Yujin Injection Veterinary Grade API, when used in veterinary tablet manufacture, is first screened for particle size by ISO 13320:2020 laser diffraction. A d90 below 150 µm and a d50 between 40 µm and 80 µm are common development targets for direct compression candidates. Lots with bulk density below 0.45 g/mL tend to bridge in the feed frame of rotary presses and are diverted to wet granulation. Loss on drying is maintained below 0.5% by USP <731> because moisture above this threshold increases sticking to the upper punch face. Pre-drying in a tray dryer at 40°C for 2 h is used when incoming lot moisture exceeds 0.5% or when relative humidity in the compression suite exceeds 60%.

A representative direct compression formula for a 100 mg active tablet core consists of 40.0% w/w API, 52.5% w/w microcrystalline cellulose, 5.0% w/w croscarmellose sodium, 1.5% w/w sodium stearyl fumarate, and 1.0% w/w colloidal silicon dioxide. The API and microcrystalline cellulose are blended in a V-blender at 12 rpm for 15 min. Disintegrant is added before lubrication; lubricant is added for the final 3 min only. Compression is performed on a rotary tablet press at 12–20 kN main compression force. In-process hardness is held at 5–8 kp; disintegration is tested by USP <701> in water at 37°C and should not exceed 15 min.

Compliance obligations include 21 CFR 211.84 for incoming component testing, 21 CFR 211.101 for verified charge-in, and 21 CFR 211.110 for in-process sampling. Finished cores are tested for content uniformity by USP <905>; acceptance value must not exceed 15.0. If film coating is required, an aqueous Opadry II coating is applied at 3% w/w weight gain. Terminal product is a veterinary tablet core or coated tablet intended for oral administration.

What Changes When the Same API Lot Is Filled as a Sterile Injection?

The API is not assumed sterile; if the certificate of analysis does not include USP <71> compliance, the solution must be sterilized downstream. Under aseptic processing, the API is dissolved in Water for Injection chilled to 10–15°C to reduce oxidative degradation. A nitrogen overlay is applied when the molecule contains phenolic or thioether moieties. The solution is adjusted to pH 4.5–7.5 with 0.1 N hydrochloric acid or sodium hydroxide. If isotonicity is required, tonicity is adjusted with sodium chloride to 280–320 mOsm/kg measured by USP <785>. For multi-dose vials, benzyl alcohol at 0.9% v/v is added as a preservative; for single-dose vials, preservative is omitted.

The compounding vessel is jacketed and kept at 10–15°C during dissolution to reduce degradation. A sterilizing-grade 0.22 µm polyvinylidene fluoride membrane with a 0.1 µm prefilter is used for aseptic filtration. Pre-filtration bioburden is monitored and controlled below 10 CFU/100 mL as an in-process limit. Filtration is followed by filling into depyrogenated Type I glass vials under ISO 5 conditions per 21 CFR 211.42. If terminal sterilization is feasible, a moist heat cycle at 121°C for 15 min with F0 ≥ 8 min is applied; heat-labile formulations are aseptically filtered instead. For freeze-dried products, primary drying occurs at -40°C for 24 h, followed by secondary drying at 20°C for 6 h; moisture content is confirmed below 1.0% by USP <921>.

Finished injectables are tested for sterility by USP <71>, bacterial endotoxins by USP <85>, and particulate matter by USP <788>. Endotoxin limits are calculated from maximum dose and target species body weight; published data for this specific configuration is limited and must be established per product. 21 CFR 211.94 applies to container closure integrity. Terminal product is a sterile injection in 10 mL, 50 mL, or 100 mL vials sealed with chlorobutyl stoppers.

When Potency Uniformity in Low-Fill Capsules Requires Geometric Dilution

Capsule filling with less than 10 mg active per unit cannot rely on simple mixing because hopper segregation and electrostatic adhesion produce poor content uniformity. Geometric dilution is performed by pre-blending the API with an equal mass of lactose monohydrate, passing the blend through a 355 µm sieve, then adding further lactose in doubling portions. A typical low-dose capsule formula contains 1–10% w/w API, 88–96% w/w lactose monohydrate, 0.5–1.0% w/w magnesium stearate, and 1–2% w/w croscarmellose sodium. The final blend is filled into hard gelatin or HPMC capsules at 30–45% relative humidity to prevent shell softening and static charge.

