Direct compression of Sanwei Quanshen Oral Solution Veterinary Grade API into piglet enteric tablets is governed by the water budget of the wet mass rather than by the active fraction alone. When the liquid extract is received at a dry-matter content of 20–30% w/w, the initial unit operation is vacuum-assisted evaporation at 50–60 °C jacket temperature under -0.08 MPa to -0.09 MPa until the concentrate reaches 60–65% solids. The concentrate is then sprayed onto a premixed carrier of microcrystalline cellulose 101 and dibasic calcium phosphate dihydrate at a carrier ratio of 1.0:0.35 in a high-shear granulator fitted with a side chopper operating at 1,500 rpm. Aqueous fractions containing gallotannins and condensed tannins can reduce tablet breaking force by forming weak hydrogen-bonded films around dried particles when moisture after granulation exceeds 7%; therefore fluid-bed drying at 60 °C inlet air with a dew point not higher than 4 °C is applied until loss on drying reaches 2–3%. Lubrication is limited to 0.4% sodium stearyl fumarate because magnesium stearate at 1% may reduce breaking force below 60 N on a 10 mm round concave tool. Compression is performed on a 24-station rotary press with pre-compression 5 kN and main compression 10–12 kN. The resulting tablets are tested per USP 905 uniformity of dosage units and USP 701 disintegration in 0.1 N hydrochloric acid at 37 °C, with a target disintegration time not exceeding 15 min when a 2% w/w hydroxypropyl methylcellulose film is applied from aqueous coating suspension. The terminal product is a 500 mg oral tablet for swine, individually sealed in aluminum foil blister with a water vapor transmission rate below 0.5 g/m²/day.

What Limits Terminal Sterilization of the Aqueous Extract in Multi-Dose Vials?

Conversion of the liquid extract into an injectable dosage form is constrained by the absence of published thermal destruction data for the specific triterpenoid glycoside and polyphenolic profile at vial scale. The three-herb extract in Sanwei Quanshen Oral Solution—Bistortae rhizoma, Potentillae discoloris herba, and Pulsatillae radix—contains heat-labile protoanemonin-derived constituents and tannin fractions that may darken and precipitate when saturated steam is applied. Consequently, terminal autoclaving is not selected as the default sterilization route. After cold centrifugation at 8,000–10,000 × g at 2–8 °C, the liquid API is diluted to 5% total solids with Water for Injection and passed sequentially through 0.45 µm and 0.22 µm polyethersulfone membrane cartridges with a filtration area of 0.6 m² per 200 L batch. Filter integrity is confirmed by bubble point or diffusional airflow method before filling. The pH is adjusted to 6.0–6.5 with 10 mM citrate buffer, and benzyl alcohol at 1.5% v/v is incorporated only for multi-dose presentations; single-use ampoules omit the preservative. Tonicity is adjusted to 280–320 mOsm/kg and confirmed per USP 785. Aseptic filling is conducted in an EU GMP Grade A zone within an ISO 14644-1 cleanroom, followed by sterility testing per USP 71 and bacterial endotoxin testing per USP 85. The finished injectable is a 50 mL or 100 mL Type II amber glass vial with nitrogen overlay and FluroTec-coated stopper. The absence of terminal steam sterilization imposes stricter pre-filtration bioburden control, documented per 21 CFR 211.110 in-process sampling, and the batch is released only after sterility and endotoxin criteria are met.

Spray-dried conversion of the oral solution API into capsule-grade powder is constrained by the glass transition temperature of co-extracted oligosaccharides and by the gelatin-crosslinking tendency of the tannin fraction. Hard gelatin capsules are replaced by HPMC capsules when the fill moisture exceeds 4.5% or when storage relative humidity exceeds 55%, because tannin–gelatin interaction can delay disintegration beyond USP 2040 limits. The liquid is first vacuum-concentrated to 50% solids, then spray-dried with 15% maltodextrin DE 10–12 and 5% colloidal silicon dioxide as a moisture-scavenging carrier. A co-current spray dryer with rotary atomizer is operated at inlet 170 °C and outlet 70–80 °C, yielding a powder with moisture 4–5% and bulk density 0.35–0.45 g/cm³. The spray-dried intermediate is blended with lactose monohydrate 20%, sodium starch glycolate 0.5%, and talc 1% in a bin blender at 12 rpm for 15 min. Capsule filling is performed on a dosator-type machine to a target fill weight of 250 mg; weight variation is assessed per USP 905, and water content is determined by Karl Fischer titration per USP 921. The terminal veterinary capsule is a 250 mg HPMC shell packed in PVC/PVDC blister with desiccant because the powder has a critical relative humidity below 50%. The capsule route is suitable for companion-animal and calf administration when solid oral dosage forms must resist moisture uptake in tropical distribution lanes.

