AU2012206996A1 - Methods for stabilizing ophthalmic compositions - Google Patents

Abstract

The present invention relates to a method comprising stabilizing, during autoclaving, an oxidatively unstable ophthalmic compound dissolved in an ophthalmic solution by incorporating a stabilizing effective amount of at least one electron rich polymer in said ophthalmic solution.

Description

AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION INVENTION TITLE: METHODS FOR STABILIZING OPHTHALMIC COMPOSITIONS The following statement is a full description of this invention, including the best method of performing it known to us:- -2 METHODS FOR STABILIZING OPHTHALMIC COMPOSITIONS FIELD OF THE INVENTION The present invention relates to methods for stabilizing ophthalmic against oxidative degradation, during processing, autoclaving, packaging, shipping or storage. This application is a divisional of application no. 2006225171, the disclosures of which are deemed to be incorporated herein. BACKGROUND OF THE INVENTION Therapeutic agents for topical administration to the eye are generally formulated in either a liquid or gel form and must be kept sterile until administration. Accordingly, ophthalmic therapeutic agents are either packaged asceptically, which is cumbersome and expensive or are heat sterilized. Unfortunately, many therapeutic agents are not oxidatively stable, especially at elevated temperatures. EDTA has been used to improve the stability of certain therapeutic agents during autoclaving. However, there remains a need lbr other compounds capable of stabilizing unstable therapeutic agents that are susceptible to catalytic oxidative degradation. SUMMARY OF THE INVENTION The present invention relates to a. method comprising stabilizing, during autoclaving, an oxidatively unstable ophthalmic compound dissolved in an ophthalmic solution by incorporating a stabilizing effective amount of at least one electron rich polymer in said ophthalmic solution. In an embodiment of the invention there is provided a method for stabilizing against oxidative degradation, during autoclaving, an oxidatively unstable ophthalmic compound, which shows greater than 10% degradation when autoclaved in solution with at least one oxidative catalyst, but shows less than 10% degradation when autoclaved under the same conditions without said at least one oxidative catalyst, dissolved in an ophthalmic solution by incorporating a -3 stabilizing effective amount of polyvinyl pyrrolidone in said ophthalmic solution, wherein said oxidatively unstable ophthalmic compound is selected from the group consisting of ketotefin fumarate, I I-dihydro- 1] -(1 -methyl-4 piperidinylidene)-5H-imidazo[2,1-b][13]benzazepinc-3-carboxaldehyde, and mixtures thereof wherein said polyvinyl pyrrolidone has a weight averaged molecular weight between 1000 and 2,000,000 and is substantially free from transition metal containing species In an embodiment of the invention there is provided an autoclavable solution comprising an ophthalmic solution comprising at least one oxidatively unstable ophthalmic compound, which shows greater than 10% degradation when autoclaved in solution with at least one oxidative catalyst, but shows less than 10% degradation when autoclaved under the same conditions without said at least one oxidative catalyst, and a stabilizing effective amount of polyvinyl pyrrolidone wherein said oxidatively unstable ophthalmic compound is selected from the group consisting of ketotefrin fumarate, I I-dihydro-I -(1-methyl-4 piperidinylidene)-5H- imidazo[2,1-b][ 3 ]benzazepine-3-carboxaldehyde, and mixtures thereof wherein said polyvinyl pyrrolidone has a weight averaged molecular weight between 1000 and 2,000,000 and is substantially free from transition metal containing species DETAILED DESCRIPTION OF THE INVENTION The present invention comprises, consists of and consists essentially of stabilizing, during autoclaving, at least one oxidatively unstable ophthalmic compound dissolved in an ophthalmic solution by incorporating a stabilizing effective amount of at least one electron rich polymer in said ophthalmic solution.

