Compound Sulfachlorpyrazin Sodium Premix Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions is a water-soluble sulfonamide active substance supplied as a crystalline or spray-dried powder for downstream veterinary pharmaceutical manufacturing. The material is differentiated by salt form, particle-size distribution, bulk density, and residual-solvent profile. The sodium salt of sulfachlorpyrazine is produced by neutralization of the free sulfonamide with sodium hydroxide; the resulting API provides a solution pH of 8.0–10.0 at 10% w/v in water and is intended for direct dissolution in liquid premixes or aqueous granulation. Because the substance is not assigned a single harmonized monograph in Ph. Eur. or USP, release testing follows validated manufacturer methods aligned to Ph. Eur. 2.2.24, 2.2.29, and VICH GL18. Manufacture is performed under GMP controls aligned to 21 CFR 210, 21 CFR 211, and EU GMP Part 4. Typical trade-grade models include a micronized grade with D90 ≤ 20 µm for suspension and injection, a standard crystalline grade with D90 ≤ 75 µm for feed premix and granules, and a granulated direct-compression grade with bulk density 0.45–0.65 g/cm³ and D50 120–180 µm for tablets. The active substance is suitable for dry blending, wet granulation, direct compression, and aseptic solution preparation when the appropriate physical grade is selected.

The sodium content of the salt is reported on the certificate of analysis because it affects the salt-to-free-acid conversion when label strength is expressed as sulfachlorpyrazin base. The manufacturer should state the conversion factor, the hydration state, and the particle-size method. Material intended for drinking-water premixes requires dispersibility testing with a 0.45 mm screen; the dispersion should pass through the screen without residue when added to water at 20–25 °C under 60–120 rpm stirring in a stainless-steel vessel.

Why does the sodium salt form change aqueous dissolution and blend uniformity in low-dose formulations?

The free acid of sulfachlorpyrazine is sparingly soluble in water; sodium-salt formation increases aqueous wetting and dissolution rate. This changes manufacturing logic for tablets, capsules, powders, granules, premixes, and solutions. Aqueous granulation with starch or povidone at binder temperatures 20–25 °C is preferred, but the API should not be pre-blended with acidic excipients such as ascorbic acid or citric acid before the granulation fluid is added. Local pH depression can precipitate the free acid and reduce dissolution in the finished dose form. In production-scale ribbon mixers and high-shear granulators, segregation of micronized API from coarse carriers is the dominant blend-uniformity failure mode. A two-step geometric dilution sequence with lactose monohydrate or calcium carbonate is therefore used before final blending. Blend uniformity is assessed by sampling 10 locations and testing by HPLC with a relative standard deviation ≤ 5.0% according to USP <905>.

At residual moisture above 1.0%, the sodium salt becomes tacky and can produce tablet capping or capsule-shell softening in gelatin and hypromellose capsule systems. Dry granulation by roller compaction is only feasible when the relative humidity is maintained below 60% and the powder temperature is kept below 30 °C; otherwise the material adheres to the rolls and requires repeated scraper adjustment. Direct-compression formulations usually require a silicon dioxide glidant at 0.5–1.0% w/w and magnesium stearate at 0.25–0.75% w/w to manage flow and ejection force on rotary tablet presses. Tablet hardness is typically adjusted to 60–80 N for immediate-release products; friability is controlled at ≤ 1.0% after 100 rotations per Ph. Eur. 2.9.7.

Specification profile for batch release under veterinary pharmacopoeial alignment

The release panel in the table below is applied to each incoming batch before use in finished veterinary medicine production.

Heavy metals are controlled using Ph. Eur. 2.4.8 with a limit of ≤ 10 ppm. The limit applies to the oral and premix grades; injectable grades are subject to additional particulate-matter control after dissolution, using light obscuration at 25 µm and 10 µm channel sizes according to Ph. Eur. 2.9.19. Depending on the manufacturing route, the residual-solvent method should also monitor N,N-dimethylformamide as a class 2 solvent at ≤ 880 ppm if it is used in the final crystallization step. The analytical method for related substances is typically a reversed-phase C18 column 250 × 4.6 mm, 5 µm, with a phosphate buffer pH 3.0 and acetonitrile gradient at 40 °C, detection at 270 nm. System suitability requires resolution of sulfachlorpyrazin sodium from sulfanilamide of ≥ 2.0 and tailing factor ≤ 1.5.

