The intramuscular injectable route for buparvaquone is developed for bovine theileriosis caused by Theileria parva and Theileria annulata. Reference veterinary protocols dose at 2.5 mg/kg body weight as a single deep intramuscular injection, and commercial injectable presentations are commonly formulated at 50 mg/mL. For a 400 kg adult animal, the dose volume becomes 20 mL, which is typically split across two injection sites to reduce local myositis and depot volume effects. The API is a lipophilic hydroxynaphthoquinone with low aqueous solubility; therefore the manufacturing stream uses a non-aqueous or water-miscible co-solvent vehicle rather than an aqueous buffer. A 316L stainless steel mixing vessel with a bottom-mounted sweep agitator is charged with the vehicle and excipients, and buparvaquone is added under low-speed mixing at a controlled temperature. Nitrogen blanketing is applied throughout the dissolution step because non-aqueous vehicles can absorb oxygen and dissolved oxygen can promote oxidation. The solution is then passed through a 0.22 µm sterilizing-grade PVDF or PTFE membrane. Filter compatibility is evaluated with the selected co-solvent system; nylon membranes are excluded where the vehicle contains aprotic or acidic solvent components. Pre-filtration bioburden is controlled below 10 CFU/100 mL, and filter integrity is tested by bubble point or forward-flow method according to the membrane manufacturer’s bulletin. The filled injection is tested for sterility by USP <71>, bacterial endotoxins by USP <85>, and particulate matter by USP <788>. Because the product is non-aqueous, water content is monitored by Karl Fischer titration and held below the limit established during process validation; published data for the exact buparvaquone non-aqueous water tolerance is limited. Filling is performed in an ISO 14644-1 class 5 environment. Vials are depyrogenated at 250 °C for 30 minutes and sealed with halogenated butyl rubber stoppers. In-process fill volume checks are performed every 15 minutes or at the interval validated by line speed. Holding time after sterile filtration is controlled so that the total time between filtration and stoppering does not exceed the validated hold period. This injectable route is the most mature downstream sector for buparvaquone; the main production bottlenecks are filter clogging from vehicle insolubles, slow dissolution of the API in the vehicle, and residual water in transfer lines.

When Wet Granulation Replaces Direct Compression in High-Dose Buparvaquone Tablet Streams

Direct compression trials with buparvaquone as a high-dose, poorly compressible API frequently produce tablets with capping, lamination, and low tensile strength when the API mass fraction exceeds 30–40% w/w. Wet granulation is therefore selected for oral solid dosage forms in which a disintegrating tablet or a slow-release bolus is required. The granulation step is conducted in a high-shear granulator with an impeller tip speed typically in the range of 2–6 m/s; published values for buparvaquone-specific impeller speed are limited because the registered oral tablet estate is smaller than the injectable estate. Granulating fluid is added at a controlled rate, and the moisture end point is determined by power consumption or torque rise rather than by fixed time. Over-wetting above 35% w/w liquid addition can produce granules with a median size above 1.0 mm, which leads to poor flow in the tablet feed frame and slower disintegration. The wet mass is transferred to a fluid-bed dryer with inlet air temperature not exceeding 60 °C for this non-salt API; higher inlet temperatures can case-harden granules and trap residual solvent. Drying is continued until loss on drying reaches the validated range, commonly 1.5–2.5% w/w. The dried granules are milled through a 0.8 mm or 1.0 mm screen and blended with extragranular disintegrant, glidant, and lubricant. Magnesium stearate is added at 0.5–1.0% w/w and blended for a short period, typically 3–5 minutes, because hydrophobic lubricant over-blending retards dissolution. Tablets are compressed on a rotary press with a compression force range that is product-specific; common tooling sizes for veterinary boluses may be 12–20 mm. Hardness, friability, disintegration, and dissolution are tested according to USP <711> and the relevant veterinary monograph where one exists. Because buparvaquone has low aqueous solubility, sink conditions may not be achieved in standard media without a validated surfactant; dissolution method development therefore requires justification of the surfactant type and concentration. The tablet route is used in small-ruminant and experimental therapeutic protocols where parenteral administration is impractical; published data for a compendial buparvaquone tablet monograph is limited.

On rotary capsule-filling machines, buparvaquone API with a micronized particle size distribution and low bulk density creates flow-related weight variability when the machine is run at high dosing disc speeds. Automatic capsule fillers use tamping pins to compress the powder bed into the dosing disc; if the API is cohesive, the fill weight drifts during the first 10–15 minutes of the run until the powder bed reaches equilibrium. Operators typically run the machine at the lower end of its speed range, use a force feeder with an agitator set to avoid shear-induced segregation, and add colloidal silicon dioxide at a level not exceeding 0.5% w/w because higher levels can reduce dissolution from the gelatin or HPMC capsule shell. If the formulation is granulated before capsule filling, granule size and flowability improve, but the capsule fill volume may then require adjustment because granulated material has lower bulk density than a direct-compression blend. Capsule strengths are selected for dose titration in smaller animals or for research protocols; unit doses must comply with uniformity of dosage units by USP <905>. Dissolution testing follows USP <711> with the same surfactant justification required for tablets. Moisture protection is important because the capsule shell can absorb water and affect the dissolution of a poorly soluble API; capsules are therefore packed in aluminium foil blisters or HDPE bottles with desiccant. Published data for buparvaquone capsule production speed limits and capsule-specific dissolution profiles is limited. The capsule route is technically feasible but less common than the injectable route; the main process failure mode is fill weight variation caused by dense API particles segregating in the powder bed.

