Imidocarb Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions is supplied as imidocarb dipropionate, CAS 55750-06-6, molecular formula C₂₅H₃₂N₆O₅, a crystalline carbanilide-derived antiprotozoal. The non-sterile bulk grade is released against a typical specification that includes HPLC assay of 99.0–101.0% on the dried basis, total specified impurities ≤ 1.0%, unspecified impurities ≤ 0.10%, water content ≤ 1.0% by Karl Fischer, sulfated ash ≤ 0.1%, heavy metals ≤ 20 ppm under Ph. Eur. general chapter 2.4.8, and residual solvents controlled according to Ph. Eur. 5.4 and ICH Q3C: ethanol ≤ 5000 ppm, methanol ≤ 3000 ppm, and isopropanol ≤ 5000 ppm for the standard powder grade. The physical-form model is governed by particle-size distribution rather than a separate brand code: micronized injectable grade has D90 ≤ 20 µm via laser diffraction using ISO 13320:2020, tablet and capsule grade has D50 60–120 µm with bulk density 0.35–0.55 g/cm³, and granule and premix grade has retained material on a 75 µm sieve ≤ 5.0%. The material appears as a white to off-white powder and requires storage in double polyethylene bags inside aluminium-foil laminate, protected from light and moisture, with a retest period of 36 months when stored below 25 °C and at relative humidity ≤ 60%. Manufacturing is conducted under veterinary GMP aligned with 21 CFR 210/211 and VICH GL1 validation principles.

The principal veterinary use of imidocarb dipropionate is the treatment of bovine babesiosis caused by Babesia bovis and B. bigemina, bovine anaplasmosis caused by Anaplasma marginale, and equine piroplasmosis caused by Theileria equi and Babesia caballi. A representative bovine subcutaneous or intramuscular dose is 1.2 mg/kg bodyweight, while equine regimens typically use 1.0–2.0 mg/kg intramuscularly every 72 h for two to four administrations depending on parasitaemia and clinical condition. Injectable solutions are commonly formulated at 120 mg/mL imidocarb dipropionate, equivalent to approximately 84 mg/mL imidocarb base, in a sterile aqueous vehicle containing propionic acid as solubiliser and buffered to pH 4.5–6.5. Free propionic acid content must be controlled because excess ion-pairing acid depresses local pH and increases injection-site pain. During solution manufacture, nitrogen overlay is applied in compounding and filling; oxygen-sensitive degradation products are monitored by an HPLC purity threshold of ≥ 98.0% after 24 h at 25 °C under 500 lux light stress. Aseptic filtration through 0.22 µm polyethersulfone or polyvinylidene fluoride membranes is preferred where terminal sterilisation produces assay loss greater than 2.0% in stability-indicating studies. Operational boundaries include the anticholinesterase activity of imidocarb: concurrent administration with organophosphate or carbamate parasiticides is contraindicated, and intravenous administration is not recommended because of reported acute cholinergic and hypotensive effects in cattle.

Why Does the Dipropionate Salt Dominate Parenteral Veterinary Formulations?

Salt selection is the primary difference between this Veterinary Grade API and alternative imidocarb salts or other antiprotozoal actives. The dipropionate moiety provides greater lipophilicity and lower aqueous solubility at physiological pH than the dihydrochloride salt, slowing dissolution at the subcutaneous or intramuscular depot and prolonging the absorption phase. Published pharmacokinetic studies in cattle show that a single subcutaneous injection produces peak plasma concentrations within 6–12 h and detectable antiprotozoal activity for approximately 4–6 weeks. This depot behaviour supports both therapeutic clearance and short-term prophylaxis in endemic herds. However, the same lipophilicity extends tissue residue duration; published withdrawal periods vary by species and regulatory jurisdiction, and imidocarb is not authorised for use in animals producing milk for human consumption in certain markets. The dipropionate salt also differs from the hydrochloride salt in its processing profile: dipropionate exhibits lower hygroscopicity, reducing sticking and picking during tablet and capsule operations when relative humidity is controlled below 60%. Processing beyond that threshold without pre-drying causes water uptake above 1.0% and lowers blend flowability. A comparative matrix of the main veterinary antiprotozoal salts is summarised below.

The Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions differs from research-grade imidocarb hydrochloride and technical-grade imidocarb base in three production-critical ways. First, the dipropionate salt’s crystalline habit and lower hygroscopicity maintain blend flow and reduce punch filming during extended compression campaigns, whereas the hydrochloride salt requires humidity-controlled suites below 40% RH and anti-adherent excipients such as magnesium stearate at 0.5–1.0%. Second, the veterinary grade is supplied with a validated analytical dossier covering identity by infrared absorption and melting range, assay by HPLC, related substances, residual solvents, and particle-size distribution; technical-grade material may lack the impurity profile needed for a veterinary drug substance file. Third, the dipropionate salt is the form used in approved injectable solutions, so tablets, capsules, granules, and premixes produced from the same salt can be referenced to the same toxicological and residue data package, reducing the bridging burden when multiple dosage forms are registered. The base or hydrochloride salt requires salt-conversion documentation for finished-product equivalence because the active species, imidocarb free base, may exhibit different dissolution and absorption kinetics.

When the Same API Is Compressed into Tablets and Filled into Capsules

Formulation of imidocarb Veterinary Grade API into immediate-release tablets requires direct compression or dry granulation when the crystalline powder is brittle and moisture-sensitive. Direct compression is limited to low-dose strengths, typically 5–25 mg imidocarb base per tablet, because the drug’s poor compactibility at high drug load reduces tensile strength below 1.0 MPa and increases friability above 1.0% using USP <1216> as a reference. For higher-dose tablets, roller compaction is preferred over wet granulation because imidocarb dipropionate exhibits pH-dependent hydrolysis at acidic pH below 4.0. The granulation is processed on a roller compactor with roll pressure 40–80 bar, screen size 0.8–1.2 mm, and is then blended with microcrystalline cellulose and croscarmellose sodium to produce final blends with Hausner ratio ≤ 1.25 and Carr index ≤ 25%. Tablet press settings require precompression force of 5–10 kN and main compression force of 15–25 kN on a 16-station rotary press for 8 mm round tooling. Capsule filling of the same powder blend is carried out on a dosing disc or dosator capsule filler with target weight variation ≤ 4.0% RSD; dissolution testing uses 0.1 M hydrochloric acid or pH 4.5 buffer at 37 °C with USP apparatus II at 50 rpm. The dissolution medium should not exceed pH 6.8 because the dipropionate salt precipitates and underestimates release. For capsules, mass uniformity across 10 units is evaluated per USP <905>; assay and content uniformity follow the same HPLC method used for API release.

For powders and granules destined for oral administration, the product is pre-dried at 40–45 °C for 4–6 h in a vacuum tray dryer when initial water content exceeds 1.5%. Drying beyond 3 h at temperatures above 60 °C is avoided because the dipropionate salt can release propionic acid and produce an amine-like odour without significant assay loss. Near-infrared process analytical technology may be used for blend uniformity; a validated NIR model with a root mean square error of prediction ≤ 10% of the target active content is acceptable where supported by HPLC reference data. These constraints apply to all product presentations including tablets, capsules, granules, and premix powders.

