Bazheng Powder Veterinary Grade API, product code BZP-VG-API-PF-011, is a standardized multi-botanical active pharmaceutical ingredient derived from eight botanical and mineral materials: Dianthi Herba, Plantaginis Semen, Polygonum aviculare Herba, Akebiae Caulis, Gardeniae Fructus, Rhei Radix et Rhizoma, Talcum, and Glycyrrhizae Radix et Rhizoma. The powder is supplied as a pale yellow to brownish fine powder with a characteristic aromatic odour and is intended solely as an input to licensed veterinary medicinal product manufacture. The API is manufactured for further processing into 7 presentation types: tablets, injections, capsules, powders, granules, premixes, and oral solutions. The material is not a simple crude herb mixture; manufacturing includes dry cleaning, comminution, sieving through an 80-mesh screen with nominal aperture 0.180 mm, homogenization in a 2000 L double-cone blender, and final metal detection at 1.5 mm ferrous, 2.0 mm non-ferrous, and 2.5 mm stainless steel sensitivity.

Three physical grades are supplied under the same chemical specification. The standard grade PF-011 is used for tablets, capsules, powders, and granules. The fine grade F075 is milled for extraction-based liquid dosage forms. The P150 grade is used for premix blending with feed carriers. All grades are released against a certificate of analysis that includes identity, appearance, loss on drying, total ash, acid-insoluble ash, heavy metals, arsenic, total aerobic microbial count, Escherichia coli, Salmonella, and particle-size distribution. The batch designation includes the manufacturing year and a sequential lot number; the product is not released for direct administration to animals.

For solid dosage form developers, the most consequential property is powder flow behaviour. The API exhibits a Carr’s compressibility index of 28–34% and a Hausner ratio of 1.35–1.45, indicating poor to passable flow. Without a glidant, segregation and weight variation exceed acceptable limits on rotary tablet presses. Colloidal silicon dioxide at 0.5–1.0 wt% reduces flow time through a 10 mm orifice to below 20 s/100 g. Production-scale observations on a 16-station rotary press with 10 mm round tooling indicate that a formulation containing 40 wt% API, 45 wt% microcrystalline cellulose, 10 wt% sodium starch glycolate, 4 wt% copovidone, and 1 wt% magnesium stearate produces tablet hardness of 70–90 N and friability below 1.0% when the API lot D90 is below 125 µm.

What limits the direct-compression behaviour of the granulation-grade API?

Particle-size distribution is the first controlling variable. Laser diffraction data obtained according to ISO 13320:2020 using dry dispersion at 3 bar define three grades. For standard PF-011, the D10 is 12–18 µm, the D50 is 48–65 µm, and the D90 is 110–140 µm. If the D90 exceeds 140 µm, tablet tools show visible punch filming within 30 min of continuous operation, and content uniformity RSD increases above 5.0%. For capsules, a D10 below 8 µm creates static adhesion to gelatin and hypromellose shells, causing fill weight drift. For injection precursor use, the F075 grade is milled to D90 65–75 µm and extracted with purified water at 90–95°C for 1 h; the extract is then filtered through 0.45 µm and 0.22 µm polyethersulfone membranes prior to aseptic filling. The dry powder must not be represented as injectable; it is only an extraction feedstock for sterile processing.

In premix manufacture, the P150 grade is blended with ground corn cob or rice hulls in a ribbon mixer. The particle-size overlap between API and carrier must be within 30% of the carrier D50; otherwise the API migrates to the bottom of the mixer during discharge. In mixer validation using a 500 kg ribbon mixer, samples collected at 10 time points during unloading had relative standard deviation below 5.0% only when the carrier D50 was 450–600 µm and the API D50 was 70–90 µm. If the carrier D50 exceeds 800 µm, the coefficient of variation increases to 8–12%.

Analytical Release Specification and Residual Contaminant Thresholds

The registered specification below is aligned with general methods of the Chinese Pharmacopoeia 2020 and the heavy-metal procedure of Ph. Eur. 2.4.8. The exact limits must be confirmed against the product licence because individual target species may require lower residue values.

For the extraction grade used in injectables, endotoxin control is applied to the aqueous extract rather than the dry API. The extract is tested by Limulus amoebocyte lysate assay with an acceptance limit of <0.5 EU/mL for the diluted solution before filling. The dry powder itself is not depyrogenated; terminal sterilisation of the filled solution by autoclaving at 121°C for 15 min is acceptable only if stability data confirm that geniposide and rhein retention remain above 95% at release. Published data for this specific herbal injection configuration is limited; therefore, batch-specific process validation is required before commercial use.

