| HS Code | 316963 |
| Product Name | Sodium Hydrogen Sulphite Veterinary Grade API |
| Chemical Name | Sodium hydrogen sulfite |
| Molecular Formula | NaHSO3 |
| Molecular Weight | 104.06 g/mol |
| Cas Number | 7631-90-5 |
| Appearance | White or almost white crystalline powder or crystals with a faint sulphur dioxide odour |
| Solubility | Freely soluble in water; sparingly soluble in ethanol |
| Ph Value | Aqueous solution is acidic; pH of a 5% solution is approximately 3.0 to 4.5 |
| Assay | 95.0% to 100.5% calculated on the dried basis as NaHSO3 |
| Sulphur Dioxide Content | Equivalent to approximately 24% to 26% of available SO2 |
| Storage Conditions | Store in a tightly closed container in a cool, dry place; protect from light and moisture |
| Function | Acts as an antioxidant and preservative in pharmaceutical formulations |
| Veterinary Grade Application | Suitable for use in tablets, capsules, powders, granules, premixes, solutions, and injectable veterinary dosage forms |
As an accredited Sodium Hydrogen Sulphite 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 Hydrogen Sulphite Veterinary Grade API is packed in 25 kg net weight, food-grade polythene-lined drums with airtight, moisture-resistant seals. |
| Container Loading (20′ FCL) | 20′ FCL container loading of Sodium Hydrogen Sulphite veterinary API: palletized, moisture-protected drums/bags, secured safely for tablet/injection/capsule/powder forms. |
| Shipping | Sodium Hydrogen Sulphite Veterinary Grade API is shipped in sealed, humidity-proof containers, protected from heat and light. Compatible packaging and inert liners prevent contamination. Transport in dry, ventilated conditions, segregated from acids, oxidizers, and foodstuffs. Ensure proper labeling, documentation, and handling protocols for veterinary-grade pharmaceutical use. |
| Storage | Store in tightly sealed, original containers in a cool, dry, well-ventilated area. Protect from moisture, humidity, heat, and direct sunlight. Avoid contact with acids and oxidizing agents. Ensure container integrity to prevent decomposition and sulphur dioxide release. Keep away from incompatible substances and food products. |
| Shelf Life | Shelf Life: 24 months when stored in tightly closed containers in a cool, dry place, protected from light and moisture. |
Sodium hydrogen sulphite (NaHSO₃, E222) is incorporated into veterinary dosage forms as a reducing agent and oxygen scavenger. Its utility is confined to aqueous systems where free sulfite species remain in equilibrium and where formulation pH, trace-metal concentration, headspace oxygen, and packaging permeability can be controlled. The application set below covers parenteral solutions, oral solutions and drenches, tablets, capsules, water-soluble powders, granules, medicated premixes, and lyophilised powders.
