Quicklime Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions is supplied as a free-flowing calcium oxide preparation produced by controlled calcination of a selected limestone fraction in a rotary kiln with target residence time of 4–6 h at 900–1100 °C. The material is released under model QL-VET-97/140, where the suffix denotes a minimum calcium oxide release assay of 95.0% on the ignited basis and a nominal laser-diffraction D50 of 140 µm. A finer milling variant QL-VET-97/75 with D50 38 µm is available for aqueous suspension processing and injectable manufacturing. The product functions as an anhydrous alkalising precursor, moisture-scavenging carrier, and pH-shift control agent in veterinary dosage forms; in aqueous environments it undergoes the slaking reaction CaO + H2O → Ca(OH)2 with an enthalpy of approximately −65.2 kJ/mol, which must be managed during granulation and solution preparation. Unlike kiln-run quicklime sold for soil stabilization or building lime, this grade is released with lot-level documentation for acid-insoluble matter, sieve residue, elemental impurities, bioburden, and, for parenteral-use evaluations, endotoxin and particulate matter controls aligned to USP <232>, USP <233>, USP <61>, USP <85>, and USP <788>.

What Release Parameters Separate a Veterinary Grade Oxide from Kiln-Run Quicklime?

The central distinction is not total calcium content alone but the residual carbonate, heavy-metal, and sieve residue profile. Technical quicklime from shaft or rotary kilns can vary by more than ±10% CaO and commonly contains sulphide, fluoride, and silicate phases from high-sulphur or siliceous feedstock. Such material can attenuate pH response unpredictably and introduce extractable iron that can discolour tablet matrices. The veterinary grade is controlled by ASTM C25-19 for CaO and loss on ignition, with particle-size distribution verified by laser diffraction per ISO 13320:2020 and by air-jet sieve residue at 150 µm and 75 µm. Microbial quality is tested by USP <61> with a release limit of <100 CFU/g total aerobic count, while elemental impurities are screened against USP <232> risk categories with analytical recovery by USP <233>.

Direct-compression tablet manufacture with QL-VET-97/140 is feasible only at controlled addition levels. On a 12-station rotary tablet press operated at 35 rpm and 18–24 kN compression force, tablet tensile strength measured by USP <1217> ranged from 1.6 MPa to 2.1 MPa when the oxide fraction was first pre-blended with microcrystalline cellulose for 15 min at 25 rpm in a V-blender and held at 2.5–5.0 wt% of the core mass. Raising the oxide level to 7.5 wt% produced ejection force spikes of roughly 40% and visible sticking on chromium-plated tooling after 3000 compressions. The anhydrous oxide is therefore reserved for moisture-sensitive active blends and is not recommended as a bulk filler in direct compression.

Aqueous Granulation, Slaking Exotherm, and Binder Viscosity Control

Wet granulation is the primary tablet and capsule route for this material because the slaking reaction can be exploited for in situ binder control but must be thermally managed. In a 600 L high-shear granulator fitted with an impeller at 120 rpm and a chopper at 1500 rpm, water addition at 6–8 kg/min through a nozzle positioned above the moving powder bed produced a granule bed temperature of 28–34 °C. When the same water dose was added over 2 min, bed temperature exceeded 48 °C and caused premature surface crusting of granules and a bimodal particle-size distribution. The practical temperature rise depends on the heat capacity of the blend and is buffered by a 5% w/w povidone K30 binder solution containing 0.2% polysorbate 80 for edge-wetting. Granulation endpoint is controlled by impeller power draw 4.5–6.0 kW and final moisture 1.8–2.4% by loss on drying at 85 °C. For capsules, the dried granules are sized through a 1.0 mm oscillating granulator and lubricated with 0.5% stearic acid for 3 min; capsule fill weights then show relative standard deviation <2.5% on a dosator machine at 40 cycles/min.

Parenteral manufacturing does not use calcium oxide as a final injectable component; it is processed as a slurry to generate calcium hydroxide for pH adjustment of weakly acidic formulations. QL-VET-97/75 is dispersed in cold water at 2–5 °C in a jacketed vessel with a high-shear rotor-stator mixer at 3000 rpm for 10 min, then passed through a 0.45 µm nylon membrane before the neutralizing solution is added to the batch. The addition must be restricted to 0.1–0.3% of total batch mass until pH stabilizes; localized overshoot above pH 10 can precipitate transition-metal hydroxides and generate subvisible particles. Final injectable solutions are tested for pH by USP <791>, particulate matter by USP <788>, and sterility by USP <71>. Published stability data for calcium oxide slurries held beyond 24 h in injectable processing vessels are limited, so the slurry is prepared fresh and held within a qualified 2–8 °C window.

When Carbonate Limits Exceed 6.0% in Premix and Granule Lines

Prolonged storage in humid air converts surface CaO to calcium hydroxide and subsequently to calcium carbonate; this is the primary source of lot variability in quicklime. For premix and granule applications, a carbonate boundary of 6.0% as loss on ignition is applied. Above this value, the desiccant capacity declines because calcium carbonate does not remove moisture and the slaking exotherm is blunted by the hydrated and carbonated surface layer. In a 500 kg ribbon blender, QL-VET-97/140 at 0.5–2.0 wt% reduced the moisture of a dicalcium phosphate carrier from 4.2% to 2.7% after 20 min contact, while the slurry pH shifted from 4.8 to 5.6 at 10% solids. Batches above the carbonate boundary required twice the addition level to achieve the same moisture endpoint. Storage in original sealed liners at ≤ 25 °C and <40% relative humidity is specified; opened containers are retested for loss on ignition before use.

Solution preparation for oral or topical veterinary use follows the sequence of oxide added to water under continuous agitation at 450–600 rpm in a vented vessel. Direct water addition to a static oxide bed is not permitted because the slaking reaction can generate localized temperatures above 80 °C and cause splatter of caustic slurry. The resulting stock is standardised to pH 9.5–10.5 and filtered through a 100 µm inline strainer before transfer to holding tanks. For powders, the product is incorporated by geometric dilution with the active ingredient or carrier, keeping the oxide concentration below 5.0 wt% in final dosage forms unless a higher pH is explicitly justified by the manufacturer’s stability protocol. Hard-gelatin capsules and granule lines use the 140 µm grade to reduce dusting, and the 75 µm grade is reserved for suspensions and injectable manufacturing intermediates where rapid hydration and particle-size consistency are critical.