Filling equipment is a dosator or tamping-pin capsule machine. Weight variation checks are performed every 15 min; for a 250 mg fill weight, individual weight limits are ± 5%. Dissolution testing is carried out by USP <711> using 900 mL water at 37°C with paddle apparatus at 50 rpm; stage 1 acceptance is Q = 80% at 30 min. Content uniformity by USP <905> requires acceptance value ≤ 15.0.

21 CFR 211.101 governs charge-in verification; 21 CFR 211.110 establishes blend uniformity sampling. HPMC shell selection occurs when lot moisture exceeds 0.5% or when aldehyde crosslinking with gelatin is observed. Terminal product is a hard capsule containing 250 mg blend fill weight.

In poultry and swine drinking water systems, the API is formulated as a water-soluble powder with a dissolution target of 99% in 1 L water at 20°C within 5 min. The carrier phase uses lactose monohydrate and dextrose in a 3:1 ratio. Sodium lauryl sulfate at 0.1–0.3% w/w is added as a wetting agent; citric acid at 1–2% w/w buffers the reconstituted solution below pH 6.0 to reduce hydrolysis. Dry blending is performed in a ribbon mixer at 12 rpm for 20 min. If fluid bed granulation is required, inlet air temperature is 60–70°C, outlet air is 30–35°C, and final LOD is held below 0.5% by USP <731>. Water activity is monitored below 0.60 to prevent hydrolytic degradation.

Cleaning validation follows 21 CFR 211.67 because residual API in shared packaging equipment can contaminate non-medicated feed products. VICH GL18 applies if residual ethanol from granulation is present. Hard water with high divalent cation content may reduce dissolution; if precipitate is observed, disodium EDTA at 0.1% w/w is incorporated. Terminal product is a foil-lined 100 g or 1 kg pouch, reconstituted at 1 g/L drinking water.

Premix Granulation and Carry-Over Control in Medicated Feed

Medicated feed premix is produced by stepwise dilution of the API to 1–20% w/w active content with a carrier such as calcium carbonate, wheat middlings, or ground rice hulls. Homogeneity is checked by collecting 10 samples per batch; coefficient of variation of active content should not exceed 10%. Final feed dose is typically 0.5–5 kg premix per 1000 kg finished feed. Mixing is conducted in a twin-shaft paddle mixer or ribbon mixer for 10–15 min. Carrier particle size is controlled between 200 µm and 500 µm to reduce segregation.

When the API is heat-labile, addition after pelleting via liquid spray is required because pellet conditioning at 70–85°C may reduce potency. If the API is heat-stable, it may be mixed before conditioning, but retention time above 80°C should remain below 30 seconds unless thermal degradation kinetics are established for the lot. Dust extraction and choke-feed are applied at the blending station to reduce cross-contamination. EU Regulation (EU) 2019/4 requires homogenicity and carry-over control; 21 CFR 558 governs medicated feed article status in the United States. Clean-in-place validation follows 21 CFR 211.67. Terminal product is a 25 kg multiwall paper bag with polyethylene inner liner.

Where cattle and sheep require an oral drench, the API is dissolved in a co-solvent system rather than dispersed as a suspension. Formulation for drench solutions includes 0.5–10% w/v API, 10–30% v/v propylene glycol, 5–20% v/v ethanol, 1.5% v/v benzyl alcohol as preservative, and 0.1% w/v sucralose for palatability. Purified water is added to final volume. The pH is adjusted to 4.0–6.0 with citrate buffer; pH is verified by USP <791>. Viscosity is controlled below 20 mPa·s by USP <912> to permit accurate drench gun dosing.

The solution is compounded in a closed stainless steel vessel with a propeller impeller at 200 rpm. The API is first dissolved in the co-solvent phase at 20–25°C; water is then added gradually with continuous mixing. The final solution is filtered through a 10 µm stainless steel cartridge and filled into amber HDPE containers. Amber containers meeting USP <671> are selected because light exposure can reduce assay by photodegradation. 21 CFR 211.94 applies to container closure integrity; 21 CFR 211.160 supports process validation. Terminal product is an oral drench in 1 L or 5 L bottles.