Phenazopyridine Hydrochloride
CAS: 136-40-3
Category: Pharmaceutical Intermediates
| Purity | Reagent Grade ≥95%, Standard Grade ≥98%, High-Purity Grade ≥99%, Pharmaceutical Grade ≥98.0–102.0% ( |
| Molecular Formula | C11H12ClN5 |
| Molecular Weight | 249.70 |
| Appearance | Brick-red to purple crystalline powder or microcrystals |
| Packaging | 100 mg/glass vial, 250 mg/glass vial, 500 mg/glass vial, 1 g/glass vial, 5 g/glass vial, 25 g/amber glass bottle, 100 g/amber glass bottle, or 1 kg/aluminum foil bag |
| Testing Indicators | Appearance — Visual inspection (brick-red to purple crystalline powder or microcrystals with slight violet luster); Melting point — Capillary method (233–238°C, IARC; 235°C, NTP; 139°C, free base); Boiling point — Not applicable (decomposes before boiling); Density — Hydrometer (not typically measured); Purity — HPLC-UV (≥95–99.5%, C18 column, acetonitrile:buffer gradient, λ=220–260 nm, azo chromophore); Related substances — HPLC (impurity profiling including aniline, 2,6-diaminopyridine, des-phenylazo analogs, and reductive cleavage products); Assay — Titrimetric or HPLC (USP: 98.0–102.0% of C11H12ClN5, calculated on the dried basis; Thermo Fisher: 99.0–101.0%); Loss on drying — Gravimetric (≤0.5%); Residue on ignition — Gravimetric (≤0.1%); Heavy metals — Colorimetric/ICP-MS (≤20 ppm); Identification — FTIR (characteristic peaks: N–H (amine) ~3300–3500 cm⁻¹, aromatic C–H ~3000–3100 cm⁻¹, N=N (azo) ~1400–1500 cm⁻¹, aromatic C=C ~1600 cm⁻¹, C–N ~1300–1350 cm⁻¹, C–Cl ~800–900 cm⁻¹, N–H bend ~1600 cm⁻¹); UV spectrophotometry (λmax ~238 nm in ethanol, IARC; λmax ~220–260 nm, azo chromophore); ¹H NMR (DMSO-d₆: δ 6.80–7.80 ppm multiplet aromatic protons, δ 8.50 ppm broad singlet NH₂ (2,6-diamino), δ 10.50 ppm broad singlet NH₂ (pyridinium)); ¹³C NMR (DMSO-d₆: δ 115–150 ppm aromatic carbons, δ 155 ppm C–NH₂); Mass spectrometry — ESI-MS (m/z 250 [M+H]⁺, m/z 213 [M–HCl]⁺ for free base); Water content — Karl Fischer titration (GB/T 6283/EP 2.5.12); pH — Potentiometry (aqueous suspension, weakly acidic, pKa ~2.3); Specific optical rotation — Not applicable (achiral compound); Solubility — Slightly soluble in cold water (1:300), soluble in boiling water (1:20), slightly soluble in ethanol, soluble in glacial acetic acid/glycerol/ethylene glycol/propylene glycol, insoluble in acetone/benzene/chloroform/ether/toluene. |
| Storage Notes | Store in a cool, dry, well-ventilated area at 20–25°C (68–77°F); excursions permitted to 15–30°C (59–86°F) [USP Controlled Room Temperature]. Protect from light, moisture, and air. Keep container tightly sealed in amber vials or light-protective packaging. Store powder at -20°C for long-term stability (up to 3 years); at 4°C for 2 years. Light-sensitive material; avoid prolonged exposure to light and UV radiation. The compound should be stored in amber containers or light-protective wrapping. Store away from strong oxidizing agents and incompatible substances. Use inert atmosphere (nitrogen or argon) for long-term storage if available. |
| Lead Time | 10 days |
Phenazopyridine Hydrochloride (INN, also known as Pyridium, Urodine, Mallophene, Sedural, Azodyne, or NC 150) is a heterocyclic aromatic azo compound and a local urinary tract analgesic. It functions as a topical analgesic on the mucosa of the urinary tract, providing symptomatic relief of pain, burning, urgency, frequency, and discomfort associated with lower urinary tract irritation. It does not possess antibacterial activity and is typically used as an adjunct to antimicrobial therapy for urinary tract infections (UTIs). Upon ingestion, it imparts a characteristic orange or red color to the urine due to its azo dye structure. Used as a pharmaceutical intermediate and active pharmaceutical ingredient (API) for the development and quality control of oral tablet formulations (e.g., Pyridium 100 mg, Pyridium 200 mg). Approved for short-term clinical use in the management of urinary tract irritation. Also employed in analytical method development, pharmacological research, and quality control applications. ATC code: G04BX06. Note: Classified by IARC as Group 2B (possibly carcinogenic to humans) and by NTP as reasonably anticipated to be a human carcinogen based on animal studies.