FORM 2
THE PATENTS ACT 1970
(39 of 1970)
AND
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rulel3)
1. TITLE OF THE INVENTION:
"PHARMACEUTICAL FORMULATION"
2. APPLICANT:
(a) NAME: CIPLA LTD.
(b)NATIONALITY: Indian Company incorporated under the Companies Act, 1956
(c) ADDRESS: 289, Bellasis Road, Mumbai Central, Mumbai - 400 008, Maharashtra, India.
3.PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of invention and the manner in which it is to be performed.

Technical field
The present invention relates to a parenteral pharmaceutical formulation comprising beta-lactamase inhibitor and beta-lactam antibiotic. The present invention also relates to a process for preparing the said parenteral formulation.
Background of the Invention
Polymicrobial infections are often caused by pathogens that produce beta-lactamase enzymes. These enzymes commonly produce resistance against antibiotics such as penicillins and cephalosporins. Without any treatment these microbes would multiply and thrive unimpeded, leading to serious or critical consequences in the patient. Beta-lactamase inhibitors are potential inhibitors of the enzyme beta-lactamase and therefore are usually combined with penicillin antibiotics to prevent their degradation which is caused by the enzyme beta-lactamases. Tazobactam is one such example of a beta-lactamase inhibitor that is usually combined with Piperacillin, which is an extended spectrum beta-lactam antibiotic belonging to ureidopenicillin class. Tazobactam causes permanent inactivation of beta lactamase enzyme, and allows Piperacillin to destroy susceptible bacteria. This combination therapy exhibits activity against many Gram-positive and Gram-negative pathogens and anaerobes, including Pseudomonas aeruginosa. The combination of Piperacillin and Tazobactam is commercially available as Tazomed- P®, Tazocin® or Zosyn®.
However, owing to the instability exhibited by Piperacillin in aqueous solution at room temperature, these active substances are usually provided as a lyophilized form in injection vials. Thus, prior to administration, this lyophilized powder must be dissolved or reconstituted in a suitable solvent.
WO2000/050035 discloses a premixed ready for use buffered formulation of Piperacillin and Tazobactam. It further teaches that the stability of the formulation is achieved by buffering the solution with citrate to maintain the pH range.

US2008/233196 discloses a sterile pharmaceutical composition comprising piperacillin sodium and Tazobactam sodium mixed with sodium bicarbonate. It further teaches that the addition of small quantities of sodium bicarbonate provides a highly water soluble and sterile solution and presents no problem during its mixing with the active principles, in contrast to other buffer agents that contain water of crystallization (e.g. sodium citrate) which is potentially damaging to the stability of the dry product.
US20070116770A1 discloses a lyophilizate parenteral formulation comprising Tazobactam and Piperacillin. It further teaches co-lyophilization of both the drugs to obtain a lyophilizate that is less cohesive and less hygroscopic. However co-lyophilization requires the concentration of initial solution to be less than l00mg/ml, thus restricting the amount of solution that could be lyophilized at a time. Thus this process is time consuming and further adds cost to the product.
US2009186865 discloses a process of lyophilization wherein carbon dioxide is removed from the solution prior to lyophilization to improve the stability by avoiding the formation of particulates after reconstitution of the lyophilized product.
The parenteral formulation comprising the combination of Piperacillin and Tazobactam as described above have to be reconstituted prior to administration with water and then with Lactated Ringers solution. However, it has been observed that when reconstituted product comprising the combination of Piperacillin and Tazobactam is further diluted with Lactated Ringers Solution there results an incompatibility which may be observed over a period of time.
However, to the best of our knowledge, none of the prior art mentioned above provide a solution to combat the incompatibility of the said combination with lactated Ringer solution.
US6900184 discloses addition of aminobicarboxylic acid for example sodium edetate to the formulation to overcome the incompatibility issue. However, use of EDTA and its salts in formulations is required to be restricted due to serious side effects like cardiac arrest, irregular heartbeat, kidney damage, low blood pressure, low blood sugar and

seizures associated with EDTA. EDTA also alters the absorption of calcium and vitamin, thus decreasing the absorption of essential nutrients in the body.
Therefore, there still exists a need for developing a stable parenteral formulation that overcomes the problems as observed in the prior art formulations.
Object of the Invention
The object of the present invention is to provide a stable parenteral formulation comprising beta lactamase inhibitor and penicillin antibiotic.
Another object of the present invention is to provide a stable parenteral formulation comprising beta lactamase inhibitor and penicillin antibiotic which is compatible with lactated Ringer's solution.
Summary of the invention
According to one aspect of the present invention there is provided a stable parenteral formulation comprising beta lactamase inhibitor and penicillin antibiotic.
According to another aspect of the present invention there is provided a stable parenteral formulation comprising beta lactamase inhibitor, penicillin antibiotic, and buffering agents.
Detailed Description
As mentioned earlier, it is well-known from the prior art that parenteral formulations comprising beta-lactamase inhibitor such as Tazobacam and piperacillin antibiotic such as Piperacillin are incompatible with lactated Ringers solution which is used for diluting the reconstituted product prior to the parenteral administration.
The inventors of the present invention have surprisingly found that by utilizing a buffering system and pH adjusting agent, a stable parenteral formulation comprising Tazobactam and Piperacillin can be prepared that does not require an addition of any

