| HS Code | 774877 |
| Product Name | Sodium Phenytoin (Dalantin) Veterinary Grade API for Tablets / Injections / Capsules / Powders / Granules / Premix / Solutions |
| Chemical Name | 5,5-Diphenylhydantoin sodium salt |
| Molecular Formula | C15H11N2NaO2 |
| Molecular Weight | 274.25 g/mol |
| Cas Number | 630-93-3 |
| Grade | Veterinary Grade API |
| Appearance | White or almost white crystalline hygroscopic powder |
| Solubility | Freely soluble in water; sparingly soluble in ethanol; practically insoluble in chloroform and ether |
| Melting Point Decomposition | Approximately 290°C (decomposes) |
| Ph | 10.0 - 12.0 (1% aqueous solution) |
| Loss On Drying | NMT 2.5% w/w |
| Assay | 98.0% - 102.0% on dried basis |
| Heavy Metals | NMT 20 ppm |
| Residue On Ignition | 16.0% - 17.5% w/w |
| Storage | Store in tightly closed containers, protected from light, in a dry place |
As an accredited Sodium Phenytoin (Dalantin) 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 | Sodium Phenytoin (Dalantin) veterinary grade API, white crystalline powder, supplied in sealed 25 kg drums with double polybags. |
| Container Loading (20′ FCL) | Container loading (20′ FCL) for Sodium Phenytoin veterinary API: palletized drums, moisture-protected, securely stowed, segregated from incompatible materials, ensuring stability and safety. |
| Shipping | Sodium Phenytoin (Dalantin) Veterinary Grade API ships in sealed, opaque, moisture-proof containers under controlled room temperature, protected from light. Ship via expedited, traceable courier with temperature monitoring. Hazard documentation and certificates accompany shipment. Ensure compliance with local veterinary drug transport regulations. |
| Storage | Store Sodium Phenytoin (Dalantin) Veterinary Grade API in a tightly closed, well-sealed container, protected from light and moisture. Keep in a cool, dry, well-ventilated area at controlled room temperature (15–30°C). Avoid excessive heat and incompatible materials. For formulated tablets, injections, capsules, or powders, maintain packaging integrity until use. |
| Shelf Life | Shelf life: 3 years from manufacture when stored sealed in a cool, dry place, protected from light and moisture. |
A wet-granulated tablet intermediate for canine neurology is metered to deliver 100 mg phenytoin acid equivalent per unit; the sodium salt is charged at 1.09 times the acid mass to correct for molecular weight. The core granulation is formulated with 28–40% w/w sodium phenytoin, 30–45% w/w lactose monohydrate, 15–25% w/w microcrystalline cellulose, and 3–5% w/w povidone K30. Wet-massing is performed in a high-shear mixer with a 300 L bowl; binder solution is sprayed at 2–4 kg/min until impeller power draw rises 15–22% above dry-mix baseline. Over-wetting above 3.0% w/w residual moisture increases die-wall adhesion and produces a fine-particle fraction that shifts tablet weight variability outside the USP <905> acceptance range. Drying in a fluid-bed drier at 55–65°C inlet air temperature reduces moisture to 1.8–2.5% w/w; the dried granules are milled through a 0.8 mm screen and compressed on a rotary press with 8 mm round concave tooling. Tablet hardness is maintained at 6–10 kp with friability below 1.0% by weight under USP <1216>. The finished tablet is the terminal dosage form for canine anticonvulsant therapy, with batch release testing including USP <905> uniformity of dosage units and USP <711> dissolution testing in 900 mL aqueous medium at 37±0.5°C using Apparatus 2 at 50 rpm. Compliance is governed by 21 CFR 211.110(a) for in-process sampling and 21 CFR Part 530 for extralabel use in companion animals; API manufacturing follows ICH Q7, and residual solvent controls follow compendial monograph requirements for sodium phenytoin.
The injectable solution is formulated at 50 mg/mL sodium phenytoin (5.0% w/v) in a hydroalcoholic vehicle containing 40% v/v propylene glycol and 10% v/v ethanol, adjusted to pH 12 with 2 N sodium hydroxide. The pH is not a cosmetic parameter; it is the operational boundary that prevents reconversion of the sodium salt to insoluble phenytoin acid, which has a pKa near 8.3 and begins precipitating when the solution is diluted below the critical pH threshold. Aseptic processing in a closed stainless-steel vessel under nitrogen is used because the co-solvent system and strongly alkaline pH impose constraints on terminal steam sterilization. The bulk solution is filtered through a 0.22 µm membrane qualified for hydroalcoholic streams, then filled into Type I glass vials under an inert gas overlay; headspace oxygen is monitored below 1.0% v/v. Production lines use USP <71> sterility testing, USP <788> particulate matter testing, and USP <790> visible particulate inspection as release controls. The terminal product type is a sterile injectable vial. The principal incompatibility observed at production scale is precipitation when the injection is mixed with dextrose-containing diluents, because the reduced pH shifts the equilibrium toward free phenytoin and produces crystal growth. Only 0.9% w/v sodium chloride injection is used as a diluent; refrigeration is avoided because low temperature reduces solubility and may generate precipitates even in the marketed vial. Compliance with 21 CFR 211.94(b) governs container-closure suitability, while USP <1> defines the injectable quality attributes.
