DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003

COMPLETE SPECIFICATION
(Section 10 and Rule 13)

VASOPRESSIN FORMULATIONS FOR PARENTERAL USE

AUROBINDO PHARMA LTD HAVING CORPORATE OFFICE AT
THE WATER MARK BUILDING,
PLOT NO. 11, SURVEY NO. 9,
HITECH CITY, KONDAPUR,
HYDERABAD - 500 084,
TELANGANA, INDIA
AN INDIAN ORGANIZATION

The following specification particularly describes the invention and the manner which it is to be performed:
FIELD OF THE INVENTION

The present invention relates to a stable injectable formulation for administration to a patient comprising a biologically active peptide i.e. Vasopressin, a buffering agent, optionally a preservative and water. The present invention also relates to processes for preparation of such stable formulation of Vasopressin and methods of using such formulations for treating sepsis and cardiac conditions, and in the elevation of patients suffering from low blood pressure.

BACKGROUND OF THE INVENTION

VasopressinCyclo [(1-6) L-Cysteinyl-L-Tyrosyl-L-Phenylalanyl-LGlutaminyl-L-Asparaginyl-L-Cysteinyl-L-Prolyl-L-Arginyl-L- Glycinamide] is a potent endogenous hormone, responsible for maintaining plasma osmolality and volume in most mammals. Vasopressin can be used clinically in the treatment of sepsis and cardiac conditions, and in the elevation of patients suffering from low blood pressure. Vasopressin is structurally represented as:

Vasopressin has two basic groups, the N-terminal cysteine, and the arginine at position eight, that at neutral to acidic pH are protonated and can each carry an acetate counterion. The amide groups of the N-terminal glycine, the glutamine at position four, and the asparagine at position five, are susceptible to modification when stored as unit dosage forms. The glycine, glutamine, and asparagine residues can undergo deamidation to yield the parent carboxylic acid and several degradation products. Deamidation of asparagine and glutamine residues can occur in vitro and in vivo, and can lead to perturbation of the structure and function of the affected proteins. The susceptibility to deamidation can depend on primary sequence of the protein, three-dimensional structure of the protein, and solution properties including, for example, pH, temperature, ionic strength, and buffer ions. Deamidation can be catalyzed by acidic conditions. Under physiological conditions, deamidation of asparagine occurs via the formation of a five-membered succinimide ring intermediate by a nucleophilic attack of the nitrogen atom in the following peptide bond on the carbonyl group of the asparagine side chain. Vasopressin can also form dimers in solution and in vivo. The Vasopressin dimers can occur through the formation of disulfide bridges that bind a pair of Vasopressin monomers together. The dimers can form between two parallel or anti-parallel chains of Vasopressin. Given the delicate stability of Vasopressin, there is a need to develop a stable formulation at different conditions.

Vasopressin injection 20U/ml & 200U/10ml were approved by US FDA under the brand name “Vasostrict”and indicated to increase blood pressure in adults with vasodilatory shock (e.g., post-cardiotomy or sepsis) who remain hypotensive despite fluids and catecholamines. The goal of treatment with Vasopressin is to optimize the perfusion to critical organs like the gastrointestinal tract, whose function is difficult to monitor. In general, Vasopressin should be titrated to the lowest dose compatible with a clinically acceptable response. For post-cardiotomy shock, the start dose is 0.03 units/minute and maximum dose is 0.1 units/minute. For septic shock, start dose is 0.01 units/minute and maximum dose is 0.07 units/minute. If the target blood pressure response is not achieved, titrating up by 0.005 units/minute at 10- to 15-minute intervals is required. After target blood pressure has been maintained for 8 hours without the use of catecholamines, tapering of Vasopressin by 0.005 units/minute every hour as tolerated to maintain target blood pressure is necessary. In view of the complex dosage regimen, a stable multi use dosage form is required.

