DESC:
AN AQUEOUS STERILE SOLUTION OF ATROPINE FOR OPHTHALMIC USE

SUN PHARMACEUTICAL INDUSTRIES LTD.

A company incorporated under the laws of India having their office at SUN HOUSE, 201 B/1, WESTERN EXPRESS HIGHWAY, GOREGOAN (E), MUMBAI-400063 MAHARASHTRA, INDIA.

The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
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 1/5th 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. 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 only when sodium citrate and citric acid are used as buffer, there occurs no substantial increase in the level of tropic acid upon storage. Surprisingly, other buffers such as acetate, borate and phosphate buffer failed to control tropic acid generation. Also, atropine solution prepared without using any buffer failed to control tropic acid generation.
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,
c. purified sterile water
wherein the pH of the solution ranges from 4.5 to 5.5,
wherein 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 container coated with 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 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, such as 3 months or 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 tropic acid is controlled. The level of tropic acid upon storage at 60°C for 28 days or upon storage at the accelerated stability condition of 40°C/25%RH for 1 month is not more than 0.2 % by weight of atropine. In preferred embodiments, the 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. Also, the assay of atropine remains within 93.0 % - 107.0 %, upon storage at room temperature for at least 6 months.
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 essentially of sodium citrate and citric acid,
c. purified sterile water
wherein the pH of the solution ranges from 4.5 to 5.5,
wherein 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 only 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, such as for example, 0.006, 0.065, 0.007, 00075, 0.008, 0.0085, 0.009, 0.0095, 0.01, 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 be selected from but not limited to pH adjusting agent/s, buffer, tonicity adjusting agent and preservative.
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 however 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 5.5 such as for example 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5 or intermediate values thereof. According to preferred embodiments, the pH of the solution is 4.8 ± 0.2, more preferably 4.89 ± 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 are selected from, but 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 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 queous solution at a concentration ranging from 0.05 to 1.5 % w/v such as for example 0.05%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 the citrate buffer consists of citric acid monohydrate and sodium citrate dihydrate. Citric acid monohydrate may be present at a concentration ranging from 0.05 to 0.5 % w/v, preferably at a concentration of 0.1 % to 0.3 % w/v such as for example 0.1 % w/v, 0.15% w/v, 0.2% w/v, 0.25 % w/v or 0.3% w/v and sodium citrate dihydrate may be present at a concentration ranging from 0.2 % to 1.0 % w/v, preferably 0.3 % to 0.8 % w/v such as for example 0.3% w/v, 0.35% w/v,0.4% w/v, 0.45% w/v, 0.5% w/v, 0.55% w/v, 0.6% w/v, 0.65% w/v, 0.7% w/v, 0.75% w/v or 0.8 % w/v.
It has been surprisingly found by the present inventors that only when sodium citrate and citric acid are used as buffer, the generation of tropic acid is effectively controlled and there occurs no substantial increase in the level of tropic acid impurity upon storage. Surprisingly, other buffers such as acetate, borate and phosphate buffer fail to control tropic acid generation. Also, atropine solution prepared without using any kind of buffer too failed in controlling tropic acid generation.
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 include, 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, such as for example 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 butyl- paraben), 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, such as for example 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 choride.
The use of polyhexamethylene biguanide as a preservative has been found to be advantageous over other widely used preservative like benzalkonium chloride because aqueous solution comprising polyhexamethylene biguanide show lower mydriatic action than the solution which comprises benzalkonium chloride. It is noteworthy that mydriatic action which leads to dilatation of pupil is undesirable for the treatment.
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 (DTPA), dimercaptopropane sulfonic acid (DMPS), dimercaptosuccmic acid (DMSA), aminotrimethylene phosphonic acid (ATPA).
In preferred embodiments, the aqueous sterile solution for ophthalmic use according to the present invention is free of water soluble polymers such as 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, such as for example the container being opaque or amber coloured or container coated with light protective coating. The light protective container that may be used include, but is not limited to, opaque polyethylene, polypropylene or low-density polyethylene containers. In preferred embodiment, the aqueous stable solution for ophthalmic use according to the present invention is filled into the 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 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 4.6 to 5.0, polyhexamethylene biguanide as 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,
c. purified water
wherein the pH of the solution is 4.8 ± 0.2,
wherein 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. tonicity adjusting agent consisting essentially of sodium chloride and
e. purified water
wherein the pH of the solution is 4.8 ± 0.2,
wherein 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 0.3 % to 0.8 % w/v and citric acid at a concentration ranging from 0.1 % to 0.3 % w/v,
c. polyhexamethylene biguanide at a concentration ranging from 0.001 % to 0.5 % w/v,
d. tonicity adjusting agent consisting essentially of sodium chloride and
e. purified water
wherein the pH of the solution is 4.8 ± 0.2,
wherein the solution is to be instilled in the eye without dilution or reconstitution.
In 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 0.5 %w/v and citric acid monohydrate at the concentration of 0.2% 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,
wherein the solution is to be instilled in the eye without dilution or reconstitution.
In one embodiment, the present invention provides a process of preparing the aqueous sterile solution for ophthalmic use involving the step 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 4.8±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 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 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 ophthalmic solution according to one preferred embodiment of the present invention.
Table 1: Composition details
Ingredients Amount % w/v
Atropine Sulfate 0.01
Citric acid monohydrate 0.20
Sodium Citrate (dihydrate) 0.50
Polyhexamethylene biguanide hydrochloride 0.005
Sodium chloride 0.75
Water for Injection (purified water) q.s to 100 %
q.s.: quantity sufficient.
Method of preparation: The dispensed quantity of the sodium citrate dihydrate and citric acid monohydrate were dissolved in water for injection. To this buffer solution, dispensed quantity of polyhexamethylene biguanide was added under stirring and dissolved. Further dispensed quantity of atropine sulfate was added in solution containing buffer and preservative. After that dispensed quantity of sodium chloride was added in solution containing 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 membrane filter to get the sterile solution. The above solution was filled in the opaque light protective polyethylene plastic bottles.
The solution prepared as per example 1 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:
Time point Physical Observation % Tropic acid levels
6 month Clear and colorless solution, free of visible particulate matter 0.13
12 months 0.18
Stability testing of solution of example 1 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:
Stability condition Physical Observation % Tropic acid levels
40°C/25%RH for 1 month Clear and colorless solution, free of visible particulate matter Not Detected
60°C for 7 days Not Detected
60°C for 28 days Not Detected

