| HS Code | 627350 |
| Chemical Name | 1-Cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid |
| Cas Number | 93106-60-6 |
| Molecular Formula | C19H22FN3O3 |
| Molecular Weight | 359.4 g/mol |
| Appearance | White to pale yellow crystalline powder |
| Solubility | Slightly soluble in water; soluble in dilute alkaline and acidic solutions |
| Melting Point | Approximately 225-230°C |
| Assay Purity | 98.0% to 102.0% on a dried basis |
| Residual Solvents | Complies with ICH guidelines |
| Veterinary Grade | Suitable for veterinary pharmaceutical formulations |
| Application | Antibacterial agent used for uterine infusion and treatment of bacterial infections in veterinary medicine |
| Mechanism Of Action | Inhibits bacterial DNA gyrase (topoisomerase II), leading to bacterial cell death |
| Storage Conditions | Keep sealed, protected from light, and store in a cool, dry place |
| Shelf Life | Typically 36 months from date of manufacture |
| Available Dosage Forms | Tablets, injections, capsules, powders, granules, premix, and solutions |
As an accredited Enrofloxacin Uterine Infusion Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Enrofloxacin Uterine Infusion Veterinary Grade API is packaged in sealed double-lined drums, 25 kg per drum, ensuring stability. |
| Container Loading (20′ FCL) | One 20′ FCL containing Enrofloxacin veterinary-grade API, packed in export-grade drums for tablets, injections, capsules, powders, granules, premix, or solutions. |
| Shipping | Enrofloxacin API ships in sealed, light-protected containers to prevent degradation. Packaged per IATA/IMDG regulations, with proper labeling for veterinary pharmaceutical use. Temperature-controlled, dry environment required; avoid moisture and extreme heat. Include Material Safety Data Sheets and certificates for customs clearance. Handle carefully to maintain purity and stability during transit. |
| Storage | Store Enrofloxacin veterinary-grade API in a tightly sealed, original container, protected from light and moisture. Keep in a cool, dry, well-ventilated area at controlled room temperature (20–25°C). Avoid exposure to excessive heat or humidity. Ensure container is clearly labeled and kept out of reach of children and animals. |
| Shelf Life | Shelf life is typically 2 years when stored in a cool, dry, airtight container, protected from light and moisture. |
Bovine postpartum uterine infections in dairy and beef herds are treated with intrauterine infusion formulations in which enrofloxacin is delivered at concentrations that achieve intrauterine fluid levels above the MIC₉₀ for Trueperella pyogenes and Escherichia coli while systemic absorption is monitored through milk and plasma withdrawal periods. The finished product must comply with Commission Regulation (EU) No 37/2010, which sets the sum of enrofloxacin and ciprofloxacin MRL in bovine muscle at 100 µg/kg, liver at 200 µg/kg, kidney at 300 µg/kg, and milk at 100 µg/kg; sterility of the finished infusion is verified under Ph. Eur. 2.6.1, and bacterial endotoxin limits are assessed under Ph. Eur. 2.6.14 with an action limit of 0.50 EU/mL or lower unless otherwise justified. Addition ratios are typically 5.0 g to 10.0 g enrofloxacin per 100 mL, expressed as 5%–10% w/v, with the lower end reserved for formulations containing a polymeric viscosity modifier such as hypromellose or sodium carboxymethylcellulose at 0.5%–1.5% w/v to extend intrauterine retention, and the higher end used when the product is intended for single-dose administration at 2.5–5.0 mg/kg body weight per day. Downstream production of sterile intrauterine suspensions or solutions uses a closed stainless-steel vessel equipped with a bottom-entry high-shear disperser operated at 3,000–5,000 rpm for 20–30 min, followed by pH adjustment to 4.0–5.0 with dilute hydrochloric acid or sodium hydroxide, then passage through a 0.22 µm hydrophilic PVDF or polyethersulfone membrane into an aseptic filling isolator; moist-heat terminal sterilisation is generally avoided because thermal exposure can shift pH and generate degradation products, and published data for autoclave cycles on enrofloxacin uterine formulations at 121°C is limited. Finished product types include prefilled single-dose polyethylene or polypropylene intrauterine syringes fitted with Luer lock cannulas and packaged in low-particulate polyester peel pouches, as well as vented bottle presentations for use with disposable catheters.
