| HS Code | 245725 |
| Chemical Name | Silver sulfadiazine |
| Molecular Formula | C10H9AgN4O2S |
| Molecular Weight | 357.14 g/mol |
| Cas Number | 22199-08-2 |
| Description | White to off-white crystalline powder; suitable for veterinary pharmaceutical formulations including tablets, injections, capsules, powders, granules, premix, and solutions |
| Solubility | Practically insoluble in water; slightly soluble in ethanol; freely soluble in dilute mineral acids and alkali hydroxides |
| Assay Value | 98.0% - 102.0% on dried basis |
| Ph Value | 5.5 - 7.0 (suspension in water) |
| Storage Conditions | Store in airtight containers, protected from light, at controlled room temperature 15°C - 25°C |
| Shelf Life | 24 months from date of manufacture when stored under recommended conditions |
| Veterinary Indication Property | Provides broad-spectrum antibacterial activity against gram-positive and gram-negative bacteria; used for wound infections, burns, and systemic infections in animals |
As an accredited Silver Sulfadiazine Suspension Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in sealed, moisture-protected drums, 25 kg net per drum, labeled for veterinary pharmaceutical use. |
| Container Loading (20′ FCL) | A 20′ FCL container loaded with Silver Sulfadiazine Suspension Veterinary Grade API, securely packed in sealed drums for safe transport. |
| Shipping | Ship Silver Sulfadiazine Suspension (Veterinary Grade API) under controlled temperature, away from light and moisture. Use sealed, corrosion-resistant drums or HDPE containers with proper hazardous goods labeling. Include MSDS, certificate of analysis, and customs documentation. Ensure compliance with veterinary pharmaceutical transport regulations for safe, traceable delivery. |
| Storage | Store Silver Sulfadiazine Suspension (Veterinary Grade API) in a tightly sealed, light-resistant container in a cool, dry, well-ventilated area. Protect from direct sunlight, moisture, and excessive heat. Avoid contact with metals. Maintain controlled room temperature and ensure container integrity until use. Keep out of reach of children. |
| Shelf Life | Shelf life is typically 24 months in unopened, tightly sealed containers, stored in a cool, dry place protected from light. |
In companion animal dermatology, a 1% w/w silver sulfadiazine nonsterile cream is prepared from the veterinary-grade suspension by first discharging the API slurry into a glycerin or propylene glycol wetting phase; direct addition of the suspension into a heated aqueous phase is avoided because production batches on rotary ointment mills have shown hard agglomerates that survive colloid milling and require rework. The 1% w/w loading is aligned with the standard canine and feline burn and wound concentration referenced in veterinary formularies; published data do not support routine loading above 1.5% w/w for improved re-epithelialization, and higher silver exposure increases the risk of delayed keratinocyte migration. The veterinary-grade suspension is distributed for nonsterile topical dosage forms; tablets, capsules, and injectable solutions are not currently listed as supported downstream formats because systemic silver exposure in veterinary species lacks established safe residue limits. Microbial quality is controlled by USP <61> and USP <62>; antimicrobial preservation is evaluated by USP <51>; nonsterile compounded preparations are released under USP <795>, while commercial manufacturing falls under FDA 21 CFR 210 and 21 CFR 211, with sampling and testing under 21 CFR 211.110. In the production process, the oil phase is heated to 65°C–70°C and the aqueous phase to 60°C–65°C; the silver sulfadiazine/glycerin dispersion is introduced under a rotor-stator homogenizer at 2,500 rpm–3,500 rpm before the oil phase is added, and the batch is cooled to 25°C–30°C with side-sweep agitation. Deaeration is performed under vacuum at -0.06 MPa to -0.08 MPa for 20 min–30 min, and final viscosity is confirmed with a Brookfield T-bar spindle at 5 rpm. Chloride-containing wetting phases are not used because chloride precipitates silver ion and reduces free antimicrobial activity. Finished formats include 15 g, 30 g, and 454 g collapsible aluminum-tube creams, single-use postoperative ointment packs, and bulk nonsterile creams supplied to veterinary compounding pharmacies.
