The present invention relates to an aqueous sterile solution of atropine or its pharmaceutically acceptable salts for ophthalmic use, wherein the solution is filled in a light protective container.

BACKGROUND OF THE INVENTION

Myopia is an ophthalmic condition affecting more than l/5 ^th of the world population, especially children. Atropine is currently the most effective therapy for myopia control. Berton et al, “Stability of Ophthalmic Atropine Solutions for Child Myopia Control” teaches that 1% concentration atropine eye drops is effective in controlling myopic progression but causes important visual side effects resulting from cycloplegia and mydriasis. Several clinical trials have evaluated the safety and efficiency of atropine eye drops at lower concentrations and demonstrated that low-dose atropine eye drops such as 0.01% resulted in retardation of myopia progression, with significantly less side effects compared to higher concentration preparation.

Atropine Sulfate is the sulfate salt of atropine, a naturally -occurring alkaloid isolated from the plant Atropa belladonna. It functions as a sympathetic, competitive antagonist of muscarinic cholinergic receptors, thereby abolishing the effects of parasympathetic stimulation. Several clinical trials have evaluated the safety and efficacy of atropine eye drops and have demonstrated that atropine eye drops helped in retardation of myopia progression, with significantly less side effects compared to higher concentration preparation.

Till date, however, there appears to be a need of an improved, stable aqueous solution of atropine that is robust in terms of chemical stability. In fact, the inventors of the present invention while developing a robust aqueous sterile solution of atropine that can be directly instilled into the eyes without any further need of dilution or reconstitution, faced with a problem of generation of unwanted degradation product of atropine, particularly tropic acid, atropic acid and apotropine. Tropic acid is generated as a result of hydrolysis of atropine. The structure of the tropic acid is given in Formula I below:

Formula I

It is surprisingly found by the present inventors that when sodium citrate and citric acid are used as a buffer, there occurs no substantial increase in the level of these degradation products upon storage. For example, tropic acid, atropic acid and apotropine were found to be within the specified limit of NMT 7.0%, NMT 1.0% and NMT 1.0%, respectively, upon storage. Surprisingly, other buffers, such as acetate, borate and phosphate buffer, were less effective at controlling these degradation products, particularly tropic acid generation. Also, atropine solution prepared without using any buffer was similarly less effective at controlling generation of these degradation products.

SUMMARY OF THE INVENTION

The present invention provides an aqueous sterile solution for ophthalmic use filled in a light protective container said solution comprising: a. atropine sulfate at a concentration ranging from 0.001 % to 0.05 % w/v, b. buffer consisting of sodium citrate and citric acid, and c. purified sterile water, wherein the pH of the solution ranges from 4.5 to 5.8, and the solution is to be instilled in the eye without dilution or reconstitution.

In another embodiment, the present invention provides an aqueous sterile solution for ophthalmic use filled in a light protective container said solution comprising: a. atropine sulfate at a concentration ranging from 0.01 % w/v, b. buffer consisting of sodium citrate and citric acid, c. polyhexamethylene biguanide hydrochloride, and d. punned sterile water, wherein the pH of the solution ranges is about 5.5, and the solution is to be instilled in the eye without dilution or reconstitution.

DETAILED DESCRIPTION OF THE INVENTION

The term “sterile” as used in the context of the invention means a solution that has been brought to a state of sterility and has not been subsequently exposed to microbiological contamination, i.e. the sterility of the aqueous solution present in the container has not been compromised.

The term “light protective container” as used herein means a container that protects the contents from the effects of light by virtue of the specific properties of the material of which it is composed, including any coating applied to it, such as, for example, an opaque container or amber coloured container or a container coated with a light protective coating and the like.

The phrase “the solution is to be instilled in the eye without dilution or reconstitution” as used herein refers to direct topical administration of the aqueous drug solution to the eye of patient without involving any intermediate steps of manipulation, dilution, reconstitution, dispensing, sterilization, transfer, handling or compounding before administration of the drug solution. The aqueous drug solution is ready to use or ready to administer, which is meant for direct administration topically from the container to the eye of patient in need thereof, without dilution or reconstitution.

