FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
STABLE SOLUTIONS OF NADIFLOXACIN OR SALTS THEREOF AND
THEIR METHODS OF PREPARATION
2. APPLICANT (S)
(a) NAME: WOCKHARDT LTD.
(b) NATIONALITY: INDIAN
(c) ADDRESS: Wockhardt Towers, Bandra-Kurla Complex, Bandra
(East), Mumbai-400 051.
3. PREAMBLE TO THE DESCRIPTION
The present invention relates to stable solutions suitable for ophthalmic, otic, or nasal administration that include nadifloxacin and pharmaceutically acceptable salts thereof. The invention also relates to processes for the preparation of the stable solutions.
The following specification particularly describes the invention and the manner in which it is to be performed.
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4. DESCRIPTION
The present invention relates to stable solutions suitable for ophthalmic, otic, or nasal administration that include nadifloxacin and pharmaceutically acceptable salts thereof. The invention also relates to processes for the preparation of the stable solutions.

Chemically, nadifloxacin is 9-fluoro-6,7-dihydro-8-(4-hydroxy-1-pyperidinyl)-5-methyl-1-oxo-1H,5H-benzo(l,j)quinolizine-2-carboxylic acid of Formula I provided below.

Nadifloxacin is a synthetic quinolone with potent broad-spectrum anti-bacterial activity. Nadifloxacin inhibits the enzyme DNA gyrase that is involved in bacterial DNA synthesis and replication, thus inhibiting the bacterial multiplication. RS-nadifloxacin and S-nadifloxacin, in particular, exhibit strong antibacterial activity against Gram-positive, Gram-negative and anaerobic bacteria, resistant Gram-positive organisms such as methicillin-resistant Staphylococcus aureus (MRSA), quinolone-resistant Staphylococcus aureus, coagulase negative staphylococci, such as methicillin-resistant Staphylococcus epidermidis (MRSE), enterococci, betahemolytic streptococci and viridans group of streptococci, mycobacteria and newly emerging nosocomial pathogens such as Chryseobacterium meningosepticum, and Gram-negative pathogens such as E.coli, Klebsiella, Proteus, Serratia, Citrobacter and Pseudomonas. Recently, it has also been shown that S-(-)-nadifloxacin, in particular exhibits potent antibacterial activity against glycopeptide intermediate S. aureus (GISA), vancomycin intermediate S.
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aureus (VISA) and vancomycin-resistant S. aureus (VRSA). Nadifloxacin is also active against quinolone-resistant Staphylococci.
Nadifloxacin is marketed in the form of cream for topical application for the treatment of acne vulgaris, folliculitis and sycosis vulgaris. It is also indicated for the treatment of topical bacterial infections with susceptible bacteria.
U.S. Patent No 4,399,134 discloses processes for the preparation of nadifloxacin or salts thereof and antibacterially effective pharmaceutical compositions of nadifloxacin. Typical dosage forms include tablets, pills, powders, liquid preparations, suspensions, emulsions, granules, capsules, suppositories, and injectable preparations (solutions, suspensions, etc).
U.S. Patent No 6,884,768 discloses solid oral pharmaceutical compositions that includes nadifloxacin, an absorbefacient and taurine compounds.
U.S. Patent Application 20060183698 describes topical ophthalmic formulation that includes serum electrolytes; an antimicrobial compound and an antiinflammatory or steroidal compound. Several antimicrobial agents have been disclosed including nadifloxacin.
U.S. Patent Application 20040176337 discloses topical compositions of benzoquinolizine-2-carboxylic acid antimicrobial drug.
U.S. Patent Application 20040176321 discloses injectable pharmaceutical composition for intravenous delivery of an active agent that includes RS-(±)-nadifloxacin; S-(-)-nadifloxacin and hydrates thereof; or S-(-)-nadifloxacin arginine and salts thereof.
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PCT Publication WO 04/00360 describes pharmaceutical compositions of several active ingredients including nadifloxacin for topical use for treatment of dermatosis.
PCT Publication WO 00/06122 describes taste-masked pharmaceutical compositions for oral administration containing nadifloxacin.
Journal of Ocular Pharmacology and Therapeutics, vol 23(3): 243-256, 2007 discloses (7-[(3R)-3-aminohexahydro-1H-azepine-1-yl]-8-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylivc acid as the topical agent for the treatment of ophthalmic infections.