Considering the complexity in the dosage regimen and delicate stability of Vasopressin, there is a need for development of pharmaceutical formulations of Vasopressin which have long term and improved stability at different conditions. US Patent No. 9375478 discloses a method of increasing blood pressure in a hypotensive human, wherein the method comprises an intravenous administration of a unit dosage form having a pH of 3.8 and consisting essentially of: a) Vasopressin (0.01 mg/mL to 0.07 mg/mL); b) 10 mM acetate buffer; and c) water. US Patent No. 9687526 discloses a method of increasing blood pressure in a hypotensive human, wherein the method comprises an intravenous administration of composition comprising i) Vasopressin (0.01 mg/mL to 0.07 mg/mL); ii) acetic acid; and iii) water and this pharmaceutical composition has a pH of 3.8; and exhibits less than about 5% degradation after storage at 2-8° C. for about four weeks. US9744239 discloses a method of increasing blood pressure in a hypotensive human, the method comprises providing a intravenous composition having a pH of 3.5 to 4.1 and consisting of i) Vasopressin (0.01 mg/mL to 0.07 mg/mL); ii) optionally chlorobutanol; iii) acetic acid, acetate, or a combination thereof; iv) 0-2% Vasopressin degradation products; and v) water. US Patent No. 9750785 discloses a unit dosage form that has a pH of 3.7-3.9 and composition comprising Vasopressin (0.01 mg/mL to 0.07 mg/mL) and impurities (0.9% to 1.7%), wherein the impurities have from about 85% to about 100% sequence homology to SEQ ID NO.: 1, and wherein the unit dosage form. Further US Patent No. 9744209 discloses a method of increasing blood pressure in a hypotensive human using the composition covered in US 9750785 patent.

US Patent No. 5482931A discloses stabilized aqueous pharmaceutical compositions for nasal, oral or parenteral administration of small and medium-size peptides (up to about eicosapeptides), such as desmopressin (1-deamino-8-D-arginine Vasopressin; DDAVP). US Publication No. 20110237508A1 discloses an aqueous formulation comprising a therapeutically effective amount of oxytocin, Vasopressin or an analogue thereof, a buffer and at least one non-toxic source of divalent metal ion. US Publication No. 20030216302A1 discloses stable aqueous composition comprising desmopressin or its other pharmaceutically acceptable salts in a pharmaceutically acceptable carrier, wherein the carrier comprises a buffering agent, a parahydroxybenzoate preservative and a cosolvent.
The therapeutically activity of Vasopressin is often extremely high and very small amounts of peptide are needed, hence dilutions are required. Such dilute aqueous peptide solutions in general are not stable at room temperature for longer periods, even if kept in sealed containers. Its aqueous solution has to be stored at a temperature not exceeding 8º C. The Label of Vasopressin injection, solution of Fresenius Kabi discloses a composition, wherein Each mL contains: 20 USPVasopressin units; chlorobutanol (anhydrous) 5 mg as preservative; Water for Injection q.s. Glacial acetic acid and/or sodium hydroxide for pH adjustment (2.5 - 4.5). However this formulation was not approved by FDA, due to lack of sufficient safety and efficacy data. The label of VASOSTRICT shows that the product requires refrigeration and as an unopened product it is stable at specific temperature (20° to 25°C) for 12 months and it is further stable for only 30 days after opening the vial. Further, it is known from the cited prior arts that storage at higher temperatures such as, for instance, at room temperature results in the degradation of Vasopressin by hydrolytic and/or oxidative processes which are not blocked by the addition of a preservative, such as chlorobutanol (1,1,1-trichloro-2-methylpropan-2-ol).

The aforementioned prior arts formulations of Vasopressin are stable for a less period and require refrigeration for maintenance or reconstitution of lyophilized powders due to Vasopressin's poor long-term stability. Accordingly, a need exists to develop more efficient pharmaceutical formulationscomprisingVasopressin which has improved stability than the prior art formulationsand providing advantages of longer shelf life. The present inventors have discovered an injectable formulation of Vasopressin which is stable for significant time and at different temperatures/conditions, wherein the formulation comprises of alternate buffering agents, optionally preservatives and water. The alternate buffers used in the present invention stabilizes or maintains the pH of the formulation between about 3.0 and 4.5 and alleviates the limitations in the art by providing better stable Vasopressin injectable preparations with decreased degradation and lesser amount of impurities. Another object of the present invention is to provide a stabilized aqueous formulation containing a Vasopressin for parenteral administration which is cost effective and can be conveniently stored at room temperature for extended periods of time.

SUMMARY OF INVENTION

Aspects of the present invention relate to a stable injectable formulation of Vasopressin comprising buffering agents that stabilizes or maintains the pH of the formulation, optionally a preservative and water for injection.

Aspects of the present invention relate to a pharmaceutical formulation comprising Vasopressin, buffering agents that stabilizes or maintains the pH of the formulation, optionally a preservative and water, wherein the pharmaceutical formulation is having an acidic pH and exhibits less than about 7% degradation after storage at different temperatures/conditions and time periods.