The term ‘stable’ as used herein means that the aqueous solution filled in the container is physically as well as chemically stable when stored at room temperature for a period of at least 6 months, preferably 12 months, more preferably 18 months, or more. The aqueous solution has been also found to be stable when stored at forced degradation conditions such as 60°C for 28 days. Also, the aqueous solution is stable upon storage at the accelerated stability condition of 40°C/25% relative humidity (RH) for at least 1 month, preferably 3 months, more preferably, 6 months. By the term “physical stability”, it means that the solution remains clear and colourless and free of any visible particulate matter upon storage. By the term “chemical stability”, it means that generation of degradation impurities, such as tropic acid, atropic acid and apotropine, are controlled. In preferred embodiments, tropic acid is not generated and the levels are not detected upon storage. The level of tropic acid upon storage at room temperature (25 °C and 60 % relative humidity) for a period of 6 months is not more than 0.5 % by weight of atropine, preferably not more than 0.2 % by weight of atropine. Further, the level of tropic acid upon storage at 30°C and 35% relative humidity or at accelerated condition of 40°C and 25% relative humidity for a period of at least 3 months, preferably 6 months, more preferably 12 months, is not more than 7.0 % by weight of atropine. Similarly, the level of atropic acid upon storage at 30°C and 35% relative humidity or at accelerated condition of 40°C and 25% relative humidity for a period of at least 3 months, preferably 6 months, more preferably 12 months, is not more than 1.0 % by weight of atropine. Further, the level of apotropine upon storage at 30°C and 35% relative humidity or at accelerated condition of 40°C and 25% relative humidity for a period of at least 3 months, preferably 6 months, more preferably 12 months, is not more than 1.0 % by weight of atropine. In another aspect, the level of total impurities upon storage at 30°C and 35% relative humidity or at accelerated condition of 40°C and 25% relative humidity for a period of at least 3 months, preferably 6 months, more preferably 12 months, is not more than 7.0 % by weight of atropine. Also, the assay of atropine remains within 93.0 % - 107.0 %, upon storage at room temperature for at least 3 months, preferably 6 months, more preferably 12 months.

The present invention provides an aqueous sterile solution for ophthalmic use fdled in a light protective container said solution comprising: a. atropine sulfate at a concentration ranging from 0.001 to 0.05 % w/v, b. buffer consisting essentially of sodium citrate and citric acid, and c. purified sterile water, wherein the pH of the solution ranges from 4.5 to 5.8, and the solution is to be instilled in the eye without dilution or reconstitution.

The term ‘consisting essentially of as used herein means that the aqueous solution of the present invention contains a buffer having mainly sodium citrate and citric acid or hydrates thereof.

The aqueous sterile solution for ophthalmic use according to the present invention comprises atropine sulfate as a sole therapeutically active ingredient. It is present in an amount ranging from about 0.001 % to 0.05 % w/v, preferably from about 0.005 % to 0.015 % w/v, more preferably, 0.006, 0.065, 0.007, 00075, 0.008, 0.0085, 0.009, 0.0095, 0.01, and/or 0.015 % w/v. In one preferred embodiment, atropine sulfate is present in the ophthalmic solution in an amount of 0.01 % w/v. The aqueous sterile solution for ophthalmic use according to the present invention comprises other pharmaceutically acceptable excipients, which may include, but are not limited to, pH adjusting agent/s, buffers, tonicity adjusting agents and preservatives.

The vehicle used for formulating the aqueous sterile solution of the present invention is purified/sterile water. The active and inactive ingredients are dissolved in purified water to form a clear and colorless aqueous solution.

The aqueous sterile solution of the present invention is free of deuterated water.