The use of quinolone antibiotics to treat infections is known art in the field of ophthalmic pharmaceutical compositions and methods of treatment. Several quinolone antibacterial agents available in the market include gatifloxacin (available as Zymar®), Levofloxacin (available as Quixin® or Iquix®), Ciprofloxacin (available as Ciloxan®), Ofloxacin (available as Ocuflox®), Lomefloxacin (available as Lomeflox®), Moxifloxacin (available as Vigamox®) and Norfloxacin (available as Chibroxin®).
U.S. Patent No 6,333,045 discloses liquid pharmaceutical compositions of gatifloxacin or salt thereof and disodium edetate. European Patent EP 275,515 and U.S. Patent No 4,923,862 disclose aqueous pharmaceutical compositions of levofloxacin and ofloxacin or salts thereof. U.S. Patent No 6,716,830 discloses ophthalmic dosage forms of moxifloxacin or salts thereof in a concentration of 0.1% to 1% w/w and pharmaceutically acceptable vehicle.
The foregoing quinolone antibiotic compositions are generally effective in treating ophthalmic infections, and have distinct advantages over prior ophthalmic antibiotic compositions, particularly those having relatively limited spectrum of antimicrobial activity, such as: neomycin, polymyxin B, gentamicin
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and tobramycin, which are primarily useful against gram negative pathogens; and bacitracin, gramicidin, and erythromycin, which are primarily active against gram positive pathogens.
However, despite the general efficacy of the ophthalmic quinolone therapies currently available, there is a need for improved compositions and methods of treatment based on the use of antibiotics that are more effective than existing antibiotics against key ophthalmic pathogens and less prone to the development of resistance by those pathogens.
There is an even greater need for effective stable topical compositions and methods for treating otic and nasal infections, particularly bacterial infections. The use of oral antibiotics to treat otic infections in children has limited efficacy, and creates a serious risk of pathogen resistance to the orally administered antibiotics.
The present inventors while working on the pharmaceutical compositions of nadifloxacin or salts thereof have surprisingly found that nadifloxacin can be formulated into a stable solution dosage form that prevents coloration, reduces formation of impurities and avoids precipitation of active ingredient from solution dosage form throughout its shelf life. The stable solution is suitable for the treatment of ocular, otic and nasal infections. The present inventors have found that the low resistance of microbes to nadifloxacin, effectiveness in treating Methicillin-Resistant Staphylococcus Aureus (MRSA) infections and no cross-resistance with other quinolones makes nadifloxacin an ideal candidate for the treatment of bacterial infections of ophthalmic, otic and nasal origin. When compared with other known quinolone anti-bacterial drugs used in solution dosage forms for ophthalmic, otic or nasal use, nadifloxacin is effective in low dosages and is relatively well tolerable.
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Additionally, it was also found that nadifloxacin is the only acidic quinolone available in the market. Other known quinolones tend to lose their antibacterial activity in acidic conditions while nadifloxacin activity potentiates in acidic medium. Since ocular environment is near neutral or acidic; nadifloxacin offers excellent advantage over other quinolones. In some specific pathological conditions wherein ocular pH is lowered significantly, nadifloxacin exhibits excellent bactericidal activity whereas other known quinolones tend to be ineffective.
In one aspect of the invention there is provided a stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutical^ acceptable salt thereof at a concentration of 0.01% to 1% (w/v), wherein the solution does not show any precipitation during the entire period of shelf life.
In another aspect of the invention there is provided a stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutical^ acceptable thereof at a concentration of 0.01% to 1% (w/v), wherein the solution does not show any precipitation during the entire period of shelf life and the amount of total related substances after six months of storage at 25°C/60% RH or at 45°C/75%RH is 2.0 % (w/w) or less.
The term "nadifloxacin or pharmaceutically acceptable salts thereof" referred to in this invention means racemic nadifloxacin and its salts, its single enantiomer such as R-Nadifloxacin or S-nadifloxacin or salts thereof with organic or inorganic bases. (S)-Nadifloxacin salts with amino acids such as arginine salt is also contemplated in this invention.
Normally, the amount of nadifloxacin or its salt to be formulated in the solution pharmaceutical composition of the present invention varies according to the degree of infection of a particular subject, but normally, nadifloxacin is formulated
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within the range of 0.01 to 1.0% (w/v), preferably 0.1 to 0.8% (w/v), more preferably 0.2 to 0.5% (w/v).
