F0RM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - STABILIZED ORAL PHARMACEUTICAL
COMPOSITIONS OF CEPHALOSPORINS
2. Applicant(s)
(a) NAME . LUPIN LIMITED
(b) NATIONALITY : An Indian Company.
(C) ADDRESS : 159, CST Road, Kalina, Santacruz (East), Mumbai-
400 098, State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF INVENTION
The invention relates to oral pharmaceutical compositions of cephalosporins, particularly Cefpodoxime and a method for enhancing the stability of these oral pharmaceutical compositions.
BACKGROUND OF THE INVENTION
Cephalosporins are one of the mainstays of antibacterial therapy today. Cefpodoxime proxetil, (R, S)-l-(isopropoxycarbonyloxy) ethyl - (+)-(6R, 7R)-7-[2-(2-amino-4-thiazolyl)-2-((Z)-methoxyimino)acetamido]-3-methoxymethyl-8-oxo-5-thia-1-azabicyclo [4,2,0]oct-2-en-2-carboxylate, disclosed in U.S. Pat. No. 4,486,425, is a cephalosporin ester pro-drug which, when orally administered, is absorbed and de-esterified through rapid hydrolysis by esterases present on the intestinal mucosa to release its active metabolite, the third generation cephalosporin, cefpodoxime, an antibacterial agent.
Cefpodoxime Proxetil is a valuable antibiotic characterized by high broad-spectrum activity against gram-positive and gram-negative microorganisms. Cefpodoxime exhibits a high degree of β - lactamase stability and is stable towards hydrolysis by the most commonly found plasmid-mediated β- lactamases. It shares the familiar and relatively benign tolerability profile of other broad spectrum cephalosporins with regard to both the incidence and severity of adverse events thus, rendering it as an effective alternative to currently used β - lactams for empirical therapy in a wide range of community acquired infections in both adult and pediatric patients.
Like many cephalosporins, Cefpodoxime proxetil is a highly hydrophobic drug that has a tendency to form a gel in aqueous media, which thereby results in slow dissolution and hence poor bioavailability. It is therefore necessary that the pharmaceutical composition be formulated such that bridging of molecules to form a gel is prevented and thereby, the dissolution is improved.
Apart from ensuring bioavailability, a pharmaceutical dosage form also needs to be stable. The stabilization of cephalosporins such as cefpodoxime, which are highly prone to degradation in the presence of moisture and temperature, is a challenging task for the formulator. The applicants have now surprisingly found that the use of maize starch with moisture content of not more than 2% in oral, pharmaceutical compositions comprising Cefpodoxime proxetil significantly improves stability.
2

OBJECTS OF THE INVENTION
It is the principal object of the present invention to formulate oral pharmaceutical compositions of Cefpodoxime proxetil in which gel formation is minimized and dissolution is improved.
It is a further object of the present invention to formulate oral pharmaceutical compositions comprising Cefpodoxime as a powder for oral suspension to provide a convenient method of preventing gel formation and ensuring adequate bioavailability.
It is another object of the present invention to provide oral, pharmaceutical compositions comprising a cephalosporin, which have adequate bioavailability and stability, the composition comprising cephalosporin and maize starch.
It is another object of the present invention to provide oral, pharmaceutical compositions comprising Cefpodoxime proxetil, which have adequate bioavailability and stability, the composition comprising Cefpodoxime and maize starch.
It is another object of the present invention to provide a method of enhancing the stability profile of cephalosporins in a pharmaceutical composition, the method comprising of contacting the cephalosporin with a stability - enhancing amount of maize starch with moisture content of not more than 2%.
It is another object of the present invention to provide a method of enhancing the stability profile of Cefpodoxime proxetil in a pharmaceutical composition, the method comprising of contacting Cefpodoxime proxetil with stability - enhancing amount of maize starch with moisture content of not more than 2%.
Another object of the invention is to provide a process for preparing an oral, stable, pharmaceutical composition of a cephalosporin comprising the steps of reducing the size of the cephalosporin particles and mixing with maize starch and one or more excipients.
Another object of the invention is to provide a process for preparing an oral, stable, pharmaceutical composition of Cefpodoxime proxetil comprising the steps of reducing the size of the cefpodoxime proxetil particles and mixing with maize starch and one or more excipients.
3

