Method for solubilizing pyridonecarboxylic acids comprising the use of an arylcarboxylic acid as solubilizer

Abstract: A method for solubilizing a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof, which comprises adding an arylcarboxylic acid of the formula (I): L 1 -R 1 COOH wherein L 1 is an optionally substituted heterocyclic group or aryl group having not more than 14 carbon atoms, and R 1 is an optionally substituted alkyl group having not more than 4 carbon atoms or a single bond, to the pyridonecarboxylic acid or the pharmacologically acceptable salt thereof, a solubilizer thereof and an aqueous solution containing a solubilized pyridonecarboxylic acid. According to the solubilization method of the present invention, the solubility of pyridonecarboxylic acid compounds and salts thereof at near physiological pH can be increased, thereby making the production of an aqueous solution to be used as an eye drop, nasal drop, ear drop and the like possible.

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for solubilizing a pyridonecarboxylic acid, which is an amphoteric compound and which has an antibacterial activity, or a pharmacologically acceptable salt thereof; the use of an arylcarboxylic acid as a solubilizer of a pyridonecarboxylic acid and an aqueous solution containing a solubilized pyridonecarboxylic acid. BACKGROUND OF THE INVENTION Pyridonecarboxylic acid and pharmacologically acceptable salts thereof have been known to be extremely superior synthetic antibacterial agents. However, since said pyridonecarboxylic acid has carboxylic acid and the dihydropyridine skeleton in a molecule, forming a zwitterion, it shows strikingly low solubility in water at a physiological pH, i.e., neutral range. This imposes a problem that an aqueous solution containing pyridonecarboxylic acid or a pharmacologically acceptable salt thereof cannot be formulated into a pharmaceutical preparation at a neutral pH. Hardly soluble pyridonecarboxylic acid and a pharmacologically acceptable salt thereof are solubilized by, for example, adding an inorganic acid to pyridonecarboxylic lactate (USP 4705789, USP 4808583, USP 4808585), or adding a base in excess to pyridonecarboxylic acid (USP 4772605), or adding a metal compound comprising aluminum, magnesium or zinc to pyridonecarboxylic acid or a salt thereof (Japanese Patent Unexamined Publication No. 188626/1988). The aqueous preparations thus obtained are associated with variations in pH which are caused by the solubilizer added, and the toxicity of the solubilizer itself which may cause a local irritation and the like, possibly leading to unexpected disorders. Thus, there has not been provided an aqueous preparation containing solubilized pyridonecarboxylic acid, which is safe and useful at a physiological pH, i.e., about neutral pH. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for solubilizing a pyridonecarboxylic acid and a pharmacologically acceptable salt thereof. Another object of the present invention is to provide the use of an acrylcarboxylic acid as a solubilizer of a pyridonecarboxylic acid. Yet another object of the present invention is to provide an aqueous solution containing a solubilized pyridonecarboxylic acid and an arylcarboxylic acid. A further object of the present invention is to provide an aqueous solution containing a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof at a high concentration. According to the present invention, it has now been found that the addition of an arylcarboxylic acid to a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof leads to successful solubilization thereof at around a physiological pH. Thus, the present invention provides the following. (1) A method for solubilizing a pyridonecarboxylic acid which is at least one compound selected from the group consisting of lomefloxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, fleroxacin, cinoxacin, levofloxacin and sparfloxacin or a pharmacologically acceptable salt thereof, which comprises adding an arylcarboxylic acid which is at least one compound selected from the group consisting of pranoprofen, ibuprofen, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid to the pyridonecarboxylic acid or the pharmacologically acceptable salt thereof. (2) The method