Nadifloxacin solution dosage form is tested for stability using specified temperature and humidity ranges. Accelerated stability studies are performed by subjecting the samples at 40°C/75% Relative Humidity for 6 months. Total relative substances of the sample are tested; the different impurity values obtained indicated that there is no any precipitation and the formulation is stable at accelerated storage conditions.
In another aspect of the present invention there is provided a stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), arginine at a concentration of 0.1% to 4.0% (w/v), and pharmaceutically acceptable vehicle therefor.
Addition of 0.1% to 4.0% (w/v) of arginine provides increased solubility of nadifloxacin, lowered potential to induce phlebitogenicity and stability when stored for an extended period at specified temperature and humidity ranges.
In yet another aspect of the present invention there is provided a stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), a pharmaceutically effective amount of hydroxypropyl-P-cyclodextrin, and pharmaceutically acceptable vehicle therefor.
In yet another aspect of the present invention there is provided a stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), arginine at a concentration of 0.1% to 4.0% (w/v), a pharmaceutically effective
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amount of hydroxypropyl-b-cyclodextrin, and pharmaceutically acceptable vehicle therefor.
Hydroxypropyl- b-cyclodextrin acts as a solubility enhancer component, helps to stabilize the solution and further helps to enhance the penetration of the drug into the corneal tissue.
In another aspect of the present invention there is provided a stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), arginine at a concentration of 0.1% to 4.0% (w/v), a pharmaceutically effective amount of hydroxypropyl-b-cyclodextrin, a steroid, and pharmaceutically acceptable vehicle therefor.
For broader spectrum antibacterial activity, a second drug can be administered in co-therapy. In case of present embodiment, the second agent can be steroid. Formulations containing steroids are useful for topical application to the eye, ear, nose or skin. Steroids are insoluble in water and thus are generally available in suspended form or are dissolved in oil or solvents when used in the formulation. However, for ophthalmic use it would be desirable to avoid the use of oil or solvents and provide a clear solution of steroid in a predominantly aqueous phase and a formulation in suspension form causes discomfort to the eye and requires inclusion of many additional excipients to formulate a stable suspension composition, which may also cause irritation to the eye. Thus a clear, stable solution composition is the most preferred formulation for administration to the eye.
The suitable steroidal drug comprises one or more of beclomethasone, betamethasone, budesonide, dexamethasone, clobetasol, clobetasone, flumethasone, fluorometholone, hydrocortisone, prednisolone, triamcinolone loteprednol, methylprednisolone, medrysone and the like.
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In another aspect of the present invention there is provided a process for the preparation of a stable solution, the process comprising:
a) mixing water, nadifloxacin or a pharmaceutical^ acceptable salt thereof, arginine and hydroxypropyl- b-cyclodextrin;
b) filtering the solution; and
c) filling in suitable containers.
In yet another aspect of the present invention there is provided a process for the preparation of a stable solution, the process comprising:
d) mixing water, nadifloxacin or a pharmaceutically acceptable salt thereof, arginine, hydroxypropyl- (3-cyclodextrin and dexamethasone;
e) filtering the solution; and
f) filling in suitable containers.
The pharmaceutically acceptable vehicle may include water.
The composition may further include other pharmaceutically acceptable excipients. The other excipients may include one or more of preservatives, surfactants or co-solvents, viscosity enhancing agents, and the like.
The stable solution dosage form for the ophthalmic, otic or nasal use, as part of present invention can be present in a single use or multi-use container. The compositions are preferably sterile, and have physical properties (e.g., osmolality and pH) that are specially suited for application to ophthalmic, otic and nasal tissues, including tissues that have been compromised as the result of preexisting disease, trauma, surgery or other physical conditions.
The compositions are typically administered to the affected ophthalmic, otic or nasal tissues by topically applying one to four drops of a sterile solution, one to four times per day. However, the compositions may also be formulated as
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irrigating solutions that are applied to the affected ophthalmic, otic or nasal tissues during surgical procedures.
The ophthalmic, otic and nasal compositions of the present invention will typically have a pH in the range of 4.5 to 8.0. The ophthalmic compositions must also be formulated to have osmotic values that are compatible with the aqueous humor of the eye and ophthalmic tissues. Such osmotic values will generally be in the range of from about 200 to about 400 milliosmoles per kilogram of water ("mOsm/kg"), but will preferably be about 300 mOsm/kg.