Aqueous wound sprays compounded from veterinary-grade silver sulfadiazine suspension are subject to a settling limitation that dictates line design: the delivered concentration changes during the filling campaign if the suspension is not continuously recirculated, because dispersed silver sulfadiazine particles settle in the manifold and check valves at a rate dependent on mean particle size, vehicle viscosity, and pump shear. Target concentrations are typically established between 0.05% w/v and 0.5% w/v; the lower bound is selected on the basis of minimum inhibitory concentration data generated by broth microdilution according to CLSI M07-A10, while the upper bound is limited by nozzle clogging and visible residue on hair-coat surfaces. The vehicle is prepared with a suspending agent, commonly hydroxyethylcellulose at 0.5% w/v or xanthan gum at 0.25% w/v, hydrated under high-shear dispersion, and then the silver sulfadiazine slurry is added under a rotor-stator mixer at 3,000 rpm for 15 min. The pH is maintained at 4.5–5.5 because lower pH promotes sulfadiazine precipitation and higher pH accelerates silver oxide formation. For filling, a 60-mesh in-line strainer and a recirculating peristaltic pump operating at not less than 2 L/min through the manifold are used to keep the suspension homogeneous; without recirculation, concentration drift across the filling campaign is observed even when the bulk tank is stirred. Published line data for this specific low-concentration veterinary spray configuration is limited; therefore the recirculation threshold should be verified by in-process concentration assay before a commercial campaign is released. Equipment cleaning between campaigns follows 21 CFR 211.67 because silver residues adsorb on stainless steel. Microbial limits are tested under Ph. Eur. 2.6.12 and Ph. Eur. 2.6.13, preservative efficacy under USP <51>, and residual solvent control under VICH GL18 for formulations containing cosolvents. Finished product types include 100 mL and 250 mL high-density polyethylene trigger sprays, 50 mL single-use spray vials, and aseptically processed water-miscible wound irrigation ampoules.
| Dosage form | Active concentration | Primary process threshold | Finished format |
|---|---|---|---|
| Cream | 1% w/w | Pre-wetting in glycerin; rotor-stator 2,500 rpm–3,500 rpm | 15 g, 30 g, 454 g tubes |
| Aqueous spray | 0.05% w/v–0.5% w/v | Recirculation rate ≥2 L/min; pH 4.5–5.5 | 100 mL, 250 mL HDPE trigger sprays |
| Dusting powder | 1% w/w | Geometric dilution; 60-mesh sieve; blend RSD ≤5.0% per USP <905> | 50 g, 200 g sachets |
| Otic suspension | 0.5% w/v–1% w/v | Osmolality 280 mOsm/kg–320 mOsm/kg; pH 4.5–5.5 | 10 mL, 20 mL dropper bottles |
| Premix granules | 1% w/w | Fluid-bed product temperature 30°C–40°C; final moisture ≤3.0% | 5 g, 25 g single-use granules |
For equine distal limb wounds, a 1% w/w silver sulfadiazine dusting powder is manufactured by drying the veterinary-grade suspension in a vacuum tray dryer at 40°C–45°C to a loss on drying of not more than 3.0%, then passing the dried active through a 60-mesh stainless steel sieve before geometric dilution with a zinc oxide or modified starch carrier; this format is selected because occlusive cream dressings slide or are removed under bandaging in high-movement zones. The finished powder must meet USP <905> uniformity of dosage units and Ph. Eur. 2.9.5 mass uniformity criteria, with microbial limits under USP <61> and USP <62>; residual solvents from the drying step are controlled under VICH GL18, and elemental impurities are controlled under ICH Q3D. The blending process uses a V-blender with an intensifier bar at 10 rpm for 15 min after the active-carrying fraction is passed through a 60-mesh stainless steel sieve and geometrically diluted in a 1:1, 1:2, 1:4 active-to-base sequence to avoid concentration hot spots. Stratified sampling at the beginning, middle, and end of discharge is evaluated by high-performance liquid chromatography; release is allowed when individual samples fall within 90.0%–110.0% of label claim and the relative standard deviation is not more than 5.0%. Finished products include 50 g and 200 g polypropylene sachets, 500 g wide-mouth jars for equine hospital use, and bulk powder drums for downstream repackaging. Terminal steam sterilization is not applied because autoclave exposure darkens the formulation and increases free silver ion release.