The aqueous sterile solution for ophthalmic use according to the present invention has a pH in the range of about 3.5 to 6.0, preferably, from about 4.5 to 5.8, more preferably, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7 or 5.8, or intermediate values thereof. According to preferred embodiments, the pH of the solution is 4.8 ± 0.2, more preferably 4.89 ± 0.2. In another preferred embodiment, the pH of the solution is 5.5 ± 0.2. The pH of the solution may be adjusted using a pH adjusting agent/s and/or a buffer. The pH adjusting agents that may be used in the ophthalmic solution according to the present invention include, but are not limited to, hydrochloric acid, sodium hydroxide or mixtures thereof.

The aqueous sterile solution for ophthalmic use according to the present invention comprises a buffer. The buffer that is preferably used is a citrate buffer, which consists of a mixture of citric acid and sodium citrate or hydrates thereof. In preferred embodiments, the citrate buffer is present in the aqueous solution at a concentration ranging from 0.01 to 1.5 % w/v, for example, 0.01% w/v, 0.02% w/v, 0.03% w/v, 0.04% w/v, 0.05% w/v, 0.055% w/v, 0.06% w/v, 0.065% w/v, 0.07% w/v, 0.075% w/v, 0.08% w/v, 0.085% w/v, 0.09% w/v, 0.095% w/v, 0.1% w/v, 0.2% w/v, 0.3% w/v, 0.4% w/v, 0.5% w/v, 0.6% w/v, 0.7% w/v, 0.8% w/v, 0.9% w/v, 1.0% w/v, 1.1% w/v, 1.2% w/v, 1.3% w/v, 1.4 % w/v or 1.5 % w/v. Preferably, at a concentration ranging from 0.05% w/v to 1.0% w/v. Preferably, the citrate buffer consists of citric acid monohydrate and sodium citrate dihydrate. Citric acid monohydrate may be present at a concentration ranging from 0.005 to 0.5 % w/v, preferably, at a concentration of 0.01 % to 0.3 % w/v, for example, 0.01 % w/v, 0.02% w/v, 0.03% w/v, 0.04% w/v, 0.05% w/v, 0.06% w/v, 0.07% w/v, 0.08% w/v, 0.09% w/v, 0.1% w/v, 0.2% w/v, or 0.3% w/v, and sodium citrate dihydrate may be present at a concentration ranging from 0.02 % to 1.0 % w/v, preferably, 0.03 % to 0.8 % w/v, more preferably, , more preferably, 0.03% to 0.5% w/v, for example, 0.03% w/v, 0.035% w/v, 0.04% w/v, 0.045% w/v, 0.05% w/v, 0.055% w/v, 0.06% w/v, 0.065% w/v, 0.07% w/v, 0.075% w/v, 0.08 % w/v, 0.09 % w/v, 0.1% w/v, 0.2% w/v, 0.3% w/v, 0.4% w/v or 0.5% w/v.

It has been surprisingly found by the present inventors that when sodium citrate and citric acid are used as a buffer, the generation of degradation impurities, such as tropic acid, atropic acid and apotropine, is effectively controlled and there occurs no substantial increase in the level of tropic acid, atropic acid or apotropine impurities generated upon storage. Surprisingly, other buffers, such as acetate, borate and phosphate buffers, fail to control these degradation impurities, such as, tropic acid, atropic acid, apotropine, generation. Also, an atropine solution prepared without using any kind of buffer failed to control such degradation impurities.

The aqueous sterile solution for ophthalmic use according to the present invention comprises a tonicity adjusting agent. The tonicity adjusting agent that may be used in the ophthalmic solution according to the present invention includes, but is not limited to, polyethylene glycol, propylene glycol, glycerol, sodium chloride, potassium chloride, sodium bromide, calcium chloride, mannitol, sorbitol, dextrose, sucrose, mannose and the like and mixtures thereof. In one preferred embodiment, the tonicity adjusting agent used in the ophthalmic solution according to the present invention is sodium chloride. Sodium chloride may be present in the solution at a concentration ranging from about 0.3 % to 0.9 % w/v. In some embodiments, a combination of sodium chloride and mannitol may be used as tonicity adjusting agent. In preferred embodiments, only sodium chloride is used as a tonicity adjusting agent at a concentration ranging from 0.7 to 0.9 % w/v. The aqueous sterile solution of the present invention is characterized by osmolalities of 250 to 350 mOsm/kg, preferably, 270-350 mOsm/kg, more preferably, 275, 280, 285, 290, 295, 300, 305, 310, 315, 320, 325, 330, 335, 340 or 345 mOsm/kg.

