| HS Code | 794427 |
| Product Name | Dimpylate Veterinary Grade API |
| Chemical Name | O,O-Diethyl O-(2-isopropyl-6-methylpyrimidin-4-yl) phosphorothioate |
| Cas Number | 333-41-5 |
| Molecular Formula | C12H21N2O3PS |
| Molecular Weight | 304.35 g/mol |
| Appearance | Colorless to pale yellow clear liquid |
| Solubility | Practically insoluble in water; miscible with ethanol, acetone, xylene, and most organic solvents |
| Boiling Point | 306°C at 760 mmHg with decomposition |
| Purity | Veterinary grade, typically ≥ 95% assay |
| Mechanism Of Action | Inhibits acetylcholinesterase, causing accumulation of acetylcholine and disruption of nerve function in parasites |
| Stability | Stable under normal handling conditions; hydrolyzes in strong acids and alkalis; decomposes when exposed to UV light |
| Storage Conditions | Store in tightly sealed original containers in a cool, dry, well-ventilated area, protected from light and moisture |
As an accredited Dimpylate 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 | Available in 25 kg sealed multi-layer drums, packed to protect Dimpylate Veterinary Grade API for tablets, injections, capsules, powders, granules, premix, and solutions. |
| Container Loading (20′ FCL) | Dimpylate veterinary API packed in sealed containers, palletized and secured, loaded into 20-foot FCL for safe transport. |
| Shipping | Dimpylate Veterinary Grade API is shipped in sealed, UN-approved containers with tamper-evident liners, labeled per hazardous-goods regulations. Shipments include safety data sheets and certificates of analysis. Transport is temperature-controlled, dry, and ventilated, with full compliance for road, sea, or air freight. Proper handling and segregation prevent contamination and ensure stability. |
| Storage | Store Dimpylate Veterinary Grade API in tightly sealed, original containers in a cool, dry, well-ventilated area. Protect from light, moisture, and heat; avoid direct sunlight. Maintain moderate room temperature. Keep away from oxidizing agents, food, feed, and incompatible materials. Ensure proper labeling and segregation. |
| Shelf Life | Shelf life is 24 months when stored in a cool, dry, tightly sealed container, protected from light. |
Production-scale sheep dips using dimpylate as the sole organophosphate ectoparasiticide are prepared from a 250 g/L emulsifiable concentrate. A 600 L cold-water charge dosed with 1.0 L concentrate yields 417 mg/L active substance (0.042% w/w), within the registered in-use band of 0.02–0.05% active substance. Emulsification is carried out by metering the concentrate into a recirculating plunge dip tank at 20–25°C; the tank is equipped with a 1,500 L/h centrifugal pump and a venturi injector to achieve oil-in-water droplet sizes below 5 µm. Water pH above 8.0 accelerates alkaline hydrolysis to 2-isopropyl-6-methyl-4-pyrimidinol and shortens the bath half-life to less than 6 h; pH is maintained between 5.5 and 7.0 with citric acid when source water hardness exceeds 250 mg/L CaCO₃. Sodium ions from hard water or residual detergents destabilise the emulsifier system, producing visible oil slicking after 4 h in batch tests. Bath replenishment on continuous units is operated by adding 0.5 L concentrate per 200 animals after the initial charge, with adjustment based on gas chromatography with nitrogen-phosphorus detection under ISO/IEC 17025. Compliance is governed by EU Regulation 2019/6 and, where applicable, Commission Regulation (EU) No 37/2010 Table 1 maximum residue limits for ovine tissues; the UK HSE Sheep Dip Code of Practice applies to worker exposure and spent dip disposal. The terminal product is an aqueous immersion solution for whole-animal plunge dipping. Tablets, injections, and capsules do not have an established downstream application under current regulatory dossiers and are excluded from the formulation scenarios below.
