Topical suspension formulations containing ciprofloxacin and dexamethasone

<td>REPUBLIC POLAND</td><td>(12) PATENT DESCRIPTION (19) PL (21) Application number: 359623</td><td>(11) 201 130 (13) B1</td>

<td></td><td>(22) Date of notification: 10/08/2000</td><td>(51) Int.Cl. A61K 9/10 (2006.01)</td>

<td></td><td>(86) Date and number of the international application:</td><td>A61K 31/57 (2006.01)</td>

<td></td><td>2000-08-10, PCT / US00 / 21961</td><td>A61K 31/497 (2006.01)</td>

<td>patent Office</td><td>(87) Date and publication number of the international application:</td><td></td>

<td>Polish Republic</td><td>2001-04-05, WO01 / 22936 PCT Gazette No. 14/01</td><td></td>

<td colspan="2">₍₅₄₎ Suspension compositions containing ciprofloxacin⁽⁵⁴⁾ and dexamethasone for topical administration to the eyes, ears, or nose</td>

<td rowspan="2">(30) Priority: 1999-09-24, US, 60 / 155,942</td><td>(73) The right holder of the patent:</td>

<td>ALCON INC. ^ Nenberg, CH</td>

<td>(43) Application announced: 23.08.2004 BUP 17/04</td><td>(72) Inventor (s): Onkar N. Singh, Arlington, US Haresh G. Bhagat, Fort Worth, US</td>

<td>(45) The grant of the patent was announced:</td><td rowspan="2">(74) Representative: Jolanta Mitura, PATPOL Sp. z o. o</td>

<td>March 31, 2009 WUP 03/09</td>

⁽⁵⁷⁾ A suspension composition for topical administration to the eyes, ears or nose, characterized in that it comprises

a) 0.01-0.5% (w / w) dexamethasone;

b) 0.1-0.4% (w / w) ciprofloxacin;

c) a tonicity adjuster consisting essentially of NaCl in an amount sufficient for the osmolality of the composition to be about 250-350 mOsm;

d) 0.1-0.5% (w / w) of a non-ionic polymer;

e) 0.01-0.2% (w / w) of a nonionic surfactant; and

f) buffer, wherein the composition has a pH of 4.5 0.2.

PL 201 130 B1

Description of the invention

The present invention relates to ciprofloxacin and dexamethasone compositions intended for topical administration to the eyes, ears or nose.

The compositions of the present invention are suspensions that have excellent physical stability and are readily re-suspended. In particular, the invention relates to stable ciprofloxacin and dexamethasone suspension formulations devoid of a non-ionic tonicity adjusting agent such as glycerol or mannitol.

Spanish Patent Application No. 2,065,846 A1 (February 16, 1995) discloses topically administrable ophthalmic and ear products which are a combination of an antibiotic and a steroid. Examples 1-3 illustrate ophthalmic suspension formulations containing the combination of specific drugs with excipients including non-ionic polymers and non-ionic surfactants. Example 1 describes a formulation of clobetasone and lomefloxacin that contains a non-ionic tonicity adjusting agent (glycerin). Example 2 describes a formulation of fluorometholone and norfloxacin that contains an ionic tonicity adjuster (sodium chloride). Example 3 describes a formulation of ciprofloxacin and dexamethasone that contains a non-ionic tonicity adjusting agent (mannitol).

U.S. Patent Nos. 5,540,930 and 5,747,061 disclose steroidal suspension formulations for topical administration that contain a non-ionic polymer, a non-ionic surfactant, and a non-ionic tonicity adjuster. These patents relate to "stable suspensions of water-insoluble steroid drugs with a particle size &lt;15 µm that remain in such a state as to permit immediate suspension, if desired, even after periods of chronic sedimentation" (see abstract 5,747,061). These patents are based on the statement that "surprisingly, conventional tonicity adjusting agents such as an aqueous solution containing 0.9% NaCl, 0.1% EDTA, or a phosphate buffer, even at concentrations as low as 1 mM, cannot be used. to obtain stable aqueous corticosteroid suspensions such as [loteprednol etabonate (LE)] ”(Patent 5,747,061, col. 2, lines 52-56).