DETAILED DESCRIPTION OF INVENTION
The invention pertains to oral, pharmaceutical compositions of cephalosporins. Examples of cephalosporins include, but are not limited to Cefixime, cefpodoxime proxetil, cefuroxime axetil, Cefdinir, cefaclor, cephalexin and the like.
As used herein, the term cefpodoxime covers cefpodoxime base and the esters of cefpodoxime such as cefpodoxime proxetil and these terms are interchangeable. The maize (com) starch used has moisture content of not more than 2% (low moisture containing maize or corn starch). The low moisture containing starch is maize (corn) starch (e.g. marketed under the brand name of Unipure FL) that has been carefully dried under controlled conditions to meet moisture specifications that is lower than that found in conventional starches. The maize starch with moisture content of not more than 2% can be used in a stability-enhancing amount. By "stability - enhancing amount" is meant an amount which stabilizes a cephalosporin, particularly cefpodoxime proxetil in a composition as compared to a composition which does not contain maize starch and this amount can range from 1-99%. In a preferred embodiment, the maize starch with moisture content of not more than 2% can be used in a range from 5 to 50%.
The term ' dosage form' includes within its scope but is not limited to tablets, capsules, suspensions, suppositories, semisolid preparations and the like. Such dosage forms can additionally comprise one or more excipients, which are well known to the person skilled in the art. Processes well known to the person skilled in the art can be used to prepare these dosage forms e.g. a process for preparing an oral, stable, pharmaceutical composition of a cephalosporin can comprise the steps of reducing the size of the cephalosporin particles and mixing with maize starch and one or more excipients. In a preferred embodiment, a process for preparing an oral, stable, pharmaceutical composition of Cefpodoxime proxetil can comprise the steps of reducing the size of the cefpodoxime proxetil particles and mixing with maize starch and one or more excipients.
A preferred embodiment involves the use of maize starch with moisture content of not more than 2% in an oral, pharmaceutical suspension composition of cephalosporins particularly, Cefpodoxime proxetil.
The term "suspension composition" includes within its scope but is not limited to compositions selected from the group consisting of pellets for suspension which can be coated or uncoated, granules for suspension, in the form of a unit dose packet (sometimes
4

referred to in the art as a "sachet"), in the form of a suspension made from a unit dose packet, in the form of a powder for oral suspension, in the form of a dose sipping device and in the form of an oral suspension per se and combinations of these e.g. coated pellets filled in a dose sipping device or in a sachet. It is noted that when a unit dose packet is constituted, it is probably mainly in the form of a suspension if reconstituted according to directions, although the extent of suspension versus solution depends on a number of factors such as pH. The use of the term "suspension" herein is intended to embrace liquids containing cefpodoxime axetil partially in suspension and partially in solution.
A further preferred embodiment involves the use of maize starch with a moisture content of not more than 2% in a powder for suspension composition of cephalosporins, particularly cefpodoxime proxetil.
The oral, pharmaceutical suspension composition can additionally comprise of atleast one excipient depending upon the dosage form e.g. whether as pellets or as granules for suspension and so on. The excipient can be one or more selected from the group consisting of diluents, binders, disintegrants, stabilizers, wetting agents, sweeteners, thickening agents, dispersing agents, pH - stabilizing agents, flavoring agents, taste - enhancing agents, preservatives, coloring agents, lubricants and flow - aids and the like. One excipient can perform more than one function.
Diluents, which include, but are not limited to mannitol, sucrose, starch, lactose, dicalcium phosphate, xylitol, sorbitol, micro-crystalline cellulose and the like can be used.
Binders which include, but are not limited to, alkylcelluloses such as methyl cellulose, hydroxyalkylcelluloses such as hydroxypropylcellulose, low substituted hydroxypropylcellulose and hydroxypropyl methylcellulose, sodium carboxymethylcellulose or mixtures thereof, pregelatinised maize starch or polyvinylpyrrolidone can be used. Disintegrants, which include but are not limited to, crospovidone, sodium starch glycolate, starches such as maize starch and dried starch, croscarmellose sodium and cellulose products such as microcrystalline cellulose, microfine cellulose, low substituted hydroxypropylcellulose and the like.
Suitable wetting agents can include, but are not limited to, surfactants, either singly or in admixture. Examples of surfactants include, but are not limited to, the polysorbates, sodium lauryl sulphate, poloxamers and the like.
5