Particle Engineering and Blend Uniformity Metrics in Premix and Granule Processing

For powders, granules, and medicated premixes, the primary technical risk is segregation at low active inclusion. Imidocarb Veterinary Grade API is commonly incorporated at a final premix activity of 1–10 g/kg, followed by dilution into a final feed mixture at 2–5 mg/kg for prophylactic administration or outbreak control, but the authorised dose must be confirmed against national label conditions because medicated feed approvals vary. The API is first milled through a pin mill with screen aperture 0.5 mm and then blended stepwise in a double-cone or ribbon blender. A geometric dilution scheme of 1:10 API-to-carrier, repeated over 3 stages, is used to achieve a coefficient of variation for imidocarb content ≤ 5.0% across 10 sampling points, as measured by HPLC with UV detection at the validated absorption maximum. Blend homogeneity is tested according to the principles of USP <905> and Ph. Eur. 2.9.40. On a 500 L ribbon blender, low-inclusion blend uniformity typically fails if API is charged before diluent; the order of addition is API premix, then half the diluent, blend, then the remaining diluent. Granulation for premix intermediates involves dry granulation through a Fitzmill or low-shear wet granulation with 5–10% starch paste, followed by fluid-bed drying at inlet air temperature 50–60 °C until loss on drying is ≤ 3.0%. Dust generation is controlled by the addition of 0.5–1.0% light mineral oil or vegetable oil as a dedusting agent, but oil levels above 1.5% reduce dissolution and can promote caking during 40 °C accelerated stability storage. Batches exposed to relative humidity above 65% during blending exhibit flow stoppage in transfer hoppers and should be dried before tableting or capsule filling.

Imidocarb Veterinary Grade API for Solutions is typically dissolved in a sterile vehicle containing propionic acid and water for injection. The solution is filled under nitrogen into Type I glass vials sealed with chlorobutyl rubber stoppers; headspace oxygen below 5.0% reduces oxidative discoloration. Terminal moist-heat sterilisation at 121 °C for 15 min may be applied if the finished product retains assay ≥ 98.0% and the pH shift is ≤ 0.3 units; otherwise aseptic filtration is required. The solution should not be mixed with alkaline diluents because precipitation of the dipropionate base occurs above pH 7.0. For oral powders and solutions, palatability is a constraint in equine and canine patients; the active is bitter and may require encapsulation or the addition of taste-masking polymers. Such coatings must be selected to avoid enteric release in ruminants where a rumen-stable but abomasum-releasable profile is necessary; published data for imidocarb abomasal release is limited.

Spectrum boundaries place imidocarb between Anaplasma coverage and extended tissue persistence

The product differs from diminazene aceturate in its spectrum against Anaplasma marginale and in its longer protective effect in cattle. Diminazene is effective against Babesia and Trypanosoma species but has negligible activity against Anaplasma, whereas imidocarb is used for both babesiosis and anaplasmosis in cattle. Compared with buparvaquone, which is indicated for Theileria species, imidocarb is preferred for equine piroplasmosis caused by Theileria equi and Babesia caballi but may require repeated administration in chronic carriers. The residue profiles also differ: imidocarb requires extended withdrawal periods due to tissue persistence, while diminazene and buparvaquone have their own species-specific residue restrictions. For tablet, capsule, powder, granule, and premix presentations, imidocarb is primarily used in ruminant and equine practice, whereas diminazene is more common in companion-animal and small-ruminant parenteral regimes in certain regions. The choice among these actives is therefore based not solely on in vitro potency but on species-specific parasites, tissue residue intervals, available formulation stability, and national approval status.

The primary specified impurities include process intermediates from the carbanilide synthetic route and oxidative degradants. High-performance liquid chromatography is performed on a C18 column with phosphate or acetate mobile phase at pH 3.5–4.5 and UV detection at the validated absorption maximum; the tailing factor for imidocarb must be ≤ 2.0, and resolution between imidocarb and its primary process impurity must be ≥ 2.0. A typical system suitability injection establishes theoretical plates ≥ 2000 and relative standard deviation ≤ 1.0% over six replicate injections. The method is stability-indicating; alkaline stress at pH 10 for 24 h at 60 °C increases early-eluting polar degradants, while oxidative stress with 3.0% hydrogen peroxide for 24 h produces a late-eluting impurity that must be separated from the principal peak. These method performance parameters are established under ICH Q2(R1) and are used for both API release and finished dosage form assay.