| HS Code | 775293 |
| Api Name | Sulphapyridine |
| Grade | Pharma Grade API |
| Chemical Name | 4-Amino-N-pyridin-2-ylbenzenesulfonamide |
| Molecular Formula | C11H11N3O2S |
| Molecular Weight | 249.29 g/mol |
| Cas Number | 144-83-2 |
| Appearance | White or almost white crystalline powder |
| Solubility | Slightly soluble in water; soluble in acetone and ethanol; sparingly soluble in ether |
| Melting Point | 191-193°C |
| Assay | 98.0% - 101.0% on dried basis |
| Related Substances | Complies with pharmacopoeial limits |
| Suitable Dosage Forms | Tablet, capsule, granule, injection |
| Route Of Administration | Oral and injectable |
As an accredited Sulphapyridine Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 kg net in sealed double polythene-lined drums, labelled for pharma-grade Sulphapyridine API used in oral and injectable formulations. |
| Container Loading (20′ FCL) | 20′ FCL loading of Sulphapyridine Pharma Grade API: drummed, palletized, secured, with moisture-proof liners for safe transport. |
| Shipping | Ship as pharma-grade API in sealed double polyethylene liners inside HDPE drums or fiberboard containers, protected from moisture, light, and contamination. Ensure tamper-evident seals, complete labeling, and include COA and MSDS. Store cool and dry; for injectable grades, maintain validated aseptic handling and temperature-controlled transport. |
| Storage | Store Sulphapyridine Pharma Grade API in tightly sealed, light-resistant containers in a cool, dry, well-ventilated area at controlled room temperature (15–30°C). Protect from moisture, direct sunlight, and excessive heat. Keep away from strong oxidizing agents and incompatible substances. Maintain proper labeling, segregation, and inventory rotation to preserve purity, stability, and compliance for oral and injectable formulations. |
| Shelf Life | Store in cool, dry place, protected from light. Shelf life: 36 months from manufacture date when packaging remains intact. |
In wet granulation-based tablet lines, sulphapyridine is processed as a micronized active pharmaceutical ingredient with controlled sieve fraction because the free acid exhibits poor aqueous solubility and coarse particles above 150 µm can extend disintegration beyond compendial limits. Manufacturing operations fall under 21 CFR 211.111 time limits, 21 CFR 211.165 release testing, and ICH Q3D elemental impurity risk assessment. Tablet formulations for a 500 mg label claim may allocate micronized sulphapyridine at 40–70% w/w, microcrystalline cellulose q.s., povidone K30 at 2–4% w/w, crospovidone at 2–5% w/w, and magnesium stearate at 0.5–1.0% w/w; lower strengths reduce the API mass fraction to 25–50% w/w but require equivalent diluent adjustment to maintain die fill. The downstream process begins with high-shear granulation at impeller tip speed 5–6 m/s and chopper speed 1500–3000 rpm, wet massing for 3–6 min, and fluid-bed drying at inlet air 60–70°C to a loss on drying of 1.5–2.5%. Dried granules are milled through a 1.0 mm screen, blended in a bin blender at 10–12 rpm for 20 min, and compressed on a rotary tablet press with pre-compression rollers to limit capping at high drug load. Terminal products include uncoated or film-coated immediate-release tablets for oral administration, packaged in HDPE containers with desiccant or PVC/PVDC/aluminium blisters. Release testing for uniformity and dissolution follows USP <905> and USP <711>.
