Sulfacetamide Sodium is the monosodium salt monohydrate of sulfacetamide, a sulfonamide antibacterial active pharmaceutical ingredient (API). It is chemically identified as N-sulfanilylacetamide monosodium salt monohydrate and is widely used in pharmaceutical formulations intended for topical and ophthalmic applications. FDA substance records identify Sulfacetamide Sodium as the monohydrate with the molecular formula C₈H₉N₂NaO₃S·H₂O and molecular weight 254.24 g/mol.
Sulfacetamide Sodium is recognized in major pharmacopoeial references, including USP and Ph. Eur./BP. The current USP monograph defines the substance at 99.0%–100.5% on an anhydrous basis, while the BP/Ph. Eur. monograph specifies 99.0%–101.0% on an anhydrous basis.
As a sulfonamide antibacterial, Sulfacetamide Sodium inhibits bacterial folate synthesis. Sulfonamides act as competitive antagonists of para-aminobenzoic acid (PABA), inhibiting the bacterial enzyme dihydropteroate synthetase and thereby interfering with formation of dihydrofolic acid. This produces a predominantly bacteriostatic antibacterial effect.
The API is particularly suitable for pharmaceutical manufacturers developing topical and ophthalmic dosage forms. FDA-listed ophthalmic formulations use Sulfacetamide Sodium at a concentration of 100 mg/mL (10%).
Sulfacetamide Sodium occurs as a white to yellowish-white crystalline powder and is freely soluble in water and slightly soluble in anhydrous ethanol according to the BP/Ph. Eur. monograph. Its aqueous solution is alkaline, with a pharmacopoeial pH range of 8.0–9.5.
The monohydrate form is important when specifying this API because its molecular weight and water content differ from the anhydrous substance. FDA records specifically identify the pharmaceutical substance as the monohydrate.
Sulfacetamide Sodium is used as an active ingredient in ophthalmic antibacterial preparations for susceptible superficial ocular infections. FDA-listed 10% ophthalmic products contain 100 mg/mL Sulfacetamide Sodium and are intended for topical ocular use.
The API is also incorporated into topical dermatological formulations. Sodium sulfacetamide preparations, including combinations with sulfur, are used in formulations intended for the topical control of acne vulgaris, acne rosacea and seborrheic dermatitis.
Sulfacetamide Sodium works through the sulfonamide pathway by competing with PABA. In susceptible microorganisms, inhibition of dihydropteroate synthetase disrupts folate synthesis, which is essential for bacterial growth and reproduction.
Pharmacopoeial quality control includes identification, assay, related substances, pH and water determination. USP 2025 specifies an assay range of 99.0%–100.5% on an anhydrous basis, pH 8.0–9.5, and water NMT 8.1%. USP related-substance controls include sulfanilamide at NMT 0.20%, any unspecified individual impurity at NMT 0.10%, and total impurities at NMT 0.50%.
The BP/Ph. Eur. monograph similarly specifies impurity A (sulfanilamide) at NMT 0.20%, unspecified impurities individually at NMT 0.10%, total impurities at NMT 0.50%, and a disregard limit of 0.05%. It also controls sulfates at NMT 200 ppm.
Manufacturing of Sulfacetamide Sodium API requires controlled synthesis, salt formation and crystallization followed by purification and drying under conditions that maintain the required chemical purity and hydrate state. Critical quality attributes include assay, related substances, pH, water content, appearance and identity.
Because the substance is a monohydrate and pharmacopoeial assay is expressed on an anhydrous basis, control of water content is particularly important during manufacturing and packaging.
Sulfacetamide Sodium is a crystalline, water-soluble sulfonamide salt. BP/Ph. Eur. describes it as freely soluble in water and slightly soluble in anhydrous ethanol. The monograph reports a melting-point identification test of 181–185°C for sulfacetamide liberated from the sodium salt during the identification procedure; this should be treated as a reference/identification value rather than a direct release specification for the sodium salt.
Pharmacopoeial guidance specifies protection from light, while USP calls for storage in tight, light-resistant containers. Appropriate moisture-protective packaging is recommended because the material is a defined hydrate and water content is a controlled quality attribute.
Typical pharmaceutical API documentation can include a Certificate of Analysis (CoA), specification sheet, Safety Data Sheet (SDS), manufacturing and quality documentation, analytical test reports, batch information and applicable regulatory documentation.
A qualified Sulfacetamide Sodium API manufacturer should provide consistent control of assay, hydrate/water content, related substances, pH and identity according to the applicable pharmacopoeial standard. A robust quality system, validated analytical procedures, controlled manufacturing environment and traceable batch documentation are important for pharmaceutical manufacturers sourcing this API.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 99.0–100.5% on anhydrous basis |
| pH (1% Solution) | 8.0–9.5 |
| Individual Impurity | NMT 0.10% |
| Total Impurities | NMT 0.50% |
| Water Content | NMT 8.1% |
| Melting Point | 181–185°C |