Patent 5,747,061 relates to formulations that solved the need for "aqueous suspensions of corticosteroids such as LE that can be obtained without agglomeration" (col. 2 lines 57-59). The formulations of the patent 5,747,061 include (A) a "soft" steroid such as LE present in particulate form preferably having a mean diameter value less than about 15 microns, (B) a non-ionic polymer as a suspending agent, (C) a non-ionic surfactant, and (D ) a non-ionic tonicity adjuster. Patent 5,747,061 defines a "soft" drug as a biologically active chemical component with predictable in vivo metabolism to non-toxic derivatives once a therapeutic effect is achieved. Patent 5,747,061 teaches that "it is imperative that these components (A) - (D) be as non-ionic as possible, since the presence of ions has now been found to be a major cause of caking" (col. 3, lines 51- 53). As the preferred tonicity adjusting agents (see col. 3 lines 53-56), mention is made of nonionic diols such as glycerin or mannitol "and not the commonly used sodium chloride". The nonionic tonicity adjuster is preferably present in an amount of about 0.5 to 10% by weight.

The compositions of the present invention are non-agglomerating aqueous suspension formulations of corticosteroids (dexamethasone). In addition to corticosteroids, these preparations contain an antibiotic (ciprofloxacin) as a second active ingredient. The compositions of the present invention contain an ionic tonicity adjusting agent, but are nevertheless stable enough to be immediately and readily resuspended if necessary.

The compositions of the present invention contain a corticosteroid and an antibiotic. The corticosteroid is dexamethasone and the antibiotic is ciprofloxacin. Dexamethasone can be present in any ophthalmically and ENT acceptable form having poor water solubility such that the final formulation is a suspension formulation. Suitable forms of dexamethasone include dexamethasone alcohol and dexamethasone acetate. A preferred form is dexamethasone-alcohol. Ciprofloxacin may be present in any ophthalmically and ENT acceptable form such that this component is in solution in the final formulation. A preferred form of ciprofloxacin is ciprofloxacin hydrochloride monohydrate.

The compositions of the present invention contain about 0.01-0.5% dexamethasone and about 0.1-0.4% ciprofloxacin. The preferred amounts of dexamethasone and ciprofloxacin in the compositions of the present invention are 0.1% and 0.3%, respectively.

PL 201 130 B1

In addition to the active ingredients, the compositions of the present invention contain sodium chloride as an ionic tonicity adjuster. The amount of NaCl depends on the desired tonicity of the final formulation, but is usually in the range of 0.1-0.9%. For ocular and ear applications, the suspension compositions of the present invention preferably contain sufficient NaCl to provide formulations with an osmolality of about 250-350 mOsm.

The suspension compositions also include a non-ionic polymer. There are many known non-ionic polymers acceptable in ophthalmology and ENT. These polymers include hydroxyethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone and polyvinyl alcohol. A preferred nonionic polymer is hydroxyethyl cellulose. The nonionic polymer is present in the compositions of the present invention in an amount of about 0.1-0.5%. In the case of hydroxyethyl cellulose, the preferred concentration of the non-ionic polymer is 0.2%.

The compositions of the present invention also contain a nonionic surfactant in an amount of about 0.01-0.2%. Many ophthalmically and ENT-acceptable nonionic surfactants are known. Suitable nonionic surfactants include tyloxapol, polyoxyethylene sorbitan esters such as polysorbate 20, polysorbate 60 and polysorbate 80, polyethoxylated castor oils such as Cremaphor E, polyoxyethylene hydrogenated castor oils such as HCO-40 and poloxamers. The usual surfactant is tyloxapol.