| Dosage form / application | Typical addition range | Primary compliance anchor | Terminal product type |
|---|---|---|---|
| Injectable solution/emulsion | 0.05–0.20% w/v | Ph. Eur. 5.1.1; VICH GL18; ICH Q3D | 50–250 mL multi-dose vials |
| Oral solution/drench | 0.10–0.30% w/v | Ph. Eur. 5.1.4; VICH GL18; ICH Q3D | 100 mL–1 L oral drench bottles |
| Tablet/capsule core | 0.10–0.50% w/w | Ph. Eur. 5.1.4; VICH GL11; ICH Q3D | Film-coated tablets; hard gelatin capsules |
| Water-soluble powder/granule | 0.10–0.75% w/w | Ph. Eur. 5.1.4; VICH GL18; ICH Q3D | 100 g–5 kg sachets or barrier-lined buckets |
| Medicated premix | 0.05–0.25% w/w | Regulation (EU) 2019/4; VICH GL18; ICH Q3D | 1–25 kg medicated premix bags |
| Lyophilised powder for injection | 0.02–0.10% w/v | Ph. Eur. 5.1.1; 21 CFR 211; VICH GL18; ICH Q3D | 1–10 mL lyophilised vials |
Parenteral formulations of oxygen-sensitive veterinary actives use sodium hydrogen sulphite at 0.05–0.20% w/v in the finished aqueous solution, with pH adjusted to 3.5–5.0 where the bisulfite ion is the dominant free sulfite species. The material is dissolved in Water for Injections at 15–25°C in a stainless-steel prep vessel before addition of the API; dissolved oxygen is lowered to <0.5 mg/L by nitrogen sparging and monitored with an optical dissolved-oxygen probe. The bulk solution is passed through a 0.22 µm PVDF or PES cartridge filter and filled into Type I borosilicate glass vials under nitrogen blanketing. If the formulation permits moist-heat sterilisation, terminal sterilisation is performed in a steam-air autoclave at 121°C for 15 min; heat-labile APIs are processed by aseptic filtration and filling in an isolator line. Compliance anchors include Ph. Eur. 5.1.1 methods of preparation of sterile products, VICH GL18 for residual solvents, ICH Q3D elemental impurities, and the relevant sodium bisulfite compendial monograph for SO₂ assay and clarity of solution. The material is not introduced into solutions containing thiamine HCl, because bisulfite cleaves the thiazole-methylene bridge; it is also kept separate from strong oxidising disinfectants and heavy-metal catalyst residues. Terminal products include 50 mL, 100 mL, and 250 mL multi-dose vials of injectable antiparasitic or local anaesthetic solutions for cattle and swine, where oxidative discoloration and potency loss are the primary failure modes.
The limiting variable in oral solutions is not antioxidant capacity but organoleptic tolerance and free SO₂ evolution at low pH. Loading is therefore confined to 0.10–0.30% w/v in finished oral solutions and drenches at pH 3.0–4.5. The production sequence involves dissolving sodium hydrogen sulphite in purified water at 20–30°C in an AISI 316L mixing tank, adding a citrate or tartrate buffer after the sulfite has fully dissolved, and only then dispersing the API to avoid localised low-pH degradation of acid-sensitive actives. Headspace oxygen is displaced by nitrogen, and the batch is filtered through a 0.45 µm stainless-steel cartridge before filling into amber PET bottles or glass bottles with tamper-evident closures. Compliance for non-sterile liquid preparations is aligned with Ph. Eur. 5.1.4 microbiological quality, VICH GL18 residual solvents, ICH Q3D elemental impurities, and the sulfite monograph limits for heavy metals and iron. Terminal products are 100 mL, 500 mL, and 1 L oral drench solutions for ruminants, typically containing oxidisable endectocide or anticoccidial actives, where the bisulfite functions as both an antioxidant and a protecting agent against oxidative colour development. The operational boundary is that sodium hydrogen sulphite addition to high-pH solutions above 7.0 shifts the equilibrium toward sulfite and reduces the available free SO₂ fraction; pH therefore precedes addition in the batch record.
In tablet and capsule manufacture, sodium hydrogen sulphite is introduced through the granulating fluid rather than as a dry powder, because wet granulation provides a more uniform antioxidant coating over the API particles. The addition ratio is 0.10–0.50% w/w of the finished core weight, and the binder solution is commonly 5–10% w/w povidone K30 in purified water. Granulation is performed in a high-shear granulator with an impeller speed of 200–350 rpm and chopper speed of 1,500 rpm; wet mass is dried in a fluid-bed dryer at inlet air temperature 50–60°C until loss on drying reaches 1.5–2.5% w/w. Dried granules are sized through an 800 µm screen, lubricated with 0.5–1.0% w/w magnesium stearate, and compressed on a rotary tablet press at 8–15 kN for tablets; capsule fills are prepared by filling the same granules into size 0–4 hard gelatin capsules. Compliance for non-sterile solid oral forms is established under Ph. Eur. 5.1.4, VICH GL11, ICH Q3D, and the sodium bisulfite monograph; finished-product stability protocols follow VICH GL11 for impurity and degradation-product reporting. The main incompatibility is with amine-based film coatings and amine-containing APIs, where free bisulfite can form sulfonate adducts; such combinations require prior forced-degradation comparison. Terminal products include film-coated tablets and hard gelatin capsules for companion animal and swine endoparasite or metabolic disease programmes, manufactured in batch sizes of 10–120 kg.
