FIELD OF THE INVENTION

The present invention relates to pharmaceutical composition comprising levothyroxine or a salt thereof and one or more pharmaceutically acceptable excipient(s).

The present invention also relates to process for preparation of pharmaceutical composition comprising levothyroxine.

The present invention further relates to the use of the pharmaceutical composition of levothyroxine for the treatment of a disease or disorder in a subject in need thereof.

The pharmaceutical compositions comprising levothyroxine are highly stable and are useful . when thyroid replacement is needed on an urgent basis, for short term thyroid replacement, and/or when oral administration is not possible, such as for a patient in a state of myxedema coma.

The present invention further relates to a lyophilized pharmaceutical composition of levothyroxine sodium and process of preparing such composition.

BACKGROUND OF THE INVENTION

Levothyroxine, also known as L-thyroxine, synthetic T4, or 3,5, 3',5'-tetraiodo-L-thyronine, is a synthetic form of thyroxine used as a thyroid hormone replacement therapy in cases of reduced or absent thyroid function, for e.g., ailments such as myxedema, cretinism and obesity.

Thyroid hormones regulate multiple metabolic processes and play an essential role in normal • growth and1 development, and normal maturation of the central nervous system and bone.

Thyroid hormone drugs are natural or synthetic preparations containing tetraiodothyronine (T4,levothyroxine) or triiodothyronine (T3,liothyronine) or both, usually as their pharmaceutically acceptable (e.g., sodium) salts.

T4and.T3. are produced in the. human thyroid gland by the iodination and coupling. of the . . . amino acid tyrosine. T4 contains four iodine atoms and is formed by the coupling of two molecules of diiodotyrosine (DIT).T3 contains three atoms of iodine and is formed by the coupling of one molecule of DIT with one molecule of monoiodotyrosine (MIT). Both hormones are .stored in the thyroid colloid as thyroglobulin. Thyroid hormone preparations belong to two categories: (1) natural.hormonal preparations derived from animal thyroid, and (2) synthetic preparations. Natural preparations include desiccated thyroid and thyroglobulin

Thyroid hormones are believed to exert their physiologic actions through control of DNA transcription and protein synthesis. It is presently believed that the T3 and T4 hormones diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex then activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. The physiological actions of thyroid hormones are believed to be produced predominantly by T3, approximately 80% of which is derived from T4 by deiodination in peripheral tissues.

T4 has higher serum levels, slower metabolic clearance, and a longer half-life than T3, which may be due to the higher affinity of serum proteins for T4 compared to T3.

A patient who has had their thyroid gland removed, or whose thyroid gland functions at an undesirably low level (hypothyroidism), may be treated by administration of a daily maintenance dose of 50-100 micrograms (fig) of levothyroxine sodium. A patient in need of additional intervention may be treated by administration of an initial dose of 200-500 u.g or 300-500 jig of levothyroxine sodium and/or with a 2nd day dose of 100-300 \xg of levothyroxine sodium.
Levothyroxine sodium was initially manufactured as synthetic T4 in 1958 and it was first '"'■ introduced into the maYker as early as before 1962 without an approved NDA, apparently in ; ": the belief that it was not a new drug.

Levothyroxine sodium for injection is a sterile lyophilized product for parenteral administration of levothyroxine sodium for thyroid replacement therapy. Levothyroxine sodium for injection is particularly useful when thyroid replacement is needed on an urgent

basis, for. short term thyroid replacement, and/or when oral administration is not possible, . - such as for a patient in a state of myxedema coma.

Conventional formulations of levothyroxine sodium for injection (Synthroid^ are
preservative-free lyophilized powders containing synthetic crystalline levothyroxine sodium
and the excipients mannitol, tribasic sodium phosphate, and sodium hydroxide. These
conventional formulations typically contain 10 milligrams (mg) of mannitol, 700 jig of
tribasic sodium phosphate, and either 200 jig or 500 u.g of levothyroxine sodium.