COMPARATIVE EXAMPLES (I to IV)
Effect of buffers on the stability of aqueous sterile solution of Atropine Sulfate
The ophthalmic solution of atropine sulfate was prepared using the same procedure as explained in example 1. The composition was prepared using the different buffer system such as acetate, borate and phosphate as described in comparative example II, III and IV and without use of buffers as per comparative example I.
Table 4- Compositions of Atropine with different buffer system.
Ingredients

Comparative Examples
I II III IV
No Buffer Acetate buffer Phosphate Buffer Borate Buffer
% w/v
Atropine sulfate 0.01
Polyhexamethylene biguanide hydrochloride 0.005

Sodium chloride 0.75
Acetic acid - 0.08 - -
Sodium acetate - 0.153 - -
Dibasic sodium phosphate - - 0.026 -
Monobasic sodium phosphate - - 0.341 -
Boric acid - - - 0.3
Sodium hydroxide or hydrochloric acid q.s to adjust pH to 4.8
Water for Injection (purified water) q.s. to 100 %
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 I to IV
Comparative Example % Tropic acid levels
60°C for 7 days 60°C for 28 days 40°C/25%RH for 1 month
I (Without Buffer) 0.094 0.79 0.12
II (With Acetate buffer) 0.23 0.78 0.14
III (With Phosphate Buffer) 0.15 0.83 0.17
IV (With Borate Buffer) 0.09 0.80 0.17
From the above stability data in table 2, 3 and table 5, it was surprisingly found that only when the citrate buffer consisting of citric acid and sodium citrate was used, there occurs no increase in the tropic acid impurity levels and the levels were not detected. However, other buffers as described in comparative example II, III and IV surprisingly caused increase in the tropic acid levels. The atropine solution prepared without using any buffer also showed increased tropic acid level.
,CLAIMS:Claims:
1. An aqueous sterile solution for ophthalmic use filled in a light protective container, said solution comprising
i. atropine sulfate at a concentration ranging from 0.001 % to 0.05 % w/v,
ii. buffer consisting essentially of sodium citrate and citric acid,
iii. purified water
wherein the pH of the solution ranges from 4.5 to 5.5,
wherein the solution is to be instilled in the eye without dilution or reconstitution.

2. The aqueous sterile solution as claimed in claim 1, wherein atropine sulfate is present at a concentration of 0.01 % w/v.
3. The aqueous sterile solution as claimed in claim 1, wherein the buffer is present at a concentration ranging from 0.05 % to 1.5 % w/v.
4. The aqueous sterile solution as claimed in claim 1, wherein the buffer consists of citric acid monohydrate and sodium citrate dihydrate, further wherein citric acid monohydrate is present at a concentration ranging from 0.1 % to 0.3 % w/v and sodium citrate dihydrate is present at a concentration ranging from 0.3 % to 0.8 % w/v.
5. The aqueous sterile solution as claimed in claim 1, wherein the pH of the solution is 4.89 ± 0.2.
6. The aqueous sterile solution as claimed in claim 1, wherein the light protective container is an opaque polyethylene plastic bottle.
7. The aqueous sterile solution as claimed in claim 1, wherein the solution further comprises polyhexamethylene biguanide at a concentration ranging from 0.002 % to 0.5 % w/v.

8. The aqueous sterile solution as claimed in claim 1, wherein the solution is free of benzalkonium chloride and deuterated water.

Dated this 1st day of February 2021

Dr Vinita Kulkarni
Senior General Manager
Sun Pharmaceutical Industries Limited