Nitric Oxide (NO), also known as nitrogen monoxide, is a colorless gaseous chemical compound and an important pharmaceutical and medical gas. It acts as a signaling molecule in the human body and produces physiological effects including vascular smooth-muscle relaxation and vasodilation.
Nitric Oxide is used in pharmaceutical and medical applications, particularly where controlled inhalation of nitric oxide is required. It is supplied as a compressed gas and requires specialized manufacturing, filling, storage and quality-control procedures.
Nitric Oxide is a specialized medical/pharmaceutical gas requiring stringent control of gas purity and trace impurities. Unlike conventional solid APIs, its quality is primarily evaluated through gas-phase assay, identification and impurity analysis.
Pharmacopoeial and medical-gas quality assessment can include control of nitrogen dioxide, nitrogen, oxygen, carbon dioxide, nitrous oxide, water and other relevant gaseous impurities.
CAS Number: 10102-43-9
Molecular Formula: NO
Molecular Weight: 30.0061 g/mol
IUPAC Name: Nitric Oxide
Systematic Name: Nitrogen Monoxide
Synonyms: Nitrogen monoxide, Nitrogen(II) oxide, NO
Drug Class: Medical Gas
Therapeutic Class: Pulmonary Vasodilator
Therapeutic Area: Respiratory / Cardiovascular
Molecule Type: Inorganic Small Molecule / Medical Gas
UN Number: UN 1660
NIST confirms the CAS number, formula and molecular weight of Nitric Oxide.
Inhaled Nitric Oxide diffuses into vascular smooth muscle and activates the soluble guanylate cyclase (sGC)–cyclic GMP pathway, resulting in smooth-muscle relaxation and pulmonary vasodilation.
Its physiological effects include:
Nitric Oxide is relevant to:
Inhaled Nitric Oxide is used as a selective pulmonary vasodilator. It can reduce pulmonary vascular resistance while producing comparatively less systemic vasodilation because its biological activity is rapidly terminated when Nitric Oxide reacts with hemoglobin.
The specific therapeutic indication, concentration and administration conditions depend on the approved medicinal-gas product and applicable regulatory labeling.
Nitric Oxide is a colorless gas at room temperature. NIST reports a molecular weight of 30.0061 g/mol.
The gas has a boiling point of approximately −151.7°C and a melting/freezing point of approximately −163.6°C, according to NIST/Sigma-Aldrich data.
Nitric Oxide has limited solubility in water. Reported data indicate approximately 0.0056 g/100 mL at 20°C, equivalent to approximately 0.056 g/L.
For pharmaceutical and medical-gas applications, Nitric Oxide requires careful control of impurities because it can oxidize to nitrogen dioxide (NO₂).
Important quality attributes include:
USP describes medical-gas testing as involving assay of the gas and analysis of trace impurities, with techniques including gas chromatography and paramagnetic analysis.
A controlled pharmaceutical Nitric Oxide production and filling process may involve:
Typical pharmaceutical Nitric Oxide testing may include:
A European Pharmacopoeia-based specification historically reported not less than 99.0% V/V Nitric Oxide, with specific impurity controls including CO₂, N₂, NO₂, N₂O and H₂O.
Nitric Oxide should be stored as a compressed gas in suitable, properly secured gas cylinders, under controlled conditions and in accordance with applicable medical-gas and compressed-gas safety requirements.
The gas should be protected from incompatible materials and handled using appropriate gas-cylinder equipment.
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Melting Point | −163.6°C |