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Rifaximin

a technology of rifaximin and amorphous form, which is applied in the field of rifaximin, can solve the problem that none of the above patents discloses a wholly amorphous form of rifaximin

Inactive Publication Date: 2012-05-10
CIPLA LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention provides a new form of the drug rifaximin, which is in a pure and crystal-free state. This new form can be easily prepared and can be used in pharmaceutical compositions. The technical effect of this invention is the ability to obtain a more pure and usable form of rifaximin for therapeutic use.

Problems solved by technology

However, none of the above patents disclose a wholly amorphous form of rifaximin.
In addition, amorphous solids do not give rise to a specific melting point and tend to liquefy at some point beyond the glass transition temperature.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0061]Rifamycin S 100 g (0.143 moles), dichloromethane 300 ml and 2-amino-4-picoline, 46.4 g (0.434 moles) were mixed at room temperature under argon atmosphere. Iodine 19 g (0.074 moles) dissolved in dichloromethane 700 ml, was added dropwise in 30-45 minutes at room temperature. Reaction mixture was then stirred at room temperature for 15-18 hours. L(−) Ascorbic acid 20 g (0.113 moles) dissolved in 100 ml water was added. The mixture was stirred for 30-45 minutes at room temperature and then cooled to 10 to 15° C. The pH of the reaction mixture was adjusted to 2 using 12.5% dil. HCl solution. The mass was stirred for 10 to 15 minutes, organic layer was separated and washed at first with demineralized water then with 10% sodium thiosulfate and finally with water till neutral pH was obtained. The organic layer was charcolized, filtered through hyflo, dried over sodium sulfate and concentrated under vacuum below 50° C. The product was stripped out with n-heptane and crude material th...

example 2

[0062]Amorphous rifaximin (100 g) was dissolved in acetic acid (200 ml) at 50° C., stirred for 30-45 minutes and demineralized water (200 ml) was added dropwise at 50° C. in 30-45 minutes. Stirring was continued at 50° C. for 30-45 minutes, cooled gradually to room temperature and stirred for 2 hours. The solid obtained was filtered and washed at first with acetic acid-water 1:1 mixture then with 10% acetic acid-water mixture and finally washed with water. The solid obtained was dried at 100-110° C. for 12-15 hours to get 62-65 g of rifaximin-γ-form.

example 3

[0063]Amorphous rifaximin (100 g) was dissolved in formic acid (200 ml) at 50° C., stirred for 30-45 minutes and demineralized water (200 ml) was added dropwise at 50° C. in 30-45 minutes. Stirring was continued at 50° C. for 30-45 minutes, cooled gradually to room temperature and stirred for 2 hours. The solid obtained was filtered and washed at first with formic acid-water 1:1 mixture then with 10% formic acid-water mixture and finally washed with water. The solid obtained was dissolved in Isopropyl alcohol (310 ml) at 50° C. and stirred at 50° C. for 30 minutes. Demineralized water (310 ml) was added dropwise at 50° C. in 30-45 minutes and stirring was continued at the same temperature for 30-45 minutes. The mixture was cooled gradually to room temperature and stirred for 2 hours. The solid obtained was filtered, washed with Isopropyl alcohol-water 1:1 mixture and then with demineralized water, dried at 80-90° C. for 10-15 hours to get 40-45 g of rifaximin-β-form.

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Abstract

Amorphous rifaximin, methods of making it, and pharmaceutical compositions containing it. Also described are methods of converting amorphous rifaximin to crystalline rifaximin and vice versa.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a Continuation Application of U.S. application Ser. No. 12 / 441,368 having a 371(c) date of Aug. 3, 2009 and published as US 2009 / 0312357 A1 and entitled “Rifaximin” which was a filing under 35 U.S.C. 371 of International Application No. PCT / GB2007 / 003629 filed Sep. 24, 2007, entitled “Rifaximin,” claiming priority of Indian Patent Application No. 1520 / MUM / 2006 filed Sep. 22, 2006, which applications are incorporated by reference herein in their entirety.FIELD OF THE INVENTION[0002]The present invention relates to amorphous rifaximin, pharmaceutical compositions containing the same, processes for preparing amorphous rifaximin and to therapeutic uses and therapeutic methods of treatment employing amorphous rifaximin, or such pharmaceutical compositions, medicaments or products.BACKGROUND OF THE INVENTION[0003]Rifaximin is a semi-synthetic, rifamycin-based non-systematic antibiotic. It is chemically termed as (2S,16Z,18E,...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C07D498/22
CPCC07D498/22A61K31/437A61P1/00A61P1/04A61P1/12A61P1/18A61P31/04Y02A50/30
Inventor RAO, DHARMARAJ RAMACHANDRAKANKAN, RAJENDRA NARAYANRAOPHULL, MANJINDER SINGHGHAGARE, MARUTI
Owner CIPLA LTD
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