transfer this homogenized slurry into sterile bulk in filtration tank.
24. Rinse the slurry tanks (5L tank) with aseptically filtered, approximately 5L water (Refer
Part D for details) and add this rinsate to sterile bulk in filtration tank through
homogenizer (at pressure 1000±200 bar)
25. Make the bulk weight considering density 1.016 g/ml in filtration tank using sterile water
for injection. used in rinsing of 5L tank.
26. Continue the stirring to get a uniform bulk. Stir it for 2 hr and send the samples for bulk
analysis.
Part D: Pre-sterilized water for injection
27. Collect water for injection into manufacturing tank 1, filter it through 0.2 μ filter, used
for filtering tyloxapol solution & collect in 5L tank (used for slurry) and use this for
volume make up in filtration tank.
24
Example 3
Ingredients Quantity (%)
Brinzolamide 1.0
Tyloxapol 0.025
Carbomer 974P 0.42
Edetate disodium 0.01
Mannitol 3.3
Sodium chloride 0.25
Sodium hydroxide/Hydrochloric acid q.s.
Water for Injection q.s.
Brief manufacturing procedure:
The process for preparation of pharmaceutical ophthalmic suspension shall be divided in
following parts.
1. Remaining product vehicle (solution of EDTA, Mannitol, Carbomer, sodium chloride)
2. Tyloxapol solution/API slurry
3. Slurry Homogenization (by mixing Tyloxapol solution)
4. Water for injection.
Part A. Remaining product vehicle:
5. Weigh and check the weight of all ingredients.
6. Take approximately 120% of required quantity of Water for injection in a Manufacturing
tank -1
7. Purge filtered Nitrogen gas and Cool Water for Injection, using cooling jacket to 30ºC
(range 25º to 35ºC), through sparger till the dissolved oxygen level reaches to not more
than 2 ppm.
8. Transfer 60 % of required quantity of cooled water for injection from manufacturing tank
-1 to Manufacturing tank -2.
9. Add and dissolve edetate disodium in the Manufacturing tank -2 with continuous stirring.
10. Add and dissolve Mannitol in the Manufacturing tank -2 with continuous stirring
25
11. Add and dissolve carbomer 974P slowly in the Manufacturing tank -2 with continuous
stirring.
12. Add and dissolve sodium chloride in the Manufacturing tank -2 with continuous stirring
at RPM 350±50.
13. Rinse the container multiple times with sufficient water for injection for complete
transfer.
14. Adjust the pH of the solution between 7.5 ± 0.3 by adding 5 N Sodium Hydroxide/ 1N
Hydrochloric Acid, in increments, if required. Stir solution for 5 min between each
increment.
15. Make up the weight of bulk solution to 37 kg.
16. Transfer the above bulk solution from manufacturing tank-2 to filtration tank through
20μ Polypropylene filter. Record the loss during transfer.
17. Sterilize the bulk in filtration tank by in-situ sterilization (30min, NLT 121.6ºC, 1 cycle)
Part B. Tyloxapol solution
18. In separate pressure vessel prepare the solution of Tyloxapol by collecting 3-4 L water
for injection in pressure vessel and dissolve the dispensed batch quantity in hot water for
injection and adding this to pressure vessel. Make up the volume to 10% of batch size.
19. Filter this solution through 0.2 μ filter into filtration area (5 L tank).
Part C. Slurry Homogenization (by mixing Tyloxapol solution)
20. Add aseptically sterile API to the above tyloxapol solution.
21. Stir the slurry for not less than 3hr using magnetic stirrer at sufficient RPM to generate
vortex and avoiding high turbulence.
22. Create loop to facilitate the recirculation in homogenization process and its transfer to
filtration tank. Homogenize the slurry using high pressure homogenizer at pressure
1000±200 bar for 2 hr (for 50 L batch size)
23. Transfer this homogenized slurry into sterile bulk in filtration tank.
26
24. Rinse the slurry tanks (5L tank) with aseptically filtered, approximately 5L water (Refer
Part D for details) and add this rinsate to sterile bulk in filtration tank through
homogenizer (at pressure 1000±200 bar)
25. Make the bulk weight considering density 1.016 g/ml in filtration tank using sterile water
for injection. used in rinsing of 5L tank.
26. Continue the stirring to get a uniform bulk. Stir it for 2 hr and send the samples for bulk
analysis.
Part D. Pre-sterilized water for injection.
27. Collect water for injection into manufacturing tank 1, filter it through 0.2 μ filter, used
for filtering tyloxapol solution & collect in 5L tank (used for slurry) and use this for
volume make up in filtration tank.
Further the particle size and morphology obtained by the present invention process is
similar to that of ball milling process as shown in Table 3. However the current process is much
more efficient and economical compared to the ball mill process. The particle size analysis is
measured by Liquid particle counter.
Table 3: Comparison of particle size between present invention
formulation of brinzolamide ophthalmic suspension 1.0% and
Reference listed drug (AZOPT(R)).
Particle size
RLD Present Invention
Lot No. 203411F Lot No. PR3F054-10
% < 10μ Particles 94.0% 99.0%
% < 25μ Particles 100.0% 100.0%
% < 50μ Particles 100.0% 100.0%
% < 100μ Particles 100.0% 100.0%
For development studies, particle size evaluation has been also performed using Morphology G3
instrument from Malvern at Aimil Labs in Vadodara as shown in Table 4.