Compliance for medicated feed premixes containing enrofloxacin in the European Union is anchored to Regulation (EU) 2019/4 and Commission Regulation (EU) 37/2010, which fixes porcine MRL values for enrofloxacin and ciprofloxacin in muscle at 100 µg/kg, skin and fat at 100 µg/kg, liver at 200 µg/kg, and kidney at 300 µg/kg; feed-mill carryover and homogeneity criteria are governed by Annex II of Regulation (EU) 2019/4, and in-house validated cleaning limits at 1% of the lowest active concentration in the subsequent non-target batch are often applied when published regulatory default values vary by formulation and species. Residual moisture for finished granules is specified at ≤5.0% by Karl Fischer titration per Ph. Eur. 2.5.12. The API is incorporated into a lactose monohydrate or wheat bran carrier at 5%–10% w/w enrofloxacin, representing 50–100 g/kg premix potency, and is subsequently diluted in complete feed to a final concentration of 50–100 g/metric tonne, equivalent to 50–100 ppm, for growing pigs. The API particle size is controlled at D90 < 150 µm by jet milling or air-classified milling because enrofloxacin needle-like crystals produce segregation and content uniformity failures above this threshold. Downstream production employs a sequential dilution step in a twin-ribbon blender with a fill volume of 60%–70% and mixing time of 15–20 min, followed by top-spray fluid-bed granulation using an aqueous binder solution of povidone K-30 at 2%–4% w/w of dry blend, inlet air temperature 60–70°C, product temperature 35–40°C, and drying to loss-on-drying ≤3.0%. Blend uniformity is verified by sampling at 10 points with a coefficient of variation ≤5.0%, and finished granules are packed in 25 kg multi-wall paper bags with a polyethylene inner liner or in 5 kg aluminium-composite bags under nitrogen flush for feed mills equipped with automated micro-dosing systems.
Enrofloxacin water-soluble powder for poultry is formulated as an acidified granulate because the solubility of the hydrochloride salt in drinking water falls when pH rises above 6.5 and when total hardness exceeds 200 mg/L calcium carbonate equivalents. Compliance is governed by Commission Regulation (EU) 37/2010, which assigns poultry MRL values of 100 µg/kg in muscle, 100 µg/kg in skin and fat, 200 µg/kg in liver, and 300 µg/kg in kidney, but use in laying hens producing eggs for human consumption is excluded because no MRL has been established in eggs; batch release includes disintegration testing per Ph. Eur. 2.9.1 and residual moisture by Ph. Eur. 2.5.12 with a limit of ≤4.0%. API addition in the powder is commonly 10% w/w, equivalent to 100 g enrofloxacin per kg, while the final medicated drinking water is prepared at 50 mg enrofloxacin per litre for 3–5 consecutive days; under thermoneutral conditions this corresponds to approximately 10 mg/kg body weight per day in broilers when water intake approaches 180–220 mL/kg per day. The production process blends jet-milled enrofloxacin with dextrose monohydrate, anhydrous citric acid at 10%–20% w/w, and a low-foaming dispersant such as poloxamer 188 at 0.2%–0.5% w/w in a high-shear granulator at 800–1,200 rpm for 3–5 min, then wet-masses with ethanol and dries in a vacuum dryer at 40–45°C to preserve acidulant activity. The resulting granulate is sieved to 0.5–1.0 mm and packed in 100 g, 500 g, and 1 kg heat-sealed aluminium-foil sachets. Terminal finished product types include water-soluble powders and effervescent granules for farm water proportioners, with the acidified matrix maintaining a pH of 3.5–4.5 after dilution in typical farm water lines.