aminocarboxylic substance or any such other chelating substance to overcome the incompatibility of the said formulation when reconstituted with lactated Ringers solution.
The parenteral pharmaceutical formulation comprising Tazobactam and Piperacillin, is compatible with lactated Ringer's solution and is stable as compared to the prior art formulations that contains aminocarboxylic substance or any other such chelating substance.
According to one embodiment of the present invention, beta lactamase inhibitor is preferably Tazobactam sodium or its solvate, derivative, polymorph, enantiomers thereof.
Tazobactam sodium, a derivative of the penicillin nucleus, is a penicillanic acid sulfone. Its chemical name is sodium (2S, 3S, 5R)-3-methyl-7-oxo-3-(lH -1, 2, 3-triazol-1-yImethyl)-4-thia-l-azabicyclo [3.2,0] heptane-2-carboxyIate-4, 4-dioxide. The chemical formula is C10H11N4O5S and the molecular weight is 322.3. The chemical structure of Tazobactam sodium is:

According to present invention, penicillin antibiotic is preferably Piperacillin sodium or its solvate, derivative, polymorph, enantiomers thereof.
Piperacillin sodium is derived from D (-)-a -aminobenzyl-penicillin. The chemical name of piperacillin sodium is sodium (2S, 5R, 6R)-6-[(R)-2-(4-ethyl-2, 3-dioxo-l-piperazine-carboxamido)-2-phenylacetamido]-3,3-dimethyl-7-oxo-4-thia-l-azabicyclo heptane-2-carboxylate. The chemical formula is C23H26N5NaO7S and the molecular weight is 539.5. The chemical structure of piperacillin sodium is:


According to the present invention, the term "stable parenteral formulation" used herein throughout the specification, refers to a formulation wherein there is practically no incompatibility observed in the formulation, comprising of Tazobactam sodium and Piperacillin sodium, and Lactated Ringer's solution.
Addition of a buffer is desired for controlling the pH to enhance stability. Preferably, a suitable amount of buffer controls the pH for maximum stability without significantly catalyzing or degrading the drug, or causing pain to the patient upon infusion.
Suitable buffering agent that may be used in the stable parenteral pharmaceutical formulation of the present invention comprises citric acid and sodium citrate, preferably citric acid anhydrous and sodium citrate dihydrate also known as trisodium citrate dihydrate.
Buffers may be used in a range from 0.01-5.0mg and 10-300mg for citric acid anhydrous and sodium citrate dihydrate respectively by weight of the formulation preferably from G.l-3.0mg and 50-200mg citric acid anhydrous and sodium citrate dihydrate respectively by weight of the formulation.
Suitable pH adjusting agent may be used in the stable parenteral pharmaceutical composition of the present invention to maintain the pH of the solution within limit. These pH adjusting agents may be weak acids or weak bases.
According to one embodiment of the present invention, pH adjusting agent may be a weak acid, preferably sodium bicarbonate.

According to another embodiment of the present invention, the pH of the formulation after reconstitution may be in the range from pH 4.0 to pH 8, preferably in the range from pH5.0 to pH7.0.
The present invention further provides a process of manufacturing the stable parenteral formulation which process comprises providing Tazobactam and Piperacillin, in the form of a formulation suitable for parenteral administration and which is compatible with lactated Ringers solution.
Suitably the process for manufacturing the stable parenteral formulation according to the present invention comprises:
1) adding Tazobactam acid and Piperacillin acid to a vessel containing sterile water for injection.
2) adding buffering agents to the step (1) solution.
3) filtering the step (2) solution and then lyophilizing the mixture
4) granulating the lyophilized mixture
5) blending the granulated mixture and packing in injectable vials.
The present invention further provides a method of administering a stable parenteral pharmaceutical formulation comprising Tazobactam and Piperacillin which method comprises administering the said parenteral formulation subcutaneously, arterially or intravenously or by intravenous infusion.
According to one aspect of the present invention, the stable parenteral pharmaceutical formulation may suitably be provided in the form of dry powder that requires re-constitution prior to administration.
The sterile dry powder for injection according to present invention may be reconstituted with water for injection and further with lactated Ringers solution before administration.
According to another aspect of the present invention, the stable parenteral pharmaceutical formulation may be provided as a ready to use solution for injection.