-4 As used herein, oxidatively unstable ophthalmic compound ("OUOC") is any therapeutic agent which shows greater than 10% degradation when autoclaved in solution with at least one oxidative catalyst, but shows less than 10% degradation when autoclaved under the same conditions without said at least one oxidative catalyst. Oxidative instability may be measured by forming a solution of 3 ml packing solution containing 25 ppm of the therapeutic agent to be evaluated, and exposing the solution, with and without oxidative catalysts (100 ppm Cu 2 O and 100 ppm FeSO4) to autoclave conditions (I 20*C for 20 minutes). Examples of OUOC include oxidatively unstable pharmaceutical and nutraceutical compounds. In one embodiment the OUOC comprises at least one pharmaceutically active amine. In one embodiment the OUOC comprises at least one tertiary cyclic amine. In another embodiment the OUOC comprises at least one tertiary cyclohexyl amine. In another embodiment the OUOC comprises at least one therapeutic agent selected from acycylovir, adrenalone, aminocaproic acid, amoxicillin, amotriphene, amoxecaine, amodiaquin, antazoline, atrophine, betaxolol, bupivacaine, carbachol, carteolol, chlorampenicol, eblortetracycline, corynathine. cromalyn sodium, cyclopentolate, demecarium, dexamethasone, dichlorphenamide, dibutoline, diclophenac, dipivefrin, ephedrine, erythromycin, ethambutol, eucatropine, fluoromethalone, gentamycin, gramicidin, homatropine, indomethacin, ketotifen, levallorphan, levobunolol, levocabastine, lidocaine, lignocaine, lonefloxacin, medrysone, mepivacaine, methazolamide, naphazoline, natamycin, natamycin, neomycin, noradrenaline, ofloxacin, oxybuprocaine, oxymetazoline, pheniramine, phenylephrine, physostigmine, pilocarpine, polymyxin B, prednisolone, proparacaine, pyrilamine, scopolamine, sorbinil, sulfacetamide, tamoxifen, tetracaine, tetracycline, tetrahydozoline, timolol, trifluridine, tropicamide, vidarabine, and salts and mixtures thereof Examples of nutriceutical compounds include vitamins and supplements such as vitamins A, D, E, lutein, zeaxanthin, lipoic acid, flavonoids, ophthalmicially compatible fatty acids, such as omega 3 and omega 6 fatty acids, combinations thereof, combinations with pharmaceutical compounds and the like. In yet another embodiment the OUOC comprises at least one therapeutic agent selected from ketotifen fumarate, nor ketotifen fumarate, 11 -dihydro-l l-(lmethyl-4-piperidinylidene)-SHU-imidazo[2,1 -b][3lbenzazepine-3-carboxaldehyde (CAS# 147084-10-4), olapatadine and mixtures thereof. In yet another embodiment the OUOC comprises at least one therapeutic agent selected from ketotifen fumarate, Ii-dihydro- 11 -(1 -nethyl-4-piperidinylidene)-5H-imidazo[2,I-b][ 3]benzazepine-3 carboxaldehyde (CAS# 147084-10-4) and mixtures thereof. The concentration of the OUOC in the oxidatively stable ophthalmic compositions of the present invention may range from about 10 ppm to about 100,000 ppm, in some embodiments from about 10 to about 10,000 ppm, in some embodiments fi.om about 10 to about 1,000 ppm and some embodiments from about 10 to about 500 ppm. The oxidatively stable ophthalmic compositions of the present invention further comprise at least one electron rich polymer. Suitable electron rich polymers are water-soluble, comprise at least one group with a free electron pair, have a weight average molecular weight, Mw, greater than about 1,000 and in some embodiments between about 1000 and about 2,000,000, and are substantially free from transition metal containing species. As used herein, water soluble means that the selected electron rich polymer does not precipitate or form visible gel particles at the concentrations selected and across the temperatures and p-I regimes common for manufacturing, sterilizing and storing ophthalmic solutions. In some embodiments the electron rich polymer is substantially free from copper and iron containing species. For purposes of the invention, the molecular weight is determined using a gel permeation chromatography with a 90* light scattering and refractive index detectors. Two columns of PW4000 and PW2500, a methanol-water fluent of 75/25 wt/wt adjusted to 50mM sodium chloride and a mixture of polyethylene glycol and polyethylene oxide molecules with well defined molecular weights ranging from 325,000 to 194 are used.

-6 As used herein, "substantially free from" means that transition metal containing species are present in the electron rich polymer in amounts which are insufficient to cause further degradation of the OUOC. Preferably transition metal containing species are present in the electron rich polymer in amounts less than about 100 ppm, in some embodiments less than about 50 ppm and in some embodiments less than about 20 ppm. Suitable electron rich polymers include polymers comprising esters, acids, amines, carbonates, carboxylates, thiols, lactates, amides, carbamates, phosphates, phosphines, nitriles, lactams, and combinations thereof. Polymers which do not have groups with at least one free electron pair, such as polymers comprising only ether groups. alcohol groups or combinations thereof are not electron rich polymers are defined herein. A wide concentration of electronic donating groups may be included, however, the higher the concentration of electron donating groups, the less electron rich polymer will need to be used. Specific examples include homopolymers and random or block copolymers of methacrylic acid, acrylic acid, itaconic acid, fumaric acid, maleic acid, vinylpyrollidone, vinylmethacetimide, combinations thereof and the like. More specific examples include poly(acrylic acid), poly(vinylpyrollidone) and poly(vinylmethylacetamide) and combinations thereof and the like. In one embodiment the electron rich polymer is polyvinyl pyrrolidone. The electron rich polymer is present in the ophthalmic composition in stabilizing effective amounts. A stabilizing effective amount will vary depending upon the OUOC, the concentration of the OUOC and the concentration of other components in the ophthalmic composition, but generally stabilizing effective amounts are those sufficient to provide at least about a 5% improvement in stability. Suitable amounts of electron rich polymer include between about 10 and about 5,000 ppm, in some embodiments between about 100 and about 5,000 ppm, in some embodiments between about 500 and about 3,000 ppm. 'rhe OUOC and electron rich polymer may be combined in any suitable ophthalmically compatible carrier. Suitable carriers include water, saline solution, mineral oil, petroleum jelly, water soluble solvents, such as Cj- 2 o alcohols, C 15