The powder is hygroscopic above 60% relative humidity. Unprotected storage for 48 h at 25°C and 75% RH can increase the loss on drying from 7.2% to 9.8% and initiate caking in the P150 premix grade. Primary packaging is therefore an aluminium foil laminate with a moisture vapour transmission rate less than 0.1 g/m²/day at 38°C and 90% RH. Reprocessing of caked API by re-milling is not recommended because the talc component redistributes and the anthraquinone-containing particles may generate heat-labile fines. Moisture control is equally critical during wet granulation; the granulation end-point is set at a product temperature of 40–45°C and a final granule loss on drying not exceeding 5.0%. Overdrying below 3.0% increases granule friability and can promote segregation of the denser talc-containing fraction.

When a Veterinary API Diverges from Feed-Grade Bazheng Powder

Feed-grade botanical powders are frequently sold on visual identity and a crude marker-herb check; they may carry total aerobic plate counts up to 100,000 CFU/g, and they are not released under drug GMP. The veterinary API differs in four measurable ways. First, identity is confirmed by thin-layer chromatography and HPLC fingerprint similarity against the reference extract; a similarity index below 0.90 is cause for rejection. Second, heavy metals are controlled to ≤20 mg/kg and arsenic to ≤2 mg/kg, whereas feed-grade material may not carry a per-lot limit. Third, the microbial specification for the API is tighter than feed grade: total aerobic count is ≤10,000 CFU/g, and Salmonella is absent in 10 g. Fourth, the particle-size distribution is controlled and reported by laser diffraction, while feed-grade powders are typically sold by mesh designation only. The veterinary API also differs from human-grade Bazheng San because the residual solvent and heavy-metal thresholds are adjusted for animal-specific metabolic and tissue residue considerations, and the extraction grade is standardized for the manufacture of registered veterinary solutions rather than decoction pieces.

Compared with a synthetic loop diuretic such as furosemide, the API does not contain a single active molecule with a defined renal tubule target; it is a polychemical mixture that requires species-specific dose-setting and should be used as adjunctive therapy in urinary tract inflammatory conditions. The onset of action is not equivalent to that of a parenteral loop diuretic, and the material cannot be substituted on an equal-mass basis.

Thermal and Moisture Constraints in Multi-Botanical Blends

Wet granulation is the preferred processing route for tablets because the powder has poor direct-compression flow. In a high-shear granulator with impeller speed 200–300 rpm and chopper speed 1500 rpm, purified water is sprayed at 80–120 mL/min until the torque reaches 12–15 N·m. The wet mass is discharged through a 2.0 mm screen and dried in a fluidized-bed dryer with inlet air at 60°C and product temperature not above 45°C. Drying to a loss on drying of 4.0–5.0% provides acceptable hardness and disintegration; over-drying below 3.0% causes lamination during compression. The talc component acts as an internal lubricant but also contributes acid-insoluble ash; the acid-insoluble ash limit of ≤2.0% therefore includes the talc fraction and must be interpreted in the context of the formula.

For injectable-grade extraction, the decoction is concentrated under vacuum at 60°C to a relative density of 1.10–1.15 at 20°C, then filtered through 0.45 µm and 0.22 µm membranes. The pH is adjusted to 4.5–5.5 to maintain anthraquinone solubility; final sterilisation may be by autoclaving at 121°C for 15 min only where the registered stability data support marker retention. The solution is tested for particulate matter according to USP <788> and for bacterial endotoxin according to Ph. Eur. 2.6.14. The API should not be combined with strong oxidizing acids or alkaline processing aids above pH 8.5, because the anthraquinone components precipitate as aglycone salts in alkaline solution. Solutions containing calcium or magnesium ions should be avoided unless chelation is incorporated; these ions can form insoluble complexes with constituents of the botanical matrix and reduce the recovery of marker compounds.

The intended clinical use of finished products containing this API is adjunctive management of lower urinary tract inflammation, cystitis, and urolithiasis in swine, cattle, poultry, and companion animals. The API is not a finished product and must not be administered directly. Dosage is species-specific and must be derived from the registered veterinary medicinal product monograph; no universal dosage can be stated across formulations because extraction ratio, marker standardization, and excipient loading alter the final exposure. In oral solution manufacture, the extraction ratio is typically 10:1 or 20:1 crude-to-extract; the final solution may contain preservatives selected to avoid incompatibility with the herbal matrix. In premix formulations, the API is dispersed onto a feed carrier at 5–20 wt% before dilution into complete feed to avoid sorting and to maintain a coefficient of variation below 5.0% in mixer validation studies. Capsule filling on an automatic dosator machine requires pin setting adjustment; the static charge of the powder is reduced by controlling room humidity to 45–55% RH and adding 0.5% sodium stearyl fumarate. Without humidity control, capsule shell cracking occurs due to moisture transfer from the shell to the hygroscopic API. For tablet cores containing more than 45 wt% API, the talc and mineral fraction increases ejection force; punch tip hardness should be at least 62 HRC, and tooling wear becomes measurable after 200,000 compressions. If the API is added at 50 wt% or higher, disintegration time may exceed 30 min in 0.1 M hydrochloric acid, requiring a higher proportion of sodium starch glycolate or crospovidone.