Suitable sweeteners include, but are not limited to, natural sweeteners such as sugars e.g. fructose, glucose, sucrose, sugar alcohols such as mannitol, sorbitol or mixtures thereof and artificial sweeteners such as sodium saccharine, sodium cyclamate and aspartame.
Suitable thickening agents function as suspending agents and include, but are not limited to, hydrocolloid gums known for such purpose, examples of which include xanthan gum, guar gum, locust bean gum, gum tragacanth, microcrystalline cellulose and carboxymethylcellulose sodium, sodium carboxymethylcellulose, polyvinylpyrrolidone, hydroxypropylcellulose and the like or mixtures thereof.
Dispersing agents include, but are not limited to, colloidal silicon dioxide and surfactants, wherein the surfactant is used alone or as an admixture with one or more surfactant. Combinations of colloidal silicon dioxide with one or more surfactants can also be used.
The oral, pharmaceutical suspension composition may also contain a pH - stabilizing agent to maintain a desired pH upon reconstitution, as discussed above. The term "pH - stabilizing agent" encompasses buffers and pH - altering agents. Suitable pH - stabilizing agents include tribasic sodium phosphate, anhydrous sodium carbonate, glycine, citric acid and the like or mixtures thereof.
Flavouring agents are well known to persons skilled in the art and include, but are not limited to fruity flavours. Banana Flavour or combinations thereof with other flavours are preferred.
Taste enhancing agents include, but are not limited to, sodium chloride, glycine, citric acid, tartaric acid and the like and mixtures thereof.
Suitable preservatives include, but are not limited to, benzoic acid and sorbic acid and their salts, methyl paraben, butylparaben, propylparaben and the like.
Suitable coloring agents include, but are not limited to, titanium dioxide pigments, lake colours and iron oxide pigments.
Lubricants and flow aids such as, but not limited to, talc, magnesium stearate, calcium silicate and colloidal silicon dioxide can also be used.
All these excipients can be used at levels well known to the persons skilled in the art.
The oral suspension compositions can be prepared by means well known to those skilled in the art.
6

For example, the powder for suspension formulations can be prepared by a process comprising the steps of reducing the size of the cephalosporin and mixing with one or more excipients selected from the group consisting of diluents, binders, disintegrants, stabilizers, wetting agents, sweeteners, thickening agents, dispersing agents, pH - stabilizing agents, flavoring agents, taste - enhancing agents, preservatives, coloring agents, lubricants and flow - aids and the like.
In a preferred embodiment, the powder for suspension formulations can be prepared by a process comprising the steps of reducing the size of Cefpodoxime proxetil and mixing with one or more excipients selected from the group consisting of diluents, binders, disintegrants, stabilizers, wetting agents, sweeteners, thickening agents, dispersing agents, pH -stabilizing agents, flavoring agents, taste - enhancing agents, preservatives, coloring agents, lubricants and flow - aids and the like.
Where applicable, the suspension can be reconstituted using potable water or using juices such as apple juice, strawberry juice, orange juice or using aerated or carbonated preparations. Alternatively, for the suspension per se, vehicles well known to persons skilled in the art, such as propylene glycol, glycerin, sorbitol, liquid glucose and the like can also be used, at levels well known to the persons skilled in the art, in addition to water.
Thus, the invention provides for an oral, pharmaceutical composition, which is stable and has adequate bioavailability, the composition comprising a cephalosporin particularly cefpodoxime proxetil and maize starch. By 'adequate bioavailability' is meant a composition which is bioequivalent to the commercially available oral, pharmaceutical compositions of cephalosporins particularly cefpodoxime proxetil.
The application of the invention can be seen by the following, non limiting examples: EXAMPLE 1.

Sr.No. Ingredients mg/5mL
I II
1. Cefpodoxime Proxetil e. To Cefpodoxime 40 mg 57.80 57.80
2. Microcrystalline cellulose & carboxymethyl -cellulose sodium 100.00 100.0
3. Colloidal silicon dioxide 15.00 15.0
5. Hydroxypropyl cellulose 15.00 15.0
6. Sodium Benzoate 10.00 10.0
7. Silicon dioxide (Syloid) - 600.0
8. Maize Starch (Unipure FL) 300.00 -
7

9. Citric acid anhydrous 10.00 10.0
10. Aspartame - 20.0
12. Art Banana spray dry 15.00 15.0
14. Sucrose EFG 2477.20 215M10
Total 3000.00 3000.00
Brief manufacturing procedure:
1. Cefpodoxime proxetil was micronized and sifted using an appropriate screen on a vibratory sifter.
2. All the other ingredients were sifted through an appropriate screen using a vibratory sifter.
3. One third of the sucrose was milled.
4. All the ingredients were mixed using an octagonal blender.
5. The blend was filled in HDPE bottles.
Table 1: Comparison of the stability profile of powder for oral suspension of Cefpodoxime proxetil formulation I (with maize starch) and formulation II (without maize starch) immediately after reconstitution and 10 days after reconstitution