above, wherein the arylcarboxylic acid is added in a proportion of 0.001-50 parts by weight per part by weight of the pyridonecarboxylic acid. (3) Use of an arylcarboxylic acid selected from the group consisting of pranoprofen, ibuprofen, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid as a solubilizer of a pyridonecarboxylic acid which is at least one compound selected from the group consisting of lomefloxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, fleroxacin, cinoxacin, levofloxacin and sparfloxacin or a pharmacologically acceptable salt thereof. (4) The use above, wherein the arylcarboxylic acid is added in a proportion of 0.001-50 parts by weight per part by weight of the pyridonecarboxylic acid. (5) An aqueous solution comprising a pyridonecarboxylic acid which is at least one compound selected from the group consisting of lomefloxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, fleroxacin, cinoxacin, levofloxacin and sparfloxacin or a pharmacologically acceptable salt thereof solubilized by the method of claim 1, and an arylcarboxylic acid which is at least one compound selected from the group consisting of pranoprofen, ibuprofen, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid. (6) The solution above, which is an eye drop. (7) The solution above, which is a nasal drop. (8) The solution above, which is an ear drop. (9) The aqueous solution above, which comprises at least a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof in a concentration of 0.2 - 5.0 (w/v) %. DETAILED DESCRIPTION OF THE INVENTION The solubilizing method of the present invention comprises the addition of a solubilizer containing an arylcarboxylic acid as an active ingredient to a pyridonecarboxylic acid, which is an amphoteric compound and which has an antibacterial activity, or a pharmacologically acceptable salt thereof. For example, an arylcarboxylic acid is added to a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof. To be specific, the arylcarboxylic acid is dissolved in water and adjusted to pH 3 and added. Thereafter, the pH is adjusted to 3.5-8.5, preferably 6-8. Said arylcarboxylic includes 2-naphthoic acid, 2-naphthylacetic acid, 2-naphthoxyacetic acid; ibuprofen, bromfenac, pranoprofen, The pyridonecarboxylic acid in the present specification has a solubility in water which corresponds to the solubility of from "somewhat insoluble" to "sparingly soluble" as defined in Japan Pharmacopoeia, 12th Edition, Explanation (1991), Hirokawashoten, Tokyo, p. A-45, General Notices 24, Description, or from "sparingly soluble" to "practically insoluble" as defined in International Pharmacopoeia III. The pyridonecarboxylic acid include enoxacin: [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-carboxylic acid], ofloxacin: [(±)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid], cinoxacin: [1-ethyl-1,4-dihydro-4-oxo-[1,3]-dioxolo[4,5-g]cinnoline-3-carboxylic acid], ciprofloxacin: [1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid], sparfloxacin: [5-amino-1-cyclopropyl-7-(cis-3,5-dimethyl-1-piperazinyl)-6,8-difluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid], tosufloxacin: [(±)-7-(3-amino-1-pyrrolidinyl)-1-(2,4-difluorophenyl)-6-fluoro-1,4-dihydro-4-oxo-1-naphthyridine-3-carboxylic acid], norfloxacin: [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid], fleroxacin: [6,8-difluoro-1-(2-fluoroethyl)-1,4-dihydro-7-(4-methyl-1-piperazinyl)-4-oxo-3-quinolinecarboxylic acid], levofloxacin: [(-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid], lomefloxacin: [1-ethyl-6,8-difluoro-1,4-dihydro-7-(3-methyl-1-piperazinyl)-4-oxo-3-quinolinecarboxylic acid], The pharmacologically acceptable salts of pyridonecarboxylic acid include, for example, acid addition salts with inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and the like, organic acids such as acetic acid, lactic acid, succinic acid, methanesulfonic acid, maleic acid, malonic acid, gluconic acid and the like, and amino acids such as aspartic acid, glutamic acid and the like; metal salts such as sodium salt, potassium salt and the like; and the like. The amount of the arylcarboxylic acid to be added to the pyridonecarboxylic acid or a pharmacologically acceptable salt thereof is preferably about 0.001-10 parts by weight