Aspects of the present invention relate to a pharmaceutical formulation comprising Vasopressin, buffering agents that stabilizes or maintains the pH of the formulation, stabilizing excipient, optionally a preservative and water, wherein the pharmaceutical formulation is having an acidic pH and exhibits less than about 7% degradation after storage at different temperatures/conditions and time periods.

Aspects of the present invention relate to a pharmaceutical formulation in a unit dosage form having acidic pH, for administration after dilution with a diluent, wherein the formulation comprises of Vasopressin, buffering agents, optionally preservative and water and wherein the formulation has 0-7% Vasopressin degradation products.

Aspects of the present invention relate to a Vasopressin formulation in a unit dosage form, wherein the unit dosage form further comprises impurities (0.5% to 1.7%) and these impurities have from about 85% to about 100% sequence homology to SEQ ID NO.: 1

Aspects of the present invention relate to a method of increasing blood pressure by administering a stable unit dosage form, wherein the unit dosage form has an acidic pH and comprises of Vasopressin, buffering agents, optionally a preservative and water for injection.

Aspects of the present invention relate to, a method of increasing blood pressure by a) providing a pharmaceutical formulation, that has an acidic pH, comprising: vasopressin, buffer, optionally a preservative and water, b) storing the pharmaceutical formulation at different conditions and time periods; and c) administering the pharmaceutical formulation that exhibits less than about 7% degradation after storage.

In an aspect of the present invention, the buffering agents stabilizes or maintains the pH of the Vasopressin formulation between about 3.0 and 4.5, where in the preferred buffering agents are selected from potassium phosphate, sodium phosphate, saline sodium citrate buffer (SSC), Lactic acid, Monobasic sodium phosphate monohydrate, Dibasic sodium phosphate anhydrous, Trisodium citrate dehydrate, Citric acid monohydrate, Sodium acetate, Acetic acid, citric acid, Phosphoric acid Lactic acid, acetate, saline, physiological saline, phosphate buffer saline (PBS), 4-2-hydroxyethyl-1-piperazineethanesulfonic acid buffer (HEPES), 3-(N-morpholino)propanesulfonic acid buffer (MOPS), and piperazine-N,N'-bis (2-ethanesulfonic acid) buffer (PIPES), or combinations thereof. More preferably Phosphate buffer, Acetic acid, 10mM citrate buffer, 1mM citrate buffer and higher concentration of acetate buffer (50 mM) buffer and mixtures thereof.

An another aspect of the present invention relates to a stable Vasopressin injectable formulation obtained by a simple process with suitable pharmaceutical excipients, comprising of Vasopressin or an pharmaceutically acceptable salt thereof as an active ingredient in an effective therapeutic amount and suitable excipients, characterized in that said formulation comprises of buffering agents which are preferably selected from Acetic acid, citric acid, sodium citrate, Phosphoric acid, sodium phosphate, Lactic acid, acetate buffer and mixtures thereof, optionally preservative and Water for Injection.

Aspects of the present invention also relate to stable Vasopressin injectable formulation having improved stability for extended periods of time and the formulation further comprises total impurities that are present in an amount of 1.0% - 6.73% by Initial Related Substances.

DETAILED DESCRIPTION OF THE INVENTION

Within the scope of the description of the invention, Vasopressin and any of its addition salts are referred to as "Vasopressin". Also, unless otherwise stated, the terms "active ingredient" and "active substance" refer to Vasopressin and any of its pharmaceutically salts. The effective therapeutic amount of active principle is advantageously such that the unit content of Vasopressin and it pharmaceutically acceptable salts is from about 0.01 mg/mL to about 0.07 mg/mL, preferably 20 units/mL in a single dose vial and 200 units/10 mL (20 units/mL) in a multiple dose vial. When the active principle is a Vasopressin pharmaceutically acceptable salt, the salt content in the formulation is such that the latter comprises from 0.001 to 0.5 mg/ml of Vasopressin base.

In embodiments, the pharmaceutical formulation provided herein comprises buffering agents. Certain non-limiting examples of buffering agents include potassium phosphate, sodium phosphate, saline sodium citrate buffer (SSC), Lactic acid, Monobasic sodiumphosphate monohydrate, Dibasic sodium phosphate anhydrous, Trisodium citrate dehydrate, Citric acid monohydrate, Sodium acetate, Acetic acid, citric acid, Phosphoric acidLactic acid, acetate, saline, physiological saline, phosphate buffer saline (PBS), 4-2-hydroxyethyl-1-piperazineethanesulfonic acid buffer (HEPES), 3-(N-morpholino) propanesulfonic acid buffer (MOPS), and piperazine-N,N'-bis (2-ethanesulfonic acid) buffer (PIPES), or combinations thereof. More preferably Phosphate buffer, Acetic acid, 10mM citrate buffer, 1mM citrate buffer and higher concentration of acetate buffer (50 mM)buffer and mixtures thereof.