At a veterinary compounding pharmacy, sodium phenytoin is dispersed or dissolved at 30 mg/mL (3.0% w/v). The vehicle is structured with 1.5–2.0% w/v microcrystalline cellulose/carboxymethylcellulose sodium and 20% w/v sorbitol; glycerin at 10% v/v is used as a levigating agent. Final pH is maintained above the precipitation threshold of the free acid; viscosity is controlled to 300–600 mPa·s because lower viscosity accelerates sedimentation and higher viscosity impairs pourability. Compounding uses a high-shear rotor-stator mixer at 1,500–3,000 rpm for dispersion, followed by gentle deaeration to reduce entrapped air that would cause dose errors in oral syringes. The in-process test is sedimentation volume after 24 hours, which must remain at or above 0.95. USP <795> governs nonsterile compounding beyond-use dating and environmental controls, while USP <51> preservative effectiveness testing applies to multi-dose oral containers. The terminal finished product is an oral suspension in amber multi-dose bottles, dispensed with graduated syringes. The operational boundary includes pre-wetting of suspending agents to avoid fish-eye agglomerates and a prohibition on direct dry blending of API into the finished vehicle because non-uniform wetting has produced assay variability in high-humidity compounding suites.
| Dosage form | Reference standard | In-process control | Terminal product type |
|---|---|---|---|
| Wet-granulated tablet | USP <905>, USP <711>, USP <1216>, 21 CFR 211.110(a) | Granulate moisture 1.8–2.5% w/w; hardness 6–10 kp | Canine anticonvulsant tablet |
| Sterile injectable | USP <1>, USP <71>, USP <788>, 21 CFR 211.94(b) | pH 12; headspace oxygen <1.0% v/v | Hydroalcoholic injection vial |
| Compounded oral suspension | USP <795>, USP <51> | Viscosity 300–600 mPa·s; sedimentation volume ≥0.95 | Multi-dose oral suspension |
| Low-dose capsule/powder | USP <795>, USP <905>, 21 CFR 211.165 | Fill weight ±5%; active content 1.5–6.0% w/w | Capsule or unit-dose sachet |
| Granulated oral powder intermediate | USP <795>, ICH Q7, 21 CFR 211.130 | Bulk density 0.45–0.58 g/cm³; moisture <2.5% w/w | Unit-dose granules or stick packs |
Feline dosing requires an active content range of 1.5–6.0% w/w when sodium phenytoin is filled into hard gelatin capsules, because individual doses may be 5–25 mg and total fill weights are held to 125–250 mg. Direct blending is not acceptable for this low loading. The API is first triturated with an equal mass of anhydrous lactose, then dilution is expanded stepwise until the final active content is achieved; this sequence is executed in a low-shear tumble blender with filling volume between 50% and 70% of rated capacity. Capsules are filled on an intermittent-motion capsule filler with in-process weight variation checks at ±5% of target mass. Published data for feline-specific capsule dilution is limited; batch records therefore treat each fill weight as an individual compounding event under USP <795>. Uniformity of dosage unit testing follows USP <905>, and release testing is aligned with 21 CFR 211.165. The terminal finished product type is a hard gelatin capsule or a unit-dose powder sachet. At relative humidity above 60%, the API absorbs surface moisture and adheres to stainless-steel contact surfaces; pre-conditioning at 30–35% RH for at least 4 hours is required before filling.
Granulated sodium phenytoin intermediate for unit-dose oral powders is produced by wet-massing active at 20–35% w/w with 5–8% w/w pregelatinized starch and 0.5–1.0% w/w magnesium stearate, followed by extrusion through a 1.0 mm screen and fluid-bed drying to less than 2.5% w/w moisture. The resulting granules are dispensed into single-dose stick packs or unit-dose cups for use in dogs that cannot safely swallow tablets. This is not a feed-premix operation; the narrow therapeutic index of phenytoin excludes dilute incorporation into bulk feed because cross-contamination and uneven consumption would create overdose risk. Regulatory compliance for the pharmacy-scale granulation step falls under USP <795> for nonsterile compounding; when the granulate is used as an intermediate in a registered manufacturing facility, ICH Q7 and 21 CFR 211.130 govern packaging and labeling controls. Terminal finished product types are bulk granules or unit-dose powder packets; fill-weight verification is performed to ±5% of target mass, and granule flow through the filling machine requires bulk density between 0.45 and 0.58 g/cm³ to avoid sticking and rat-holing.