per part by weight of the pyridonecarboxylic acid or pharmacologically acceptable salt thereof. The solubilizer of the pyridonecarboxylic acid and a pharmacologically acceptable salt thereof contains arylcarboxylic acid as an active ingredient in almost the same amount as mentioned above. The solvent to be used for the aqueous solution of the present invention may be, for example, purified water, particularly distilled water for injection. The concentration of the active ingredient of the aqueous solution, i.e. pyridonecarboxylic acid, can be markedly increased by arylcarboxylic acid, preferably to 0.2-5.0 (w/v)%. The arylcarboxylic acid to be used for the aqueous solution of the present invention may be those mentioned above. Said aqueous solution may contain various additives as appropriate, such as buffer, isotonizing agent, solubilizer, antiseptic, thickener, chelating agent, aromatic and the like. Examples of the buffer include phosphate buffer, borate buffer, citrate buffer, tartrate buffer, acetate buffer, amino acid and the like. Examples of the isotonizing agent include sugars such as sorbitol, glucose, mannitol and the like, polyhydric alcohols such as glycerol, propylene glycol and the like, salts such as sodium chloride and the like, and the like. Examples of the solubilizer include non-ionic surfactants such as polyoxyethylenesorbitane monoolate, polyoxyethyleneoxystearic acid triglyceride, polyethylene glycol, polyoxyethylene hydrogenated castor oil and the like, and the like. Examples of the antiseptic include quaternary ammonium salts such as benzalkonium chloride, benzethonium chloride, cetylpyridinium chloride and the like, p-hydroxybenzoates such as methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate and the like, benzyl alcohol, phenetyl alcohol, sorbic acid, salts thereof, thimerosal, chlorobutanol, sodium dehydroacetate and the like. Examples of the thickener include polyvinylpyrrolidone, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, salts thereof and the like. Examples of the chelating agent include sodium edetate, citric acid, salt thereof and the like. Examples of the aromatic include 1-menthol, borneol, camphor, eucalyptus oil and the like. The aqueous solution of the present invention is used as an eye drop, nasal drop or ear drop. When it is used as an eye drop, its pH is generally adjusted to about 3.5-8.5, preferably about 6-8, when it is used as a nasal drop, its pH is generally adjusted to about 3.5-8.5, preferably about 6-8, and when it is used as an ear drop, its pH is generally adjusted to about 3.5-8.5, preferably about 6-8. While the method for producing the aqueous solution of the present invention varies depending on the kind of a desired solution, a known method can be used to produce such aqueous solution. When the aqueous solution of the present invention is used as an eye drop, for example, the dose thereof need only be sufficient to effectively suppress inflammation in the eye, and may vary according to symptoms, the kind of inflammation, the patients in need of said solution and the like. A typical dose is 20-200 µL, preferably 50-100 µL, which may be administered 1 to 12 times a day. The present invention is described in more detail by way of Examples and Experimental Examples, which should not be construed as limiting the invention. Experimental Example 1 : Effect of arylcarboxylic acid on solubility of pyridonecarboxylic acid - 1 To a 0.1% aqueous sodium dihydrogenphosphate solution (100 ml) containing pranoprofen, ibuprofen or bromfenac was added norfloxacin or enoxacin in excess, and the pH thereof was adjusted to 7-8 with hydrochloric acid or sodium hydroxide. The mixture was shaken for one week at 25°C and filtered through a 0.45 µm membrane filter, which was followed by the determination of a norfloxacin or enoxacin content by high performance liquid chromatography. The results are shown in Table 1. solubility (%) norfloxacin enoxacin pH 7 pH 8 pH 7 pH 8 without addition 0.040 0.036 0.026 0.025 pranoprofen added 0.181 0.081 0.078 0.063 ibuprofen added 0.043 0.042 0.030 0.028 bromfenac added 0. 