Aqueous Drinking-Water Powders and Their Moisture-Dependent Caking Threshold

Direct adsorption of the liquid API onto a porous carrier yields a water-dispersible powder for mass medication through poultry drinking lines. The formulation is built from 40% w/w spray-dried glucose carrier, 3% sodium citrate buffer, 1% colloidal silica, and the oral solution API solids required to meet the label claim; the liquid is applied by top-spray fluidized-bed coating at inlet air 55–60 °C, atomizing air 1.5 bar, and bed temperature 30–35 °C. After drying, the powder is passed through a 250 µm stainless-steel sieve to remove agglomerates before filling into laminated foil sachets. The critical caking threshold is moisture-dependent: when moisture exceeds 5%, amorphous sugar bridging reduces the flow function coefficient below 4, causing ratholing in bulk bags and bridging at the dispenser inlet. Therefore loss on drying is controlled to 2–3% per USP 731, and the sachet seal is validated for water vapor transmission below 0.3 g/m²/day. The terminal product is a 100 g or 1 kg water-soluble powder sachet for poultry, piglet, and calf drinking-water administration; the powder is dissolved in water at 1:500 to 1:1,000 depending on the prescribed dose per kg body weight.

Granulation onto coarse dextrose monohydrate for in-feed top dressing avoids the compressibility loss seen in direct compression but introduces segregation at fill weights below 50 g. In this route, the oral solution API is used as the granulating liquid after viscosity adjustment to 100–200 mPa·s with pre-gelatinized starch at 2% w/w. The liquid is sprayed onto a 5 kg bed of dextrose monohydrate and corn starch in a fluid-bed granulator with inlet air 55–65 °C, product temperature 30–35 °C, and spray rate 50–80 g/min. Granules are dried to 2–3% moisture and sieved between 0.5 mm and 1.0 mm; overs are milled through a cone mill at 1,000 rpm and re-granulated to avoid yield loss. The finished granule is a 25% w/w extract granule for piglet creep feed or poultry top dressing, packed in paper sacks with a 0.5 mm polyethylene liner. A stressed shelf-life check at 40 °C / 75% RH in open trays for 7 days is used to confirm no darkening or clumping beyond 10% moisture regain; this is not a full stability study but a batch-release control against capillary caking in high-humidity feed barns.

When a 5% Medicated Premix Is Discharged From a Double-Ribbon Mixer Under Assay RSD 5%

Premix manufacture is the highest-risk dilution step because the liquid API cannot be sprayed directly into final feed without first being fixed onto a carrier. The carrier is selected to avoid free iron in bentonite or certain clay fractions because the tannic constituents form dark iron–tannate complexes that can reduce assay recovery by 3–7% and produce visible blue-black specks. Porous calcium carbonate or rice hulls are preferred. The liquid API is applied at 30% w/w onto the carrier in a paddle mixer at 80 rpm, then dried at 45 °C to 5% moisture before incorporation into ground corn or soybean meal. A 5% or 10% premix is then blended in a double-ribbon mixer at 60–70% fill volume for 12 min; ten sampling points are extracted according to ISO 6497 and assayed for uniformity. If the assay RSD exceeds 5%, mixing is extended by 3 min and re-sampled before discharge. The finished premix is a 25 kg bagged product labeled under 21 CFR 225 medicated feed GMP requirements and retained with batch records that include carrier moisture, blend time, assay RSD, and equipment cleaning verification.

Ready-To-Use Drench Solutions Require a pH-Controlled Dilution Sequence to Prevent Oxidative Darkening

Large-volume drinking-water solutions are prepared from the oral solution API by continuous mixing into potable water at 1:200 to 1:500 depending on the prescribed dose per kg body weight. The dilution sequence is pH-controlled because phenolic constituents in the extract oxidize rapidly above pH 7.0, producing dark polymerized pigments and sediment. Citric acid at 0.1% and sodium citrate at 0.05% are dissolved first to maintain pH 4.5–5.5, and a nitrogen sparge of 0.1 L/min is applied during mixing to reduce headspace oxygen. In-line static mixing is preferred over propeller agitation because high shear can incorporate air and accelerate color development. The extract must not be combined with alkaline electrolyte salts, sodium hypochlorite disinfectants, or cationic quaternary ammonium compounds because precipitation and oxidative degradation may occur. The terminal product is a 500 mL HDPE bottle or 5 L jerry can with tamper-evident cap, filled at 2–8 °C under nitrogen and stored away from light. Release testing includes pH, appearance, microbiological limits, and preservative effectiveness per USP 51 when a preservative system is present.