Manufacturing of the premix intermediate from the API typically proceeds by dry blending with calcium carbonate or lactose carrier in a paddle or ribbon mixer operating at 10–15 rpm and 50–70% working volume. The API is screened through a 710 µm sieve before loading to remove agglomerates. Spray-dried material with a tapped density of 0.35–0.55 g/mL is preferred when the premix is to be finely dispersed in drinking-water systems, because faster wetting in stainless-steel tanks reduces nozzle clogging. Stability is assigned in tight polyethylene containers at 25 °C ± 2 °C and 60% RH ± 5% following long-term and accelerated protocols under VICH GL3. Observed failure modes under humidity stress include discoloration at 75% RH and agglomeration when the container is left open for more than 24 h in uncontrolled bulk-handling rooms. For solution products, the premix is dissolved in potable water or water for veterinary use; the solution should be used within 24 h because sulfonamide sodium salts can undergo photodegradation and microbial growth in non-sterile drinking-water systems.

When the API grade is intended for injectable solutions, what particle-size and endotoxin constraints apply?

Injectable formulations require the micronized grade with D90 ≤ 20 µm and endotoxin ≤ 0.5 EU/mg. The API is dissolved in water for injection at 20–25 °C; the solution is then passed through a 0.45 µm polyethersulfone filter followed by a 0.22 µm sterilizing filter. The sodium salt should be added slowly to the aqueous vehicle to avoid transient pH gradients above 10.5, which can accelerate hydrolysis of the sulfonamide linkage. In aseptic filling lines, the fill solution should be protected from light because photodegradation produces colored degradation products that are detected by HPLC as late-eluting peaks. Terminal sterilization by autoclave at 121 °C for 15 min is only suitable if the finished-product stability data support the impurity profile; published data for this specific configuration is limited and formulation-specific validation is required under VICH GL2.

Cleaning residue limits for the API in multi-product veterinary manufacturing lines are derived from a toxicologically acceptable daily intake calculation and expressed as a maximum allowable carryover of 10 ppm in the next batch. Swab sampling of stainless-steel, glass, and flexible polymer contact surfaces is performed after wet cleaning with 0.1 mol/L sodium hydroxide solution. The analytical method is HPLC with a limit of quantitation ≤ 0.1 ppm in swab extract. Because the sodium salt is hygroscopic, flushing with dry nitrogen is used before returning equipment to service.

Differences from other sulfonamide sodium salts in downstream manufacturing

The pyrazine substituent in sulfachlorpyrazin sodium alters chromatographic retention and solid-state stability relative to the pyrimidine and pyridazine sulfonamide salts. The comparison below lists typical working ranges observed in formulation development; the manufacturer’s certificate should be used for exact batch values.

The principal formulation difference is that the pyrazine ring of sulfachlorpyrazin sodium gives a larger polar surface area than the pyrimidine ring of sulfadiazine sodium. This shifts the reversed-phase HPLC retention time and requires a specific related-substances method to resolve sulfanilamide and early-eluting process impurities. In feed premixes, the compound is often chosen when the finished product must disperse rapidly in drinking water; however, published comparative tissue-residue depletion data for this specific configuration is limited. Withdrawal periods for target species must be established by marker residue studies under VICH GL48, and extrapolation from sulfadiazine sodium or sulfaquinoxaline sodium is not permitted without bridging pharmacokinetic data.

The API must be stored in double low-density polyethylene liners inside a sealed HDPE drum at 25 °C ± 2 °C and 60% RH ± 5%. After opening, the working stock should be consumed within 72 h or transferred to a desiccator with silica gel. The sodium salt is incompatible with strong oxidizing agents and with concentrated acids; acidification below pH 7.0 precipitates the free acid and should be avoided in solution preparation. Handling operations that generate dust should use local exhaust ventilation and dust-tight transfer systems because the dry powder is a respiratory and contact irritant. The compound should not be directly blended with amine-based excipients unless compatibility has been demonstrated by forced degradation at 40 °C / 75% RH for 14 days; otherwise premature discoloration may occur.