Administration of the conventional formulation involves reconstitution of the lyophilized
powder in 5 milliliters (ml) of 0.9% sodium chloride injection (USP), to provide injectable
solutions having levothyroxine sodium concentrations of 40 micrograms per milliliter (ug/ml)
or 100 u.g/ml respectively.

Fresenius Kabi USA has launched improved formulations of levothyroxine sodium for injection on June 24, 2011. Fresenius product is a sterile, preservative-free lyophilized powder consisting of the active ingredient, levothyroxine sodium, and the excipients dibasic sodium phosphate heptahydrate, USP; 3 mg of mannitol, USP; and sodium hydroxide, NF in . single-use amber glass vials. Levothyroxine Sodium for Injection is available in two dosage strengths: 100 meg per vial and 500 meg per vial.

U.S. Patent No. 9,006,289 describes a composition comprising levothyroxine sodium; a phosphate buffer; and from 2 to 4 milligrams of mannitol, where the composition is a lyophilized solid.

There still exists an unmet need for pharmaceutical compositions of levothyroxine sodium which have improved stability over the compositions known to the art.
Surprisingly; the inventors of the present invention have- developed highly stable
compositions of levothyroxine sodium which are convenient to store, to reconstitute, and to
administer to a patient. . .

SUMMARY OF THE INVENTION
Aspects of the present invention relates to pharmaceutical composition comprising levothyroxine or a salt thereof and one or more pharmaceutically acceptable excipient(s).
Aspects of the present invention further relate to lyophilized pharmaceutical composition of levothyroxine sodium and process of preparation of such composition.
An aspect of the present invention relates to a composition comprising levothyroxine or a salt thereof; a buffer; about 2 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipieht(s).
An aspect of the present invention relates to a lyophilized solid composition comprising levothyroxine sodium; a buffer; about 2 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipient(s). '
An aspect of the present invention relates to a lyophilized solid composition comprising levothyroxine sodium; a buffer other than a phosphate buffer; about 2 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipient(s).
Aspects of the present invention also relates to process for preparation of pharmaceutical composition comprising levothyroxine.
Aspects of the present invention further relates to the use of the pharmaceutical composition of levothyroxine for the treatment of a disease or disorder in a subject in need thereof.
Aspects of the present invention further relates to pharmaceutical compositions comprising levothyroxine that are highly stable and are useful when thyroid replacement is needed on an urgent basis, for short term thyroid replacement, and/or when oral administration is not possible, such as for a patient in a state of myxedema coma.
Aspects of the present invention also relates to a method of using the lyophilized pharmaceutical composition of levothyroxine sodium for treatment of myxedema coma.

DETALIED DESCRIPTION OF THE INVENTION
The present invention provides pharmaceutical composition comprising levothyroxine or a salt thereof and one or more pharmaceutically acceptable excipient(s).
In an embodiment, the present invention provides lyophilized pharmaceutical composition of levothyroxine sodium and process of preparation of such composition.
In an embodiment, the present invention provides a composition comprising levothyroxine or a salt thereof; a buffer; about 2 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipient(s).
In another embodiment, the present invention provides lyophilized solid composition comprising levothyroxine sodium; a buffer; about 2 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipient(s).
In another embodiment, the present invention provides lyophilized solid composition comprising levothyroxine sodium; a buffer; about 5 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipient(s).
In an embodiment, the present invention provides a lyophilized solid composition comprising levothyroxine sodium; a buffer other than a phosphate buffer; about 2 to about 150 milligrams of mannitol, and optionally one or more other pharmaceutically acceptable excipient(s).
In an embodiment, the present invention provides a composition comprising levothyroxine
sodium, a buffer arid a bulking ageJht, wherein the composition is a lyophilized solid and "free'
from phosphate buffer.
In an embodiment, the present invention provides a composition comprising levothyroxine sodium, a buffer, bulking agent, and a base for adjusting the pH, wherein the composition is a lyophilized solid and free from phosphate buffer.

