Sulfamethizole API is a synthetic sulfonamide antibacterial active pharmaceutical ingredient belonging to the sulfonamide class of antimicrobial compounds. Chemically, it is identified as 4-amino-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide. Sulfamethizole has the molecular formula C₉H₁₀N₄O₂S₂, molecular weight 270.33 g/mol, and CAS Number 144-82-1.
Sulfamethizole is recognized as a sulfonamide antibacterial and is covered by a European Pharmacopoeia monograph. The Ph. Eur. specification defines Sulfamethizole at 99.0–101.0%, calculated with reference to the dried substance.
Sulfamethizole contains a 1,3,4-thiadiazole ring with a methyl substituent connected through a sulfonamide group to a para-aminobenzene ring. Its systematic chemical name is 4-amino-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide.
Sulfamethizole is described pharmacopoeially as a white or yellowish-white crystalline powder or crystals. It is very slightly soluble in water, soluble in acetone and sparingly soluble in ethanol (96%). It dissolves in dilute alkali hydroxide solutions and dilute mineral acids.
The compound has a melting point of approximately 210°C in the Ph. Eur. specification, while the Japanese Pharmacopoeia specifies 208–211°C.
Sulfamethizole is a sulfonamide antibacterial API that has been used in pharmaceutical formulations for the treatment of susceptible bacterial infections.
Its relatively high urinary excretion and antibacterial activity have historically supported its use in pharmaceutical preparations for urinary tract infections. Sulfamethizole has also been incorporated into combination pharmaceutical products.
The actual indication, dosage, formulation, target population and regulatory status depend on the finished medicinal product and the applicable market authorization.
Sulfamethizole acts as a member of the sulfonamide antibacterial class. Sulfonamides structurally resemble para-aminobenzoic acid (PABA) and interfere with bacterial folate biosynthesis.
By inhibiting dihydropteroate synthase, sulfonamides reduce the formation of folate intermediates required for bacterial nucleotide synthesis. This disruption inhibits bacterial growth and produces the antibacterial effect.
Sulfamethizole is covered by Ph. Eur. monograph 0637, which establishes requirements for identification, acidity, related substances, loss on drying, sulfated ash and assay.
The pharmacopoeial definition requires Sulfamethizole to contain 99.0–101.0% of the active substance, calculated with reference to the dried substance.
Identification includes infrared absorption spectrophotometry using Sulfamethizole CRS. The monograph also specifies a characteristic melting point of approximately 210°C.
The current referenced Ph. Eur. analytical procedure controls related substances by liquid chromatography. The specified limits include Sulfamethizole impurity D NMT 0.20%, each unspecified impurity NMT 0.10%, and total impurities NMT 0.50%.
The monograph specifies loss on drying NMT 0.5% and sulfated ash NMT 0.1%.
The pharmacopoeial assay is based on determination of primary aromatic amino-nitrogen using sodium nitrite titration, with an electrometric endpoint, rather than an HPLC assay.
Swapnroop Drugs and Pharmaceuticals provides pharmaceutical API manufacturing and quality-support capabilities for Sulfamethizole, with analytical evaluation aligned with applicable pharmacopoeial and customer-specific requirements.
Sulfamethizole API can be evaluated for identity, assay, related substances, loss on drying, sulfated ash, melting range and other applicable quality parameters according to the agreed specification.
For pharmaceutical manufacturers seeking Sulfamethizole API from India, product specifications, analytical documentation and commercial requirements can be evaluated according to the intended application and applicable regulatory market.
Sulfamethizole should be protected from light, consistent with the Ph. Eur. monograph.
Suitable pharmaceutical-grade packaging should be used to protect the API from light and environmental exposure during storage and transportation. Packaging configuration and storage conditions should follow the approved product specification and stability data.
Depending on customer and regulatory requirements, documentation may include:
Sulfamethizole is an established sulfonamide antibacterial API with a Ph. Eur. monograph defining identity, assay, related substances and key physical-quality requirements. The referenced pharmacopoeial specification provides 99.0–101.0% assay, NMT 0.5% loss on drying, NMT 0.1% sulfated ash and NMT 0.5% total impurities.
Swapnroop Drugs and Pharmaceuticals focuses on controlled pharmaceutical API manufacturing, analytical quality evaluation and documentation support for customers seeking Sulfamethizole API.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 99.0–101.0% on dried basis |
| Loss on Drying | NMT 0.5% |
| Heavy Metals | NMT 20 ppm |
| Individual Impurity | NMT 0.20% |
| Total Impurities | NMT 0.50% |
| Melting Point | About 210°C |