In companion animal dose forms, enrofloxacin hydrochloride is selected over the free base because the salt provides reproducible aqueous solubility during dissolution testing while retaining acceptable stability in dry-granulation and direct-compression processes. In the United States, enrofloxacin tablets are regulated under 21 CFR 520.804, and the corresponding injectable solution appears in 21 CFR 522.804; finished tablet release includes uniformity of dosage units per Ph. Eur. 2.9.40 or USP <905>, and dissolution testing is conducted in 0.1 M hydrochloric acid at 37°C with a paddle apparatus at 50 rpm, although published data for a fully harmonised enrofloxacin dissolution standard is limited and a Q value of 75% at 45 min is used for immediate-release tablets under validated in-house methods. Stability protocols follow VICH GL 3 and residual solvent limits follow VICH GL 18. Tablet cores contain 22.7 mg, 68 mg, or 136 mg enrofloxacin per unit, and the API-to-core mass ratio is usually 25%–35% w/w, with silicified microcrystalline cellulose at 20%–35% w/w, lactose monohydrate or dicalcium phosphate dihydrate at 20%–30% w/w, crospovidone at 2%–5% w/w, colloidal silicon dioxide at 0.5%–1.0% w/w, and magnesium stearate at 0.5%–1.0% w/w; capsules may use a dry-filled enrofloxacin hydrochloride powder at 10%–30% w/w with microcrystalline cellulose as filler. The process proceeds by roller compaction dry granulation at 4–8 kN/cm roll force and 1.5–2.0 mm screen size because enrofloxacin displays poor flow with a Carr index often above 30, then compression on a rotary tablet press at 10–15 kN main compression force and target hardness of 80–120 N; a film coating of polyvinyl alcohol-based Opadry II is applied to a 3% w/w weight gain to reduce bitterness and improve handling in automated bottle lines. Final presentations include 10-count and 100-count HDPE bottles with child-resistant closures, unit-dose blisters using PVdC-coated aluminium foil, and veterinary clinic dispensing packs, with light protection below 25°C and relative humidity ≤60%.
Enrofloxacin injectable solutions are produced at 50 mg/mL or 100 mg/mL potencies, and the formulation must address the zwitterionic nature of enrofloxacin by maintaining a final pH of 3.5–5.0, because aqueous solubility falls sharply above the isoelectric point and precipitation occurs at neutral pH in the presence of phosphate or bicarbonate buffers. Sterility is governed by Ph. Eur. 5.1.1, bacterial endotoxin limits by Ph. Eur. 2.6.14 with a limit of ≤0.50 EU/mg for veterinary parenterals, residual solvent control by VICH GL 18, and the US filing for the 100 mg/mL product falls under 21 CFR 522.804. The formulation incorporates 100 g enrofloxacin per litre, expressed as 10% w/v, with pH adjustment using hydrochloric acid or sodium hydroxide; for multidose presentations, benzyl alcohol at 0.5%–2.0% v/v or a combination of propyl gallate and disodium edetate may be included as an antimicrobial preservative and antioxidant system, and water for injection serves as the continuous phase after nitrogen sparging to keep dissolved oxygen below 0.5 mg/L. The production train begins with dissolution in a jacketed stainless-steel reactor at 40–50°C under sustained agitation at 150–250 rpm for 30–45 min, followed by cooling to 20–25°C, pH adjustment, and pre-filtration through a 0.45 µm polyethersulfone membrane before sterilising filtration through two serial 0.22 µm membrane filters; filling then proceeds in a Grade A isolator into amber Type I glass vials of 50 mL, 100 mL, or 250 mL with chlorobutyl rubber stoppers and aluminium flip-off seals. Terminal finished product types are sterile injectable solutions for subcutaneous, intramuscular, or slow intravenous administration in cattle, swine, dogs, and cats, and vials are protected from light to limit photodegradation; terminal autoclaving is generally avoided because published stability data for moist-heat cycles on enrofloxacin solutions is limited and sterile filtration remains the preferred sterility assurance route.
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Enrofloxacin Uterine Infusion Veterinary Grade API (CAS 93106-60-6, molecular formula C19H22FN3O3, molecular weight 359.39 g/mol) is supplied as a white to pale yellow crystalline powder for formulation into sterile intrauterine suspensions, injectable solutions, tablets, capsules, oral powders, granules, premixes, and concentrated solutions. The product is identified in manufacturer documentation by a grade code that varies between suppliers; the designation commonly carries the suffix “INF” or “UI” when the lot meets intrauterine low-endotoxin release criteria. End users should match the certificate of analysis to the intended pharmacopoeial monograph rather than relying on a single universal model code. Representative release specifications include assay on dried basis between 98.0% and 102.0%, loss on drying ≤1.0%, residue on ignition ≤0.1%, and total related substances ≤2.0% with individual impurities ≤0.5% as determined by validated HPLC. Because enrofloxacin is amphoteric, its aqueous solubility is pH-dependent; this property controls both dissolution in parenteral vehicles and absorption after intrauterine administration.
