Clotrimazole Ointment Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions is a supply-grade descriptor for the imidazole antifungal 1-[(2-chlorophenyl)diphenylmethyl]-1H-imidazole, CAS 23593-75-1, molecular formula C22H17ClN2, relative molecular mass 344.84 g/mol. The product is a white to pale-yellow crystalline powder controlled against the current Clotrimazole monograph in USP-NF and Ph. Eur.; veterinary-grade qualification requires the batch certificate to report residual solvents under ICH Q3C / VICH GL18, elemental impurities under the relevant ICH/VICH guidance, and stability data suitable for veterinary medicinal product registration. The phrase “Ointment Veterinary Grade” indicates that particle-size distribution, microbial enumeration, and documentation are suitable for topical semisolid manufacturing; the same active may be used in the other listed dosage forms only after downstream formulation risk assessment.

Model: The API is not defined by a harmonized public model number. Commercial lots are assigned supplier-specific grade codes that distinguish air-jet-micronized powder for ointments and suspensions from unmicronized powder for granulated tablets or feed premixes. These codes appear on the certificate of analysis; the purchase specification should fix particle-size range, bulk density, residual solvent profile, and endotoxin status when the title extends to injections or solutions.

What Specification Limits Are Applied to Clotrimazole Veterinary Grade API?

Clotrimazole is an imidazole base, not a salt; assay is expressed on the dried basis and no counterion correction is applied. The release specification combines compendial and veterinary supply requirements. Typical compendial acceptance values are shown below; supplier limits may be tighter.

The low aqueous solubility of clotrimazole is documented in compendial solubility statements; the compound is practically insoluble in water and soluble in organic solvents such as ethanol, acetone, and chloroform. This property drives dissolution, granulation, and particle-size decisions. Particle size is measured by laser diffraction according to ISO 13320:2020; a D90 below 20 µm is often required for topical semisolid products to avoid grittiness, but the exact limit is product-specific. Published industrial data for clotrimazole veterinary suspension particle-size thresholds are limited.

Veterinary-grade materials are also expected to support batch-to-batch consistency. A production campaign may show differences in bulk density between air-jet-micronized lots and hammer-milled lots; therefore the certificate of analysis should report bulk density, tapped density, Hausner ratio, and particle-size distribution. Air-jet-micronized lots often have low bulk density and high static charge; this is not a specification failure but changes handling and blending. The material should be stored in airtight containers below 25 °C and protected from light. The manufacturer should assign retest intervals based on ICH Q1A stability data; published data for clotrimazole veterinary grade API in long-term storage at 25 °C/60% RH are product-specific but generally support a retest interval when container closure remains intact.

Because the API is hydrophobic and often cohesive, direct compression of low-dose clotrimazole tablets is rarely robust. Shear cell testing according to ASTM D6128-22 provides flow function coefficient; a value below 4 indicates a cohesive powder and normally precludes direct compression without glidants. Production-scale batches of low-dose azole tablets have shown weight variation and content uniformity failures when unmicronized API is blended with direct-compression excipients; these failures are detected by USP 905 acceptance value. Excipient moisture should be kept below 2.0% w/w when ambient relative humidity exceeds 60%, because moisture can aggravate cohesion and die-fill variability.

Dissolution testing of clotrimazole solid dosage forms is complicated by pH-dependent solubility. In acidic media, the imidazole nitrogen can protonate and increase solubility; in neutral phosphate buffer, the compound remains largely undissolved. USP 711 permits surfactants when justified. Sodium lauryl sulfate at 0.1–0.5% w/v is commonly used to achieve sink conditions, but the lowest concentration that provides sink conditions should be chosen. Failing to establish sink conditions produces artificially low dissolution and may confound formulation comparisons.

When High-Shear Granulation Is Required for Clotrimazole Tablets

Wet granulation with a hydroalcoholic binder is preferred. Water alone is not recommended because the hydrophobic crystal surface prevents uniform liquid distribution. A binder solution of povidone K30 at 5–10% solids in ethanol or isopropanol is added at a controlled rate in a high-shear mixer; end-point is determined by impeller torque or power consumption. After wet screening through a 1.0–2.0 mm screen, granules are dried in a fluid-bed dryer with inlet air temperature controlled below 50 °C to avoid softening and residual solvent carryover. Dried granules are screened and blended with disintegrant and lubricant. On a rotary tablet press, low-dose tablets require tight granule particle-size control; a granule D50 between 100 µm and 250 µm is a typical starting range, but published data for this specific API is limited and the final range must be confirmed by dissolution and content uniformity studies.