The compositions of the present invention have a pH in the range of 3-5, preferably 4.5. The pH can be adjusted with NaOH / HCl. A preferred buffering system for the compositions of the invention is a combination of sodium acetate and acetic acid. The sodium acetate concentration is generally in the range of 0.015-0.06%, and is preferably about 0.03%. The acetic acid concentration is preferably in the range of 0.02-0.08%, preferably about 0.04%.

Unless otherwise indicated, the amounts of all ingredients as percentages are% by weight.

Thus, the suspension composition according to the invention intended for topical administration to the eyes, ears or nose, is characterized in that it comprises:

a) 0.01-0.5% (w / w) dexamethasone;

b) 0.1-0.4% (w / w) ciprofloxacin;

c) a tonicity adjuster consisting essentially of NaCl in an amount sufficient to produce an osmolality of the composition to be about 250-350 mOsm;

d) 0.1-0.5% (w / w) of a non-ionic polymer;

e) 0.01-0.2% (w / w) of a nonionic surfactant; and

f) buffer, wherein the composition has a pH of 4.5 0.2.

Preferably, the composition comprises, as the nonionic surfactant, hydroxyethylcellulose which is present at a concentration of 0.2% (w / w), and as the nonionic surfactant, tyloxapol, which is present at a concentration of 0.05% (w / w).

If desired, the compositions of the invention may contain a quaternary ammonium halide preservative. Suitable quaternary ammonium halides include polyquaternium-1 and benzalkonium halides. Preferably the benzalkonium halides are benzalkonium chloride ("BAC") and benzalkonium bromide. Mostly, the amount of the preservative is in the range 0.005 0.3%. In the preferred case where the preservative is BAC, it is present in a concentration of 0.01%.

If desired, a chelating agent may also be present in the suspension compositions of the present invention. Suitable chelating agents include disodium edetate ("EDTA"); trisodium edetate; tetrasodium edetate; and diethyleneamine pentaacetate. EDTA is most preferred. The amount of chelating agent, if present, is typically in the range of about 0.001-0.1%. In the case of EDTA, the chelating agent is preferably present at a concentration of 0.01%.

In the case of preserved multi-dose formulations, the suspension compositions of the present invention may contain boric acid in an amount of 0.1-1.5%.

In one preferred embodiment, the composition according to the invention further comprises 0.005-0.3% (w / w) of a quaternary ammonium halide; 0.001-0.1% (w / w) of a chelating agent; and 0.1 - 1.5% (w / w) boric acid.

In a specific embodiment, the suspension composition according to the invention consists essentially of:

a) 0.1% (w / w) of dexamethasone-alcohol;

b) 0.35% (w / w) of ciprofloxacin hydrochloride monohydrate;

c) NaCl in an amount sufficient to make the composition osmolality about 250-350 mOsm;

PL 201 130 B1

d) 0.2% (w / w) of hydroxyethyl cellulose;

e) 0.05% (w / w) of tyloxapol;

f) a buffer containing sodium acetate and acetic acid;

g) 0.01% (w / w) benzalkonium chloride;

h) 0.01% (w / w) of disodium edetate;

i) 0.6% (w / w) of boric acid;

wherein the composition has a pH of 4.5 0.2.

The mean particle size ("mean volume basis") of the dexamethasone in the compositions of the invention should be less than 10 µm to avoid irritation and discomfort. The average particle size is preferably less than 6 µm and more preferably less than 3 µm. The appropriate size of the dexamethasone particles can be obtained using known techniques such as grinding in a ball mill, microfluidization, sonication.

The following examples are intended to illustrate the present invention in a non-limiting manner.