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Sodium phenytoin (Dalantin) Veterinary Grade API is the sodium salt of 5,5-diphenylhydantoin, CAS 630-93-3, molecular formula C15H11N2NaO2, molecular weight 274.25 g/mol, and phenytoin acid equivalent factor 0.920. The Dalantin identifier denotes a veterinary-grade sodium phenytoin API supplied in standard powder, micronized, and injection-compatible particle-size distributions for tablets, injections, capsules, powders, granules, premixes, and oral solutions. Because no separate USP veterinary monograph is assigned to phenytoin sodium, the material is qualified against the current USP Phenytoin Sodium monograph with supplementary endotoxin, elemental impurity, and residual solvent controls appropriate to the intended animal drug route of administration.
Release testing follows the current USP Phenytoin Sodium monograph. The specification includes identification by infrared absorption and sodium flame test, assay by HPLC, related substances, loss on drying, residual solvents, and elemental impurities. For injection-grade lots, bacterial endotoxins and subvisible particulate matter are specified after dissolution in the intended vehicle. The exact particle size distribution is agreed between purchaser and manufacturer because no universal veterinary monograph establishes a fixed D90.
| Parameter | Representative specification | Test method |
|---|---|---|
| Appearance | White to off-white crystalline powder | Visual |
| Identification A | Infrared absorption matching reference | USP <197> |
| Identification B | Sodium flame test | USP <191> |
| Assay (dried basis) | 98.0% to 101.0% C15H11N2NaO2 | HPLC |
| Loss on drying | Not more than 2.0% | USP <731> |
| Related substances | Individual unspecified impurity not more than 0.10%; total impurities not more than 1.0% | HPLC |
| Residual solvents | Meet ICH Q3C limits | USP <467> |
| Elemental impurities | Meet ICH Q3D or USP <232>/<233> | ICP-MS |
| Particle size | D90 not more than 100 µm for oral solid; finer grades as specified | Laser diffraction per ISO 13320:2020 |
| Bacterial endotoxins | Injection-grade lots meet USP <85> limit based on maximum dose | Limulus amebocyte lysate |
Assay is expressed on the dried basis; therefore loss on drying must be determined concurrently for each lot. The sodium content can be verified by flame photometry for release. For injection-grade lots, particulate matter in the compounded solution is controlled by USP <788> after filtration through 0.2 µm membranes. Residual solvent profiles are lot-specific and are reviewed against route-specific limits in ICH Q3C. Because the sodium salt is alkaline, aqueous dissolution testing may require an alkaline medium to maintain sink conditions.
The selection of sodium phenytoin rather than phenytoin acid changes wetting, dissolution, and active-moiety equivalence. The sodium salt exhibits higher aqueous solubility, enabling solution-based granulation and improved dissolution in solid oral dosage forms. However, the salt is alkaline and can accelerate hydrolysis of ester-based coatings or interact with acid-labile excipients in the granulating fluid. When substituting the sodium salt for the free acid, the salt factor must be applied: 108.7 mg sodium phenytoin yields 100 mg phenytoin acid. Failure to apply the conversion produces an 8% underdose of active moiety.
| Property | Sodium phenytoin | Phenytoin acid |
|---|---|---|
| Molecular weight | 274.25 g/mol | 252.26 g/mol |
| Phenytoin acid equivalent | 92 mg per 100 mg | 100 mg per 100 mg |
| Water solubility | Soluble in water; slightly soluble in alcohol | Practically insoluble in water; soluble in dilute alkali |
| pH of aqueous dispersion | Alkaline above pH 11 when dissolved | Weakly acidic suspension |
| Primary formulation use | Tablets, capsules, injections, oral solutions | Tablets, capsules, compounding powders |
| Moisture handling | Requires controlled humidity; pre-drying at RH over 60% | Lower moisture sorption in typical processing |
| Dissolution behavior | Rapid dissolution in alkaline media | Dissolution requires ionization or wetting agents |
Veterinary-grade qualification differs from human-grade phenytoin sodium in the acceptance of animal-specific impurity thresholds, feed-premix homogeneity data, and carryover residue documentation where the API is used in medicated feed. A human-grade certificate alone does not demonstrate suitability for veterinary premix use because blend homogeneity and stability in feed matrices require separate validation. Conversely, an injectable veterinary product shares the same pH, particulate, and sterility controls as human parenterals under USP <788> and USP <85>.