For capsules, direct filling of micronized clotrimazole is difficult due to cohesive flow and dusting; granulation or slugging improves flow and reduces dust. Capsule content uniformity is evaluated under USP 905, and dissolution is run using USP 711 with a medium that provides sink conditions. Powders and granules for veterinary oral administration should be geometrically diluted with lactose or starch carriers. Segregation risk increases at low drug loadings below 1% w/w due to differences in particle size, shape, and density.

Premix Stability and Carrier Adsorption Behaviour in Medicated Feed

Clotrimazole premix is a low-inclusion medicated feed intermediate. In ribbon blenders or V-blenders, micronized API can segregate onto vessel surfaces and into dust fractions because of electrostatic charge. Geometric dilution with a carrier such as lactose monohydrate or corn starch is required; mixing time must be validated by HPLC assay uniformity across top, middle, and discharge sampling points. Carriers should be selected with a particle-size distribution overlapping the API to reduce percolation segregation. Low-inclusion premixes below 0.1% w/w generally require two-step dilution. No general compendial monograph exists for clotrimazole feed premix; the release specification is established by the marketing authorisation holder and must include assay, uniformity, moisture, and degradation products. HPLC methods used for premix assay should be validated for specificity, linearity, accuracy, and precision according to ICH Q2(R1).

Ointment processing with clotrimazole veterinary grade API normally requires micronized material and levigation into a hydrophobic or anhydrous base such as white petrolatum, mineral oil, or a non-aqueous ointment base. The API is dispersed in the molten base; processing temperatures are usually limited to below 60 °C to prevent polymorphic change and protect heat-sensitive components, although the clotrimazole melting range is 141–145 °C. After cooling, an ointment mill or three-roll mill reduces agglomerates. Final semisolid quality is assessed by microscopic examination and texture, with input API D90 controlled by ISO 13320:2020. In aqueous creams, the API is dissolved in the oil phase or suspended in the external phase; a high-shear mixer is used to disperse the powder before thickening agent hydration. During transfer of micronized clotrimazole to the ointment base, dust containment and local exhaust ventilation are required because the compound is a potent azole; powder handling should follow current occupational hygiene standards.

Topical solutions and sprays are prepared by dissolving clotrimazole in ethanol, isopropanol, propylene glycol, or a mixture; because the API is practically insoluble in water, aqueous dilution above a critical ratio causes precipitation. The concentration in commercial veterinary topical solutions is often 1% w/v, but this is a formulation value and not a solubility limit. For injectable solutions, the product title includes injections as a possible dosage form, but the formulation challenge is severe: simple aqueous injection is not feasible, and non-aqueous vehicles or cyclodextrin complexation are required. Published data for veterinary parenteral clotrimazole are limited; any injectable use must be supported by dedicated toxicology, local tolerance, and stability studies, and the API lot must meet bacterial endotoxin limits. Non-aqueous vehicles containing propylene glycol and ethanol must be evaluated for precipitation upon dilution with simulated plasma; dynamic light scattering or filtration can detect submicron precipitate. The material should not be assumed injectable-grade unless the certificate of analysis explicitly certifies endotoxin and sterile API status.

Comparative Positions of Clotrimazole Against Other Azole and Allylamine Antifungals

The main difference between clotrimazole and other veterinary antifungal actives is not always antifungal spectrum but physicochemical behaviour and route dependency. Clotrimazole is an imidazole, not a triazole; it inhibits lanosterol 14α-demethylase in fungal ergosterol biosynthesis. Its high lipophilicity and poor aqueous solubility keep it largely in the skin, mucosa, or gut lumen, whereas fluconazole has sufficient water solubility for systemic intravenous use. Compared with miconazole, another imidazole, clotrimazole is supplied as the base, while miconazole is often used as the nitrate salt; the salt may alter dissolution and ointment compatibility. Compared with terbinafine, which inhibits squalene epoxidase, clotrimazole acts earlier in ergosterol biosynthesis and has broader topical coverage of Candida and Malassezia, but terbinafine has stronger keratophilic retention for dermatophyte control. Nystatin is a polyene that binds ergosterol directly and is not absorbed from the gastrointestinal tract; its spectrum is mainly Candida, and it has no systemic use. Ketoconazole is an imidazole with oral and topical veterinary applications, but its systemic use is restricted by hepatotoxicity and drug interaction concerns; clotrimazole is generally not used systemically because of rapid hepatic metabolism and limited bioavailability.

An ointment veterinary grade API additionally differs from a general chemical grade by microbial and particle-size controls. For cutaneous semisolids, the absence of coarse particles is a patient tolerance parameter, and the batch certificate usually includes a laser-diffraction particle-size report under ISO 13320:2020. Chemical-grade clotrimazole with the same assay value may still be unsuitable because it lacks particle-size control, residual solvent documentation, and microbial limits. Every change from this veterinary grade to a general chemical source should trigger a supplier qualification review rather than a simple certificate comparison.