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2 0 amides, C 1

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5 20 alcohols substituted with zwitterions, vegetable oils or mineral oils comprising from 0.5 to 5% by weight hydroxyethylcellulose, ethyl oleate, carboxymethylcellulose, polyvinyl-pyrrolidone and other non-toxic water-soluble polymers for ophthalmic uses, such as, for example cellulose derivatives, such as methyleellulose, alkali metal salts of carboxy-methylcellulose, hydroxymethyleellulose, hydroxyethyleellulose, methythydroxypropyl-cellulose, hydroxypropylcellulose, chitosan and scleroglucan, acrylates or methacrylates, such as salts of poly(acrylic acid) or ethyl acrylate, polyacrylamides, natural products, such as gelatin, alginates, pectins, tragacanth, karaya gum, xanthan gum, carrageenin, agar and acacia, starch derivatives, such as starch acetate and hydroxypropyl starch, and also other synthetic products, such as poloxamers, e.g. Poloxamer F 127, polyvinyl alcohol, polyvinylpyrrolidone. polyvinyl methyl ether, p1olyethylene oxide, preferably cross-linked poly(acrylic acid), such as neutral Carbopol, or mixtures of those polymers. Preferred carriers are water, cellulose derivatives. such as methylcellulose, alkali metal salts of carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, methylhydroxypropyleel lulose and hydroxypropylcellulose, neutral Carbopol, or mixtures thereof. The concentration of the carrier is, for example, from 0.1 to 100000 times the concentration of the active ingredient combinations thereof and the like. When the ophthalmic composition is an eye drop. preferred carriers include water, pH buffered saline solution, mixtures thereof and the like. The oxidatively stable compositions of the present invention may also be used as the packaging or storage solution for an ophthalmic device, such as a contact lens. When the ophthalmic composition of the present invention is used as a packaging solution for a contact lens the carrier comprises a buffered saline solution. Any contact lens could be packaged with the oxidatively stable ophthalmic compositions of the present invention, including, but not limited to commercially available hydrogel formulations such as etafilcon, polyinacon, vifilcon, genfilcon A, lenefilcon A, galyfilcon, senofilcon, balafilcon, lotrafilcon A, lotrafilcon B and the like.

-8 The compositions of the present invention may further comprise additional components such as antioxidants, demulcents, antibacterial agents, solubilizers, surfactants, buffer agents, tonicity adjusting agents, chelating agents, preservatives, wetting agents, thickeners, combinations thereof and the like. The oxidatively stable compositions of the present invention must be ophthalmically compatible. If the addition of the electron rich polymer decreases the pH1 of the ophthalmic composition to an undesirable level, a stoichometric amount of a base, such as sodium hydroxide, or a buffering agent, such as sodium borate, may be added. Generally a pH between about 5 and about 9, in some embodiments between about 6 to about 8 is desired. In some embodiments, the stabilizing effect of the electron rich polymer may be most effective at a pH of about 6.5 to about 7.5. The oxidatively stable compositions of the present invention may be formed by mixing the OUOC and the electron rich polymer with the selected carrier. When a liquid composition, such as an eye drop or packaging solution for a contact lens, the OUOC and the electron rich polymer are dissolved in the carrier. When the oxidatively stable composition is a gel or an ointment, the OUOC and electron rich polymer may be incorporated in any suitable manner, such as dissolved, mixed or compounded into the selected carrier. It is generally desirable that the shelf life of the oxidatively stable compositions of the present invention be in excess of about 6 months, and in some instances greater than about 1 year, or even more than about 2 years. During the shelf life of the oxidatively stable compositions it is desirable that at least about than 80% of the original concentration of the OUOC remains, and in some embodiments greater than about 90%. EXAMPLES These examples do not limit the invention. They are meant only to suggest a method of practicing the invention. Those knowledgeable in contact lenses as well as other specialties may find other methods of practicing the invention. However, those methods are deemed to be within the scope of this invention.

