Rifaximin API Suppliers & Bulk Manufacturers

Available Forms: API (drug substance)

Available Strengths: USP grade or in-house specification

Reference Brands: Xifaxan, Normix

Category: Active Pharmaceutical Ingredient

Rifaximin is a semi-synthetic, poorly absorbed rifamycin antibiotic used for gut infections, hepatic encephalopathy and IBS-D. Formulation makers and CDMOs source the API.

Product Description:

Rifaximin is a rifamycin antibiotic derived from rifamycin SV; it blocks bacterial RNA synthesis and stays mostly in the gut because very little is absorbed. It is approved for travellers' diarrhoea caused by non-invasive E. coli, to reduce the risk of recurrent overt hepatic encephalopathy in adults, and for irritable bowel syndrome with diarrhoea in adults (reference brand: Xifaxan, Normix).

Specification at a glance

Regulatory files and timing

The FDA list of Drug Master Files (third quarter 2026) shows 18 active Type II API DMFs for this molecule. There is a fair choice of sources, so compare documents and impurity profiles, not just price. For Europe, ask whether the supplier holds a CEP or an EU ASMF and, for imports into the EU, a written confirmation.

Generic or biosimilar entry. United States: Entry expected (Jan 2028 (settlements)). European Union: No confirmed date.

Handling and quality points

Rifaximin exists in several crystalline and amorphous forms with different solubility and absorption, and specific forms are covered by patents, so the polymorph must be specified and tested by XRPD. Water content drives conversion between some forms, so drying, packing and storage conditions matter. Ask for related substances data, including rifamycin SV and other process impurities, plus a nitrosamine risk assessment.

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Brand names are trademarks of their respective owners and identify the reference medicine only. Information is general and was checked in October 2026; confirm specifications and filings with the supplier before purchase.