Direct compression of spray-dried Shuanghuanglian extract is rarely feasible above 30% w/w drug loading because the amorphous phenolic glycosides produce capping at compaction pressures above 180 MPa on rotary presses. Wet granulation with aqueous ethanol 60% v/v is therefore preferred for tablets intended for oral administration to dogs, cats, and weaned calves. In a typical core formulation, the extract solids are fixed at 25–40% w/w; microcrystalline cellulose PH102 is added at 35–50% w/w as a brittle/plastic filler; crospovidone is incorporated at 4–6% w/w as a disintegrant; povidone K30 at 2–4% w/w is dissolved in the ethanolic granulation fluid; and magnesium stearate at 0.5–1.0% w/w is the final lubricant. The granulation endpoint is reached when the wet mass passes through a 710 µm sieve without smearing and the dried granule loss on drying is 3–5% at 105 °C for 15 min. Drying is carried out in a tray dryer at 60 °C for 2–3 h or in a fluid-bed dryer with inlet air at 65–70 °C and product temperature not exceeding 45 °C because the dried extract shows a glass transition near 48–52 °C, above which particle agglomeration occurs. Compression is run on a 16-station rotary tablet press with 8 mm round concave tooling at 30–40 rpm, with target tablet weight 250 mg, hardness 7–10 kp, friability not more than 1.0%, and disintegration not more than 30 min in 900 mL of 0.1 M hydrochloric acid at 37 ± 0.5 °C using basket apparatus. Terminal tablets are film-coated with hydroxypropyl methylcellulose 6 mPa·s at 3% w/w weight gain to mask bitterness and to reduce moisture uptake; the coating dispersion is applied at 45–50 °C pan temperature and 1.5–2.0 g/min spray rate. Release testing follows the CVP 2020 veterinary tablet monograph, and finished-tablet specifications require baicalin 90.0–110.0% of label claim and chlorogenic acid 85.0–115.0% of label claim by HPLC-UV with a C18 column 250 × 4.6 mm, 5 µm, using a phosphoric acid/methanol gradient.

What Limits Sterile Filtration of Herbal Extract Injection Solutions?

Because Shuanghuanglian extract contains chlorogenic acid, baicalin, and residual pectin-like polysaccharides from three botanical sources, sterile filtration behaves differently from that of synthetic small-molecule parenterals. Aqueous injection solutions are prepared by dissolving 50–100 g/L of dry extract equivalent in Water for Injection at 40–50 °C under high-shear mixing at 3000–5000 rpm for 20–30 min; the pH is then adjusted to 5.5–6.5 with 0.1 M sodium hydroxide or hydrochloric acid. A sharp flux decline of 40–60% across a single-use 0.22 µm polyethersulfone filter cartridge at 20–25 °C is observed on production-scale batches due to membrane fouling by high-molecular-weight polysaccharides and phenolic acid aggregates; the solution is therefore clarified through a 0.45 µm polypropylene depth filter and chilled to 2–8 °C for 12 h before final sterilizing filtration. Terminal steam sterilization at 121 °C for 15 min is generally avoided because baicalin shows pH-dependent degradation and Maillard-type browning of residual reducing sugars raises color intensity beyond the veterinary injectable monograph limit. Release testing includes sterility by membrane filtration with incubation for 14 days at 30–35 °C and 20–25 °C, bacterial endotoxin by kinetic chromogenic assay with a limit derived as 5 EU/kg body mass per hour of dosing, subvisible particulate matter by light obscuration under USP <788> with not more than 6000 particles per container at ≥10 µm and 600 per container at ≥25 µm, and marker assay by HPLC-UV at 280 nm for baicalin. The final injection solution is filled into 10 mL and 20 mL amber glass ampoules or butyl-rubber-stoppered vials under nitrogen to limit chlorogenic acid oxidation; osmolality is adjusted with sodium chloride to 280–320 mOsm/kg. Incompatibilities include sulfite antioxidants at low pH, which can accelerate ester cleavage of chlorogenic acid, and polyvinyl chloride administration sets that adsorb baicalin during slow infusion.