Example 1

Table 1

<td rowspan="2">Ingredients</td><td colspan="5">PREPARATION</td>

<td>AND wt.%</td><td>B wt.%</td><td>C. wt.%</td><td>D wt.%</td><td>E. wt.%</td>

<td>Ciprofloxacin HCl, monohydrate</td><td> 0,35</td><td> 0,35</td><td> 0,35</td><td> 0,35</td><td> 0,35</td>

<td>Dexamethasone - alcohol</td><td> 0,1</td><td> 0,1</td><td> 0,1</td><td> 0,1</td><td> 0,1</td>

<td>Hydroxyethyl cellulose</td><td> 0,2</td><td> 0,2</td><td> 0,2</td><td> 0,2</td><td> 0,2</td>

<td>Benzalkonium chloride</td><td> 0,01</td><td> 0,01</td><td> 0,01</td><td> 0,01</td><td> 0,01</td>

<td>Sodium acetate (trihydrate)</td><td> 0,03</td><td> 0,03</td><td> 0,03</td><td> 0,03</td><td> 0,03</td>

<td>Acetic acid</td><td> 0,04</td><td> 0,04</td><td> 0,04</td><td> 0,04</td><td> 0,04</td>

<td>Sodium chloride</td><td> 0,25</td><td> 0,25</td><td> 0,8</td><td> 0,53</td><td> -</td>

<td>Disodium edetate</td><td> 0,01</td><td> 0,01</td><td> 0,01</td><td> 0,01</td><td> 0,01</td>

<td>Tyloxapol</td><td> 0,05</td><td> 0,05</td><td> 0,05</td><td> 0,05</td><td> 0,05</td>

<td>Glycerine</td><td> 1,5</td><td> -</td><td> -</td><td> -</td><td> 2,35</td>

<td>Boric acid</td><td> -</td><td> -</td><td> -</td><td> 0,6</td><td> -</td>

<td rowspan="2">NaOH / HCI</td><td>qspH</td><td>gspH</td><td>qspH</td><td>qspH</td><td>qspH</td>

<td> 4,5±0,2</td><td> 4,5±0,2</td><td> 4,5±0,2</td><td> 4,5±0,2</td><td> 4,5±0,2</td>

<td>Purified Water</td><td>qs 100</td><td>qs 100</td><td>qs 100</td><td>qs 100</td><td>qs 100</td>

<td>Osmolality (mOsm)</td><td> 272</td><td> 99</td><td> 274</td><td> 286</td><td> 290</td>

* Corresponds to 0.3% of ciprofloxacin base

AE formulations were prepared as follows:

(1) To obtain a 500 ml portion of the formulation, in a grinding drum containing 30 ml polypropylene, a suspension is prepared by combining 75 g of 3 mm zirconium beads, 12 g of 1.0% tyloxapol stock and 0.5 g of dexamethasone in the alcohol form (approximately 48% of the required final tyloxapol portion is used);

(2) the suspension containing the beads is steam sterilized (autoclave);

(3) the sterilized suspension is milled in an aseptic ball mill for 18 hours at 50 to 55 rpm;

(4) an aqueous solution is prepared containing the remaining required amount of tyloxapol and the required amounts of all other components (e.g. for formulation D, the remaining components are ciprofloxacin hydrochloride monohydrate, benzalkonium chloride, sodium acetate, acetic acid, sodium chloride, hydroxyethylcellulose, boric acid, disodium edetate and purified water;

(5) the aqueous solution prepared in step 4 is steam sterilized (autoclave);

(6) the sterile suspension obtained in Step 3 is combined with the sterile solution obtained in Step 5 by aseptically pouring the suspension into the solution obtained in Step 5 through a sterile screen (to remove beads);

(7) the weight of the formulation is adjusted to 80-90% of the batch weight using purified, filter-sterilized water;

(8) check the final pH and, if necessary, adjust it to 4.5 ± 0.2 with filter-sterilized sodium hydroxide or hydrochloric acid; and (9) adjusting the weight of the formulation to 100% of the batch weight using filter sterilized purified water.