In cattle self-treatment stations, dust formulations for backrubbers require a free-flowing powder loaded with 2.0% w/w technical dimpylate and 3.0% w/w precipitated silica as fluidisation aid. The kaolin carrier is dried to less than 1.0% free moisture in a fluidised-bed dryer at 80°C and milled through an ASTM E11 No. 200 sieve (75 µm). A 500 kg ribbon blender at 50% fill is used; liquid dimpylate is sprayed through a positive-displacement metering pump at 2.0 bar over 15 min, followed by 10 min post-spray mixing. Oil absorption of the carrier is controlled at 0.35–0.50 mL/g to prevent soft agglomerates that block dust bag orifices. Bulk density is measured with USP 616, targeting 0.55–0.70 g/mL; material outside this range segregates in self-treatment devices and produces inconsistent delivery. The powder is manufactured under GMP conditions aligned with EudraLex Volume 4 Part II for veterinary medicinal products. The final product is a ready-to-use cattle dust bag refill powder; VICH GL10 stability data at 30°C/65% RH are required for container closure integrity and active content retention.
Manufacturing a 4.0% w/w dimpylate dust for poultry mite treatment requires control of the liquid API viscosity and carrier sorption capacity. Technical dimpylate is adsorbed onto kaolin with a d50 of 15 µm and d90 of 45 µm measured by ISO 13320:2020. The mixer is a 1,000 L ploughshare unit with high-speed choppers at 2,800 rpm; API is atomised through a heated nozzle at 40°C to reduce viscosity below 20 mPa·s before addition. Blending time is 12 min, after which a 10-point sampling plan is applied; the acceptance criterion is a relative standard deviation of active content not exceeding 5%. Jacket temperature is held at 35°C to prevent shear-induced overheating above 45°C, where carrier oil absorption falls and surface moisture triggers agglomeration. The final product is a ready-to-use poultry dusting powder applied to the vent area and litter at a label rate of 50 g per 100 birds; application must avoid feed and water surfaces. Compliance documentation includes VICH GL10 stability storage at 30°C/65% RH, Ph. Eur. 2.9.36 powder flow testing, and water content below 1.5% by USP 921 Karl Fischer titration. Worker exposure limits are set by the national authorisation and require impermeable gloves and respiratory protection during application.
When a solid polymer ear tag is required for prolonged acaricide release, twin-screw extrusion is used to incorporate 20.0% w/w dimpylate into a PVC matrix. The polymer matrix consists of 100 parts PVC, 25 phr dioctyl terephthalate plasticiser, 2 phr epoxidised soybean oil co-stabiliser, and 1 phr stearic acid external lubricant. Liquid dimpylate is introduced through a side-stuffer at zone 6 of a 40:1 L/D twin-screw extruder to reduce thermal exposure; barrel temperatures start at 150°C and do not exceed 175°C in zones 7–9, while screw torque is maintained below 85% of drive capacity. The melt is pelletised under nitrogen and injection moulded at a nozzle temperature of 170°C and mould temperature of 80°C into ear tag cavities at a clamp force above 150 t. Post-moulding annealing at 35°C for 48 h stabilises surface bloom below 0.2 mg/cm². Compliance requires residual solvent testing under VICH GL18 and extractables assessment under the national marketing authorisation. The terminal product is a solid polymer ear tag delivering acaricide by controlled surface migration.
For swine and poultry housing emptied between production cycles, premise sprays are prepared by dilution of a 500 g/L emulsifiable concentrate to 0.5% active substance (1:100 v/v) in water at pH 6.5. The concentrate used for this dilution is authorised under EU Regulation 2019/6 or national regulatory equivalents for premise spray use. Emulsion stability is verified by CIPAC MT 36.3 with no creaming or oil separation after 24 h in standard hard water C. Application equipment includes diaphragm pumps operated at 50–150 psi and flat-fan nozzles producing a volume median diameter of 200–250 µm; droplets coarser than 300 µm reduce surface coverage, while droplets finer than 100 µm increase drift and operator inhalation risk. A registered label application rate of 1 L diluted emulsion per 20 m² is applied to non-porous concrete and metal surfaces in emptied housing. The terminal product is a diluted emulsion applied to animal housing surfaces; treated structures are kept free of animals for 24 h and ventilated before re-stocking. Analytical verification of active content in the diluted spray uses ISO/IEC 17025 HPLC-UV at 254 nm, with acceptance limits of ±5% of the target concentration.