Canine otitis externa caused by Pseudomonas aeruginosa is a reserved application where silver sulfadiazine is compounded at 0.5% w/v to 1% w/v into a nonsterile otic suspension; the vehicle is designed with a carbomer or hydroxyethylcellulose network to retain the active within the vertical ear canal. The formulation is prepared by neutralizing the polymer in a buffered vehicle to pH 4.5–5.5 and adjusting osmolality to 280 mOsm/kg–320 mOsm/kg with glycerol; the silver sulfadiazine slurry is added under low-shear mixing rather than high-shear dispersion because high-shear degrades the polymer network and produces a viscosity drop that cannot be recovered. Antimicrobial activity against Pseudomonas aeruginosa is confirmed by broth microdilution using CLSI M07-A10; microbial quality is tested under Ph. Eur. 2.6.12 and Ph. Eur. 2.6.13, and preservative efficacy under USP <51>. The completed suspension is filled into 10 mL and 20 mL dropper bottles under continuous gentle agitation; fill volume is checked by weighing bottles before and after filling to an in-process limit of ±1.0%. Use is not recommended where tympanic membrane integrity is unknown, because silver sulfadiazine contact with middle ear structures has not been systematically evaluated in canine safety studies. Finished formats include 10 mL dropper bottles, 20 mL dropper bottles, single-use ear syringes, and unit-dose vials for shelter intake protocols.
Granulation into a topical premix is performed when the downstream user requires a free-flowing, dust-controlled wound dressing intermediate for large animal and shelter medicine. The veterinary-grade suspension is first dewatered by vacuum filtration and wet-massed with microcrystalline cellulose, lactose monohydrate, and a polyvinylpyrrolidone binder solution; the wet mass is passed through a 1.0 mm screen and dried in a fluid-bed dryer at a product temperature of 30°C–40°C to a final moisture of not more than 3.0%. The dried granules are milled through a 1.0 mm screen and blended with a glidant before packaging; a 1% w/w silver sulfadiazine label claim is achieved by adjusting the dried granule mass as active water is removed. Release testing includes assay, loss on drying, and microbial limits under USP <61> and USP <62>; elemental impurities are controlled under ICH Q3D, and residual solvents are controlled under VICH GL18. Finished product types include 5 g and 25 g single-use granule packets for direct application to wound beds, 250 g polypropylene jars for clinical use, and bulk drums for secondary repackaging. The granulation process should not include prolonged storage above 40°C or exposure to chloride-containing water, because silver ion release increases and the granule color darkens from white to off-white.
In shelter and field medicine, a 0.05% w/v silver sulfadiazine wound irrigation suspension is prepared from the veterinary-grade API by aseptic dilution into sterile water for irrigation; this format is used for contaminated traumatic wounds where continuous-flow lavage is required before primary closure. Because the active is present as a suspension, terminal 0.22 µm membrane filtration is not applicable; therefore the vehicle and container components are pre-sterilized by autoclaving or aseptic filtration, and the silver sulfadiazine slurry is transferred into the vehicle in a classified ISO 7 environment under USP <797> when a sterile claim is required. Nonsterile versions are prepared under USP <795> and tested for microbial limits by USP <61> and USP <62>. The fill line uses a low-shear magnetic stir bar or recirculating peristaltic pump at 1 L/min to maintain homogeneity, and the fill weight is monitored to ±2.0%. Finished products include 50 mL and 100 mL squeeze bottles, 500 mL irrigation bottles with twist-off caps, and 1 L pour bottles for equine field hospitals.
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Silver Sulfadiazine Suspension Veterinary Grade API is supplied under model designation AgSD-VET-20S as a micronized aqueous dispersion containing 20% w/w silver(I) sulfadiazine, molecular formula C10H9AgN4O2S, CAS 22199-08-2, and molecular weight 357.14 g/mol. The material is intended for further manufacture into tablets, injections, capsules, powders, granules, premixes, and non-aqueous or co-solvent solutions; because silver sulfadiazine is practically insoluble in water, aqueous preparations are suspensions rather than true solutions. The product is manufactured under ICH Q7 for veterinary active pharmaceutical ingredients and is released against a pharmacopoeial monograph that includes identification, assay, related substances, residual solvents, elemental impurities, and microbial limits.
Release testing uses HPLC for sulfadiazine content and complexometric titration for silver after acid digestion. Residual solvents are controlled under USP <467>, elemental impurities under USP <232>/<233>, and non-sterile microbial limits under USP <61>/<62>. For sterile injectable grades, sterility is tested under USP <71> and bacterial endotoxins under USP <85>; the endotoxin acceptance limit is assigned in the approved marketing authorization and is not specified universally.
