What limits terminal sterilization of Kushen Huanglian Injection in multi-dose vial lines?

Injectable processing of Kushen Huanglian Injection veterinary-grade API from Sophora flavescens root and Coptis chinensis rhizome is constrained by the pH-dependent solubility reversal of the quaternary alkaloid fraction during terminal sterilization. The API is a spray-dried or vacuum-dried extract; marker alkaloid content is normalized by blending because native alkaloid content shifts by ±12% depending on harvest year and drying history. In a 1,000 L jacketed preparation vessel equipped with a bottom-mounted rotor-stator mixer, the extract is introduced at the vortex periphery to avoid wall film formation. The production failure most frequently observed on scale-up is the formation of a thin unhydrated film above the liquid line; this film dislodges during the heating ramp and survives 0.22 µm filtration as visible particulate matter. To prevent this, the extract is pre-slurried in 10 volumes of 20–25°C water-for-injection before transfer. Addition is controlled at 0.8–2.0 g dried extract per 100 mL of final solution, equivalent to 0.8–2.0% w/v. The solution is pH-adjusted to 5.0–5.5 with citric acid/sodium citrate buffer, then clarified with 0.1% w/v activated carbon at 60°C for 30 min under low-shear agitation at 80–120 rpm. Filtration uses a 0.45 µm polyethersulfone prefilter and a 0.22 µm PES membrane at ≤0.2 MPa differential pressure. Terminal sterilization is validated with a 105°C/30 min air-overpressure autoclave cycle; a 121°C/15 min cycle is acceptable only if the pH is locked at 5.0–5.5 and the drug product has passed differential scanning calorimetry screening for thermal decomposition. Berberine salts lose aqueous solubility above pH 6.8; precipitation is observed in production holds when the pH drifts above this threshold during the terminal heat ramp. The injectable-grade API lot must meet bacterial endotoxin limits <0.25 EU/mL in the finished product per Ph. Eur. 2.6.14/USP <85>, sterility per Ph. Eur. 2.6.1, heavy metals <10 ppm per Ph. Eur. 2.4.8, and absence of Salmonella per ISO 6579-1:2017. Finished presentations are 10 mL, 20 mL, 50 mL amber borosilicate vials and 100 mL multi-dose vials sealed with chlorobutyl rubber closures; the larger vial format requires preservative efficacy testing per Ph. Eur. 5.1.3 unless the product is single-use.

At low inclusion levels in poultry drinking water systems, the extract is formulated as a concentrated oral solution that is diluted through a proportional dosing pump at 0.1–0.5% v/v into the main water line. The working concentration in the final drinking solution is 0.10–0.50 g of extract per liter, depending on water pH and carbonate hardness. A 500 L jacketed stainless steel tank with a counter-rotating agitator is used to prepare the concentrate; propylene glycol is added at 30–50% v/v and glycerin at 5–10% v/v to prevent salting-out of berberine at low temperatures before water is introduced. The bulk is pH-adjusted to 5.5–6.5 with citrate buffer and agitated at 80–120 rpm for 30 min. Concentrate viscosity at 25°C is typically 80–150 mPa·s; at lower storage temperatures the dosing line is maintained at 20–25°C to prevent viscosity increase and pump cavitation. Inline filtration is carried out through a 50 µm stainless-mesh filter before filling, and the product is packed into 1 L and 5 L high-density polyethylene jerry cans with fill volume tolerances of ±1.0% and ±0.5% respectively. Non-sterile oral liquid administration requires microbial quality per Ph. Eur. 2.6.12 and 2.6.13 with acceptance criteria for non-sterile oral liquids; the API must also meet heavy metal limits of <20 ppm per Ph. Eur. 2.4.8 and residual solvent limits per USP <467> when solvent-based extraction is used at the upstream API site. Sodium metabisulfite is incompatible above 0.05% w/v because bisulfite adduct formation with berberine causes HPLC peak area loss and pH drift during 30-day stability storage. The use of softened water in the field is required when carbonate hardness exceeds 300 mg/L as CaCO₃; otherwise the concentrate can generate a transient turbidity at the dosing pump injection point.

