Fomepizole API is a pyrazole derivative chemically known as 4-methylpyrazole. It is an inhibitor of alcohol dehydrogenase and is used as an antidote in methanol and ethylene glycol poisoning. Fomepizole has the molecular formula C₄H₆N₂, molecular weight 82.10 g/mol, and CAS Number 7554-65-6.
Fomepizole is a low-melting compound that can occur as a liquid or crystalline solid at room temperature. Its melting point is approximately 25°C. It is soluble in water and very soluble in ethanol, diethyl ether and chloroform.
Fomepizole is also known as 4-methyl-1H-pyrazole and 4-methylpyrazole. Its molecular formula is C₄H₆N₂, molecular weight 82.1038 g/mol, and CAS Registry Number 7554-65-6.
Commercial pharmaceutical-grade material is available with a reported purity of 99%, while analytical-grade 4-methylpyrazole is also commercially available at 96% minimum by GC.
Fomepizole API can be evaluated using identification, chromatographic assay, water/loss-on-drying determination, impurity testing and elemental impurity controls. For your CMS, the values below are based on a published pharmaceutical-grade specification where available.
Fomepizole is used as an alcohol dehydrogenase inhibitor and as an antidote for confirmed or suspected methanol or ethylene glycol poisoning.
| Parameter | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Heavy Metals | NMT 10 ppm |
| pH (1% Solution) | 5.0 – 7.0 |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |
| Melting Point | 25–30°C |
| Solubility | Soluble in water and alcohol |