Ophthalmic, otic and nasal pharmaceutical products are typically packaged in multidose form. Preservatives are thus required to prevent microbial contamination during use. Suitable preservatives include: polyquatemium-1, benzalkonium chloride, thimerosal, chlorobutanol, methyl paraben, propyl paraben, phenylethyl alcohol, edetate disodium, sorbic acid, or other agents known to those skilled in the art. Typically such preservatives are employed at a level of from 0.001% to 1.0% (w/v).
A surfactant or other appropriate co-solvent in the composition may enhance the solubility of the components of the present compositions. In case of nadifloxacin due to its poor water solubility use of co-solvents or complex forming agents helps in achieving the desired results. Such co-solvents include polysorbate 20, 60, and 80, polyoxyethylene/polyoxypropylene surfactants (e.g., Pluronic F-68, F-84 and P-103), and cyclodextrin especially HP- b -CD, or other agents known to those skilled in the art. Typically such co-solvents are employed at a level of from 0.01% to 5% (w/v). HP-b-CD has a tendency to form inclusion complex with many drugs including nadifloxacin. This complex offers several advantages, such as reduced irritation, increased tolerability and efficacy. The dose of nadifloxacin can be further reduced based on complexation with HP- b -CD.
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The use of viscosity enhancing agents to provide the compositions of the invention with viscosities greater than the viscosity of simple aqueous solutions is desirable to increase ocular absorption, and reduce irritability of the active compounds by the target tissues or increase the retention time in the eye, ear or nose. Such agents include, for example, polyvinyl alcohol, polyvinyl pyrrolidone, methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose or other agents know to those skilled in the art. Such agents are typically employed at a level of from 0.01% to 2% (w/v).
Nadifloxacin solution dosage form is tested for stability using accelerated stability tests as well as for initial time studies. Accelerated stability studies are performed by subjecting the samples at 40°C/75% Relative Humidity for 3 months and 6 months. The relative impurities (known and unknown) of the sample are tested by using HPLC analysis method. The different impurity values obtained indicated that the formulation is stable at accelerated storage conditions. The stability results are provided in Tables 2 and 3. The single highest known impurity is nothing but the known impurity having maximum value selected from all known impurity peak areas. The single highest unknown impurity is unknown impurity having maximum value selected from all unknown impurity peak areas. Sum of peak areas of single highest known impurity and single highest unknown impurity is represented as total.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
Example 1: The composition of batches is provided in Table 1. Following formulations are representatives of the preferred compositions of the present invention. The preparation of example 1 is detailed below.
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Table 1 provides composition of batches of the present invention

Sr.No Name of ingredient Example 1 (% Composition) Example 2 (% Composition)
1 S-Nadifloxacin 0.3 0.2
2 L-Arginine 0.66 0.44
3 Hydroxypropyl betacyclodextrin 2.50 2.0
4 Polyvinyl alcohol 0.3 0.30
5 Benzalkonium chloride 0.01 0.01
6 Disodium EDTA 0.05 0.05
7 Sodium Chloride 0.50 0.50
8 Water for injection q.s. 100 ml q.s 100 ml
9 Sodium Hydroxide or Hydrochloric acid q.s 1 N solution for pH adjustment to 7.0 q.s 1 N solution for pH adjustment to 7.0
Procedure -
Nadifloxacin, amino acid and HP-b- CD were dissolved in water for injection. To this was added a solution of polyvinyl alcohol and benzalkonium chloride in water for injection. A solution of disodium edetate was added to this and the pH of the resultant solution was adjusted using 1N HCI between 5.5 to 7.5. The solution was then adjusted to required osmolality using a solution of sodium chloride (0.1 to 0.9%) in water for injection. Osmolality of solution was adjusted to 250-350 mOsm/kg. The resultant solution was filtered using 0.22m membrane filters and filled in desired containers under laminar flow.
Example 2: The composition of batches is provided in Table 2.

Sr.No Name of ingredient Example 3 (% Composition)
1 S-Nadifloxacin 0.3
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2 Dexamethasone 0.1
3 L-Arginine 0.2
4 Hydroxypropyl betacyclodextrin 1.0
5 Polyvinyl alcohol 0.5
6 Benzalkonium chloride 0.01
7 Disodium EDTA 0.01
9 Water for injection q.s. 100 ml
10 Sodium Hydroxide or Hydrochloric acid q.s 1 N solution for pH adjustment to 5.5-7.5
Procedure -
Nadifloxacin, dexamethasone, amino acid and HP-b- CD were dissolved in water for injection. To this was added a solution of polyvinyl alcohol and benzalkonium chloride in water for injection. A solution of disodium edetate was added to this and the pH of the resultant solution was adjusted using 1N HCI between 5.5 to 7.5. Osmolality of the solution was adjusted to 250-350 mOsm/kg. The resultant solution was filtered using 0.22 m membrane filters and filled in desired containers under laminar flow.