High-speed dosator capsule fillers apply a compression stroke to a powder bed, and fill-weight variability is governed by powder cohesion, bulk density, and the ratio of dosator length to diameter. Sulphapyridine powder with moisture above 3.0% can adhere to dosator pin surfaces, producing weight drift beyond ±3% and capsule shell splitting during filling. The formulation therefore uses a hydrophobic flow aid and a low-humidity manufacturing environment; a typical capsule formulation may contain sulphapyridine at 50–85% w/w, pregelatinized starch at 15–40% w/w, colloidal silicon dioxide at 0.5–1.5% w/w, and sodium stearyl fumarate at 0.5–1.0% w/w, screened through a 0.5 mm sieve before blending. The downstream process uses a V-blender at 25 rpm for 15 min, an intermittent-motion capsule filler operating at 60,000 capsules/h, and in-process checkweighing every 5 min; fill weight is correlated with dosator powder bed height and tamping force. Compliance tests include USP <905> for content uniformity, USP <2040> for disintegration, and 21 CFR 211.166 stability testing. Terminal finished products are hard gelatin or HPMC capsules of size 0 or 1, commonly packed in PVC/PVDC blisters with desiccant under RH ≤ 40%.
| Dosage form | Test attribute | Standard designation | In-process control linkage |
|---|---|---|---|
| Immediate-release tablet | Dosage unit uniformity | USP <905>, Ph. Eur. 2.9.40 | Press weight control at ±3% |
| Immediate-release tablet | Dissolution | USP <711>, Ph. Eur. 2.9.3 | Granule hardness and loss on drying monitored |
| Hard capsule | Disintegration | USP <2040>, Ph. Eur. 2.9.1 | Fill weight check every 5 min |
| Granules for suspension | Particle-size distribution | USP <786>, Ph. Eur. 2.9.38 | Sieve fraction after milling |
| Sterile injectable | Visible and subvisible particulate matter | USP <790>, USP <788> | Filtration integrity and fill volume |
Because sulphapyridine granules intended for oral suspension are filled into sachets or bottles, the granule bed must retain both dry flow and rapid redispersion after reconstitution. The manufacturing formula may allocate sulphapyridine at 20–45% w/w within a sucrose or mannitol diluent system, with xanthan gum at 0.2–0.5% w/w as a suspending agent, citric acid monohydrate at 0.1–0.3% w/w for pH adjustment, and povidone K30 at 1–3% w/w as a binder. Granulation is performed as a top-spray fluid-bed process with inlet air at 50–70°C, spray rate 100–200 g/min, and bed temperature 28–32°C; dried granules are milled to a sieve fraction between 150 µm and 1.18 mm. The particle-size distribution is verified against USP <786> or Ph. Eur. 2.9.38, and redispersibility is assessed by repeated inversion after 24 h; quantitative suspension stability criteria are defined in the product’s marketing authorization. Terminal finished products include foil-lined single-dose sachets and amber glass bottles with a graduated measuring cup for oral use. Compliance for release and stability testing is governed by 21 CFR 211.165 and 21 CFR 211.166, with non-sterile microbial limits tested under USP <61> and USP <62>.
Preparation of a sterile injectable from sulphapyridine base requires conversion to the sodium salt in Water for Injection using a 1:1 molar ratio of sulphapyridine to sodium hydroxide, followed by pH adjustment to 9.0–10.0; the free acid can precipitate below neutral pH and block sterilizing filters. Published data for a specific commercial sulphapyridine injectable strength is limited; therefore the following is based on standard sulfonamide sodium salt parenteral manufacturing practice. A lyophilized formulation may use mannitol as a bulking agent at 4–6% w/v and may be filled at a sulphapyridine equivalent concentration that is determined by the product’s marketing authorization; the solution is pre-filtered through 0.45 µm and sterile-filtered through 0.22 µm polyvinylidene fluoride membranes under nitrogen pressure. Aseptic filling occurs in Grade A conditions within a Grade B background, and the vials are lyophilized with shelf freezing at -40°C for 3 h, primary drying at -20°C, and secondary drying at 25°C. Compliance standards include USP <1>, USP <788> for subvisible particulate matter, USP <790> for visible particulates, USP <85> for bacterial endotoxins, USP <71> for sterility, and 21 CFR 211.167 sterility testing. Terminal finished products include sterile lyophilized cake in Type I borosilicate glass vials sealed with bromobutyl elastomeric stoppers and aluminium caps, intended for parenteral use after reconstitution with an appropriate diluent.