An alternative method of preparing formulations A-E, especially when crude dexamethasone is supplied or available in a form meeting the particle size requirements, is as follows:

(1) raw dexamethasone is sterilized with dry hot air (recommended technical requirements: 7 - 11 hours at 130 - 140 ° C (internal powder temperature));

(2) preparing a solution of tyloxapol in purified water containing the required aliquot of tyloxapol;

(3) sterilize the tyloxapol solution by passing it through a 0.2 µm filter;

(4) the sterile dexamethasone and the sterile tyloxapol solution are aseptically combined to form a sterile suspension and mixed until uniform;

(5) an aqueous solution is prepared containing the desired amounts of the remaining ingredients (e.g., for formulation D, the other ingredients are ciprofloxacin hydrochloride, benzalkonium chloride monohydrate, sodium acetate, acetic acid, sodium chloride, hydroxyethyl cellulose, boric acid, disodium edetate, and purified water;

(6) the aqueous solution prepared in step (5) is steam sterilized (autoclave);

(7) the sterile suspension prepared in step (4) is combined aseptically with the sterile solution prepared in step (6);

(8) the weight of the formulation is adjusted to 80-90% of the batch weight using sterilized purified water;

(9) check the final pH and, if necessary, adjust it to 4.5 ± 0.2 with filter-sterilized sodium hydroxide or hydrochloric acid; and (10) the weight of the formulation is adjusted to 100% of the batch weight by using filter sterilized purified water.

Example 2

Formulations A - E were tested for their recovery time in "accelerated" and "real-time" sedimentation studies.

Accelerated sedimentation tests were carried out by subjecting 5 g of each preparation to centrifugation in separate, flat-bottomed glass tubes with dimensions of 16 x 125 mm for 30 minutes at 3100 rpm using an IEC CENTRA-7 centrifuge. The reconstitution of the suspended material from the deposited material was tested by measuring the number of seconds of hand shaking required to completely reconstitute the suspension.

Real-time sedimentation studies were carried out by placing 5 g of each formulation in 16 x 125 mm flat bottom glass tubes and allowing 7 days (except for formulation B, which was left for four days) for natural sedimentation (under gravity. Reproducibility. the deposited material suspensions were tested by measuring the number of inversions necessary to completely re-suspend the pellet. Table 2 shows the results of the suspension reproducibility study for the tested formulations.

Table 2

<td rowspan="2">Preparation</td><td>Accelerated sedimentation</td><td>Real-time sedimentation</td>

<td>Suspension reconstitution time (seconds)</td><td>Number of inversions to completely reconstitute the suspension</td>

<td> 1</td><td> 2</td><td> 3</td>

<td></td><td> 11</td><td> 17</td>

<td>AND</td><td> 12</td><td> 16</td>

<td></td><td> 11</td><td> 19</td>

<td rowspan="2">B *</td><td> 6</td><td> 16</td>

<td> 7</td><td> 16</td>

PL 201 130 B1 cont. table 2

<td> 1</td><td> 2</td><td> 3</td>

<td></td><td> 13</td><td> 12</td>

<td>C.</td><td> 16</td><td> 13</td>

<td></td><td> 19</td><td> 11</td>

<td></td><td> 7</td><td> 12</td>

<td>D</td><td> 9</td><td> 13</td>

<td></td><td> 6</td><td> 11</td>

<td></td><td> &gt;60</td><td> 18</td>

<td>E.</td><td> &gt;60</td><td> 26</td>

<td></td><td> &gt;60</td><td> 19</td>

* Formulation B tested after 4 days standing; remaining after 7 days.

Example 3

Preservation Efficiency Test (PET)

The antimicrobial preservation performance of the polymeric quaternary ammonium compound / boric acid combination of the present invention was determined using an organism challenge test according to the methods described in the US Pharmacopoeia (USP) and European Pharmacopoeia (Ph.Eur.). Test samples were inoculated with known levels of vegetative Gram-positive bacteria (Staphylococcus aureus ATCC 6538) and Gram-negative bacteria (Pseudomonas aeruginosa ATCC 9027 and Escherichia coli ATCC 8739), yeast (Candida albicans ATCC 10231) and mold (Aspergillus niger then ATCC 16404). test samples at specified intervals to determine if the preservative system was capable of killing or inhibiting the growth of the organisms intentionally introduced into the formulation. The factor or level of antimicrobial activity was determined according to USP and / or Ph.Eur Preservation Efficiency Standards. for eye preparations.

