Sanhuang Powder Veterinary Grade API is a dry, multi-component botanical extract intended for downstream formulation into tablets, injections, capsules, powders, granules, premixes, and solutions. Manufacturer model designations are not harmonized across the industry; a representative internal code may appear as SHP-VG-API-01, but the Chinese Veterinary Pharmacopoeia does not assign a uniform model number. The powder is standardized from Rhei Radix et Rhizoma, Scutellariae Radix, and Phellodendri Chinensis Cortex, and its analytical identity rests on marker compounds from three chemical classes: baicalin, berberine hydrochloride, aloe-emodin, rhein, and chrysophanol. Thin-layer chromatography against chemical reference substances and high-performance liquid chromatography with diode-array detection are used for identity and assay; because botanical raw material varies with geographic origin, marker content is normalized to a manufacturer-specific fingerprint rather than a single absolute percentage.

Dry powder specifications are set separately for oral granule, premix, and injection grades because downstream processing imposes different limits. A representative release profile for non-sterile oral and premix material is shown in Table 1. Residual moisture is controlled because the API is hygroscopic; at relative humidity above 60%, open handling can increase moisture by 1.0–2.0% within 30 min, causing clogging of sieve screens and erratic capsule filling. In production, transfer is conducted in closed systems with nitrogen or dehumidified air at ≤40% RH.

Dosage form compatibility and process integration

Tablet manufacture from the API is conducted by either direct compression or wet granulation. Direct compression requires a pre-blend with microcrystalline cellulose, croscarmellose sodium, and colloidal silicon dioxide because the botanical powder exhibits cohesive flow in an annular shear cell; flow function coefficient values below 5.0 are classified as cohesive under ASTM D6773. Where direct compression is not feasible, high-shear wet granulation with purified water or a 5–10% povidone K30 solution is used, followed by fluid-bed drying at 50–60 °C to a final granule moisture of 2.0–3.5%. Compression on a rotary tablet press is typically run at 40–80 rpm using 10–25 kN compression force, with friability tested according to USP <1216> at a limit of ≤ 1.0%. Aqueous film coating may be applied with an 8–12% solids dispersion of hydroxypropyl methylcellulose and polyethylene glycol; pan inlet air temperature is held at 60–70 °C, and bed temperature at 38–42 °C to reduce surface friability without increasing core moisture.

Capsule filling of the milled API after sieving through a 250 µm screen is performed on a dosator or tamping-pin encapsulation machine. Fill weight variability is controlled by monitoring the coefficient of variation of fill mass; for botanical powders, a batch limit of 3.5% relative standard deviation is used when the powder is pre-blended with 0.5–1.5% colloidal silicon dioxide. Dissolution testing, where required, uses a USP <711> type II paddle apparatus at 50 rpm in 900 mL of pH 1.2 medium for immediate-release solid dosage forms, with marker sampling at 45 min rather than a single time point because the anthraquinone and flavonoid markers release at different rates.

Granules and oral powders are prepared by dry blending with dextrose or lactose monohydrate followed by low-shear mixing in a ribbon blender. Published data for scale-independent mixing of this specific botanical extract are limited; therefore blending time is established by sampling at 10 positions and assaying the baicalin marker until the relative standard deviation falls below 5.0%. The resulting mixture is packaged in aluminium-laminated sachets to prevent moisture gain and photodegradation of berberine.

On production-scale direct-compression lines, the principal failure mode is irregular screw feeding. When the API is loaded directly into the hopper without an antistatic pre-blend, rat-holing and bridging are observed on a gravimetric screw feeder with a 30 mm open auger; this causes feeder mass flow variability up to ±12% at 20 kg/h output. The corrective action is pre-blending with 1.0% w/w fumed silica and restructuring the hopper to a 70° cone angle.

Why does the premix route require particle size control below 180 µm?