High-dose sulphapyridine tablet cores containing 60–80% w/w API exhibit increased friability at the tablet edge, and aqueous film coating introduces a moisture exposure that can soften a poorly bound core if bed humidity rises above 45% RH. Coating is performed in a side-vented pan coater with pan speed 3–6 rpm, inlet air 60–70°C, bed temperature 38–42°C, spray rate 15–25 g/min per gun, and atomizing air pressure 1.5–2.0 bar. The coating suspension contains hydroxypropyl methylcellulose at 6–8% w/w, polyethylene glycol 400 at 0.5–1.0% w/w, talc at 1–2% w/w, and purified water q.s., applied to a weight gain of 2.5–3.5%. The coated tablet is tested for dissolution according to USP <711> and disintegration according to USP <2040>; packaging system suitability is assessed under USP <661.1> and USP <671> when plastic containers are used. Because sulfonamides can undergo photo-oxidative discoloration, ICH Q1B photostability data determine whether amber glass or aluminium blister packaging is required. Terminal finished products include film-coated tablets packed in amber HDPE bottles with desiccant or PVC/PVDC/aluminium blisters; the film coat does not alter the drug-release mechanism but reduces dusting and edge chipping during high-speed packaging.
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Pharmaceutical-grade sulphapyridine, 4-amino-N-(pyridin-2-yl)benzenesulfonamide, is supplied as a crystalline active pharmaceutical ingredient for oral solid dosage forms and injectable presentations. The compound is identified by CAS Registry Number 144-83-2, molecular formula C11H11N3O2S, and relative molecular mass 249.29 g mol⁻¹. The free acid is reported as a white to pale yellow crystalline solid with a melting range of approximately 190–193 °C; the unionized form is practically insoluble in water at neutral pH and dissolves in dilute mineral acids and alkali hydroxides. Supplier-specific model designations distinguish oral powder grades from low-endotoxin injectable grades. Typically, oral grades are controlled for particle size, bulk density, residual solvent profile, and microbial limits, whereas injectable grades are controlled for bacterial endotoxin, bioburden, particulate matter, and sterile-filterability. Injectable material may be supplied as the free acid for in situ sodium salt formation or as a pre-formed sodium salt. No universal model code exists across manufacturers, so the procurement specification should define the physical form, D10/D50/D90, endotoxin limit, residual solvent class, and container closure before qualification. The API is used as a starting material for oral tablets, hard gelatin capsules, granules, oral liquids, and sterile injectable preparations.
| Parameter | Reference method | Typical release criterion |
|---|---|---|
| Appearance | Ph. Eur. 2.2.1 | White to faint yellow crystalline powder |
| Identification | IR: Ph. Eur. 2.2.24; UV: Ph. Eur. 2.2.25 | Conforms to reference spectrum |
| Assay, dried basis | HPLC: Ph. Eur. 2.2.29 | 98.0–101.0% C11H11N3O2S |
| Related substances | HPLC: Ph. Eur. 2.2.29 | Unspecified ≤ 0.10%; total ≤ 0.5% or per monograph |
| Loss on drying | Ph. Eur. 2.2.32 | ≤ 0.5% at 105 °C, 2 h |
| Sulfated ash | Ph. Eur. 2.4.14 | ≤ 0.1% |
| Particle size distribution | Laser diffraction: ISO 13320:2020 | D50 10–30 µm; D90 ≤ 75 µm for oral grade |
| Endotoxin, injectable grade | Ph. Eur. 2.6.14, USP <85> | Calculated from maximum daily dose; low-endotoxin grade often ≤ 0.050 EU/mg dose-dependent |
Analytical release of each batch is performed by HPLC under Ph. Eur. 2.2.29; identification relies on infrared absorption under Ph. Eur. 2.2.24 and ultraviolet spectrophotometry under Ph. Eur. 2.2.25. Related substances are reported according to ICH Q3A thresholds: reporting at 0.05%, identification at 0.10%, and qualification at 0.15% for daily doses up to 2 g, unless a pharmacopoeial monograph imposes stricter values. Residual solvents are determined by headspace gas chromatography under Ph. Eur. 2.4.24. The API must be manufactured under ICH Q7 for active pharmaceutical ingredients; a change in final recrystallisation solvent or drying temperature can alter residual solvent profile, crystal habit, and electrostatic charging. The vendor technical package should include at least three consecutive production batches with certificates of analysis, particle size distribution, and stability data. For injectable grade, bacterial endotoxin release data generated by Ph. Eur. 2.6.14 and bioburden data by Ph. Eur. 2.6.12 should accompany each lot.