Tables 3 and 4 provide the stability data for the nadifloxacin solution dosage form prepared as per the Formula given in Table 1.
Samples containing nadifloxacin solution dosage form are tested for stability using accelerated stability tests (subjecting the samples at 40°C/75% Relative Humidity for 3 months and 6 months) as well as "initial time" studies. The results are shown in Tables 3 and 4.
Table 3 - Stability data for example 1.

Parameters Initial 3 Months 6 Months
25°C/60%RH 40°C/75%RH 25°C/60%RH 40°C/75%RH
Assay of Nadifloxacin 102.67 100.19 102.80 103.72 100.42
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Nadifloxacin
RelatedSubstances-1. SingleHighestKnownimpurity 0.063 0.059 0.063 0.125 0.128
2. Single Highest Unknown impurity 0.139 0.136 0.119 0.258 0.281
3. Total RS 0.343 0.333 0.339 0.702 0.746
pH 7.01 6.95 6.94 6.74 6.63
Osmolality 300 - - - -
Table 4 - Stability data for example 2.

Parameters Initial 3 Months 6 Months
25°C/60%RH 40°C/75%RH 25°C/60%RH 40°C/75%RH
Assay of Nadifloxacin 102.58 101.49 101.96 98.78 99.31
RelatedSubstances-1. SingleHighestKnownimpurity 0.063 0.063 0.060 0.111 0.127
2. Single Highest 0.128 0.142 0.126 0.257 0.281
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Unknown impurity
3. Total RS 0.329 0.342 0.320 0.694 0.718
pH 6.82 6.96 6.79 6.80 6.62
Osmolality 300 - - - -
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
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We Claim:
1. A stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable salt thereof at a concentration of 0.01% to 1% (w/v), wherein the solution does not show any precipitation during the entire period of shelf life.
2. A stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), wherein the solution does not show any precipitation during the entire period of shelf life and the amount of total related substances after six months of storage at 25°C/60%RH or at 45°C/75%RH is 2.0 % (w/w) or less.
3. A stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), arginine at a concentration of 0.1% to 4.0% (w/v), and pharmaceutically acceptable vehicle therefor.
4. A stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), a pharmaceutically effective amount of hydroxypropyl-b-cyclodextrin, and pharmaceutically acceptable vehicle therefor.
5. A stable solution suitable for ophthalmic, otic or nasal administration
comprising nadifloxacin or a pharmaceutically acceptable thereof at a
concentration of 0.01% to 1% (w/v), arginine at a concentration of
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0.1% to 4.0% (w/v), a pharmaceutically effective amount of hydroxypropyl-b-cyclodextrin and pharmaceutically acceptable vehicle therefor.
6. A stable solution suitable for ophthalmic, otic or nasal administration comprising nadifloxacin or a pharmaceutically acceptable thereof at a concentration of 0.01% to 1% (w/v), arginine at a concentration of 0.1% to 4.0% (w/v), a pharmaceutically effective amount of hydroxypropyl-b-cyclodextrin, a steroid, and pharmaceutically acceptable vehicle therefor.
7. A process for the preparation of a stable solution, the process comprising:

a) mixing water, nadifloxacin or a pharmaceutically acceptable salt thereof, arginine and hydroxypropyl-b-cyclodextrin;
b) filtering the solution; and
c) filling in suitable containers.
8. A process for the preparation of a stable solution, the process
comprising:
a) mixing water, nadifloxacin or a pharmaceutically acceptable salt thereof, arginine, hydroxypropyl-P-cyclodextrin and dexamethasone;
b) filtering the solution; and
c) filling in suitable containers.
9. The stable solution according to claims 1 to 6, wherein pH of the
solution is within the range 4.5 to 8.0.
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10. The stable solution according to claims 1 to 6 further comprises one or more other pharmaceutically acceptable excipients.
Dated this ™ day of August 2007.

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Abstract
The present invention relates to stable solutions suitable for ophthalmic, otic, or nasal administration that include nadifloxacin and pharmaceutically acceptable salts thereof. The invention also relates to processes for the preparation of the stable solutions.
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