| Quality attribute | Method | Acceptance criterion |
|---|---|---|
| Appearance | Visual inspection | White to off-white suspension with no agglomerates |
| Assay as sulfadiazine | HPLC, external reference standard | 98.0–102.0% of label claim on dried basis |
| Silver content | Complexometric titration after acid digestion | 98.0–102.0% of theoretical |
| Particle size | Laser diffraction, ISO 13320 | D90 ≤ 20 µm injectable; D90 ≤ 50 µm oral/premix |
| Viscosity | Brookfield RVT, spindle 3, 20 rpm, 25 °C | 800–1200 mPa·s |
| Residual solvents | USP <467> | Class 1 absent; Class 2 within limits |
| Elemental impurities | USP <232>/<233> | Meets oral or parenteral limits |
| Microbial limits | USP <61>/<62> | Meets non-sterile veterinary API limits |
HPLC method validation follows ICH Q2(R1) for specificity, linearity, accuracy, precision, and robustness. Linearity is demonstrated over 80% to 120% of the working concentration; recovery from placebo matrices is targeted at 98.0–102.0% with relative standard deviation not more than 2.0% across six replicates. The method is considered stability-indicating only when forced degradation studies show no co-elution of degradation products with the intact silver sulfadiazine peak.
Silver sulfadiazine is practically insoluble in water, ethanol, and common aqueous parenteral vehicles; therefore the injection is a sterile suspension rather than a solution. Terminal membrane filtration through 0.22 µm filters is unsuitable because the dispersed phase intentionally contains particles larger than the membrane pore size, and aseptic dispersion of sterilized drug and sterile vehicle is required. The suspension for injection is controlled by laser diffraction to D90 ≤ 20 µm, and subvisible particulate matter is evaluated by light obscuration under USP <788> with limits adapted to an inherently particulate dosage form. Attempts to heat-sterilize the finished suspension at 121 °C can cause darkening, silver reduction, and particle aggregation; published data for this specific configuration remains limited, so terminal sterilization is not assigned as a default operation. The vehicle should be free of chloride ions because chloride reduces available silver ion activity and can alter the release profile.
For syringability, the aqueous vehicle is thickened with a non-ionic polymer to a representative viscosity of 800 mPa·s to 1200 mPa·s at 25 °C, measured with a Brookfield RVT using spindle 3 at 20 rpm. Settling is controlled by maintaining a measurable yield stress above 1 Pa; resuspendability after 30 s of manual shaking is a release parameter for multidose containers. Because the injectable grade is particulate, intravenous administration is not appropriate unless the approved label explicitly provides for a specific ultra-fine or filtered presentation; the product is not marketed as an intravenous solution.
For oral solid dosage forms, the micronized suspension is converted to dry powder by spray drying or low-temperature vacuum drying. The resulting powder is blended with lactose monohydrate, microcrystalline cellulose, and 0.5% w/w colloidal silicon dioxide in a high-shear granulator; the silicon dioxide reduces segregation and improves flow. Low-dose tablets and capsules require geometric dilution because the active substance has high density and poor aqueous solubility. Blend uniformity is tested under USP <905> with an acceptance value ≤ 15 for low-dose solid dosage forms, and content uniformity is confirmed on finished units.
The dried powder is milled through a 1.0 mm screen and controlled to a bulk density of 0.35 g/mL to 0.60 g/mL and a Carr index below 25. Capsule filling on dosator or tamping-pin machines proceeds without excessive powder sticking when moisture is maintained below 2.0% w/w. Tablet compression is performed on a rotary press with tooling designed for dense, poorly compressible granules; precompression force and turret speed are adjusted to avoid lamination and capping.
Granulation and drying are constrained by light sensitivity. In fluid-bed drying, inlet air temperature is maintained at 50 °C to 60 °C, and the granulate is protected from direct sunlight. Higher temperatures or exposure to ultraviolet light cause surface darkening and may generate elemental silver. Batch-to-batch variation is reduced by sieve analysis of the dried granulate at 250 µm and 850 µm; oversized material is rejected or milled under low-shear conditions. Dissolution testing for tablets uses USP <711> apparatus II; because of low solubility, a surfactant-containing medium is required to maintain sink conditions.
For premix and granule applications, the API is incorporated into a carrier such as lactose monohydrate or calcium carbonate by geometric dilution. The final feed concentration is determined by the approved veterinary label; a representative working range of 10 mg/kg to 100 mg/kg requires a premix concentration of 1% w/w to 10% w/w to allow metering accuracy. Premix homogeneity is assessed by sampling at 10 locations across a ribbon blender or paddle mixer and analyzing sulfadiazine by HPLC, with acceptance limits of 90.0–110.0% of label claim. Dust control and containment are required because micronized silver sulfadiazine may become airborne and requires local exhaust ventilation. Sampling plans for animal feeding stuffs follow ISO 6497.
