Liquid silkworm ecdysis API is usually converted into tablet intermediates by first fixing the aqueous fraction onto a porous pharmaceutical carrier rather than by direct addition into the final dry blend, because free liquid reduces flowability and accelerates punch filming on rotary tablet presses operating above 60,000 tablets/h. The liquid fraction contains an ecdysteroid component and residual chitin/protein material; both contribute to hygroscopicity and require granulation endpoints based on loss on drying rather than visual appearance.

On pilot-scale high-shear granulators fitted with a twin-screw chopper and a bowl temperature probe, a pre-blend of microcrystalline cellulose PH102, lactose monohydrate 200 mesh, crospovidone and colloidal anhydrous silica is charged, and the liquid API is metered through a peristaltic pump nozzle positioned below the impeller sweep. The addition interval is extended until the impeller power draw stabilizes; over-addition produces a paste with a torque rise that can overload 18 kW drive motors and leaves non-homogeneous hard agglomerates after drying. The wet mass is passed through a conical mill fitted with a 4.0 mm rasp screen, then dried in a fluid-bed bowl at an inlet air temperature not exceeding the limit established by forced degradation studies; published data for this specific liquid API are limited, so the drying temperature is validated batchwise by HPLC purity before lot release. Drying is stopped at 1.5%–2.5% loss on drying by Ph. Eur. 2.2.32.

After dry milling through a 1.0 mm screen, extra-granular croscarmellose sodium is added before lubrication with 0.5% w/w magnesium stearate. Tablets are compressed on a 16-station rotary press using 9 mm concave tooling at 12–18 kN. Hardness is monitored against friability ≤1.0% per Ph. Eur. 2.9.7. Uniformity of mass is tested by Ph. Eur. 2.9.5, content uniformity by Ph. Eur. 2.9.40 or USP <905>, and dissolution by Ph. Eur. 2.9.3 or USP <711>. Dissolution method development for the ecdysteroid fraction generally requires surfactant screening because desorption from the dried granulate is medium-dependent and can be incomplete in plain buffer.

During pilot batches, the principal failure mode is not hardness failure but lamination at tablet crowns caused by moisture migration from granule cores that were not fully equilibrated after drying. If tablets are compressed immediately after dry milling, residual internal moisture at the granule center plasticizes the binder and produces cap separation. A post-drying equilibration bin is therefore used for 8–12 h before final blending; alternatively, moisture-corrected granulate is stored in desiccated intermediate bulk containers and retested before compression. Intra-granular croscarmellose sodium can wick the liquid API and form hard granules; extra-granular addition is preferred when disintegration time exceeds 15 min in Ph. Eur. 2.9.1. The particle size distribution after final milling is checked by analytical sieving per Ph. Eur. 2.9.38; a typical compression target is a d50 of 200–400 µm with more than 90% below 1.0 mm. When the fraction below 74 µm exceeds 20%, tablet weight variation can increase even with force feeders.

Can Aseptic Filtration Replace Terminal Steam Sterilization for Ecdysis Liquid Injection Solutions?

Parenteral dilution of silkworm ecdysis liquid in Water for Injections is performed under Grade A unidirectional airflow inside an ISO 14644-1:2015 Grade B background. The liquid API is first clarified through a depth filter, then serially filtered through 0.45 µm and 0.22 µm polyethersulfone capsules. Chitinous fragments and cuticular proteins that survive upstream clarification can load the final filter; therefore differential pressure across the 0.22 µm membrane is recorded continuously and the filter train is replaced if the pre-set pressure limit is reached before the batch volume has passed. Batch records include filter integrity testing by bubble point or pressure decay before and after filling, as required by Ph. Eur. 5.1.1 and sterility testing per Ph. Eur. 2.6.1. Stability protocols for the injection are based on VICH GL3.

Scale-up from filter discs to filter capsules is non-linear because the liquid contains fibrillar material; filter sizing runs should use the actual batch fluid rather than water. Flux is deliberately kept below the filter manufacturer’s maximum water flux by a factor of 0.5 to provide a pressure safety margin. Terminal steam sterilization at 121 °C for 15 min is avoided when forced degradation reveals ecdysteroid loss above the pre-defined threshold; if stability-indicating HPLC demonstrates acceptable recovery, moist-heat sterilization remains the preferred route because it simplifies sterility assurance. The formulated injection is adjusted to 280–320 mOsm/kg with sodium chloride and buffered to a pH range that avoids both precipitation of the protein fraction and oxidative degradation of the ecdysteroid fraction. Sub-visible particle burdens are controlled to Ph. Eur. 2.9.19 limits; light obscuration counts above 25 µm are evaluated after terminal processing as an indicator of aggregate formation. Adsorption onto hydrophobic surfaces, including silicone tubing and nylon membranes, should be measured by mass balance during process simulation because published data for this exact liquid API are limited.

Carrier Saturation Limits Determine Premix Homogeneity and Downstream Carryover

The liquid API is incorporated into feed premixes by spraying onto carriers having controlled oil absorption and low water activity. Defatted rice bran, wheat middlings, precipitated silica and calcium carbonate are screened by ISO 9277:2010 BET surface area for silica carriers and by bulk and tapped density per Ph. Eur. 2.9.34. The carrier is charged into a horizontal ribbon mixer with a spray bar mounted above the first third of the trough; the liquid API is delivered by a gear pump at a rate below the point at which the carrier surface becomes visibly wet. Over-wetting forms agglomerates that segregate in downstream screw conveyors and increase carryover into mixer seals.