In intrauterine formulations, the critical quality attribute is not chemical purity alone but bacterial endotoxin burden. The uterine infusion grade is released with endotoxin level ≤0.5 EU/mg by Ph. Eur. 2.6.14 kinetic chromogenic assay, whereas standard oral-grade enrofloxacin may be released at ≤2.5 EU/mg or higher unless otherwise specified. Total aerobic microbial count is controlled to ≤100 CFU/g and total combined yeasts and molds to ≤10 CFU/g by Ph. Eur. 2.6.12 and 2.6.13, respectively. The API is not terminally sterilized at the bulk stage; it is intended for aseptic compounding or terminal sterilization of the finished solution or suspension. Manufacturing lines that incorporate a 0.2 µm sterilizing-grade filter upstream of filling must first prefilter through a 0.45 µm depth or membrane filter because enrofloxacin suspensions show rapid fouling when particle size D90 exceeds 50 µm. In production-scale campaigns, endotoxin reduction alone does not guarantee pyrogen-free final product: depyrogenation of stainless steel 316L vessels with dry heat at 250 °C for 30 min is required for product-contact surfaces after cleaning, as residual endotoxin adsorbs to vessel walls.
For injectable and uterine infusion solutions, terminal moist-heat sterilization is generally conducted at 121 °C for 15 min in a saturated steam autoclave with load probes in the cold spot. The formulation pH is maintained between 4.0 and 5.5 using citric acid or gluconic acid buffers; at pH above 7.0, pronounced yellow-to-amber coloration and related substance growth occur during heating. The ampoule or vial headspace should be sparged with nitrogen because enrofloxacin is photosensitive and oxygen-sensitive under alkaline conditions. Terminal sterilization of suspensions requires a viscosity target of 15–50 mPa·s at 25 °C measured by Brookfield viscometer spindle LV-2 at 60 rpm, sufficient to prevent sedimentation during the autoclave cycle but low enough to allow syringeability through 16G or 18G infusion needles. Published data for the interaction of enrofloxacin with heat-stable suspending agents in the uterus is limited; therefore, stability-indicating HPLC should be performed on the final formulation at 40 °C/75% RH for 6 months to establish a formulation-specific shelf life.
Direct compression of enrofloxacin into tablets is possible only when the API D90 is ≤150 µm and the Hausner ratio is ≤1.25, as measured by USP <1174> powder flow analysis. At above 60% RH, the API is pre-dried at 60 °C for 4 h before blending with microcrystalline cellulose and sodium starch glycolate in a bin blender filled to 60–70% of capacity. Tablets manufactured on a rotary press at 60–100 rpm with compression force 8–15 kN show acceptable weight uniformity when the fill variation is ±3.0% or tighter. Capsule filling with tamping pins requires bulk density 0.45–0.60 g/mL and a tapped density no more than 20% higher than bulk density to reduce weight variation. These parameters are normal production boundaries for poorly compressible, moisture-sensitive APIs and are not specific chemical stabilisation data for enrofloxacin.
Although thermodynamic solubility is a molecular property, the observed dissolution rate in a uterine infusion vehicle depends strongly on particle size distribution and polymorphic form. Micronization of enrofloxacin to a D90 ≤25 µm increases the specific surface area and reduces the time to reach saturation, but overmicronization below D90 ≤5 µm may increase static charge and agglomeration when transferred through pneumatic conveyors. Laser diffraction analysis per ISO 13320 with wet dispersion in water containing 0.1% polysorbate 80 is used to monitor the size distribution; dry dispersion without dispersant produces artificially broad distributions because of electrostatic clustering. In aqueous suspension processing, rotor-stator homogenization at tip speeds of 10–20 m/s for 20–30 min yields a homogeneous slurry without temperature rise above 30 °C, which is critical because local heating above 40 °C can increase amorphous content and accelerate recrystallization during storage. Differential scanning calorimetry of the API typically shows a melting endotherm at 219–221 °C; the presence of a shoulder below 210 °C indicates amorphous content or a second polymorph and is a release criterion only if validated by X-ray powder diffraction.