041 0.054 0.032 0.035 Experimental Example 2: Effect of arylcarboxylic acid on solubility of pyridonecarboxylic acid - 2 To a 0.1% aqueous sodium dihydrogenphosphate solution (100 ml) containing 2-naphthoic acid, 2-naphthylacetic acid or 2-naphthoxyacetic acid was added norfloxacin or enoxacin in excess, and the pH thereof was adjusted to 8-9 with hydrochloric acid or sodium hydroxide. The mixture was shaken for one week at 25°C and filtered through a 0.45 µm membrane filter, which was followed by the determination of a norfloxacin or enoxacin content by high performance liquid chromatography. The results are shown in Table 2. solubility (%) norfloxacin enoxacin pH 8 pH 9 pH 8 pH 9 without addition 0.036 0.106 0.025 0.071 2-naphthoic acid added 0.092 0.159 0.054 0.119 2-naphthylacetic acid added 0.058 0.206 0.042 0.083 2-naphthoxyacetic acid added 0.075 0.160 0.047 0.099 Experimental Example 3 : Effect of arylcarboxylic acid on solubility of pyridonecarboxylic acid - 3 To a 0.1% aqueous sodium dihydrogenphosphate solution (100 ml) containing pranoprofen, ibuprofen, diclofenac, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid or 2-naphthoxyacetic acid was added lomefloxacin in excess, and the pH thereof was adjusted to 8-9 with hydrochloric acid or sodium hydroxide. The mixture was shaken for one week at 25°C and filtered through a 0.45 µm membrane filter, which was followed by the determination of a lomefloxacin content by high performance liquid chromatography. The results are shown in Table 3. solubility (%) lomefloxacin pH 8 pH 9 without addition 0.118 0.300 pranoprofen added 0.214 ― ibuprofen added ― 0.350 diclofenac added 0.139 0.333 bromfenac added ― 0.470 2-naphthoic acid added 0.230 ― 2-naphthylacetic acid added 0.180 ― 2-naphthoxyacetic acid added 0.204 ― As is evident from the results shown in Tables 1 to 3, the addition of at least one member selected from the group consisting of arylcarboxylic acid compounds such as pranoprofen, ibuprofen, diclofenac, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid and the like increased the solubility of a pyridonecarboxylic acid compound, such as norfloxacin, enoxacin, lomefloxacin and the like, and salts thereof, by about 1.5-3 times. Eye drops, nasal drops and ear drops having the following formulations were prepared. Neither of them showed precipitation of crystals after preservation for 4 days at room temperature. The solubility of norfloxacin in 0.1% phosphate buffer (pH 8) and 1.6% borate buffer (pH 7) was 0.036% and 0.039%, respectively; the solubility of enoxacin in 0.1% phosphate buffer (pH 7) and 1.6% borate buffer (pH 6) was 0.028% and 0.17%, respectively; and the solubility of ofloxacin in physiological saline adjusted to pH 7 with phosphoric acid was 0.5%. Example 1 An eye drop having the following formulation was prepared.. norfloxacin 0.04 g bromfenac sodium 0.4 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 8) Example 2 An eye drop having the following formulation was prepared. norfloxacin 0.05 g 2-naphthylacetic acid 0.3 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 3 An ear drop having the following formulation was prepared. enoxacin 0.03 g ibuprofen 0.5 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 4 An eye drop having the following formulation was prepared. enoxacin 0.25 g 2-naphthoic acid 0.2 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 6) Example 5 A nasal drop having the following formulation was prepared. ofloxacin 0.8 g 2-naphthoic acid 0.1 g phosphoric acid 0.1 g sodium chloride 0.9 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 6 An ear drop having the following formulation was prepared. norfloxacin 0.04 g bromfenac sodium 0.4 g naphazoline hydrochloride 0.003 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 8) Example 7 An ear drop having the following formulation was prepared. norfloxacin 0.04 g bromfenac sodium 0.4 g chlorpheniramine maleate 0.03 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 8) Example 8 An eye drop having the following formulation was prepared. norfloxacin 0.04 g bromfenac sodium 0.4 g pyridoxine hydrochloride 0.1 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 8) Example 9 An eye drop having the following formulation was prepared. norfloxacin 0.05 g 2-naphthylacetic acid 0.3 g naphazoline hydrochloride 0.003 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 10 An eye drop having the following formulation was