The aqueous sterile solution for ophthalmic use according to the present invention further comprises a preservative such as polyhexamethylene biguanide or its salt like hydrochloride salt, benzyl alcohol, cetrimide, chlorobutanol, mercurial preservatives like phenylmercuric nitrate, phenylmercuric acetate, thimerosal, phenylethyl alcohol, polyquad®, stabilized peroxides and perborates, stabilized oxychloro compounds, edetate disodium, boric acid, borates, parabens (such as methyl-propyl, isopropyl and butylparaben), pyruvates, sorbic acid/potassium sorbate, metal ions, and the like and mixtures thereof. In preferred embodiments, the ophthalmic solution according to the present invention contains polyhexamethylene biguanide. The polyhexamethylene biguanide may be present at a concentration ranging from 0.001 % to 0.5 % w/v, preferably, at a concentration ranging from 0.002 % to 0.5 % w/v, more preferably, 0.005 % w/v ,0.01% w/v, 0.015% w/v, 0.02% w/v, 0.025% w/v, 0.03% w/v, 0.035% w/v, 0.04 % w/v, 0.045% w/v , 0.05% w/v, 0.1% w/v, 0.15% w/v, 0.2% w/v, 0.25% w/v, 0.30% w/v, 0.35% w/v, 0.40% w/v, 0.45% w/v or 0.5 % w/v. In preferred embodiments, the aqueous solution according to the present invention is devoid of benzalkonium chloride.

The use of polyhexamethylene biguanide as a preservative has been found to be advantageous over other widely used preservatives like benzalkonium chloride because an aqueous solution comprising polyhexamethylene biguanide shows lower mydriatic action than a solution which comprises benzalkonium chloride. It is noteworthy that mydriatic action, which leads to dilatation of pupil, is undesirable for the treatment of myopia.

In preferred embodiments, the aqueous sterile solution for ophthalmic use according to the present invention is free of chelating agents, such as, ethylenediamine tetraacetic acid (EDTA), cyclohexanediamine tetraacetic acid (CDTA), hydroxyethylethylenediamine triacetic acid (HEDTA), diethylenetriamine pentaacetic acid (DTP A), dimercaptopropane sulfonic acid (DMPS), dimercaptosuccmic acid (DMSA), and aminotrimethylene phosphonic acid (ATP A).

In preferred embodiments, the aqueous sterile solution for ophthalmic use according to the present invention is free of water soluble polymers, for example, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, polyvinylpyrrolidone and the like.

The aqueous sterile solution for ophthalmic use according to the present invention is filled into a light protective container which protects the aqueous solution contained therein from the effects of light by virtue of the specific properties of the material of which it is composed, for example, a container being opaque or amber coloured or a container coated with a light protective coating. Light protective containers that may be used include, but are not limited to, opaque polyethylene, polypropylene or low-density polyethylene containers. In a preferred embodiment, the aqueous stable solution for ophthalmic use according to the present invention is filled into a light protective opaque polyethylene plastic bottle. The light protective container may be in single-use format or multi -dose format.

In one preferred embodiment, the aqueous sterile solution for ophthalmic use according to the present invention comprises a low concentration of atropine sulfate (0.005 to 0.015 % w/v), citrate buffer to maintain the pH of the solution in the range of 4.5 to 5.8, polyhexamethylene biguanide as a preservative, a tonicity adjusting agent and a pH adjusting agent, wherein the solution is free of benzalkonium chloride, deuterated water and water soluble polymers.

In another preferred embodiment, the aqueous sterile solution for ophthalmic use is filled in a light protective container and comprises: a. atropine sulfate at a concentration of 0.01 % w/v, b. a buffer consisting essentially of sodium citrate and citric acid, and c. purified water, wherein the pH of the solution is 4.8 ± 0.2, and the solution is to be instilled in the eye without dilution or reconstitution.