In embodiments, the stabilized formulation of the present invention has a pH of between about 3.0 to about 4.5. More preferably the pH is 3.0 to 4.0 and further the suitable pH-adjusting agent that can be used in the stabilized aqueous formulation of the present invention is selected from but not limited to a group comprising hydrochloric acid, sodium hydroxide, acetic acid, phosphoric acid, Lactic acid, and mixtures thereof.

In embodiments, optionally preservative can be added to the stabilized formulation in order to inhibit the growth of microbial contaminants and suppress biodegradation. Suitable preservative is selected from but not limited to a group comprising benzalkoniumchloride, benzethonium chloride, chlorhexidine gluconate, chlorobutanol, benzyl alcohol, sodium dehydroacetate, p-hydroxybenzoate, and the like, and mixtures thereof. In certain embodiments of the present invention, the stabilized formulation of present invention can be administered parenterally such as, intravenously, intramuscularly, intraperitonealy, subcutaneously, or via an implantable pump.

In embodiments, the pharmaceutical formulation provided herein further comprises other excipients to improve stability such as sugars. Non-limiting examples of excipients include trehalose, sucrose, glucose, lactose, galactose, glyceraldehyde, fructose, dextrose, maltose, xylose, mannose, maltodextrin, starch, cellulose, lactulose, cellobiose, mannobiose, 0.9% Sodium chloride, Dextran-40 in 0.9% Sodium chloride, Mannitol and combinations thereof.

In embodiments, Pharmaceutical formulations of the invention can be formulated in any suitable volume, which can be, about 0.1 mL to about 30 mL. Preferably the fill volume can be about 0.1 mL, about 0.2 mL, about 0.3 mL, about 0.4 mL, about 0.5 mL, about 0.6 mL, about 0.7 mL, about 0.8 mL, about 0.9 mL, about 1 mL, about 1.1 mL, about 1.2 mL, about 1.3 mL, about 1.4 mL, about 1.5 mL, about 1.6 mL, about 1.7 mL, about 1.8 mL, about 1.9 mL, about 2 mL, about 2.1 mL, about 2.2 mL, about 2.3 mL, about 2.4 mL, about 2.5 mL, about 2.6 mL, about 2.7 mL, about 2.8 mL, about 2.9 mL, about 3 mL, about 3.1 mL, about 3.2 mL, about 3.3 mL, about 3.4 mL, about 3.5 mL, about 3.6 mL, about 3.7 mL, about 3.8 mL, about 3.9 mL, about 4 mL, about 4.1 mL, about 4.2 mL, about 4.3 mL, about 4.4 mL, about 4.5 mL, about 4.6 mL, about 4.7 mL, about 4.8 mL, about 4.9 mL, about 5 mL, about 5.1 mL, about 5.2 mL, about 5.3 mL, about 5.4 mL, about 5.5 mL, about 5.6 mL, about 5.7 mL, about 5.8 mL, about 5.9 mL, about 6 mL, about 6.1 mL, about 6.2 mL, about 6.3 mL, about 6.4 mL, about 6.5 mL, about 6.6 mL, about 6.7 mL, about 6.8 mL, about 6.9 mL, about 7 mL, about 7.1 mL, about 7.2 mL, about 7.3 mL, about 7.4 mL, about 7.5 mL, about 7.6 mL, about 7.7 mL, about 7.8 mL, about 7.9 mL, about 8 mL, about 8.1 mL, about 8.2 mL, about 8.3 mL, about 8.4 mL, about 8.5 mL, about 8.6 mL, about 8.7 mL, about 8.8 mL, about 8.9 mL, about 9 mL, about 9.1 mL, about 9.2 mL, about 9.3 mL, about 9.4 mL, about 9.5 mL, about 9.6 mL, about 9.7 mL, about 9.8 mL, about 9.9 mL, or about 10 mL.