27
Table 4: Comparison of particle size between present invention formulation of
brinzolamide ophthalmic suspension 1.0% and Reference listed drug (AZOPT(R))
Particle size
RLD Present Invention
203411F PR3F054-10
D(0.9) 1.89μ 3.02μ
D(0.5) 1.21μ 2.01μ
D(0.1) 0.75μ 1.38μ
From the particle size analysis as depicted above in Table 4, it is inferred that present
invention formulation of brinzolamide ophthalmic suspension 1.0% is comparable with
Reference listed drug i.e. AZOPT(R) , manufactured by Alcon Pharmaceuticals.
UTILITY OF THE PRESENT INVENTION
The present inventors provides a simpler, cost effective and efficient process for
manufacturing sterile, ophthalmic pharmaceutical suspension comprising CAI without the use of
use of any special equipment such as ball mill, milling bottle and/or, jet mill. The prepared
suspension is useful in treatment of elevated intraocular pressure in patients with ocular
hypertension or, open angle glaucoma.
28
WE CLAIM:
1. An improved process of manufacturing a sterile, ophthalmic pharmaceutical suspension
comprising a sterile active ingredient, at least one surfactant, wherein the said process
comprises steps of:
i. subjecting a suspension of the sterile active ingredient in an aqueous solution of
surfactant to homogenization to form a mixture; and,
ii. combining the mixture formed in step (a) with the rest of the inactive
ingredients, wherein inactive ingredients comprises of:
a) at least one polymer(s),
b) at least one or two tonicity agent(s) or combinations thereof, and
c) optionally a pharmaceutically acceptable preservative; wherein the process
doesn’t involve the use of any special equipment’s such as ball mill,
milling bottle and/or, jet mill to achieve desired particle size.
2. The process as claimed in claim 1, wherein the sterile active ingredient is a sterile
carbonic anhydrase inhibitor.
3. The process as claimed in claims 1 to 2, wherein the sterile carbonic anhydrase inhibitor
is sterile brinzolamide.
4. The process as claimed in claims 1 to 3, wherein the manufacturing process reduces the
generation of Impurity A.
5. The ophthalmic pharmaceutical suspension as claimed in claims 1 to 4, which upon
storage for three months, comprises less than 0.4 w/v % of Impurity A (S)-4-
(ethylamino)-3,4-dihydro-2-(3-methoxypropyl)-2H-thieno[3,2-e]-1,2-thiazine-6-
sulfonamide 1,1-dioxide.
6. The process as claimed in claim 1, wherein the surfactant is selected from the group
consisting of Tyloxapol(R), Triton X-100(R), polysorbates, polyoxyl 35 castor oil,
polyoxyl 40 hydrogenated castor oil, polyoxyl 40 stearates, sorbitan monolaureates,
poloxamer and the mixture thereof.
29
7. The process as claimed in claim 1, wherein the polymer is selected from the group
consisting of Carbomer(R), povidone, hydroxypropyl methyl cellulose, hydroxypropyl
cellulose, hydroxyethyl cellulose and the mixture thereof.
8. The process as claimed in claim 1, wherein the preservative is selected from the group
consisting of benzethonium chloride, phenyl ethanol, phenyl propanol, phenyl mercuric
acetate, phenyl mercuric nitrate, phenyl mercuric borate, chlorhexidine acetate or
gluconate, cetrimide, chlorocresol, sodium methyl paraben, sodiumpropyl paraben,
thimerosal, benzalkonium chloride and the mixture thereof.
9. The process as claimed in claim 1, wherein the tonicity agents is selected from the group
consisting of mannitol, dextrose, glycerin, potassium chloride, sodium chloride and the
mixture thereof.
10. The process as claimed in claim 1, wherein the chelating agents if used, include edetate
disodium, edetate trisodium, edetate tetrasodium, diethyleneamine pentaacetate and the
mixture thereof.
11. The process as claimed in claim 1, wherein homogenization is carried out by using high
pressure homogenization at pressure 1000±200 bar for uniform dispersion.
12. The process as claimed in claim 1, wherein the process does not involve the use of any
special equipment’s such as ball mill, milling bottle and/or jet mill.
13. A sterile, ophthalmic pharmaceutical suspension as prepared by the process as claimed in
claim 1.
14. A process of manufacturing a sterile, ophthalmic pharmaceutical suspension comprising a
carbonic anhydrase inhibitors (CAIs), comprises steps of:
a) preparing a solution comprising polymers, chelating agents, one or more tonicity
agents and optionally a pharmaceutically acceptable preservative;
30
b) adjusting the pH of the solution of step a) between 7.5 ± 0.3 by adding sodium
hydroxide/ hydrochloric acid, in increments, if required;
c) sterilizing the bulk of step a) by in-situ sterilization;
d) preparing a surfactant solution in another pressure vessel;
e) filtering a surfactant solution of step d) through 0.2 μ filter;
f) adding aseptically sterile API to the above surfactant solution of step e);
g) homogenizing the above slurry using high pressure homogenizer at pressure
1000±200 bar to achieve uniform dispersion;
h) transferring this homogenized slurry into sterile bulk in filtration tank of step c).
15. The ophthalmic pharmaceutical suspension as claimed in claims 1 and 14, wherein the
suspension is stable when stored for 3 months at 40°C at no more than 25% relative
humidity.
16. The ophthalmic pharmaceutical suspension as claimed in claims 1 to 15, wherein the
ophthalmic suspension is packaged in a multi dose container.
17. The ophthalmic pharmaceutical suspension as claimed in claims 1 to 15, wherein the
ophthalmic suspension is packaged in a unit dose container.
18. A sterile, ophthalmic pharmaceutical suspension as prepared by the process as claimed in
claim 14.