Rifamycin is a member of the rifamycin class of antimicrobial agents, with particular activity against mycobacteria. The pharmaceutical substance most appropriately covered by the current pharmacopoeial API monograph is Rifamycin Sodium, the monosodium salt of rifamycin SV. It is produced from rifamycin B obtained through fermentation involving Amycolatopsis mediterranei, followed by chemical transformation to rifamycin SV and its sodium salt.
Rifamycin SV is an ansamycin antibiotic and acts principally by inhibiting bacterial DNA-dependent RNA polymerase. Rifamycin products have applications in antibacterial and antimycobacterial pharmaceutical preparations.
Rifamycin Sodium API
FDA's G-SRS record identifies Rifamycin Sodium as an anti-infective/antibacterial/antitubercular substance and gives CAS 14897-39-3. PubChem reports the molecular formula C₃₇H₄₆NNaO₁₂ and molecular weight 719.7 g/mol.
Rifamycin Sodium is the monosodium salt of rifamycin SV. The current BP/Ph. Eur. monograph describes it as a substance obtained by chemical transformation of rifamycin B, which is produced during growth of certain strains of Amycolatopsis mediterranei.
The API is a complex ansamycin structure containing multiple hydroxyl groups, an acetate ester, an aromatic naphthofuranone region and a macrocyclic ansa chain. It contains 9 defined atom stereocenters and 3 E/Z centers according to the FDA substance record.
Rifamycin SV itself has the formula C₃₇H₄₇NO₁₂ and molecular weight approximately 697.8 g/mol.
Rifamycin Sodium API is used in pharmaceutical manufacturing for antibacterial and antimycobacterial products.
Potential pharmaceutical applications include:
The ATC classification places rifamycin under antibacterial agents and also under antimycobacterial agents used for tuberculosis.
Rifamycin inhibits bacterial DNA-dependent RNA polymerase. By interacting with the bacterial RNA-polymerase system, it interferes with transcription and consequently suppresses bacterial RNA synthesis.
The mechanism is particularly important against mycobacteria, which is why rifamycin-class compounds are classified among antitubercular antibiotics.
Resistance can develop through alterations in the bacterial RNA-polymerase target, making susceptibility and appropriate formulation/therapeutic use important considerations.
The current BP 2025 / Ph. Eur. 0432 monograph provides a detailed analytical framework for Rifamycin Sodium.
Key quality controls include:
The related-substances method uses LC with UV detection at 254 nm. The monograph specifically controls rifamycin B (impurity A), rifamycin S (impurity B), and other impurities.
Rifamycin Sodium is manufactured through a controlled biological and chemical process.
The pharmacopoeial manufacturing description identifies the following general sequence:
The BP specifically states that manufacturing methods should be designed to minimise or eliminate substances capable of lowering blood pressure, an important process-quality consideration for this substance.
These values are taken from the current BP 2025 presentation of Ph. Eur. monograph 0432.
Rifamycin Sodium should be packaged in an airtight container and protected from light.
The BP/Ph. Eur. monograph specifies storage at 2°C to 8°C. If the substance is sterile, it should be stored in a sterile, airtight and tamper-evident container.
Appropriate API packaging should therefore provide:
Typical pharmaceutical documentation for Rifamycin Sodium API can include:
A qualified Rifamycin Sodium API manufacturer should maintain strict control over fermentation-derived starting material, chemical conversion, sodium-salt formation, purification, related substances and microbiological potency.
For this API, potency, rifamycin B, rifamycin S, other related substances, water content and manufacturing-related impurities are particularly important quality attributes. The current pharmacopoeial monograph also establishes a specific endotoxin requirement when the material is intended for manufacture of parenteral preparations without a subsequent appropriate endotoxin-removal process.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| pH (1% Solution) | 6.5 – 8.0 |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 2.0% |
| Water Content | 12.0% – 17.0% |