In yet another embodiment, there is provided an aqueous sterile solution for ophthalmic use filled in a light protective container, said solution comprising: a. atropine sulfate at a concentration of about 0.01 % w/v, b. a buffer consisting essentially of sodium citrate and citric acid, c. polyhexamethylene biguanide, and d. purified water, wherein the pH of the solution ranges from 4.5 to 5.8 and the solution is to be instilled in the eye without dilution or reconstitution.

In another preferred embodiment, there is provided an aqueous sterile solution for ophthalmic use filled in a light protective container, said solution consisting essentially of: a. atropine sulfate at a concentration of 0.01 % w/v, b. a buffer consisting essentially of sodium citrate and citric acid, c. polyhexamethylene biguanide at a concentration ranging from 0.001 % to 0.5 % w/v, d. a tonicity adjusting agent consisting essentially of sodium chloride, and e. purified water; wherein the pH of the solution is 4.8 ± 0.2, and the solution is to be instilled in the eye without dilution or reconstitution. In another preferred embodiment, there is provided an aqueous sterile solution for ophthalmic use filled in a light protective container, said solution consisting essentially of: a. atropine sulfate at a concentration of 0.01 % w/v, b. a buffer consisting essentially of sodium citrate at a concentration ranging from 0.03 % to 0.8 % w/v and citric acid at a concentration ranging from 0.005 % to 0.5 w/v, c. polyhexamethylene biguanide at a concentration ranging from 0.001 % to 0.5 % w/v, d. a tonicity adjusting agent consisting essentially of sodium chloride, and e. purified water, wherein the pH of the solution is 4.8 ± 0.2, and the solution is to be instilled in the eye without dilution or reconstitution.

In another preferred embodiment, the aqueous sterile solution for ophthalmic use is filled in a light protective container, said solution consisting of: a. atropine sulfate at a concentration of 0.01 % w/v, b. a buffer consisting of sodium citrate dihydrate at concentration of about 0.055 %w/v and citric acid monohydrate at the concentration of about 0.01% w/v, c. polyhexamethylene biguanide at a concentration of 0.005 % w/v, d. sodium chloride, and e. purified water, wherein the pH of the solution is 4.8 ± 0.2, and the solution is to be instilled in the eye without dilution or reconstitution.

In another embodiment, there is provided a method of treating myopia comprising administering to a patient in need thereof an aqueous sterile solution for ophthalmic use filled in a light protective container, said solution comprising: a. atropine sulfate at a concentration ranging from 0.001 % to 0.05 % w/v, b. a buffer consisting essentially of sodium citrate and citric acid, and c. purified water, wherein the pH of the solution ranges from 4.5 to 5.5 and the solution is to be instilled in the eye without dilution or reconstitution. In yet another embodiment, there is provided a method of treating myopia comprising administering to a patient in need thereof an aqueous sterile solution as disclosed in any one of the preceding embodiments.

In yet another embodiment, there is provided use of the aqueous sterile solution as disclosed in any one of the preceding embodiments for the treatment of myopia.

In one embodiment, the present invention provides a process of preparing an aqueous sterile solution for ophthalmic use involving the steps of:

1. Dispensing and dissolving specified quantity of the sodium citrate dihydrate and citric acid monohydrate in water for injection to prepare a buffer solution;

2. Dispensing specified quantity of preservative such as polyhexamethylene biguanide, and adding it to the above buffer solution under stirring, until it is dissolved;

3. Dispensing specified quantity of atropine sulfate and adding in solution containing buffer and preservative;

4. Dispensing specified quantity of tonicity adjusting agent like sodium chloride and adding it to the solution containing buffer, preservative and atropine;

5. Adjusting the pH of the solution to 5.5±0.2 using pH adjusting agent/s if required and making the volume to 100 % with purified water;

6. Sterilizing the solution, preferably by filtering it through membrane filter to get sterile solution; and filling the solution in an opaque container like a light protective polyethylene plastic bottle.

