Product designation Zihezi Powder Veterinary Grade API is assigned material code ZI-HZ-VAPI-P for oral powders, granules, tablets, capsules, and premix applications. The injection sub-lot is released under material code ZI-HZ-VAPI-I after additional bacterial endotoxin and sub-visible particulate controls. The material is supplied as a white to off-white crystalline powder in double polyethylene bags within a fibre drum or, for injectable-grade packaging, in vacuum-sealed aluminium-foil bags under nitrogen. The release specification follows Ph. Eur. general monograph 2034, EU GMP Part II for APIs, and VICH GL18 for residual solvents. Published peer-reviewed data for this specific veterinary active substance configuration are limited; the technical statements below therefore describe assigned release limits, pharmacopoeial test methods, and manufacturing control windows rather than target-animal clinical efficacy data.

Active Substance Identity and Powder-Grade Specification

The powder is tested for appearance, identity by infrared absorption and reversed-phase HPLC retention time, water content, related substances, residual solvents, residue on ignition, particle-size distribution, bulk and tapped density, and microbial enumeration. The oral-grade release limits are assay 98.0%–102.0% on the anhydrous basis, water ≤0.5%, total specified impurities ≤0.5%, total unspecified impurities ≤0.10%, and residue on ignition ≤0.1%. Residual solvent acceptance follows VICH GL18 class 2 concentration limits; class 1 solvents are controlled as not detected in the injection sub-lot. Elemental impurity control is based on a risk assessment aligned with ICH Q3D principles. Particle-size acceptance is set by intended processing route: D90 ≤ 150 µm for premix and granulation, D90 ≤ 100 µm for direct compression, and D90 ≤ 75 µm for injectable suspension processing. The injection sub-lot carries bacterial endotoxin limit <0.10 EU/mg by Ph. Eur. 2.6.14, and total aerobic microbial count ≤10 CFU/g. Oral-grade lots are controlled at ≤100 CFU/g TAMC and ≤10 CFU/g TYMC by Ph. Eur. 2.6.12 and 2.6.13.

Particle-size control is achieved by de-agglomeration through 0.150 mm stainless-steel sieves and, for injection-grade material, air-jet milling under nitrogen. Milling gas pressure is controlled between 2.0 bar and 4.0 bar; the milled powder is sampled at 15-minute intervals until D90 meets the injectable limit. Overtreatment in the mill reduces bulk density below 0.30 g/mL, causing poor flow and bowl adhesion in subsequent mixing operations. The supplier therefore stops milling when D90 enters the 70–75 µm window rather than targeting over-micronisation, because further size reduction increases surface area and moisture sensitivity without improving dissolution in the intended veterinary formulations.

Direct compression of the oral-grade powder on a rotary tablet press equipped with pre-compression roller force between 4 kN and 12 kN and main compression force between 15 kN and 30 kN is limited primarily by powder flow. Representative technical dossier data show bulk density 0.38 g/mL to 0.52 g/mL and tapped density 0.52 g/mL to 0.72 g/mL, giving Hausner ratios of 1.25 to 1.40. After dry blending with 0.5% w/w colloidal silicon dioxide and 1.0% w/w magnesium stearate, mass uniformity on a 12-station rotary press at 25 rpm remains within ±2%. When the API fraction exceeds 70% w/w and the blend is exposed to ambient relative humidity above 60%, weight variation widens and tablet ejection force increases from approximately 1.2 kN to 2.1 kN. Pre-drying at 40°C ± 2°C for 4 h is therefore required when storage RH exceeds 60%. Roller compaction is an alternative for high-dose oral solids; after compaction and milling through a 0.8 mm screen, granule D50 is typically 180–260 µm.

High-shear aqueous granulation with 5% w/w povidone K30 solution changes the particle-size envelope and requires disintegration adjustment in tablet formulations. In process capability trials, impeller speed 150–250 rpm, chopper speed 1,500–2,000 rpm, and granulation time 3–6 min produce wet-milled granules with D50 120–200 µm. Tablet friability below 1.0% is achieved when hardness is maintained above 60 N. Prolonged granulation beyond 8 min at maximum chopper speed reduces compressibility and increases final tablet porosity above 12%, which is undesirable for aqueous film-coating operations. For capsule filling, low-shear blending with dibasic calcium phosphate dihydrate and sodium starch glycolate is used; segregation potential measured after 5 min tapping is acceptable when the D50 ratio of API to filler does not exceed 1:3.

If the Injection-Grade Sub-Lot Is Reconstituted in an Aqueous Vehicle

Injectable processing requires controls that are absent from oral powder release. The injection sub-lot is controlled for bacterial endotoxins at <0.10 EU/mg by Ph. Eur. 2.6.14, sub-visible particulate matter by Ph. Eur. 2.9.19, and total aerobic microbial count at ≤10 CFU/g. Reconstitution in water for injection is buffered to pH 6.0–7.5 with phosphate or citrate systems because unbuffered solutions below pH 4.0 show more than 2.0% assay loss after 24 h at 40°C. Terminal sterilisation at 121°C for 15 min is acceptable for neutral, buffered solutions only when the resulting assay loss is <2.0%. Sterile filtration through 0.2 µm polyethersulfone membranes is recommended before aseptic filling. The formulation should not be autoclaved in the presence of reducing sugars or amine-based buffers because specified impurities increase above 0.5% under those conditions.