For poultry and swine drinking-water medication, water-soluble powders and granules contain sodium hydrogen sulphite at 0.10–0.75% w/w of the dry mix, with the lower bound used when the formulation also contains soluble trace minerals and the upper bound reserved for highly oxidisable APIs. The process uses a low-shear ploughshare mixer or a twin-ribbon blender; sodium hydrogen sulphite is pre-milled through a 60 mesh screen and pre-blended with 10–20% w/w of the carrier lactose or dextrose before addition to the main batch. Mixing is run for 10–20 min at 60–100 rpm, and where granulation is required to reduce segregation, the blend is compacted on a roller compactor with a nip angle of 20–30° and a roll pressure of 40–70 kN. The resulting granules are filled into laminated foil sachets or barrier-lined buckets under nitrogen-flushed packaging. Compliance is aligned with Ph. Eur. 5.1.4, VICH GL18, ICH Q3D, and the relevant purity monograph for sulfate, chloride, and iron limits. The critical process boundary is chlorinated drinking water: free chlorine above 1–2 ppm is consumed by sulfite before the API is stabilised, reducing disinfectant residual and producing sulfate; the product is therefore not administered through hyperchlorinated lines without prior dechlorination confirmation. Terminal products are 100 g, 1 kg, and 5 kg water-soluble powders or granules used in large-group drinking-water medication of poultry and swine.
A different sequence constraint arises when sodium hydrogen sulphite is required in medicated premixes: the sulfite is first dispersed onto the inert carrier before the API is added, because direct contact between the acidic sulfite particle and an acid-labile antibiotic produces localised low-pH zones that can increase degradation. The addition ratio is 0.05–0.25% w/w of the finished premix, and the carrier is typically calcium carbonate, wheat middlings, or lactose monohydrate with moisture not more than 8% w/w. Mixing is carried out in a Forberg-type paddle mixer or twin-shaft ribbon blender for 15–25 min, followed by screening through a 500 µm sieve to break soft agglomerates. The premix is packed in 1 kg, 5 kg, or 25 kg valve bags with an oxygen barrier layer, and stability testing follows VICH GL18 for residual solvents, ICH Q3D for elemental impurities, and Regulation (EU) 2019/4 where the premix is incorporated into medicated feed at 0.5–5.0% w/w of final feed. The process boundary is alkaline mineral premixes: free sulfite is less stable above pH 7.5, and the combination can generate SO₂ vapour and cake within the mixer; such formulations must be segregated and pH-controlled. Terminal products are medicated premix and intermediate feed products for group treatment of pigs and poultry, where oxidative losses of the therapeutic agent during storage and feed pelleting are the main control variables.
In lyophilised parenteral powders, residual water content rather than sulfite loading frequently controls the finished-cake stability of sodium hydrogen sulphite. The bulk solution is prepared with the sulfite at 0.02–0.10% w/v in Water for Injections at pH 3.5–5.0, sterile-filtered through a 0.22 µm PVDF cartridge, and filled into Type I glass vials under nitrogen. Lyophilisation is performed with shelf ramping from -40°C to +30°C at a chamber pressure of 0.15–0.30 mbar; residual moisture is controlled below 1.0% w/w because free water accelerates sulfite oxidation and reduces the available SO₂ fraction in the dried matrix. Compliance anchors include Ph. Eur. 5.1.1 for sterile preparation, 21 CFR 211 for finished pharmaceutical cGMP, VICH GL18 residual solvents, ICH Q3D elemental impurities, and the sulfite monograph for assay and clarity. The critical incompatibility is with unbuffered high-sugar lyophilisation matrices, where the low pH required for bisulfite ion may alter the crystalline/amorphous ratio and depress the collapse temperature; published data for this specific configuration is limited, and thermal characterisation by freeze-drying microscopy is required before scale-up. Terminal products are 1 mL, 5 mL, and 10 mL vials of lyophilised powder for solution for injection, reconstituted immediately before administration to cattle, horses, or companion animals.