In an embodiment, the present. invention provides a composition comprising levothyroxine sodium; a buffer selected from a group comprising sodium bicarbonate, tromethamine, diethanolamine, trisodium citrate, and mixtures thereof; about 2 to about 150 milligrams of mannitol; and a base for adjusting the pH, wherein the composition is a lyophilized solid and free from phosphate buffer.
A solid composition that includes levothyroxine sodium and mannitol may include from about 25 to 1,000 ug levothyroxine sodium. Preferably, the composition includes from about 50 to about 750 jig levothyroxine sodium or from about 100 to 500 ug levothyroxine sodium. The amount of levothyroxine sodium in the composition may be an amount sufficient for a single initial dose of levothyroxine sodium, an amount sufficient for a single 2n day dose of levothyroxine sodium, and/or an amount sufficient for a daily maintenance dose of levothyroxine sodium. The amount of levothyroxine sodium in the composition may be a different therapeutic amount. For example, the amount of levothyroxine sodium in the composition may be an amount sufficient for half of a single initial dose, half of a single 2nd day dose, or half of a daily maintenance dose.
In an embodiment, the pharmaceutical composition of the present invention contains about 100 jig or about 200 ug or about 500 ug of levothyroxine sodium.
In embodiments of the present invention, the composition that includes levothyroxine sodium
and mannitol may also include one or more other excipient(s)/substances. Non-limiting
examples of other excipients include buffers, stabilizers, solubilizers, preservatives,
antioxidants, tonicity contributors, and the like. Substances that may be useful in formulating
pharmaceutically acceptable compositions, and methods of forming such compositions, are
described, for example, in Remington: The Science and Practice of Pharmacy, 20th Ed., ed.
A. Gennaro, Lippincott Williams & Wilkins, 2000, and in Kibbe, "Handbook • of
Pharmaceutical Excipients"3'Edition, 2000
In an embodiment, the present invention provides process for preparation of pharmaceutical composition comprising levothyroxine.
In an embodiment, the present invention provides a process for producing a lyophilized pharmaceutical composition of levothyroxine _ sodium comprising the steps of forming a

liquid mixture by .combining .levothyroxine sodium, bulking agent, buffer and water; and lyophilizing the liquid mixture.
In an embodiment, the process for. forming a liquid mixture comprises combining levothyroxine sodium; from about 2,to about 4 milligrams of mannitol; buffer selected from group comprising sodium bicarbonate, tromethamine or diethanolamine or trisodium citrate; and solvent.
In an embodiment, the ingredients used to form the compositions of the present invention may include a buffer selected from a group comprising sodium bicarbonate, tromethamine, diethanolamine, trisodium citrate, and mixtures thereof.
An effective amount of buffer for lyophilized compositions of the present invention is the amount required to maintain desired pH of the compositions throughout the product shelf life. The effective amount of buffer depends upon the type of buffer and its buffering capacity, which is well known to a person skilled in art.
In an embodiment, forming the liquid mixture for use in preparing the solid composition may further include adding a base to the liquid mixture to provide a desired pH in the mixture, wherein the base is different from any buffer(s) present in the composition. The amount of the base added to the liquid mixture may be an amount sufficient to provide a liquid mixture pH in the range of about 8 to about 12, or from about 9 to about 11. The liquid mixture is lyophilized to obtain a solid composition, and the said solid composition is reconstituted in a suitable recoristitution fluid such as 5 mL of 0.9% aqueous sodium chloride (USP) preferably prior to administration. In an embodiment, the base is selected from a group comprising sodium hydroxide, potassium hydroxide, and the like.
In an embodiment, the present invention provides a composition comprising levothyroxine ■"'' sodium; a buffer; and 3 milligrams of mannitol, wherein the composition is a lyophilized solid and free from phosphate buffer.
A solid composition that includes levothyroxine sodium and mannitol may include from about 25 jig to less than about 10 mg mannitol. In an embodiment, the composition includes

