Fomepizole USP IP
CAS: 7554-65-6
Molecular Formula: C₄H₆N₂
Fomepizole, also known as 4-methylpyrazole, is a medication used to treat methanol and ethylene glycol poisoning. It may be used alone or together with hemodialysis. It is given by injection into a vein. Fomepizole works by blocking the enzyme that converts methanol and ethylene glycol to their toxic breakdown products. Fomepizole was approved for medical use in the United States in 1997. It is on the World Health Organization's List of Essential Medicines. Fomepizole is used to treat ethylene glycol and methanol poisoning. It acts to inhibit the conversion of these alcohols into their respective aldehydes by alcohol dehydrogenase. The prevents further conversion to the more active toxic metabolites oxalic acid and formic acid, respectively. Fomepizole is most effective when given soon after ingestion of ethylene glycol or methanol. Delaying its administration allows for the generation of harmful metabolites.
Molecular Structure
| Description | Colorless to pale yellow liquid, it may be present as solid form at room temperature (25°C) |
| Solubility | Soluble in water, very soluble in ethanol, diethyl ether and in chloroform |
| Identification by IR | Infrared spectrum of sample should concordant with the spectrum obtained with standard |
| Identification by HPLC | The retention time of major peak of sample solution, corresponds to that of standard solution obtained in the test for assay |
| Water Content by KF, Wt.% | NMT 1.0% |
| Color and clarity of solution | Abs at 400nm, NMT 0.030AU |
| Transmittance at 600nm | NLT 95.0% |
| Residue on Ignition | NMT 0.05% (Sample size 1g) |
| Hydrazine content, by GC Wt.% | NMT 0.001% |
| Related Substances by GC | Impurity at RRT 0.78: NMT 0.1% |
| Related Substances by GC | Unspecified impurity: NMT 0.2% |
| Related Substances by GC | Total Impurity: NMT 0.5% |
| Assay on anhydrous basis | 98 to 102% |
| Residual Solvent | Methylene Dichloride: NMT 600ppm |
| Residual Solvent | Methanol: NMT 3000ppm |
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