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Sodium hydrogen sulphite veterinary grade API, model NaHSO₃-VET-API, CAS 7631-90-5, is a reducing agent and antioxidant supplied as a white to off-white crystalline powder or granular solid. The material is intended for use in tablets, capsules, powders, granules, premixes, solutions, and injectable aqueous preparations. Because solid sodium hydrogen sulphite exists in equilibrium with sodium metabisulfite, the batch release assay is expressed as sulfur dioxide content rather than as absolute sodium hydrogen sulphite. Three physical variants are available: NaHSO₃-VET-API for general oral and premix processing, NaHSO₃-VET-API-SI for injectable applications with endotoxin control, and NaHSO₃-VET-API-M with nominal particle size ≤200 µm for direct compression and dry granulation. The API is produced under cGMP conditions consistent with FDA 21 CFR 210/211 and is not interchangeable with technical-grade sodium bisulfite intended for water treatment or photographic chemistry, because veterinary API grades carry lower trace metal, sulfate, chloride, and microbial burden specifications.
Release is performed against a representative specification aligned with sulfite antioxidant monographs and adapted for veterinary dosage manufacturing. The assay is determined by iodometric titration and reported as SO₂. Because the solid material contains both bisulfite and metabisulfite species, the SO₂ assay range is intentionally wider than a single-species theoretical value. Trace element levels are controlled by ICP-OES, and injectable-grade material is evaluated for bacterial endotoxin using a kinetic turbidimetric LAL method. The following representative acceptance criteria apply to the standard non-sterile grade; the sterile injectable grade additionally requires endotoxin and particulate matter testing according to current pharmacopoeial methods:
| Parameter | Acceptance criterion | Method designation |
|---|---|---|
| Appearance | White to off-white crystalline powder | Visual inspection |
| Assay as SO₂ | 58.0–67.4% | Iodometric titration |
| pH, 1% w/v aqueous solution | 3.8–5.0 | Potentiometric pH |
| Heavy metals as Pb | ≤10 ppm | Ph.Eur current edition |
| Iron | ≤20 ppm | ICP-OES |
| Chloride | ≤0.05% | Limit test |
| Sulfate | ≤0.05% | Limit test |
| Arsenic | ≤3 ppm | AAS hydride generation |
| Lead | ≤2 ppm | ICP-OES |
| Loss on drying | ≤5.0% | Halogen moisture balance |
| Bacterial endotoxins, NaHSO₃-VET-API-SI | ≤0.25 EU/mg | LAL kinetic turbidimetric |
| Microbial enumeration, non-sterile grade | TAMC ≤100 CFU/g, TYMC ≤10 CFU/g | Membrane filtration |
Sampling of finished containers is conducted according to ISO 2859-1 general inspection level II with an AQL of 0.65 for critical chemical attributes. Bulk shipments are double-lined with low-density polyethylene and sealed under nitrogen at ≤20% RH. Storage above 40 °C or exposure to direct sunlight accelerates sulfur dioxide evolution and should be avoided.
For solid oral dosage forms, the non-sterile API is milled to a target mean particle size of 180–200 µm before blending. Powder flow measurements on a 316L stainless steel production line show tapped bulk density of 0.85–1.10 g/cm³ and Hausner ratio of 1.15–1.35. These values permit reliable metering from twin-screw feeders into high-shear granulators at screw speeds up to 120 rpm without bridging. At relative humidity above 60%, however, the material becomes adhesive on contact surfaces and should be handled with conditioned compressed air at ≤20% RH. Ribbon blender mixing of the API with microcrystalline cellulose and sodium starch glycolate produces acceptable content uniformity after 10–12 minutes at 25 rpm; longer mixing times increase electrostatic adhesion and should be avoided. The API is added intragranularly when wet granulation is required, but the granulating fluid should be kept below 30 °C because acidic binders can provoke premature sulfur dioxide release.