Capsule Filling Demands Low-Moisture Extract Granulation

In low-volume veterinary capsule manufacturing, the hygroscopic nature of dried Shuanghuanglian extract determines fill-weight consistency and shell integrity. Hard gelatin capsules are filled with a granulated blend containing 30–40% w/w extract solids, 30–40% w/w microcrystalline cellulose PH101, 20–25% w/w lactose monohydrate, 3–5% w/w croscarmellose sodium, 0.5–1.0% w/w magnesium stearate, and 0.2–0.5% w/w colloidal silicon dioxide. Granulation is performed with ethanol 70% v/v rather than an aqueous binder to keep granule moisture below 4%; the wet mass is passed through a 1.0 mm screen and dried in a tray dryer at 50–55 °C to a final loss on drying of 2–4%. The blend is filled into size 0 hard gelatin capsules at target fill weight 300 mg using an intermittent-motion capsule filling machine with dosator or tamping pin. Tapped density is maintained between 0.60 g/mL and 0.80 g/mL, and the Carr index is held below 20% to avoid dose weight deviation above 5%. Moisture transfer into the capsule shell becomes measurable when granule water activity exceeds 0.55; below that threshold, shell brittleness at 25 °C/60% RH remains acceptable. Dissolution testing follows the CVP 2020 capsule monograph using apparatus 2 at 75 rpm in 900 mL of water at 37 ± 0.5 °C, with not less than 80% baicalin released at 45 min. Storage in high-density polyethylene bottles with 1 g silica gel desiccant canisters is specified; blister packaging is avoided unless the lidding foil includes a desiccant layer, because phenolic acids accelerate gelatin crosslinking in humid conditions.

Water-soluble oral powders for mass medication in drinking water are prepared by dry adsorption of the liquid extract onto a dextrose monohydrate carrier or by spray-drying after mixing. In a typical batch, the extract solids are diluted to 5–15% w/w with dextrose monohydrate 75–85% w/w, sodium chloride 1–2% w/w, citric acid 0.5–1.0% w/w, and maltodextrin DE10–15 5–10% w/w; the citric acid lowers the reconstituted solution pH to 3.5–4.5, a range that stabilises chlorogenic acid against oxidative browning. The dry powder is milled and screened through a 60 mesh sieve, with not less than 98% passing; reconstitution in potable water at 20–25 °C at 50 g/L should yield a clear to slightly opalescent liquid within 5 min under gentle agitation. Packaging for the terminal product is a 100 g, 500 g, or 1 kg aluminium foil laminate sachet with a polyethylene inner layer; the foil reduces moisture ingress and light exposure, which otherwise cause baicalin assay loss of up to 10% over 6 months at 40 °C/75% RH. Dosage in drinking water for pigs is adjusted to deliver 0.5–1.0 g powder per 10 kg body weight per day for 3–5 days; medicated water is prepared fresh every 24 h and drinking systems are rinsed before and after medication. Batch release includes loss on drying not more than 5%, bulk density 0.55–0.70 g/mL, HPLC-UV assay for baicalin and chlorogenic acid, and residual solvent testing for ethanol when the extract was adsorbed from an ethanolic concentrate. The finished powder is controlled under the CVP 2020 oral powder monograph for veterinary herbal preparations.