The requirements according to the standards of preservation for eye preparations are presented below:

For bacteria:

(Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli)

Organism population reduction log

<td>The time interval</td><td>USP</td><td>Ph.Eur.A (target)</td><td>Ph.Eur.B (Min)</td>

<td>6 hours</td><td> -</td><td> 2</td><td> -</td>

<td>24 hours</td><td> -</td><td> 3</td><td> 1</td>

<td>7 days</td><td> -</td><td> -</td><td> 3</td>

<td>14 days</td><td> 3</td><td> -</td><td> -</td>

<td>28 days</td><td>* NI</td><td>** NO</td><td>NI</td>

For mushrooms:

(Candida albicans, Aspergillus niger)

<td>The time interval</td><td>USP</td><td>Ph.Eur.A (target)</td><td>Ph.Eur.B (Min)</td>

<td>7 days</td><td> -</td><td> 2</td><td> -</td>

<td>14 days</td><td>NI</td><td> -</td><td> 1</td>

<td>28 days</td><td>NI</td><td>NI</td><td>NI</td>

* NI = No growth at this or next time frame ** NR = No recovery

- = no requirements for this time frame

The results of the preservation challenge tests conducted on the formulations of Examples 1-4 are shown in Table 3. These examples illustrate that, if desired, the suspension composition of the present invention can be preserved to meet the minimum preservation requirements of the United States Pharmacopoeia (USP). ) and the European Pharmacopoeia (Ph.Eur.) for eye and ear preparations.

PL 201 130 B1

Table 3

<td rowspan="2">Test organism</td><td colspan="5">PREPARATION</td>

<td>Time</td><td>AND</td><td>B</td><td>C.</td><td>D</td>

<td rowspan="6">S. Aureus</td><td>Initial</td><td> 6,0</td><td> 6,1</td><td> 6,1</td><td> 5,9</td>

<td>6 hours</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 4,9</td>

<td>24 hours</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 4,9</td>

<td>7 days</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 4,9</td>

<td>14 days</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 4,9</td>

<td>28 days</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 4,9</td>

<td rowspan="6">P. Aeruginosa</td><td>Initial</td><td> 6,0</td><td> 6,0</td><td> 6,0</td><td> 6,0</td>

<td>6 hours</td><td> 5,0</td><td> 5,0</td><td> 5,0</td><td> 5,0</td>

<td>24 hours</td><td> 5,0</td><td> 5,0</td><td> 4,7</td><td> 5,0</td>

<td>7 days</td><td> 5,0</td><td> 5,0</td><td> 5,0</td><td> 5,0</td>

<td>14 days</td><td> 5,0</td><td> 5,0</td><td> 5,0</td><td> 5,0</td>

<td>28 days</td><td> 5,0</td><td> 5,0</td><td> 5,0</td><td> 5,0</td>

<td rowspan="6">E. coli</td><td>Initial</td><td> 6,0</td><td> 6,0</td><td> 6,0</td><td> 5,9</td>

<td>6 hours</td><td> 4,0</td><td> 4,0</td><td> 4,0</td><td> 3,9</td>

<td>24 hours</td><td> 4,0</td><td> 4,0</td><td> 4,0</td><td> 3,9</td>

<td>7 days</td><td> 4,0</td><td> 4,0</td><td> 4,0</td><td> 3,9</td>

<td>14 days</td><td> 4,0</td><td> 4,0</td><td> 4,0</td><td> 3,9</td>

<td>28 days</td><td> 4,0</td><td> 4,0</td><td> 4,0</td><td> 3,9</td>

<td rowspan="4">C. Albicans</td><td>Initial</td><td> 6,0</td><td> 6,1</td><td> 6,1</td><td> 6,1</td>

<td>7 days</td><td> 5,0</td><td> 5,1</td><td> 4,7</td><td> 5,1</td>

<td>14 days</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 5,1</td>

<td>28 days</td><td> 5,0</td><td> 5,1</td><td> 5,1</td><td> 5,1</td>

<td rowspan="4">A. Niger</td><td>Initial</td><td> 6,1</td><td> 5,9</td><td> 5,9</td><td> 6,1</td>