from about 0.1 to about 7 mg mannitql, or about 1.-5 mg.mannitol, or about 2-4 mg mannitol, or about 2.9-3.1 mg mannitol.
In one embodiment, the present invention provides a composition comprising levothyroxine sodium; a phosphate buffer; and from about 5 mg to about 100 mg of mannitol, wherein the composition is a lyophilized solid.
In an embodiment, the buffer is selected from a group comprising monobasic sodium phosphate anhydrous, dibasic sodium phosphate heptahydrate, tribasic sodium phosphate anhydrous, and combinations thereof.
In another embodiment, the present invention provides a process for producing a lyophilized pharmaceutical composition containing levothyroxine sodium, wherein the said process comprises the following steps: (i) forming a liquid mixture by combining levothyroxine sodium, about 5-150 milligrams of
mannitol, buffer, solvent, and optionally one or more other excipient(s), and (ii) lyophilizing the liquid mixture to obtain the desired product.
In one embodiment, the present invention provides a composition comprising levothyroxine sodium; a buffer; and a bulking agent which is mannitol, lactose, dextrose or sorbitol; and wherein the composition is a lyophilized solid.
The amount of levothyroxine sodium is about 100 jug to about 500 |ig. The buffer is selected from phosphate buffer, sodium bicarbonate, tromethamine or diethanolamine or trisodium citrate dihydrate.
In a specific embodiment, the present-invention provides a composition comprising 100 jig or ! 200 jig or 500 \ig of levothyroxine st>dium, about 3 mg: of mannitol and about 2.46 mg of trisodium citrate dihydrate.
In another embodiment, the present invention provides a process for producing a lyophilized pharmaceutical composition containing levothyroxine sodium, wherein the said process comprises of the following steps:

, (i).. forming a.liquid mixture by combining levothyroxine sodium; bulking agent which is lactose, dextrose or sorbitol; buffer which is phosphate, sodium bicarbonate, tromethamine or diethanolamine or trisodium citrate dehydrate; and solvent, and (ii) lyophilizing the liquid mixture.
In a specific embodiment, the present invention provides a process for producing a lyophilized pharmaceutical composition containing levothyroxine sodium, wherein the said process comprises of the following steps: (iii) forming a liquid mixture by combining levothyroxine sodium, mannitol, trisodium
citrate dihydrate and solvent, and (iv) lyophilizing the liquid mixture.
In an embodiment, a liquid mixture may be formed by adding the levothyroxine sodium and mannitol to a container including the solvent, and then adding a buffer and/or a base to achieve the desired pH in the liquid mixture. In a further embodiment, the liquid mixture has a pH of about 8-.12.
The solvent in the liquid mixture may include water and/or an organic solvent.
If the solvent includes an organic solvent, the organic solvent preferably is miscible with ' water. Non-limiting examples of organic solvents that are miscible with water and may be present in the solvent include alcohols such as ethanol, isopropanol, and t-butanol. The concentration of organic solvent, if present, may be from about 0.5 to 20 percent by volume (vol %) or from 2 to 10 vol % of the solvent. The liquid mixture may include from about 0.1 to about 5 ml solvent. In an embodiment, the liquid mixture includes from about 0.5 to 2 ml . solvent or from about 0.75 to about 1.5 ml solvent.
In an embodiment'of the present, invention, the lyophilizatioff may include freeze^drying the"' liquid mixture to provide a solid composition. Freeze-drying of the liquid mixture may include maintaining the liquid mixture in an inert atmosphere, such as nitrogen or argon. Preferably the liquid mixture is placed in glass vials prior to lyophilization, and the amount of the liquid mixture in each vial is based on the amount of levothyroxine intended to be present in the final solid composition in the vial.

