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| Other names | analgesine, antipyrine |
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| Eliminationhalf-life | 12 hours |
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| ECHA InfoCard | 100.000.442 |
| Chemical and physical data | |
| Formula | C11H12N2O |
| Molar mass | 188.230 g·mol−1 |
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Phenazone (INN andBAN; also known asphenazon,antipyrine (USAN),antipyrin,[1] oranalgesine) is ananalgesic (pain reducing),antipyretic (fever reducing) andanti-inflammatory drug. While it predates the term, it is often classified as anonsteroidal anti-inflammatory drug (NSAID). Phenazone was one of the earliest synthetic medications — when it was patented in 1883, the only synthetic medical chemicals on the market werechloral hydrate, asedative (as well as at least one derivative of that chemical),trimethylamine, andiodol (tetraiodopyrrol), an early antiseptic.[2] One of the earliest widely used analgesics and antipyretics, phenazone was gradually replaced in common use by other medications includingphenacetin (itself later withdrawn because of safety concerns),aspirin,paracetamol and modern NSAIDs such asibuprofen. However, it is still available in several countries either as anover-the-counter or prescribed drug.
Ludwig Knorr was the first to synthesize phenazone, then called antipyrine, in the early 1880s. Sources disagree on the exact year of discovery, but Knorr patented the chemical in 1883.[3][4][5]: 26–27 Phenazone has an elimination half life of about 12 hours.[6]
Phenazone is synthesized[7] by condensation ofphenylhydrazine andethyl acetoacetate under basic conditions and methylation of the resulting intermediate compound 1-phenyl-3-methylpyrazolone[8] withdimethyl sulfate ormethyl iodide. Itcrystallizes in needles which melt at 156 °C (313 °F).Potassium permanganateoxidizes it to pyridazine tetracarboxylic acid.
Possible adverse effects include:[citation needed]
Phenazone is often used in testing the effects of other drugs or diseases on drug-metabolizing enzymes in the liver.[9]
