Sulfathiazole 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-(1,3-thiazol-2-yl)benzenesulfonamide and is also known as Sulphathiazole, Sulfathiazol, Norsulfazole and N¹-(2-thiazolyl)sulfanilamide. Sulfathiazole has the molecular formula C₉H₉N₃O₂S₂, molecular weight 255.30 g/mol, and CAS Number 72-14-0.
Sulfathiazole is recognized as a sulfonamide antibacterial and is covered by a Ph. Eur. monograph 0742. The BP 2025 monograph specifies that Sulfathiazole contains not less than 99.0% and not more than 101.0%, calculated with reference to the dried substance.
Sulfathiazole contains a p-aminobenzenesulfonamide structure linked to a 1,3-thiazole ring. Its IUPAC name is 4-amino-N-(1,3-thiazol-2-yl)benzenesulfonamide.
The API is described in the BP 2025/Ph. Eur. monograph as a white or slightly yellowish crystalline powder. It is practically insoluble in water, slightly soluble in ethanol (96%), and practically insoluble in methylene chloride. It dissolves in dilute solutions of alkali hydroxides and dilute mineral acids.
The pharmacopoeial melting point is 200–203°C. The monograph notes that melting may occur around 175°C followed by solidification and a second melting between 200°C and 203°C.
Sulfathiazole is a sulfonamide antibacterial API that has historically been used as an oral and topical antimicrobial. It has also been used in combination with other sulfonamide ingredients in certain pharmaceutical preparations.
Its antibacterial activity is associated with inhibition of bacterial folate metabolism. Historically, Sulfathiazole has been used in pharmaceutical preparations for susceptible bacterial infections, although its use has declined in many applications because of the availability of newer and less toxic antibacterial agents.
The actual indication, dosage, formulation and regulatory status depend on the finished pharmaceutical product and applicable market authorization.
Sulfathiazole belongs to the sulfonamide antibacterial class. Sulfonamides structurally resemble para-aminobenzoic acid (PABA) and interfere with bacterial folate biosynthesis.
Sulfathiazole inhibits dihydropteroate synthase, an enzyme involved in the bacterial folate pathway. This reduces the formation of folate intermediates required for nucleic-acid synthesis and bacterial growth.
The resulting interference with folate metabolism produces antibacterial activity against susceptible organisms.
Sulfathiazole is covered by Ph. Eur. monograph 0742, reproduced in the BP 2025 monograph. The pharmacopoeial definition requires 99.0–101.0% assay on the dried basis.
Identification includes infrared absorption spectrophotometry against Sulfathiazole CRS, along with additional pharmacopoeial identification procedures. The monograph specifies a melting point of 200–203°C.
The related-substances test in the BP/Ph. Eur. monograph uses thin-layer chromatography (TLC). Any spot other than the principal spot is controlled against the sulfanilamide reference solution corresponding to 0.5%.
The monograph specifies loss on drying NMT 0.5%, determined at 105°C, and sulfated ash NMT 0.1%.
The pharmacopoeial assay determines primary aromatic amino-nitrogen by sodium nitrite titration with an electrometric endpoint. Therefore, the compendial assay should not be incorrectly described as an HPLC assay.
The USP monograph also specifies loss on drying NMT 0.5%, residue on ignition NMT 0.1%, and heavy metals 0.002% (20 ppm).
Swapnroop Drugs and Pharmaceuticals provides pharmaceutical API manufacturing and quality-support capabilities for Sulfathiazole, with analytical evaluation aligned with applicable pharmacopoeial and customer-specific requirements.
Sulfathiazole 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 Sulfathiazole API from India, product specifications, analytical documentation and commercial requirements can be evaluated according to the intended application and applicable regulatory market.
Sulfathiazole should be stored protected from light, consistent with the BP 2025/Ph. Eur. monograph.
Suitable pharmaceutical-grade packaging should be used to protect the API from light, moisture and environmental contamination during storage and transportation. Storage conditions should follow the approved product specification and available stability data.
Depending on customer and regulatory requirements, documentation may include:
Sulfathiazole is an established sulfonamide antibacterial API with BP/Ph. Eur. and USP compendial specifications. The BP 2025/Ph. Eur. monograph specifies 99.0–101.0% assay on the dried basis, NMT 0.5% loss on drying, and NMT 0.1% sulfated ash.
Swapnroop Drugs and Pharmaceuticals focuses on controlled pharmaceutical API manufacturing, analytical quality evaluation and documentation support for customers seeking Sulfathiazole 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% |
| Residue on Ignition | NMT 0.1% |
| Heavy Metals | NMT 20 ppm |
| Individual Impurity | NMT 0.5% |
| Melting Point | 200–203°C |