In embodiments, the expression "stable injectable formulation" is intended to mean shelf stable formulation, stable after secondary dilution, formulation stable during different temperatures (for example, 2°C, 5°C, 25°C, 28°C, and 40°C) for a longer period of time (for example, up to 3 years) and stability of formulation prior to first use and after multiple uses. As used herein, the term "Stabilized formulation” further refers to a stable solution for therapeutic use, containing Vasopressin. As used herein, the term "Stable Unit Dosage form” further refers to the said stable injectable formulation in a unit dosage form for therapeutic use. Vasopressin and associated degradation products or impurities formed in the formulation are listed in Table 1 below:

TABLE 1:
Name Sequence SEQID NO.
Vasopressin (AVP; arginineVasopressin) CYFQNCPRG-NH2 1
Gly9-Vasopressin (Gly9-AVP) CYFQNCPRG 2
Asp5-Vasopressin(Asp5-AVP) CYFQDCPRG-NH2 3
Glu4-Vasopressin (Glu4-AVP) CYFENCPRG-NH2 4
Acetyl-Vasopressin(Acetyl-AVP) Ac-CYFQNCPRG-NH2 5
Dimeric-Vasopressin(Dimer-AVP) (monomerscross linked by disulfide bridges) - -

In one embodiment, the stabilized aqueous formulation of the present invention can be sterilized. Non-limiting examples of sterilization techniques include filtration through a bacterial-retaining filter, terminal sterilization, and incorporation of sterilizing agents, irradiation, and heating. In embodiments, the stabilized aqueous formulation of the present invention comprises a pharmaceutically acceptable solvent or carrier system in which an active ingredient is dissolved in said solvent or carrier system. The pharmaceutically acceptable solvent may be an aqueous solvent such as water, physiological saline and buffer, in which the active is dissolved.

In another embodiment, the preferred buffering agents are selected from citric acid, sodium citrate, acetic acid, Phosphoric acid, sodium phosphate, Lactic acid, acetate buffer and mixtures thereof. In embodiments, the present invention relates to a stabilized aqueous formulation comprising Vasopressin, a buffering agent, optionally a preservative and the said buffering agent stabilizes or maintains the pH of the formulation between about 3.0 and 4.0. A formulation described herein can be used with or without initial vasopressin dilution. The formulations of the present invention can be aliquoted into individual vials or can be premixed, already-diluted, and can be ready for use as a bottle or intravenous drip-bag. The formulation supplied in the bottle can then be transferred to an intravenous drip-bag for administration to a subject. A therapeutically-effective amount of a compound described herein can be present in a composition at a concentration of, for example, about 0.1 units/mL to about 50 units/mL.

In embodiments, the stabilized aqueous formulation of the present invention further comprises total impurities that are present in an amount of 1.0% - 6.73% by Initial Related Substances. In embodiments, the stabilized aqueous formulation of the present invention can be used in the treatment of sepsis and cardiac conditions, and in the elevation of patients suffering from low blood pressure. In embodiments, the stabilized aqueous formulation of the present invention may be prepared by a simple process comprising:

The formulation of the present invention may be prepared by a simple process comprising the following steps:

a) Collect 80% of Water for Injection in a SS vessel.
b) Add suitable buffering agents and/or pH adjustor to adjust pH to 3.8.
c) Add Vasopressin and stir to get a clear solution.
d) Check the pH of bulk solution. Adjust the pH to 3.7-3.9 by using pH adjustor if required.
e) Make up the volume to the required batch size with Water for Injection and stir to get a clear solution.
f) Filter the bulk solution through 0.2µ filter.
g) Fill 1.0 mL of the above filtered bulk solution in 2 mL clear glass vials and close the vial with butyl rubber stopper and seal with aluminum seal.

The formulation of the present invention can also be prepared by a simple process comprising the following steps:
a) Collect 0.8L cool water for injection and add 57ml of glacial acetic acid and make up the volume to 1 Liter
b) Collect Water for Injection in a SS vessel and cool it. Further collect the cooled water for injection (80% of the batch size) in a makeup vessel.
c) Add desired quantity of Chlorobutanol to the solution of step b) and stir till clear solution.
d) Add desired quantity of Vasopressin USP to the solution of step c) and stir till clear solution.
e) Adjust the pH of step d) solution to 3.0 - 3.5 by using 1N acetic acid and stir the solution.
f) Make up the volume to the required batch size with the solution of step a) and stir to get a clear solution.
g) Filter the bulk solution through 0.22µ filter and maintain it at a temperature of 2-8ºC.
h) Fill 1.0 mL of the above filtered bulk solution in 2 mL clear glass vials and close the vial with butyl rubber stopper and seal with aluminum seal.