In injectable aqueous systems, sodium hydrogen sulphite functions primarily as an oxygen scavenger and antioxidant for oxidation-sensitive active substances. The reaction consumes dissolved oxygen according to 2 HSO₃⁻ + O₂ → 2 SO₄²⁻ + 2 H⁺. The resulting pH shift must be controlled with a suitable buffer system, typically citrate or phosphate, when the formulation pH is maintained between 3.5 and 5.0. Addition levels in veterinary parenterals are commonly limited to 0.05–0.3% w/v; higher levels provide no additional oxygen-scavenging capacity in closed containers and may increase the risk of sulfite-associated reactions in sensitive species. Published data for species-specific sulfite tolerance in veterinary parenteral use is limited, so the lowest effective antioxidant concentration should be selected using dissolved oxygen measurements in the finished container rather than by fixed dosage convention.
The injectable grade is dissolved in Water for Injections in a 316L stainless steel vessel with a nitrogen overlay pressure of 0.2–0.5 bar. Dissolved oxygen is reduced to ≤0.5 mg/L before the active ingredient is added, then the solution is filtered through a 0.22 µm polyvinylidene fluoride or polyethersulfone membrane. Terminal sterilisation at 121 °C for 15 minutes can cause headspace sulfur dioxide loss; therefore the fill volume and headspace oxygen content must be controlled to maintain antioxidant reserve. Stability studies on a pilot lyophilisation line indicate that sodium hydrogen sulphite is most effective when the solution is filled under nitrogen and the rubber stopper has low oxygen permeation. The API should not be combined with aldehydic drug substances, amine-based buffers, or copper ions, because these components consume bisulfite through nucleophilic addition or redox side reactions. If the formulation pH rises above 6.5, bisulfite converts to sulfite and the oxygen-scavenging rate changes; the pH specification should therefore be reviewed before transferring a formulation from one buffer system to another.
In tablet and capsule manufacture, sodium hydrogen sulphite is used as a solid-state antioxidant for active substances that undergo oxidative degradation during granulation, drying, or long-term storage. The API is blended at 0.05–0.5% w/w relative to the total core weight, depending on the oxidation potential of the active substance. For moisture-sensitive actives, direct compression is preferred over wet granulation. When wet granulation is unavoidable, fluid-bed drying is performed with inlet air not exceeding 55 °C and final granule moisture is held below 1.5% to reduce sulfur dioxide evolution and tablet softening. Compression on a rotary tablet press is typically operated at 10–20 kN for flat-faced beveled tablets, though the optimum force depends on the excipient matrix. Sodium hydrogen sulphite should not be dry-blended with strongly acidic excipients such as ascorbic acid in an unbuffered formulation, because moisture pickup can initiate sulfite decomposition and generate localised sulfur dioxide gas. Capsule formulations using the micronized grade show acceptable blend uniformity after 8 minutes in a bin blender at 20 rpm when the API is pre-screened through a 500 µm mesh.
Veterinary premixes and granules containing fat-soluble vitamins, unsaturated fatty acids, or mineral catalysts often require a reducing agent to limit oxidative rancidity and loss of vitamin activity. Sodium hydrogen sulphite veterinary grade API is incorporated into premix carriers at 0.05–0.5% w/w on a dry matter basis. The premix-grade product is granulated to 180–425 µm to reduce dust and improve distribution in feed. Mixing studies in a horizontal ribbon blender with a capacity of 500 kg show a coefficient of variation below 5% after 10 minutes at 25 rpm. Premixes containing the API should be packaged in moisture-resistant sacks and stored below 25 °C, because high storage temperature combined with trace transition metals accelerates sulfite oxidation to sulfate. In drinking water applications, the API can also be used for chlorine removal before reconstitution of probiotics or live vaccines; the stoichiometric requirement depends on free chlorine residual and water pH. For routine dechlorination of municipal water with chlorine residual below 2 mg/L, an addition of 2–5 mg/L of sodium hydrogen sulphite is typically effective, but the actual dose should be confirmed by measuring free chlorine after 5 minutes of mixing. The material should not be mixed with oxidising disinfectants in the same stock solution, because exothermic redox reaction and sulfur dioxide release may occur.