While the present invention is disclosed generally above, additional aspects are further discussed and illustrated with reference to the examples set forth below. However, the examples are presented merely to illustrate the invention and should not be considered as limitations thereto.

EXAMPLE I

Table 1 below gives composition details of an ophthalmic solution according to one preferred embodiment of the present invention.

Table 1 : Composition details q.s.: quantity sufficient, # Only if required for pH adjustment.

Method of preparation of Composition A: The dispensed quantity of the sodium citrate dihydrate and citric acid monohydrate were dissolved in water for injection. To this buffer solution, the dispensed quantity of polyhexamethylene biguanide was added under stirring and dissolved. The dispensed quantity of atropine sulfate was added to the solution containing the buffer and preservative. After that, the dispensed quantity of sodium chloride was added to the solution containing the buffer, preservative and atropine. The pH of the solution was 4.8. The volume was made up to 100 % with water for injection. The formulation was filtered through a membrane filter to get the sterile solution. The above solution was filled in opaque light protective polyethylene plastic bottles.

Method of preparation of Composition B: The dispensed quantity of the sodium citrate dihydrate and citric acid monohydrate were dissolved in water for injection. To this buffer solution, the dispensed quantity of polyhexamethylene biguanide was added under stirring and dissolved. The dispensed quantity of atropine sulfate was added to the solution containing the buffer and preservative. After that, the dispensed quantity of sodium chloride was added to the solution containing the buffer, preservative and atropine. The pH was adjusted to 5.5 using sodium hydroxide. The volume was made up to 100 % with water for injection. The formulation was filtered through a membrane filter to get the sterile solution. The above solution was filled in an opaque light protective polyethylene plastic bottles.

The solution prepared as per Example I, Composition A was tested for storage stability at room temperature (25°C and 60 % relative humidity) and was found to be physically and chemically stable upon storage. Stability results upon storage at room temperature are given below in Table 2.

Table 2: Results of Stability study at room temperature:

Stability testing of the solution of Example I, Composition A was also carried out at forced degradation condition of 60°C at different time points. The stability study was also carried out at the accelerated stability condition of 40°C/25%RH. Stability results upon storage at different conditions are given below in Table 3. Table 3: Results of Stability:

Similarly, the solution prepared as per Example I, Composition B was tested for storage stability at 20°C and 35% relative humidity and at the accelerated stability condition of 40°C/25%RH. Composition B was found to be physically and chemically stable upon storage. The assay of atropine sulfate was found within the specified limit of 93.0 % - 107.0 %. Further, the levels of impurities (tropic acid, atropic acid, and apotropine) and total impurities were found within the specified limit. Stability results upon storage at room temperature for Composition B are given below in Table 4.

* Clear, colorless solution, filled in LDPE botle, NA: Not Available, ND: Not Detected COMPARATIVE EXAMPLES (la to IV)

Effect of various buffers on the stability of an aqueous sterile solution of Atropine

Sulfate

Ophthalmic solutions of atropine sulfate were prepared using the same procedure as explained in Example I. The compositions were prepared using different buffer systems such as acetate, borate and phosphate as described in comparative Examples II, III and IV and without use of buffers as per comparative Example la.

Table 4: Compositions of Atropine with different buffer system. q.s.: quantity sufficient. The above compositions of comparative examples were filled in opaque light protective polyethylene bottles. Stability testing was carried out at forced degradation condition of 60°C at different time points. The stability study was also carried out at the accelerated stability condition of 40°C/25%RH. The stability results upon storage are disclosed in Table 5 below. Table 5: Stability Results for comparative Examples la to IV From the stability data set forth in Tables 2, 3 and 5, it was surprisingly found that when a citrate buffer consisting of citric acid and sodium citrate was used, there occurs no increase in the tropic acid impurity levels and no levels were detected. In contrast, other buffers as described in comparative Examples II, III and IV surprisingly caused increase in the tropic acid levels. The atropine solution prepared without using any buffer also showed an increased tropic acid level.