Oil-holding capacity is measured by adding the liquid API dropwise to the carrier under constant mixing until the angle of repose falls below 35° or visible agglomeration appears; this is a carrier selection tool rather than a release test. After spraying, the premix is discharged into lined bulk bags and allowed a maturation interval before sampling. Homogeneity is assessed by collecting 10 thief samples across the discharge stream and analysing ecdysteroid content by HPLC; a coefficient of variation ≤5% is used as the in-process limit. The final premix must comply with the homogeneity requirements of Regulation (EU) 2019/4 for medicated feed and with the residue avoidance provisions of Regulation (EU) 2019/6 for veterinary medicinal products. Cross-contamination is controlled by confirming cleanout with a subsequent batch of carrier.

Drinking-water solutions derived from the same liquid API are not simply diluted stock solutions, because water quality, pH, and distribution-line biofilm formation alter dosing uniformity across a barn. Stock solutions are prepared at the highest concentration that remains physically stable for 24 h in hard water containing 250 mg/L calcium carbonate equivalent; precipitation tests are run at 5 °C and 25 °C because barn water temperatures vary between winter and summer. A proportional dosing pump calibrated to deliver 0.5%–5% of stock solution into the drinking line is protected by a coarse pre-filter to prevent nozzle clogging from particulates. Light-exposure studies under 365 nm UV-A and visible light are performed on stock solutions because the ecdysteroid fraction may undergo photodegradation; if photostability is insufficient, amber or opaque stock tanks are specified.

Microbial growth is a critical failure mode when stock solutions remain in distribution lines after drinking peaks. The system should be rinsed with untreated water after each medication pulse; if preservatives are required, their selection must consider palatability and species-specific regulatory prohibitions. Chlorine residual above 0.5 mg/L can react with cuticular protein fragments and produce turbidity, so dechlorination or an alternative water source is required in bleached distribution systems. Lines are drained and rinsed with at least 3× the dead volume after each dosing event. Pig and poultry lines differ in biofilm risk because drinking water pressure and temperature fluctuate differently; dosing pumps should be interlocked with the main water flow meter so that medication ceases when water flow stops.

When Hard Capsules Are Filled with a Liquid Concentrate Rather Than a Dry Powder Bed

Hard gelatin and HPMC capsule shells can be filled with a semi-solid or liquid concentrate of silkworm ecdysis API when content uniformity requirements are tighter than dry powder mixing can reliably provide. The liquid API is dewatered under vacuum at a temperature not exceeding the thermal limit and dispersed into a carrier system of hydrogenated vegetable oil and colloidal silica. The resulting thixotropic mass is filled on a laboratory-scale capsule filler fitted with volumetric nozzles; fill weight is checked every 15 min because viscosity drift changes delivered volume. Capsules are sealed by banding with gelatin or HPMC solution to prevent leakage; shell moisture is kept within 13%–16% for gelatin and lower for HPMC to avoid shell cracking or softening.

Fill weight uniformity is tested according to Ph. Eur. 2.9.5 and content uniformity according to Ph. Eur. 2.9.40 or USP <905>. Shell compatibility is assessed by visual inspection for staining and by disintegration testing per Ph. Eur. 2.9.1; lipid-based fill can delay disintegration, so dissolution testing per Ph. Eur. 2.9.3 may require the addition of surfactant to the medium. Fill masses with viscosity above 10,000 mPa·s at 25 °C can be filled with volumetric pumps, but bubble entrapment causes weight variation and shell staining; vacuum deaeration before filling is used to reduce entrapped air. Residual air content below 2% is targeted during process qualification to limit bubble-induced fill-weight variation. Capsule banding defects are inspected on a 20% sample of the batch during start-up and after every filler nozzle change.

Oral Granules and Unit-Dose Powders for Top-Dressing Feed

Unit-dose granules for addition to individual animal feed are produced by low-shear wet granulation of the API with mannitol, maize starch and a palatable carrier. The granulate is dried to 1.0%–2.0% moisture and sieved between 0.5 mm and 1.6 mm using analytical sieving per Ph. Eur. 2.9.38; the retained fraction is milled and re-sieved to limit sachet fill volume variation. Sachet filling is performed on a vertical form-fill-seal machine with auger dosing; fill mass is controlled by periodic checkweighing and Ph. Eur. 2.9.5 mass uniformity. Segregation is minimized by surface treatment of the granules with 0.1% w/w colloidal silica prior to sachet filling.

If the fines fraction exceeds 15%, the granule is re-sieved and the fines are re-granulated with fresh binder to maintain yield and flowability. In-process content uniformity is monitored by sampling from the beginning, middle and end of the sachet run; a coefficient of variation ≤3% across 20 sachets is used as the target for a single lot. If the formulation includes coated granules for taste masking, disintegration acceptance may shift; the coating level must be justified by dissolution verification rather than assumed to have no effect. Pouches are sealed under a nitrogen flush if oxidative stability data show a moisture- or oxygen-sensitive ecdysteroid fraction; otherwise standard foil laminate is acceptable. The powder and granule formats are intended for top-dressing only where the animal consumes the entire dose immediately and feed refusal can be observed.