Sulphacetamide Sodium, commonly spelled Sulfacetamide Sodium, is a sulfonamide antibacterial active pharmaceutical ingredient. The pharmaceutical substance is the monohydrate, with molecular formula C₈H₉N₂NaO₃S·H₂O and molecular weight 254.24 g/mol. The CAS number for the monohydrate is 6209-17-2, while the anhydrous substance is CAS 127-56-0. USP identifies Sulfacetamide Sodium as the monosodium salt monohydrate.
The API is described in the BP/Ph. Eur. monograph as Sodium acetyl[(4-aminophenyl)sulfonyl]azanide monohydrate. It occurs as a white or yellowish-white crystalline powder and is freely soluble in water and slightly soluble in anhydrous ethanol.
Sulfacetamide Sodium is a sulfonamide antibacterial that interferes with bacterial folate synthesis. Sulfonamides act as structural analogues of para-aminobenzoic acid and inhibit bacterial dihydropteroate synthase, thereby interfering with folate-dependent bacterial growth.
The sodium salt provides substantially greater aqueous solubility than the corresponding free compound, making it suitable for aqueous pharmaceutical formulations.
Sulfacetamide Sodium has an anhydrous molecular weight of 236.23 g/mol and a monohydrate molecular weight of 254.24 g/mol. The controlled water content reflects its monohydrate nature. USP specifies the API assay on an anhydrous basis.
The BP/Ph. Eur. monograph specifies a melting-point identification range of 181–185°C after precipitation of sulfacetamide during the identification procedure.
Sulfacetamide Sodium is used as an active ingredient in topical and ophthalmic antibacterial formulations. Pharmaceutical formulations may use the sodium salt where its water solubility is advantageous.
The API has also been used in topical dermatological products, including formulations designed for conditions where antibacterial sulfonamide activity is required.
Sulfacetamide Sodium competitively interferes with the bacterial utilization of PABA by inhibiting dihydropteroate synthase. This interrupts folate biosynthesis and reduces the availability of folate derivatives needed for bacterial nucleic-acid synthesis.
Sulfacetamide Sodium has established pharmacopoeial specifications. USP defines the substance as containing NLT 99.0% and NMT 100.5% sulfacetamide sodium calculated on the anhydrous basis.
The BP/Ph. Eur. monograph specifies 99.0–101.0% on an anhydrous basis, pH 8.0–9.5, water 6.0–8.0%, sulfates NMT 200 ppm, and total related substances NMT 0.5%. Sulfanilamide is controlled at NMT 0.20%, while each unspecified impurity is limited to NMT 0.10%.
Manufacturing involves controlled synthesis, salt formation, crystallization and drying. Because the API is a monohydrate, control of water content is particularly important for maintaining consistency between batches.
Analytical release testing should confirm identity, assay, related substances, pH, water content and other applicable pharmacopoeial attributes.
Sulfacetamide Sodium is a white or yellowish-white crystalline powder. It is freely soluble in water and slightly soluble in anhydrous ethanol. Its aqueous solution is alkaline, with the BP/Ph. Eur. monograph specifying pH 8.0–9.5.
The API should be packaged in suitable pharmaceutical-grade containers that protect it from moisture, contamination and excessive environmental exposure. The BP/Ph. Eur. monograph specifies that Sulfacetamide Sodium should be protected from light.
Typical API documentation may include Certificate of Analysis (CoA), specification sheet, Safety Data Sheet (SDS), batch analytical records, impurity profile, stability information and applicable regulatory documentation.
A qualified Sulphacetamide Sodium API manufacturer should maintain controlled synthesis, validated analytical methods and appropriate control of assay, related substances, water content and solid-state characteristics. Pharmacopoeial compliance and complete batch documentation support consistent pharmaceutical API quality.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 99.0–101.0% on anhydrous basis |
| pH (1% Solution) | 8.0–9.5 |
| Individual Impurity | NMT 0.10% |
| Total Impurities | NMT 0.50% |
| Water Content | NMT 0.50% |
| Melting Point | 181–185°C |