There is further provided by the present invention a method of treating disorders or conditions that respond to, or are prevented, ameliorated or eliminated by, the administration of Tazobactam sodium and Piperacillin sodium.
The present invention further provides use of the stable parenteral formulation comprising Tazobactam and Piperacillin for treating Appendicitis, Uncomplicated and complicated skin and skin structure infections, including cellulitis, cutaneous abscesses and ischemic/diabetic foot infections, Postpartum endometritis or pelvic inflammatory disease caused by piperacillin-resistant and β-lactamase producing strains of Escherichia coli, community-acquired pneumonia (moderate severity only) and nosocomial pneumonia
The following example is for the purpose of illustration of the invention only and is not intended in any way to limit the scope of the present invention.
Example 1:

Sr. No. Ingredients Quantity [mg]
1 Tazobactam acid 500
2. Piperacillin acid 4000
3. Sodium Citrate dihydrate 200
4. Citric acid anhydrous 1.0
5. Sodium bicarbonate Sufficient to adjust the pH
Process:
1. Tazobactam acid and Piperacillin acid were added to a vessel containing sterile water for injection.
2. Sodium citrate dihydrate, citric acid anhydrous and sodium bicarbonate were added to step 1 solution.
3. The above solution was filtered and then lyophilized.
4. After lyophilization, the mixture was granulated.
5. Granulated mixture was blended and packed in injectable vials.

Experimental results
An experiment was carried out where the stability of Piperacillin and Tazobactam formulation with and without sodium edetate was compared at 25°C and 2-8°C. Following are the results obtained.

Condition Duration Solvent used Total Imp Total Imp pH PH
for NMT 5% NMT 5% [with [without
reconstitution [with EDTA] |without EDTA] EDTA] EDTA]
Sterile Water 2.04 1.31 6.84 6.79
RT
25°C/60% 0 hr for injection

* S.WFI + 1.63 1.46 6.57 6.97
Ringer Lactate
Sterile Water 1.99 1.99 6.44 6.28
Ref 2-8°C 2 days for injection

* S.WFI + 2.26 2.09 6.31 6.18
Ringer Lactate
* S.WFI: Sterile water for injection
Thus it is apparent from the above results that formulation of the present invention i.e., formulation without EDTA is stable when reconstituted with lactated Ringers solution at refrigeration and room temperature without any change in the pH of the formulation.
It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the spirit of the invention. Thus, it should be understood that although the present invention has been specifically disclosed by the preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and such modifications and variations are considered to be falling within the scope of the invention.

It is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural references unless the context clearly dictates otherwise.

We Claim:
1) A stable parenteral formulation comprising beta lactamase inhibitor and penicillin antibiotic and one or more pharmaceutically acceptable excipients.
2) A stable parenteral formulation as claimed in claim 1, wherein the beta lactamase inhibitor is tazobactam or its pharmaceuticaHy acceptable salts, solvates, derivatives, hydrates, anhydrates, enantiomers, polymorphs or mixtures thereof.
3) A stable parenteral formulation as claimed in claim 1, wherein the penicillin antibiotic is piperacillin or its pharmaceutically acceptable salts, solvates, derivatives, hydrates, anhydrates, enantiomers, polymorphs or mixtures thereof.
4) A stable parenteral formulation as claimed in claim 2 and 3, wherein the tazobactam is tazobactam sodium and piperacillin is piperacillin sodium.
5) A stable parenteral formulation as claimed in any of the preceding claims further comprising a buffer.
6) A stable parenteral formulation as claimed in claim 7, wherein the buffer is selected from citric acid anhydrous and sodium citrate dihydrate,
7) A stable parenteral formulation as claimed in any of the preceding claims further comprising a pH adjusting agent.
8) A stable parenteral formulation as claimed in claim 8, wherein the pH adjusting agent is a weak acid.
9) A stable parenteral formulation as claimed in claim 9, wherein the pH adjusting agent is sodium bicarbonate.

10) A stable parenteral formulation as claimed in claims 8, 9 and 10, wherein the pH is from 5 to 7.
11) A stable parenteral formulation as claimed in any of the preceding claims wherein the formulation is a powder for reconstitution.
12) A stable parenteral formulation as claimed in claim 12 wherein the powder for reconstitution is reconstituted with water and lactated Ringers solution.
13) A stable parenteral formulation as claimed in any of the preceding claims wherein the formulation is compatible with lactated Ringers solution.
14) A process for preparing the stable parenteral formulation which process comprises

a) dissolving tazobactam, piperacilin in an aqueous solvent.
b) adding buffers and pH adjusting agents to the solution obtained in step (a)
c) filtering the solution obtained in step (b)
d) lyophilizing the solution obtained in step (c) to obtain a mixture

d) granulating the lyophilized mixture
e) blending the granulated mixture and packing in injectable vials
15) A stable parenteral formulation substantially herein described with reference to the
accompanying examples.