For solutions, particle size is irrelevant after complete dissolution, but the API must be dissolved in stages. Typical dissolution protocols add enrofloxacin to water at 35–45 °C under constant agitation at pH 3.0–3.5, then back-titrate with sodium hydroxide to pH 4.5–5.5. Direct addition to neutral buffer produces a gummy precipitate that is difficult to dissolve even with prolonged mix time. The addition rate should not exceed 2.5 kg/min per 1000 L vessel to avoid localized supersaturation and agglomeration on baffles; in production-scale campaigns, high-speed dispersers with tip speeds below 15 m/s prevent foam generation while maintaining sufficient mass transfer. After complete dissolution, the solution is cooled to 20–25 °C and filtered through a 0.45 µm membrane prior to sterile filtration. The pH-dependent solubility requirement means that the same grade cannot be directly substituted into neutral oral solutions without adjustment.
Distribution of the API onto lactose monohydrate, dextrose, or corncob carriers in a ploughshare mixer with chopper speed 1500–3000 rpm provides a mixing coefficient of variation below 5.0% for a 1:1000 dilution when sampled per ISO 6497. If the carrier has moisture above 1.0%, enrofloxacin particles adhere to metallic surfaces and cause cross-batch carryover; therefore, the carrier is pre-dried at 70 °C until moisture is ≤1.0%. The use of mineral clays or bentonite is not recommended because adsorption to aluminosilicate surfaces reduces the feed concentration of enrofloxacin below the labeled level after 24 h storage in silos. Granulation of premixes in a fluid-bed granulator with inlet air temperature 45–55 °C and product temperature 28–35 °C reduces dust and segregation but requires a binder solution pH below 5.0 to avoid dissolution of enrofloxacin and subsequent recrystallization on the granule surface. The final granules should be passed through a 1.0 mm screen and have a friability below 1.0% to withstand pneumatic transfer to bags or bulk trucks.
Because enrofloxacin carries both a carboxylic acid and a piperazinyl amine, pH adjustment in either direction increases solubility, but the choice of acid or base is restricted by compatibility and sterility. Hydrochloric acid is used only in glass-lined or 316L steel vessels at concentrations below 0.5 M; prolonged contact with stainless steel above 40 °C can release iron ions that complex with the quinolone carbonyl group and form colored degradation products. Citric acid is preferred for oral and intrauterine buffering because it provides pH 3.0–3.5 for initial dissolution and acts as a chelating agent for trace metal ions. Phosphate buffers are not used in enrofloxacin injection vehicles because the API can precipitate as a phosphate salt when the pH is raised above 5.0 and when calcium or magnesium ions are present from water hardness. Chelating agents such as disodium edetate at 0.01–0.05% w/v are included to stabilize the solution against metal-catalyzed oxidation, but edetate levels above 0.1% w/v may cause local tissue irritation after intrauterine infusion. For injection vials, the fill volume is standardized to 10 mL, 50 mL, or 100 mL Type I glass vials sealed with halogenated butyl rubber stoppers; the stopper should be siliconized with a layer not exceeding 0.5 mg/dm² to avoid particulate shedding during needle puncture.
During terminal sterilization, the cold spot is monitored with a validated F0 value of ≥15 min; for heat-sensitive formulations containing enrofloxacin, the F0 may be reduced to ≥8 min only if pre-sterilization bioburden is ≤10 CFU/100 mL and the product is intended for intrauterine administration in non-systemic infections. This is an operational boundary derived from sterilization chapters and ICH Q8 quality-by-design principles. The API manufacturer’s certificate of analysis should include residual solvent levels per ICH Q3C; for the low-endotoxin grade, acetonitrile, dichloromethane, and methanol are commonly controlled at Class 2 and Class 3 limits by headspace gas chromatography. The absence of pyrogens does not imply the absence of particulate matter; final solutions should meet USP <788> particulate matter limits for injections, with ≤6000 particles/container ≥10 µm and ≤600 particles/container ≥25 µm.