Fluidised-Bed Drying Limits for Shuanghuanglian Granules

The wet granulation endpoint for Shuanghuanglian granules determines both downstream drying capacity and baicalin marker retention. A high-shear mixer granulator with 10 L bowl is charged with 10–20% w/w extract solids, 50–60% w/w sucrose, 20–30% w/w dextrin, and 2–4% w/w povidone K30; water is added at 8–12% w/w of dry mass while impeller speed is held at 200–300 rpm and chopper speed at 1500–2500 rpm for 3–5 min. The wet granules are transferred to a fluid-bed dryer with inlet air temperature 60–70 °C and product temperature 40–45 °C; the drying endpoint is defined by loss on drying 2–3% and not by fixed time, because the glass transition of the amorphous extract at 48–52 °C causes irreversible sticking and wall adhesion if the product temperature exceeds 50 °C. After drying, the granules are passed through a 16 mesh sieve and retained on a 40 mesh sieve to provide a uniform 355–1000 µm particle-size band; bulk density is controlled at 0.50–0.60 g/mL and angle of repose below 35°. Terminal granules are filled into 100 g and 500 g high-density polyethylene bottles with induction-sealed caps and a 1 g desiccant canister; the granules are administered as an oral drench after reconstitution in water at 37 °C or mixed into small volumes of moist feed for weaned pigs. Stability samples stored at 40 °C/75% RH for 6 months are monitored for baicalin, chlorogenic acid, pH of a 10 g/L solution, and microbial limits; a characteristic failure mode in bulk storage is caking caused by moisture ingress above 5% loss on drying. Batch release under the CVP 2020 granule monograph includes sieve analysis, loss on drying, and marker assay.

When Shuanghuanglian Extract Is Diluted into Medicated Feed Premixes

Dry mixing of Shuanghuanglian extract into feed premixes requires a carrier system that accommodates particle-size mismatch and the hygroscopic extract fraction. A typical premix contains 2–10% w/w extract solids, 85–95% w/w ground rice hull or corn cob carrier, 0.5–1.0% w/w mineral oil, and 0.2–0.5% w/w precipitated silica; the mineral oil is sprayed onto the carrier before adding the extract to reduce dust and segregation. Mixing is performed in a horizontal ribbon mixer at 20–30 rpm for 10–15 min; blend uniformity is assessed by sampling 10 points from the mixer and assaying baicalin, with a relative standard deviation not more than 5%. The premix is then diluted in final feed at 1–5 kg/tonne to achieve target daily intake; however, segregation risk at the feed mill increases sharply when extract particle size is below 100 µm and carrier particle size exceeds 1000 µm, so the extract is pre-blended with an equal mass of carrier in a planetary mixer for 5 min before incorporation. Terminal packaging is 1 kg, 5 kg, or 20 kg multi-wall paper bags with a low-density polyethylene liner; bags are closed by heat sealing to limit moisture uptake. In pelleted feed, conditioning at 80–90 °C for 30–60 s causes baicalin loss of 5–15% depending on residence time, so a 10–15% overage is added when pelleted feed is the intended final matrix. Compliance for the premix includes feed additive safety limits under GB 13078-2017, aflatoxin B1 not more than 20 µg/kg, Enterobacteriaceae not more than 1000 CFU/g, and residual solvent class 3 limits where the extract was concentrated from ethanolic extraction.

Oral solutions containing Shuanghuanglian extract are prepared at 10–20% w/v dry extract equivalent and adjusted to pH 4.0–5.5 with citric acid and sodium citrate buffer to stabilise chlorogenic acid and reduce microbial growth. The manufacturing procedure dissolves the extract in purified water at 40–50 °C under high-shear mixing, then adds 10–20% v/v propylene glycol as co-solvent, 5–10% v/v glycerin as viscosity modifier and sweetener, and 0.1–0.2% w/v sodium benzoate or potassium sorbate as preservative; the solution is cooled to 25 °C and passed through a 1 µm polypropylene filter before filling. The finished solution is packaged in 100 mL, 250 mL, or 1 L amber polyethylene terephthalate bottles with tamper-evident caps and a dosing cup; amber glass is used for small-volume veterinary clinics because chlorogenic acid undergoes photodegradation under UVA at 365 nm, and the E1cm1% absorbance at 327 nm decreases by more than 5% after 48 h of direct light exposure. Shelf-life studies at 25 °C/60% RH for 12 months show pH drift of less than 0.5 units and baicalin retention above 95% when bottle headspace oxygen is below 2%; nitrogen flushing before capping is therefore specified. Incompatibilities include benzalkonium chloride, which forms insoluble complexes with chlorogenic acid, and aluminium closures, which corrode at pH below 4.0. The oral solution is administered to swine, poultry, and calves at 1 mL per 10 kg body weight twice daily for 3–5 days; when diluted in drinking water for mass delivery, the medicated water is used within 24 h to avoid fermentation.