<td>7 days</td><td> 1,8</td><td> 0,9</td><td> 0,9</td><td> 1,8</td>

<td>14 days</td><td> 2,0</td><td> 0,8</td><td> 1,0</td><td> 1,9</td>

<td>28 days</td><td> 2,5</td><td> 1,5</td><td> 1,5</td><td> 4,3</td>

<td colspan="2">Meeting PET requirements</td><td>USP Ph.Eur.B</td><td>only USP</td><td>USP Ph.Eur.B</td><td>USP Ph.Eur.B</td>

Each of the formulations listed in Table 3 met the preservation criteria of Ph. Eur. And with regard to bacteria and Candida albicans, but preparations containing no boric acid showed difficulties meeting the Ph. Conservation criteria. Eur. B for Aspergillus niger.

The combination of boric acid and benzalkonium chloride improved the preservative activity with respect to Aspergillus niger and the formulation easily met Ph. Eur. B. Formulation B (boric acid free) only met USP criteria and failed to meet Ph. Minimum maintenance requirements. Eur. Preparation C (without boric acid) met the requirements of USP and Ph. Eur. B (minimum). Formulation A initially met the requirements of Ph. Eur. B, but showed reduced activity against Aspergillus niger when retested after 52 weeks. The baseline and 52 week results for Formulation A are shown in Table 4.

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Table 4

<td>Test organism</td><td>Time</td><td>Initially</td><td>52 weeks</td>

<td rowspan="6">S. Aureus</td><td>Initial</td><td> 6,0</td><td> 6,0</td>

<td>6 hours</td><td> 5,0</td><td> 5,0</td>

<td>24 hours</td><td> 5,0</td><td> 5,0</td>

<td>7 days</td><td> 5,0</td><td> 5,0</td>

<td>14 days</td><td> 5,0</td><td> 5,0</td>

<td>28 days</td><td> 5,0</td><td> 5,0</td>

<td rowspan="6">P. Aeruginosa</td><td>Initial</td><td> 6,0</td><td> 6,1</td>

<td>6 hours</td><td> 5,0</td><td> 5,0</td>

<td>24 hours</td><td> 5,0</td><td> 5,0</td>

<td>7 days</td><td> 5,0</td><td> 5,0</td>

<td>14 days</td><td> 5,0</td><td> 5,0</td>

<td>28 days</td><td> 5,0</td><td> 5,0</td>

<td rowspan="6">E. Coli</td><td>Initial</td><td> 6,0</td><td> 6,0</td>

<td>6 hours</td><td> 4,0</td><td> 4,0</td>

<td>24 hours</td><td> 4,0</td><td> 4,0</td>

<td>7 days</td><td> 4,0</td><td> 4,0</td>

<td>14 days</td><td> 4,0</td><td> 4,0</td>

<td>28 days</td><td> 4,0</td><td> 4,0</td>

<td rowspan="4">C. Albicans</td><td>Initial</td><td> 6,0</td><td> 6,0</td>

<td>7 days</td><td> 5,0</td><td> 5,0</td>

<td>14 days</td><td> 5,0</td><td> 5,0</td>

<td>28 days</td><td> 5,0</td><td> 5,0</td>

<td rowspan="4">A. Niger</td><td>Initial</td><td> 6,1</td><td> 6,2</td>

<td>7 days</td><td> 1,8</td><td> 1,0</td>

<td>14 days</td><td> 2,0</td><td> 1,2</td>

<td>28 days</td><td> 2,5</td><td> 1,7</td>

The invention has been described by reference to certain preferred embodiments, although it is understood that the invention may have other specific forms or embodiments not departing from the spirit or essential features of the invention. Therefore, the embodiments of the invention described above illustrate in all respects and without limitation the scope of the invention, which is defined by the appended claims and not by the above patent specification.