In oral solid dosage manufacture, sulphapyridine is incorporated in dry blends, wet granulations, capsules, and granules. The crystalline free acid can exhibit electrostatic charging in low-humidity suites; therefore, particle size distribution is measured by laser diffraction according to ISO 13320:2020, with D10, D50, and D90 recorded together with bulk and tapped density under Ph. Eur. 2.9.34. Direct compression recipes generally request a D50 of 10–30 µm and a D90 ≤ 75 µm to reduce segregation and content uniformity failures on rotary tablet presses operating above 40 rpm. Low-dose blends of 5–15% w/w are pre-screened through a 500 µm stainless-steel sieve and geometrically diluted in a bin blender or V-blender before lubrication. For wet granulation, the aqueous binder may be alkaline or hydroalcoholic because the free acid has low aqueous solubility. Granulation in a high-shear mixer with impeller tip speed of 5–10 m s⁻¹ is followed by fluid-bed drying at inlet air temperature not exceeding 60 °C to limit discolouration of the aromatic amine. Dried granules are milled through a 1.0 mm screen, lubricated with magnesium stearate at 0.5–1.5% w/w, and compressed to hardness of 50–100 N with friability ≤ 1.0% by Ph. Eur. 2.9.7. Dissolution testing under Ph. Eur. 2.9.3 or USP <711> uses pH 1.2 or 6.8 media, with surfactant added only when justified by the dosage form.
For capsule filling, automatic tamping and dosator machines respond to the same flow properties. Blends with Carr index above 25% or Hausner ratio above 1.25 are not suitable for direct encapsulation and should be granulated or densified. Roller compaction at 2–4 kN cm⁻¹ followed by milling to D50 150–300 µm can restore flow without promoting segregation; if roller compaction is not available, slugging with a tablet press and subsequent sizing through a 1.0 mm screen is an alternative. Granulation also reduces dust formation, which is relevant because fine sulphapyridine particles can become airborne and contribute to cross-contamination in shared facilities. Cleaning validation for sulfonamide residues should use HPLC detection with limits based on permitted daily exposure values, because visual inspection alone will not detect low-level carryover.
Because the free acid is practically insoluble at physiological pH, injectable presentations are formulated as the sodium salt or are pH-adjusted in situ with sodium hydroxide above pH 8.5. The resulting solution must be monitored for colour and related substances because the aromatic amine is susceptible to oxidative degradation. Terminal sterilisation at 121 °C for 15 min may be used only after HPLC data demonstrate that the specified impurity profile remains within limits. Aseptic filtration through a 0.22 µm PES or PVDF membrane is required for heat-sensitive formulations; pre-filtration bioburden is controlled to ≤ 10 CFU/100 mL in accordance with EU GMP Annex 1. Injectable-grade sulphapyridine API must meet bacterial endotoxin limits derived from the maximum daily dose using Ph. Eur. 2.6.14 or USP <85>; low-endotoxin release limits of ≤ 0.050 EU/mg are common for small-volume parenterals, but the final limit must be calculated for each product because endotoxin intake depends on dose and patient body weight. Particulate matter is controlled by Ph. Eur. 2.9.19 or USP <788>; for containers up to 100 mL, the solution should contain no more than 25 particles per mL at ≥ 10 µm and no more than 3 particles per mL at ≥ 25 µm. If free acid is supplied for in situ salt formation, sterile-filterability must be confirmed at the final pH because local acidification can precipitate unionized sulphapyridine. Published solubility values for the sodium salt in complex parenteral vehicles remain limited; pilot-scale solubility screening is required before transfer to a production line.