After the carrier is dried to 8.0% moisture, granular bait for fly control around animal housing is manufactured with 2.0% w/w dimpylate on corn cob granules having a sieve fraction of 600–850 µm. Liquid API is mixed with 2.5% w/w mineral oil binder in a heated vessel at 35°C and sprayed onto a tumbling bed in a 300 kg rotary drum at 20 rpm. Retention time is 18 min, followed by 24 h curing at 25°C in vented containers. Bulk density after curing is 0.40–0.48 g/mL; attrition is assessed by a 20 min rotating drum per ASTM E728-91 with loss not exceeding 5.0%. The finished product is a scatter bait applied at 1–2 kg per 500 m² to wet areas around manure storage and feed pad perimeters. Compliance is determined by the registered pesticide label for the granular product, including worker re-entry interval of 12 h unless specified otherwise. The product must not be applied to animal feed surfaces or areas where poultry may ingest granules directly.
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Dimpylate (CAS 333-41-5; molecular formula C12H21N2O3PS; relative molecular mass 304.35 g/mol) is an organophosphorothioate active ingredient supplied as a veterinary-grade API for processing into tablets, injections, capsules, powders, granules, premix, and solutions. The substance is a viscous amber liquid at 25 °C, with a water solubility of 40 mg/L and a log Kow of 3.30. These physical properties impose a formulation workflow in which the liquid API is adsorbed, dissolved, or otherwise fixed onto a carrier before tableting, encapsulation, or dry blending. The therapeutic effect against ectoparasites results from cytochrome P450-mediated oxidative desulfuration to diazoxon, which inhibits arthropod acetylcholinesterase at cholinergic synapses. This activation step is significant in solid-dose manufacturing because thermal oxidation of the P=S moiety must be controlled during drying, milling, and compaction.
No harmonized pharmacopoeial model designation exists for dimpylate veterinary-grade API. The product is identified by the manufacturer’s dossier reference, the ISO common name dimpylate, CAS 333-41-5, and the applicable veterinary marketing authorization number. In bulk supply, the material is commonly packaged in epoxy-phenolic lined steel or high-density polyethylene drums under nitrogen headspace to limit moisture ingress and oxidative degradation. Batch traceability includes lot number, retest date, and storage conditions; labelling typically directs storage at ≤ 25 °C with protection from light.
Dimpylate belongs to the pyrimidinyl organothiophosphate class and is supplied as a technical liquid. Because no harmonized Ph. Eur. or USP monograph exists for dimpylate, veterinary API release criteria are generally derived from FAO/WHO pesticide specifications, regional licensing requirements, and manufacturer stability data. The published FAO/WHO technical material specification for diazinon lists a minimum active ingredient content of 950 g/kg, water not more than 2 g/kg, and acidity not more than 2 g/kg calculated as sulfuric acid. Veterinary API grades are expected to meet or exceed these controls because formulation into low-dose veterinary products cannot tolerate excessive water, acidity, or insoluble matter. Analytical release typically includes HPLC assay, Karl Fischer water determination, acid-base titration, and gravimetric insoluble matter determination.