In a typical lyophilization process^ the temperature of the liquid mixture is lowered .to..a . temperature at or below the solidification point of the liguid mixture. If the liquid mixture forms a glass when cooled, the solidification point typically is the glass transition temperature. If the liquid mixture forms crystals when cooled, the solidification point typically is the eutectic point. The solidified mixture is then dried under vacuum. Typically, the drying process includes a primary drying step in which the temperature of the solidified mixture is raised gradually while most of the water is removed from the mixture by the vacuum, and a secondary drying step in which the temperature of the solidified mixture is raised further while residual moisture is removed from the mixture by the vacuum. The temperature is kept at or below the desired storage temperature for the final solid composition. Lyophilization typically is complete within 48 hours, but may require additional time. The solid composition resulting from the lyophilization typically is sealed for later use. Details regarding the lyophilization process may be found, for example, in Remington: The Science and Practice of Pharmacy, 20th Ed., ed. A. Gennaro, Lippincott Williams & Wilkins, 2000.
The lyophilized solid composition of the present invention may be stored for later reconstitution and administration. The solid composition is stored at a temperature of about 10°C to 40°C, or from about 15°C to 35°C, or from about 20°C to 30°C, or about 25°C. Preferably the solid composition is protected from light, such as by storing the composition in an opaque or tinted container, such as an amber tinted container. Preferably the solid composition is sealed in a glass vial to protect the composition from moisture in the surrounding environment. In an embodiment, the containers include amber tinted glass vials. The packaging may contain a desiccant or an oxygen scavenger.
A solid composition that includes levothyroxine sodium and bulking agent may be administered to a patient by combining the composition with an aqueous carrier liquid to form an aqueous mixture, and administering.the aqueous mixture into the patient by for ' example, injection. Preferably, the aqueous carrier liquid is a pharmaceutical acceptable carrier liquid.
Non-limiting examples of pharmaceutically acceptable carrier liquids include water.and saline, such as phosphate buffered saline (PBS), Ringers solution or lactated Ringers injection. The aqueous carrier liquid also may include, fixed oils, fatty esters or polyols,

Particularly if the aqueous mixture for injection is a suspension. The aqueous carrier liquid also may include one or more other substances such as buffers, stabilizers, solubilizers, preservatives and antioxidants. Preferably the solid composition dissolves in the aqueous carrier liquid to form a solution. Presently preferred aqueous carrier liquids include sodium chloride injection, such as solutions containing 0.9% or 0.45% or 0.225% sodium chloride.
In an embodiment, the aqueous carrier liquids include 0.9% sodium chloride injection or 0.9% sodium chloride injection USP containing benzyl alcohol, and bacteriostatic sodium chloride injection.
The amount of aqueous carrier liquid may be sufficient to provide an aqueous mixture containing levothyroxine sodium at a concentration of from about 5 to 500 jig/ml. Preferably the concentration of levothyroxine-sodium in the aqueous mixture is from about 10 to 200 jig/ml, or from about 20 to 100 ug/mL In an embodiment, the concentration of levothyroxine sodium in an aqueous mixture for injection is about 20 ug/ml, or 40 ug/ml or 100 (ig/ml.
An aqueous mixture formed from the solid composition may be administered to provide an initial dose of 200-500 ug or of 300-500 u.g of levothyroxine sodium to a patient. An aqueous mixture formed from the solid composition may be administered to provide a 2 day dose of 100-300 ug of levothyroxine sodium to a patient. An aqueous mixture formed from the solid composition may be administered to provide a daily dose of 50-100 (ig of levothyroxine sodium to a patient. Doses outside of these ranges also may be administered.
In a further embodiment, the present invention provides the use of the pharmaceutical composition of levothyroxine for the treatment of a disease or disorder in a subject in need thereof.
In a further embodiment the present invention provides pharmaceutical compositions comprising levothyroxine that are highly stable and are useful when thyroid replacement is needed on an urgent basis, for short term thyroid replacement, and/or when oral administration is not possible, such as for a patient in a state of myxedema coma.