Drug product compatibility studies for injectable sulphapyridine should include pH shift, light exposure, and contact with rubber closures, because an alkaline solution can leach stopper accelerators and generate particulate haze. If the sodium salt is lyophilised, the freeze-dried cake should be reconstituted with water for injection to a concentration that does not exceed the solubility limit at the final pH. Published data for lyophilised sulphapyridine sodium formulations in this specific presentation remain limited; pilot-scale solubility and cake-collapse screening is required before committing to a production freeze-dryer. The choice of container closure—Type I glass vial with elastomeric closure or a prefilled syringe—requires extractables and leachables assessment under USP <1663>.
Four sulfonamide-related substances are occasionally confused in sourcing documents, but their chemical and formulation properties are not interchangeable. Sulphapyridine contains a pyridin-2-yl substituent on the sulfonamide nitrogen; sulfadiazine contains a pyrimidin-2-yl substituent, which changes solubility, crystal habit, and urinary pH behaviour. Sulfamethoxazole carries a 5-methylisoxazol-3-yl group and is most often processed in a 5:1 fixed-dose combination with trimethoprim; sulphapyridine is not a typical partner for dihydrofolate reductase inhibitors. Sulfasalazine is a prodrug, not a simple sulfonamide: sulphapyridine is covalently linked through an azo bond to 5-aminosalicylic acid, and colonic bacterial azoreductases cleave the azo bond to release sulphapyridine and 5-ASA. The released sulphapyridine is absorbed and acetylated, while 5-ASA acts locally. This difference explains why sulfasalazine and sulphapyridine cannot be substituted on a mass basis. For formulation, the free acid of sulphapyridine is a distinct crystalline entity with low aqueous solubility, whereas sulfasalazine has its own solid-state properties and disintegrant interactions. Procurement of sulphapyridine for tablets, capsules, granules, or injections therefore requires confirmation of identity against the reference standard, because the infrared spectrum and HPLC retention time are not equivalent to those of sulfasalazine or sulfamethoxazole.
Analytically, the four substances are separated by reversed-phase HPLC with UV detection. The retention time for sulphapyridine is influenced by the pyridine ring pKa but is not a substitute for a reference standard. Suppliers should provide a certificate of analysis that includes loss on drying, residue on ignition, melting range, and IR spectrum; this package distinguishes sulphapyridine from sulfamethoxazole and sulfadiazine during incoming inspection. Compendial identification tests are substance-specific and should not be interchanged across sulfonamide monographs.
Sulphapyridine free acid is normally packed in double polyethylene bags within a fibre drum; injectable-grade material is additionally supplied with nitrogen overlay, sterile or low-bioburden bagging, and light-resistant outer packaging. The retest period is assigned from ICH Q1A(R2) stability data generated at long-term 25 °C/60% RH and accelerated 40 °C/75% RH. Residual solvents are controlled under ICH Q3C; class 3 solvents are typically limited to 5000 ppm, and any class 1 solvent is avoided in the final purification train. Elemental impurities are assessed by a risk-based approach under ICH Q3D and released by ICP-MS using Ph. Eur. 2.4.20 or USP <233>. The free amine is sensitive to light and strong oxidising agents; warehouse excursions above 40 °C should be avoided unless justified by accelerated stability data. When the API is supplied for injectable use, container closure integrity and sterility assurance must be maintained through the entire supply chain because terminal sterilisation of the finished product may not be possible for every formulation.
Stability of the unformulated API is not the same as the finished product. Retest period assignment can be extended only with long-term data at 25 °C/60% RH and, if significant change occurs at 40 °C/75% RH, an intermediate condition of 30 °C/65% RH. The API should not be stored with strong oxidising agents or near sources of nitrogen oxides because aromatic amine degradation can proceed through nitrosation. For injectable presentation, storage of the raw API under inert gas reduces oxidative discolouration and stabilises the aromatic amine during warehousing.