Residual solvent control is aligned with USP <467> and Ph. Eur. 5.4; specific solvent limits are set according to the synthesis route and the intended dosage form. Published harmonized numerical limits for individual toxicologically relevant organophosphorus impurities in veterinary-grade dimpylate are limited; each manufacturer is expected to justify impurity limits in the marketing authorization dossier using HPLC or LC-MS/MS with external reference standards. This impurity envelope is a central difference from agricultural technical material, where field efficacy rather than pharmaceutical purity governs the release decision.
| Control parameter | Published technical material limit | Method or standard designation |
|---|---|---|
| Active ingredient content | ≥ 950 g/kg | HPLC or GC with external standard |
| Water content | ≤ 2 g/kg | Karl Fischer titration; USP <921> Method Ia |
| Acidity as H2SO4 | ≤ 2 g/kg | Acid-base titration |
| Residual solvents | Route-specific dossier limit | USP <467> / Ph. Eur. 5.4 |
The table reflects published technical material criteria. A veterinary API certificate of analysis generally adds identity by infrared or chromatographic retention time, related substances by HPLC area percent, and, for parenteral use, controls on bacterial endotoxins and sterility of the finished dosage form rather than the bulk API. Because dimpylate is a liquid, particle-size tests apply to the carrier-loaded premix or granulate rather than to the neat active ingredient.
The primary difference is the control framework. Agricultural technical material may be manufactured under crop-protection quality standards and released with a specification oriented to field performance. Veterinary API is expected to be produced under current good manufacturing practice for active pharmaceutical ingredients, with documented batch records, change control, and stability data. The molecular structure may be identical, but supplier qualification for solid oral and parenteral veterinary products requires control of solvent residues, heavy metal catalyst residues, moisture, acidity, and potentially genotoxic impurities. Agricultural technical material may contain solvents or stabilizers that are not acceptable in parenteral or feed premix applications. Published comparative toxicological data for all veterinary dosage forms is limited; justification is therefore product-specific.
Another difference from other ectoparasiticide APIs is dimpylate’s organophosphate mechanism. Unlike pyrethroid or neonicotinoid actives that primarily modulate sodium channels or nicotinic acetylcholine receptors, dimpylate requires bioactivation to diazoxon and acts through acetylcholinesterase phosphorylation. In accidental overdosage, specific antidotal intervention with atropine and pralidoxime is used. Compared with other organophosphates such as coumaphos or trichlorfon, dimpylate has relatively low water solubility and moderate lipophilicity, which affects solvent selection and residue behavior in hair, wool, or skin. These distinctions influence formulation choices rather than requiring simple concentration adjustments.
In solid-dose processing, the liquid physical state of dimpylate means that direct compression is not feasible without a solid carrier. The API is adsorbed onto microcrystalline cellulose, colloidal silicon dioxide, or a combination of the two; the carrier ratio is selected from the oil absorption capacity of the carrier and must produce a free-flowing, non-sticky premix. The blend is then diluted in low-shear tumble or double-cone equipment. For low-dose tablets and capsules, blend uniformity is verified according to USP <905>; manufacturing-scale batches may fail when stratified sampling detects API enrichment in fine fractions or depletion in coarse fractions. Use of a carrier with a particle-size distribution overlapping the excipient phase reduces segregation risk.
Wet granulation with an aqueous binder is generally avoided unless the process is specifically designed to control hydrolysis. Non-aqueous granulation with isopropanol- or ethanol-based binder systems may be used, but residual solvent levels must meet USP <467>. Drying temperature and airflow are critical because oxidative desulfuration of the phosphorothioate can occur at elevated temperature. Fluid-bed drying with product temperature held below the onset temperature identified by differential scanning calorimetry is used when non-aqueous granulation is required. Published stability data for dimpylate in specific granulated matrices is limited; therefore, each formulation must be supported by degradation product screening under accelerated conditions.
Capsule filling follows the same carrier-loaded blend approach. Hard gelatin capsules expose the fill to atmospheric humidity; therefore, the API-loaded granules should be filled under controlled relative humidity, commonly below 40% RH, to prevent capsule shell softening and API hydrolysis at the capsule interface. Tablet compression may be performed on a rotary tablet press with precompression; tooling must be resistant to residual acidic residues from the API. Low-dose tablets require careful control of punch lubrication and scrap rates to avoid content uniformity drift.