Soluble powder carrier chemistry under high-moisture drinker line conditions

Because berberine chloride and related quaternary alkaloids in the extract are hygroscopic, soluble powder formulation requires carrier selection that keeps water activity below 0.60 at 25°C. Dry blending is conducted in a 500 kg ribbon blender at 15 rpm for 15 min; carrier systems based on dextrose monohydrate 50–70% w/w, lactose monohydrate 20–40% w/w, and anhydrous citric acid 1–2% w/w are used to maintain final powder moisture below 5.0% by Karl Fischer titration. The extract addition ratio in the finished soluble powder is 1.0–2.5 g per liter of drinking water after reconstitution, and the dry carrier inclusion level is adjusted to deliver 0.05–0.25% w/w extract in final feed when used as a direct feed powder. Fluid-bed granulation is required when extract loading exceeds 20% w/w because simple ribbon blending leads to segregation of high-density extract particles with D90 > 250 µm; granulation inlet air is maintained at 50–60°C and product moisture is reduced to <3% before sieve classification at 16–40 mesh. The powder must meet non-sterile microbial limits of TAMC ≤10⁴ CFU/g and TYMC ≤10² CFU/g per Ph. Eur. 2.6.12/2.6.13, absence of Salmonella in 25 g per ISO 6579-1:2017, and heavy metals <20 ppm per Ph. Eur. 2.4.8. Terminal packaging is 100 g and 500 g foil-lined sachets, 1 kg barrier pouches, and 25 kg polyethylene-lined multi-wall paper bags. In high-humidity production zones above 60% RH, the dry extract is pre-dried at 45°C under −0.08 MPa vacuum for 2 h before weighing.

Starch-based wet granulation of the dried extract for swine feed pellets requires pregelatinized starch as a binder because the extract contains hygroscopic quaternary alkaloid salts that soften at 40°C and can fuse screens during dry size reduction. The granulation substrate is prepared by pre-mixing the extract with maize starch and microcrystalline cellulose in a high-shear granulator at impeller speed 200–300 rpm; the extract inclusion is 0.2–1.0 kg per tonne of complete feed, equivalent to 0.02–0.10% w/w in the final feed. For oral administration granules, a 5 g granule dose contains 200–500 mg of extract. Binder solution is 5% w/w povidone K30 in purified water sprayed at 15–25 g/min per kg of dry mix; granulation is transferred to a fluid-bed dryer with inlet air at 50–60°C until loss on drying is <3.0%. The dried granules are screened to 16–40 mesh and filled into 100 g, 500 g, and 20 kg LDPE-lined feed-grade bags. Microbial quality is controlled as non-sterile oral granule per Ph. Eur. 2.6.12/2.6.13, with TAMC ≤10³ CFU/g and TYMC ≤10² CFU/g; heavy metals are limited to <20 ppm by Ph. Eur. 2.4.8. Pellet mill in-feed at temperatures above 70°C is not recommended for this granule unless post-pellet liquid application or temperature-controlled short conditioning is used.

Moisture-barrier granulation as a prerequisite for chewable tablet compression of Sophora flavescens–Coptis chinensis extracts

Mechanistically, the quaternary alkaloid fraction in the extract exhibits moisture sorption at relative humidity above 50% at 25°C, which causes tablet sticking during compression. The extract is therefore roller-compacted with microcrystalline cellulose 50–80% w/w and croscarmellose sodium 2–5% w/w, then lubricated with magnesium stearate 0.5–1.0% w/w. Addition ratio in the finished tablet core is 30–150 mg extract per unit, representative of 10–30% w/w of the core blend. Compression is carried out on a rotary tablet press at 15–25 kN main compression force; the target tablet hardness is 60–90 N and the friability limit is <1.0% per USP <1216>. Film coating uses a 12% w/w hypromellose 6 cP aqueous dispersion at bed temperature 38–42°C to provide a moisture barrier. Capsule formulations use size 2 or size 3 hydroxypropyl methylcellulose shells to limit hygroscopic shell-bridging seen with gelatin shells. The regulatory route determines the compliance framework: drug products fall under 21 CFR 211 current good manufacturing practice, while non-drug supplement formats fall under 21 CFR 111; in either case, heavy metals are limited to <10 ppm per Ph. Eur. 2.4.8, residual solvents to USP <467>, and microbial quality to Ph. Eur. 2.6.12/2.6.13. Finished presentations are 60 and 120 count HDPE bottles with 1 g silica-gel desiccant canisters and induction-sealed closures.

If pellet conditioning exceeds 80°C, heat-labile alkaloid recovery dictates the inclusion window

For ruminant premix applications, the extract is incorporated in a carrier premix with calcium carbonate and wheat middlings. The addition rate is 0.05–0.15% w/w in the total mixed ration; this corresponds to 2–10 kg of extract per tonne of premix when the premix is diluted at 1:50 or 1:100 at the feed mill. Production is performed in a horizontal paddle mixer at 20–30 rpm for 10 min. Pellet conditioning above 80°C reduces the recovery of the berberine fraction, and the inclusion level is increased by 10–15% when conditioner temperature cannot be held below 80°C; published data for this specific extract configuration is limited, so the adjustment is confirmed by HPLC area recovery under the feed mill’s own temperature profile. Compliance for the premix follows EC 183/2005 feed hygiene, heavy metals per Directive 2002/32/EC Annex I, and Salmonella absence per ISO 6579-1:2017. Terminal packaging is 25 kg multi-wall paper bags with inner polyethylene liner or bulk bag containers for integrated feed mills.