The table below compares the low-endotoxin uterine infusion grade with a standard oral premix grade. The values are representative release limits found in pharmacopoeial monographs and manufacturer specifications; each lot should be verified against the approved certificate of analysis.
| Parameter | Uterine Infusion Grade | Standard Oral/Premix Grade | Test Method |
|---|---|---|---|
| Assay (dried basis) | 98.0–102.0% | 98.0–102.0% | HPLC |
| Bacterial endotoxins | ≤0.5 EU/mg | ≤2.5 EU/mg or as agreed | Ph. Eur. 2.6.14 |
| Total aerobic microbial count | ≤100 CFU/g | ≤1000 CFU/g | Ph. Eur. 2.6.12 |
| Particle size D90 | ≤50 µm for suspension; ≤25 µm for sterile filtration | ≤200 µm | ISO 13320 |
| Loss on drying | ≤1.0% | ≤1.0% | Ph. Eur. 2.2.32 |
| Elemental impurities | ICH Q3D injection route limits | ICH Q3D oral route limits | ICP-MS |
| Residual solvents | ICH Q3C Class 2/3 limits | ICH Q3C Class 2/3 limits | GC-HS |
| Packaging | Double LDPE bags under nitrogen in aluminium drum | LDPE bag in fiber drum | Internal SOP |
Route-specific control limits and process failure modes observed on production-scale equipment are summarized below. These are empirical boundaries for planning, not substitutes for formulation-specific validation.
| Formulation Route | Critical API Parameter | Processing Boundary | Known Failure Mode |
|---|---|---|---|
| Uterine infusion suspension | Endotoxin ≤0.5 EU/mg; D90 ≤50 µm | Terminal autoclave 121 °C 15 min; pH 4.0–5.5 | Sedimentation caking after cooling if viscosity is below 15 mPa·s |
| Injectable solution | Clarity after 0.45 µm filtration; residual metals | Dissolve at pH 3.0–3.5; back-titrate to 4.5–5.5 | Precipitation during autoclave cooling when pH exceeds 5.5 |
| Tablet/capsule | D90 ≤150 µm; Hausner ratio ≤1.25 | Pre-dry at 60 °C for 4 h if RH exceeds 60% | Weight variation from agglomerated fines |
| Premix/granules | Bulk density 0.45–0.60 g/mL; moisture ≤1.0% | Ploughshare mixing 10–15 min at 60–80% fill | Segregation of API during pneumatic transfer |
| Concentrated oral solution | Solubility at pH 3.0–4.0; light protection | Nitrogen purge; amber container | Photodegradation under UV exposure |
A distinguishing feature of the uterine infusion grade is its controlled particle size distribution suitable for aqueous suspension and its low endotoxin load, whereas standard oral premix grade allows coarser particles and higher bioburden. The low-endotoxin grade is not intended for direct use as a sterile API; it requires terminal sterilization or aseptic processing at the finished-product stage. Compared with enrofloxacin hydrochloride, the base has lower aqueous solubility in neutral water, but it is preferred in dry premixes and suspensions because it contributes no chloride ion and is less hygroscopic. In contrast, enrofloxacin hydrochloride may be selected for concentrated injectables where rapid dissolution in water is required; however, the hydrochloride salt imposes stricter packaging requirements because moisture uptake can cause deliquescence and caking in single-use bags. The base grade described here is also differentiated from microencapsulated or taste-masked grades intended for palatable oral tablets; those products use polymer coatings that alter release profiles and are outside the scope of the API specification.
Storage limits for this API are defined by the manufacturer’s established stability data. In the absence of specific long-term data for a given customer formulation, the unopened API is typically stored below 25 °C in a dry area protected from light. The inner LDPE liner is purged with nitrogen to maintain residual oxygen below 2.0%; once opened, the material should be used within 30 days or re-validated for moisture and bioburden. High humidity above 60% RH causes particle agglomeration, while prolonged exposure to ultraviolet light above 200 W/m² in the 320–400 nm range accelerates photodegradation. These constraints are operational boundaries rather than absolute incompatibilities.