Assay
0th day 10th day
INITIAL 6 MONTHS 40°C/75%RH INITIAL 6 MONTHS 40°C/75%RH
Formulation I 110.48 104.33 104.85 101.03
Formulation II 105.35 71.98 103.38 76.08
*0th day = Analysis done immediately after reconstitution
*10th day= Analysis done after storage of the reconstituted suspension for 10 days at the
specified condition.
As can be seen, there is a significant difference in the assay values with the formulation
containing stability - enhancing amount of maize starch showing adequate stability as
opposed to the formulation, which does not contain it.
8

We claim:
1. An oral pharmaceutical composition of a cephalosporin, which is stable and has adequate bioavailability, the composition comprising the cephalosporin and maize starch.
2. An oral pharmaceutical composition of Cefpodoxime, which is stable and has adequate bioavailability, the composition comprising Cefpodoxime proxetil and maize starch.
3. An oral pharmaceutical composition of a cephalosporin according to claim 1, wherein the maize starch has a moisture content of not more than 2%.
4. An oral pharmaceutical composition of a cephalosporin according to claim 1, wherein a stability - enhancing amount of maize starch is present.
5. An oral pharmaceutical composition of a cephalosporin according to claim 1, which is in the form of tablets, capsules, suspensions, suppositories, semisolid preparations and the like.
6. An oral pharmaceutical composition of a cephalosporin according to claim 1, wherein the pharmaceutical composition is an oral suspension being a composition selected from the group comprising of pellets for suspension which can be coated or uncoated, granules for suspension, in the form of a unit dose packet (sachet), in the form of a suspension made from a unit dose packet, in the form of a powder for oral suspension, in the form of a dose sipping device and in the form of an oral suspension.
7. An oral pharmaceutical composition of a cephalosporin according to claim 1, wherein maize starch is present in an amount between 1 - 20%.
8. An oral pharmaceutical composition of a cephalosporin according to claim 1, wherein the composition comprises of atleast one additional excipient selected from the group consisting of diluents, binders, disintegrants, stabilizers, wetting agents, sweeteners, thickening agents, dispersing agents, pH - stabilizing agents, flavoring agents, taste - enhancing agents, preservatives, coloring agents, lubricants and flow - aids and the like.
9

9. A process for preparing an oral pharmaceutical composition of a cephalosporin comprising the steps of reducing the size of the cephalosporin and mixing with maize starch and one or more excipients.
10. A process for preparing an oral pharmaceutical composition of Cefpodoxime comprising the steps of reducing the size of Cefpodoxime proxetil and mixing with maize starch and one or more excipients.
11. A method of enhancing the stability profile of a cephalosporin in a pharmaceutical composition, the method comprising of contacting the cephalosporin with a stability -enhancing amount of maize starch with a moisture content of not more than 2%
12. A method of enhancing the stability profile of Cefpodoxime proxetil in a pharmaceutical composition, the method comprising of contacting Cefpodoxime proxetil with stability - enhancing amount of maize starch with a moisture content of not more than 2%.
13. An oral suspension pharmaceutical composition comprising of a cephalosporin and maize starch in a stability - enhancing amount which exhibits an improved stability profile as compared to an oral suspension pharmaceutical composition comprising the said cephalosporin which does not contain maize starch in a stability - enhancing amount.
14. An oral suspension pharmaceutical composition comprising of Cefpodoxime proxetil and maize starch in a stability - enhancing amount which exhibits an improved stability profile as compared to an oral suspension pharmaceutical composition comprising cefpodoxime proxetil which does not contain maize starch in a stability -enhancing amount.


Dated this 3rd day of May 2005

10

ABSTRACT
Title : STABILIZED ORAL PHARMACEUTICAL COMPOSITIONS OF CEPHALOSPORINS
Oral pharmaceutical compositions of cephalosporins, particularly Cefpodoxime, aproces for preparing the same and a method for enhancing the stability of these oral pharmaceutical compositions. The oral pharmaceutical composition of a cephalosporin, is stable and has adequate bio-availability, and comprises the cephalosporin and maize starch. The process for preparing an oral pharmaceutical composition of a cephalosporin comprises the steps of reducing the size of the cephalosporin and mixing with maize starch and one or more excipients. The method of enhancing the stability profile of a cephalosporin in a pharmaceutical composition comprises contacting the cephalosporin with a stability - enhancing amount of maize starch with a moisture content of not more than 2%. The oral suspension exhibits an improved stability profile as compared to an oral suspension pharmaceutical composition comprising the said cephalosporin which does not contain maize starch in a stability - enhancing amount.