Injectable dimpylate products require a non-aqueous vehicle because the API is poorly water soluble and hydrolytically labile. Finished injectable solutions must comply with USP <1> for injections, USP <71> for sterility, and USP <85> for bacterial endotoxins. If the marketing authorization allows terminal sterilization, moist heat is not automatically suitable because organophosphorothioates can degrade in the presence of water at high temperature. Aseptic filtration through a 0.22 µm membrane into sterile containers is used when terminal sterilization is not validated. Vehicle selection is usually limited to fixed oils, glycol ethers, or another non-aqueous solvent acceptable for veterinary parenteral administration. Published data for specific dimpylate parenteral formulations is limited; vehicle compatibility must be confirmed through forced degradation studies.
Solution dosage forms may be non-aqueous liquids or emulsifiable concentrates intended for dilution before topical administration. Solutions should be buffered in a mildly acidic range because alkaline conditions accelerate hydrolytic cleavage. Contact with primary amine compounds, strong oxidizing agents, and certain metal surfaces such as copper and mild steel should be avoided unless compatibility is demonstrated. Glass-lined or 316L stainless steel vessels are typical for compounding; material selection is confirmed by corrosion and trace metal testing. Mixing should use a high-shear disperser only when required, because excessive shear can generate heat and localize oxidative stress.
| Dosage form | Typical processing route | Critical control point | Equipment type |
|---|---|---|---|
| Tablets | Carrier adsorption, non-aqueous granulation, compression | Content uniformity per USP <905>; drying temperature | Rotary tablet press with precompression |
| Capsules | Carrier-loaded powder blend, encapsulation | Relative humidity below capsule shell tolerance | Dosator or tamping-pin encapsulation machine |
| Powders / granules / premix | Geometric dilution with feed or pharmaceutical carriers | Segregation control and carrier particle-size match | Double-cone blender, ribbon mixer |
| Injections | Non-aqueous vehicle, aseptic filtration | Sterility USP <71>; endotoxin USP <85> | Sterile filling line with isolator |
| Solutions | Dissolution in non-aqueous solvent or emulsifiable system | pH and moisture control | Glass-lined or 316L stainless steel mixing vessel |
Premix and granule products intended for in-feed use require separate controls. The carrier must be compatible with animal feed matrices and must allow homogeneous distribution of the active at the intended inclusion rate. Geometric dilution is performed in stages, beginning with an adsorption step onto silica, corncob, or precipitated silica followed by dry blending. The finished premix is tested for active content and homogeneity using multiple thief samples from different locations. If the premix is intended for food-producing species, relevant maximum residue limits and withdrawal periods must be observed according to national authorization; published maximum residue limit data for dimpylate are jurisdiction-specific.
Stability of bulk dimpylate is influenced by moisture, heat, and light. The API should be stored in tightly closed containers under inert gas at controlled room temperature. Hydrolytic degradation is pH-dependent; aqueous systems above neutral pH show faster loss of parent compound. Because the API is a liquid with limited water solubility, addition of surfactants or co-solvents can change degradation kinetics. Forced degradation studies according to ICH Q1A(R2) are used to identify degradation products in each dosage form. Published data on individual degradation products in veterinary formulations is limited; therefore, specificity of the HPLC method must be confirmed for the proprietary matrix.
The distinctions from other API products become most apparent on multi-use solid dosage lines. Dimpylate’s liquid nature, thermal sensitivity, and organophosphate toxicity require segregated containment and cleaning validation. Changeover from dimpylate to non-organophosphate products on shared equipment requires documented cleaning procedures, swab limits, and a validated analytical method for residue detection. Cross-contamination into other veterinary products is a critical concern; dedicated production equipment or campaign scheduling is generally required.