The following examples are intended to serve as illustrations of the present invention and not intended to be limiting in any manner.

EXAMPLES
Example 1:
S. No. Ingredients Quantity/mL Function
1 Vasopressin 20 Units Active
2 Monobasic sodium phosphate monohydrate 2.5 mg Buffer
3 Dibasic sodium phosphate anhydrous 4 mg Buffer
4 Hydrochloric acid q.s. to adjust pH 3.8 pH Adjustor
5 Water for Injection q.s. to 1 mL Solvent

Data for pH and Related Substances for Example 1:

Based on the study, it can be concluded that the formulation maintains the stability of the drug product.

Example 2A:
S. No. Ingredients Quantity/mL Function
1 Vasopressin 20 Units Active
2 Trisodium citrate dihydrate q.s. Buffer
3 Citric acid monohydrate q.s.
4 Water for Injection q.s. to 1 mL Solvent

Data for pH and Related Substances for Example 2 A:

Based on the study, it can be concluded that the formulation maintains the stability of the drug product.

Example 2 B:
S. No. Ingredients Quantity/mL Function
1 Vasopressin 20 Units Active
2 Trisodium citrate dihydrate q.s. Buffer
3 Citric acid monohydrate q.s.
4 Water for Injection q.s. to 1 mL Solvent

Data for pH and Related Substances for Example 2 B:

Based on the study, it can be concluded that the formulation maintains the stability of the drug product.

Example 3:
S. No. Ingredients Quantity/mL Function
1 Vasopressin 20 Units Active
2 Sodium acetate 0.136 mg Buffer
3 Acetic acid 0.544 mg
4 Water for Injection q.s. to 1 mL Solvent

Data for pH and Related Substances for Example 3:

Based on the study, it can be concluded that the formulation maintains the stability of the drug product.

Example 4:
S. No. Ingredients Quantity/mL Function
1 Vasopressin 20 Units Active
2 Chlorobutanol 5 mg Preservative
3 Glacial Acetic acid Quantity Sufficient Buffer
4 Water for Injection q.s. to 1 mL Solvent

Data for pH and Related Substances for Example 4:

Based on the study, it can be concluded that the formulation maintains the stability of the drug product. ,CLAIMS:We Claim:

1. A stable injectable formulation of Vasopressin comprising buffering agent, optionally a preservative and water for injection.

2. The formulation as claimed in claim 1, wherein the buffering agent of the formulation can be selected from Acetic acid, citric acid, sodium citrate, Phosphoric acid, sodium phosphate, Lactic acid, acetate buffer and mixtures thereof.

3. The formulation as claimed in claim 1, wherein the pH of the formulation is between 3.0 to 4.0, more preferable pH of the formulation is between 3.0 to 3.5.

4. The formulation as claimed in claim 1, further comprises of pharmaceutical excipients such as pH adjusting agents, stabilizing agents including sugars; or mixtures thereof.

5. The formulation as claimed in claim 1, wherein the amount of Vasopressin is in the range of 0.01 mg/mL to about 0.07 mg/mL.

6. The formulation as claimed in claim 1, wherein the fill volume is selected from 0.1 mL to about 30 mL

7. A stable injectable formulation comprising Vasopressin, buffering agent, optionally a preservative and water, wherein the pharmaceutical formulation is having an acidic pH and exhibits less than about 7% degradation.

8. A method of increasing blood pressure by administering a stable unit dosage form, wherein the unit dosage form has an pH between 3.0 to 3.5 and comprises of Vasopressin, buffering agents, optionally a preservative and water for injection.

9. A stable injectable formulation of Vasopressin comprising Vasopressin or a pharmaceutically-acceptable salt thereof from about 0.01 mg/mL to about 0.07 mg/mL, acetic acid, optionally cholobutanol, 0-2% vasopressin degradation products, and water for injection, wherein the formulation has a pH of 3.0 to 3.5.

10. A process of preparation of the stable injectable formulation comprises the following steps:
a) Add cool water for injection to buffering agent
b) Add Chlorobutanol to cool water for injection and stir
c) Add Vasopressin USP to the solution of step b) and stir
d) Adjust the pH of step c) solution to 3.0 - 3.5 by using acetic acid and stir
e) Make up the volume to required batch size with the solution of step a) and stir
f) Filter the solution through filter and maintain it at a temperature of 2-8ºC