Batch records document mixer speed, mixing time, and discharge sequence. Because silver sulfadiazine is denser than some carriers, extended mixing can increase segregation rather than improve uniformity; mixing time is therefore established by a blend uniformity protocol rather than fixed arbitrarily. Published data for this specific formulation configuration is limited, so pilot-scale blending studies are required before production-scale release. Metering accuracy is confirmed with a loss-in-weight feeder and a target feed rate variation below 2% relative standard deviation.
Compared with silver nitrate, silver sulfadiazine releases silver ion more slowly because silver is coordinated to the sulfonamide and pyrimidine nitrogen atoms. Silver nitrate is freely soluble and generates a rapid burst of free silver ions that can precipitate immediately as silver chloride in chloride-containing biological fluids; silver sulfadiazine has lower free silver ion activity, which reduces immediate precipitation and prolongs oligodynamic action. Silver chloride is very slightly soluble and releases silver ion at a rate that is often too low for therapeutic value; silver sulfadiazine occupies an intermediate release position without requiring nitrate anions. Organic antibacterial APIs act through specific bacterial target inhibition, whereas silver sulfadiazine combines silver ion disruption with sulfadiazine inhibition of dihydropteroate synthase; selection pressure and residue behavior therefore differ.
| Comparative parameter | Silver sulfadiazine | Silver nitrate | Silver chloride | Organic antibacterial API |
|---|---|---|---|---|
| Water solubility | Practically insoluble | Freely soluble | Very slightly soluble | Variable |
| Free silver ion release rate | Slow, ligand-controlled | Rapid, ionic | Very slow | No silver release |
| Behavior in chloride-containing media | Reduced immediate silver chloride precipitation | Immediate silver chloride precipitation | Already chloride salt | Not applicable |
| Primary resistance mechanism | Silver efflux, silver reduction, target enzyme mutation | Silver efflux | Silver efflux | Beta-lactamase or other target-based resistance |
| Typical processing route | Micronized suspension; dry powder by low-temperature drying | Aqueous solution compounding | Dispersion or topical | Variable depending on molecule |
Silver sulfadiazine is not interchangeable with sulfadiazine sodium or sulfadiazine base. Sulfadiazine sodium is freely soluble and is used for intravenous solutions, whereas silver sulfadiazine is practically insoluble and releases silver ions. Sulfadiazine base provides only the folate inhibition component; the silver complex adds an oligodynamic mechanism that alters the residue and toxicity profile.
pH is maintained between 4.5 and 6.5 with a non-buffering pH modifier. Below 4.5, silver complex dissociation increases and sulfadiazine may precipitate; above 6.5, silver oxide or silver carbonate may form at the particle surface. The suspension is therefore formulated with a preservative that is compatible with silver ions; benzalkonium chloride is avoided because of chloride incompatibility and adsorption onto silver particles. Published data for this specific configuration is limited, so preservative efficacy is confirmed by USP <51> rather than assumed from preservative concentration.
The degradation pathway in aqueous suspension is primarily photolytic; light exposure produces silver metal and oxidatively degraded sulfadiazine species. Therefore, packaging light transmission is controlled by using amber high-density polyethylene or type III amber glass, and storage trials include light stability under ICH Q1B conditions where applicable to veterinary products.
Storage of the veterinary grade suspension requires protection from light, humidity, and freezing. The suspension is filled into amber high-density polyethylene containers or type III amber glass with polypropylene closures; storage temperature is maintained at 15–30 °C. Freezing causes irreversible particle aggregation and should be avoided. Chloride-containing diluents are incompatible because they reduce available silver ion activity; only purified water or a specified non-ionic vehicle should be used for dilution. The product should not be combined with reducing agents, aldehydes, or amine-based additives because these can precipitate elemental silver and decrease potency. Resuspendability is verified after 30 s of manual shaking, and viscosity at 25 °C is controlled between 800 mPa·s and 1200 mPa·s to maintain uniformity during dispensing.
When the suspension is transferred into compounding tanks or filling lines, stainless steel surfaces should be passivated and light exposure should be minimized. Contact with monel, copper, or uncoated carbon steel can cause galvanic deposition of silver; the manufacturing line is therefore restricted to 316L stainless steel or polymeric contact parts. Cleaning validation under 21 CFR 211.67 uses swab and rinse sampling with a maximum allowable carryover calculated from toxicological data; no universal acceptance limit is assigned without product-specific safety information.