prepared. norfloxacin 0.05 g 2-naphthylacetic acid 0.3 g chlorpheniramine maleate 0.03 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 11 An eye drop having the following formulation was prepared. norfloxacin 0.05 g 2-naphthylacetic acid 0.3 g pyridoxine hydrochloride 0.1 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 12 A nasal drop having the following formulation was prepared. enoxacin 0.03 g ibuprofen 0.5 g naphazoline hydrochloride 0.003 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 13 An eye drop having the following formulation was prepared. enoxacin 0.03 g ibuprofen 0.5 g chlorpheniramine maleate 0.03 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 14 A nasal drop having the following formulation was prepared. enoxacin 0.03 g ibuprofen 0.5 g pyridoxine hydrochloride 0.1 g phosphoric acid 0.1 g con. glycerol 2.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 7) Example 15 An eye drop having the following formulation was prepared. enoxacin 0.25 g 2-naphthoic acid 0.2 g naphazoline hydrochloride 0.003 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 6) Example 16 An eye drop having the following formulation was prepared. enoxacin 0.25 g 2-naphthoic acid 0.2 g chlorpheniramine maleate 0.03 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 6) Example 17 An eye drop having the following formulation was prepared. enoxacin 0.25 g 2-naphthoic acid 0.2 g pyridoxine hydrochloride 0.1 g boric acid 1.6 g hydrochloric acid appropriate amount sodium hydroxide appropriate amount sterile purified water appropriate amount total amount 100 ml (pH 6) According to the solubilizing method of the present invention, the solubility of a pyridonecarboxylic acid compound and a salt thereof at near physiological pH can be increased, thereby making the production of an aqueous solution to be used as an eye drop, nasal drop, ear drop or the like possible. This application is based on application No. 21807/1997 filed in Japan.

Claims: A method for solubilizing a pyridonecarboxylic acid which is at least one compound selected from the group consisting of lomefloxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, fleroxacin, cinoxacin, levofloxacin and sparfloxacin or a pharmacologically acceptable salt thereof, which comprises adding an arylcarboxylic acid which is at least one compound selected from the group consisting of pranoprofen, ibuprofen, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid to the pyridonecarboxylic acid or the pharmacologically acceptable salt thereof. The method of claim 1 wherein the arylcarboxylic acid is added in a proportion of 0.001-50 parts by weight per part by weight of the pyridonecarboxylic acid. Use of an arylcarboxylic acid selected from the group consisting of pranoprofen, ibuprofen, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid as a solubilizer of a pyridonecarboxylic acid which is at least one compound selected from the group consisting of lomefloxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, fleroxacin, cinoxacin, levofloxacin and sparfloxacin or a pharmacologically acceptable salt thereof. The use of claim 3, wherein the arylcarboxylic acid is added in a proportion of 0.001-50 parts by weight per part by weight of the pyridonecarboxylic acid. An aqueous solution comprising a pyridonecarboxylic acid which is at least one compound selected from the group consisting of lomefloxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, fleroxacin, cinoxacin, levofloxacin and sparfloxacin or a pharmacologically acceptable salt thereof solubilized by the method of claim 1, and an arylcarboxylic acid which is at least one compound selected from the group consisting of pranoprofen, ibuprofen, bromfenac, 2-naphthoic acid, 2-naphthylacetic acid and 2-naphthoxyacetic acid. The solution of claim 5 which is an eye drop. The solution of claim 5 which is a nasal drop. The solution of claim 5 which is an ear drop. The aqueous solution of claim 5, which comprises at least a pyridonecarboxylic acid or a pharmacologically acceptable salt thereof in a concentration of 0.2 - 5.0 (w/v) %.

Inventors: SAWA SHIROU, SAWA, SHIROU
Applicants: SENJU PHARMA CO, SENJU PHARMACEUTICAL CO., LTD.
Application year: 1998
Main classification: A61K47
IPC codes: A61K9, A61K47, A61K31