Injection-grade sodium phenytoin requires an alkaline aqueous-organic vehicle. Phenytoin is a weak acid with pKa 8.3; the sodium salt dissolves as the phenytoinate anion above pH 11. When the solution is diluted with infusion media of lower pH, the equilibrium shifts toward the poorly water-soluble free acid, and visible precipitation can occur. Commercial injection formulations have employed propylene glycol/ethanol/water vehicles adjusted with sodium hydroxide. Processing controls include pH measurement after compounding, filtration through low-protein-binding membranes, and subvisible particulate testing under USP <788>. Avoid dilution into acidic vehicles; where dilution is necessary, compatibility with the specific infusion fluid must be verified by pH and particulate monitoring at the point of administration.
For injection manufacture, the incoming API is not necessarily sterile; the finished injection is sterilized by filtration through 0.2 µm filters after dissolution in the vehicle. Bacterial endotoxin control is assigned on the basis of maximum intended animal dose using USP <85>. If the final injection contains propylene glycol, the API manufacturer must control reducing substances and aldehyde contamination because these can degrade the active molecule.
Oral solutions are prepared by dissolving the sodium salt in alkaline buffer systems with cosolvents such as propylene glycol or glycerin. The pH is maintained above 11 to prevent precipitation of the free acid. Acidic sweetening or flavoring agents must be neutralized before addition or avoided entirely. The solution is protected from light and filled under nitrogen to reduce oxidative discoloration.
For tablet and capsule manufacture, the sodium salt is dry blended or wet granulated. Aqueous wet granulation is feasible because the salt dissolves in the granulating fluid, but the resulting granules can become hard on drying and may require sizing through 0.8 mm or 1.0 mm screens. Direct compression has been used on rotary tablet presses with precompression force profiling when the API fraction is low and the particle size D90 is below 100 µm. Content uniformity is evaluated according to USP <905>; dissolution is evaluated according to USP <711> using an alkaline medium that maintains sink conditions. Published data for specialized veterinary tablet strengths in multi-species use is limited; therefore, formulation studies should establish blend uniformity, dissolution, and stability in the final container closure system.
Powders, granules, and premixes intended for in-feed or oral administration are prepared with lactose, starch, or microcrystalline cellulose carriers. The API is added by geometric dilution or low-shear tumble blending. The sodium salt tends to segregate when its particle size differs from the carrier by more than one order of magnitude; therefore, particle sizing is controlled before blending. Blend uniformity is assessed by stratified sampling and HPLC. For premixes, the inclusion rate is calculated on the phenytoin acid equivalent basis to avoid overage or underdose when converting from the free acid. Residual moisture in feed matrices is monitored because free water can mobilize the alkaline sodium salt and create localized pH gradients that degrade heat-labile feed additives.
Aqueous solubility of sodium phenytoin is high under strongly alkaline conditions, but it falls sharply as pH declines toward pKa 8.3. Particle size distribution therefore controls dissolution in solid oral dosage forms only where the salt does not rapidly dissolve; for modified-release products, diffusion through the hydrated layer may be rate-limiting rather than dissolution of the pure salt. Particle size specification depends on dosage form. Tablets and capsules typically require a D90 below 100 µm; direct compression may use a D90 below 50 µm. Laser diffraction method validation follows ISO 13320:2020. Powder flow is characterized by bulk and tapped density according to USP <616>; poor flow may require forced feeders on high-speed tablet presses.
Manufacture of veterinary-grade sodium phenytoin API is conducted in closed stainless-steel or glass-lined reactors. The final crystallized salt is filtered, washed with controlled solvent, and dried under vacuum. Milling is performed under nitrogen or low-humidity air because micronized material can develop electrostatic charge. Metal contamination from milling is controlled by USP <232>/<233> or ICH Q3D analysis on the finished micronized grade. Batch-to-batch variance in particle size is controlled by fixed crystallization cooling rates and drying profiles. During scale-up from pilot to production crystallizers, changes in agitation speed and cooling rate can alter crystal aspect ratio, which affects flow through vibratory feeders and tablet weight variation. Particle size distribution is therefore measured on every batch using laser diffraction and compared with the approved specification.
In veterinary neurology, sodium phenytoin is used as an anticonvulsant; its elimination is dose-dependent and saturable, which differs from first-order elimination observed with some other anticonvulsants. Published veterinary pharmacokinetic data are limited for this specific configuration; therapeutic monitoring protocols from human use should not be transferred without species-specific validation. Compared with phenobarbital or potassium bromide, sodium phenytoin requires different monitoring because of saturable metabolism and the potential for disproportionate changes in exposure after small dose adjustments. Veterinary formulations therefore require tighter assay and content uniformity limits than some older anticonvulsant APIs.
Storage of sodium phenytoin API should be in tightly closed, light-resistant containers. At relative humidity above 60%, pre-drying is required before weighing and blending. The sodium salt should not be combined with strong acids, acidic buffers, or acid-releasing excipients during wet granulation or solution compounding. For injection compounding, the final solution must be protected from light and used within the validated in-use holding period; precipitation or particulate formation requires immediate rejection.