Aseptic processing of the injection sub-lot requires dry heat depyrogenation at 250°C for 2 h if the primary container is non-sterile. The API itself is not exposed to dry heat for depyrogenation because thermal degradation begins above 180°C; vial, stopper, and filter components are depyrogenated separately. Filter compatibility data show that a 0.2 µm polyethersulfone membrane retains less than 0.5% of the active substance from a 2% w/v buffered solution. Nylon and cellulose acetate membranes should be avoided because adsorption can exceed 5% at low concentration.

Why Premix Uniformity Limits Are Tighter Than Finished Feed Tolerances

Premix use imposes particle-size and flow constraints because the API is diluted into feed matrices at inclusion rates as low as 2 kg/t in medicated feed. The D90 ≤ 150 µm limit for premix grade is tighter than many industrial powders because coarse fractions can stratify during pneumatic transfer and ribbon blending. Premix batches are sampled according to ISO 2859-1 normal inspection level II, and uniformity of content in the premix is assessed at 10 sampling points with acceptance of 90.0%–110.0% of label claim and relative standard deviation below 5.0%. Lactose or glucose carriers are recommended at 10% w/w API concentration. Hard water above 250 mg/L calcium carbonate equivalents can produce turbidity in drinking-water dilution; 0.05% w/v disodium EDTA is used to restore clarity where site water requires it.

Premix granulation onto lactose carrier is performed at low shear to avoid generating fines below 45 µm; fines increase dusting and segregation in feed mills. The finished premix is controlled for loss on drying at ≤1.5% and bulk density 0.55–0.75 g/mL. Medicated feed mixed with the premix is sampled after 3 minutes and 10 minutes of ribbon mixing to confirm that the coefficient of variation for the active substance remains below 5.0%.

Long-term stability samples held at 25°C ± 2°C / 60% RH ± 5% RH and accelerated samples at 40°C ± 2°C / 75% RH ± 5% RH are used to assign retest intervals for powder in the original fibre drum. The oral-grade lot remains within specification for 24 months under long-term conditions when the heat-sealed polyethylene liner is kept closed and the product is stored below 60% RH. Repeated opening of bulk containers at ambient humidity above 75% RH increases water content at approximately 0.02% per opening cycle in the manufacturer’s container-closure study; container replacement or desiccant use is therefore required for multi-campaign production. The injection sub-lot is shipped in vacuum-sealed aluminium-foil bags under nitrogen and assigned a shorter retest interval if the bag is opened outside an ISO 14644-1 class 8 controlled environment.

Forced degradation studies for the oral grade show that oxidative stress with 3% w/w hydrogen peroxide for 24 h at 25°C increases total impurities by 1.2%; acid stress at pH 1.2 and heat stress at 80°C for 48 h produce different degradation profiles. These studies support peak purity in the HPLC method rather than routine stability acceptance. The oral powder is not protected against oxidation by added antioxidants; formulators must add butylated hydroxyanisole or ascorbic acid if the finished feed or oral solution contains oxidising carriers. Data for specific oxidation conditions in non-aqueous vehicles are limited, so a matrix-specific forced degradation study is required before commercial batch release.

Comparative Release Requirements Across Dosage-Form Streams

Table 1 summarises the release differences among the oral powder grade, tablet and capsule application, and injection sub-lot for the same molecular entity.

Manufacturing-scale comparisons between this pharmaceutical grade and ungraded feed or industrial powder show that the pharmaceutical grade is supplied against microbial, elemental impurity, and residual solvent monographs that are not routinely applied to commodity powder. The pharmaceutical powder is de-agglomerated through 0.150 mm stainless-steel screens under humidity-controlled air; the injection sub-lot is further air-jet milled and sampled according to ISO 2859-1. These operations reduce batch-to-batch assay variability from approximately ±3% in unprocessed powder to ±1% in the released API, based on 24-month trend data for oral-grade lots. The controlled powder also avoids the common failure mode of a premix-grade API entering an injectable formulation without endotoxin or sub-visible particulate certification.

Regulatory Control Matrix and Release Documentation

Each batch is supported by a certificate of analysis, certificate of origin, and a EU GMP Part II compliance statement. The release dossier includes residual solvent data under VICH GL18, elemental impurity risk assessment under ICH Q3D principles, and stability data under the conditions specified above. The API is not sterile; terminal sterilisation is required for injectable formulations. The material is incompatible with strong oxidising agents, strong acids at pH below 2.0, and primary amines in aqueous media because these conditions accelerate degradant formation. Storage below 60% RH and above 5°C is required to avoid moisture uptake and condensation.

The operational boundary for this grade is set by microbial status, particle-size segregation, and water uptake rather than chemical instability under normal storage. The principal application difference from other products is sub-lot assignment: oral, premix, and injectable uses are not supplied from the same unclassified powder but are released with application-specific particle size, endotoxin, and microbial data. This reduces downstream reprocessing such as re-milling and depyrogenation. However, material control does not replace stability testing in the finished veterinary dosage form; compatibility and preservative efficacy must be verified separately for each formulation because route of administration, packaging, and target species alter the risk profile.