Feed premix homogeneity is governed by particle-size overlap between the API and the feed carrier. If the API D90 exceeds 180 µm, demixing during pneumatic conveying and auger metering produces assay variation exceeding 15% relative standard deviation in finished feed. The API is therefore air-jet milled or impact milled to a D90 below 180 µm, with particle size distribution verified by laser diffraction according to ISO 13320:2020 under a dry dispersion pressure of 2.0 bar. The milled powder is then diluted with calcium carbonate or rice hull carrier to a final premix concentration appropriate for on-farm dosing; batch uniformity is confirmed by near-infrared reflectance spectroscopy calibrated against HPLC assay.

Premix production on a horizontal ribbon blender with 1500 L working capacity is limited to 70–80% fill volume because the cohesive API/carrier blend can override the ribbon shaft at higher fills. Mixing at 18–22 rpm for 20–30 min typically achieves marker uniformity below 5% relative standard deviation; longer mixing times are not used because electrostatic charging increases segregation after discharge. Segregation potential is measured using a sifting segregation tester in accordance with ASTM D6940, with the acceptable segregation index set below 10% for the primary marker. Storage is restricted to dry carriers with water activity below 0.60 at 25 °C; when feed moisture exceeds 14.0%, berberine migration into the feed matrix reduces aqueous-methanol extraction recovery by 3–8% in quality-control assays. Sealed aluminium-laminated bags with desiccant are specified for bulk packs.

Oral solutions and drinking-water formulations are prepared from a water-dispersible grade by addition of pH 6.0–7.5 purified water and a preservative system such as sodium benzoate at 0.1–0.2%. The solution is filtered through a 5 µm clarification cartridge before filling. Published data for this specific configuration are limited; therefore each lot is checked for sediment after 72 h at 25 °C and 2–8 °C to confirm physical stability.

When injection-grade aqueous solutions require bacterial endotoxin control

Injectable solutions are not manufactured by simple dissolution of the oral-grade powder. The API must be subjected to aqueous extraction, centrifugation, and activated carbon adsorption to remove high-molecular-mass polysaccharides, proteins, and endotoxin. A clarifying filtration step with a 0.45 µm polyethersulfone cartridge precedes depyrogenation; terminal sterilisation is performed by autoclaving at 121 °C for 15 minutes or by passage through a 0.22 µm sterilising-grade filter with bacterial retention validation per ASTM F838-20. Bacterial endotoxin release is controlled against a product-specific limit calculated from dose volume and animal body weight; a frequent starting specification is <0.50 EU/mg, but the final limit must be justified for the target species and route of administration.

The aqueous injection vehicle is maintained at pH 5.5–7.5. Outside this range, baicalin-related flavonoids precipitate as pale yellow agglomerates after 24–48 h at 2–8 °C, and berberine hydrochloride may crystallise at pH above 8.0. Citrate or phosphate buffers are added before final volume adjustment, and the finished solution is stored in amber glass vials because light exposure reduces berberine marker recovery. For parenteral use in food-producing species, preservative selection must also be justified against maximum residue limits. Benzyl alcohol is generally excluded from injectable formulations for food animals due to residue concerns; where necessary, the depletion profile of benzyl alcohol is established in the target species. The API manufacturer provides residual solvent and elemental impurity statements to support the formulation dossier.

Comparative evaluation against single-molecule veterinary drug APIs shows three operational differences. First, the analytical target is not a single chromatographic purity value but a multi-marker area ratio; batch acceptance is typically set at 80–120% of the reference fingerprint for the primary markers. Second, residual solvent control differs from synthetic antibiotics: ethanol and water are the main process solvents, and residual ethanol is controlled under USP <467> with a class 3 limit of 5000 ppm, whereas synthetic APIs may require chlorinated solvent monitoring. Third, the particle surface of the botanical API is more sensitive to moisture and static charge, requiring closed handling and bonded/grounded equipment in areas with relative humidity above 50%.

Veterinary-grade material differs from human-use botanical extracts in that the microbial acceptance limits follow veterinary dosage form risk assessments and the ash content may be broader. The API is released under veterinary GMP documentation with batch-specific certificates of analysis covering mycotoxins and pesticide residues where the botanical source country requires it. Because animal species differ in gut transit time and gastric pH, dissolution or release specifications for the API are not directly transferable from human pharmacopoeial monographs; manufacturer data packages should be reviewed for the target species.