Oral solutions and reconstitutable powders present a different stability problem: the antioxidant must remain active in aqueous media with dissolved oxygen, light exposure, and metal extractables from packaging. Sodium hydrogen sulphite is used in oral vehicles at 0.05–0.2% w/v, with the solution pH adjusted to 3.5–4.5 to maintain bisulfite as the dominant species. Amber polyethylene terephthalate or Type III glass containers reduce light-induced oxidation, while a nitrogen headspace during filling limits oxygen ingress. Long-term storage data show that sulfate accumulation is the principal degradation product; if sulfate exceeds 0.1% w/v, the solution may show visible precipitation with calcium-containing buffers. Therefore, deionized water with calcium below 1 mg/L is specified for manufacturing oral solutions containing this API. Reconstitutable powders are dry-blended with the API at the same use rates as tablets, then filled into low-moisture foil pouches. The powder should be reconstituted only at the time of administration, because the antioxidant reserve declines rapidly once the product is hydrated and exposed to air.
Sodium hydrogen sulphite differs from sodium metabisulfite, sodium sulfite, and technical-grade sulfite sources in pH, sulfur dioxide assay, ionic species distribution, and suitability for veterinary dosage forms. Sodium metabisulfite releases SO₂ rapidly in water and has a higher SO₂ assay, which makes it a common solid antioxidant, but its acidic response in solution can be too aggressive for some poorly buffered veterinary formulations. Sodium sulfite is more alkaline and is suitable for neutral to alkaline systems, but it has a lower oxygen-scavenging rate in acidic formulations. Technical-grade sodium bisulfite may meet water treatment requirements but generally lacks the trace metal, arsenic, chloride, sulfate, and microbial controls required for veterinary API use. The following comparison summarises the main distinctions for formulation selection:
| Product | Major species in 1% aqueous solution | Typical pH, 1% solution | SO₂ assay | Primary veterinary dosage use |
|---|---|---|---|---|
| Sodium hydrogen sulphite veterinary API | HSO₃⁻ with equilibrium SO₂ | 3.8–5.0 | 58.0–67.4% | Injectable antioxidant, oral powder antioxidant |
| Sodium metabisulfite | S₂O₅²⁻ converting to HSO₃⁻ | 3.5–4.5 | 65.0–70.0% | Solid oral dosage antioxidant |
| Sodium sulfite | SO₃²⁻ | 9.0–10.5 | 50.0–52.0% | Alkaline aqueous antioxidants |
| Technical sodium bisulfite | HSO₃⁻ plus sulfite oxidation products | 3.5–5.0 | 24.0–30.0% as solution | Water treatment only |
Sodium hydrogen sulphite veterinary grade API offers intermediate acidity and a solid-state SO₂ release profile that can be adjusted through particle size control. The sodium metabisulfite content in the solid may vary between batches, but the SO₂ assay specification ensures consistent reducing capacity. Sodium sulfite is not substituted without reformulation because its higher pH shifts acid-base equilibria and can alter drug solubility. Technical-grade material should not be used in veterinary pharmaceutical manufacture because it can contain arsenic, lead, iron, sulfate, and insoluble residues above pharmacopoeial limits. The veterinary API is therefore selected when a controlled reducing agent is required across tablets, capsules, powders, granules, premixes, solutions, and injectable preparations without the variability associated with industrial sulfite sources.