. The present invention, will now be described with reference, to the following non-limiting examples which are for illustrative purposes only and does not limit the scope of the invention in any manner whatsoever.

The composition is prepared by forming a liquid mixture by combining levothyroxine sodium, mannitol, buffer (sodium bicarbonate or tromethamine or diethanolamine or trisodium citrate dihydrate), and a solvent comprising water; and lyophilizing the liquid mixture. The solvent, levothyroxine sodium, mannitol, buffer, optional a base and one or more other optional substances may be combined in any order when forming the liquid mixture. For example, a liquid mixture may be formed by adding the levothyroxine sodium and mannitol to a container including the solvent, and then adding a buffer and/or a base to achieve the desired pH in the liquid mixture. The liquid mixture preferably has a pH of from about 9-11.


The composition is prepared.by forming a liquid mixture by combining levothyroxine sodium, mannitol, dibasic sodium phosphate heptahydrate, and a solvent comprising water; . and lyophilizing the liquid mixture. The solvent, levothyroxine sodium, mannitol, buffer, optional base and one or more other optional substances may be combined in any order when forming the liquid mixture. For example, a liquid mixture may be formed by adding the levothyroxine sodium and mannitol to a container including the solvent, and then adding a buffer and/or a base to achieve the desired pH in the liquid mixture. The liquid mixture preferably has a pH of from about 10-11.

The composition. is prepared.by forming a liquid mixture by combining levothyroxine sodium, bulking agent (lactose, dextrose or sorbitol), a buffer (monobasic sodium phosphate anhydrous or dibasic sodium phosphate heptahydrate or sodium bicarbonate) and a solvent comprising water; and lyophilizing the liquid mixture. The solvent, levothyroxine sodium, mannitol, buffer, optional base and. one or more other optional substances may be combined in any order when forming the liquid mixture. For example, a liquid mixture may be formed by adding the levothyroxine sodium and mannitol to a container including the solvent, and

then adding a.buffer, and/or a base to achieve the desired pH in the liquid mixture. The liquid mixture preferably has a pH of from 10-11.
The compositions of the present invention descried in the examples are highly stable and have a better shelf-life when. compared to conventional levothyroxine formulations for injection known to the art.
While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible within the scope of the invention.

We Claim:
1. A composition comprising levothyroxine or a salt thereof, a buffer other than phosphate buffer and from 2 to 100 milligrams of mannitol, wherein the composition is in a lyophilized form.
2. The composition of claim 1, comprising levothyroxine sodium in an amount of about 100 micrograms to about 500 micrograms.
3. The composition of claim 1, wherein the buffer is selected from sodium bicarbonate, tromethamine, diethanolamine, trisodium citrate dihydrate and combinations thereof
4. The composition of claim 1, comprising about 100 or about 200 or about 500 micrograms of levothyroxine sodium, about 3 milligrams of mannitol and trisodium citrate dehydrate.
5. The composition of claim 1, comprising about 100 or about 200 or about 500 micrograms of levothyroxine sodium, about 3 milligrams of mannitol and from about 2 to about 5 milligrams of trisodium citrate dihydrate.

6. The composition of claim 1, comprising levothyroxine sodium and from 5 to 100 milligrams of mannitol.
7. The composition of claim 1, wherein the buffer is selected from monobasic sodium phosphate anhydrous, dibasic sodium phosphate heptahydrate, tribasic sodium phosphate anhydrous, sodium bicarbonate and combinations thereof.
8. The composition of claim 1, comprising a bulking agent selected from lactose, dextrose, sorbitol and combinations thereof.
9. Process of preparation of a composition according to claim T, wherein the said process comprises of the following steps:
(i) forming a liquid mixture comprising levothyroxine sodium, mannitol, buffer and
solvent, and
(ii) lyophilizing the liquid mixture.

10. The pharmaceutical composition of levothyroxine according to claim 1, which is useful.. . for the treatment of a disease or disorder in a subject in need thereof