Why Does Top-Dress Granulation Demand a Defined Sieve Cut for Dose Uniformity?

Top-dressing of buparvaquone granules onto concentrate feed uses the granule size distribution as the primary control for dose uniformity in the final feed mixture. If the API-containing granules contain a large fine fraction below 75 µm, the fines adhere to mixer walls and create cross-contamination and operator exposure during transfer. If the oversize fraction above 1.0 mm is too high, the granules segregate in auger systems and the active dose per unit of feed becomes non-uniform. A defined sieve cut, commonly in the 250–850 µm range for oral feed granules, is used to align granule density and shape with the feed carrier particles. Granulation is performed by low-shear wet granulation or roller compaction. In roller compaction, ribbon density is controlled within a narrow range because an overly dense ribbon produces hard granules that do not disperse in feed; an under-compacted ribbon produces excessive fines. The granule moisture content is controlled below the validated limit, and the granules are packed in foil-lined bags with a desiccant to prevent caking in humid storage. Blend uniformity testing follows USP <905>, and the finished feed premix is tested by a validated HPLC assay. Dissolution testing for granules may require a surfactant in the medium; if the granule is intended to be mixed with feed, the test vessel can be used with a sinker or a modified apparatus depending on the regional regulatory filing. Published data for buparvaquone top-dressing granule performance in commercial feed mills is limited. The granule route is relevant for calves and young stock where oral administration through feed avoids the stress of injection; however, regional authorization must confirm the target species and dosing schedule.

Release testing for buparvaquone API used across injectable, tablet, capsule, and granule applications is organized around impurity control, moisture, assay, and particle characteristics where relevant. Impurity testing is conducted by reverse-phase HPLC with UV detection at a wavelength selected from the API absorption maximum. System suitability criteria include resolution between buparvaquone and the nearest related hydroxynaphthoquinone peak of not less than 2.0, and a tailing factor not more than 2.0. Related substances are reported, identified, and qualified according to ICH Q3A (R2) and VICH GL10. Residual solvents are controlled under VICH GL18, and elemental impurities are controlled according to ICH Q3D. For non-sterile oral solid dosage forms, microbial enumeration tests are carried out by USP <61> and USP <62>. For sterile injectables, the tests shift to USP <71>, USP <85>, and USP <788>. The API incoming particle size distribution is measured by laser diffraction and is reported as D10, D50, and D90; this becomes critical when the same API lot is used for direct compression or low-speed capsule filling. In a multi-dosage-form release program, a single API specification is rarely sufficient; the injectable route may require a lower bioburden and endotoxin limit than the oral granule route, while the tablet route may require a finer particle size distribution. The analytical control package is governed by ICH Q6A for specification setting and ICH Q7 for API GMP. No compendial monograph for buparvaquone API exists in all major pharmacopoeias; therefore the manufacturer’s validated methods become the regulatory reference.

Non-Aqueous Vehicle Selection and Sterilizing-Grade Filtration for Buparvaquone Parenterals

In non-aqueous injectable manufacturing, the choice of vehicle determines both the filtration throughput and the injection-site tolerance. Buparvaquone is poorly water-soluble, so the vehicle system is formulated with a water-miscible co-solvent or a water-immiscible ester-like solvent. Sterilizing-grade filtration uses a 0.22 µm membrane, but the filter membrane must be qualified for the selected solvent system because some vehicles swell nylon or degrade polysulfone supports. A PVDF or PTFE membrane is usually selected. Pre-filtration through a 0.45 µm membrane reduces bioburden and protects the final sterilizing filter from particulate load. The solution is mixed in a closed vessel with nitrogen overlay; moisture ingress is limited because water can cause the API to precipitate and can shift the solution pH. If the vehicle contains a low-boiling co-solvent, filling is performed at a controlled temperature below the solvent flash point and the line is explosion-proof. The fill volume for a 50 mg/mL product is set by the dose calculation; for a 400 kg animal at 2.5 mg/kg, the fill volume is 20 mL. In-line checkweighing is used to reject units outside the validated fill volume tolerance. After filtration, filter integrity is tested by bubble point or forward-flow before and after filling. If the filter integrity test fails after filling, the batch is rejected unless a validated re-filtration procedure exists. Terminal moist-heat sterilization of the final non-aqueous product is avoided unless the formulation is shown to be stable at 121 °C; heat transfer in non-aqueous liquids is slower than in water, and the product load may require extended equilibration times that can increase impurities. Published data for buparvaquone terminal sterilization in non-aqueous vehicles is limited, so aseptic filtration remains the standard route. Primary packaging consists of Type I glass vials sealed with halogenated butyl rubber stoppers and aluminium caps. Vials are washed, depyrogenated, and filled under ISO 14644-1 class 5 conditions. The line clearance between buparvaquone and other injectable APIs is critical because beta-lactam or penem residue would require separate dedicated lines. In a multi-product facility, buparvaquone injectables are scheduled after non-potent compounds or on dedicated equipment to avoid cross-contamination and to comply with 21 CFR 211.67 cleaning validation.