-9 Examples 1 -3 The solutions of Table I were formed by combining the listed components with reverse osmosis purified water to a total volume of I liter. The p1I of these solutions was adjusted to 7.5, 7.3, and 6.9 with addition of HCL To each solution was added 80 ppm of ketotifen fumarate, 3.0 ml of each of these solutions were placed in a number of vials. Each vial was autoclaved, heating to 121 *C and holding at that temperature for 30 minutes, for the number of cycles indicated in Table 2, using three vials per each set of conditions. The concentration of ketotifen was determined using IHPLC using an HP 1100 with an Agilent Zorbax Eclipse XDB-C1 8 and Rapid Resolution HT 50 x 4.6 mm x 1.8 [t column and the following conditions: Detector Wavelength: 299 nm Flow rate: 1.0 mL/min Injection Volume: 3 pL Mobile Phase: Eluent A: 17 % acetonitrile in 0.025 M dihydrogen potassium phosphate buffer 0.2 % triethylamine, 0.13 % o-phosphoric acid Eluent B:50 % acetonitrile in 0.025 M dihydrogen potassium phosphate buffer 0.2 % triethylamine, 0.13 % o-phosphoric acid m ne (n in Eluent A % Eluent B (%) 0 100 0 5 100 0 20 0100--~ 21 100 0 25 100 - 10 Table 2 shows the average of three measurements of the concentration of ketotifen remaining in the vials as a percentage of the original concentration. Table I Comp (gm/100 l ) Ex .1 Ex. 2 Ex.3 CEx CEx2 CEx NaCI 0.83 0.83 0.83 0.83 0.83 0.83 Boric acid 0.91 0.91 0.91 0.91 0.91 0.91 Sodium borate 0.1 0.1 0.1 0.1 0.1 0.1 PAA (MW 0.1 0.1 0.1 0 0 0 225,000) abe 2 - Ketotifen concentration after autoclaving Ex. x.2 Ex.3 CEx I CEx 2 CEx 3 PH 7.5 7.3 6.9 7.5 7.3 6.9 Cycle 100 100 100 100 100 100 1icycle 64 96 96 0 0 0 2 cycle 55 86 84 3 cycle 22 64 62 Examples 4-6 The solution of Example 1 was made but with the amounts of PAA shown in Table 3, below. The pH of each solution was adjusted to 7.22 using 0.1 N HCL. As in Example 1 80 ppm (wt) ketotifen fumarate added to each solution. The stability of the solutions was tested as in Example 1. The results are shown in Table 3. Table 3 Ex. 4 Ex. 5 Ex. 6 [PAA] ppm 0500 2000 5000 cycles 100 100 100 cyc 88 94 94 2 Cl 64 81 83 3 cycles 36 66 70 Example 7 A ketotifen fumarate solution was formed by combining the components listed in Table 4 with reverse osmosis purified water to a total volume of I liter. The pH of the solution was about 7.2. 3.0 ml of the solution was placed in each of three vials. The initial concentration of ketotifen was determined using -IPLC. The vials were autoclaved, heating to 121*C and holding at that temperature for 30 minutes. The concentration of ketotifen remaining after one autoclave cycle was determined using HPLC as described above. The average concentration of ketotifen furmarate remaining was 80 tg/ml. Accordingly, only about 17% of the ketotifen fumarate was lost during a single autoclave cycle. A control solution, having the components in Table 4, but without the 400 ppm PVP lost over 50% of the ketotifen fumarate during a single autoclave cycle. Table 4 Component NaCl 0.83 gm/nml Boric acid 0.9] m/ml Sodium borate _ 0.1 gm/mI PVP (MW = 90,000) 400 ppm Ketotifen fumnarate 97 /m Thus the foregoing examples clearly show that the inclusion of at least one electron rich polymer, such as poly(acrylic acid), significantly improves the stability of an oxidatively unstable ophthalmic composition, like ketotifen fumarate. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia.

Claims (3)

1. 2. The method of claim 1, wherein said polyvinyl pyrrolidone is present in an amount between 10 and 5000 ppm.
2. 3. The method of claim 2, wherein said polyvinyl pyrrolidone is present in an amount between 100 and 5000 ppm.
3. 4. An autoclavable solution comprising an ophthalmic solution comprising at least one oxidatively unstable ophthalmic compound, which shows greater than 10% degradation when autoclaved in solution with at least one oxidative catalyst, but shows less than 10% degradation when autoclaved under the sanie conditions without said at least one oxidative catalyst, and a stabilizing effective amount of polyvinyl pyrrolidone wherein said oxidatively unstable ophthalmic compound is selected from the group consisting of ketotefin fumarate, I 1-dihydro-I 1 -(1 -methyl-4-piperidinyl idene) SH- imidazo[2,1 -b][3]benzazepine-3-carboxaldehyde, and mixtures thereof wherein said polyvinyl pyrrolidone has a weight averaged molecular weight between 1000 and 2,000,000 and is substantially free from transition metal containing species. -13 5 The autoclavable solution of claim 4, wherein said polyvinyl pyrrolidone is present in an amount between 10 and 5000 ppm. 6 The autoclavable solution of claim 5, wherein said polyvinyl pyrrolidone is present in an amount between 100 and 5000 ppm.