Sulfadimidine, also known as Sulfamethazine and Sulphadimidine, is a synthetic sulfonamide antibacterial active pharmaceutical ingredient. It is chemically identified as 4-amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide and has the molecular formula C₁₂H₁₄N₄O₂S, molecular weight 278.33 g/mol, and CAS Number 57-68-1. FDA's Global Substance Registration System lists Sulfadimidine/Sulfamethazine under CAS 57-68-1 and recognizes its various pharmacopoeial and international synonyms.
Sulfadimidine is a sulfonamide antibacterial that acts by interfering with bacterial folate synthesis. It is included in the British Pharmacopoeia/European Pharmacopoeia as a medicinal substance, where it is defined with a content requirement of 99.0% to 101.0% on the dried substance.
Sulfadimidine is a synthetic antimicrobial compound belonging to the sulfonamide class. Its chemical structure contains a sulfonamide group linked to a substituted pyrimidine ring. The compound is primarily characterized by its antibacterial activity and its ability to interfere with folate metabolism in susceptible microorganisms.
The API is available as a white or almost white powder or crystals. According to the BP/Ph. Eur. monograph, it is very slightly soluble in water, soluble in acetone and slightly soluble in ethanol (96%). It also dissolves in solutions of alkali hydroxides and dilute mineral acids.
Sulfadimidine has the molecular formula C₁₂H₁₄N₄O₂S and molecular weight 278.33 g/mol. Its chemical name is 4-amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide. The substance is also known internationally as Sulfamethazine, Sulphadimidine and Sulfadimidinum.
The API is generally supplied in its non-salt form. This distinction is important because Sulfadimidine/Sulfamethazine (CAS 57-68-1) should not be confused with Sulfadimidine Sodium/Sulfamethazine Sodium, which is a separate salt form with different molecular characteristics.
Sulfadimidine has historically been used as a sulfonamide antibacterial active ingredient. It has been associated with pharmaceutical and veterinary antimicrobial preparations and is recognized in pharmacopoeial references as a sulfonamide antibacterial.
Its pharmaceutical use depends on the applicable regulatory jurisdiction, formulation and approved indication. Manufacturers should therefore apply the appropriate current regulatory requirements when developing or manufacturing products containing Sulfadimidine.
Sulfadimidine acts as a structural analogue of para-aminobenzoic acid (PABA). It competitively inhibits bacterial dihydropteroate synthase, an enzyme involved in folate biosynthesis. Interference with this pathway reduces the availability of folate derivatives required for nucleotide synthesis and bacterial growth.
The BP/Ph. Eur. monograph provides detailed quality controls for Sulfadimidine. The assay requirement is 99.0%–101.0% on a dried-substance basis. Identification includes infrared absorption spectrophotometry and chromatographic procedures.
Related substances are controlled by liquid chromatography. Specified impurities C, D and G are each limited to NMT 0.10%, unspecified impurities are individually limited to NMT 0.05%, total impurities are limited to NMT 0.50%, and the disregard limit is 0.03%. Loss on drying is NMT 0.5%, while sulfated ash is NMT 0.1%.
Manufacturing of Sulfadimidine API involves controlled chemical synthesis followed by purification, crystallization and drying. Process controls are important for maintaining chemical identity, assay, impurity profile and physical characteristics.
Particular attention is required for the control of related sulfonamide impurities, including sulfanilamide, sulfacetamide, sulfaguanidine and related pyrimidine derivatives. The BP/Ph. Eur. monograph specifically identifies several of these compounds as potential impurities.
Sulfadimidine is a white or almost white powder or crystalline material. It is very slightly soluble in water, soluble in acetone and slightly soluble in ethanol. The historical pharmacopoeial description reports that it melts at approximately 197°C with decomposition.
Sulfadimidine should be packaged in suitable pharmaceutical-grade containers that protect the material from environmental exposure. The BP/Ph. Eur. monograph specifies that the substance should be protected from light.
A pharmaceutical API supply package can include a Certificate of Analysis (CoA), specification sheet, Safety Data Sheet (SDS), batch documentation, analytical reports and applicable regulatory documentation.
A reliable Sulfadimidine API manufacturer should maintain consistent control over assay, related substances, loss on drying, sulfated ash, identity and physical characteristics. Pharmacopoeial testing and appropriate analytical controls help ensure that each batch meets the applicable quality standard.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 99.0–101.0% |
| Loss on Drying | NMT 0.5% |
| Individual Impurity | NMT 0.05% |
| Total Impurities | NMT 0.50% |
| Melting Point | About 197°C |